Hi,
I would like to gather a few more opinions on the pros and cons of solar thermal collectors supporting heating in combination with a gas condensing boiler.
Some background information:
The house faces south and is located in the mild and sunny Rhine valley with no shading, approximately 160 sqm (1,722 sq ft) of living space. No underfloor heating is planned in the living areas. The walls are made of 24 cm (9.5 inches) Ytong blocks without insulation, but very good (new) windows and doors will be installed. Roof insulation will also be added.
The (NOT independent) energy consultant advised against it. His reasoning: when heating is needed, there is usually no sun or not enough sunlight—his opinion is that the maximum annual savings (under ideal year-round weather conditions, etc.) would be about 80–100 € (~$85–$105), which does not justify the investment costs. He suggests only supporting domestic hot water.
Sanitary company A had the opposite view. Heating support is the only way to go; the investment cost would be moderate since you can also get funding from BAFA. Their plan includes a buffer tank of around 500–600 liters (132–158 gallons) and domestic hot water on a flow-through system.
Sanitary company B said roughly the same as the energy consultant and stated that at least an 800-liter (211 gallons) tank would be necessary (which is very expensive) and recommended only domestic hot water support.
Sanitary company C could not or would not give a clear recommendation. They warned about the costs of heating support (around 10,000 €), said they had installed it in their own house and generally recommend it, but ultimately suggested that only domestic hot water support might be more reasonable.
The detailed offers with cost breakdowns will be sent to me by the companies in the next few days.
So, what do you think?
Regards
I would like to gather a few more opinions on the pros and cons of solar thermal collectors supporting heating in combination with a gas condensing boiler.
Some background information:
The house faces south and is located in the mild and sunny Rhine valley with no shading, approximately 160 sqm (1,722 sq ft) of living space. No underfloor heating is planned in the living areas. The walls are made of 24 cm (9.5 inches) Ytong blocks without insulation, but very good (new) windows and doors will be installed. Roof insulation will also be added.
The (NOT independent) energy consultant advised against it. His reasoning: when heating is needed, there is usually no sun or not enough sunlight—his opinion is that the maximum annual savings (under ideal year-round weather conditions, etc.) would be about 80–100 € (~$85–$105), which does not justify the investment costs. He suggests only supporting domestic hot water.
Sanitary company A had the opposite view. Heating support is the only way to go; the investment cost would be moderate since you can also get funding from BAFA. Their plan includes a buffer tank of around 500–600 liters (132–158 gallons) and domestic hot water on a flow-through system.
Sanitary company B said roughly the same as the energy consultant and stated that at least an 800-liter (211 gallons) tank would be necessary (which is very expensive) and recommended only domestic hot water support.
Sanitary company C could not or would not give a clear recommendation. They warned about the costs of heating support (around 10,000 €), said they had installed it in their own house and generally recommend it, but ultimately suggested that only domestic hot water support might be more reasonable.
The detailed offers with cost breakdowns will be sent to me by the companies in the next few days.
So, what do you think?
Regards
L
laien.haft20 Feb 2014 15:30baweng schrieb:
Oh yes, new radiators will be installed as well: Kermi x2The return water temperatures will still be significantly higher than with underfloor heating systems. So, the situation remains unchanged.
laien.haft schrieb:
...a solar thermal system for domestic hot water pays off quite quickly.... Is that an assumption, or can you provide verifiable yields here with a heat meter?laien.haft schrieb:
...The return temperatures of conventional radiators do not contribute to the efficient operation of the solar system. Please provide a technically sound reference to support this claim!Best regards
L
laien.haft20 Feb 2014 17:05Amortization:
The system efficiency of a solar domestic hot water system is generally undisputedly higher than that of a solar system supporting space heating. Solar systems for space heating support are usually designed for the transition seasons. In summer, these systems inevitably go into stagnation (there are numerous publications on this topic; if you need a source, you can find them on the websites of relevant institutes – especially from ISE, ISFH, or SPF).
From experience, I would estimate a specific collector yield of about 350 kWh per m² per year (350 kWh/m²/a) for a well-designed solar system supporting space heating, and about 450 kWh per m² per year (450 kWh/m²/a) for a well-designed domestic hot water system.
Of course, anyone interested in solar thermal energy should carry out (or have someone carry out) a case-specific calculation.
The fact that a “smaller system” may be more financially worthwhile is, in my opinion, not the main point of your question.
Return temperatures:
There are numerous studies on the influence of return temperatures on solar coverage ratios or system efficiency (especially in the field of solar-supported local heating networks) (Szablinski, 2004).
There are certainly some methods to reduce return temperatures in conventional radiators, but no miracles can be expected.
In general, it can be said that high return temperatures reduce the efficiency of solar thermal systems.
To analyze this precisely, all details need to be considered. I believe that is the intention of €uro. He is right. Nevertheless, I would still recommend a domestic hot water system.
The system efficiency of a solar domestic hot water system is generally undisputedly higher than that of a solar system supporting space heating. Solar systems for space heating support are usually designed for the transition seasons. In summer, these systems inevitably go into stagnation (there are numerous publications on this topic; if you need a source, you can find them on the websites of relevant institutes – especially from ISE, ISFH, or SPF).
From experience, I would estimate a specific collector yield of about 350 kWh per m² per year (350 kWh/m²/a) for a well-designed solar system supporting space heating, and about 450 kWh per m² per year (450 kWh/m²/a) for a well-designed domestic hot water system.
Of course, anyone interested in solar thermal energy should carry out (or have someone carry out) a case-specific calculation.
The fact that a “smaller system” may be more financially worthwhile is, in my opinion, not the main point of your question.
Return temperatures:
There are numerous studies on the influence of return temperatures on solar coverage ratios or system efficiency (especially in the field of solar-supported local heating networks) (Szablinski, 2004).
There are certainly some methods to reduce return temperatures in conventional radiators, but no miracles can be expected.
In general, it can be said that high return temperatures reduce the efficiency of solar thermal systems.
To analyze this precisely, all details need to be considered. I believe that is the intention of €uro. He is right. Nevertheless, I would still recommend a domestic hot water system.
laien.haft schrieb:
...To really settle this precisely, all details need to be on the table. I believe that is the intention of €uro.... Correct, but usually the problem lies in the details! ;-) Best regards