Semester Project 3: Security of Power Supply

SECURITY OF POWER SUPPLY
16. december 2015
Maibrit Vester Hansen Josephine Kamper Bang
Julie Birkedal Svendsen Jesper Arbirk Larsen
Søren Andreas Aagaard Christian Nissen Ahrenkilde
3. Semester-Project
Group: 4
Field of study: Energy Technology
University of Southern Denmark

University of Southern Denmark
Faculty of Engineering
Campusvej 55
5230 Odense M
http://www.sdu.dk
Titel:
Security of power supply
Projekt:
3rd Semester projekt
Projektperiode:
September 2015 - December 2015
Project group:
4
Participants:
Maibrit Vester Hansen
Josephine Kamper Bang
Julie Birkedal Svendsen
Jesper Arbirk Larsen
Søren Andreas Aagaard
Christian Nissen Ahrenkilde
Supervisor:
Alireza Kouchaki
Copy: 1
Pages: 75
Appendix: 25
Finshed 16-12-2015
Synopsis:
The project is about the security of
power supply, both current and in the
future. Renewable energys part, of the
total electricity production will continue
to grow in the following years, this will be
illuminated and analyzed.
The applicable legislation will be provided
and explained to help grasping the legal
aspect of the security of power supply.
The economical optimum power supply
will be calculated, to help evaluate if it
is proﬁtable to uphold Denmarks high
security of power supply.
To provide a more practical view, a
model of the powergrid has come together,
analysing how the grid react to the strain
caused by errors, to help fathom by which
criteria the grid is constructed.
The content of the rapport is freely accessibly, but publication (with sources acknowledged) is only allowed with
permission from the authors.

Preface
We would like to thank our supervisor Alireza Kouchaki for being helpful throughout the
project. We would also like to thank the employees of Energinet.dk, especially Chadi Ibrahim
Dalal and Kim Boe Jensen. Lastly we would like to thank all of our lecturers on the third
semester for guidance in the project.
Reading guide
The following project consist of diﬀerent chapters and section. Before each chapter or section, a
small introduction to the next section is written in italic text. Also after every section a partial
conclusion which is also written in italic text. Any source needed in the project is referenced to
in the project by using square brackets with a number inside.
If reading the project as a PDF: The references to the sources is a hyperlink which can be
used to jump to the bibliography in the back of the project. In the bibliography in the back the
internet sources are hyperlinks. Also all references made in the project to other sections,
chapters, ﬁgures or tables are hyperlinks.
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Abstract
1
This project will investigate the security of power supply both for now and the future. First,
the security of power supply will be explained. Hereafter the legislation that concerns the
security of power supply will be investigated, hereunder also what effect the legislation has on
the electricity grid. The next section will contain a calculation of the optimum security of
power supply, to find out whether it is too high. The calculated optimum security of power
supply is expected to be at the same level in the future as it is now. Next, the electricity grid
will be studied. This part will contain both what interconnections there are and what effect
these have on the grid, plus errors in the grid and handling of these. In order to look further
into the errors in the grid, a model of Funen is made. The model will contain four scenarios the
last three containing a type of error. A reason for errors could be an unstable load plan.
Therefore the load plan for 2014 will be analyzed. It will be made for both production and
consumption. Furthermore, the fluctuation in production and consumption is compared to see
the gap between these. Lastly, the project will contain a future aspect. This will contain the
energy scenarios, a possible future load plan, the future power grid, and tools for keeping the
security of power supply high.
The project concludes: The load plan, more specific the production, for the future will change.
However, the project finds that the optimum security of power supply is close to what it
currently is. Therefore will the security of power supply remain about the same in the future as
it is now because it is needed and because it can be done by the different methods stated in the
project. Such as interconnections, flexible consumption and capacity mechanisms.
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Contents
1 Abstract 4
2 Introduction 7
2.1 Specific tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3 Understanding the Security of Power Supply 9
3.1 Informative description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2 Legislation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2.1 Power production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2.2 Transmission system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.2.3 Fuel storage in case of emergencies . . . . . . . . . . . . . . . . . . . . . . 11
3.3 Optimum Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.3.1 Economical Power supply in general . . . . . . . . . . . . . . . . . . . . . 12
4 The Electricity Grid 16
4.1 Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.1.1 Power Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.1.2 Transmission System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.1.3 Distribution System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.2 Interconnections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.2.1 Interconnections in Denmark . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.2.2 Benefits - Great Belt Power Link . . . . . . . . . . . . . . . . . . . . . . . 19
4.2.3 The Technology Behind the Cable . . . . . . . . . . . . . . . . . . . . . . 19
4.2.4 Power Spot Price . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.3 Errors in the Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.3.1 Types of Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.3.2 Handling of Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.3.3 Preventing errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.3.4 Historical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.4 Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.4.1 Results – Load flow simulations . . . . . . . . . . . . . . . . . . . . . . . . 26
4.4.2 Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
5 Load plan 29
5.1 Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
5.2 Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
5.3 Production and Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.4 Fluctuations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
6 The energy system in the future 36
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Group 4 Energy Technology SDU
6.1 Energy in the future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
6.1.1 Energy scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
6.1.2 Wind-scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
6.1.3 Biomass-scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
6.1.4 Hydrogen-scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
6.1.5 Possible future load plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
6.2 Tools for securing the security of power supply . . . . . . . . . . . . . . . . . . . 39
6.2.1 The grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
6.2.2 Capacity Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
6.2.3 Flexible consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
6.3 Optimum power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
7 Discussion 46
8 Conclusion 47
9 Appendix list 49
9.1 Symbol explanation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
9.2 Abbreviation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
9.3 AC or DC lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
9.3.1 When are they used . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
9.3.2 Self-induction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
9.4 Simulering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
9.4.1 Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
9.4.2 Loadflow - Scenario 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
9.5 Surplus production calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
9.6 Project Formulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
9.6.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
9.6.2 The Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
9.6.3 Specific tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
9.6.4 The relevance of the project . . . . . . . . . . . . . . . . . . . . . . . . . . 64
9.6.5 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
9.7 Group process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
9.7.1 Work flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
9.7.2 Supervisor meetings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
9.7.3 Six phase model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
9.7.4 Belbin profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
9.7.5 Time table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
9.8 Implementation of the semester courses . . . . . . . . . . . . . . . . . . . . . . . 68
9.9 Optimum power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Bibliography 73
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Introduction
2
The project came to be by the hypothesis: If We do not act, the security of power supply will
decrease, because of the increasing renewable energies that have a more fluctuating power
production.
This hypothesis can be stated from the fact that there is an aim to increase the power
production from renewable energies, wind turbines in particular. By looking at the power
production from the current wind turbines in Denmark, a conclusion can be made; if the wind
turbines right now produce a fluctuating power production, the fluctuations will be even
greater with the increased amount of wind turbines in the future. This fluctuation will make it
harder for the Danish power grid to maintain the high security of power supply there is now.
The security of power supply will be harder to maintain because the supply and demand of
electricity will not correspond, and therefore either excess electricity or a lack of electricity will
occur at most times of the day. Both excess and lack of electricity can cause errors in the
Danish electricity system in terms of e.g. blackouts.
The current study is of interest, because the security of power supply in Denmark is one of the
highest in the world. Prognoses conclude that the security of power supply will decrease in the
future, as a reaction to the fluctuating power production caused by renewable energy. The
security of power supply is important, since a lot of our society depends on power at all hours
of the day. As a private consumer, the security of power supply is important but not essential
e.g., hospitals and banks need to know that there will be a power source at all times.
In this project, the Danish power grid and the security of power supply, will be studied and
analyzed. First, the legislation that the Danish government have about security of power
supply will be looked into. After this, the optimum power supply will be calculated. In the
next section an analysis of some of the interconnections in Denmark, in particular the Great
Belt Power Link. In the next section, errors in the grid and how it reacts are investigated, e.g.
a broken wire or the shutdown of a power plant will be simulated. The Danish load plan will be
made in form of graphs. This will include both the production and consumption. Lastly, the
electricity grid in the future will be studied.
2.1 Specific tasks
1. Illuminate the Legislation concerning security of power supply in Denmark and find out
what effect, it has on the Danish electricity system.
2. Investigate how errors in the grid are handled.
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3. Research interconnections including the Great Belt Power Link and how it aﬀected the
Danish power grid.
4. Analyze the load plan and the ﬂuctuations in the grid for the Danish electricity system.
5. Explore and calculate the optimum security of power supply in Denmark, seen from an
economical view.
6. Make a simulation of a circuit system, where an error happens in the grid
7. Make an analysis of the future energy system.
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Understanding the Security
of Power Supply
3
3.1 Informative description
For the modern society it is important to know that power will be avaliable at all times. It is
not only the households that need the power, but also companies, most importantly banks and
hospitals need power at all the time. For hospitals, banks and other power-sensitive companies
a uninterruptible power supply (UPS) system exists. This is further discussed in section 4.3.2.
The Danish security of power supply was 99.996% in 2014. This is equivalent to an average of
40 minutes without electricity per consumer per year. This is 10 minutes less than
Energinet.dk’s goal of 50 minutes per consumer [1]. On a ten-year average, the Danish security
of power supply is one of the three best in Europe together with the Netherlands and Germany.
Denmark is therefore used to having electricity at most times. A reason for it is that the
electricity grid provides electricity even if an error or two occurs. Errors are further looked into
in section 4.3. Another way to always provide electricity is via capacity mechanisms. These
mecanicims insure avalible capacity when needed and is further described in section 6.2.2. In
the future it can however be a problem to keep the security of power supply high, due to more
fluctuating power production, mainly from wind turbines. The current loadplan can be seen in
section 5 and a possible future loadplan in section 6.1.5. Regardless of the future Energinet.dk
has to make sure the Danish security of power supply stays high.
