Smart grids incorporating hydro power-reverse pumping-floating solar plants-wind energy-a

OFFSHORE ENERGY SYSTEMS SA
Address: 67 VOUTSINA STR., GR 15561 HOLARGOS, Greece
Tel. +30 210 6775 003, Fax +30 210 6812 770, www.martech.gr, email: tech@martech.gr
IntegrationofHydropowerwithFloatingsolar&Windpower
towardsselfcontrolledSmartGrids
INTEGRATION OF HYDROPOWER STATIONS WITH SOLAR
AND WIND ENERGY TOWARDS SELF CONTROLLED
SMART GRIDS

towardsselfcontrolledSmartGrids Renewable energychallenges inGreece
 Solar energy aims to contribute by 30% to the total renewable energy sector,
while wind energy by 50%
 Greece aims at 35% penetration of renewable energy to national total energy
consumption and more than 60% to electricity consumption by 2030
 This would require about 3.5 GW of wind power and nearly 5 GW of solar
plants to be installed by 2030
 The inherent stochastic and unpredictable nature of renewable sources create
grid instabilities and leads to low RES penetration
 The fragmented topography of Greece leads to small scattered installations with
high investment and operational costs
 The inefficiencies of the Greek power system result to low efficiency factors of
the Greek system

towardsselfcontrolledSmartGrids Energy quality andefficiency -Issuesregarding RES
 Renewable energy, especially wind and
solar, is of unstable nature not following
the demand, not adapted to production
norms, as shown in the diagram
 Spatial distribution of wind and solar
sources has a smoothing effect, but it is
inadequate to stabilize the system. The
interconnection with neighboring countries
can also help in normalizing the grid and
increase penetration
 Required balance, frequency and voltage
regulation cannot be achieved with RES
alone. Additional power is needed with
high response time (spinning reserves),
mainly based on fossil fuels
IntegrationofHydropowerwithsolar&windenergytowardsSelf
ControlledSmartGrids
Daily production of a wind farm
Smoothing effect of multiple wind mills
Inefficiencies of both the renewable & the base
stations (forced to operate far from optimum point)

 Capacity factors in the Greek energy system*
 Capacity factors in USA**
H/E Wind energy Solar Energy
Power
(GW)
Production
(TWh)
Capacity Factor
(CF)
Power
(GW)
Production
(TWh)
Capacity Factor
(CF)
Power
(GW)
Production
(TWh) Capacity Factor (CF)
2020 3.4 5.5 18% 3.6 7.2 23% 3 4.6 18%
2022 3.7 6.2 19% 4.2 10 27% 3.9 6.3 18%
2025 3.7 6.3 19% 5.2 12.5 27% 5.3 8.5 18%
2027 3.7 6.3 19% 6 14.3 27% 6.3 10 18%
2030 3.7 6.4 20% 7 17.1 28% 7.7 12.1 18%
*Data from
ESEK 2019
**Data from USA
Energy Information
Association
The low efficiency of the Greek RES sector is a remarkable conclusion studying
actual and projected data
Energy quality -Issuesregarding RES

Energy Storage asananswer toRESinefficiencies
 Energy storage can provide a bridge between supply and demand, can reduce
wind farm stoppages and improve efficiency
o Reverse pumping
o Batteries
 Methods under discussion in Greece this period :
 Hydrogen production can also be a help in
exploiting excess power from wind stations
 One method which is absent from the
internal discussion is the energy storage
in the form of compressed air
o Air storage in old mines (large scale
applications in USA, Germany)
o Storage in balloons at large water depths,
already developed in OES

