The cost of balancing a parabolic trough concentrated solar power plant in the Spanish electricity spot markets

This study presents a new dispatch model (SCSP) for a CSP plant based on a dynamic programing algorithm. The purpose is to investigate the cost of balancing a CSP plant in the Spanish electricity market. Results are presented for a parabolic plant in the Spanish market for years 2009, 2010 and 2011 using solar availability data at the Plataforma Solar, Andalucia, Spain. The variation of balancing cost with solar multiple (SM) and number of storage hours (Nh) is analysed and results for two different optimisation cases presented. The first uses day-ahead forecasts for both solar availability and market prices. The second uses day-ahead solar availability and within-day market price forecasts. Both cases are settled in the balancing market. Key results include that the balancing cost decreases with increased SM and Nh and that balancing costs can be 2.2% to 9.5% of the plants gross income. For all SM and Nh, balancing costs are a function of season, being lower in summer than winter driven by increased load-factor in summer. During the year Quarter 3 has a lower balancing cost than Quarter 2 due to a closer match between forecast and actual solar availability. Optimising against within-day prices costs more than with day-ahead prices resulting from more balancing energy traded at a less favourable price than day-ahead. It is envisaged that the numbers presented in this study will provide an aid to policy makers when constructing tariffs to support future CSP development.