LEAD Innovation Blog

How the house roof can become a small power station

Written by Daniel ZAPFL | Jan 9, 2019 9:20:00 AM


According to the EU building directive, only very low-energy buildings are to be allowed to be erected by 2020. However, being almost energy self-sufficient cannot be achieved by saving alone. This goal can be achieved more easily with a small power station on the building. Read in this blog post what role the roof can play in the future.

When we talk about small power plants, many of us immediately think of solar energy. That's only legitimate. The generation of heat (photothermics) and electrical energy (photovoltaics) from sunlight is popular and widespread. Ingenious inventors can even assemble a system themselves with copper pipes, corrugated iron, wood and a few other ingredients. Others equip a tandem with a roof made of solar panels and thus cycle to Kazakhstan with an electric tailwind.


Energy self-sufficient through solar roof system

But Otto Normal consumers are also becoming increasingly interested in energy from the sun. No wonder: at least for homeowners, many energy suppliers have suitable solar packages in their range. The association wants to make homeowners energy self-sufficient at all. Part of the offer is the Tesla Powerwall. The home storage designed by visionary Elon Musk is intended to supply houses with electrical energy even during the darker periods when the sun is not shining so much. Musk has also shown the world that solar energy cannot only be generated with the help of ugly panels aligned to the position of the sun. This is also possible with chic solar roof tiles, which are available in the colour and shape to match the rest of the building. A small detail: Musk did not invent the solar tile, however - it has been around for several years. Musk is not the only one who deals with the subject of aesthetics and solar power.


Transparent solar cells are also suitable for the roof of the conservatory

The Lower Austrian solar technology company ertex solar recently presented a low-cost solar cell that also lets light through. So-called semi-transparent solar cells have been around for some time. However, they are usually seven times more expensive than the opaque versions. The cells developed by ertex solar now cost only half. In addition, their efficiency is also higher than that of previous solutions. Thanks to such translucent solar cells, not only windows but also the roof of a conservatory can generate electricity.


What the sun can't do, the wind should fix

Despite all the enthusiasm for solar energy, there remains a serious disadvantage, especially in our latitudes. The sun doesn't always shine. At night, for example. And if it shines, then one needs at least usually less heat energy. The obvious solution is wind energy. Because it also blows at night and especially when it is colder outside. Even the trade has easy-to-install sets ready for sale. In addition, mounting a wind turbine seems to offer significant advantages: The height of the house saves you a part of the mast, no space is needed in the already small garden, and the way to the power grid is extremely short.


Wind turbines on rooftops cause problems

But: the roof is usually the wrong place for wind turbines. On a single-family house in a residential area, such a system makes little sense: Firstly, the ideal wind speed for electricity production does not prevail directly on the roof of the house. And a mast several meters high does not make a really slim foot directly in the residential area, the building regulations once again ignored. Secondly, such wind turbines can also transmit sound. And that should disturb the neighbors. Wind turbines with a vertical axis would be better suited for the city. These are considered quieter, and the authorities are also more willing to approve such systems. However, these constructions have a considerably lower efficiency than the wind power plants, where the rotors rotate around a horizontal axis.


The windmill for cities comes from the Netherlands

From the land of windmills comes a small, approximately 4000 euro expensive device that could solve the problems that wind farms in cities bring with them. The Liam F1 wind turbine, the Rotterdam-based research and development company, produces electricity almost silently. The design resembles a Nautilus shell. The marine animal consists of several spiral chambers that the shellfish can fill with air to control its buoyancy. Due to the screw shape, the smart windmill moves automatically into the optimal position, and thus always achieves the maximum yield. The Liam F1 generates an average of 1,500 kilowatt hours of energy at a wind speed of five meters per second. This corresponds to about half the energy requirement of a normal household. The developers of Liam F1 have moved all their activities to South Korea and the project is now called Archimedes Wind Mill.


A nozzle makes legs for the wind on a flat roof

A Swiss start-up called Anerdgy has also developed a system that can draw a few kilowatts of electricity from the wind that travels through the cities: The Windrail® is a box-shaped construction and is mounted on flat roofs along the eaves. The turbine mounted in the box does not only use conventional wind energy. The pressure differences generated by air flows on the building are also used. These increase the natural wind speed and provide a boost in the turbine chamber. Windrail® uses the principle of the Venturi nozzle: the flow velocity of gases increases when they pass a narrow point. And: On the top of the box are solar panels that also generate electricity. Windrail® is available in various designs to meet the requirements of residential, office or industrial buildings. In Berlin, some Windrail® turbines are already generating energy. The only requirement for the installation: The buildings should have a flat roof.


Roof garden as urban air conditioning system

These buildings are often found in large numbers in cities. Flat roofs do not only offer space for Windrail®, but also for a garden. One of these creates more green in the city. It also helps to improve the urban climate: The Urban Heat Island effect has become a serious problem. The urban heat islands can affect the health of the inhabitants. So-called "green roofs" are one of many measures designed to combat urban heat hotspots. A special plant composition ensures that a lot of liquid evaporates on the "climate green roof" in dry and hot weather. This has a cooling effect on the environment. An additional advantage: The plants can also be supplied with grey water from the building.


Conclusion: How the house roof can become a small power station

Climate change and its attempt to prevent it are increasingly placing the roof at the centre of attention as a place to generate energy. This is only logical: where there are many buildings, a lot of energy is needed. And the most efficient way to produce energy is where it is consumed. There are already many possibilities to build small power plants on the roof. Thanks to the inventiveness driven not least by the EU Buildings Directive, there will probably be much more in the future.