Energy storage can help integrate renewable energy sources by storing excess production for times when supply is low. However, current storage technologies are too expensive to deploy widely. Alternatives include improving demand management and allowing generators to better adjust output to changing demand. Further development is needed to reduce storage costs before it can be broadly implemented on power grids.

1. ENERGY STORAGE
Digajerla Suresh
M TECH-CTM
14CM43F

2. PRESENTATION STRUCTURE
• Why Do We Want Storage?
• Benefits of Storage
• Storage options
• Challenges for storage
• Alternatives

3. Data Sources for Today’s Presentation
• The Ontario generation (except for solar) and customer demand data was obtained from the
IESO website (http://www.ieso.ca). Detailed analysis was done in 2011 but load data for
2012 and 2013 has not changed much.
• Solar flux data comes from the Canadian Weather for Energy Calculations (CWEC) dataset
for Toronto, Environment Canada. Solar generation output simulations were produced
courtesy of Carbon Free Technology using PV system simulation software.
• Electricity production cost data was obtained from Ontario 2013 FIT rates and the Projected
Costs of Generating Electricity, 2010 Edition , Organization for Economic Co-operation and
Development, median case with carbon tax removed.
• www.eolien.qc.ca

4. DISADVANTAGES OF RE
• Diffuse Nature Of Renewables
Solar panels and wind turbines need to become cheaper
than raw fossil fuels.
• Intermittent Nature Of Renewables
Storage solutions need to become cheaper than fossil fuel
refineries (e.g. power plants).

5. COST COMPARISON
RENEWABLE ENERGY
• Deployment cost = $1.44/
W
• Lead Acid batteries = $
0.34 / kWh
• Li ion = $ 0.4/kWh
CONVENTIONAL
ENERGY
• Deployment cost = $
0.34/W
• Final cost per unit = $
0.06/kWh
• Fuel cost = $ 0.015/kWh
• Refining cost = $ 0.045
/kWh

7. Why do we want storage?
• Customer load varies significantly over time. The summer peak
is almost 250% higher than the spring low.
• Some generation technologies cannot adjust output to match
demand (limited ramp rates, minimum loads, etc.).
• Some generation technologies (wind and solar) are
intermittent and can change output very quickly opposite to
demand and can disappear for extended periods of time
across the province.
• Storage is an integrating technology – enables supply to
better match demand.

8. Benefits of storage
• Storage provides renewables with a zero GHG emission
backup.
• Storage can support voltage regulation and grid frequency
regulation.
• Storage reduces the amount of dispatching (load following)
imposed on generators (improves plant capacity factors)
• Storage reduces the natural gas plant capacity needed to
meet peak demand and reserves.
• Storage enables better utilization of base-load nuclear plants.
• Storage can reduce the required capacity of transmission and
distribution lines if it is located optimally

9. Storage Options
Short term storage:
• Batteries,
• Flywheels,
• Compressed air (tanks & underwater volumes).
• Dam and pumped hydroelectric (with small reservoirs – eg Niagara Pumped
Generating Station).
Longer term storage:
• Compressed air in underground caverns,
• Dam and pumped hydroelectric (with very large reservoirs – eg: Quebec’s James
Bay development).

14. Challenges- Solutions
• Large electrical demand variation increases the required
peak power rating of storage in kW and the integrated
capacity rating in kWh.
- Improved
demand management & load shifting
• Seasonal storage (shifting production from spring to
summer and autumn to winter) is the most valuable but
it is also the most expensive and environmentally
disruptive.
-Modifying flood
management systems Flood routing and storage in retention
basins

15. The Challenges for Storage
• Efficiency
All storage options lose some of the stored energy over
time (5 to 50% depending on technology and storage
duration).
• Hydroelectric storage Is the cheapest large scale storage but
you need ideal geography

16. The Challenges for Storage
• Cost is prohibitive – see 2010 EPRI Report 1020675
• Batteries: 1 to 5 k$/kW & 0.2 to 5.0 k$/kWh (short
life, 3 to 12 yrs)
• Flywheels: 2 k$/kW & 2 to 9 k$/kWh (10 hrs max
storage)
• Compressed Gas: 1 to 2 k$/kW & 0.1 to 0.5 k$/kWh
(low efficency)
• Pumped Hydro: 1 to 9 k$/kW & 0.2 to 0.9 k$/kWh
(uses large land areas)

17. Alternatives Without Storage
• Improved demand management
& load shifting
• Improved load following at
existing plants
• Surplus steam to district
industrial process steam system
• Produce hydrogen during off-peak
hours
• Export energy at below the
cost of production.
No energy is wasted with these
options.

18. Alternatives Without Storage
• Hydroelectric spill
• Dispatch Solar and wind
generation down
• Improve nuclear steam
bypass capability
Energy is wasted with these
options.

19. Summary
• Storage is an elegant solution.
• Much too expensive now to deploy on a large scale.
• Other non-storage options are available to manage
supply-demand balance until storage costs drop.