Flexibility of power system by Dr. Bilal Amjad from Bradford University UK. Very good understanding of flexibility in power system types and features. Long term medium term and short term flexibility Power system operation in flexible modes Demand and supply side power management through balancing operation and services

1. Flexibility of Power System
Bilal Amjad
bamjad@bradford.ac.uk
MSc Smart Grids and Energy Systems
University of Bradford, UK

2. Table of contents
• Definition and introduction
• Why flexibility matters
• Flexibility in traditional power system
• Flexibility with variable energy resources
• Types of flexibility
• Flexibility options
• Future improvements for flexibility
• Flexibility markets in UK, EU and USA

3. Definition of Flexibility
Flexibility is the ability of a power system to maintain continuous
service in the face of rapid and large swings in supply or demand
(ECOFYS).
 “The extent to which a power system can modify electricity
production or consumption in response to variability, expected or
otherwise“ (International Energy Agency).
Modifying generation and/or consumption patterns in reaction to an
external signal (such as a change in price) to provide a service within
the energy system (OFGEM).

4. Introduction
• Power systems are designed to ensure a spatial and temporal balancing of
generation and consumption at all times.
• Power system flexibility represents the extent to which a power system can
adapt electricity generation and consumption as needed to maintain
system stability in a cost-effective manner.
• Flexibility can be up regulation (by additional power and/or reducing load)
or down regulation (by reducing power generation and /or increasing load).
• Power system flexibility is an inherent feature in the design and operation
of power systems.
• Increasing flexibility is key for the reliable operation of future power
systems with very high penetration of variable renewable energy sources
(VRES).
• Video: What Is Power System Flexibility?

5. Flexibility
• The three main services for a flexible and stable power system
oLoad balancing
oFrequency/Voltage response
oCongestion management
• There are three important factors that indicate the flexibility of a
power plant:
oRamp rate
oCold-start time
oStart-up costs

6. Flexibility Factors
• Ramp rate: It means how quickly a power plant’s power output is
changing, either by increasing (ramp up) or decreasing(ramp down) in
MW per minute.
• Different power plants have different achievable ramp rates.
• Nuclear power plants have slow ramp rates compared to hydro or gas
power plants.
• Power plant with slow ramp rate (e.g. nuclear) provides so-called
baseload power.
• Power plants with the ability to ramp up and down quickly are
important elements of a flexible power supply, particularly in meeting
peak demand.

7. Flexibility Factors
• Gas turbines (orange area) do indeed ramp up along with
hard coal around Christmas break.

8. Flexibility Factors
• Cold-start time: It indicates the number of minutes required to turn a
power plant on and ramp it up to at least its lowest turndown levels,
so it can be synchronized with the power grid and supply electricity. T
• he faster a power plant can start up, the faster it can start serving
regional power needs when urgently called upon.
• This capability is critical to offer to grid operators to maintain system
stability in near-emergency conditions.
• Start-up costs: It reflecting the cost expenditures, each time the asset
is started from a cold stop.
• Each time a fossil fuel power plant is required to initiate operation,
this cost needs to consider.

9. Flexibility in Traditional power system
• In traditional power system, flexibly is provided almost entirely by
controlling the supply side, also called load following.
• Power plants that are less flexible (longer minimum run times and
slower ramp times) serve base load energy, while plants that are
more flexible (shorter minimum run times and quicker ramp times)
are better-suited to filling peak demand.
• Power plants (nuclear and coal power plants), which are
conventionally considered inflexible power plants, can be redesigned
to become more flexible.

10. Flexibility in Traditional power system
• Now a days, the hard (anthracite) coal power plants performed their
flexibility potentials to fed to the grid when the residual load is above
a certain threshold.

11. Flexibility in Traditional power system
• This excludes most
renewables since
their operational
flexibility is partially
dependent on
weather conditions
such as solar
irradiance and wind
speed.

12. Flexibility with Variable Energy Resources
(VERs)

13. Flexibility with Variable Energy Resources
(VERs)
• VERs reduce the flexibility sources in the system by displacing
traditional supply side flexibility providers while increasing the need
of flexibility due to their inherent stochastic nature.
• This creates a “Flexibility Gap” that needs to be covered by new
flexibility options.
• In a system with increasing shares of VERs, additional flexibility is
needed to maintain system reliability as the variations in supply and
demand grow to levels far beyond what is seen today.

