Renewable energy

Haven’t you thought about alternatives to your conventional heater installation? But which alternatives do I have? There is a certain number of ways to generate energy based on renewable resources: wood-pellet heating, solar collectors for hot water conditioning or groundwater/air/soil heat pumps.

Conclusion for PKG

For our school “Paul-Klee-Gymnasium (PKG)” the most reasonable and most long-term solution would be a groundwater heat pump since groundwater is already available in a depth of eight metres on the school’s land. Therefore, this system would be very profitable. Ground-source heat pumps obtain heating energy from the groundwater and furthermore, they feature the best coefficient of performance of all heat pump systems. However, it is the most expensive option. Non-abrasive and available groundwater is one assumption for the operation of heat pumps. Moreover, the watershed management department’s authorization is required. In our case, the watershed management department of Donauwoerth is responsible for the authorization. On the picture right hand, you can see a fuel bill that compares the existing gas heating with a groundwater heat pump (German only. Sorry!).

Functionality of heat pumps

A heat pump is an assembly that imbibes heat on a low-temperature level and dissipates it on a higher, useable level using mechanical or electrical operating power. The bulk of this heat is nothing else but absorbed solar energy in the ground, the water or the air. Heat pumps usually obtain electricity from the grid and operate a compressor that imbibes heat from soil, groundwater or air. At a temperature of -5°C to +10°C heat is extracted from the soil and afterwards dissipated to the heating at a temperature of +35°C to +55°C.

Subsequent to this paragraph, you can find a flash animation featuring different types and functions of heat pumps (German only. Sorry!):

Demonstration Application

Solar energy

Although Germany isn’t one of the sunniest countries in Europe the solar intensity suffices to fuel solar plants profitably, even in this part of the world.

How it works:

In general, solar plants for service water warming are installed in detached or semidetached houses. Sunlight is transformed in heat by the use of efficient flat-plate or evacuated tube collectors. An antifreeze mixture transports the solar heat into a service water repository that is capacious enough to meet the hot water requirements of two to three days. If the hot water does not suffice in winter or in the transition period, the conventional central-heating boiler will heat up the repository using a secondary heat cycle, which offers the user permanent hot water, even while the sun is not shining. Choosing the proper collector area will allow the user to cut off the central heating boiler during summer term. Thus, the solar energy heats up sixty percent of the water.

Wood pellets

Another way of generating energy from renewable resources provides wood, pressed in so-called “pellets”. Pellets are small-sized wood sticks pressed from sawdust and strands.

How it works

The functionality of a pellet stove is similar to the functionality of an ordinary wood stove. A heat exchanger transports the heat energy generated by wood pellets. Wood pellet heaters are combined with solar plants in the majority of cases.

Finally we would like to say “Thank you!” to Mr. Bernhard Wenzel and his organization “Verein Klima Innovativ e.V.” who made both calculators available to us.

Florian Behr und Christoph Herold

translator: Julian Schöler

Wikipedia.org
Firmen:
Viessmann
Junkers

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