towardsselfcontrolledSmartGrids Opportunities ofartificial lakesinGreece
 Reverse pumping offers a proven method of increasing efficiency. A number of
projects are under development or in planning phase
 What it is stressed here is that instead of developing new reservoirs we have to
investigate how to exploit the existing ones
Ονομασία Επιφάνεια (τ.χμ.) Βάθος (μ)
Ωφέλιμος όγκος (m.
m3)
Ελάχιστη Στάθμη
Λειτουργίας (m)
Μέγιστη Στάθμη
Λειτουργίας (m)
Διαφορά Στάθμης
(m)
Ύψος
Υδατόπτωσης (m)
Κρεμαστών 68.53 60 2760 227 276 49 132
Καστρακίου 26.8 50 52 142 144.2 2.2 75
Στράτου 8.4 20 12 67 68.6 1.6 37
Λάδωνα 3.05 25 46 400 420 20 239
Αώου 11.5 144 1315 1343 28 675
Πουρναρι Ι 18.23 304 100 120 20 79
Πουρναρι ΙΙ 18.23 4 33.4 40 6.6 14
Πλαστήρα
(Ταυρωπού)
22.18 48 300 776 792 16 577
Πολυφύτου
(Αλιάκμωνα)
56.79 80 1089 270 290 20 146
Σφηκιά 4.3 18 141.7 146.5 4.8 60
Ασωμάτων 2.6 10 80.5 85.5 5 42
Άγρα 5.8 4 477.8 480.3 2.5 156
Θησαυρού 20 175 563 320 380 60 154
Πλατανόβρυσης 3.25 95 12 223.5 227.5 4 74
269.67 5318
*Main source of data
the presentation by
J. Argyrakis

towardsselfcontrolledSmartGrids The idea…
1. Exploit lake surface to Develop Floating solar plants
2. Exploit reservoir capacity to Develop Reverse pumping
3. Combine the two energy sources to control the overall power
4. Introduce also wind power to form an independent grid, Ring Grid, which
incorporates all different power units operated by a controller and an
allocator to provide high quality energy according to demand
5. Introduce the idea of the Virtual Ring Grid which may have the same
effect as the physical network

 The lakes provide a theoretical capacity of more than 30 GW of solar power
 10% of this area could host more than 3.5 GW and it can double the power of
the existing Hydro-Power Stations
 Hydropower stations have already developed a complete electrical system
which means considerable savings of the required CAPEX to develop complete
solar plants

 Installing floating solar plants will have positive
environmental impact:
o It will reduce evaporation
o It will reduce algae increasing water
oxygenation and increase fish population
o It will reduce pressure on productive
agricultural land in achieving the targets of the
“ΕΣΕΚ”
 It allows large scale installations compared to
fragmented small land installations
 It presents improved panel performance due to
cooling effects

RIGID Floating Module (RFM)
By connecting 4 basic modules in parallel
Panels per module: 60
Power per module: 18.9 KW
Total area per RFM: 144 m2
Basic Floating Module (BFM)
Power per module: 4.7 KWPV Panel
Power/panel : 240 W
 A highly structured system has been developed within OES
TheproposedFloatingSolarStationsatthelakes -OESsystem

ELASTIC Floating Module (EFM)
Rigid modules/elastic: 25
Power per module: 473.6 KW
Total area per RFM: 3720 m2

MOORING COMPLEX (MC)
Elastic modules/mooring complex: 25
Panels per complex: 37500
Power per module: 11.8 MW
Total area per MC: 103.000 m2
Considering 20% improved performance due to
operating environment (cooling effect)
Mooring Complex accounts for 14.8 MW
A complete and autonomous power station
Connecting elastic modules with special internal
lines leads to mooring complexes

towardsselfcontrolledSmartGrids Mooringfloatingmodulesinavariableenvironment
 The major problem in designing floating solar plants at the lakes is the variable water level
 Water level variations with the current operations at the artificial lakes can be above 50 m
The OES system can be shortly described as follows:
o A group of Elastic Modules (EM) are connected together with elastic lines with adjustable
elasticity (internal lines)
o The group is anchored to the bottom with external lines of catenary shape
o The distance between EM, at the lowest water level, is enough for a small boat to have free
and safe passage
o As the water level increases, the distance between EM increases as well, keeping the stiffness
of the external lines at acceptable levels and the overall stiffness within the safety margins

towardsselfcontrolledSmartGrids Solution viability
Number of elastic modules 25
Number of rigid modules 625
Number of basic modules 2,500
No of PV panels 37,500
Total area of floating modules 90,000m2
Total power 11.800 KW
Estimated Produced energy per year 17,300,000KWh
Using a mooring complex
as the base case
Investment Cost per KW < 950€/KW
Cost of energy per KWh <0.034€/KWh
Internal Rate of Return >12%
A Mooring
Complex
contains
Costs will be further reduced and
capacity factor improved with
increasing size of the investment
However energy quality emerges as a significant
issue.
Combined solar with hydropower may make
possible to feed the grid with high quality energy
according to demand

