Optimised Solar Concentrators in Multi-Tower Multi-Aiming Configurations

Abstract

The increased focus on renewable energies all around the world is fuelled by a combination of global warming and others environmental concerns, fuel prices fluctuations and their long term uncertainties, and the growth of electricity demand in the most populated regions of the world. Concentrating Solar Thermal (CST) technologies are among the series of renewable energy technologies that are expected to play an important role in the mid to long-term future. In its most recent roadmap [1], the International Energy Agency estimates that CST technologies may provide 11% of global electricity generation by 2050. Solar Tower (ST) technology is one of the most promising CST technologies, due to its ability to achieve high operating temperatures and also integrate high temperature and high volume storage, allowing a wider range of application than other CST technologies. Although ST technology witnessed robust growth in the last years, it needs additional research to unlock its full potential and enhance its cost competitiveness. The improvement of the annual efficiency of heliostats fields in ST technology (currently typically well below the 70% mark) could significantly contribute to increase the cost competitiveness of this technology, since the cost of this ST subsystem is a large fraction of the total cost of the overall system. Up to now, research targeted to improve the annual efficiency of heliostat fields has resulted in limited gains in the annual efficiency, due to the interdependences of influent factors. Indeed, the improvement of some factors affect the performance of others and consequently limit the total gain. The ultimate goal of the proposed work is to identify the major factors limiting the techno-economic performance of the light collection and concentration (LCC) subsystem of a solar tower in a solar tower system and explore ways of overcoming them. This subsystem is the combination of the heliostat field and solar receiver(s) envelop(s). As a whole, the LCC subsystem is in charge of collecting and concentrating the direct solar radiation into the absorbing surfaces, and/or the entrance apertures of the central receiver(s), where the concentrated solar radiation is transformed into thermal energy. This identification will start with the formulation of idealized models of LCC subsystems to establish the upper limits of their techno-economic performance. Once these upper limits are established and their dependence on the main variables that characterize the LCC subsystem are analysed in detail, more realistic models of the LCC subsystem will be formulated and analysed, with the aim to gain insight on how to design high performance LCC subsystems that will substantially enhance the cost competitiveness of ST technology. Show more