ᐅ Operating a heat pump independently with a photovoltaic system.
Created on: 18 Dec 2015 19:51
I
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 =)
Inotsara schrieb:
If you could explain your calculation to me in more detail, I would be happy to show you mine. Then we can compare.Why do we even need a calculation for that? It should be obvious that a property of several hundred square meters with a house larger than 100 square meters (more than 100 square meters) and its construction costs is not “economically” livable for a family of four.
This is pure luxury! It has absolutely NOTHING to do with cost-effectiveness, which is clearly your top priority...
Nevertheless, I would still be interested to see how you justify your KfW40+ house economically.
@oleda222.
You’re right. But don’t be too harsh on the OP.
The decision to build a single-family home is usually not based on a strictly positive business case. Even experts say so.
The decision is often made based on other factors.
In a way, it’s a luxury—or rather, the desire to shape one’s private living situation according to personal preferences (and if you can do that, it’s a kind of luxury as well).
What the OP probably means is: Considering the decision, be as economical as possible... (again, from their own set of criteria. Anyone can justify their numbers—see my comment above—but it’s legitimate to do so, no shame in that! Some people are happy with low initial costs, others with savings made later through an investment).
Best regards, Thorsten
You’re right. But don’t be too harsh on the OP.
The decision to build a single-family home is usually not based on a strictly positive business case. Even experts say so.
The decision is often made based on other factors.
In a way, it’s a luxury—or rather, the desire to shape one’s private living situation according to personal preferences (and if you can do that, it’s a kind of luxury as well).
What the OP probably means is: Considering the decision, be as economical as possible... (again, from their own set of criteria. Anyone can justify their numbers—see my comment above—but it’s legitimate to do so, no shame in that! Some people are happy with low initial costs, others with savings made later through an investment).
Best regards, Thorsten
T21150 schrieb:
The decision is usually based on other criteria.This statement is quite clear:
Inotsara schrieb:
Thank you for your tip. The potential expansion of the system is, of course, logical and the resulting outcome understandable. However, for me, cost-effectiveness is the top priority.
@T21150
There is nothing to add to your recent posts in this thread. Very good contributions.
@oleda222
Sometimes you do make things difficult.
The OP primarily meant in terms of cost-effectiveness that (referring to my example) it is completely uneconomical to install a hugely oversized photovoltaic system on the roof just to cover as much of the self-consumption as possible — which I fully agree with.
You say that often the investment in land and house is not economical purely from a business perspective, although this is not always necessarily the case. A few months ago in a thread, I described using a colleague’s example that there are regions where the investment already pays off based on the land price alone (my colleague paid about 120 euros per square meter (about 11 USD per square foot) three years ago — today people in his municipality pay around 300 euros per square meter (about 28 USD per square foot) for a similar location).
You are also right that investments in an energy-efficient house like KfW55 or KfW40 standards often do not pay off in the medium term. There was a recent thread on this as well.
However — as far as the OP has thought in this direction at all: this was not the starting point of their question. Their interest/question is to what extent a high degree of self-sufficiency can be achieved, or whether this is generally uneconomical, and what experiences others have had in this regard.
There is nothing to add to your recent posts in this thread. Very good contributions.
@oleda222
Sometimes you do make things difficult.
The OP primarily meant in terms of cost-effectiveness that (referring to my example) it is completely uneconomical to install a hugely oversized photovoltaic system on the roof just to cover as much of the self-consumption as possible — which I fully agree with.
You say that often the investment in land and house is not economical purely from a business perspective, although this is not always necessarily the case. A few months ago in a thread, I described using a colleague’s example that there are regions where the investment already pays off based on the land price alone (my colleague paid about 120 euros per square meter (about 11 USD per square foot) three years ago — today people in his municipality pay around 300 euros per square meter (about 28 USD per square foot) for a similar location).
You are also right that investments in an energy-efficient house like KfW55 or KfW40 standards often do not pay off in the medium term. There was a recent thread on this as well.
However — as far as the OP has thought in this direction at all: this was not the starting point of their question. Their interest/question is to what extent a high degree of self-sufficiency can be achieved, or whether this is generally uneconomical, and what experiences others have had in this regard.
oleda222 schrieb:
Why would you need an invoice for that? It should be obvious that a plot of land several hundred square meters in size with a house over 100 square meters in size, along with its construction costs, is not "economical" for a family of four to live in.
This is pure luxury! It has absolutely NOTHING to do with economy, which is your top priority...
Still, I’d be interested to see how you calculate your KfW40+ house. I don’t understand why anyone would insist on the opinion that a house is not economical. Maybe we have different ideas about the definition of "economy"? Or maybe it’s just me. Personally, I don’t want my house to replace my job so that it earns money for me and I never have to work again. If I finance a house with land and have paid it off after 30 years, then it was economical for me. The interest I gave away until then matters to me about as much as a sack of rice falling over in China. Because if I stay in my apartment and throw the same money out the window for 30 years, after 30 years I still don’t have any land or property. So, compared to that, I’m doing quite well. That is what economy means to me. However, I wasn’t talking about that at all—I was only referring to my parents’ photovoltaic system, with an example from f-pNo. But I guess that’s been explained now.
Let’s get to the KfW 40 Plus house (my project), where I have monthly heating costs of €0.00 (because of the air-to-water heat pump and ventilation—so only electricity) and, depending on the season, an average monthly electricity cost of about €20.00 including the heat pump and ventilation, thanks to the 5.3 kWp photovoltaic system. In thirty years, my electricity price will probably rise somewhat—provided I don’t add anything else. But compared to others who are still 100% dependent on electricity and will probably pay ten times today’s prices, I’m better off. Or has electricity suddenly become cheaper?
But thanks for worrying about my uneconomical setup. On top of all that, there’s obviously the luxury factor already mentioned: my own garden, my own barbecue area, my own terrace, the freedom to do what I want, like-minded homeowners of more or less the same age, where the children can integrate perfectly as well. And so on...
It’s a shame this thread missed its point.
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