The security of power supply is a description of the quality for the electricity. There are
different variables in the description. It is important that every aspect is within the tolerance,
otherwise the grid will not function properly. Energinet.dk is responsible for securing the
supply of electricity. The different variables are that [2]:
1. The frequency has to be 50 Hertz +/- 0.1
2. The voltage has to be 230 Volt +10%/-6%
3. The electricity price has to be at a payable level
4. The different security requirements must be respected
5. The grid must be built and operated with respect to the environment
3.2 Legislation
In the following section the legislation associated with security of power supply will be
illuminated together with the effect it has on the Danish electricity system.
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As mentioned earlier in section 3.1 the security of power supply in Denmark is one of the
highest in the world. This is however no coincidence. The Danish government is very keen on
having a high security of power supply so the high standard of living and industry can be
maintained. The Danish legislation and delegated legislation therefore makes sure that the
security of power supply meet the requirements from the Danish society. One of the more
important pieces of legislation is the Danish electricity supply Act(Bekendtgørelse af lov om
elforsyning[3]), where one of the main objectives stated in section 1(1) is to secure the
electricity supply in terms of i.a. security of power supply. The act also states in section 27a(1)
that the responsibility for upholding the security of power supply lies with Energinet.dk. This
means that they have to maintain the technical quality and balance in the electricity system,
and make sure that a suﬃcient power production capacity is available. To uphold the security
of power supply Energinet.dk has the right, stated in the Danish electricity supply Act section
27a(2), to collect information from the users of the electricity system. The legislation
concerning Energinet.dk is elaborated in the Danish Act on Energinet.dk(Bekendtgørelse af lov
om Energinet.dk[4]).
3.2.1 Power production
To make sure that the security of power supply is being upheld, rules about power production
are made in the Danish electricity supply act. Any power plant with a capacity larger than 25
MW has to get a license to produce power from the minister of climate, energy and
building(klima-, energi- og bygningsministeren). This is stated in the Danish act on electricity
supply section 10. In this license there can be some conditions that has to be met including
that the power plant is obligated to change the production if Energinet.dk ﬁnds it necessary to
maintain e.g. the security of power supply. Furthermore it is stated in section 27b(1) that any
power plant with a capacity larger than 25 MW has to get an authorization by Energinet.dk to
be allowed to shut down. Also if the power plant does have an authorization, but Energinet.dk
estimates that the power plant has to run to maintain the security of power supply,
Energinet.dk can demand that the power plant keeps running. Of course being paid to do so by
Energinet.dk. This can be categorised as an capacity mechanism too, which is explained
further in section 6.2.2
If a power plant does not plan to shut down, it has to, according to the Danish electricity
supply act section 27b(2), inform its projected power production to Energinet.dk, up to four
weeks in advance, if it is needed to maintain the security of power supply. This information is
needed for Energinet.dk to see if the expected power production is enough for the expected
power load. Energinet.dk then has to approve the plan for expected power production as stated
in section 27c(3). Even though the plans have been approved, Energinet.dk can according to
section 27c(4) demand that a power plant changes its production to uphold the security of
power supply.
In section 27b(3) it is stated that Energinet.dk is given the right to demand that any power
plant has to be held ready for operation, even though they informed Energinet.dk that they
were not going to produce power that day. Energinet.dk has the right to do so if they estimate
that the power plants that informed Energinet.dk that they were going to produce cannot
uphold the security of power supply. The additional costs for the power plant, by being ready
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for operation, is paid by Energinet.dk. This can be categorised as an capacity mechanism too,
which is explained further in section6.2.2
3.2.2 Transmission system
In the Danish Act on Energinet.dk section 4(1) it states that Energinet.dk can make new
transmission lines or make significant changes in the existing system, if there is a need to do so,
to maintain or improve e.g. the security of power supply. In section 4(3) it is stated that the
minister of climate, energy and building can require that the changes Energinet.dk plans, has
to be approved by the minister of climate, energy and building. In section 5(6) it is also stated
that the minister of climate, energy and building, can impose Energinet.dk to expand the
offshore transmission lines to maintain the security of power supply at smaller islands. If a
company not owned by Energinet.dk wishes to expand or make significant changes in the
transmission lines for voltages higher than 100 kV, an authorization is needed from the minister
of climate, energy and building. According to the Danish electricity supply act section 21(1),
the act also states that the company has to be able to prove that the changes in the lines are
needed to improve i.a. the security of power supply.
3.2.3 Fuel storage in case of emergencies
The previous section illuminated how Energinet.dk can control the power production so the
security of power supply can be upheld. This is necessary, but does not matter if there are no
fuel to produce power. Therefore, fuel storage exists in case of emergencies, where it is
impossible to obtain fuel from the rest of the world. This fuel storage is explained in the
executive order on fuel storage in case of emergencies in pursuance the Danish electricity supply
Act(Bekendtgørelse om lagerberedskab for brændstoffer i medfør af lov om elforsyning[5]). The
executive order is as stated in section 1 meant to make requirements for the Danish fuel storage
in case of emergencies.The Danish Transmission system operator (TSO) has to investigate how
the Danish power supply will handle a problem in the power supply. In these investigations it
is also considered if any plant can operate on different fuels, in case it is only one of the fuel
supplies that is cut. This is stated in section 2(2). With all these investigations taken into
account the Danish power consumers has to be able to get power for three months even if the
fuel supply is cut off. This is stated in section 3. This means that there has to be fuel storages
in Denmark, or transmission lines from other countries, to deliver power to the Danish
consumers in three months. These three months are based on an average month and are
therefore not certain for the exact case, but development in the power consumption has to be
taken into account when calculating the storage needs. If the Danish TSO finds the existing
storages to be lacking capacity to maintain the 3 month power production, the Danish TSO
has to inform the Danish Energy Agency(Energistyrelsen) as stated in section 3(2).
So as seen in the former section the Danish government is working towards having a steady and
reliable power source for the Danish consumers. Not only do they try to prevent any faults in
the electric grid by managing the power production, they also have fuel storages in case the
country cannot get fuel to produce power.
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3.3 Optimum Power Supply
As mentioned in section 3.1 the security of power supply is at 99.996% and has been for some
time now, and in section 3.2 it is shown that the Danish government also has an interest
upholding the high security of power supply. But is it really profitable for the consumers to
have this extensive security? In the following section, the economical optimum power supply
will be explained and calculated, for further information look in section 9.9.
3.3.1 Economical Power supply in general
From an economical point of view, it is reasonable to conclude the optimal security of power
supply is at equilibrium when, the long run total cost (LRTC) of heighten the security is equal
to the value of lost load (VoLL) caused by the supply failure over time.
The LRTC of heighten the security of power supply has an actual price, which can be
determined through the sum of: Long run marginal cost (LRMC) of turbines, the grids and
transformer stations times the power consumption.
The VoLL can on the otherhand be difficult to calculate. The cost of a large company having a
power outage can be calculated as the salery of the employee not being able to work, any
irrecoverable work and overdue deadlines. But the cost can also be direct none monetary such
as; panic, loss of reputation and danger of being victim of a criminal act. These loss’ are much
harder to price, and can only be optained through a survey.
The same goes for a household, where the direct monetary cost of a power outage of one hour
is somewhat near 0 DKK, but the direct none monetary cost such as not being able to cook,
rising tempature in the refrigiator and not being able to use electric light, all provides some
value for the household.
Data
Through this section DAMVAD’s report on expenses caused by not planned disruptions of the
power grid, will be used as data source[6]. The value will vary a lot for the different kind of
consumers e.g., a large factory stand to loose a lot more, compared to a household. Thus the
consumers has been divided into 4 different categories: "Households, Agriculture, Industry and
Service". An optimum security of power supply will be calculated for each group
Duration Agriculture Industry Service Households
1 Minute 0.0 7.8 0.0 0.0
1 Hour 9.5 111.0 116.6 0.0
4 Hours 21.6 135.9 275.8 29.3
12 Hours 22.3 94.4 255.4 49.9
Table 3.1. Normalized cost [DKK/kWh] distributed over time
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0.1 1 4 12
0
50
100
150
200
250
300
Hours
DKK/MWh
Household
Agriculture
Service
Industry
Figure 3.1. Normalized cost [DKK/kWh] as a function af time
Method
This subsection will take a deeper look into the methods used to calculate the optimum power
supply and explain some of the terms used.
Value of Lost Load
The VoLL is the estimated amount customers are willing to pay, to avoid disruptions in their
power supply. In this report VoLL is decided to be equal to the amount they stand to loose as
a result of being disconnected from the grid.
The data from DAMVAD has been used, to determine 5 trendlines for each consumer group,
the first 4 to copy the original data and the 5th starting at the 12th hour and rising with the
average incline.
Long Run Total Cost
To determine the LRTC of operating the power grid, the powers "road" from production to
consumption needs to be broken down to smaller parts.
First the powerplant, in this analysis a gas turbines long run marginal cost (LRMC) is
calculated with an availability of 94%. Adding a second powerplant to the grid heightens the
availability to 99.64%. Adding enough energy sources, the availaility is going to be endlessly
close to 100%. Ploting the LRMC as a function to the hours the plant is active. From these
coordinates a trendline can be estimated, gasturbines LRMC as a function of "price" and "lack
of availaility".
LRMC(x) =
40
x
(3.1)
The cost of subscripting to the power company, taxes etc. has been determined from
Vordingborgs power company. The cost of transmission and distribution grid has been
determined to be equal to the grid and system tariff. This has been done due to the fact that
the tariffs function is to cover the expenses of transission and distribution. DAMVAD’s report
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has estimated the average power consumption for each user, this data will be used further in
this analysis.
