CPV-connected ES for Multiple Services

Sammanfattning: In this master thesis, the topic of energy storage connected to concentrator photovoltaic power production is assessed. The end goal is to propose the optimal energy storage technology and its sizing, regarding power and energy capacity, for an existing concentrator photovoltaic power plant. The plant is located in the province of Algarve in Portugal, the installed production capacity is 4.5 MW, and the average annual electric energy produced is 7 200 MWh. Services chosen to be provided by the energy storage, in falling priority, are ramping support, peak shaving and arbitrage. The energy storage system will pose as a demonstration project, contributing with knowledge to the field and promoting investment in novel energy technology. Also, as the penetration of intermittent renewable energy sources are expected to increase over the coming decades, the demand for services provided by energy storage systems will grow. To reach the objective of technology and sizing selection, a literature study combined with computer-aided simulations has been carried out. Also, an economic analysis of relevant technologies has been performed to help selecting the wisest option. For the simulations, measurements of direct normal irradiation have been used to calculate minute-by-minute power outputs. The validity of the calculated output was confirmed through comparison with real output data from the solar platform. It was found that an energy storage based on the sodium-sulphur technology would be the preferred alternative. The proposed sizing was set at a rated power of 2.75 MW and an energy capacity of 1 MWh. With these characteristics, more than 98 % of the simulated extreme ramping events (changes in output over 10 % of installed capacity per minute) would be covered for. A general conclusion from the analysis is that to provide the service of ramping support, a rather high power rating is needed, while the required energy capacity is small. This means that out of the three chosen services, ramping support is the one dimensioning for the rated power. On the contrary, peak shaving and arbitrage are energy capacity intensive, thus, they are the dimensioning services for the energy parameter. It was also found that the arbitrage service, with the chosen energy storage dimensions, resulted in very limited gains in revenue. However, when the service is combined with peak shaving, it can instead be seen as a strategy to minimize losses in revenue. Regarding technologies, it was early concluded that a mature option of battery energy storage was going to be chosen for our case. The sodium-sulphur technology was found to excel, from an economical standpoint, in cases where the required energy capacity is rather large. The lithium ion technology on the other hand is preferred when this dimension is kept small. A lead-acid battery was found problematic to combine with the services of peak shaving and arbitrage because of its limited ability to be fully discharged.