Hello
First, let me briefly introduce myself. My name is Julian, and I’m from the beautiful Saarland region. Since my partner and I are gradually thinking about buying a home and gathering some ideas, I have a few questions.
We are planning to build a single-family house with a living area of 160 m² (1,722 sq ft). Now the question is how to save money despite rising energy and heating costs.
Now to my main idea:
I would build a house with a large solar thermal system and a photovoltaic system. Inside the house, there would be a large water storage tank with a capacity of about 20–30 cubic meters (7,057–10,594 cubic feet). I would use the solar thermal system to heat the water in the storage tank to provide domestic hot water. Additionally, I could use the stored heat to warm the house in winter through underfloor heating. For very cold winters, I would also install a large wood-burning stove. This stove might have an integrated heat exchanger to heat water as well. Do you think such a setup could work without any additional heating system? What would the approximate cost be? I have also been considering installing an automatic ventilation system to prevent mold and other issues in a highly insulated house.
What do you think? Feasible or a rather unrealistic idea?
First, let me briefly introduce myself. My name is Julian, and I’m from the beautiful Saarland region. Since my partner and I are gradually thinking about buying a home and gathering some ideas, I have a few questions.
We are planning to build a single-family house with a living area of 160 m² (1,722 sq ft). Now the question is how to save money despite rising energy and heating costs.
Now to my main idea:
I would build a house with a large solar thermal system and a photovoltaic system. Inside the house, there would be a large water storage tank with a capacity of about 20–30 cubic meters (7,057–10,594 cubic feet). I would use the solar thermal system to heat the water in the storage tank to provide domestic hot water. Additionally, I could use the stored heat to warm the house in winter through underfloor heating. For very cold winters, I would also install a large wood-burning stove. This stove might have an integrated heat exchanger to heat water as well. Do you think such a setup could work without any additional heating system? What would the approximate cost be? I have also been considering installing an automatic ventilation system to prevent mold and other issues in a highly insulated house.
What do you think? Feasible or a rather unrealistic idea?
T
Thomas46315 May 2012 21:32Hello,
so forget the idea of a 20-30m³ (700-1,060 cubic feet) storage tank quickly. The size of the buffer tank and the required area of solar panels is determined by the number of household members.
If the solar system is also intended for heating, your house must have at least a low-energy standard (airtightness, very good thermal insulation, high-quality glazing and window frames, etc.), or even better, passive house standard.
What I would recommend:
a) Low-energy house:
The possible heat sources are:
1.) Solar panels: For hot water and possibly also for heating as a supplement to other energy sources. Alone, they are not sufficient for heating!
2.) Surface or deep collectors for geothermal energy utilization
3.) Heat pump to boost the energy gained from 1. and 2.
Here, we are talking about low-temperature systems because the heating temperature is only slightly higher than the desired room temperature (compared to radiators, which can reach 70-80°C (158-176°F)).
As distribution systems for low-energy standard:
1.) Wall and/or underfloor heating
2.) Controlled mechanical ventilation with heat recovery
Now an explanation:
With deep or surface collectors, pipes are either laid horizontally in the ground (surface collector) — sometimes several hundred meters distributed over a large area — or, as with a well, vertically at great depth (>80m (260 feet), depending on the requirement), only a few pipes (usually 2 circuits) go into a small borehole. Deep collectors have the advantage of requiring much less ground area compared to surface collectors, but you can read about all of this on Wikipedia or similar if interested.
These collectors extract a fairly constant temperature level from the ground throughout the year. However, this temperature level is still too low for heating and must be raised to a usable temperature level by a heat pump.
The heat pump works like a refrigerator: A compressor compresses a gas, which heats up in this area. This temperature can be transferred via a heat exchanger to, for example, an underfloor heating system. The water that has passed through the floors to be heated then returns cooler because it has released heat to the room. This cooler water cools the warm side of the heat pump again (and the cycle repeats). The cooler gas inside the heat pump, which is still compressed, then passes through an expansion valve (the opposite of compression), cooling down even more than before. At this point, the cold side of the heat pump absorbs the warmed-up energy level from the deep or surface collector, and through compression, it becomes usable again, restarting the heat pump cycle. The cooled medium from the collector (usually a brine solution — saltwater) is pumped through the pipes and continuously absorbs more heat from the ground or groundwater, arriving warm again at the heat pump.
