The document discusses various energy storage technologies for renewable energy systems. It describes how storage is needed to deal with the intermittent nature of renewable sources like solar and wind. It then examines different storage options like pumped hydro, batteries, flywheels, compressed air and thermal storage. Each technology is described in terms of its workings, advantages and disadvantages. The document concludes that reliable and affordable energy storage will be key to increasing the use of renewable energy in the future.

1. Planning & Operating
Electricity Network with
Renewable Generation

2. ENERGY STORAGE TECHNOLOGIES FOR
INTERMITTENT RENEWABLE ENERGY
SYSTEMS

3. Contents
• Introduction
• Background of storage system
• Different energy storage technology
• Comparison of different storage technology
• Conclusion

4. INTRODUCTION
• What is energy storage system for renewable
energy ?
• Why is it required ?
• Function of energy storage system

5. Background of storage system
Storage is an essential unit that stores unstable electric
energy during wind and photovoltaic power
generation, which is sharply growing new renewable
energy, and supplies the unstable energy to electric
power system again in necessary moment. If there is
no such energy storage unit, any kinds of serious
problems like sudden blackout occurs because of
unstable sunlight-dependent electricity supply. This
Storage takes an important part in the electricity
storage systems for households, the medium-size
system for industrial/commercial use, and the extra-
large system for power plants and substations like
Frequency Regulations

7. Importance of ESS...
• Thrust for Renewable Energy sources
• Variable outputs
• Energy Buffering
• Importance in the present context
• Why new technologies and devices?

8. Different Types of ESS…
ESS can be classified as
• Mechanical Energy Storage.
• Magnetic Energy Storage.
• Thermal Energy Storage.
• Chemical Energy Storage.

9. Mechanical Energy Storage
Fly Wheels
• Principle: Energy is
stored in the form of
Mechanical Energy.
• Light weight fiber
composite materials are
used to increase
efficiency.
• Energy density
=0.05MJ/Kg, η=0.8

10. • The Energy Density is defined as the Energy per unit
mass:
• Where,
V is the circular velocity of the flywheel
σ is the specific strength of a material
ρ is the density of the material
2E 1
V
m 2

 


11. Properties of some materials used for building flywheels.

12. Advantages and disadvantages:
• Very compact when compared to other energy
storage systems.
• Flywheels are used for starting and braking
locomotives.
• A flywheel is preferred due to light weight and
high energy capacity.
• It is not economical as it had a limited amount
of charge/discharge cycle.

13. Compressed Air Energy Storage

14. Operation:
• Uses off-peak electricity to compress air and
store it in airtight underground caverns.
• When the air is released from storage, it expands
through a combustion turbine to create
electricity.
• Energy density = 0.2~2 MJ/Kg, η=0.5
Advantages and disadvantages:
• Fast start-up.
• Draw back - Geological structure reliance

15. Pumped Hydroelectric Energy Storage

16. Operation:
• It consists of two large reservoirs located at
different elevations.
• During peak demand, water is released from
the upper reservoir.
• If Production exceeds Demand, water is
pumped up and stored in the upper reservoir.
• Pump used is a Combined Motor and Dynamo.

17. Advantages and disadvantages:
• Most effective with largest capacity of
electricity (over 2000 MW).
• Energy density = 0.001MJ/Kg, η=0.8
• Geographical dependence.
• The capital cost is massive.
• Soil erosion, land inundation, Silting of dams.

18. Magnetic Energy Storage
Super Conductors

19. • SMES systems store energy in a magnetic field
created by the flow of direct current in a coil of
superconducting material that has been
cryogenically cooled.
• Principle: At low-temperatures, electric
currents encounter almost no resistance.
• Stores energy in the magnetic field.
• Environmental friendly and Highly efficient.

20. Depending on the peak field and ratio of the coil's height and
diameter capacity of storage varies.

21. Super Capacitors
• Use of thin film polymers for
the dielectric layer
• Carbon nanotubes and
polymers are practical for
super capacitors
• In future - carbon nanotubes
with ceramics
• Reduce the effect of
fluctuations
• Longer life time which reduces
maintenance
costs.

22. Electrochemical Storage
Types of Batteries:
– Small Capacities
– Lead-Acid Batteries
• They use a chemical reaction to do work on charge and
produce a voltage between their output terminals.
• Energy density is 0.6 MJ/Kg.
• Efficiency of the cell is only 15%
– Large Scale

23. Working of a Lead acid Battery

26. Under-Ground Thermal Energy Storage
• Using methods of heat exchange
1. Aquifer thermal storage
- Usage of underground water
2. Duct thermal storage
- Usage of Plastic Tubes
• Environmental impact
Eg: De-ice frozen roads

28. Application of Thermal Energy Storage
Air Conditioning:
• A salt hydrate acts as a cool heat sink for the
air conditioner working fluid.
• The stored heat is rejected from the salt
hydrate during night to heat the surrounding
air.
• Energy density = 0.25MJ/Kg, η=0.8
• E.g.: Sodium Sulfate Decahydrate.

