• Energy Research

Abstract We formulate the concept of a multi-functional energy system, called storage plant, as a possible solution to cover the variable residual load that appears in most countries after introducing renewables in the power sector. A storage plant consists of a photovoltaic power plant, a heat storage system with electric heater to transform solar power, a steam power cycle to convert stored heat to dispatchable power, a backup heating unit for the storage based on the combustion of biomass or other renewable hydrocarbons, and a gas turbine with waste heat recovery for peak loads. After explaining the storage plant concept, the paper describes a simulation model of the German power sector and its transformation from the year 2020 with roughly 40% renewable electricity share to 2040 with a hypothetic 90% renewable electricity share. Multi-indicator benchmarking over that period shows that storage plants can have a key role to achieve emission goals and at the same time sustain full supply security within the German power sector.

The capacity of a concentrating solar thermal power (CSP) plant can be considered flexible and firm, just like that of a conventional steam cycle power station. Periods without sunshine can be bridged by thermal energy storage or fuel, enabling a CSP plant to deliver power on demand at any time. To this technical quality is added the economic quality of electricity costs that will be stable for a lifetime because they are mainly composed of capital costs, spare parts and personnel. CSP is competitive with power from fuel oil and moving to break even in costs with natural gas by around 2020 and steam coal by around 2025. Carbon dioxide emissions of 10–40 tons/GWh, land use of 250–550 m²/GWh and water consumption of 250 m³/GWh (using dry cooling) compare favorably with other energy sources. Environmental benefits, the technical imperative of firm and at the same time flexible power supply, and the economic targets of affordability and cost stability are the main reasons for a significant role for CSP in a sustainable future electricity mix. Two case studies show the different roles CSP can play north and south of the Mediterranean Sea, in one case importing CSP to Germany for flexible power and in the second case using CSP in Jordan to provide firm and at the same time renewable power capacity for the quickly growing electricity demand.