1 - Introduction to concentrating solar thermal (CST) technologies

Abstract

Concentrating solar thermal (CST) technologies provide promising and diverse opportunities to power the present and future needs of humankind. All solar energy systems are designed to maximise the advantages provided by the sun as an energy source and to minimise the disadvantages. CST technologies collect and concentrate radiation from the sun to transform it into high-temperature thermal energy. This thermal energy can later be used for a plethora of high-temperature thermal applications, such as heating and cooling, process heat, material treatments, electricity production, or chemical processes. This chapter provides a background to the sun as our most valuable energy source, the defining characteristics of CST technologies, and the need and limits associated with the concentration of sunlight. It presents the competing tendencies for the efficient conversion of direct solar radiation into useful thermal energy and the subsequent transformation into work by a heat engine and explains how this leads to the existence of an optimum in the overall light-to-work conversion efficiencies of a CST system in terms either of the operating temperature or the solar radiation concentration capabilities of the system. It also provides an overview of the four main commercially available solar concentrating technologies, along with the current state-of-the art of CST technologies for electricity and process heat generation, solar chemistry, and thermal energy storage, and an overview of the major research efforts around the world to increase the cost-competitiveness of CST technologies and ensure that they will play a major role in the necessary and urgent transition to a much more environmentally friendly world energy system. Finally, the chapter presents the overall concept of this book on advances in concentrating solar power research and technology, which aims to provide an overview beyond the state-of-the-art of CST technologies, with a focus on advanced CST concepts that are emerging as incremental or step-changes in CST technology.