Innovative CSP tower system coupled with solar micro gas turbine

In this thesis a complete thermodynamic, operational and economic analysis of a solar micro gas turbine is presented (design net power output of 187.3 kWel). The heliostats field is taken from the existing plant of Aora in Almeria (Spain) while the tower receiver is optimized to give the maximum annual performances (optical efficiency of 72.02%). Following a description of the components necessary to implement the power block, such as the volumetric receiver (allowing a higher maximum temperature with respect to a tubular receiver, respectively 1200°C and 800°C), a Matlab model is developed to simulate both on-design and off-design performances of the system. Technical constraints regarding the receiver, the recuperator, the combustor and the gas turbine engine (operating up to 950°C to avoid cooled-blade technologies) are accounted for a correct run. On-design conditions are characterized by a DNI of 950 W/m2 (peak flux in Sevilla) and an ambient temperature of 35°C, which correspond to an incident power from the sun of 790 W and the resulting solar-block efficiency is 32.99% while the solar-to-electric efficiency is 23.71%. The exergy analysis of the design system is also presented, highlighting a total second-law-efficiency loss of 74.51%, mostly due to the solar block (loss of 46.31%). Referring to the GSE in Italy, a power plant can access renewable incentives while using an annual fuel-integration up to 15%. Thus, off-design conditions of the system also include hybridization. Different strategies of operations are considered, such as the solar-only-mode (annual energy of 285.3 MWhel and annual ηsol-el of 0.2189), the nominal-power-mode with heavy fossil fuel firing (annual energy of 479.0 MWhel and annual ηsol-el of 0.2141), the maximum cycle efficiency mode (annual energy of 398.2 MWhel and annual ηsol-el of 0.2325), the hourly fuel-control of 15% (annual energy of 333.9 MWhel and annual ηsol-el of 0.2176) and the optimal renewable strategy with hybridization only when sun’s irradiation is low (annual energy of 339.0 MWhel and annual ηsol-el of 0.2239). A particular attention on CO2 emissions-savings with respect to a standard gas turbine is exposed. Based on the reliable power-block costs (346.33 euro/kWe), and on the more uncertain solar-block costs (2444.24 euro/kWe), the final economic analysis is computed considering two possible discount rates, presenting a best scenario (LCOE of 0.2064 euro/kWh for the renewable strategy) and a worst scenario (LCOE of 0.2717 euro/kWh). Other economic parameters such as Net Present Value, Pay Back Time and Internal Rate of Return are calculated to evaluate the profitability of the project. Finally a last case in view of a future where incentives wouldn’t be available anymore is considered, to understand if fuel-integration would be convenient or not. This analysis shows how the income increases with a higher hybridization, even though the profits remain negative.