The value of BESS as a
transmission asset (SATA)
for the power system
Grid Challenges during energy transition and
battery’s role in providing solutions
Dr. Sankara Subramanian
TOPICS
1. Grid challenges today – WW : slide# 3
2. Saft’s classification – existing & new services : slide# 4
3. “New applications” gaining momentum – “Congestion & Inertia” : slides# 5-9
4. UK Grid situation (challenges & Solutions) : slides# 10-11
5. BESS performance during actual disturbance : slide# 12 -13
6. Applications vs requirements – Grid & Developer side : slide# 14
7. Value drivers and remuneration : slide# 15
8. How the future looks like for Grid “Flexibility” resources : slide# 16
9. Grid Substation: BESS Use-cases : slide# 17
What challenges does de-carbonization present to the
Grid?
Less dispatchable More asynchronous More variable sources of Generation moving to
generation generation generation different areas
Reduction of coal & gas Increase of renewable Increase of renewable New generation located
synchronous generators generators connected by generators based on at network extremities
➔ Less firm, flexible inverter-based technologies intermittent, unstable and with low demand such
power and system increasing stability risk nature dependent source as offshore or
services like voltage and distribution networks
stability ➔ Limited system services ➔ Operation challenges
➔ Less inertia, less grid ➔ No inertia & ➔ Increased power ➔ Network
services ➔ Lesser system strength required congestions
➔ Curtailment as well Source: NESO
as capacity (non-
spinning) needs
World is fast moving away from the historic construct of base load and peaking to today and future’s world of
variable renewable energy and firming.
Segmentation of the Grid Ancillary services and its pressing
need?
B C
A D
3C’s: Congestion, Curtailment, Capacity
Saft’s classification of Ancillary Services
How batteries help manage congestion?
• Virtual transmission line*
• Grid boosters*
• Virtual Distribution capacity
*Source… IET G, T&D special issue, Nov’22: Operation strategies of battery energy storage systems for preventive and curative congestion
management in transmission grids – authored by Martin Lindner, Jan Peper, Nils Offermann, Charlotte Biele, Milijana Teodosic, Oliver Pohl, Julian
Menne, Ulf Häger
Preventative congestion
Application -1
Battery as Virtual transmission lines
This congestion is caused by the steady state
increase in power that leads to increase in
temperature rise of conductors and therefore needs
actions before a real contingency has occurred in the
network.
1) arrows pointing upwards shows dis-
charging and downwards shows charging of
batteries.
2) arrows in “black” are preventative
congestion measure.
“Day ahead market”
Ringo project in France
Curative Congestion Application -2
Battery as Grid Booster (during n-1 contingency and to reduce re-dispatch costs)
When a real contingency happens, the amount of added
power the rest of network must carry on can lead to
thermal stability issues along with other issues, so
corrective actions needed to be taken in short duration
following the contingency to avoid further disconnections
of circuits.
Both the charging and discharging of batteries happen F
simultaneously at either end of the “now congested line”.
1) arrows pointing upwards shows dis-charging
and downwards shows charging of batteries.
2) arrows in “red” are curative congestion “Still being part of regulated market”
measure.
Transnet BW in Germany
Virtual Distribution Capacity Application -3
Problem Solution
(1) Like “Virtual transmission lines”, similar services are available with BESS at the
distribution level.
(2) The transformer’s capacity can exceed during the peak times to support load,
(3) Therefore, distribution planners, can upgrade the transformer capacity or install BESS
downstream of the transformer to ensure its limit is not exceeded for few more years.
“Day ahead market”
How batteries help manage inertia of the grid? Application - 4
A reduction in inertia of 100GVA seconds will result in a drop in frequency of 0.3Hz.
System frequency rapidly degrade in less Inertia system
with higher RoCoF and will be critical to arrest the fast
degradation. Today the practise is to use combination of
Multiple resources for the 10 seconds’ period.
Later half of 5-10 seconds are also called as Dynamic containment (DC)
or Frequency Control Ancillary Services (FCAS)
“Spot market”
Synthetic Inertial support in system with less inertia
UK Grid situation – Headlines (1/2)
❖ The inability to connect new renewable resources to the electricity grids is hampering
energy projects – with a queue that has more than twice the amount of energy generation in
the queue than is needed for 2035 decarbonised energy system target.
❖ Curtailment of already connected renewable resources leading to millions of £ payments
by the system operator NESO.
❖ Ageing Grid infrastructure is a key attribution.
❖ Congestion in the distribution networks.
❖ Mvar support mainly in distribution grids.
The level of energy storage required in the UK’s future energy system is
currently unclear
UK Grid situation – Developments (2/2)
Local UK system operator NESO, in specific:
(1) introduced multiple reforms to “new grid services”,
(2) launched Innovative projects (Pathfinder) across UK, to address the key power systems issues
Under the Network Options Assessment (NOA) released by NG-
ESO 3 areas have been identified for Pathfinder projects to
solve specific problems in the system:
1. NOA High voltage Pathfinder: finding solutions to regional
high voltage issues.
2. NOA Stability Pathfinder: Addressing NG-ESO’s
immediate needs of national inertia, and local short circuit
level needs in Scotland.
3. NOA Constraint management Pathfinder: Resolving
network constraint issues and lowering balancing costs.
Stability projects are completed, BESS with GFM capability
plays a key role here in stability projects;
Opportunities for BESS in other two pathfinder projects..
UK and in specific NESO – are unique, during the energy transition, using “different innovation models” to try out new
technologies to support the ageing UK grids integrated with >90% already renewable resources.
How did BESS help on 22nd December 2023:
when France- UK Interconnector tripped? (1 /2)
➢ via Dynamic Containment
(DC) 873MW of Power is fed to
the grid to bring the freq. above
49.5Hz.