14. Flexibility with Variable Energy Resources
(VERs)
• Now Flexibility can be define as, the capability of a power system to
cope with the variability and uncertainty that solar and wind energy
introduce at different time scales, from the very short to the long
term, avoiding curtailment of power from these variable renewable
energy (VRE) sources and reliably supplying all customer energy
demand.
• Video:
• Flexibility for variable renewable energy in energy intensive industries
• Webinar (for detailed information):
• Flexibility: the path to low-carbon, low-cost electricity grids
• Flexibility of Power System

15. Flexibility – different flexibility sources for different
flexibility needs
• Different flexibility options must be deployed for different flexibility
needs.
• Regarding the time component, the lead time (time between the
flexibility request and the flexibility delivery) and the duration (how
long flexibility is needed) characterize short- and long-term flexibility.

16. Flexibility needs along the flexibility timeline
Lead time is more important for short-term flexibility, duration is more
important for long-term flexibility. (BRP: Balancing Responsible Parties)

17. Flexibility Options
• Renewable Energy Power Plants
• Energy Storage Systems
• Interconnection
• Demand Side
https://www.youtube.com/watch?v=fF9ebrtKXn8

18. • Hydroelectric power plants and geothermal power plants are perhaps
the most flexible among all the fully dispatchable energy sources.
• For wind and solar which are variable in their nature, when there is
no wind nor solar, other sources will still be needed,
• But flexible variable renewables still have some system, economic and
environmental benefits in the near future.
• Weather forecasts and temperature-dependent demand forecasts can
be used to estimate the need for flexibility and the dispatch of
controllable technologies is managed accordingly.
Flexibility from Renewable Energy Resources

19. Flexibility from Energy Storage Systems
• Pumped storage systems have long been used, and certainly will play
a bigger part in the new power system for providing flexibility.
• At a local scale, variable renewables with small scale battery storage
can smooth the power output of VERs with less energy loss, and will
play a bigger role in residual load flexibility in the future
• Parking electric vehicles can also be a potential storage option,
electrification of the transportation sector can also increase flexibility
of the power system.
• Similarly, Power-to-Gas and Power-to-Heat storage will also cover
some flexibility needs in future.
Video: Vehicle-to-Grid

20. Flexibility from Interconnection
• Better interconnections between grids can also ease some of the flexibility
demand to neighbouring grids.
• For example, during the winter of 2016 and 2017, large amount of nuclear
capacity was unavailable to serve electricity in France. Imports from British,
Germany, and other neighbours reduced France's need to turn on too
much gas power plants (their marginal electricity producers) during the
events.
• The UK and Norway are to build the world’s longest undersea
interconnector to provide enough low-carbon energy for almost 750,000
British homes.
• Conventional electricity sources may often choose to export electricity
rather than ramping or shutting down when interconnection is better.
Subsea power cable between the UK and Norway

21. Flexibility from Demand Side
• Demand has a significant potential and is an important part of future
vision for a flexible energy
• As energy demand will increase by electrifying heating or the
transportation sector, it can provide innovative ways of demand side
management to contribute to power system flexibility.
• An example of this occurred during a solar eclipse event in Germany
in 2015. Aluminium factories were asked to lower power demand
during the few minutes, and the grid went through the event with no
major incident.

22. Flexibility from Demand Side
• US Will Have 88 Gigawatts of Residential Demand Flexibility by 2023
Cumulative Potential for Behind-the-Meter Residential Flexibility, 2017-2023E

23. Future Improvements
New Design Mindset of Power Plants:
• In the past, conventional power plants were designed to run around the
clock with little variation of power output.
• For existing conventional plants, retrofitting them may be able to increase
their flexibility
Smart Grid:
• With the digitalization of the grid and smart meters implemented for
consumers, the demand and supply of electricity can be adjusted with
automated real time communication between the devices.
• This will increase the flexibility of the power system, increase the network
capacity and reduce demand of additional storage.