The total cost of producing and distributing to the end user as a function of time is calculated
as follows:
LRTC(x) = (LRMC(x) + Subscription + Tariff) · AveragePower · x (3.2)
Security of power supply
Now, in possession of both an expression of the LRTC and the VoLL, their equlibrium is
straight forward to ﬁnd. Decide that the LRTC is equal to the VoLL and then solve for x
LRTC(x) = V oLL(x), Solve(x) (3.3)
The following graph is from the calculation of the optimum power supply of a household.
Figure 3.2. Equilibrium of a household
The total security of power supply is then calculated from the total amount of hours in a year
substracted by the "x" value of the eqlibrium.
SecurityOfPowerSupply[%] =
8760 − x
8760
· 100 (3.4)
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Analysis
This model is a simplification, and does not take into account that the VoLL can be
manipulated. The VoLL could be lowered by different messures, one of which could be by
alerting the end user in advance. By doing that, the optimum power supply would decrease as
well. The time of reference is a great factor too, households time of reference in winter between
4-8PM, for the remaining it is winter between 8AM-4PM. By altering the season or the hour,
the VoLL would change too. The reason for choosing these specific time references is an
evaluation of when the power was needed the most, in prospect of getting a worst case senario.
Households Agriculture Service Industry
Actual security of power supply 99.996 99.996 99.996 99.996
Optimum security of power supply 99.96 99.56 99.99 99.64
Difference 0.036 0.436 0.006 0.356
Table 3.2. The difference between the actual and optimum power supply in %
In Denmark the security of power supply is exceptionally high, and it is profitable to have the
security this high. The social cost of being without power is simply too high to withstand a large
span of time being without electricity.
The analysis shows on the other hand that, the households does not suffer any losses during the
first hour of the disruption. It would therefore be profitable to make contracts with households,
which allows the power company, to disrupt the power from them for a shorter period of time,
when in shortage of electricity capacity.
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The Electricity Grid
4
4.1 Structure
The most important thing that can cause the security of power supply to drop is errors in the
grid, but to be able to understand the errors that can happen in the electric grid, an
informative description of the electricty grid is needed. The following section will illuminate the
structure of the electric grid in Denmark.
The structure in the Danish power system is made of 3 elements: power production,
transmission and distribution. In the following subsections the 3 elements will be illuminated.
Figure 4.1. The Danish power grid [7]
4.1.1 Power Production
In Denmark, the electricity is produced by several diﬀerent types of power plants. Largest are
the 16 central power plants. They run on coal, natural gas, oil and biomass. Next are the 1000
decentral power plants. These can both be CHP (Combined heat and power) plants, industrial
plants, and local plants. These usually run on natural gas, waste, biogas and biomass.
Denmark is not known for having a lot of photovoltaic, nevertheless there are 92,000 solar
power plants in Denmark. And last, but certainly not least, Denmark has 5200 wind turbines
consisting of both onshore and oﬀshore.
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4.1.2 Transmission System
The transmission lines are responsible for transporting the power from the power plants around
the country, to where it is needed. The central power plants and offshore wind farms are
connected directly to the transmission lines. In Denmark the transmission lines are owned by
Energinet.dk, that is an independent company owned by the Danish state[8].
The voltage on the transmission line vary from 400 kV to 132 kV[9]. In Denmark the voltages
vary depending on where in the country the lines are placed. The highest voltage in Denmark
is 400 kV, but in Jutland and on Funen the next voltage level is 150 kV and at Zealand it is 132
kV. The explanation for this difference is the interconnections that Denmark has with its
surrounding countries. Jutland and Funen is connected to the German transmission lines,
which have a voltage of 150 kV, and Zealand is connected to the Swedish transmission lines
which run with a voltage of 132 kV[9].
4.1.3 Distribution System
Placed between the transmission lines and the consumers are the distribution lines. Most of the
power production in Denmark is connected to the distribution lines since the decentral power
plants, the solar plants and onshore wind turbines are connected to the distribution lines. The
distribution lines in Denmark vary in voltage from 60 kV to 230 V. Most consumers get their
power at a voltage of 230 V and 400 V[10], but some companies get their power from the 10 kV
distribution lines.
The distribution lines are owned by local distribution companies like “Energi Fyn” at Funen
and “DONG” at Zealand[11].
The previous section tells that the electric grid in Denmark is made from 3 different elements.
The power production, the transmission system and the distribution system. The transmission
grid is owned by Energinet.dk, and the distribution system is owned by local distribution
companies.
4.2 Interconnections
In the following section interconnections will be explained and it will be described how the
Great Belt Power Link affected the Danish power grid.
4.2.1 Interconnections in Denmark
Denmark is electrically connected to the surrounding countries with cables, called
interconnections. They are owned and operated by Energinet.dk and the TSO from the
surrounding countries. These connections make it possible to trade the surplus electricity, a
country might have, to other countries. An example is, when Denmark is producing more
energy from wind power than the total energy consumption, it can be transfered through
interconnections to surrounding countries in need. The connections are an important part of
the daily operation too, where the balance between consumption and production needs to be
maintained. The balance can be even more difficult to maintain when there are errors in the
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grid, therefore the interconnections are used to reestablish the balance between consumption
and production.
If the countries do not have the opportunity to work together through the interconnections,
every country has to have larger reserves to insure the security of power supply. Thus
interconnections are benefitial for all parties involved.
Denmarks Location
Denmarks location between a power system based on water energy in Norway and Sweden and
a power system based on power plants in central Europe means there is a large trade value to
trade electricity through Denmark. This has historically ensured an economically positive
development of the Danish interconnections. In figure 4.2 Denmarks interconnections can be
seen. It shows that Denmark has connections to Norway, Sweden and Germany, furthermore a
connection to the Netherlands and the wind farm Kriegers Flak that are under construction. In
addition, a connection to the United Kingdom is being planned, and a connection from Kriegers
Flak to Germany is also being planned. The new interconnections will be analyzed further in
section 6.2.1. The year next to the lines indicate the expected first full year of operation.
Figure 4.2. Interconnections, Denmark [12]
The Danish power system is seperated into two parts, DK1 and DK2. DK2 is a part of the
Nordic power system, and DK1 is a part of the continental European power system. While
these two parts are not in phase, they have been connected by a DC connection over the Great
Belt, which makes the transmission between DK1 and DK2 possible.
Before the 26th of August 2010 Denmark has, electrically, been divided into two parts; on one
side Zealand and the islands and on the other Jutland and Funen. Zealand is closely attached
to the other Nordic power system with AC connections to Sweden, while Jutland has strong
AC connections to Germany. One of the main reasons that the Great Belt connection became
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economically viable, was the decision to focus so much on renewable energy. The decision to
build the Great Belt Power Link was taken in 2005.
4.2.2 Benefits - Great Belt Power Link
The Great Belt Power Link has some benefits, one of which is that it is now possible to
distribute the electricity from wind power, which mainly is produced in DK1. So when there
are produced more than needed in DK1 it can be transported to DK2 instead of exported to
other countries. As it is known there has to be balance between consumption and production in
the power system because it is not an opportunity to store the electricity 6.1.5. Therefore, it is
necessary to have reserves if suddenly an error occur within the grid, in this case it means
capacity mechanism 6.2.2. With the Great Belt Power Link DK1 and DK2 can use each others
reserves and therefore it is not necessary to have as large a reserve, as before Denmark was
connected. Furthermore the need to start up the least effective power plants have become
smaller after transmission across the Great Belt has become reality. Due to this, Denmark
produces electricity at power plants with high efficiency and thereby reduces the cost of
producing power. Another benefit from the Great Belt Power Link is that it equalizes the price
of electricity in DK1 and DK2. Thereby the price in the future will be more similar in both
parts of the country.
4.2.3 The Technology Behind the Cable
The power system in DK2 and DK1 are not synchronised, therefore the Great Belt Power Link
was built on DC. The reasons why it is DC are described in the appendix section 9.3.
The Great Belt Power Link consists of two converter stations, one at Funen and the other at
Zealand. Here the DC is converted to AC and vice versa. In the same context these stations
connects the Great Belt Power Link to the existing power system. The station in Fraugde,
Funen is built in combination an existing transformer, and the station in Herslev, Zealand is
newly built.
The connection consists of two cables, one at sea and one at land. The sea cable system consist
of a 400 kV DC power cable, a 20 kV return cable and fibre optic cables. The sea cable is from
Risinge Hoved at Funen to Mullerup at west Zealand and the cable is 32 kilometers. The land
cable system does also consists of a 400 kV DC power cable, a 20 kV return cable and fibre
optic cables. At Funen the cable is 16 kilometers and it is 10 kilometers at Zealand.
4.2.4 Power Spot Price
One of the benefits about the Great Belt Power Link is, as mentioned earlier, that the
electricity price in the future is more similar in both parts of the country. This can be seen in
figure 4.3, where the power spot price is plotted for both DK1 and DK2 Denmark, just before
and after the Great Belt Power Link was built. The figure also shows some data from recent
time.
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0 1 2 3 4 5 6 7 8 9 101112131415161718192021222324
0
50
100
150
200
250
300
350
400
450
Hours
DKK/MWh
West 03.05.10
East 03.05.10
West 03.10.10
East 03.10.10
West 03.10.15
East 03.10.15
Figure 4.3. Electricity spot price [DKK/MWh] as a function af time [13]
Figure 4.3 shows, that the power spot price is lower after the Great Belt Power Link was built,
than before. It should be noticed thou, that the lower price already can be seen after few
months. But the figure also shows, that the price from 2010 to 2015 have become more similar
in both parts of the country. Furthermore it can be seen that the power spot price has become
cheaper over the years from the 26th of august 2010, where the Great Belt Power Link was
built, until 2015.
