1. The amount of electricity produced must always be on the same level as demanded!  Base Load  Intermediate Load  Peak Load Source : http :// www.world-nuclear.org/info/inf10.html

2. Intermittent Wind Supply Wind is not a controllable energy source, it is either blowing or it isn’t and this power is distributed to the electricity grid regardless of whether it is needed or not. The grid cannot store energy so power plants have to match the demand in real time. Often several power plants will operate in ‘Spinning Reserve’ mode during periods of high wind output to cater for the inevitable drop in wind. www.inference.phy.cam.ac.uk/withouthotair/c26/page_187.shtml Yearly, Bi-Monthly & Monthly Wind Output (MW)

3. Typical 7 day Winter Demand profile (Saturday/Sunday generally lowest) Wind Output for same time period has no correlation to demand Issues with excess wind generation between 12.30 AM – 6AM Source: Eirgrid

4. Most renewable energy sources have a fluctuating output. Need for storage solutions! Source: http://michaelwenzl.de/wiki/ee:virtuelles-kraftwerk-lechfeld:vortrag_gruene

5. Energy storage can facilitate renewable energy integration Source: http://www.environment-green.com Source: http://technorati.com/ Source: http://www.celgard.com/ 5

6. Introduction to Storage Energy storage is the conversion of energy to other forms so that it may be used at a later stage when required. Industrial scale energy storage technologies are measured in terms of their power output (MW) and their capacity (MWh). The most common type of energy storage is ‘Spinning Reserve’ where power plants operate at a level slightly below the point where they begin to produce power. This allows them to react quickly to large swings in demand. The spinning reserve is the extra generating capacity that is available by increasing the power output of generators that are already connected to the power system. For most generators, this increase in power output is achieved by increasing the torque applied to the turbine's rotor.

7. Key energy storage research areas include: Technology-specific issues – Mechanical storage – Electrical storage – Thermal storage 7

8. Mechanical storage options include: Compressed air energy storage (CAES) Pumped hydroelectric storage Flywheels 8

9. CAES can enable wind to supply quick, reliable energy Source: http://www.shpegs.org/cawegs.html 9

10. CAES has been operating for over 20 years: Huntorf, Germany: 290 MW (1978) McIntosh, Alabama: 110 MW (1991) Iowa Stored Energy Park: 2700 MW (2011) 10

11. CAES has many benefits for renewables Large storage: smoothes daily variability Ramps quickly: smoothes hourly variability More cost-effective that batteries at GWh scale Many locations with suitable geology in U.S. Key research area: The economic effect of integrating CAES in different electricity markets and varying levels of renewable energy penetration 11

12. CAES plants store energy in form of compressed air in underground caverns. The Advanced Adiabatic (AA) CAES stores the heat produced during the compression and compensates the freezing during the expansion. Source: http://www.climateandfuel.com/pages/storage.htm

14. Considerably large storage opportunities exist worldwide. Source: http://web.fhnw.ch/plattformen/ee/CAS%20EE%2009%20ZA%20Druckluftspeicher.pdf

15. Pumped Storage Hydroelectricity (PSH) In an PSH electrical powered turbines pump water into higher reservoirs. When needed, the water flows back down and power the reversed turbines. Source: http://www.bbc.co.uk/scotland/learning/bitesize/ standard/physics/energy_matters/generation_of_electricity_rev3.shtml

16. Pumped hydro is limited by location Source: http://www.tva.gov/power/pumpstorart.htm Key research area: Run-of-river hydro storage (all aspects) 16

17. 2.4Pumped Storage Hydroelectricity (PSH)

18. Storage Technologies – Flywheel Energy Storage Flywheels are mechanical devices which accelerate a rotor to a very high speed, storing the energy as rotational energy. These devices are most suitable for high utilization applications as their efficiency decreases in proportion to their use. Suitable for short term lulls in wind generation output (1-5min) Rated for > 100,000 cycles Used in F1 racing cars (0.1kWh, 4.6Wh/kg) http://www.upei.ca/~physics/p261/projects/flywheel2/flywheel2.htm

