Net energy analysis for concentrated solar power plants in northern Chile

Chilean energy policy goals attempts to promote efficiency and sustainability in the energy system. These objectives have been considered in recent modifications to the electricity generation laws by establishing that generation companies must reach a quota of up to a 10% from renewable energy sources by 2024. Concentrated solar power (CSP) is an interesting alternative to help achieve those objectives, as it is estimated that northern Chile has high radiation levels, coupled with the high values of the local clearness index and flat land availability. However, from the sustainability point of view it seems necessary to assess if a CSP plant is effectively an energy source. Here we propose a hybrid solar power plant lifecycle model which through a net energy analysis obtains and analyzes the plant energy sustainability attributes such as net energy, energy return over investment and energy payback time. The stages of construction, operation, maintenance and decommissioning are considered in the lifecycle analysis. The model is then applied in order to determine good locations where to install a CSP plant in the Chilean Atacama Desert. Monthly means of solar radiation are used in order to estimate the solar fraction for a 100MW direct steam generation parabolic trough collector plant. The results indicate that solar power plants are effectively a net energy source for the analyzed locations, and that higher energy costs are related to the fossil fuel backup lifecycle. A relation is established between yearly radiation, energy return over investment and energy payback time. It is estimated that the net energy analysis is a useful tool for determining under which conditions a power plant becomes a net energy source and therefore a more convenient option from the sustainability point of view, and thus can be utilized in order to define best geographical locations and operation conditions for different renewable energy sources. The sustainability attributes are greatly enhanced when considering a solar-only operation mode, which highlights the advantages of using that configuration, and presents a case for the use of thermal energy storage systems rather than fossil fuel hybridization if a constant or dispatchable energy profile is required.