I know it’s difficult to describe this in writing, but there are several videos on YouTube explaining the principle.
The solar collectors themselves mainly heat the water for the domestic hot water circuit for cooking, washing, etc., which is why the number of occupants is the main factor in sizing them.
In a passive house, you can realistically only use controlled mechanical ventilation as a distribution system because you send the “old” warm exhaust air through a heat exchanger before it leaves the house so the heat energy is transferred to the cold fresh air and warms it up. Of course, 100% heat recovery is not possible, but since the occupants also release heat (cooking, sweating, etc.), and geothermal energy plus the heat pump still provide heating, this is enough to maintain the temperature level in the house effortlessly. Additionally, there is always fresh air inside the house as it is regularly and automatically replaced, and the system also works in summer to cool the house like an energy-efficient air conditioner.
To distinguish a passive house from a low-energy house, you also need photovoltaic panels to cover the energy demand of the system, as well as somewhat better insulation and at least triple-glazed windows.
The actual calculation and dimensioning of the system should be done by a professional (who is experienced with these systems). Cost-wise, you should expect an additional expense of about €25,000-35,000 (approximately $27,000-38,000) over a low-energy standard house compared to a standard house. The passive house will cost somewhat more due to the photovoltaic system, etc.
However, it should be noted: these systems generally pay off after about 15 years (assuming stable energy prices). Considering the increasing costs of fossil fuels or electricity, the payback period could be even shorter.
If I got anything mixed up or if you don’t understand something, feel free to ask.
But please forget the idea of a 20-30m³ (700-1,060 cubic feet) storage tank quickly — such a huge storage volume is needed, and I can think of many more reasons against it that would quickly kill the project (costs for storage, structural implementation, and much more). Stick to the “conventional” building methods, which have long proven themselves and are well thought out.
Best regards,
Thomas463
so forget the idea of a 20-30m³ (700-1,060 cubic feet) storage tank quickly. The size of the buffer tank and the required area of solar panels is determined by the number of household members.
If the solar system is also intended for heating, your house must have at least a low-energy standard (airtightness, very good thermal insulation, high-quality glazing and window frames, etc.), or even better, passive house standard.
What I would recommend:
a) Low-energy house:
The possible heat sources are:
1.) Solar panels: For hot water and possibly also for heating as a supplement to other energy sources. Alone, they are not sufficient for heating!
2.) Surface or deep collectors for geothermal energy utilization
3.) Heat pump to boost the energy gained from 1. and 2.
Here, we are talking about low-temperature systems because the heating temperature is only slightly higher than the desired room temperature (compared to radiators, which can reach 70-80°C (158-176°F)).
As distribution systems for low-energy standard:
1.) Wall and/or underfloor heating
2.) Controlled mechanical ventilation with heat recovery
Now an explanation:
With deep or surface collectors, pipes are either laid horizontally in the ground (surface collector) — sometimes several hundred meters distributed over a large area — or, as with a well, vertically at great depth (>80m (260 feet), depending on the requirement), only a few pipes (usually 2 circuits) go into a small borehole. Deep collectors have the advantage of requiring much less ground area compared to surface collectors, but you can read about all of this on Wikipedia or similar if interested.
These collectors extract a fairly constant temperature level from the ground throughout the year. However, this temperature level is still too low for heating and must be raised to a usable temperature level by a heat pump.
The heat pump works like a refrigerator: A compressor compresses a gas, which heats up in this area. This temperature can be transferred via a heat exchanger to, for example, an underfloor heating system. The water that has passed through the floors to be heated then returns cooler because it has released heat to the room. This cooler water cools the warm side of the heat pump again (and the cycle repeats). The cooler gas inside the heat pump, which is still compressed, then passes through an expansion valve (the opposite of compression), cooling down even more than before. At this point, the cold side of the heat pump absorbs the warmed-up energy level from the deep or surface collector, and through compression, it becomes usable again, restarting the heat pump cycle. The cooled medium from the collector (usually a brine solution — saltwater) is pumped through the pipes and continuously absorbs more heat from the ground or groundwater, arriving warm again at the heat pump.
I know it’s difficult to describe this in writing, but there are several videos on YouTube explaining the principle.
