Cool with waste heat

New technology uses combined heat and power plants and geothermal probes

Environmentally friendly and economical air conditioning DBU
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Scientists use the waste heat from cogeneration plants and the cool soil via probes to air-condition buildings.

Germany is sweating! But the pressure on the power button of the air conditioner produced in many contemporaries conscience: High energy demand torments from ecological aspects - and hefty costs later cause hot flashes when looking at the annual bill of the energy supplier. That does not have to be! The Technical University of Hamburg-Harburg has now demonstrated in the building in Hamburg that an environmentally friendly and cost-effective air conditioning without chiller is possible. The trick: The scientists use the waste heat of combined heat and power plants (CHP), which complain about a low demand for heat in summer, and the cool soil via probes. The project was supported by over 100, 000 euros by the German Federal Environmental Foundation (DBU).

The air conditioning of buildings requires cooling and dehumidifying the outside air, the latter usually swallows the larger amount of energy. The prior art is the use of electrically operated refrigeration systems. Here, the air is cooled below the dew point in order to condense the steam, so to be able to separate the water. Then the now dry air has to be heated to the desired level again.

Demonstration plant in Hamburg

In the demonstration plant in Hamburg, an air conditioning concept consisting of an adsorption wheel - a kind of rotating filter -, a CHP and ground probes was implemented. The peculiarity: the air is no longer dried by using the high-quality energy stream, but by the Adsorptionsrad and the waste heat of the CHP. The dry fresh air is brought with the cold from the ground probes to the desired temperature. Another special feature: The use of underfloor heating in summer for cooling.

Usually, the entire cooling done by the exchange of air - which often leads to the well-known unpleasant drafts due to the large amounts of air - here is the floor to the surface cooler. The system was equipped with the appropriate measuring technology in order to be able to compare economy and energy requirements with conventional systems. For two years, the summer and winter operations were accompanied. display

Considering a whole year, it was found that a comparable building with a conventional air conditioning system has a 14 percent higher primary energy demand. DBU General Secretary Fritz

Brickwedde: "Compared to an electrically driven air-conditioning system alone, the demonstration plant is economical from the beginning because of the comparable investment and the considerably lower operating costs. The air conditioning of buildings will continue to spread in temperate climates in the future. In this respect, the project and its results are, above all, ecologically important. "

(ots / DBU, 23.08.2004 - DLO)