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 =)
Hi, here is my attempt at an answer below. Best regards, Thorsten
275 = KFW40+ subsidy?
Correct system sizing is essential here. It depends on location and orientation, roof pitch, type of collectors used, inverter efficiency, battery, and much more. An expert should calculate this.
In my case, (very soon, installation starts tomorrow) it is regulated at 70%.
My system has charging management, but I only have a very small battery in a “smart solution” from SMA. This setup aims for a self-consumption rate of about 50% and uses the battery intensively with high efficiency—under good sunlight, partly more than one charge cycle per day.
There are many different types of warranties, which vary in nature and scope from manufacturer to manufacturer.
jochi79 schrieb:I think so, but it’s best to double-check just to be sure.
- Combination of KFW 153 + 275 possible?
275 = KFW40+ subsidy?
jochi79 schrieb:Either the system is regulated via the inverter or the grid operator limits the feed-in. I would have the inverter regulate it. Excess electricity then goes into the battery (ideally with an intelligent charging management system) or is self-consumed as much as possible.
- Grid feed-in max. 50% realistically achievable? What happens, for example, in summer when the grid feed-in increases?
Correct system sizing is essential here. It depends on location and orientation, roof pitch, type of collectors used, inverter efficiency, battery, and much more. An expert should calculate this.
In my case, (very soon, installation starts tomorrow) it is regulated at 70%.
My system has charging management, but I only have a very small battery in a “smart solution” from SMA. This setup aims for a self-consumption rate of about 50% and uses the battery intensively with high efficiency—under good sunlight, partly more than one charge cycle per day.
jochi79 schrieb:Yes. Quality providers already have that covered. It’s not complicated.
- Are common inverters and batteries already designed for the new requirements?
jochi79 schrieb:I’m not sure exactly what is meant here.
- Time-value replacement guarantee of 10 years, is this already considered by the manufacturers?
There are many different types of warranties, which vary in nature and scope from manufacturer to manufacturer.
T21150 schrieb:
I don’t understand exactly what is meant here.
There are many types of warranties that vary in nature and scope depending on the manufacturer. According to the guidelines effective from 01.03., specific requirements are now being enforced, and quite a few things have changed since then. My question is basically whether anyone has looked deeply enough into this topic to confidently say that there are currently batteries available that meet the new standards for KFW 275, or if it will take some time for manufacturers to adapt accordingly.
Furthermore, I would also like to address the issue of cost-effectiveness, especially for homeowners building under the new KFW guidelines from 01.04.2016 onward. Assuming my offered house meets KFW 55 standards and I need a heating system anyway, these costs are simply part of the process. With the €10,000 (ten thousand euros) subsidy for KFW, I can finance the additional insulation. Now, to the main point:
For KFW 40+ I receive an additional €10,000. For this, I plan to install a 6 kW system on the roof and a corresponding storage battery in the basement, with total costs of €20,000. Please do not take these numbers literally; they are just rough figures to illustrate the finances.
So far, this would cost me €10,000 out of pocket. Based on an annual consumption of 5,000 kWh and an annual output of the system of 5,000 kWh, the following example emerges:
Electricity costs without photovoltaic: 5,000 kWh/year * €0.25/kWh = €1,250/year
With photovoltaic:
Self-consumption 2,500 kWh, savings 2,500 kWh/year * €0.25/kWh = €625/year
Feed-in 2,500 kWh, earnings 2,500 kWh/year * €0.12/kWh = €300/year
According to this calculation, I would have €925 more available per year. How long it takes for the battery to pay for itself can be calculated individually. In this case, a battery, if functioning correctly and without damage, seems absolutely cost-effective—unless I am completely mistaken?
D
daniels8724 Mar 2016 14:19jochi79 schrieb:
Hello everyone,
I would like to revisit the topic of KfW 40+ here, slightly deviating from the original headline.
I am currently planning a new build, and the current offer describes a KfW55 house (140m² (1507 sq ft) plus 40m² (430 sq ft) guest apartment in the basement plus 20m² (215 sq ft) living basement = ~200m² (2153 sq ft) living space, air-to-water heat pump).
Since the house is offered as a KfW55, I would currently receive a subsidy of €12,000 from the L-Bank. For a KfW40 house, that would be another €10,000 more, which according to my provider would cover the extra insulation. For KfW 40+ there would be another €10,000 subsidy; with that money, I could at least finance a photovoltaic system (~5-6 kW) and possibly part of the battery.
However, since March 1st, 2016, new guidelines for KfW program 275 have been in place. I haven’t found many discussions on this yet, so here are my questions:
- Is combining KfW 153 and 275 possible?
- Is a grid feed-in limit of max. 50% realistically achievable? What happens, for example, in summer when grid feed-in is higher?
- Are common inverters and batteries already designed for the new requirements?
- Is the 10-year residual value warranty already accounted for by manufacturers?153+275 is not possible, according to Flose89.
For excess production, it’s best to plan a consumer load for the summer, such as an air conditioner. If that’s not enough, maybe put an electric heater on the terrace?
To come back to the topic of energy self-sufficiency: clearly, it’s not economically viable, but definitely feasible.
A ground source heat pump (brine-to-water) doesn’t have as pronounced peak loads in winter as an air-to-water heat pump, and would probably be better suited.
A compact house with good insulation, combined with photovoltaics and storage. In winter, heat with wood from your own forest if the electricity runs out.
It’s best to keep indoor temperatures to a maximum of 18–19°C (64–66°F), shower with lukewarm water or cold water.
Regarding KfW 40+: currently very profitable in Bavaria!
daniels87 schrieb:
Regarding KfW 40+: Currently very cost-effective in Bavaria!I fully agree, especially for our building project.
The additional subsidies effectively upgrade our KfW55 house to a KfW40+ house at no extra cost.
Best regards
D
daniels8724 Mar 2016 21:4210,000 Houses Program.
4,500 € efficiency bonus and 8,000 € for photovoltaic system with storage.
4,500 € efficiency bonus and 8,000 € for photovoltaic system with storage.
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