Common electricity price
In 90% of the time Denmark has the same electricity price as at least one of the surrounding
countries, which electricity market is significantly larger than the Danish and thereby they are
generally the price setters. Figure 4.4 shows the period from 2012 through 2014, where the
data is given for Denmark as one part because the time with common price are largely the
same in both DK2 and DK1.
Figure 4.4. Time with common price in the period 2012-2014. [12]
In figure 4.4 it can be seen that in 50% of the time Denmark has a common price with the
Nordic and 20% of the time is common with respectively Germany and all the countries in
Europe. Finally 10% of the time Denmark has its own price.
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The former section shows that interconnections make the electric grid more steady since they
can be used to balance the grid in terms of effect. The interconnections are also an economical
benefit, since they make it possible to sell power if there is a surplus in the production.
Denmark is placed between the Nordic system and the central European systems which makes
sure, that there is a large trade value to trade electricity through Denmark. In Denmark the
Great Belt Power Link connects the two areas DK1 and DK2 Denmark. The benefits of this is
that the power can be transported to every part of the country, and to every interconnection to
the surrounding countries. This also causes the price to be more similar in the two areas DK1
and DK2 Denmark. Furthermore, the electricity spot price is lower after the construction of the
Great Belt Power Link.
4.3 Errors in the Grid
The Danish power grid is not perfect, sometimes errors happen. This section deals with
different types of errors, what to do when the power grid fails, and what is done to prevent the
errors.
4.3.1 Types of Errors
Not all loss of electricity will be caused by errors, some will also be from maintenance where a
part of Denmark may lose electricity for a period. This will, however, always be planned so the
consumers can plan how to handle it. However, it is mostly not, what happens when there is a
power outage. The main reason causing power outages are errors. There are different types of
errors. There are small errors such as voltage drops. This is defined as when the voltage drops
more than 10%. However, the main errors happen in or on the cables. Errors often happen due
to the weather which can cause storms and then trees, or other objects, to fall onto the air
cables. During the past year’s storms, 50-200 errors has happened during each storm[14].
Furthermore, in old cables more accidents happen[15]. There is a way to prevent these types of
errors though. More about that can be seen in section 4.3.3.
4.3.2 Handling of Errors
If only one cable is cut, the power grid is constructed to transfer the electricity another way,
through another cable[16]. This will also be the solution in case of planned maintenance, if the
capacity is sufficient.
Some companies cannot handle being without electricity for even a second. This could lead to
data losses in banks and even people dying on operation tables in hospitals. For these
companies a system UPS exists. These will normally only work for 10-60 minutes, this is
however enough time to get an emergency generator going. UPS is not a demand for
companies, but in 2008, 295 companies in Denmark had chosen to have one; these have a total
of 103 MW [17]. UPS can also keep providing the same voltage if the voltage should drop in
the electricity grid. The UPS however, is not used by all consumeres.
For the rest of the consumers another handling must take place. If an extensive power outage
happens, a certain procedure is put into motion in order to restore the power grid to full
capacity as quickly as possible. There are three steps involved with restoring the power grid.
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1. Prepare the power grid. Energinet.dk tells the grid companies to disconnect the
consumers from the transmission grid, which has to be manually disconnected. This
enables the transmission grid to power up slowly.
2. To get power in the transmission grid there are three ways of restoring the power:
• By the interconnections.
• By Denmark’s own central power plants: (this can only happen if they are in idle
mode, because they are unable to perform a black start).
• By special emergency power plants: (these cannot produce electricity for the entire
power grid, but can produce enough to start the central power plants).
3. At last, the consumers are connected to the power grid; this happens one area at the time.
In 2003, there was an extensive power outage[18], which is an example of why it is important to
prepare the power grid in case of a blackout. In 2003, the power outage was in eastern
Denmark and southern Sweden. The reason behind the outage was a mechanical error in
Horred, Sweeden, connection station. Because of it, four 400 kV cables did not work and the
main power production from southern Sweden got disconnected. Shortly after the connection
was cut to central Sweden, because the relay had measured a short circuit. In Denmark, there
was no way to measure the short circuit in Sweden, so the power plants kept producing even
though they could not support all of southern Sweden and eastern Denmark. The power
dropped to zero in a matter of seconds and the power grid collapsed. This damaged multiple
power plants and the biggest power plant (Asnæsværket blok 5) in eastern Denmark was
seriously damaged. The power had to be restored from scratch so the procedure was followed
and since southern Sweden was out as well, the emergency power plant had to be used, but it
did not work. Then there was only one thing to do, wait for Sweden to regain power and then
get the power plants going again. The power outage happened in Denmark, because it was not
possible to detect the error in Sweden, since there was no remote sensing. Immediately here
after a remote sensor was set up so that Denmark could see errors in the countries with whom
they are interconnected. There are other ways of preventing errors too.
4.3.3 Preventing errors
To prevent errors, the most important thing is maintenance. This will make sure that if a lot of
errors has happened on a certain cable or component that this will be replaced. As mentioned
earlier overhead wires caused a substantial amount of errors, this can be prevented by burring
the cables [19]. However not all errors can be prevented.
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4.3.4 Historical
Figure 4.5. Power outages historically
Figure 4.5 shows the historic development of how many minutes an average consumer will
experience interruption of electricity pr. year. It can be seen that the faults in the grid has
been decreasing overall. Especially the interruptions on the 25-400 kV grid, and the force
majeure on the 1-24 kV grid is lower in the last five years than in the last twenty. The reason
for this could be the additional burying of cables that was mentioned in section 4.3.3. This
makes the power grid stronger against storms and other faults in the 1-24 kV grid. In the figure
the historic failure in 2003 is causing the “Interruptions (25-400 kV)” to be bigger than in any
other year. After 2005 there is an increase of “Scheduled (1-24 kV)” interruptions, this could be
caused by the cables being laid into the ground.
This section showed that there were different types of errors, such as voltage drops and errors
on the cables. These could be dealt with in different ways. For power-sensitive companies, UPS
could be used for power outages. In order to get the electricity grid working again a procedure
had to be followed. Also, burying cables was a great way to prevent errors.
4.4 Model
To support the fact that the Danish electricity grid is resistant and well developed, a model for
simulations has been made. The model is a simplified version of the transmission grid on
Funen, covering 400kV and 150kV.
The purpose of the model is to make load flow simulations in case of errors in the grid. The
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reason to why the transmission grid is chosen for the model instead of the distribution grid is
that a breakdown in this grid will be the worst case scenario. The distribution grid is far more
widespread and therefore it is easier to withstand and maintain the stability of the grid in the
case of failure. Hence, a breakdown somewhere in the distribution grid will affect fewer
consumers.
During configuration of the model, different assumptions have been made in order to simplify.
It is assumed that:
• The Great Belt Power Link exports its full capacity of 600MW from DK2 to DK1 (worst
case scenario).
• The grid is optimal in terms of effect. This leads to reactive effect being neglected when
possible.
• There are no synchronous compensators or shunt reactors.
• Fynsværket Block 3 is out of service and will not contribute in the simulations.
• Fynsværket Block 7 is producing electricity for the 400kV grid.
• Fynsværket Block 7 is operating at full capacity (406MW).
• Interconnections from Jutland will be self-regulating feeders.
Below, the model can be viewed in figure 4.6 and compared to the actual transmission grid in
figure 4.7.
Figure 4.6. Model of the transmission grid on Funen
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Figure 4.7. The transmission grid on Funen
For more in depth information regarding the construction of the model, please see appendix 9.4.
The load flow simulations are based on 4 different scenarios. The scenarios are selected on the
basis of situations which could be critical for the load flow on Funen and therefore be critical
for the security of power supply as well.
Scenario 1
The first scenario covers the daily operation without any failures or breakdowns and will be the
reference scenario in the overall analysis.
Scenario 2
In the second scenario, the 150kV overhead wire between Abildskov and Sønderborg suffers
from a breakdown. This could cause increased loads in some cables or wires in the transmission
grid or cause a lack of effect across south west Funen and hence affect the security of power
supply. Abildskov is particularly exposed if the interconnection to Sønderborg suffers a
breakdown. This is due to the great distance to the nearest source of effect (150kV or above),
being Fynsværket.
Scenario 3
In the case of scenario 3, the 400kV overhead wire from Landerupgård to Kingstrup suffers a
breakdown. This could be crucial to the transmission grid on Funen for the same reasons
mentioned in scenario 2, but on a higher level due to the higher effect capacity of the wire.
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Scenario 4
The last scenario, scenario 4, consists of a situation where Fynsværket is out of service, due to
either planned maintenance or a failure breakdown. This situation is very interesting due to
Fynsværket being the only large power plant on Funen. This could lead to a great lack of effect
and hence be of great danger to the overall security of power supply on Funen.
