Germany The Vattenfall Haus-Strom concept has developed from a micro-CHP solution to solar power delivered directly to the tenants.

Environmentally conscious tenants in Berlin’s many blocks of flats are now offered an opportunity to get solar-powered electricity directly into their wall sockets from their own rooftops. Vattenfall has launched a pilot project, the so-called Haus-Strom based on solar energy, in which the company installs solar panels on the rooftop of blocks of flats for free and offers the generated electricity directly to the tenants in the building without use of the public grid. And as about 85 per cent of the people living in Berlin are tenants in rented flats, this presents a huge opportunity for the ordinary Berliner and the owners of the houses to contribute to the German Energiewende and a better environment.

In mid-August this year, installation started of the first of the some 600 square metres of solar panels with an annual yield capacity of 90,000 kWh. They are being installed on three blocks of flats owned by a pension fund in the Halensee district in Berlin.

Installation of the 600 square metres of solar panels is almost completed.

A personal share in the Energiewende
“Many of the large residential buildings are owned by companies that may find it attractive to be able to offer their tenants an almost personal share in Germany’s Energiewende. It may be possible find a cheaper offer for “grey” electricity somewhere in the market, but if the price is fair many Germans are willing to change to a renewable electricity product – especially when they get it directly from the roof above their heads”, explains project manager Susanne Manger from Vattenfall’s BA Heat product development department.

The system is quite simple. Vattenfall installs solar panels on the rooftop and a new meter for the house connection, maintains the system throughout the agreed period, settles electricity bills and dismantles it afterwards without any obligations on the house owner. When the sun shines, the solar-powered electricity is sent directly to the tenants’ wall sockets without involving the public grid, but if more electricity is needed than the rooftop can supply, electricity is drawn from the some 120 micro CHP units Vattenfall is operating in residential buildings.  The tenants pay the same fixed price for the CHP- and the rooftop-generated electricity. If the rooftop panels generate more electricity than is needed, the excess is sold to the public power grid.

It took a big crane to lift the solar panels onto the rooftop.

Independence in choice of energy source
“It has been a wish from the German government that the many tenants for instance in Berlin and Hamburg should have a way to participate in and identify with the Energiewende. That is why they have eased the rules, fees and taxes regulating consumption of self-generated electricity. On top of that, there seems to be a general trend towards local renewable energy and a desire to be independent in your choice of energy source”, says Hanno Balzer manager of Vattenfall Energy Solutions who is responsible for the agreements with house owners and the tenants and originally took the initiative to the new concept.

“A study from the German Federal Ministry for Economic Affairs and Energy has shown that some 3.8 million German homes could potentially be supplied with locally generated electricity, so we hope that many house owners and tenants will accept the offer to convert their rooftops into green power plants together with us,” Manger concludes.

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