29. Fuel Cells
• Direct conversion
EnergyElectricity
• Burning Fuel?
• High Efficiency
• Applications:
E.g.: NASA, Viable
alternative to petrol
engines.

30. Types of fuel cells:
Classified on the basis of operating conditions
and various electrolytes used.
– Alkaline fuel cells (AFC)
– Polymer electrolyte membrane (PEM)
– Phosphoric acid fuel cells (PAFC)
– Molten carbonate fuel cells (MCFC)
– Solid oxide fuel cells (SOFC)
– Regenerative fuel cells

31. Energy densities of some energy storage methods.

32. Advantages:
• No green house gases
• Not much political dependence
• More operating time.
Disadvantages:
• Storage of Hydrogen due to highly inflammable
nature of H2. Though metal hydrides(FeTiH1.7) and
NH3 can be alternative.
• High capital cost due to Platinum catalyst used in the
process.

33. Which is better
???
 Comparing one method of energy storage with another
is pointless.
 The reason - None of them are optimal for all purposes.
 Different storage methods differ in capacity and
maximum usable storage time.

34.  For large scale storage Underground thermal,
pumped hydro and compressed air energy storage
systems are preferable.
 Superconductors can store energy with negligible
losses.
 Fuel cells are a viable alternative to petrol engines
due to their high efficiency.
 Flywheels have a narrow range and are not an answer
for large scale operations.

35. Conclusion:
• Reliable and affordable energy storage is a
prerequisite for using renewable energy.
• Energy storage therefore has a pivotal role in
the future.
• Energy storage is the most promising
technology currently available to meet the
ever increasing demand for energy.

36. DIFFERENT ENERGY STORAGE
TECHNOLOGIES
• Pumped storage
• Batteries
• Superconducting magnet energy storage
• Flywheel energy storage
• Regenerative fuel cell storage
• Compressed air energy storage

37. Pumped storage
• A pumped storage hydro power plant
may store huge energy by pumping
water from a lower reservoir to a higher
pond. In a pumped storage hydro plant,
we usually make the height of the
reservoir equal to a small hill and at
bottom a cavity is made so that water
may not run away downward.
• Water is pumped during off-peak times
and may be utilized to generate
electricity. Other innovations may store
electricity in small quantity but pumped
storage hydro power plant may store
electricity in Megawatts (MW) or even
Gigawatts(GW).

38. Batteries
Battery Bank
Battery
Battery working

39. Flywheel energy storage
• Flywheel energy storage systems are one of
energy storage devices. They store energy
mechanically in the flywheel rotor by rotating
the rotor while as chemical batteries stores
energy electrically. When we want to use the
stored energy in the rotor, a generator is used
to convert mechanical energy to electrical
energy.
• Flywheel systems are not sensitive to
temperature since they are operating in a
vacuum containment. Therefore, the hybrid
vehicle with flywheel systems can run without
any problem at very cold or hot areas. And,
flywheel systems can store more energy per
system weight compared to chemical batteries,
• The flywheel system is a very efficient energy
storage device, it can be used for various
applications.

40. Superconducting magnet energy storage
Superconducting magnetic energy storage
systems store energy in the magnetic field
created by the flow of direct current in a
superconducting coil. This advanced systems
store energy within a magnet and release it
within a fraction of a cycle.

41. Regenerative fuel cell storage
• A fuel cell is an electrochemical cell that
converts a source fuel (from combustible
substances such as hydrogen, methane,
propane, and methanol) into an electric
current.
• A fuel cell is a device that generates
electricity by a chemical reaction. Every fuel
cell has two electrodes, one positive and
one negative, called, respectively, the anode
and cathode. The reactions that produce
electricity take place at the electrodes.
• Hydrogen is the basic fuel, but fuel cells also
require oxygen. One great appeal of fuel
cells is that they generate electricity with
very little pollution—much of the hydrogen
and oxygen used in generating electricity
ultimately combine to form a harmless
byproduct, namely water.
•

42. Compressed air energy storage
continue…
•Energy from solar or wind and even
electricity from thermal power plant during
off-peak period may be utilized to compress
air by compressor and same air may be
utilized to produce electricity during peak-
hour.
•Compressed air energy storage is done in
underground caverns and abandoned
mines.

