CSP (Concentrating solar thermal power) has long been viewed favourably by the wholesale energy sector. Now, advances in technology – including the vital thermal storage capacity that enables solar variability to be decoupled from a plant’s output – have succeeded in converting that sentiment into reality as a series of major new projects are commissioned. However, there is still some ground to cover before the technology achieves its potential. One crucial area is the development of industry International Standard.
Not that recent
Some 150 years after the French mathematician Augustin Mouchot demonstrated steam generation from concentrating solar energy, the use of solar energy steam generators connected to fairly standard conventional power islands – a steam turbine and generator – is a technology that is now becoming increasingly popular.
Indeed, while the various designs of solar collector may present some novelties, CSP installations share many common traits with their fossil-fired cousins. It is perhaps for this reason that CSP has attracted the interest not only of utility companies keen to expand their renewable portfolios, but also of original equipment manufacturers which have traditionally supplied the utility market.
Many technologies, but one aim: heat
CSP comprises a range of technologies that are used to collect and concentrate sunlight, turning it in to medium to high temperature heat. This heat may then be used to generate electricity in a conventional way using a steam turbine or a Stirling engine, or used in other applications, for example supplying process heat. With the exception of dish-Stirling systems in CSP power plants, the solar energy is typically absorbed by a heat transfer fluid, such as oil or molten salts, which is then passed through a heat exchanger and its associated steam circuit.
The mirror systems used in CSP plants are either linear or point-focusing systems. Linear systems typically concentrate the solar radiation by about one hundred times and achieve working temperatures of up to 550°C. Point systems can achieve far higher concentrations, more than a thousand times, and consequently can reach far higher temperatures, with 1 000°C or more possible.
There are four main types of commercial CSP technologies in operation today. Linear systems include Fresnel lensing and the far more common parabolic trough types. Point concentrating systems include parabolic dish-type systems, typically used with a Stirling engine, or the more common central or tower receiver systems.
Developing industry International Standards
Another major trend identified by both Tassos and Prieto is the burgeoning development of industry Standards for the emergent CSP sector.
As Tassos points out, CSP is in the relatively early stages of global development and industry Standards could provide a foundation upon which to develop new technologies and enhance existing practices. “This could also provide additional comfort to potential investors and lenders, reducing barriers to bankability and subsequently accelerating market penetration”, he says. Tassos continues: “As Standards generally reflect the best experience of the industry, they constitute an important basis for improving the credibility of new products, assisting in the development and implementation of novel technical solutions”.
He argues that the main effort in the early stages of standardization should be placed on elements such as terminology, optical and thermal characterisation of new collectors, performance testing and modelling and environmental and safety requirements.
For example, among other activities, IEC TC 117 is currently running three ad hoc groups related to CSP Standards development, considering themes such as systems and components and energy storage. As for IEC TC 120: Electrical Energy Storage (EES) Systems, it includes thermal storage in its scope, but “only from the electricity exchange point of view”.
Prieto also flags up the advantages of developing a comprehensive system of Standards, saying: “In a very global world, where tenders are international, those people who are organising tenders ― they’re usually governments ― need to be sure that the requirements they are asking for are met and the only way they can do that is through Standards”.
She concludes: “CSP is a very promising industry; we have a huge market ahead. We need to make an effort and the effort should be based on technology, so we should keep diminishing costs thanks to technology ― and Standards will help a lot.”
Written by David Appleyard for our e-tech Magazine. To find out more check out our e-tech article.