“7 MW solar heat plants will be a commodity in Europe in 5 to 10 years”
 “7 MW solar heat plants will be a commodity in Europe in 5 to 10 years”

“7 MW solar heat plants will be a commodity in Europe in 5 to 10 years”

Viessmann, a major German provider of climate solutions for living spaces, strengthened its project development team last year, hiring Christian Stadler and four of his ex-colleagues in June 2020, after their former employer, Danish-based Arcon-Sunmark, stopped operation. As part of Viessmann, Stadler and his team are now responding to district developers and utilities’ rising interest in low-carbon energy solutions and expect the first contracts to follow later this year.
Photo: Viessmann
In June 2020, you became the head of Viessmann’s business unit overseeing large solar thermal projects. How is your new job?
Stadler: We had a great start and were able to continue our work in the solar district heating market seamlessly. Combined, my four colleagues and I possess a great deal of expertise in project design, planning and implementation. One of Viessmann’s big advantages is that it has already partnered with companies offering heating solutions to commercial clients in housing, industry, trade and energy. This gives us a great opportunity to support these businesses via additional engineering capacity. We design systems that range from 500 to several thousand square metres and provide turnkey deliveries in collaboration with our partners.
Do you offer these services worldwide?
Stadler: Our focus is on Europe. There’s great interest in our solutions not only in Germany but also in the Netherlands and in France. Overall, Eastern European countries have potential for solar heat solutions as well. But coal dominates the heating sector there and is extremely cheap. That could change if the EU introduces a carbon price too.
What role does the new carbon tax in Germany play in increasing demand for solar heat solutions?
Stadler: The launch of the first carbon pricing phase in Germany, at 25 EUR per tonne of CO2, garnered little public attention because of all the reporting on the pandemic. But it has had a clear impact. For example, the housing industry, is acutely aware that it needs to reduce these additional tax costs, whereas utilities pass those costs on to customers.
Generally speaking, a carbon price on heating fuel is an ideal decarbonisation policy. It doesn’t prevent competition between renewable technologies but sets the right goal.
How about the Danish solar district heating market, Arcon-Sunmark’s cash cow over the last years?
Stadler: The Danish solar district heating market is suffering under an unfavourable political climate. Three years ago, the government implemented a heat pump subsidy – in an energy market previously regulated mainly by high taxes on oil and gas. Recently, this has caused a rush on heat pumps, mainly by municipal utilities. Together with the back-and-forth between energy companies and the Danish energy ministry regarding the energy savings agreement, it therefore became essentially impossible to do a continuous business in the solar district heat sector.
Where do you see your business unit in 5 years?
Stadler: We don’t have specific, far-reaching aims. But I’m sure that in 5 to 10 years, 7 MWth solar heat plants will be a commodity in Europe. Germany shows what a growth rate looks like in this market and might be five years ahead of other countries in Europe, which will eventually follow the same trajectory. We will see both large ground-mounted installations and smaller rooftop fields in industry and neighbourhoods.
Our great advantage is that Viessmann offers a wide variety of heating technologies inhouse, so we can provide commercial clients with solutions meeting 100 % of their heating demand by combining biomass boilers or CHP plants and solar heat. Viessmann has already had great success with this approach in the solar-bioenergy villages in Germany.
This 200 kWth solar thermal system was installed horizontally on the flat roof of a vocational training center in the zero-emission ZeoZweiFrei neighbourhood in Ettlingen, southern Germany. Together with a biomass boiler (2 MWth) and a two pellet boilers (totalling at 1,79 MWth) it forms a zero-emission heating system. The new large vacuum tube collectors made by Viessmann can be installed at an angle of only 3°.
Photo: Thomas A. Berger
Viessman has introduced a large vacuum tube collector measuring 5 m2 or 10 m2. What is the target application?
Stadler: An important feature of the new heat pipe vacuum tube collector is that it can be installed horizontally. We can mount the large collector units onto a flat roof at an angle as small as 3°. This was not possible so far with heat pipe vacuum tube collectors. To reach this we optimised not only the amount of fluid in the heat pipe but also the design of the tube and the heat transfer header. The benefits are clear: horizontal mounting leads to lower costs and wind loads. Consequently, there is also less weight, which is of great importance especially when using roofs of industrial halls, as they often have lower strength and stability requirements than the roofs of blocks of flats.
Interview conducted by Bärbel Epp

Baerbel Epp

Bärbel Epp is Founder and Director of the German communication and market research agency solrico and editor-in-chief of solarthermalworld.org