de | en | fr | tr

Passive house »Wohnen & Arbeiten«

Walter-Gropius-Strasse 22 • D-79100 Freiburg • Germany • Vox: +49 761 4568330
Email: post(at) • Web:
The Idea 
What is a Passive house? 
Energy Concept 
Research Outcomes 
The Cost 
Co-generation Unit
Residents, Owners 
Guided Tours 
Privacy policy 

The Small Co-generation Unit

  Sachs HKA-Co-generation Unit
  Click on the picture to enlarge:1024 x 768
  BHKW (opened)
  Interior View of BHKW
  Warm Water Connection of the Washing Machines

In the planning period of the houses, it was clear at an early stage, that the Vauban territory would be equipped with a local heating network: An ecologically progressive procedure, particularly with Holz-BHKW which is actualized by Badenova. In principle, we would have chosen this network, however...

Are Local Heating and Passive houses Incompatible?

When a community of a development area chooses a local or long-distance heating network, everyone has an obligation for alignment and use: every owner is obligated to join, since with a low level of participation such a network would not be economicaly or ecologically sensible.

Because the cost of the installation of a heating network is really high, (and because one wants to provide the consumers with cost-effective heating), it is conventionally and legally allowed, to shift the cost of the network (upto 70%) onto the consumers rightaway. Only 30% is paid by the provider, which, from the beginning, has a reliable customer base and a monopoly in the region. The so-called "additional connection costs" are levied per square meter of living area, independent of how much heat would actually be used later.

If we had agreed on the alignment for the local heating, we alone would have had to pay a five-figure sum for the additional connection costs for the whole house. This amount may be acceptable for a house with normal heating standards, since this sum for the most part is more favorable than a comparable installation, for example, a gas boiler. Due to our very low heating needs, this meant that we had to pay more money than we had to for a small gas-operated co-generation plant, with which we sympathized anyway since in that case, we could produce another part of our electricity ourselves and more ecologically than the traditional way allows for.

The logic and the justification -quasi "preamble"- of having to align oneself with the network enabled by the legislator, is "the cost-effective and reliable supply of heat". However, cost-effectiveness would not have been the case for us.

Private Electricity and Heat Production Cheaper than Local Heating!

The direction of the negotiations was clear: The postulated connection price was too high for us; we had built this house also so we could save some money. In the negotiations, we, the city and the energy supplier have agreed on that we, as the passive house residents/owners would come clear from the connection price and the obligation to use the local system. This was only on the condition that we would really build a passivehouse and would not try to avoid the regulations. This was for us, a task that we happily would comply with.

After considering the pros and cons of a local heating system, we can come to the conclusion that local heating systems and particularly the "combined heat and power generation" system has a big and important potential for especially old buildings. However for passivehouses, which already have very small energy requirements, local heating systems do not make economical and ecological sense.

  What does Combined Heat and Power Generation (CHP) Mean?
  With the traditional power generation via combustion engines, turbines, or steam (for example in power stations operated by oil, coal, gas, timber or uranium) only a third of the energy input (chemical energy in form of fuel) is transformed into electricity. The rest is industrial waste heat which mostly ends up not being used, escapes into the atmosphere through cooling towers.

By using combined heat and power generation, one attempts to avoid this wastefulness by using the waste heat wisely, for example to heat the rooms. Because the heat can not be produced and transported discretionarily warm (a good isolation for district heating pipeline is very expensive), the waste heat from big power plants can not be used for the heating need of the cities, eventhough it would have been the best option. Moreover, noone wants to live close to a power plant (inherently because of the local emissions) or even more certainly near a nuclear power plant. Therefore, there is still wastefulness (and certainly the electricity cartels, before and after the war, made sure that all of the Europe had fully inefficient power generation, even when higher technologies were available).

When one wants to use the waste heat emerging from electricity production sensibly (combined heat and power generation), one needs smaller devices: This would be a co-generation unit as the power generator. The market for these small power generators was very small in the beginning, so it was very costly to produce these units. Moreover, the electricity cartel still has the market in its control; the consumers are charged 17 cents per kilowatt hour when a charge 3 cents per kilowatt hour is feasable for public supply of electricity. For a wheeling to the Neigbors, the electricity supplier asks for virtually 15 cents. They act as if electricity in arbitrary amounts was available free of charge and as if only the wheeling was extremely expensive. Therefore, it was very hard for the alternative electric generators to fight against the monopoly. Since 1998, by J├╝rgen Trittin's EEG (Energy-Injection-Law, prepared by Klaus Toepfer), there has been an increased move towards regenerative electricity production in the market.

Translation: Selin Devranoglu 2005