Hello
We are building a KfW 70 house. We have a lot of window area, so the calculations showed that we need to take additional measures to meet the KfW 70 standard.
We decided against a ventilation system, but instead opted for extra panels on the roof, not only to supply hot water via collectors but also to support heating.
However, the 300-liter (79 gallons) tank has now been replaced by a 750-liter (198 gallons) water storage tank. That seems huuuuge! Does the tank’s capacity affect the calculations? I haven’t been able to reach the engineering firm yet to ask, so I wanted to get some input from the forum first.
We are building a KfW 70 house. We have a lot of window area, so the calculations showed that we need to take additional measures to meet the KfW 70 standard.
We decided against a ventilation system, but instead opted for extra panels on the roof, not only to supply hot water via collectors but also to support heating.
However, the 300-liter (79 gallons) tank has now been replaced by a 750-liter (198 gallons) water storage tank. That seems huuuuge! Does the tank’s capacity affect the calculations? I haven’t been able to reach the engineering firm yet to ask, so I wanted to get some input from the forum first.
P
perlenmann29 Sep 2013 10:23And in the other post, you mentioned the efficiency of the heat pump for domestic hot water production...
Surely, you always have hot water in summer without heating. But at what cost? What does your solar thermal system cost you (and please don’t forget the space required for a 750 liter (198 gallon) storage tank!)
When you then offset the saved hot water costs, THAT is inefficient.
Surely, you always have hot water in summer without heating. But at what cost? What does your solar thermal system cost you (and please don’t forget the space required for a 750 liter (198 gallon) storage tank!)
When you then offset the saved hot water costs, THAT is inefficient.
Explosiv schrieb:
.... When asked, everyone in my circle of acquaintances who uses solar thermal systems for domestic hot water reports that their heating is completely off during the warm season, yet they still have good hot water temperatures for showering in the morning...... That may well be true. How many kWh per year are actually generated from this?Basically, every kWh of fossil energy replaced by a solar thermal system is valuable, there is no doubt about that.
However, this does not necessarily mean it is economical for the operator.
Assuming a theoretical coverage of demand of 50%, the following savings result from the above demand and investment, approximately:
Gas condensing boiler => €102 per year (year) => 59 years
Air-source heat pump => €69 per year => 89 years
Ground-source heat pump => €54 per year => 111 years
I hardly believe that a solar thermal system will achieve such normative service lifetimes. Also considering interest costs, depreciation, inflation, as well as electricity costs for controls and circulation pump, economic viability for the operator is hardly to be expected.
I would therefore rather invest the necessary capital for a solar thermal system in improved building envelope insulation.
Best regards.
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