43. Mapping Storage Technologies

44. Advanced Lead Acid
Lead-Acid batteries consist of two
electrodes: Lead and lead-dioxide
immersed in sulfuric acid.
Lead Acid
Performance
measure
Cycle Life Energy
Efficiency (%)
Market leader 1200 80
Best in class 2000 85

45. Sodium based battery - NAS
Sodium-sulfur (NaS) batteries use molten
sodium and sulfur electrodes separated
by a ceramic electrolyte
Sodium Based
Performance
measure
Cycle
Life
Energy
Efficiency
(%)
Market leader 4000 70
Best in class 6000 85

46. Li-ion Battery Technology
Li-ion battery uses graphite as the anode
material and LiFePO4 or LiCoO2 or Lithium
titanate or lithium nickel manganese
cobaltate as the cathode.
Li-Ion Batteries
Performance
measure
Cycle Life Energy
Efficiency
(%)
Market leader 2000 90
Best in class 10,000+ 95

47. Flow Battery Technology
Flow batteries use liquid electrolytes with fixed cells to store and regenerate power. Various flow
battery chemistries exist such as vanadium redox, zinc-bromine, iron - chromium etc.
Flow Batteries
Performance
measure
Cycle Life Energy
Efficiency (%)
Market leader 5000 60
Best in class 10,000+ 70

48. Typical System Configuration for Identified Applications
Segments / Applications Sub Segments Power Rating Duration DOD
Type of
cycles
No of cycles /
Year
Renewable Energy
Integration
Wind Smoothing
1 MW- 20 MW
15 min - 1
h <60% Shallow <18,000
Wind Firming 1 MW-20 MW 4-6 h >80% Deep <500
Solar 3 KW-2 MW 3-6 h >80% Deep <350
Load shifting or energy
arbitrage
Commercial 10 KW - 2 MW 2-4 h >80% Mix <400
Industrial 500 KW - 5 MW 2-4 h >80% Mix <400
Off grid applications
Rural Microgrid
(households) 1KW - 5 kW 2-8 h >80% Mix <400
Rural Schools / Hospitals
1 KW - 10 kW 2-8 h >80% Mix <400
Replacement of DG
Telecom Towers 2 KW - 5 kW 2-4 h >80% Mix <700
Commercial 10 KW - 2 MW 2-4 h >80% Mix <400
Industrial 500 KW - 5 MW 2-4 h >80% Mix <400
Transmission or
Distribution Deferral
Utilities
1-20 MW 4-6 h >80% Mix <100
Frequency support Utilities / IPP
1 MW- 20 MW
15 min – 1
h <60% Shallow <18,000
Reactive Power
Management
Utility / C&I 3 KW - 10 MW
15 min – 1
h
N.A. N.A. N.A.
Please note that some applications require very high number of cycles but are very shallow discharges.

49. Energy Storage Landscape
2015

50. Energy Storage Performance Matrix
ENERGY STORAGE performance
metrics:
• Capital cost ($/kWh)
• Cycle life
• Roundtrip Energy Efficiency
• Space footprint
• C-rate (duration)
• Usable SOC range
Lead Acid batteries are work
horse for the industrial and
residential backup and provide
lower capital cost solutions.
Li-Ion has emerged as the
technology of choice for short
duration applications & Flow
batteries are vying for a position
for longer duration applications.

51. Key Trends in Energy Storage
51

52. Cost reduction in per Cycle Capital Costs

53. Conclusion Energy storage technologies are rapidly gaining adoption for variety of grid
applications in recent years.
 Pumped Hydro, Thermal Storage and Lead Acid batteries have been used for
grid support and back up applications for 100+ years
 In recent years, Li-Ion batteries are gaining rapid adoption for short duration
applications, and reduction is prices and improvements in performance is also
enabling use for applications such as peak load management, renewable
integration and diesel reduction.
 Advanced Lead Acid and Flow batteries also have promise for significant
improvements and enabling newer applications in next 3-5 years.
 Regulatory intervention & Business Model innovation is expected to drive large
scale adoption of energy storage in next 2-3 years.
53

54. Contact US
54
Customized Energy Solutions India Pvt. Ltd.
A 501, GO Square
Aundh - Hinjewadi Link Rd, Wakad
Pune, Maharashtra 411057 India
Phone: 91-20-32407682
info@ces-ltd.com
Customized Energy Solutions Ltd.
1528 Walnut Street, 22nd Floor
Philadelphia, PA 19102 USA
Phone: +1-215-875-9440
Fax: +1-215-875-9490
info@ces-ltd.com
Dr. Rahul Walawalkar
Executive Director,
India Energy Storage Alliance
rahul@ces-ltd.com
US Cell: +1-516-639-5391
India Cell: +950-303-1765