Anyone planning a new home should pay attention to a number of things right from the first draft. Then enough solar power can be harvested to keep investments and energy costs low for decades.
If you are planning a new building, you should follow a few basic tips so that photovoltaics can cover the highest possible proportion of the electricity requirements in the building. If the houses are misaligned or the roofs are shaded, the shortcomings can hardly be made up for with complex technology afterwards.
- Orientation of the building: prefer east and west!
It is still widely believed that solar generators are only effective on the south side of the roof. This view is outdated. It is better to align the solar panels to the west and east. The solar power yields are then better distributed over the course of the day. They fit better with the consumption peaks in the building, which usually occur in the morning and evening. Three solar fields are perfect: one to the east, one to the west and one to the south.
- Covered porch facing south!
If the house gets a flat roof, you can align the solar panels as you like. In the case of pitched roofs, solar fields are to be preferred to the east and west. Then the gable points to the south. There is a spacious veranda that can be covered with a solar roof made of double glass modules, for example. In the summer, the canopy provides cool shade and protection from violent thunderstorms. In winter, the sun is flatter in the sky, so it is not shaded by the canopy. Then it can radiate unhindered into the building and support the heating.
- The largest possible windows to the east and south!
In our latitudes, the roofs and outer walls to the west or northwest point to the so-called weather side. This is where most of the precipitation and winds come from. Therefore, you should plan large window areas, especially to the east (sunrise!) and to the south. South-facing glass fronts should definitely have a canopy so that the rooms do not overheat in summer.
The canopy can be built very well with glass-glass modules, as a simple post construction made of wood. A conservatory with solar modules as a roof is also useful and practical. Very important: the larger the transparent surfaces on the building, the better the thermal quality of the windows must be: at least triple glazing.
- Adapt the power of the solar generators to your own power requirements!
When planning the photovoltaic system, the size of the roof is not so important. It is much more important to first know your own electricity requirements: the number of kilowatt hours and how they are distributed throughout the day. Then you can precisely design the solar power system. A smartly planned solar generator can keep users powered well into the fall, starting from March. For the winter months you always have to reckon with an additional power source, which photovoltaics cannot do in our latitudes.
- Rules of thumb for proper solar generators
Four solar modules (60 cells) produce at least one kilowatt of solar power, which corresponds to a roof area of around six square meters. Over the course of the year, they generate around 900 to 1,100 kilowatt hours of solar power, but it should never be less than 900 kilowatt hours. Because the usable solar radiation in our latitudes is 900 to 1,100 hours, depending on the region. In the Alps, the yields are sometimes 20 to 30 percent higher because the strong winter sun, reflecting snow and the clear air at higher altitudes improve the electricity yield. With the new high-performance modules, you can even install 1.2 kilowatts from four standard modules, with correspondingly higher yields. For six kilowatts (6,000 kilowatt hours) you need between 30 and 36 square meters of roof area.
- Prepare hot water electrically if possible!
In order to optimally supply a house with solar power, you have to consider a few things when it comes to energy use. Anyone who only needs a little hot water (kitchens, bathrooms, sauna) should provide all taps in the house with electric boilers or instantaneous water heaters. Instantaneous water heaters usually need high power for a short time, which is why boilers are better suited for the combination with photovoltaics. They are heated electrically when the solar generators offer sufficient solar power and keep the warm water available for a long time.
Even a family of four can nowadays supply hot water very economically with class A (and better) efficiency devices. Because they run on solar power from their own roof for as long as possible. Only when the sun is no longer sufficient in autumn are they supplied with green electricity from the grid. The technical and hydraulic effort is much lower than with thermal systems with gas burners or solar heat collectors (thermal collectors).
And: water hygiene is improved because the boilers are usually installed directly at the tap. At the tap, 44 degrees Celsius is completely sufficient, at this temperature even the most stubborn kitchen fat dissolves. Long pipe routes are no longer necessary, which reduces energy losses in the hot water pipes and the risk of dangerous germs multiplying. With electrical systems, you can also react very well to changes in demand. Because this need depends primarily on the residents of a house and their demands for hot water convenience. And sometimes the house is full: with friends, with children and grandchildren or other guests.
- Thermal heat: Drive the heat pump with solar power!
In a new building, the client also has the opportunity to adapt the heating system precisely to his needs. In principle, there are two phases in the year in which the heating of the rooms plays a role. In summer and in the warm weeks in spring and autumn there is no heating, the heating stays off. In the transitional period, a certain amount of heat is required to keep the room at a comfortable temperature. The heating system is only really needed in the cold weeks. Crunchy sub-zero temperatures usually only occur for a few days in our latitudes
Since electrical heating systems are still very expensive, a hermaphrodite is recommended: Heat pumps use electricity to compress the thermal potential in the outside air, the ground or the groundwater and bring it to usable temperatures. Here, too, it makes sense to generate the pump power using the solar generator on your own roof.
First of all, it is crucial that the house is properly insulated. The heating requirement depends on how high the heat losses through the outer walls, the roof and the basement (if any) are. The heating technology must also compensate for heat losses through ventilation.
In general, air heat pumps are the first choice because they are very inexpensive to buy and easy to install. If more heat output is required (apartment building), geothermal heat pumps are used. As long as sufficient solar power is available from the roof, it can drive the heat pump. Otherwise, green electricity from the grid is used.
8. Prefer German components and devices!
German manufacturers are to be given preference for the solar generator and its components: solar panels, wiring, solar inverter, power storage devices (solar batteries) and supply technology devices (hot water, heating). Not that foreign companies are unable to properly build such devices. But German providers usually have better service in the event of complaints or damage. Sure, sometimes German products are more expensive than the competition from the Far East. But if you buy cheap, you usually buy twice.
- Leave the installation to the tradesman!
It is essential that the components and devices are installed by specialist tradesmen. The installers and system planners are familiar with meteorological and regional peculiarities, and have often already built similar off grid solar systems and equipped houses.
Most importantly, the installer should be consulted during the building design phase. Architects usually don’t like that, but the architect won’t pay your electricity and heat bills afterwards either.