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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Sebastian797 Jun 2016 07:32Inotsara schrieb:
In 30 years, our KfW 40 Plus will definitely sell better than a KfW 70.Nobody will care about that in 30 years... especially since it doesn't really mean anything. KfW or energy saving regulations are mostly just a lot of window dressing...
Sebastian79 schrieb:
No one will care about that in 30 years... especially since it doesn’t really say anything. KfW or energy saving regulations are also just a lot of window dressing... Matter of opinion. When buying, I am very interested today in how many additional costs I will face. Since there were no used homes from the 1940s available, we are now having one built.
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Bauexperte7 Jun 2016 10:01Inotsara schrieb:
It's a matter of perspective. Today, when buying, I definitely care about how many additional costs I will face. Since there were no used 40-square-meter (430-square-foot) homes available, we are now having one built.No, there is no two ways about it; humans are creatures of habit!You yourself write that additional costs matter to you; beyond the condition of the property, potential buyers will naturally not be interested in much else in the future.
I am also sure—assuming you maintain and take care of your property—that after some years you will not be able to recoup even a fraction of your investment through resale. Of course, if you look at the property over time, the situation looks different.
Best regards, Bauexperte
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Sebastian797 Jun 2016 10:01Of course, that's a matter of opinion (regarding the sales bonus, not the meaningfulness of the "certification") – but seriously think about this: in 30 (!!!) years, you'll proudly write "KFW40" in your house listing – and do you really believe anyone will check what that was all about back then? By then, the zero-energy standard will have existed for 20 years...
No, that won't give you any advantage when selling... especially since the house will have lost some value by then (the house, not the land – possibly).
No, that won't give you any advantage when selling... especially since the house will have lost some value by then (the house, not the land – possibly).
Sebastian79 schrieb:
Of course, this is subjective (regarding the sales bonus, not the meaningfulness of the "certification") – but seriously think about it: In 30 (!!!) years, you’ll proudly list “KFW40” in your house advertisement – and do you really believe anyone will check what that was all about 30 years ago? By then, the net-zero energy standard will have been around for 20 years already...
No, this won’t give you any advantage when selling... especially since the house itself will have lost some value by then (the house, not necessarily the land). Why does everyone want to sell their house at a profit? In 30 years, I will sell my house because my wife and I will be old. We won’t be able or willing to climb stairs anymore, so we’ll opt for other alternatives. A condominium, a bungalow, who knows...
And achieving KFW 40 is best done with a prefab house manufacturer who specializes in and is familiar with this standard. For them, it’s an easy win, and their prices differ from those of an individual architect building with masonry. Also, their walls are almost half a meter thick, and other things are simply better solved with timber construction. In some cases, building materials developed together with major manufacturers—such as Knauf—are used.
Don’t just make claims or run theoretical calculations. Simply take an interest and visit a prefab home provider to get a calculation, then compare that with your utility costs, especially the steadily rising electricity costs. Then say again that it wouldn’t be worth it... The stress you avoid from construction alone is an enormous added value.
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Sebastian797 Jun 2016 11:02Yeah, sure...
By the way, I’m the last person here who built their house with profit in mind...
And your great additional costs: What are you really saving compared to the effort? 5 euros per month? 10 euros? When do the costs balance out against the effort?
And of course, they offer a different price – but do you really think it’s a better one? Totally fell for that...
Personally, I’d rather deal with stress than live in a timber frame construction – but that’s just my own opinion. That also makes the supposed advantage regarding resale value later irrelevant...
By the way, I’m the last person here who built their house with profit in mind...
And your great additional costs: What are you really saving compared to the effort? 5 euros per month? 10 euros? When do the costs balance out against the effort?
And of course, they offer a different price – but do you really think it’s a better one? Totally fell for that...
Personally, I’d rather deal with stress than live in a timber frame construction – but that’s just my own opinion. That also makes the supposed advantage regarding resale value later irrelevant...
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