4.4.1 Results – Load flow simulations
Scenario 1 Scenario 2 Scenario 3 Scenario 4
Normal ABS - SØN KIN - LAG FVO
Name on line Load % Load % Load % Load %
ABS - 150kV - FVO 30.19 23.11 30.77 29.74
ABS - 150kV - SVB 10.04 1.25 11.75 11.4
ABS - 150kV - SØN 99.48 0 112.24 108.18
FGD - 150kV - FVO 23.8 30.82 23.83 18.59
FGD - 150kV - OSØ 18.39 22.03 18.4 15.07
FGD - 150kV - SVB 11.57 13.17 10.37 10.29
FGD - 400kV - KIN 9.5 10.82 2.94 20.65
FGD - 400kV - LAG 30.35 35.44 60.64 58.96
FVO - 150kV - GRP 12.49 9.59 13.34 15.84
FVO - 150kV - OSØ 9.74 12.81 9.94 9.04
FGD - 400kV - FVO 23.98 23.87 24.02 0
GRP - 150kV - KIN 29.83 33.68 22.28 34.61
KIN - 400kV - LAG 36.87 43.16 0 66.69
Busbar 100-110 100-111 99-110 99-110
Table 4.1. Scenarios
4.4.2 Analysis
Scenario 1
To see the loadflow of scenario 2 see appendix 9.4.2. When observing the 400kV grid, it is seen
that 3 out of 4 400kV overhead wires are loaded with 20-40% of their maximum capacity. The
reason to this is due to the high amount of effect transferred from the interconnections
(feeders). The last line, FGD – 400kV – KIN, is only loaded with about 10% of its maximal
capacity. This is due to some of the power transformed down to 150kV at Kingstrup, making
the 400kV overhead wire between Kingstrup and Fraugde less loaded.
Looking at the 150kV, it is seen that the general load% of the cables/wires are 10-20%, which
is very good. Two wires stand out from the rest, loaded at about 30%. The wire, GRP – 150kV
– KIN, is exposed to a greater load% caused by a larger amount of effect transferred to the
consumption load in Graderup. This is due to a shorter distance between Kingstrup and
Graderup, compared to the distance between Graderup and Fynsværket, hence this leads to
lower effect loss which always is preferred. The second wire, ABS – 150kV – FVO, is exposed to
a greater amount of load as well. The reason to this is the low max rated current of the wire
compared to the 150kV grid in general. Besides this, the small amount of effect needed in
Abildskov, to power the consumption load, is transferred through ABS – 150kV – FVO due to
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this route being the most effective coming from a central rallying point (FVO 2). The most
critical wire is the one between Abildskov and Sønderborg, called ABS – 150kV – SØN. This
wire is almost maxed out, 99.5%, in terms of possible power transferring, caused by a poor max
rated current together with the large amount of effect transferred from the interconnection
from Sønderborg to the consumption load in Abildskov. The actual wire is scheduled for
refurbishment, replacing the overhead wire with a brand new buried cable with a capacity of
925A. This will help decrease the load% of the cable in the future and is expected to be
commissioned in December 2016 .
Scenario 2
To see the loadflow of scenario 2 see appendix 9.4.3. If the interconnection between Abildskov
and Sønderborg suffers from a breakdown, it is observed that a part of the 400kV grid will be
effected. More specific, the two 400kV overhead wires from Landerupgård will be exposed to a
greater amount of effect, and hence a greater load%, in order to fill out the lost effect from
Sønderborg and stabilise the overall effect balance of the electricity grid.
When looking at the 150kV grid, it is seen that the overall load% is decreased compared to the
reference scenario. This could be due to all of the power coming from the 400kV grid and being
distributed more effectively to the cables and overhead wires with the highest capacity, yielding
a lower load%.
Scenario 3
To see the loadflow of scenario 3 see appendix 9.4.4. In this scenario, one of the 400kV
overhead wires suffers a breakdown, more specific the wire named KIN – 400kV – LAG. For the
grid to be stabilized in terms of effect, the lagging effect is drawn from the second
interconnection wire named FGD – 400kV – LAG. The reason to why the load% is doubled on
FGD – 400kV – LAG instead of transferring much more effect to the grid from Sønderborg, is
that the effect loss is less in the 400kV grid compared to the 150kV grid. The wire, FGD –
400kV – KIN, is experiencing less load% due to only having to supply effect to the consumption
load in Graderup instead of transferring effect from Kingstrup to Fraugde as in the previous
two scenarios.
The most interesting change in the 150kV grid is seen in the wire, ABS – 150kV – SØN. This
wire exceeds its capacity by 12% and this of course causes a problem in the grid. This problem
can be solved by lowering the effect transfer at the Great Belt Power Link. Solving this kind of
overload problems in the grid by changing the interconnections effect transferring is a
commonly used method.
Scenario 4
To see the loadflow of scenario 4 see appendix 9.4.5. If Fynsværket is unable to deliver power to
the grid, the 400kV interconnection from Landerupgård will operate as backup. This yields the
load% to double for both the wires, covering almost all of the lost 406MW capacity of
Fynsværket Block 7.
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The 150kV grid experiences the same load flow as in scenario 3, with the wire interconnecting
Abildskov and Sønderborg overloading with about 10%. This can be solved in the same
manner as in scenario 3.
The grid on Funen is strong enough to support itself with electricity in every scenario, but it
cannot deliver 600 MW over the Great Belt Power Link in simulation 3 and 4. The four
scenarios shows that the wire from Abildskov to Sønderborg is too weak and needs replacing.
Fortunately, this is scheduled to be finished in December 2016 with a cable with a max rated
current at 925 A, which solves the problems. The simulation is a very simplified version of the
actual grid. The actual loads are unknown but approximated assuming that they consume
equally much, which they do not in reality. There is also smaller local power plants, which is not
in the simulation; these will help securing the supply. The simulation does not consider reactive
effect, which is a problem since there will be loss of reactive power so the feeders need to deliver
the needed reactive effect to the grid so it functions normally. This gives an unrealistic problem
at the line between Sønderborg and Abildskov. In reality it is a lot less loaded.
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Load plan
5
As stated in section 4.3 some of the errors that can happen in the grid are caused by an
unstable load plan. In the following chapter an analysis will be made of the current load plan
of Denmark.
As earlier stated, the Danish security of power supply is 99.996% in 2015. This high percentage
of security of power supply is achieved by the Danish systems ability to handle errors and
interruptions. This is further explained in section 4.3. Furthermore, the high percentage is
achieved by the ability to deliver the electricity when the consumer needs it. This is done by
selling and buying electricity on NordPool and by up-and-down regulation of power plants to
ﬁt the Danish load plan. The load plan includes both the electricity produced and the
electricity consumed. The load plan can be looked at in diﬀerent ways; for one day and for a
year. In this section, these will be analyzed. All graphs in this section are plotted in the
program MATLAB [20] and made from a data collection for 2014 [13].
5.1 Production
Figure 5.1 shows the production of various kinds of electricity productions. (Yellow: Solar,
Green: Decentral, Blue: Central, Red: Wind, and Black is the total combined production)
Figure 5.1. Graph of Production
Because of the fact that there is 8760 hours in a year, this graph can only give an overall
understanding of the electricity production. Therefore, two weeks are taken out and further
analyzed. These weeks are the highest production week of winter and lowest of summer in
order to see the extremes. The high week is from 00AM Sunday 19th of January 2014 to and
including Saturday 25th of January 2014. The low week is from 00AM Sunday 27th of July
2014 to and including Saturday 2nd of August 2014.
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Figure 5.2. Graph of Production High week
Figure 5.3. Graph of Production Low week
The total production seen in figure 5.2 lies between 5000MWh
h and 7500MWh
h , whereas in figure
5.3, the production is not as high, but it still fluctuates as much; it lies between 1000MWh
h and
4000MWh
h . The main differences on the two weeks other than the high and low production are
the solar production, and the production of central and decentral production. The solar
production (yellow line) is higher in the low week (summer) than in the high week (winter). In
January 2014, there were only 17 hours of sun, whereas there in July/August were 277/188
hours of sun[21]. In the summer, the production goes up to 500 MWh, whereas it maximum
reaches 350 MWh, but mainly during the day 100-200 MWh, in the winter. Also the central
and decentral productions are different on the graphs. In Denmark, the central and decentral
production is from CHP plants. In the summer, the need for heat is not as high as in the
winter, and not as much electricity will be produced if it is not needed. The wind production
on the other hand cannot be regulated and as both graphs show, the red line (the wind
production) has a great effect on the total electricity production (This will be compared with
the production later on). First a look at the consumption on its own.
5.2 Consumption
Figure 5.4 shows the consumption: Blue: DK2, green: DK1 and red: total consumption.
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Figure 5.4. Graph of Netto Consumption
Like the graph seen i figure 5.1, this graph can only give an overall understanding of the
electricity consumption. Therefore, two weeks are taken out and further analyzed. In order to
compare the production and consumption the same weeks are chosen.
Figure 5.5. Graph of Netto Consumption High Week
Figure 5.6. Graph of Netto Consumption Low Week
The use of electricity varies throughout the day. The two figures 5.5 and 5.6 shows a constant
use of electricity throughout the entire day of at least 3000MWh
h in winter, and 2500MWh
h in
summer. By using a tool in MATLAB, the exact times can be shown. Looking at figure 5.5
(Monday to Friday), it can be seen that the electricity consumption rises from 6 AM to around
4000MWh
h , and at 8 AM it reaches somewhere between 5000MWh
h and 5500MWh
h . Again, in the
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evening it drops from around 8 PM to midnight. From 8 AM to 8 PM, the electricity
consumption goes up and down, but the fluctuations are so small that it cannot have a massive
effect on how much electricity is needed. However, at 4 PM there is a clear decrease in the
electricity use. This could be a sign of people on there way home from work and not yet home.
Furthermore, there is an increase in the use of electricity at 6 PM. A sign of people cooking,
using the dishwasher and perhaps doing the laundry. On the graph in figure 5.6, there is only a
small increase at 6 PM. When people come home in the summer, they may rather go outside
and therefore not use a lot of electricity. This pattern is the same every weekday, however in
the weekend the electricity use is different. The consumption in the beginning of the day is not
as high as in the weekdays, however in the winter there is still an increase in consumption at
around 6 PM. These graphs show that the electricity consumption is predictable throughout a
year. Since the production was not predictable, these data should be compared.