Pilot Program
Dimensions(LxB) 54.5x54.5mxm
Number of basic modules 64
Number of rigid modules 16
Number of elastic modules 4
Number of Panels 960
Power 302.9KW
Total area of floating system 2,970.30m2
Power per saquare meter of floating 102Wp
Area of panels 1,514.70m2
% coverage 51%
Apilottypicalapplication
Minimum water depth: 50 m
Maximum water depth: 100 m
Minimum distance between elastic modules : 6 m
Maximum distance between elastic modules: 24 m

towardsselfcontrolledSmartGrids B.Combining Solar Power atthelakeswithHydropower
(Limited controllability)
(Improved controllability)

 A local grid is created which is controlled by a
controller and an allocator
 An input signal O(s), by the operator, commands
the controller for a certain power production or
even a daily production trajectory
 The controller receives signals from sensors
giving info of several parameters as is, operating
point of the involved units, current production
from the solar units, water level on the reservoirs
etc
 Additional info can or have to be input as is
minimum ecological supply, agricultural
requirements etc.
Designinganeffectivecontroller(Hydro+Solar)
 The controller calculates the necessary actions and the allocator undertakes the task to
distribute the action to the individual units which are controllable (mainly hydro and pump
units)
B.Combining Solar Power atthelakeswithHydropower
o Inclusion to the local grid of wind
power will be a critical step ahead
o Integration of hydro and solar power
is expected to have marginal results

towardsselfcontrolledSmartGrids C.Introducing windenergy –TheRingGridconcept

 An independent grid (Ring Grid) is created connecting :
o Local hydropower stations in which reverse pumping is considered
o Existing wind farms in the area, or new wind farms are connected to the ring
o Solar plants at the lakes are either directly connected to the grid or they form a local grid
with the hydro stations
Designing aneffective RingGridcontroller

Designing aneffective RingGridcontroller
 Sensors, with wire or wireless connections measure essential parameters of the system in
real time, as is current production from the productive units, input water flow, water level
at the reservoirs, ecological supply, power parameters at the hub connecting with the grid
etc.
 Controller receives a command from the operator and calculates the necessary action to
satisfy this command. In addition to the operators command a number of norms (internal
commands) should be satisfied regarding the quality parameters of the output power
(Frequency, voltage), the ecological supply etc.
 Allocator (allocation logic) receives the command from the controller and allocates the
action to the individual units which are controllable (hydro power, pumps, but also some
parameters of the wind and solar plants)
 Given that hydro and pump units are highly controllable with short reaction times, an
effective control system can act as a spinning reserve
 Wind measurements at the individual wind farms, or other parameters can be fed forward,
as well as prediction models (long and short) can be incorporated

 Can incorporate large volumes of wind and solar power
 Can unify the isolated power units into one complex unit
with characteristics of spinning reserve
 It can provide guaranteed power to the national grid
 It can also supply services to the national grid to control
power quality (regulate frequency and voltage)
TheRingGrid…….
The extent to which this unified unit can play its role depends on the hydro
and reverse pumping components
Their power but also their control and controllability characteristics, the
response times, can make the system of even 1st reserve type of power
station

INTEGRATIONOFHYDROPOWERSTATIONSINGREECEWITHSOLARAND
WINDENERGYTOWARDSSELFCONTROLLEDSMARTGRIDS
Thecaseof ACHELOOS
Reservoir
Capacity (m3)
Installed Power
(MW)
Total Installed
Power (MW)
Kremasta 2,760,000,000 4x109.3 437.2
Kastraki 52,000,000 4x80.0 320.0
Stratos 12,000,000 2x75 150.0
2,824,000,000 907.2

