Solar thermal energy

Curved panel that captures solar energy

What is CSP?

Concentrated Solar Power (CSP) uses parabolic mirrors to concentrate sunlight at one point to produce heat that can be used in industrial plants. This way, renewable energy is supplied to all the production cycles requiring high temperatures.

 

This system has been used since ancient times, but at the Eni Research Centre in Novara we have developed new solutions that increase its efficiency, ease of installation and, thanks to the fact that we have also made it more cost-effective, the possibilities for its use in various contexts.

Main features

Renewable
Renewable

Pilot plants

Thermal energy
Electric energy

Politecnico di Milano,
Massachusetts Institute of Technology (MIT) in Boston

What is it for?

Concentrated solar power generates heat at high temperatures using sun rays. Through the use of linear parabolic mirrors, the rays are concentrated, allowing a fluid to be heated up to a temperature of around 550°C. The thermal energy produced in this way can be used within production cycles that require heating processes to produce steam for direct use, or to drive a turbine and produce electricity. The principle was already common knowledge in Archimedes' times and has been applied industrially since the 1970s. At the Eni Research Centre in Novara, we have developed new technological solutions to make it more efficient.  In order to study its applications we have established a testing plant in Gela.

How does it work?

The sun's rays are concentrated by the mirrors onto a tube (called a receiver) into which a heat transfer fluid flows (i.e. one capable of storing heat), which in turn transfers it to an exchanger. To make the system more efficient, we worked on four elements: the mirror, the casing of the receiver tube, the heat transfer fluid, and the support structure. For the reflective surface, we chose a special PET and silver film that is much lighter, stronger and cheaper than traditional glass mirrors. The pipe that the fluid flows through is made of multilayer steel and ceramic with optimised thermal properties.  For the fluid, we opted for a mixture of molten salts that solidifies at much lower temperatures than the fluids used thus far. Finally, in the overall design we adopted the simplest structural solutions possible.

Notes

1) A lower solidification temperature of the heat transfer fluid allows it to circulate at lower temperatures during the nocturnal hours, significantly decreasing the system’s thermal losses.

2) Higher absorptances and lower emissivity of the receiver pipe allow more efficient use of solar radiation, so smaller solar fields can be constructed with considerable cost savings for the entire system.

Features and performance

The solutions developed by Eni research can reduce the cost of mirrors by up to four times and halve the cost of a concentrating solar power plant. Savings are coupled with an improvement in the individual components’ efficiency. 

100-150
°C

fluid solidification point (vs. ~250°C for conventional fluids) ¹


95%

absorbance of the pipe that the fluid flows through ²


7%

pipe emissivity (at 550°C) ²


100-150
°C

fluid solidification point (vs. ~250°C for conventional fluids) ¹

95%

absorbance of the pipe that the fluid flows through ²

7%

pipe emissivity (at 550°C) ²

Expand

Technological partners

Solutions to improve concentrating solar power are being studied at the Eni Research Centre in Novara, in collaboration with the Milan Polytechnic and the Massachusetts Institute of Technology (MIT).

The other possibilities of solar energy

Eni's research involves studying solutions to utilise the sun's energy in alternative ways, useful not so much for large-scale electricity production as for being integrated into buildings and infrastructure. Like Organic Photovoltaic (OPV), photoactive films as thin as newsprint. Or like the Luminescent Solar Concentrators (LSC), coloured glass panels capable of capturing diffuse light and concentrating it at the edges where, thanks to photovoltaic strips, it is converted into electricity. 


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