5.3 Production and Consumption
Figure 5.7 shows the consumption and the production: Black is total production and red is
total consumption.
Figure 5.7. Graph of Netto Consumption and Production
Figure 5.7 shows that every time the red is visible, there is insufficient production and therefore
the electricity must be bought on NordPool in order to correspond to the electricity
consumption. Again, this graph can only give an overall understanding of the electricity
production in correlation consumption. Therefore, the two weeks which were used earlier in
this section will be used to compare the production and consumption.
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Figure 5.8. Graph of Netto Consumption and Production High Week
Figure 5.9. Graph of Netto Consumption and Production Low Week
As seen in figure 5.8, the production exides the consumption at all times. All the excess
electricity will then be sold. However in figure 5.9, it is only a few hours Saturday where the
production is greater than the consumption, at any other time there would be a need for
buying electricity. Both graphs show that the electricity production is fitted for the
consumption. In figure 5.8, it can be seen that Tuesday where the wind production drops, the
consumption and production curves almost touch each other. The reverse is seen in the
summer week. In figure 5.9 it is seen that the wind production rises and the production curve
passes the consumption curve at Saturday.
This section shows that the consumption is relatively reliable, however when it comes to
production it is not the same case. In order to look further into that, the production for central
and decentral electricity is compared with the electricity from solar and wind.
5.4 Fluctuations
Figure 5.10 shows the production of central and decentral electricity production. (Green:
Decentral, Blue: Central, Red the total combined production)
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Figure 5.10. Graph of Central and Decentral Production
Although the production fluctuates here, it is relatively steady. The production changes with
season and daily consumption, as shown earlier. It is therefore planned, however some of the
electricity may still be sold since the power plants cannot regulate up and down instantly.
Figure 5.11 shows the production of renewable kinds of electricity productions. (Yellow: Solar,
Green: Onshore, Blue: Offshore, Red the total combined production)
Figure 5.11. Graph of Wind and Solar Production
Unlike the electricity from central and decentral productions, the electricity from wind
production is more unsteady. The onshore wind production is the most fluctuating. In the
beginning of 2014, the combined capacity for onshore wind was 4777 MW[22], however, this
was never reached. The offshore wind on the other hand had a capacity of 1500 MW, and at
most times (in winter) the production is 1200 MW. The main differences of wind and
central/decentral production is that it cannot be decided when the production should take
place with wind. In the future the electricity should mainly come from wind. A need for
stabilization is necessary, if Denmark shall not rely on other countries to sell or buy electricity,
when the wind production is lower or higher than the consumption.
It can be concluded that the production varies over a year. Solar production is much higher in
the summer than in the winter. This is reversed for the central and decentral production.
Whereas the wind fluctuates completely throughout a year. The consumption on the other hand
is consistent and predictable hour by hour. Although the consumption varies throughout a day
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and that it changes with the seasons, it is still predictable, which is a great advantage. This can
help when, in the future, the production needs to be ﬁtted even more to the consumption.
Mainly there is an insuﬃcient production of electricity in the summer where the central and
decentral power production is low. This will in the future be even greater.
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The energy system in the
future
6
6.1 Energy in the future
In the former section the load plan was analyzed, and since it is the load plan that will change
in the future an analysis of the future load plan is needed. To analyze the future load plan the
future energy scenarios will be illuminated in the following section.
Before investigating possible future energy scenarios, it is useful to look at the future
consumption. The past four years the tendency has been a drop in electricity consumption [23].
However, the Danish energy agency expects the Danish electricity consumption to increase
with 16% from 2014 to 2025 [24]. In 2050 [25], the Danish energy agency expects the electricity
consumption to be affected by the amount of money invested in bringing down the
consumption. If 8 billion DKK is invested, the electricity consumption will be 10 PJ more than
in 2011. If 13 billion DKK is invested, the consumption will be around the same as in 2011.
Furthermore, if 22 billon DKK is invested, the consumption will be almost 20 PJ less than
2011[25, page 27]. Depending on the amount invested, a different amount of electricity is
needed. Regardless, the electricity shall not come from fossil fuels in the future. The Danish
government has multiple scenarios of the future power production; these will be analyzed in the
following section.
6.1.1 Energy scenarios
The scenarios that will be analyzed are wind, biomass and hydrogen. In all these scenarios 6.1
PJ should come from solar power. Also, in all scenarios wind production is more than half of
the total production. In all three scenarios, none of the power comes from fossil fuels.
Scenario Wind Solar CHP Condense Fuel factories Import Export Total
Wind 246.2 6.1 24.6 5.0 3.9 46.7 -51.9 280.6
Biomass 113.3 6.1 34.9 33.4 4.8 15.4 -42.7 165.3
Hydrogen 295.4 6.1 63.2 23.6 0 6.9 -62.1 320.1
Table 6.1. The electricity production in 2050(PJ) for different scenarios.
[25, page 68]
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6.1.2 Wind-scenario
In the wind scenario, the amount of wind is 246.2 PJ per year, which is equivalent to:
246.2PJ
280.6PJ
· 100 = 87.7% (6.1)
This scenario is designed to a bioenergy consumption that Denmark can deliver by itself (where
some bioenergy can be imported (but is not needed)). In order to keep the bioenergy
consumption down, hydrogen can be used to upgrade biomass and biogas for this to last longer.
The hydrogen is made with electrolysis with the excess power from wind turbines[25, page
5,19]. However, in order for this scenario to work, an electriﬁcation of especially the
transportation sector and heat sector is needed. Therefore, an expansion of the electricity grid
is needed; some of the expansion should help stabilize the electric voltage, frequency, etc. This
means a lot of extra costs for these enforcements. Another extra cost, because of the many
wind turbines, is the need to import electricity when there is no wind and export when there is
more wind power than needed. This can result in having to buy expensive power and sell cheap
power, meaning an extra cost[25, page 10, 75]. The capacity of wind power should be expanded
with an average of 400 MW per year from 2020 to 2050, a total of 12,000 MW. Furthermore,
replacement wind turbines for old wind turbines that can no longer be used is not a part of the
12,000 MW. From 2050, when the wind turbines from 2025 need to be replaced, the
replacement amount will be the same as the new amount, a total of 800 MW[25, page 10, 87].
6.1.3 Biomass-scenario
In the biomass scenario, the amount of wind is 113.3 PJ per year, which is equivalent to:
113.3PJ
165.3PJ
· 100 = 68.5% (6.2)
This scenario is designed to a bioenergy consumption around 450 PJ, which includes garbage
and losses when transported. The 450 PJ is more than Denmark can deliver by itself, 200 PJ
biomass needs to be imported. In this case, hydrogen is not used to upgrade biomass. Whereas
it was crucial to expand the electricity grid in the wind scenario, it is not nearly as necessary in
the biomass scenario, however it is still important. The main focus in the biomass scenario is
that the biomass is used on renovated CHP plants, and is an alternative fuel to fossil fuels[25,
page 10]. As opposite to the wind scenario, the cost is not as high. Other than the fact that a
large amount of wind power was needed, the other part is renovating CHP plants. To renovate
is cheaper than to build new. It is however small variations that should happen, for the wind
and biomass to have the same cost. This could happen if the price on biomass would increase
with 35% or if the cost of the electricity grid would be halved[25, page 9]. As a large amount of
wind turbines are still needed, the plan in this scenario would be to build 400 MW of wind
turbines every third year[25, page 10]. This would then be 4000 MW in 2050.
6.1.4 Hydrogen-scenario
In the hydrogen scenario, the amount of wind is 295.4 PJ per year which is equivalent to:
295.4PJ
320.1PJ
· 100 = 92.3% (6.3)
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This scenario is designed to a small bioenergy consumption around 200 PJ this includes
garbage and losses when transported. In order to keep the bioenergy consumption down
hydrogen should be used as in the wind scenario. This requires more wind power to produce
hydrogen, and therefore the wind production is higher than in the wind scenario[25, page 6,
10]. The main focus here other than in the wind scenario, is to use the hydrogen to upgrade
biofuel, as it is expected that the price of biofuel will rise. As in the wind scenario, an
electrification of especially the transportation sector and heat sector is needed. The costs would
be high, like the wind scenario, but because the bioenergy price in this case is expected to
increase, it can be beneficial. The capacity of wind power should be expanded more and faster
than in the wind scenario, meaning more than 400 MW per year.
6.1.5 Possible future load plan
As analyzed in the present load plan 5, the wind production fluctuates, but the consumption
does not, not more than expected. In a future load plan based on these scenarios, at least 68%
of the production comes from wind. This means the electricity production would be more
unstable. In all cases biomass would be used as a base, supported by hydrogen production via
electrolysis. It would be used to upgrade biofuels to make them last longer. This means that
some of the extra electricity could be used and stored for times when the electricity is more
needed. Also the electricity would be sold and bought on NordPool and a European electricity
market, however it is not a certainty that other countries have electricity when Denmark needs
it.
Lastly, another way to even out the fluctuations is to be able to store energy. This is not
something the Danish energy agency takes into account, and therefore it is not seen as a
possible solution at this moment.
So the conclusion is that the consumption side of the load plan, from 2014 to 2015 the
electricity consumption is expected to rise with 16%, but after that to 2050, the consumption
will depend on the level of investments. But even if the consumption changes it will still follow
the same patterns, and therefore be predictable. The production side of the future load plan is
based on the energy scenarios made by the Danish energy agency. There are three different
scenarios that all have at least 68% energy from wind turbines. This will create a fluctuating
power production, and make the electricity system more vulnerable to errors. In all the
scenarios bioenergy is expected to be the base production supported hydrogen production via
electrolysis. In none of the scenarios it is expected that power storage will be a possibility.