The solar collectors themselves mainly heat the water for the domestic hot water circuit for cooking, washing, etc., which is why the number of occupants is the main factor in sizing them.
In a passive house, you can realistically only use controlled mechanical ventilation as a distribution system because you send the “old” warm exhaust air through a heat exchanger before it leaves the house so the heat energy is transferred to the cold fresh air and warms it up. Of course, 100% heat recovery is not possible, but since the occupants also release heat (cooking, sweating, etc.), and geothermal energy plus the heat pump still provide heating, this is enough to maintain the temperature level in the house effortlessly. Additionally, there is always fresh air inside the house as it is regularly and automatically replaced, and the system also works in summer to cool the house like an energy-efficient air conditioner.
To distinguish a passive house from a low-energy house, you also need photovoltaic panels to cover the energy demand of the system, as well as somewhat better insulation and at least triple-glazed windows.
The actual calculation and dimensioning of the system should be done by a professional (who is experienced with these systems). Cost-wise, you should expect an additional expense of about €25,000-35,000 (approximately $27,000-38,000) over a low-energy standard house compared to a standard house. The passive house will cost somewhat more due to the photovoltaic system, etc.
However, it should be noted: these systems generally pay off after about 15 years (assuming stable energy prices). Considering the increasing costs of fossil fuels or electricity, the payback period could be even shorter.
If I got anything mixed up or if you don’t understand something, feel free to ask.
But please forget the idea of a 20-30m³ (700-1,060 cubic feet) storage tank quickly — such a huge storage volume is needed, and I can think of many more reasons against it that would quickly kill the project (costs for storage, structural implementation, and much more). Stick to the “conventional” building methods, which have long proven themselves and are well thought out.
Best regards,
Thomas463
Hello Thomas, thanks for the detailed response.
My issue with the geothermal heating system is that I would need to have a borehole drilled on my property. How is groundwater or rock layers handled in these drilling processes? Could this cause problems, or do they simply drill through?
I actually want to work as energy self-sufficient as possible. The less energy I need for heating, the less I have to pay. That’s clear. The photovoltaic system would have to be quite large to cover the consumption of the geothermal heating and ventilation system.
I need to take a closer look at the passive house standard.
My issue with the geothermal heating system is that I would need to have a borehole drilled on my property. How is groundwater or rock layers handled in these drilling processes? Could this cause problems, or do they simply drill through?
I actually want to work as energy self-sufficient as possible. The less energy I need for heating, the less I have to pay. That’s clear. The photovoltaic system would have to be quite large to cover the consumption of the geothermal heating and ventilation system.
I need to take a closer look at the passive house standard.
Hello,
Alternatively, an air source heat pump (ASHP) could be considered, depending on the building’s size and insulation standard.
The combination of a heat pump and photovoltaic (PV) system is currently one of the most cost-effective solutions.
The truth can be found through a basic assessment of actual demand and consumption (capacity, energy) for heating, domestic hot water (DHW), and possibly ventilation.
Best regards
Culli schrieb:There are various sources for ground source heat pumps (GSHP): vertical boreholes, surface collectors, geothermal baskets, trench collectors, as well as collectors that require neither digging nor drilling. Each has its advantages and disadvantages. For GSHP as a heat source, excessive insulation usually isn’t cost-effective. If you focus more on achieving a very low heat transfer coefficient (HT value, as in passive houses), a GSHP is often like “using a sledgehammer to crack a nut.”
...My problem with the geothermal heat pump is that I would need to have a borehole drilled on my property. How is groundwater and rock layers handled during these drillings? Could this cause problems, or do they just drill right through?
Alternatively, an air source heat pump (ASHP) could be considered, depending on the building’s size and insulation standard.
The combination of a heat pump and photovoltaic (PV) system is currently one of the most cost-effective solutions.
Culli schrieb:Savings on future energy costs involve substitution through investment or its financing costs. Not everything that is heavily advertised turns out to be economically viable.
... The less energy I need for heating, the less I have to pay. That’s clear.
The truth can be found through a basic assessment of actual demand and consumption (capacity, energy) for heating, domestic hot water (DHW), and possibly ventilation.
Culli schrieb:That’s a misconception. Even standard buildings, depending on location and orientation, can balance this on an annual basis.
... I’d need a very large photovoltaic system to compensate for the consumption of the geothermal heat pump and ventilation system.
Best regards
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