Choice of Solar Share of a Hybrid Power Plant of a Central Receiver System and a Biogas Plant in Dependency of the Geographical Latitude

Abstract

The potential of renewable energies varies significantly from North to South Europe. Southern Europe has a high solar potential and is ideal for the implementation of solar concentrated power plants. To this group of solar thermal power systems belong the solar tower, parabolic trough, solar dish and linear Fresnel systems. North European countries, especially the Scandinavian countries, have a high biomass and hydropower potential. This paper focuses on calculation of the power production for hybrid systems of solar tower with gas turbine in Southern Europe and biogas-only operation in Northern Europe. The solar tower system consists of a heliostat field, which concentrates direct solar irradiation on an open volumetric central receiver. The receiver heats up ambient air to temperatures of around 700°C. The hot air's heat energy is transferred to a steam Rankine cycle in a heat recovery steam generator (HRSG). The steam drives a steam turbine, which in turn drives a generator for producing electricity. In order to increase the operational hours of a solar tower power plant, a heat storage system and/ or hybridization may be considered. The advantage of solar-fossil hybrid power plants, compared to solar-only systems, lies in low additional investment costs due to an adaptable solar share and reduced technical and economical risks. On sunny days the hybrid system operates in a solar-only mode with the central receiver and on cloudy days and at night with the gas turbine only. As an alternative to methane gas, environmentally neutral biogas can be used for operating the gas turbine. Hence, the hybrid system is operated to 100% from renewable energy sources. An advanced software tool library has been developed for modelling such solar hybrid power plants. This library includes the components of the solar-heated hot gas cycle and the steam cycle. Moreover, a choice of different gas turbine and duct burner components is given. When developing a simulation model for the calculation of a small hybrid power plant, components from the library are inserted into the model. The software tool features the possibility of either calculating the energy output of individual operating points or of time intervals in the range of days up to an entire year. With this simulation tool, hybrid solar tower systems are calculated for various locations with high solar potential within Europe. In addition, locations in North Scandinavian countries with high biomass potential are investigated and power plants with biogas as fuel without solar input are calculated.