Wave spectra, wave conversion device performance, and integration into electricity markets

Electricity production from ocean waves has the theoretical advantages of higher capacity factor, lower short-term variability, and longer forecasting horizons, when compared to wind and photovoltaic sources. Potential applications of wave-generated energy, in light of these advantages, include: energy services; regulating reserves; and contingency reserves. To provide these services reliably and economically, the time variability of the wave energy resource must be clearly understood. Also, these services are provided in the context of real-time or day-ahead energy markets. The objective of this work is to assess whether the typical properties of wave energy converters, possibly enhanced with small amounts of energy storage, can result in energy products that have high value in these markets, providing highly reliable, constant power over predictable periods. We examine wave spectra from National Data Buoy Center buoys and convert them to representative time series. The wave time series are input to a generic wave converter model to generate output power characteristics. Some power takeoff devices inherently contain energy storage of small capacity; the smoothing effect of these is examined, along with larger amounts of storage. Finally the economic implications of variability and storage are calculated using recent, typical wholesale electricity prices. Investment in energy storage equivalent to 5 minutes´ worth of nameplate capacity is found to pay off in less than two years.