VTT Technical Research Center of Finland and German company ZAE Bayern have built a pilot system emission-free, solar-powered chiller. Demand and the need for cooling are growing, the potential market is world-wide, particularly in warm countries.

VTT ZAE Bayern Solar Powered Chiller Diagram with the main components and energy flows in the SHC-System. Image Credit: VTT Technology. Click image for the largest view.

VTT and ZAE Bayern have developed a solar-powered 10 kW chiller. This absorption chiller works in the same way as the gas refrigerators used in Finnish holiday cabins, for example. But in this case, a solar thermal collector is used instead of gas. The method requires electricity for the flow pumps only. If necessary, the chiller can also serve as a heat pump.

The results of the project showed that – to be used as a heating pump as well – an economically viable and competitive, solar-powered absorption chiller would need to be 50 kW or bigger.

Finnish company Savo-Solar Plc participated in both the planning phase and the practical tests. As a result, the company’s head office was successfully cooled using the pilot system built for the project. Savo-Solar and ZAE Bayern aim to develop a commercial product which enables users to cut their electricity bills through cooling with absolutely no need for electricity.

The chiller was tested as an air-conditioner for Savo-Solar’s office during the summer and for heating it during the winter. Solar collectors on the roof of the building were used to collect the required energy. If the collectors did not produce enough energy during, say, the winter, or on a cloudy day, a heat pump served as a substitute energy source. Other possible energy sources would be district heating, biofuel boilers or industrial process heat. Examples of large, megawatt-class absorption chillers based on district heating can already be found in Helsinki and Turku in Finland.

Another practical test was performed using an absorption chiller based on a bio-boiler in ZAE Bayern’s laboratory in Munich, Germany. This also is a system that can be supplemented with solar energy.

The project began in October 2013 and ended at the turn of last year running 39 months. It was funded by: Savo-Solar Plc, Tekes – the Finnish Funding Agency for Innovation, and the German Federal Ministry of Economics and Technology (BMWi).

Considering the electrical power grid mess that Germany has voted itself into, this kind of project has intense interest. The idea that cooling and heating can be nearly electricity free has an immense attraction when the power grid costs ratepayers incredible sums compared to any other industrialized country.

But does it really work? Its a compact absorption chiller comprising hydraulic rack absorption machines that transform heat into cold by means of a sorption process between a refrigerant (e.g. Water) and a Sorbent (e.g. Lithium bromide) and can be used as a chiller or heat pump. In contrast to conventional vapor compression chillers/heat pumps, the required electricity consumption is almost negligible. Yes, it works. Keep in mind, it always needs a heat source. You’re going to need some saved heat to air condition over night.

What’s missing for the rest of the world is the initial cost estimates and the longevity expectation. With Germans shelling out double and triple U.S. electricity rates the calculations start from very different inputs. What isn’t real clear is the amount of solar paneling needed to harvest heat.

This technology will find some market. Its too soon for information that may apply to the rest of the world. There is also a lithium component, a not so inexpensive item. Unless batteries get far smaller and higher capacity lithium will continue to be rather expensive.

Still for a huge part of the world this technology has great appeal. Low cost cooling where air conditioning is a major part of household expense is going to have some market legs.


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