Storage
As mentioned earlier in section 6.1.5, storage is not expected to be a possibility in the near
future. The reason for this is simply that the storage technologies is not fully developed, and
too expensive.
A roughly estimation has been made in “Ingeniøren” of different storage technologies that are
ready to be used[26]:
Pumped hydro: 1.00 DKK/kWh – Using the excess power to pump water up onto mountains
or another tall place to use the water to produce energy as it falls down at a time with an
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underproduction.
Lead batteries: 2.97 DKK/kWh – Using the excess power to storage power in a lead battery.
Tesla Powerwall: 5.65 DKK/kWh - Using the excess power to storage power in a Tesla
Powerwall[27].
A technology that could be used right now because of its simplicity and affordability is pumped
hydro. The only problem with this, is that Denmark practically does not have any mountains,
or any kind of difference in altitude in the country. So if the technology were to be used towers
would have had to be build, which would make the cost per kWh much higher, because of the
greater investment.
Many more technologies are being developed, like using water to produce hydrogen through
electrolysis and then use the hydrogen to produce power in a fuel cell when needed, but the
technology is not ready to be used commercially.
Storage using a Tesla Powerwall
Just by looking at the numbers 5.65 DKK/kWh might not seem like much, but when thinking
about the huge amount of excess power there is produced at some hours in Denmark every year,
the amount will add up. By looking at the consumption and production of power in Denmark
the surplus production can be found for 2014. The calculations can be seen in appendix 9.5.
The surplus production from 2014 is 12,880,623,000 kWh. By multiplying this with the cost
per kWh for a Tesla Powerwall, the cost would be:
12, 880623 · 1010
kWh · 5.65
DKK
kWh
= 7.77551995 · 1010
= 77billionDKK (6.4)
So if all the excess energy should have been stored in a Tesla Powerwall in 2014, it would have
cost 77 billion DKK. So even though some money could be saved by not having to sell power to
the surrounding countries at low prices, there is a great cost by trying to store it in the country.
6.2 Tools for securing the security of power supply
[28, page 40-51]In the following section the tool to secure the security of power supply will be
illuminated. The section will be divided in to three parts:
1. The grid
2. The power production
3. The consumption
The first part will include an analysis of the distribution grid, the transmission grid, and the
future interconnections. The second part will include an analysis of capacity mechanism. Last
the third part will include an analysis of flexible consumption.
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6.2.1 The grid
Distribution grid[29]
The distribution grid has in the last 10 years been the cause of approximately 3/4 or more of
the total power outage in Denmark. Therefore, main focus has been on reinforcing this grid.
One way is by securing the grid against the climate by changing the setup from overhead wires
to buried cables. In 2014, 95.22% of the distribution grid were buried cables. 98% of the grid
concerning voltage levels 0.4kV-20kV are buried. Only 41% concerning 50kV-60kV are buried,
making this part of the grid the next step in reinforcing the grid.
Changing from overhead wires to buried cables has already proved its worth. This is showed in
figure 4.5 when comparing the power outage in year 2005 versus year 2013, when two big
storms hit Denmark (5th January 2005 and 28th October 2013). To be able to look at things in
perspective, only 84.53% of the distribution grid were buried cables in 2005.
Other aspects of securing the distribution network includes securing outdoor control cabinets
against flooding.
Transmission grid
In 2014, 26%[29] of the transmission grid in Denmark was buried cables. In the future, and
even now, Denmark is working on securing the transmission grid by altering the part
concerning 132-150kV from overhead wires to buried cables. When doing this, it also gives a
possibility to restructure the layout of this part of the grid. The reason to why this is
interesting is the rise in the number of decentralized power plants which needs to get connected
to the grid. By restructuring the 132-150kV grid, it will be more suitable and optimized for the
future energy system. A future structure-layout of the transmission grid can be seen in [30,
figure 13 page 25].
In order to cope with the future energy system, with lots of small decentralized power plants
and fluctuating energy, it is necessary to reinforce the 400kV part(the electrical highway) of the
transmission grid. Studies have shown that this grid in particular will be heavy loaded in the
future and therefore something has to be done to ensure that is does not become overloaded
and cause errors. This can be done in different ways. One way is to expand the network to
handle a greater amount of effect. Another possibility is to utilize flexible consumption,
mentioned in the next subsection 6.2.3, to counteract possible overload. Parts of the 400kV
grid is also being buried or restructured. This is done, in accordance with a political
agreement, to beautify the Danish landscape. A future expansion of the transmission network
could also include a second Great Belt Power Link. Analysis have shown that DK2 in the
future could suffer from a negative effect balance. By building a second Great Belt Power Link
this could be resolved. Besides this, a second connection could also increase the security
against power outage, if one of the connections gets a failure. A new connection is only
interesting if it is proved to be the cheapest socioeconomic solution to secure a positive effect
balance. Other solutions could be new interconnections or by the use of capacity mechanisms.
Capacity mechanism will be further explained in section 6.2.2.
Furthermore, work is put into “automating” the grid. The meaning of this is to be able to
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central activate and control production- and consumption-equipment at different voltage levels.
An example of this could be the implementation of synchronous motors, driven by the network,
in order to stabilize the network by producing reactive effect, deliver inertia and by increasing
the short-circuit power. These attributes are called system bearing attributes and are usually
delivered by the generators at active thermal power plants, but due to fewer of these in the
future other options has to be available. Today, when stabilization of the network is needed,
the TSO is buying the needed system bearing attributes from thermal power plants by paying
them to force operation even though it might not be favourable to do from the plants point of
view. In the future this could be avoided by automating the grid.
Future Interconnections
As previously mentioned in section 4.2, Denmark is positioned extremely well in terms of
possibilities for interconnections. New interconnections can not only help strengthen the
Danish grid in terms of effect balance, but also have a significant positive economic aspect in
the long term.
New connections to Great Britain and The Netherlands are currently in the making. The
connection to The Netherlands, called COBRAcable, will get a capacity of 700MW. The
connection to Great Britain, called Viking Link, is currently being investigated if possible, but
the plans states a capacity of 1400MW. What makes connections between Denmark and Great
Britain and The Netherlands interesting is that fact that they will be the first between these
countries. Right now, the only connection on land between Scandinavia and Central Europe is
the one from Denmark to Germany which covers approx. 40% of the total capacity transferred
from Scandinavia to Central Europe. By adding these new connections, it will be possible to
transfer a greater amount of effect and the international grid becomes more secure in the case
of failure. Furthermore, these two connections might have a positive economic aspect in the
long term as well. Today, Denmark acts as price-taker in 90% of the time. Because of its small
effect capacity compared to our neighbouring countries and due to the interconnections
between, Denmark will obtain the same electricity price as one of its neighbours in 90% of the
time. When having in mind, that Denmark and especially Germany has some of the highest
prices for electricity in Europe, new interconnections to Great Britain and The Netherlands
might help in situations with high prices due to the demand exceeding the supply.
Furthermore, Viking Link can turn out to be an economically good investment because the
price of electricity often is higher in Great Britain compared to Denmark. This gives economic
incentive to sell surplus power when supply exceeds demand. Another situation where these
new connections might be helpful, can be in the case of situations with problems selling excess
effect to foreign countries. In other words, these two connections may help Denmark lowering
the price of electricity when the domestic demand exceeds the domestic supply and help
earning money by selling electricity when having excess effect.
New connections to Germany are also in the making. However, these connections are scheduled
for opening in 3-5 years and the reason for that is unfavourable circumstances regarding the
power network in Germany. The problem lies in the German power network being poorly
developed. With that in mind, plus a growing wind energy production in the Northern
Germany, this creates a bottle-neck situation wherein the amount of power transferred to
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Germany becomes limited. Germany is working on reinforcing their power network and by the
time of the opening of the new interconnections, the bottle-neck situation should be reduced.
An overview of new and possible interconnections can be seen below:
Name From To Capacity Status Initiation
COBRAcable DK1 NL 700 MW
Decided/
Under Construction
2020
Viking Link DK1 GB 1400 MW Investigating 2022
Kriegers Flak DK2
DE via
Kriegers Flak
400 MW
Decided/
Under Construction
2019
DK1/DE DK1 DE 2500 MW
Decided/
Under Construction
2021
DK1/DE DK1 DE West 500-1000 MW Investigating 2023
Table 6.2. New and possible future interconnections
6.2.2 Capacity Mechanisms
[28] A second tool to secure the security of power supply in the future could be by paying some
thermal power plants to be available for the market instead of closing down. This strategy is
called a capacity mechanism and is available in three different options:
Strategic reserves
The TSO, in Denmark Energinet.dk, signs a contract with a production plant e.g. a power
plant, to ensure capacity in order to balance the total effect when needed e.g. during the
winter, when the electricity demand usually is elevated. This capacity is called a strategic
reserve. It is not only production capacity which can be considered as a strategic reserve. In
Sweden, flexible consumption has been used as a strategic reserve as well. Flexible
consumption will be further explained in section 6.2.3. By signing a contract becoming a
strategic reserve, the production plant, or capacity, is withdrawn from the wholesale electricity
market and then considered only as peak load capacity. Plants used for the purpose is usually
older plants, with only few years left of the technical lifetime, which would otherwise be closed
due to unfavourable economic production conditions.
A strategic reserve is activated when the demand of electricity exceeds the maximum supply
available at that given time. In other terms, the supply and demand market is not in
equilibrium. One of the key parameters in this situation regards the price at which the
strategic reserve is activated. The reason to this, is the negative influence the price has on the
commercial power plants revenue.