19. Flywheels can help with grid angular stability and voltage support Produce 100-2000 kW for 5- 50 seconds Best for high-power, low energy applications Source: http://www.powergenworldwide.com/ Key research areas: Materials development Cost reduction Improved manufacture techniques 19

20. Flywheels store energy in form of kinetic energy in a rotating hub. Source: http://www.acsystems.com/vycon/

22. Key energy storage research areas include: Technology-specific issues – Mechanical storage – Electrical storage – Thermal storage 22

23. Batteries Batteries store energy in chemical form. Most battery technologies use two different compounds which release energy in form of an electrical current when reacting with each other. Source: http://www.wholesale-electrical-electronics.com/p-solar-battery- np12-200ah-12v-200ah-855419.html

24. Batteries are wonderful for renewables, but expensive Store and release power across a broad range of time scales Smooth rapid fluctuations Mitigate daily variability Key research areas: Large-scale demonstration projects Cost reduction Source: http://www.greencarreports.com/blog/ 24

26. Storage Technologies – Flow Batteries Flow Batteries allow energy to be stored in two solutions existing at different electrochemical potentials. All the energy is stored in the electrolyte solutions so that the capacity is determined by the size of the electrolyte tanks The system power is determined by the size of the fuel cell stacks which can be arranged in series/parallel as required. Suitable for daily lulls in wind generation output (< 12hours) Rated for > 10,000 Cycles http://www.netpowertech.com/e_menu_page.aspx?bid=4&id=10

27. Plug-in hybrid electric vehicles could act as distributed grid storage Source: http://keetsa.com/ 27 Daily load leveling Frequency regulation Reserve Large-scale use: reduce battery costs through competition and mass production Key research areas: Quantify the public and private benefit of using PHEV’s for arbitrage Identify policy incentives necessary to align consumer behavior with maximum social welfare

28. Superconducting Magnetic Energy Storage A SMES system stores energy in form of an electromagnetic field surrounding the coil. Source: http://www.lowcarbonfutures.org/assets/ media/SMES_final.pdf

30. Electrolysis of Water and Methanation Excess Electricity could be used to produce hydrogen and methane out of water and inject it into the natural gas grid.

31. Electrolysis of Water and Methanation The natural gas grid in Germany alone holds the potential of storing approximately 220 TWh. ( cf. current PSH share: 0,07 TWh )

32. Electrolysis of Water and Methanation

33. Key energy storage research areas include: Technology-specific issues – Mechanical storage – Electrical storage – Thermal storage 33

34. Thermal storage can be hot or cold Source: http://www.kelcroft.com.hk/news/ice_storage2004103 0.htm Source: http://www.tehrantimes.com/index_View.asp?code=20 1948 34

35. Demand-side “hot” storage is usually used with solar collectors Store heat energy in hot water for later use Reduce electricity demand for hot water Source: http://www.conservationhalton.on.ca/uploads/solar%20water %20heating.gif Key research areas: Quantify potential decrease in electricity demand from wide-spread use Determine optimum system size for max economic returns ID policy initiatives to encourage more deployment 35

36. A “cold” storage system generates ice to chill water for air conditioning Shift electricity demand for air conditioning from day to night Key research areas: Quantify potential shift in electricity demand from wide-spread use Determine optimum system size for max economic returns ID policy initiatives to encourage more deployment 36 Source: http://www.solarthermalmagazine.com/2010/04/1 2/storing-thermal-energy-a-cool-new-way/

37. On the supply-side, storage is usually coupled with CSP Source: http://www.volker-quaschning.de/articles/fundamentals2/index.php 37

38. CSP-TES has been operating commercially for 2 years Smoothes hourly variation from clouds Extends plant operation into nighttime peak demand hours Source: http://www.scientificamerican.com/article.cfm?id=how-to- use-solar-energy-at-night Andasol 1 in Spain: 50 MW (2008) Key research areas: Reduce costs Quantify long-term effect of TES in CSP O&M costs Evaluate the profitability of different configurations Evaluate the effect of different policy initiatives on decision to use TES with CSP Compare economic & environmental implications of TES for different CSP technologies 38