The first heating season exceeds all expectations!

At the end of September 2021, the official opening of our new company building in Neuzeug, Upper Austria, took place. As a manufacturer of solar-electric building technology, it was clear to us that we will implement our own philosophy of photovoltaic heat at the new location. The 100 kWp photovoltaic system, which is mounted on our pent roof and in the facade of the building, provides massive energy excess that can be optimally used with the thermal storage mass in the building.

In the past, we have repeatedly shown that solar-electric building technology can be operated cost-efficient and sustainable way for single and multi-family houses. What is new is that photovoltaic heat now has significantly lower investment and operating costs in commercial properties compared to heat pumps. Of course, this concept is subject to a great deal of scepticism, especially in winter. However, fear is actually the only obstacle with regard to the change!

The first winter - an energy balance of the photovoltaic heat

 All energy quantities were recorded right from the start of the building's use with the aim to create a meaningful database for detailed evaluations. In addition to the grid connection point, appropriate measuring technology has also been installed for the photovoltaic system, the electric room heating, the hot water preparation, the ventilation and air conditioning system and the charging stations. These energy flows are displayed for all visitors and employees in the visualization of the building technology, in the foyer of the building.

The following figure shows a snapshot of an early morning at the beginning of May 2022. At this point in time, all requirements of the building are already overcompensated by the photovoltaics and energy is fed into the power grid.

 Figure 1. Visualization of the housing technology in the my-PV company building. Photo from 3.5.2022 at 8.45 a.m.

This data recording is the basis for the evaluation of the first heating season 2021/2022. The months November to April are considered. The energy requirements of the four sectors (electricity, heating, hot water and mobility), the energy source and the PV surplus are shown in Figure 2.

During these six months, around 3,600 kWh were used to charge the e-cars. This corresponds to the equivalent of 360 litres of diesel, which in turn corresponds to around six tank fillings. With one tank filling per month, one would normally speak of a below-average degree of mobility, but thanks to the high efficiency of electric vehicles, more than 20,000 km could be covered with this energy.

Approximately 17,400 kWh were used for the electric space heating. Here the energy-efficient construction standard becomes particularly evident. With a floor area of ​​858 m², this means that, in addition to the passive solar and internal gains, only 20 kWh per square meter were required to maintain a comfortable indoor climate!

The hot water requirement usually accounts for a marginal proportion of the heat supply in a commercial property. Although there is a shower for the employees, hot water consumption is usually limited to washing hands, which means that only 270 kWh of energy had to be supplied.

The regular amount of electricity includes not only the lighting, the production machines and the office equipment, but also the air conditioning and ventilation system. Approximately 11,350 kWh were used for these functions in the six months of winter.

Figure 2: Energy balance November 2021 to April 2022

More than half of the energy for these four sectors was generated on site thanks to the 100 kWp photovoltaic system! With a PV self-consumption of 17,344 kWh and a grid consumption of 15,251 kWh, this means a degree of self-sufficiency of 53.2% in winter!

It is particularly important to mention that the solar yields in the "problem months" of December and January fell short of the long-term averages and that self-sufficiency would be even higher in an average year. About 15,300 kWh could not be used on site and was therefore fed back into the public grid. This results in a PV self-consumption of 53.4%.

The grid balance is calculated by dividing the grid feed-in by the grid consumption. A grid balance of 100.3% demonstrates the high level of self-sufficiency as more energy was put in the grid than was actually consumed.

When considering purchased electricity and grid feed-in, it is noticeable that more electricity was fed into the grid in the period under review than was obtained by it. This means that the building is completely energy self-sufficient in winter. Hereby, we do not just consider the electrical consumers, but also always include heat and mobility in our evaluation.

With our solar-electric company building we have achieved what the Austrian government is striving for in terms of electrical energy until 2030 – namely self-sufficiency, even in the heating season and across all sectors (electricity, heat, mobility)!

Conclusion on the first heating season in the solar-electric company building

In the house of the future, everything is purely electric, mostly solar-electric. From now on, this also applies to heating in commercial properties. Compared to conventional building services with a heat pump, our company building had lower investment costs and even generated negative operating costs over the course of the year. In other words: As an operator, we get money back!

Heat generation that does not require any moving parts, is not only completely maintenance-free, but also completely silent. "Cables instead of pipes" simplify installation and operation. With the appropriate dimensioning of the photovoltaic system, the concept is clean and sustainable!