The contract made between the TSO and the power plant, specifies different matters relating
to e.g. payments and technical aspects of the plant. Payments to the power plants for the
strategic reserves is usually divided into two sub-payments:
1. A yearly flat rate to cover the operating expenses of the plant.
2. A rate for every unit the power plant produces.
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Furthermore, it can be specified in the contract how quickly the plant has to be available for
delivering capacity to the spot-market.
Using strategic reserves is currently not a permanent solution. The reason to this is due to
difficulties in the production of electricity. The plants used is usually thermal power plants,
hence both power and heat are produced. This leads to a low efficiency of the plant due to all
the waste heat produced when producing electricity. Strategic reserves have been used in
Sweden and Finland with great success and are also used in Southern Germany as a temporary
solution while deciding the best capacity mechanism solution for the country.
The analysis of the functionality of the electric grid(Analyse af elnettets funktionalitet) states
that this capacity mechanism has the lowest distortion of the market and would be the best
solution for Denmark at the current moment. In relation to this, Denmark has decided to use
this mechanism by demanding 200MW of strategic reserves for DK1 from January 1st 2016 to
December 31st 2018[31].
Capacity Market
Another possible, and more permanent compared to strategic reserves, capacity mechanism is
the establishment of a capacity market. The purpose of creating a capacity market is to ensure
the security of power supply at the most favourable price. This market is characterized by
being established in parallel to the wholesale electricity market. Hereafter, power plants and
consumption reduction resources will have the possibility competing to get the permission to
deliver capacity to the grid when in need. When capacity is needed, two different solutions for
purchasing is possible:
1. Buying capacity at a central auction. Power plants submits capacity to the capacity
market and then the TSO is in charge of purchasing the needed capacity on behalf of the
electricity traders.
2. Buying capacity at a decentralized auction. Instead of the TSO being in charge of buying
electricity, the electricity traders will be responsible for buying it themselves.
One of the best characteristics of the capacity market is its ability to self-maintain the
necessary capacity. With the theory of a perfect competition market in mind, the market will
self-regulate so that if the supply of capacity exceeds the demand, the price for capacity will be
low and vice versa. Another important aspect of the capacity market is the participant’s
obligation to be available for the wholesale market in moments of stress. To cope this, the TSO
is allowed to fine power plants who deviates from this obligation.
The capacity market is widely used in the USA with great success. Furthermore, European
countries like Great Britain, France and Italy, are expected to introduce different variants of
capacity markets by 2020.
Capacity Payment
One last, and less marked based, capacity mechanism is capacity payments. Capacity payments
is constituted by a central administrative fixed payment rate with the purpose of obtaining a
favourable capacity balance. The thought behind these payments is to compensate the revenue
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not covered by the wholesale electricity market. By doing this, it becomes more attractive
being present in the market and as a consequence of this securing necessary capacity available.
Capacity payments may consist of either a flat rate, based on the capacity of the power plant,
or a differentiated rate based on some of the technical aspects of the plant. Technical aspects
which could substantiate the rate could be the plants capability of up- and down-regulating the
electricity production or the plants environmental aspects. The faster the regulation, the higher
rate, and the less environmental impact during production, the higher rate. The key parameter
regarding capacity payments is to determine the correct rate. Due to the rate set
administratively, this results in uncertainties regarding whether the rate can maintain the
capacity balance. The rate is usually set high enough to do this, but at times it is set too high
which causes some kind of economic inefficiency, compared to a market in perfect competition.
In other words, by setting the rate administratively, this often leads to this capacity mechanism
being the most expensive. The basic rate, can be seen as a type of capacity payment as well.
The basic rate is a subsidy given to decentralized power plants in order to encourage
cogeneration and hence keep a low price on district heating.
Capacity payments are used for example in Spain. Usually, the majority of the countries in
Europe aim to choose one of the marked based capacity mechanisms due to better and cheaper
conditions.
6.2.3 Flexible consumption
A third instrument available for securing the security of power supply in the future is flexible
consumption or intelligent electricity system (smart-grid). Consumption can be used to balance
the grid. Examples could be factories or buildings lowering their consumption for a given time
and thereby freeing capacity for the market or using electric immersion heaters or electric cars
to store excess electricity. Especially the situation reducing the consumption is interesting in
terms of security of power supply.
At present, balancing the grid by flexible consumption is not favourable due to a small
available electrical potential for balancing. As the Danish energy system gets electrified in the
future with the use of technologies such as heat pumps (domestic use or district heating),
electric cars, electric heating and so on, the potential of flexible consumption grows as well. By
2020, a theoretical potential of flexible consumption for balancing the grid will reach 2700
GWh which corresponds to the approx. 2.5 times the yearly production from Horns Rev II
(Wind energy) or the yearly electricity consumption of 500,000 households. The intensity of
the effect from the different consumptions will vary. Electric cars will be one of the small
contributors, even though they got some promising aspects in terms of flexible consumption.
They are very effective at balancing the grid for a short time with a short response time and
they can act as a power source or as storage for a shorter period of time.
For flexible consumption to be an option in the future, remotely read meters with hourly
registration has to be present in every single household. The Danish Energy Agency has
imposed all network companies to install remotely read meters in households by the end of
2020.
Bornholm is currently home for one of the largest international smart-grid demo project called
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EcoGrid. The aim of the project is to regulate the electricity consumption on basis of the
electricity price. If the price of electricity is high, the consumers reduces their consumption and
if the price is high, they have the opportunity to shift some of the consumption to times with a
low electricity price.
The former section shows that in 2014 95.22% of the distribution grid was buried cables, and
26% of the transmission grid was buried cables. Furthermore it is shown that expand the
network and to utilize flexible consumption is two possible ways of ensure the transmission grid
against overload and thereby errors. It is also seen that new interconnections can not only help
strengthen the Danish grid in terms of effect balance, but also have a significant positive
economic aspect in the long term.
Furthermore it can be concluded that using strategic reserves are the best solution for Denmark
at the current moment. But another more persistent capacity mechanism compared to the
strategic reserves is the establishment of a capacity market, this is to ensure the security of
power supply at the most favourable prices. The best thing about this market is its ability to
self-maintain the necessary capacity.
At last it is seen that another way for securing the security of power supply is flexible
consumption or intelligent electricity system (smart-grid), which can be used to balance the
grid. At present this way is not that interesting, but the potential of flexible consumption grows
with time. For flexible consumption to be an option in the future, remote meters with hourly
registration has to be present in every single household, which will be installed by the end of
2020.
6.3 Optimum power supply
Even today Denmark is greatly pedendant on electricity to function properly, section 3.3. This
dependence will only grow when looking towards the future, due to the digitalisation of the
world. Fewer and fewer hard copys will be stored, machines will take over a large number of
jobs, that are now occupied by humans and the cash-less sociaty are all factors that will
increase the VoLL over the year. As a reaction to this increase, the optimum security of power
supply should increase in the future too.
Denmark has, due to its’ involvement with the EU, agreed to lower its’ CO2 emmission,
Denmark has even decided to go beyond EU, creating tougher restrictions. To meet these
restrictions, some of the old power plants need to shut down, and renewable will have to
replace them. That will cause the LCoE to increase in the future. As a reaction to this
increase, the optimum security of power supply should decrease in the future
As a result of those two opposite forces, it is safe to conclude that the optimum security of
power supply will remain about the same in the future as it is now.
45 of 75

Discussion
7
As analyzed in section 5 the load plan of Denmark will change over the next years. Mostly the
production plan is expected to change, but this in itself is enough to influence the security of
power supply. This would maybe not be a problem if the high security of power supply we have
currently was not economically optimal, but as calculated in section 3.3 the optimal economical
security of power supply is at the moment 99.96% for the households and this is very close to
the actual security of power supply of 99.996% for the household. Also for respectively
agriculture, service and industry the actual and optimum security of power supply are very
close, the specific data can be seen in table 3.2.
With this analysis the hypothesis stated in chapter 2 is proved, and therefore the need for
improving the security of power supply in the future is confirmed. As analyzed in section 6.3
the security of power supply should remain approximately the same in the future as the current
security of power supply.
The current ways of maintaining the high security of power supply, can be further developed to
fit to the fluctuating load plan. The legislation on the subject will probably change with time,
but the main purpose will not. The way to secure the security of power supply mainly lies in
the technology, the systems used to transport power, and an optimal use of the power market.
The smartest way to make sure that these parameters will be improved is to legislate the
changes. An example of this is in the current improvement of the structure of the power system
as stated in section 4.1. Even though the legislation related to this improvement is not related
to the security of power supply, it does reduce risk of getting errors in the grid. This
improvement involves as stated in section 6.2.1 that the cables is to be buried, and maybe
reinforced if needed.
Another improvement of the security of power supply, is the many future interconnections. As
stated in section 4.2, interconnections are a great asset when trying to improve the security of
power supply, and as stated in section 4.2.1 multiple interconnections are either under
investigation or has been decided to be build. These will help with evening out the under and
surplus production, so the risk of getting errors in the grid is reduced.
To reduce errors in the grid, and a more steady power supply, as stated in section 6.2.2,
capacity mechanisms can be used. According to the Danish energy agency the most suitable
capacity mechanism for Denmark at the moment is to have strategic reserves 6.2.2.
Along with the new interconnection the strategic reserves, can make sure that the Danish
consumers can get power at almost any time. It is practically impossible to prevent blackouts,
but with these initiatives, Denmark can get incredible close to an electric grid without errors.
46 of 75

Semester Project 3: Security of Power Supply

Semester Project 3: Security of Power Supply

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