ᐅ Operating a heat pump independently with a photovoltaic system.
Created on: 18 Dec 2015 19:51
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Inotsara
Is there a photovoltaic expert here? Preferably an engineer specializing in this field? I am an electrician myself but have not yet had any practical experience with photovoltaic systems. So far, I only know about them theoretically and am very enthusiastic. I want to dive deeper into this topic and prepare myself for practical work. Recently, I have been looking into inverters and especially battery storage. The more I read, the bigger the gap I feel needs to be filled.
Currently, I am working on a project involving my parents' air-to-water heat pump. It’s a newly built house with two living units. The combined electricity consumption of both units is about 2200 kWh. Additionally, the pump consumes approximately 6600 kWh per year. Naively, I assumed my parents could invest around 25,000€ in a 9 kWp photovoltaic system and achieve a self-sufficient setup with very low electricity costs (about 30€ per month instead of 180€).
But that’s not the case. Firstly, a single-phase storage system is not an option because, due to the technology and grid regulations, the pump relies on the other two phases and will ALWAYS draw power from the grid. Even with a three-phase battery storage system, this problem would only be theoretically circumvented but not completely solved. Especially in winter, the pump runs at 80%-100% capacity while a photovoltaic system generates only about 30%-35% of its output in winter. In summer, the situation is almost exactly the opposite. This means we would underproduce in winter and overproduce in summer. On top of that, a three-phase battery system costs twice as much, and the number of manufacturers offering this option is very limited.
So, my question to the real experts: Should I just discard the idea of making the heat pump fully independent, or have I missed something?
I have gained a lot of knowledge in recent days through phone conversations with an engineer who is also a salesperson. However, I feel a bit uncomfortable bothering him further. He has already explained a lot to me. Also, information in written form is always better because you can look things up repeatedly and add to your knowledge. Therefore, it would be great if we could share our knowledge here together =)
Currently, I am working on a project involving my parents' air-to-water heat pump. It’s a newly built house with two living units. The combined electricity consumption of both units is about 2200 kWh. Additionally, the pump consumes approximately 6600 kWh per year. Naively, I assumed my parents could invest around 25,000€ in a 9 kWp photovoltaic system and achieve a self-sufficient setup with very low electricity costs (about 30€ per month instead of 180€).
But that’s not the case. Firstly, a single-phase storage system is not an option because, due to the technology and grid regulations, the pump relies on the other two phases and will ALWAYS draw power from the grid. Even with a three-phase battery storage system, this problem would only be theoretically circumvented but not completely solved. Especially in winter, the pump runs at 80%-100% capacity while a photovoltaic system generates only about 30%-35% of its output in winter. In summer, the situation is almost exactly the opposite. This means we would underproduce in winter and overproduce in summer. On top of that, a three-phase battery system costs twice as much, and the number of manufacturers offering this option is very limited.
So, my question to the real experts: Should I just discard the idea of making the heat pump fully independent, or have I missed something?
I have gained a lot of knowledge in recent days through phone conversations with an engineer who is also a salesperson. However, I feel a bit uncomfortable bothering him further. He has already explained a lot to me. Also, information in written form is always better because you can look things up repeatedly and add to your knowledge. Therefore, it would be great if we could share our knowledge here together =)
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daniels8725 Mar 2016 11:26Yes, 15,000 € KfW funding from Program 153 and up to 18,000 € from the 10,000 Houses Program. Additionally, BAFA subsidies are also possible.
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Alpandian8928 Mar 2016 21:52I am from Bavaria and planning to build a house but have not yet obtained any quotes. Is it worth going for KfW 40+ in terms of additional costs and possible subsidies compared to KfW 55?
Alpandian89 schrieb:
I’m from Bavaria and want to build a house but haven’t requested any quotes yet. Is it worth aiming for KfW 40+ in terms of additional costs and possible subsidies compared to KfW 55?No, most likely not, even with all subsidies taken into account.
Depending on the size of the house, you save roughly 10 to 30 euros per month moving from KfW 55 to 40+ — NOT including necessary capital costs. This is a rough estimate. Even KfW 70 (now part of the Energy Saving Ordinance 100) requires very little energy; KfW 55 uses somewhat less, but not noticeably so. KfW 40 and 40+ are already at an extreme low level, with a hefty price premium. KfW 40+ requires complex solar systems with large battery storage. That is still very expensive these days.
However, technically speaking, KfW 40+ is impressive.
Do you have the money? Are you willing to invest capital for the sake of the technology, enjoyment, and environment in your house? Without directly profiting financially in a noticeable way?
Then go for it. If I could have afforded it, I would have done the same.
For the fun of it — and because, as a physicist, having a “machine room” like on an aircraft carrier in a house feels unusual but not intimidating.
Regards
Thorsten
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Alpandian8928 Mar 2016 22:05Thanks Thorsten for your assessment. KfW 55 compared to KfW 70 might be more worthwhile?
When I built back in 2014, a KFW55 standard would have cost me about 12,000 to 16,000 euros more.
If you subtract around 8,000 euros for underfloor heating, which I didn’t want and still don’t want,
my issue, or rather my wife’s and my preferences, lie in the heating system.
For about 8,000 euros extra, neither I nor the bank found it worthwhile to finance the additional expenses, which mainly would have come from the foundation slab and substructure (my KFW70 is almost like a KFW55, very close).
The Energy Saving Ordinance 100 (equivalent to KFW70) results in about 10 to 15 euros more per month in direct heating costs compared to the KFW55 standard.
Even with a KFW70/Energy Saving Ordinance 100 building, for roughly 130 square meters (about 1,400 square feet) including heating and hot water—regardless of whether gas or an air-to-water heat pump is used—the monthly cost is around 50 euros. The savings potential beyond that gets increasingly marginal.
However, if I had known back then that KFW70 would become obsolete and the norm by 2016, I most likely would have chosen to build to the KFW55 standard, mainly because of market and resale value considerations.
Today, I would therefore build to KFW55, as it currently seems the most sensible option. KFW40 and KFW40 Plus are excellent, but extremely expensive.
You can easily end up spending 10,000 to 30,000 euros more than with KFW55.
Best regards,
Thorsten
If you subtract around 8,000 euros for underfloor heating, which I didn’t want and still don’t want,
my issue, or rather my wife’s and my preferences, lie in the heating system.
For about 8,000 euros extra, neither I nor the bank found it worthwhile to finance the additional expenses, which mainly would have come from the foundation slab and substructure (my KFW70 is almost like a KFW55, very close).
The Energy Saving Ordinance 100 (equivalent to KFW70) results in about 10 to 15 euros more per month in direct heating costs compared to the KFW55 standard.
Even with a KFW70/Energy Saving Ordinance 100 building, for roughly 130 square meters (about 1,400 square feet) including heating and hot water—regardless of whether gas or an air-to-water heat pump is used—the monthly cost is around 50 euros. The savings potential beyond that gets increasingly marginal.
However, if I had known back then that KFW70 would become obsolete and the norm by 2016, I most likely would have chosen to build to the KFW55 standard, mainly because of market and resale value considerations.
Today, I would therefore build to KFW55, as it currently seems the most sensible option. KFW40 and KFW40 Plus are excellent, but extremely expensive.
You can easily end up spending 10,000 to 30,000 euros more than with KFW55.
Best regards,
Thorsten
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