24. Future Improvements
Demand Side Management: Incentives for Flexibility
• Demand side management (DSM), also called load management, refers to
the management of the demand for electricity through the targeted
switching off and on of loads according to market signals.
• The full potential of residual load flexibility has still not been performed
due to the technical limits and the fear of losing revenue for conventional
operators.
• The distribution systems operators charge the customers a lower energy-
related grid fee, if they provide grid-friendly control services, which could
give incentives to more flexible demand side management or variable
renewable operations

25. Future Improvements
Flexibility in Decentralized Systems
• For decentralized power systems such as micro-grids or emergency
backup systems, diesel generators are the main dispatch able sources.
Energy storage System:
• Mass deployment of new energy storage technologies will only be
economically reasonable and necessary in the late middle stages of
the energy transition, and seasonal storage technologies will be
important in the final push for 100% renewable-based energy
systems.

26. Future Improvements
Blockchain Technology
• A blockchain is, a time-stamped series of records of data that is managed
by a cluster of computers not owned by any single entity.
• Originally devised for the digital currency, Bitcoin blockchain, the tech
community has now found other potential uses for the technology.
• The blockchain database is not stored in any single location, the records it
keeps are truly public and easily verifiable.
• Hosted by millions of computers simultaneously, its data is accessible to
anyone on the internet
• Videos
What is blockchain technology
Blockchain technology for greater flexibility in the electricity grid system

27. Flexibility Markets
• Flexible Technology can include batteries, wind, solar + storage, CHP,
Electric Vehicles (EVs) and other technologies.
• These Flexible Technologies can provide ‘Flexibility Services’ to
Electricity Networks, to help solve congestion issues on the grid and
release additional capacity, which in turn allows connection of more
low carbon technologies such as renewables.
• Power System Flexibility in Great Britain
https://www.energynetworks.org/electricity/futures/flexibility-
in-great-britain.html

28. Flexibility Markets– GB
• To balance the system, the System Operator (SO) contracts for
balancing services from providers, including frequency response and
reserve.
• Ofgem set out two broad types of flexibility:
1) Price flexibility: It will occur when any party varies its demand or
generation in response to the price of energy, at a particular time
and/or location in the network.
2) Contracted flexibility: Where parties trade and directly contract
with one another to procure flexibility.

29. Flexibility Markets– USA
• CAISO and MISO (Independent system operators (ISOs) in the United
States)—have proposed market-based flexible ramping products
(FRPs) to meet both the variability and uncertainty of the net load
and to achieve higher net response from the existing controllable
resources.
• The FRPs introduce two new market design variables to the existing
unit commitment and economic dispatch formulations:
1. Flexible ramp-up (FRU) capability
2. Flexible ramp-down (FRD) capability
Source: Wang Q., Hodge B. M., Enhancing Power System Operational Flexibility with Flexible Ramping
Products: A Review, IEEE Transactions on Industrial Informatics, 2016

30. Flexibility Markets– EU
• Different flexibility markets exist for different flexibility needs of the
electricity system. The colours indicate the suitability of each market
to provide products for different periods of time
CoBA: Coordinated Balancing Area, FCR: Frequency Containment Reserve, aFRR/mFRR: automatic/manual
Frequency Restoration Reserve, BRPs: Balancing Responsible Parties

31. Flexibility Markets– EU (coordinated balancing
area markets)
• The markets for short-term flexibility are balancing markets and
generally separated into three or four different sub-segments or
steps: FCR/aFRR/mFRR/Reserve Markets.
• Replacement reserve (RR) means the active power reserves available
to restore or support the required level of frequency restoration
reserve (FRR) to be prepared for additional system imbalances,
including generation reserves, with activation time from 15 minutes
up to hours.
• In many market designs like Germany, Belgium or Austria this is left
up to the market itself, in others like France the TSO procures a
tertiary replacement reserve.

32. Flexibility Markets– EU (wholesale markets)
• A market for flexibility is the intraday market. It is characterized by up to 30 min
lead time and down to product lengths of 15 minutes, generally the intraday-
liquidity increases with the respective VRES share.
• In general, liquidity in the hourly or quarter hourly day ahead market is much
higher.
• Future markets with seasonal price differences exist and could be used for trading
season price spreads.

33. Flexibility Markets– EU (future markets)
• New markets are regional markets, arising through decentral power plants
and prosumers.
• First cap-products have been introduced on energy exchanges as well,
supplying a hedge for extreme spot market prices in intraday markets.
• Insurances or reserve power plants may offer flexible load to balancing
responsible parties to hedge high balancing cost.