Potential of Hybrid Wind Energy Systems for Utility System Applications

Wind energy is currently one of the most economically attractive renewable forms of bulk electrical generation, with over 2 billion kWh of energy produced during 1990 in California alone. However, in order to increase the value of wind energy to utilities, it is necessary to provide firm capacity during peak load periods. This paper investigates the technical and economic merits of several wind hybrid system configurations to meet this goal. A systems simulation model has been developed specifically for this study. The model includes hybrid configurations, using wind and Photovoltaics (PV) as the primary renewable energy sources combined with a natural-gas-fired combustion turbine (CT) and storage such as pumped hydro or batteries. A simple spread-sheet cost model is used to perform cost-of-energy (COE) analyses from the perspective of an independent power producer, who may be bidding on firm capacity. The model uses typical California seasonal and diurnal wind speed, and solar insolation distributions with corresponding utility load curves to estimate the COE for varying proportions of wind/PV capacity, the backup CT, and the storage system. A wind system without storage or CT backup is first analyzed as the baseline configuration. Results from a parametric study of a hybrid wind/CT generating station provide the COE estimates for stations with 0% to 100% CT backup for a range of fuel prices. In addition, pumped hydro and battery storage elements are modeled to determine their potential, improve profitability, and provide firm capacity. The intent is to identify practical hybrid configurations with the potential to profitably shift the intermittently generated energy to peak load periods in order to provide firm capacity. Results from a tradeoff study of the storage capacity provide a hybrid configuration with the best potential for profitability.