?
?
with pumping without
Installed Y/E power MW 907.2 907.2
Pumping Power to be installed MW 1,050.0 0 Pa/Pb
Produced energy GWh/period 1,396.2 702 1.99
Absorbed Energy GWh/period 1,722.8 0
Utilization factor 0.53 0.27
Supply +Agricultural+Losses m3/period 104,976,000 54,666,667
Ecological Supply m3/period 890,267,314 3,221,000,000
Reserves
Start of period
(m3)
End of period
(m3)
Special
Consumption
(m3/MWh) GWh
Kremasta 2,640,000,000 3,036,749,640 3,300 920
Kastraki 41,600,000 47,907,260 5,800 8.3
Stratos 9,600,000 10,979,786 11,700 0.9
total 2,691,200,000 3,095,636,686 929
Q=135 m3/sec
* Basic data have been taken from John Argyrakis presentation “Η Υδροηλεκτρική Παραγωγή της ΔΕΗ ΑΕ”
Thecaseof ACHELOOS
1. Introducingreversepumpingoperation
1st Hydrological period

Pumping Power to be
installed MW 1,050.0 0 Pa/Pb
Utilazation factor 0.46 0.19
Supply
+Agricultural+Losses m3/period 88,646,400 54,666,667
Ecological Supply m3/period 863,096,508 3,221,000,000
Reserves
start of period
(m3)
End of period
(m3) S.C. GWh
Kremasta 3,036,749,640 3,068,227,776 3,300 930
Kastraki 47,907,260 49,213,244 5,800 8.5
Stratos 10,979,786 11,412,758 11,700 1.0
END 3,095,636,686 3,128,853,778 939
Q=90 m3/sec
Thecaseof ACHELOOS
2nd Hydrological period

Pumping Power to be
installed MW 1,050.0 0 Pa/Pb
Utilazation factor 0.48 0.14
Ecological Supply m3/period 1,100,194,802 3,221,000,000
Reserves
start of period
(m3)
End of period
(m3) S.C. GWh
Kremasta 3,068,227,776 2,624,731,032 3,300 795.4
Kastraki 49,213,244 41,778,308 5,800 7.2
Stratos 11,412,758 11,704,836 11,700 1.0
Total 3,128,853,778 2,678,214,176 803.6
Q=70 m3/sec
Thecaseof ACHELOOS
3rd Hydrological period

towardsselfcontrolledSmartGrids with pumping without remarks
Pumping Power to be installed MW 1,050.0 0 Pa/Pb
Utilization factor 0.49 0.20
Ecological Supply m3/period 2,853,558,624 3,221,000,000
Reserves
start of period
(m3) End of period (m3) S.C.
eq.
GWh
Kremasta 2,640,000,000 2,624,731,032 3,300 795
Kastraki 41,600,000 41,778,308 5,800 7
Stratos 9,600,000 11,704,836 11,700 1
Total 2,691,200,000 2,678,214,176 804
Annual results
• Agricultural supply is significantly increased
• Savings is expected by reducing evaporation if floating solar power station will be installed
• The ecological supply remains at the same levels, but it is a continuous and controlled flow compared
to “wavy” supply of today
o This energy is of low quality, low cost or even rejected energy
o The more energy absorbed the more wind and solar energy can be incorporated
in the system
Thecaseof ACHELOOS

Kremasta
Theoretical solar power 1.2 GW Kastraki
Theoretical solar power 423 MW
Stratos
Theoretical solar power 225 MW
Thecaseof ACHELOOS
2. Introducing floatingsolarpanels

towardsselfcontrolledSmartGrids TheRingGridofAcheloos
Hydropower equiv. 2.5 GW
Solar power : 1 GW
Wind Power : 1,5 GW
Capable to:
 Over double the existing hydropower at Acheloos complex
 Incorporate about 1.5 GW of wind power
 Incorporate more than 1 GW solar power
 Operate as a unified station
 Become one of the biggest units in Greece of the type of spinning reserve
 Replace lignite from the Greek power system
 Create over double capacity factors of the connected wind farms

