Technology

As an emerging technology, there are still plenty of areas for research and development in CSP. But limited investment budgets mean technology developers must choose their bets carefully.

By Jason Deign

At first sight the power tower being built in the Tabernas Desert, Almería, looks like those the CSP industry has put up elsewhere in Spain.

Once it is finished, though, the difference between the Llano de los Retamares facility and all the other power towers in the world will be obvious enough, if you are patient. Unlike the others, it will move, with its receiver and mirrors following the sun to get the best possible efficiency.

The plant is a test design conceived at Andalusia’s Renewable Energy Advanced Technology Centre (Tecnológico Avanzado de Energías Renovables or CTAER in Spanish), with a 57.7 metre-high tower and an initial set of 13 heliostats (or, more correctly, ‘heliomobiles’).

The installation of the heliomobiles was scheduled for completion this month, with tests due to begin shortly after.

“The CTAER wants to show at full scale that with the tracking of the apparent movement of the sun, which is the resource, there will be a greater concentration of solar radiation and therefore a better plant performance,” said the Centre in a press statement.

Such an innovation seems obvious when you think about it, and indeed trackers are already a familiar component in other areas of CSP and photovoltaic power.

“Conceptually it is simple,” says Valeriano Ruiz Hernández, the president of CTAER and the brains behind the variable geometry power tower project, “but making it a reality is a different thing.”

Still, the fact that nobody has thought of using power tower tracking until now is perhaps a measure of just now nascent the industry is in terms of technology development, even though CSP has been around for decades and is ultimately based on simple engineering principles.

Solar thermal performance

Ruiz estimates this single measure could improve solar thermal performance by up to 17%, a figure he hopes to demonstrate in practice with the tests due to start in Almería.

And it is just one of several measures which could demand further attention from research and development teams. Ruiz says that other areas currently under investigation at CTAER include thermal fluids, low- and zero-water-use generation, and hybrid-use receivers.

Of course, CTAER is just one of several institutions carrying out research into CSP. It is closely allied to the Almería Solar Platform, which is also a testing ground for DLR, the German national research centre for aeronautics and space and one of the world’s leading CSP research bodies.

And mirroring the work of the DLR across the Atlantic is the US National Renewable Energy Laboratory.

The Commonwealth Scientific and Industrial Research Organisation fulfils a similar function in Australia, and several universities worldwide, including the Massachusetts Institute of Technology, are involved in making valuable contributions to the body of lore around CSP.

All this activity is largely apart from the research and development interests of CSP developers. However, given the large capital costs involved even in building demonstration plants, it remains the case that the pace of innovation in CSP is still probably not what it could be.

With a limited amount of money and expertise available for research across the industry, it makes sense for development teams to focus on areas that offer the greatest promise for improving the commercialisation of CSP.

For most renewable energy sources, ‘improving commercialisation’ usually equates to reducing the levelised cost of electricity (LCOE) of the technology, to make it competitive with traditional power generation.

Tracking mechanisms

This is certainly also the case with CSP, and innovations such as the variable geometry power tower could go a long way towards this goal, provided the tracking mechanisms can be produced cost-effectively.

However, says Ravi Yadav, project manager for alternative energy at the analyst firm GlobalData, there is one aspect of CSP that other renewable energies cannot match and that deserves plenty of research effort.

“We have seen a fair amount of investment going into the storage space, because storage is one thing that sets apart CSP from other renewable technologies,” he says.

Continuing research into CSP with storage could be the ace in the sleeve for the industry, he continues, because “With any other renewable technology, most of them have the limitation that they are intermittent. That is why it is a prime area for research.”

Within storage research, he adds, there are two broad goals: bringing down the cost of storage on one hand, and ensuring a greater amount of heat is stored on the other.

Finally, there is the issue of the efficiency of storage; ideally, says Yadav, you want to be able to get about 95% or more of the energy you put in back out again, cost effectively.

Beyond that, he points to issues such as glass performance and water use as other areas crying out for greater study. Clearly, the drawing board still has a lot to offer CSP.   

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Or contact the editor, Jennifer Muirhead