1. Comparing Large Scale Storage Technologies Tom Konrad, Ph.D. www.AltEnergyStocks.com Presented at Solar 2009 Buffalo, NY May 15, 2009

2. Outline Characteristics of Energy Storage Technologies Technology Options Technology Comparisons References

3. Characteristics of Energy Storage Capital Cost –Per stored kWh (Energy) –Per kW capacity (Power) Round-trip efficiency Standby losses Response time Cycle life Site-specific Constraints Commercialization Energy Density

4. Pumped Hydro (PHES) StrengthsWeaknessesApplications Commercial Response time Long life Good cost of energy Limited locations Costs vary w/ location Energy Arbitrage, Load following, Peak Shaving

5. Compressed Air Energy Storage Image Credit: CAES Development Company

6. Compressed Air Energy Storage (CAES) StrengthsWeaknessesApplications Commercial Response time Long life Cost of energy Cost of power Limited locations Requires fuel Energy arbitrage, load following, Peak shaving

7. Flow Batteries - VRB Diagram for VRB flow battery Credit: Wash University of St. Louis

8. Flow Batteries – Hydrogen Electrolyzer/Fuel Cell Image Credit: North Coast Weekly Journal

9. Flow Batteries (VRB, ZnBr, PSB, Hydrogen) StrengthsWeaknessesApplications Can be used anywhere, fast response time Some toxic, generally immobile Energy arbitrage, Load following, Voltage support, Frequency regulation Peak Shaving

10. Conventional Batteries (NaS, PbA, Li-Ion, NiMH) StrengthsWeaknessesApplications Commercial Modular Can be used anywhere Can be moved Cost, Short Cycle life, Standby losses T&D deferral, Peak shaving

11. Thermal Energy Storage Molten salt storage. Image Source: National Renewable Energy Laboratory Ice Storage: Image Source: Ice Energy

12. Thermal Energy Storage (TES) StrengthsWeaknessesApplications Commercial Round-Trip Efficiency Low Cost of Power Only with Thermal Generation (CSP) or Demand (HVAC) Peak shaving Energy Arbitrage Load Following (CSP only)

13. Long Distance Transmission StrengthsWeaknessesApplications Fully Commercial Very Inexpensive (relatively) Environmental NIMBY Regulatory Peak shaving Energy Arbitrage Load Following

14. Demand-Response

15. Smart Grid Image source: US Department of Energy

16. Demand Response & Smart Grid StrengthsWeaknessesApplications Commercial (DR) Power (Both) Energy (SG) No Standards (SG) Energy arbitrage, Peak shaving, Load Following, RE Integration

17. kWh vs. Efficiency

18. kW vs. Efficiency

19. Energy vs. Power

20. General References EPRI-DOE Handbook of Energy Storage for Transmission and Distribution Applications, 12/2003 EPRI-DOE Handbook Supplement of Energy Storage for Grid Connected Wind Generation Applications, 12/2004 An investigation into the energy storage technologies available, for the integration of alternative generation techniques, David Connolly, U. of Limerick, 11/2007 Solar Energy Grid Integration Systems – Energy Storage, Dan Ton, Sandia, 7/2008.

21. Technology Specific References Wind Integrated CAES in Colorado, B. Kelley + D. Kearney NREL 2004 PHES Utilizing Current Infrastructure in Colorado, Levine+Barnes 2007 Solar-Thermal based TES - Greg Glatzmaier, NREL, interview, 4/2009 VRB Power, website 800 kV HVDC – Alternative Scenarios for long distance bulk power transmission, Gunnar Asplund, ABB, 10/2008.

22. Thank You Tom Konrad, Ph.D www.AltEnergyStocks.com Tom@AltEnergyStocks.com