CERN Accelerating science

European Organization for Nuclear Research

Evacuable Flat Panel Solar Collector

Energy is an important domain where High Energy Physics can serve as a springboard for providing innovative industrial solutions. A new generation of evacuated flat panel solar collectors has been developed based on the Ultra High Vacuum technologies used in CERN’s accelerators for the minimization of energy loss in the beam pipes.

By efficiently preventing heat loss, the technology allows these collectors to achieve very high performance and operation temperatures. The collectors can reach a temperature of 350 – 400 degrees Celsius, over 100 degrees higher than what current commercially available solar panels can achieve.

 

The Technology

Figure 1: Evacuated Flat Solar Collectors using UHV technology

Solar collectors, in particular flat panel solar collectors, are well-known devices which are used to absorb and transfer solar energy into a collection fluid. Principally, solar collectors consist of a blackened absorbing cylinder or plate contained in a housing which is frontally closed by a transparent window panel.

Due to the diluted nature of solar light, reducing thermal losses is imperative to increasing the operating temperature. One way of doing this is by the evacuation of the solar collectors to eliminate gas convection and molecular conduction, or in other words, by creating a vacuum.

The Evacuated Flat Solar Collector is conceived based on this principle and the man behind the vision is Cristoforo Benvenuti, a senior physicist working at CERN. Making use of the Ultra High Vacuum technology developed for CERN particle accelerators, he invented the Evacuated Flat Solar Collectors.

 

Innovative Features

Figure 2: Non-Evaporable Getter (N.E.G) pumps

In the words of the inventor of the technology, Cristoforo Benvenuti, vacuum is the best heat insulation technique nature has to offer. Non-Evaporable Getter (N.E.G) pumps are used to create the Ultra High Vacuum. The working of these pumps are analogous to a chemical sponge, they use thin film coatings to create vacuum by trapping any air molecules that get near them. These coatings, produced by sputtering, may recover their chemical reactivity (i.e. pumping function) by heating at temperatures as low as 180° C.

Another important feature of these solar collectors is they capture both direct and diffuse sunlight. It is generally assumed that flat collectors are only suitable for low temperature applications. High temperatures are reached by high index of solar concentration through focusing mirrors (parabolic satellite dish).

Thanks to the use of UHV, high temperatures can be achieved without the use of focusing mirrors. The flat geometry of these collectors allows diffuse light to be captured. This is a very attractive feature as diffuse sunlight make up more than 50% of the total solar energy available.

 

Industrial Applications

Figure 3: UHV solar panel with cylindrical concentration systems.

Figure 4: UHV solar panel with flat concentration systems

Figure 5: UHV solar panel with flat collectors.

The application of the Ultra High Vacuum technology to solar collectors is a good example of technology transfer from High Energy Physics to everyday applications. The industrialization of the technology is the next leap forward. Spearheaded by the inventor of the collectors, a company has been founded to develop and manufacture the UHV solar collectors.

Thanks to the high performance of the solar collectors based on NEG technology – patented by CERN -- the solar collectors are applicable over a broad temperature range. The high capacity Getter pumps produce stable vacuum over several years of operation. These features make them an excellent product for industrial application, e.g. for domestic, district and industrial heating, air conditioning and the production of electricity.

 

Industrial and district heating

For industrial use, a higher temperature than is normally used in home heating is needed. With the capability to generate temperatures of up to 200°C, the UHV solar collector with cylindrical concentration systems (Figure 3) is an ideal candidate for industrial heating processes such as construction, chemical manufacturing and the agro-alimentary sector (examples: heat of tar tanks, paint oven, plastic injection molds, textile forming presses).

Another configuration of the UHV solar panel is a panel with flat concentration systems (Figure 4). The high concentration factor makes it the suitable solution for applications of electric energy generation and for large heating plants.

 

Home heating

The panel without concentration (one of the possible configuration of the UHV solar collectors, see Figure 5) is designed primarily for domestic use. Mainly for warm water and home heating, it has a high utility for country with low radiation because of its ability to also concentrate diffuse light.