towardsselfcontrolledSmartGrids TheVirtualRingGridofAcheloos
 So far we considered the Ring Grid as a
physical network on which the individual
units are connected
 The required investment to materialize such a
grid by rearrangement of the existing or by
installing new lines could be high and put the
whole idea in jeopardy
We hereby introduce the idea of the Virtual Ring as
opposed to the physical one
o The controller will continue to receive data from the sensors and command them to operate
as if the individual units were connected to a real grid
o It is expected that the overall effect on the national grid would similar or even the same as
the effect that a real network would have to the national grid
o The development of a simulation model able to compare the operation on the two distinct
cases would reveal the prons and cons and the peculiarities in both cases
In The Virtual Ring

towardsselfcontrolledSmartGrids Technical difficulties ofAcheloos project
Acheloos project presents significant technical difficulties
which if it was only a reverse pumping project it could easily
be dropped
However the concept of the Ring Grid and especially the
Virtual Ring Grid forces to find solutions
Two major problems were identified:
A. A reservoir is needed downstream of Stratos
B. The length and shape of the required pipelines for reverse
pumping, especially between Kremasta and Kastraki
Διαδρομή Μήκος (m)
Μανομετρικό
ύψος (m)
Οζερός-Στράτος 9,000 45
Στράτος-Καστράκι 3,000 85
Καστράκι-Κρεμαστά 18,500 135

 The Ozeros lake has an area of about 10 sq.km and a
water depth of about 8-10m
 With a dam in the south and east side of about 8
meters a new storage capacity of more than 80 m.m3
is created
 Capable to serve the reverse pumping requirements
but also to secure a smooth ecological supply
 It will also prevent uncontrolled flooding's
A. The reservoir downwards Stratos
B. The large length of the required pipelines for reverse
pumping
Route
Length before
(m)
Length after
(m)
Μανομετρικό
ύψος (m)
Οζερός-Στράτος 9,000 9,000 45
Στράτος-Καστράκι 3,000 3,000 85
Καστράκι-Κρεμαστά 18,500 4.000 135
 The pipe length especially between Kastraki –
Kremasta of 18.500 m may be prohibitive
 A solution is shown on the sketch which can reduce
the length to 4.000 m and provide a smooth route
Technicaldifficulties ofAcheloosproject
andproposedsolutions
Ozeros Lake with dam

THE CASE OF ACHELOOS INDICATES:
INTEGRATIONOFHYDROPOWERSTATIONSINGREECEWITHSOLARAND
WINDENERGYTOWARDSSELFCONTROLLEDSMARTGRIDS
 The concept of the ring grid and especially the virtual grid provides a significant opportunity to
further increase the RES penetration to the Greek national system, in an effective way
 Major hydro systems in Greece, as is Aliakmonas, Nestos, should be also studied to identify
opportunities in developing corresponding ring or virtual ring grids
 It can be said that the concepts presented here can fully cover and satisfy the targets set by
ESEK not for 2030 but for 2050
OES has a good teem of engineers and academic staff which can be accompanied by a good teem
of PPC and PPC ananeosimes senior members to carry out all necessary studies and actions to
realize the project

ACTIONS TO BE TAKEN
1. Initiate the license procedure for the floating solar plants at all lakes
Start necessary technical studies including:
 Bathymetric studies at the lakes
 Bottom inspection, subsurface profiling
 Chorothetisi Solar parks based on multiple criteria (current uses and activities –
effects on them, lake bottom profile and characteristics, water level variations etc)
 Strategic Environmental studies for each case to be developed
 Weather conditions, criteria for designing with 100 years return period
 Initial mooring studies
2. Initial technical studies for the reverse pumping development at all major reservoir
complexes – operational modelling
3. Development of models of the ring and virtual ring on specific cases (Acheloos, Aliakmonas,etc),
 Controller and allocator design
 Wireless or wired sensors, requirements, specifications
 Controllability requirements upon new pumping installations
 Simulation results and comparisons –physical vs virtual grid
 Final system design
4. Choose a test case for practical application

Smart grids incorporating hydro power-reverse pumping-floating solar plants-wind energy-a

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