| For small, remote villages in developing countries, local stand-alone power systems are often more cost-effective than utility grid extension. Various combinations of wind turbine generators, photovoltaic arrays, diesel gensets, and batteries--Remote Hybrid Power Systems--may be environmentally, economically, and aesthetically preferable to diesel-only systems. One of the design issues in such systems is dispatch strategy: the aspect of control strategy that pertains to the sources and destinations of energy flows. In systems with both batteries and diesel genset(s), dispatch strategy impacts long-term fuel usage as well as battery life. The existing energy performance models offer limited choices of component configuration and of dispatch strategy, and therefore limited ability to determine optimal system designs.; This research consists of two phases: (1) Model development. In conjunction with Manwell et al. at the University of Massachusetts, new public domain software (HYBRID2) with a unique capability to compare various system configurations and dispatch strategies with a high degree of accuracy is proposed and developed in this dissertation. (2) Dispatch optimization. For the case of wind/diesel/battery systems with hour-to-hour energy storage, various dispatch strategies are compared on the basis of life-cycle costs, including diesel fuel, diesel startup, and battery replacement costs. An idealized predictive dispatch strategy, based on assumed perfect knowledge of future load and wind conditions, is developed and modeled for use as a benchmark in evaluating simple, realistic, nonpredictive strategies. It is shown that the proper choice of two simple diesel operating strategies--either load-following or full-power for a minimum run time--can, in conjunction with the frugal use of stored energy, be virtually as cost-effective as the ideal predictive strategy. The optimal choice of these two simple strategies is correlated to three dimensionless parameters, yielding a generalized dispatch design chart for this type of system. The same general principles will apply to photovoltaic/battery/diesel systems, although the design chart has not been correlated for such systems. |
