Applications questioned for new tech doubling efficiency of solar energy capture

Potential applications for an EU-funded research project into a new solar energy capture technique that more than doubles the efficiency of common solar capture technology have been questioned by an expert.

The EU-funded Prometheus project has developed a new solid-state conversion structure for transforming solar energy to electricity, which increases the conversion efficiency to at least 45%. However, Junwang Tang, professor of materials chemistry and engineering at UCL, has said that he “cannot see a close market for it in the near future,” due to “big barriers” in the methods used.

The approach uses a photon-enhanced thermionic emission (PETE) mechanism and black diamonds, which the research report claims overcomes the limitations of common PV cells. This black diamond semiconductor captures the entire spectrum on sunlight, including infrared wavelengths that produce heat. The increased efficiency of the process is therefore a combination of conventional solar capture and thermal energy mechanisms.

The temperature of the concentrated solar radiation entering the Prometheus device is equivalent to between 200 and 1000 suns. The system proposed in the Prometheus project could in the future act as a substitute to the fluid in the main cycle of current solar capture methods, which use mirrors or lenses to concentrate a large area of sunlight over a very small area. It can therefore act as a ‘topping cycle’, with a secondary thermal cycle collecting the waste heat from power generation and using it to provide useful solar energy.

Nevertheless, Tang pointed out that it might be difficult to use it in solar capture applications in the near future. He said that with the solar energy converted into both electricity and heat, the heat energy cannot be used easily as “there is already so much waste heat around us which can be used economically.

The high temperatures used are "a big barrier, as special material is required,” he added. “For an economical approach, I prefer to use one or two sun intensity instead of this highly concentrated sunlight.

The €3M Prometheus project, funded through the Eu’s Future & Engineering Technologies programme, contained seven industrial and academic partners, with the aim of meeting EU targets reducing its greenhouse gas emissions to 40% of 1990 levels by 2030.