Solar with heating support

We have a 2-person household. Single-family house with 135 sqm usable area.

Gas boiler with solar support for domestic water heating. Two collectors Logasol SKN 4.0 with a total of 4.8 sqm area are used.

I can quite easily determine the costs for daily domestic water heating when the collector delivers no energy:
0.4 cubic meters of gas, corresponding to about 4.2 kWh or 0.3 Euro per day.

This is the maximum that the collector can save for us, minus the electricity costs for the circulation pump of the solar fluid of about 5 cents. Remaining savings of 0.25 Euro per day. Generously calculated for 200 days per year. Results in 50 Euros per year.

The investment costs can never be recovered over the lifetime of the system.

A vacuum flat tube collector would have brought significantly more yield, but it costs significantly more to purchase.

I think that support of the heating circuit also only has a minor effect or is poorly economical; however, it definitely requires a vacuum flat tube collector of corresponding size. Since every percent counts here, a pure south orientation is relevant. Due to the east orientation present in my case, I lose about 10% again; therefore, it was not worth considering installing/investing in it.

Regards
Thorsten

Great, finally showing the naked truth of the solar nonsense with simple, concise numbers.

Hi,

Whether the numbers from T21150 really fit, I cannot judge, but the order of magnitude will approximately fit.


We have a similarly sized house, gas plus 5 sqm solar thermal and need 8500 kWh gas per year. The heating system always roughly tells us how much solar support it has collected. No more than 10 kWh per day come in, even in summer. Simply because no more is used for showering etc. So let's generously say 1000 kWh for the whole year. That is then 50 €/year.


Sebastian is right, this is all total nonsense. Especially when you consider that the production of 1 kg of glass requires about 1300 kWh of energy. I really have no idea how much glass is installed there, but it will definitely take several years until these things even recover the energy that was used for production. If they manage it at all.


But since these things are now often manufactured somewhere in the Far East, that is baaaad CO2 from the baaaad Chinese, but we here are the great good ones who save so much CO2. And since the baaaaad CO2 from the baaaaad Chinese certainly does not cross the border, we can all enthusiastically pat ourselves on the back here for all the great things we do for the environment.


Lord; throw down some brains from heaven.!



Back to the topic:



The solar system actually serves less to really heat and more to get the gas condensing boiler approved


By far the cheapest heating system is a gas heating system without solar and without anything. Unfortunately, this is no longer approved in this country, which is not exactly lacking in nonsense. So the only alternatives left are gas heating with solar (4-5 sqm for domestic hot water support), which is still cheaper than a heat pump currently, or from next year a gas heating system with solar heating support (10-15 sqm). The latter will probably not be much different from a good heat pump with indoor installation.

From next year you will no longer have the option "gas heating together with solar domestic hot water support," or probably only with an extremely high insulation effort.


Best regards,


Andreas

Hi Andreas,

even with a different approach, you also arrive at the order of magnitude "50 Euro/year". That should be realistic.

You are also right: from 2016 onwards, the combination is over anyway.

Best regards
Thorsten

And then at most a gas condensing boiler with zeolite or huge solarpanels?

What nonsense...

Correct, Sebastian.

More or less: economic nonsense.

Apart from the passive house, in a modern building today, depending on volume/size, you still have a savings potential of 50-80 euros/month until zero. That only with exponentially increasing investment costs.

Capital costs money just like heating.
If you already have the capital and want to play: no problem. I would do that in that case, play. Unfortunately – I am not wealthy. But an ordinary person.........

Poorly insulated old buildings – I often see ads here in the newspaper with 200 - 450 kWh/sqm/a have more potential than the purely expensive tuning of already economical low-energy houses. The comparisons often happen via primary energy anyway...... which does not provide any information about real consumption and local costs for the builder.