ᐅ Pellets combined with solar thermal or photovoltaic systems?

Hello everyone,

I am currently facing a small issue with planning the heating system.

A pellet stove with about 12 kW output is firmly planned. However, it should be supported by solar energy.

The question now is which option makes more sense...
1. Support from solar thermal system
2. Photovoltaics with an electric immersion heater in the buffer tank

Details:
Floor area about 175 sqm (1887 sq ft)
Building style: urban villa with basement
KfW 55 standard
Ventilation with heat recovery
Underfloor heating throughout the house
Orientation: south (10 m (33 ft) roof width facing south)
Roof pitch about 23°

The question is also which combination is best for subsidies/grants.

Thank you very much

Well, this is a bit of a tricky issue in this case...

In general, solar thermal systems are not cost-effective.

However, with a pellet heating system, I would still consider it, since solid fuel heating systems handle cycling the worst. During transitional seasons or summer, you could turn off the heating for many days (if you control it manually or with good automation). This benefits the longevity of the heating system. It also reduces soiling and improves average efficiency.

So yes, in my opinion, three solar thermal modules make sense for a pellet heating system. And of course, add as much photovoltaic as possible. But that is unrelated to the heating system.

Thank you for the assessment.

I had the cycling in mind as well, which is why I planned for the support.

I would either go for photovoltaic panels or solar thermal. The photovoltaic would supply an electric heating element in the buffer tank to reduce the pellet heating load during summer.

Does this make sense, or is it complete nonsense?

It certainly isn’t complete nonsense. It’s just less efficient than transferring the heat directly into the storage.

On the other hand, using electricity gives you more flexibility, and when the storage is heated, you can use the excess elsewhere, sell it, or even store it later.

Since you will probably switch to heat pumps eventually anyway (my crystal ball says so clearly ), photovoltaics will also benefit you then.

So if you don’t want both, go for photovoltaics.

Has anyone calculated this with a heating capacity of 12 kW? That seems like a very high rating given the basic data, doesn’t it?

I would also like to have this glass dome.

There is definitely no heat pump planned.

The photovoltaic system is more flexible, that's true, but it is also not as efficient (efficiency, etc.).