Generator Efficiency Improvement
This research project will strive to increase the efficiency of hydroelectric generators, thus allowing generation of more power with less water, by investigating the use of new techniques in generator efficiency. The primary focus will be on applying high-voltage generation and doubly fed (variable-speed) machines at Reclamation's powerplants.
Need and Benefit
Generator efficiency is directly related to conserving water and increasing power supplies. More efficient generators use less water to produce the same amount of power. They can also generate more power for the same amount of water. At least two emerging technologies show promise for increasing generator efficiency: high-voltage generation and doubly fed machines.
High-voltage generation produces power at power system voltages, thus reducing heating losses (less current) and eliminating the need for a step-up transformer (which has its own losses). The results are fewer overall electrical losses and more power delivered for the same amount of water flow. Eliminating the step-up transformer will also reduce the maintenance costs. Research in fiscal years (FY) 2002 and 2003 (2002 Reach for the Stars Award) led to a high-voltage generator pilot project at Folsom Powerplant. Continued research is needed into actual efficiency gains, winding testing methods, and condition monitoring. Data collected and analyzed will validate and extend previous research and answer many questions about further application of this technology.
Doubly fed machines can operate at variable speeds (rather than at only synchronous speed), and thus operate at the most efficient point on the torque-speed curve when the hydraulic head varies. For pump-generators, this has the effect of using less power to pump the same amount of water during the pumping portion of the pump-generation cycle. Power costs are reduced as well as pumping times, and wear and tear on the machine is less. Past research by Reclamation assisted the manufacturing community in producing prototypes of these machines, and it is appropriate that Reclamation investigate their applicability to our plants. Scoping research in FY 2003 indicated that the technology is likely viable and that additional research is needed to confirm and specify how it can be used. Mt. Elbert Pumped-Storage Powerplant is a prime candidate for conducting such research, due to the age and condition of the machines and the large variation in hydraulic head.
Generator efficiency improvements validated by this research could conservatively reach 2 percent. In the case of a 100-megawatt (MW) pump-generator, such as Mt. Elbert, operating 8 hours daily in generate mode, this could amount to over $290, 000 annually in energy gains with commensurate water savings. In pump mode, which requires 1.4 times as much energy to pump the water, energy savings would be over $400, 000 annually.
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