ᐅ Heating System Question for New Build KfW 70: Air Source Heat Pump + Solar, Ice Storage?
Created on: 24 Feb 2015 11:42
H
hiasl86Hello dear forum users!
We are currently planning a new build in southern Bavaria near the border with Salzburg. At the moment, we are looking for the right heating system for our home. We have a living area of about 140 sqm (1507 sq ft). We plan to build to KfW 70 standard (36 cm (14 inch) bricks with perlite filling).
What we definitely do not want is oil heating. Gas is also not an option for us since there is no connection available, and I do not want to have a gas tank buried in the garden. We also don’t really want a pellet heating system because of the required storage space.
We are actually leaning towards a heat pump. We initially wanted geothermal energy with a deep borehole (ground collectors are not feasible due to limited land area). We received an offer for the deep drilling, but to me, it seems very expensive (12,000 - 15,000 Euro). The problem is that the water management authority limits the drilling depth to 10 m (33 ft). This is partly because sulfate rock was found nearby at depths of 30–40 m (98–131 ft), and no drilling has been done directly in our neighborhood yet. The drilling company suggested drilling 9 times to 10 m (33 ft) as a safe option. The less certain option (1. due to permits and 2. because it is unclear how far you can actually drill) would be 4 times 23 m (75 ft).
Now we might consider switching to an air-to-water heat pump with solar support (for domestic hot water and heating assistance). What do you think about this combination? How effective is it and what about electricity consumption? How well do air-to-water heat pumps perform in winter on very cold days? What investment costs should we expect roughly?
We also came across the solar heat pump system, combining solar, air, heat pump, and ice storage. Has anyone had experience with such a system? How does it perform in winter? Is it possible that you might end up heating only with electricity if the ice storage freezes too early and cannot thaw quickly enough, or is the solar and air energy usually sufficient? What about investment costs—how much higher are they compared to the solar plus air-to-water heat pump version?
I have browsed quite a few forums looking for answers and experiences with ice storage. Opinions seem quite divided (too early freezing, not cost-effective due to high investment costs).
Thank you in advance for your help and advice!
Best regards
Matthias
We are currently planning a new build in southern Bavaria near the border with Salzburg. At the moment, we are looking for the right heating system for our home. We have a living area of about 140 sqm (1507 sq ft). We plan to build to KfW 70 standard (36 cm (14 inch) bricks with perlite filling).
What we definitely do not want is oil heating. Gas is also not an option for us since there is no connection available, and I do not want to have a gas tank buried in the garden. We also don’t really want a pellet heating system because of the required storage space.
We are actually leaning towards a heat pump. We initially wanted geothermal energy with a deep borehole (ground collectors are not feasible due to limited land area). We received an offer for the deep drilling, but to me, it seems very expensive (12,000 - 15,000 Euro). The problem is that the water management authority limits the drilling depth to 10 m (33 ft). This is partly because sulfate rock was found nearby at depths of 30–40 m (98–131 ft), and no drilling has been done directly in our neighborhood yet. The drilling company suggested drilling 9 times to 10 m (33 ft) as a safe option. The less certain option (1. due to permits and 2. because it is unclear how far you can actually drill) would be 4 times 23 m (75 ft).
Now we might consider switching to an air-to-water heat pump with solar support (for domestic hot water and heating assistance). What do you think about this combination? How effective is it and what about electricity consumption? How well do air-to-water heat pumps perform in winter on very cold days? What investment costs should we expect roughly?
We also came across the solar heat pump system, combining solar, air, heat pump, and ice storage. Has anyone had experience with such a system? How does it perform in winter? Is it possible that you might end up heating only with electricity if the ice storage freezes too early and cannot thaw quickly enough, or is the solar and air energy usually sufficient? What about investment costs—how much higher are they compared to the solar plus air-to-water heat pump version?
I have browsed quite a few forums looking for answers and experiences with ice storage. Opinions seem quite divided (too early freezing, not cost-effective due to high investment costs).
Thank you in advance for your help and advice!
