SEPP STEINMÜLLER: The idea for a solar system actually came to me from a different angle; it all started with my idea for a hay drying system, which I knew would require a lot of electricity. At the same time, the roof over the barn was damaged and needed replacing. From there, the plan quickly took shape to build a solar system as part of the roof renovation, which would then enable me to generate affordable electricity myself for the hay drying system and manage peaks in electricity consumption.

SEPP STEINMÜLLER: With my farm’s own hay drying system, hay that is pre-dried in the meadows can be finished off on the farm. You need to know that it is very difficult to achieve good hay quality by drying it out in the field. The grass needs to be mown later in the season so that it dries properly, and then it should ideally be left to dry outdoors for three days. By the third day, however – partly due to night-time dew – you’ve already lost around twenty per cent of the most valuable nutrients: energy, protein and vitamins. Valuable components of herbs are also lost.

If the hay is brought in ‘semi-moist’ on the second day and further dried in the barn using a hay drying system, the most valuable nutrients are still present in the hay. This brings significant benefits for animal health. It is, of course, important to operate the hay drying system as economically as possible, as it requires a high amount of electricity and heat.

SEPP STEINMÜLLER: Exactly, the solar system is used in combination and is therefore designed as an in-roof system, so that the warm air underneath can be extracted as completely as possible, which would be very difficult with a roof-mounted system. The in-roof solar system acts as an effective hot-air collector; the hot-air extraction also benefits the solar system, as it cools it down and boosts its output. And I’ll also have the free heat from the system for hay drying on days when the weather is fine.

SEPP STEINMÜLLER: The hay drying system in conjunction with the solar system required a great deal of planning, for which I was supported by Mr Huber from HUBER. One of the challenges was how to efficiently extract the majority of the air. I will also need a way to cool the system on days when the hay drying system is not running. Essentially, the warm air beneath the in-roof system will be drawn in through a ventilation ridge and channelled downwards into a large collection duct, from where it can be blown through the haystack in a concentrated stream. When the system is not in operation, there will be large ventilation flaps through which cooler outside air can flow in – a form of passive ventilation by convection, so to speak.

SEPP STEINMÜLLER: Exactly. I first looked into the cost-effectiveness of solar systems for my business: how much does such a system cost, what return on investment can I achieve, and where might there be problems. I then obtained several quotes, but these were all for rooftop systems. The suppliers all advised me against in-roof systems.

SEPP STEINMÜLLER: The suppliers of solar and PV systems are usually specialist electrical firms; from a trade perspective, they have no way of accessing the roof structure, so for such firms, a rooftop system is the only option.

But from the outset, it didn’t make sense to me why an in-roof system wouldn’t work; after all, it’s essentially a larger skylight that’s properly connected. I then set about looking for a solution, eventually came across the Solrif mounting system, and got in touch with Ernst Schweizer Metallbau AG. Together, we looked for a specialist firm that could sell and install the system for me. Ernst Schweizer Metallbau AG recommended HUBER to me.

SEPP STEINMÜLLER: Exactly, and I actually quite liked the way things went – having the specialist firm that builds the frames recommend another specialist firm with whom qualified cooperation can be expected. I found that very reassuring and it made it easier to build trust.

SEPP STEINMÜLLER: Ernst Schweizer Metallbau AG sent a specialist to assist with the installation, for which I was very grateful, as it demonstrates their interest in my project.

SEPP STEINMÜLLER: The Axsun solar modules were recommended to me by HUBER. Axsun works in partnership with Ernst Schweizer Metallbau AG by simply replacing the frame of their modules with a special frame that fits into the Solrif mounting system. I also liked the fact that Axsun manufactures in Germany. I always prefer German products whenever possible.

SEPP STEINMÜLLER: There was actually the option of using special glass-glass modules and applying an additional special coating to them, which might have resulted in even higher heat output, but I didn’t feel that extra performance was worth the extra cost. I’ve got modules that offer good value for money, so I didn’t want to add to the cost just to ensure the system’s cost-effectiveness.

SEPP STEINMÜLLER: The system has been in operation since late July or early August and has now produced around 6,000 kWh of electricity in the first two months, which is exactly on schedule. I think I’ll reach the planned annual yield this way. I’ll be able to give more precise figures after a year.

SEPP STEINMÜLLER: Not yet; installing the system was very labour-intensive, as we did a great deal of the work on the rest of the roof ourselves, which was quite stressful. I was just glad that phase was over. We haven’t managed to set up the portal yet – the final bit – but we’ll get round to that in the coming weeks.

SEPP STEINMÜLLER: The entire roof renovation was a massive project for us; you really have to stay on the ball to ensure everything runs smoothly and that all the components are coordinated. The ventilation ridge was installed by a specialist firm, and thanks to the good communication with HUBER Dachtechnik, it quickly became clear exactly how the roof connections needed to be configured.

I’d also like to mention the collaboration with HUBER during the planning phase; it was very pleasant, and it was ultimately decisive in HUBER being awarded the contract for the build, as the other solar installers simply weren’t prepared to put so much planning work into the project; they tended to get cold feet about the planned project and perhaps didn’t have the expertise or the willingness to try something new. And Mr Huber was very willing to invest time and energy and to implement the project for the in-roof solar system with hot air extraction for the hay drying system exactly as I had envisaged. There were also some great people from HUBER there who really know their stuff, and it’s simply a pleasure when the boss is always on hand. The entire construction project was completed relatively quickly, despite its size and complexity.

Mr Steinmüller, thank you very much for speaking to us.