➢ This power was injected
under 10 seconds.
(1) At the time of trip, system inertia was already lower, therefore, the tripping resulted in faster degradation of frequency.
(2) The grid frequency went down to 49.3Hz, quickly.
Frequency responses in the UK following a
disturbance (2 /2)
2 new reserve services:
The near real-time reaction. It kicks in quickly to slow down the
effects of a disturbance on the grid. It has 2 main arsenals:
(1) Quick reserve: the near real-time reaction. It kicks in
quickly to slow down the effects of a disturbance on the grid.
This is provided from frequency service but will be combined
with Dynamic Regulation (Batteries can provide this services,
as they can provide a near- instantaneous response in both
directions.)
(2) Slow Reserve : a slower solution. It provides a longer-term
fix to the underlying problem and brings frequency back
into operational limits. This service is used from the capacity
services but will be combined with Dynamic containment. The
slower, longer requirement opens this service for much wider
participants. (Batteries will be able to provide with slower ramp
With Dynamic (containment, moderation and regulation) services now evolving requirements.)
Enduring Platform launched to provide new services as well as host existing
in October 2023, NG-ESO, UK
Different applications, same requirements: Developer &
Grid side
POWER (Fast Reaction) ENERGY (multi hour storage)
0.5h 1h 1.5h 2h 3h 4h 6h
Frequency regulation Secondary reserve and other grid
Main use
Inject / Absorb active power to services Grid needs
stabilize grids Inject / Absorb active power to stabilize grids on long
Frequency.services
patern
Frequency.services
Energy arbitrage Solar / wind shifting
Buy electricity when prices Defer midday or night surplus or curtailed Developer
are low, sell it when prices production to morning/evening peak demand economics
are high Operational mgmt.services
Capacity Mechanism Capacity Mechanism USA
Capacity mechanism in the US has
AOLT Operational mgmt.services different duration requirements from
Grid needs
Capacity mechanism in France, 4h to 8h depending on the location
tailored for Frequency regulation Operational mgmt.services
BESS
1.5h 2h 3h 4h 6h
Projects by
0.5h 1h
Island France Texas Hawaii Belgium** Australia RSA
Value Drivers and remuneration – due to BESS
Category Service(s) Value (example) Rémunération type (Merchant / Regulated)
(1) Re-dispatch avoidance • 86k€/MW/yr (D) 1. Congestion mgmt. (GOPACS, Nederland),
Grid investment deferral • 100k£/MW/yr (UK) Distribution - Merchant
2. Grid Booster, Transmission - Regulated
(2) Curtailment avoidance • 30 k€/MW/yr (D) 1. Arbitrage (Trading) - Merchant
Operational 2. Local flexibility markets (UK, F, AUS) – Regulated
Management or Merchant
(3) Capacity • 29k€/MW/yr (F-AOLT) 1. Multi-year capacity contracts based on auctions Key takeaways:
• 12k£/MW/yr (UK,2023) 2. ECRS, Texas – for operational issues. Merchant
❖ To recover the life cycle costs,
(4) Investment deferral/ upgrade deferral • 5bn€/yr DistrGrids (EU) optimised value stacking of
(1) Balancing or regulation = Primary, • 50k€/MW/yr FCR (F) 1. Continental EU -Regelleistung, Picasso, Mari, - services.
secondary, tertiary frequency services Merchant
2. Local flexibility markets (UK, F) - Merchant ❖ A combination of long-term
3. Local balancing markets (UK) - Merchant contracts, day ahead or spot -
will drive the future of the market
(2) Synthetic inertia Market still evolving: 1. Dynamic containment, UK mechanism.
Frequency • spot market in Australia, 2. Dynamic Regulation, UK
• long term contracts? 3. Dynamic Moderation, UK ❖ Investors of BESS projects, may
• 200k£/MW/yr (DC-UK) 4. FCAS, Australia want to maintain a balance of
5. ERCOT, Texas – services are evolving looking for “Life-cycle costs
recovery” and “long-term
(3) Reserve services (non-spinning) • Now evolving in UK, 1. Quick and slow reserves - UK contracts”.
Australia, Ireland.
VAR services: • Normally, at the local « Bonus » for specified BESS features - Regulated
1. Power factor correction in level.
Voltage DIstribution.
2. Line-Loss compensation in
Transmission.
Restoration of Black-start • At the ocal need « Bonus » for specified BESS features – Regulated
Supply
New services are constantly evolving (& favourable for BESS) – like in UK and Australia!!!
Grid “Flexibility” Resources- today and tomorrow
Multiple ancillary services provided by multiple resources Multiple ancillary services provided by single resource
Even better :
Step#1: Main1, Main 2 resource philosophy with
different manufacturers of same technology.
Step#2: Main1, Main 2 resource philosophy with
different manufacturers and different technology.
Multiple Use cases at the Grid (Tx, sub-Tx substation) ….
Use case #1 Use case #2 Use case #3
“Loop-in & Loop-out (LILO) and to “Avoidance Generation 1) N-1 Contingency,
charge / discharge BESS Curtailment” 2) reducing redispatch
cost
Depending on the RTO, BESS can be used
either as regulated (SATOA) or allowed to
Tr.fr also participate in merchant (SATA) market.
Tr.fr Tr.fr Tr.fr
Local Local BUSBAR Local
S/s S/s S/s
BUSBAR BUSBAR
BESS
200 MW,
200 MWh
Charging
BESS BESS
50 MW,
50 - 250MWh G 100 MW,
200 MWh F
Dis-charging
Charging Charging
Remote
BESS
200 MW,
S/s 200 MWh Remote
S/s
BUSBAR BUSBAR
BUSBAR BUSBAR
Remote Remote
S/s -1 S/s -2 Breaker close
Breaker open S/s - Substation
