An image of KTH Royal Institute of Technology's new solar flux laboratory. Image courtesy of KTH.

By Jason Deign

CSP research and development activities have been given a boost with the opening of a new indoor solar laboratory for high-flux research.

The lab, at the Heat and Power Technology department of the KTH Royal Institute of Technology in Stockholm, Sweden, is being inaugurated on 27 February 2015 for researchers pursuing projects in solar concentration technologies such as CSP and concentrated PV.

The core of the facility, the first of its kind in the Nordics, is an array of twelve 7kW Xenon-arc searchlight lamps with Fresnel lens concentrators that deliver 20kW on a 20cm-diameter target 1.5 metres away, with a peak light flux of 6.7MW per square metre.

The setup imitates a parabolic dish flux and can reach temperatures that top 2,000ºC. “High-flux components form the central element of high-efficiency solar power plants and are often the life-limiting component in these facilities,” points out KTH on its web site.

The opening of the lab represents a valuable addition to Europe’s existing solar flux research centres, which include facilities at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt or DLR) and the Paul Scherrer Institut in Switzerland.

“There are similar and even larger facilities in research institutes, and there are universities doing this kind of research,” said Björn Laumert, associate professor at the KTH Division of Heat and Power Technology. “But there is some uniqueness to this facility.”

For example, the KTH array does not use parabolic back mirrors to concentrate the light. Instead, “we came up with the idea of using lenses instead of mirrors,” Laumert said. “A PhD student came up with the idea.”

The design makes it possible for KTH to use relatively low-cost searchlights, of a kind used on Chinese marine carriers, without compromising on the quality of the results. Also, the use of lenses should make it easier to simulate trough setups, simply by changing the lens design.

Three projects

Furthermore, while Laumert recognises the light will not accurately mimic standardised light sources for PV, researchers in the lab will be able to apply filters to the lamps to study certain wavelengths. The facility has already been slated for use in three projects relating to CSP.

The first is an Optimised Microturbine Solar Power or ‘OMSoP’ system project co-funded by the European Union’s seventh framework programme for research and development, which aims to develop CSP systems of up to 10kW coupled to micro-gas turbines for electricity generation.

Within this, the KTH lab will be used for dish designs. Secondly, KTH is working with the Swedish dish Stirling developer Cleanergy, which last year was making moves to enter the Middle Eastern market.

KTH is helping the company develop new, more efficient and cost-effective receivers. Finally, a third project, under the aegis of a Swedish national turbo-power research programme, will look at how to regulate solar flux and fuel in a hybrid gas and CSP plant.

However, the lab is open to other customers. For direct research agreements, Laumert said KTH, as a university, can offer cost advantages compared to traditional research institutes.

“We maybe do not need to incorporate fixed costs in a similar way as research institutes need to,” said Laumert. “We have fixed costs, and we need to handle them, but they are not in the same range as other institutes.

“Now the lab is in place, there are no costs apart from the running and component costs. Also we can work with PhD students and we have a lot of PhD students that we can use in this process. And of course you can get access to Master students.”

Research support

Effectively, Laumert points out, KTH can provide research support ranging from Master level up to full programme development. This gives developers a wide range of support options to choose from, from small focused projects up to large programmes.

Another way developers can take advantage of the lab is by working with funding bodies. KTH already works with the Swedish solar research programme and is applying for projects at the Nordic regional level.

For these, “I think we are an attractive partner because we are a very strong university,” Laumert said.

All this adds up to greater choice and flexibility for solar, and particularly CSP, research. In particular, facilities such as the KTH lab could make it easier to carry out smaller projects that can lead to incremental improvements.

The presence of such labs is critical to ongoing research into new CSP technologies, said Ilaria Besozzi, head of business development with the Swiss technology developer Airlight Energy.

“High flux solar simulators provide an non-intermittent, on-demand source of concentrated solar radiation,” she stated.

“For example, Airlight Energy collaborates with the Professorship of Renewable Energy Carriers at the Swiss Federal Institute of Technology Zurich, that has developed its own solar flux simulator. This instrument can reach a concentration factor of up to 10,000 suns.”