Best regards
Matthias
Depending on the design temperature (whether you expect very cold or average winters), I would recommend using only an air-to-water heat pump for a 140m² (1,507 sq ft) KFW-70 house with such a low heat demand—finished.
I roughly estimate about 5,500 kWh/year need according to DIN standards for heating and hot water—in practice, with warmer indoor temperatures, maybe around 7,000 kWh (estimates only). With a well-sized and properly installed air-to-water heat pump having a seasonal performance factor of 3.5, your actual (estimated) consumption would be around 2,000 kWh/year, plus circulation pump and control system.
Solar? For what? To heat the hot water in summer? Running the heat pump for just one hour per day for that is certainly much cheaper than investing in a solar system. It probably will never pay off. And in winter, it doesn’t produce any significant output. Also, combining it with solar would require a buffer tank—which is not necessary for a monovalent air-to-water heat pump system. In fact, with underfloor heating, a buffer tank would even reduce efficiency.
Ice storage? Given your low heating load? In my opinion, that’s economically unreasonable. But the experts here can probably provide more insight.
But absolutely necessary before choosing the heating system: a heating load calculation.
I roughly estimate about 5,500 kWh/year need according to DIN standards for heating and hot water—in practice, with warmer indoor temperatures, maybe around 7,000 kWh (estimates only). With a well-sized and properly installed air-to-water heat pump having a seasonal performance factor of 3.5, your actual (estimated) consumption would be around 2,000 kWh/year, plus circulation pump and control system.
Solar? For what? To heat the hot water in summer? Running the heat pump for just one hour per day for that is certainly much cheaper than investing in a solar system. It probably will never pay off. And in winter, it doesn’t produce any significant output. Also, combining it with solar would require a buffer tank—which is not necessary for a monovalent air-to-water heat pump system. In fact, with underfloor heating, a buffer tank would even reduce efficiency.
Ice storage? Given your low heating load? In my opinion, that’s economically unreasonable. But the experts here can probably provide more insight.
But absolutely necessary before choosing the heating system: a heating load calculation.
Thanks for the answers.
How does it work with hot water? Since heat pumps are best suited for small temperature differences, if hot water needs to be heated to 60°C (140°F) in winter, wouldn’t that require quite a lot of electricity?
What about combining an air-to-water heat pump with photovoltaics? I guess that probably isn’t cost-effective either, right?
How does it work with hot water? Since heat pumps are best suited for small temperature differences, if hot water needs to be heated to 60°C (140°F) in winter, wouldn’t that require quite a lot of electricity?
What about combining an air-to-water heat pump with photovoltaics? I guess that probably isn’t cost-effective either, right?
What about a brine heat pump with geothermal baskets? Depending on the design, these also require somewhat less space on the property.
I would be very cautious with deep drilling. You have to test whether the well can provide enough water and, most importantly, whether the soakaway well can absorb it again. (Possibly testing and pumping over several days/weeks) I know a case where the soakaway well became clogged with sediment...
We are still considering which heating system to choose. We have already ruled out deep drilling because, with rock and other factors here, it was too risky and the costs became unpredictable.
Geothermal with baskets is our favorite, but the initial investment is quite high. So, an air source heat pump is still an option, but I’m hesitant because, in new housing areas, I often hear those motors running in the gardens... :-/
Pellets are also not off the table yet, since the initial cost is somewhat lower and we have space in the basement. However, we’re uncomfortable with burning something again and the resulting environmental impact.
Difficult, difficult….
I would be very cautious with deep drilling. You have to test whether the well can provide enough water and, most importantly, whether the soakaway well can absorb it again. (Possibly testing and pumping over several days/weeks) I know a case where the soakaway well became clogged with sediment...
We are still considering which heating system to choose. We have already ruled out deep drilling because, with rock and other factors here, it was too risky and the costs became unpredictable.
Geothermal with baskets is our favorite, but the initial investment is quite high. So, an air source heat pump is still an option, but I’m hesitant because, in new housing areas, I often hear those motors running in the gardens... :-/
Pellets are also not off the table yet, since the initial cost is somewhat lower and we have space in the basement. However, we’re uncomfortable with burning something again and the resulting environmental impact.
Difficult, difficult….
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