Energy_Storage_Technologies.pdf

System design considerations the efficiency of these

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System Design Considerations The efficiency of these systems are typically limited most by the efficiency of the pump and turbine [3], although the friction of the water in pipes is another factor. Some of the water will be lost due to evaporation, and this may be considered self-discharge, but similarly, rainfall will help to offset this effect. Operation & Maintenance The O&M required for this system would be minimal, as these designs are well- understood and have been around for many years. Routine maintenance of the generator and turbine, and cleaning the penstock if required would be expected tasks. Environmental Impact These systems have significant impacts on the local wildlife, especially if one or both of the reservoirs needs to be constructed. Also, the fluctuating water levels can significantly disrupt the inhabitants of the reservoirs. Other Resources A number of overviews of this technology exist including [8]. Summary of Device Parameters The following table summarizes the available technoeconomic parameters for PHS from a number of studies from 2000-2010. All monetary values have been adjusted to 2010 dollars. If a value is marked with “-” either the quantity was not found in the corresponding report or the way it was presented was inconsistent with the format used here. For example, the EPRI-DOE report gives total cost in $/kW or $/kWh, not a formulation that takes into account both, simultaneously. Source: Schoenung EPRI Gonzalez Schoenung Chen 2003 [5] 2003 [2] 2004 [3] 2008 [6] 2009 [7] Techno. Params. Roundtrip Efficiency [%] 75-78 - 70-85 - 72-85 Self-discharge [%Energy per day] - - - - very small Cycle Lifetime [cycles] - - - - - Expected Lifetime [Years] n/a - 30 - 40-60 Specific Energy [Wh/kg] - - - - 0.5-1.5 Specific Power [W/kg] - - - - - Energy Density [Wh/L] - - - - 0.5-1.5 Power Density [W/L] - - - - - Costs Power Cost [$/kW] 1190-1250 - 690 - 600-2000 Energy Cost [$/kWh] 12 - 0-23 - 5-100 PCS Cost [$/kW] n/a - 270-580 - - BOP Cost [$/kW] 4.8 - included - - O&M Fixed Cost [$/kW-y] 3.0 - 4.4 - - 11
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Energy Storage Technologies Compressed Air Energy Storage (CAES) 3.2 Compressed Air Energy Storage (CAES) In compressed air energy storage systems, off-peak grid power is used pump air underground until it reaches a high pressure. It remains inderground in a geologic formation until energy is needed, then it is released and heated, and passing through and turning a turbine, which generates power. CAES systems are essentially high-efficiency combustion turbine plants. In a standard gas turbine, air is compressed, mixed with fuel and combusted. That fluid is then passed through a turbine, which spins a generator producing energy and simultaneously provides the energy for compressing the air. Two-thirds of the energy provided by the fuel goes into compressing the air. So, in CAES systems, the air is already compressed, and therefore uses significantly less fuel. Because of their similarity to standard combustion turbine systems, they are easily integrable into existing power networks. With a ramp rate similar and slightly faster than traditional gas plants, these systems are ideal for meeting peak load.
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