Hello,
I’m curious if anyone here is really knowledgeable about photovoltaic systems or if anyone knows of a website where you can calculate the performance and orientation.
We have a townhouse measuring 12 x 9 meters (39 x 30 feet) with 60 cm (24 inches) roof overhangs and a 25° pitch. The house offer stated that we would get a 9.9 kW photovoltaic system. However, we were already told that the roof area is not sufficient and that some panels would have to be placed on the extension. We actually don’t want that; we want everything on the hipped roof. According to the technical company, only 9.5 kW would fit there with an east/west orientation.
Since our house’s main roof surfaces are oriented roughly northeast/southwest, I’m a bit concerned whether it makes sense to install half the system on the northeast side. According to a table I found, that would be an azimuth of -110° and only yield about 79% efficiency. Now I’m wondering which would make more sense: the technical company’s suggested layout or utilizing the smaller roof surface nearby, which faces southeast. Of course, fewer panels would fit there, so the system would probably be closer to 7 kW, but could it generate more energy this way? We would also save money because fewer panels are needed. The technical company probably just wants to install whatever they quoted, whether it makes sense or not, as long as they make the sale.
Therefore, I would like to calculate what can be achieved with fewer solar panels but better orientation, compared to more panels with a less optimal orientation.
I’m curious if anyone here is really knowledgeable about photovoltaic systems or if anyone knows of a website where you can calculate the performance and orientation.
We have a townhouse measuring 12 x 9 meters (39 x 30 feet) with 60 cm (24 inches) roof overhangs and a 25° pitch. The house offer stated that we would get a 9.9 kW photovoltaic system. However, we were already told that the roof area is not sufficient and that some panels would have to be placed on the extension. We actually don’t want that; we want everything on the hipped roof. According to the technical company, only 9.5 kW would fit there with an east/west orientation.
Since our house’s main roof surfaces are oriented roughly northeast/southwest, I’m a bit concerned whether it makes sense to install half the system on the northeast side. According to a table I found, that would be an azimuth of -110° and only yield about 79% efficiency. Now I’m wondering which would make more sense: the technical company’s suggested layout or utilizing the smaller roof surface nearby, which faces southeast. Of course, fewer panels would fit there, so the system would probably be closer to 7 kW, but could it generate more energy this way? We would also save money because fewer panels are needed. The technical company probably just wants to install whatever they quoted, whether it makes sense or not, as long as they make the sale.
Therefore, I would like to calculate what can be achieved with fewer solar panels but better orientation, compared to more panels with a less optimal orientation.
S
Stadtvilla1917 Mar 2020 12:44Looks good, no idea why they only want to do 2 sides for us, probably because it’s less work and saves costs to climb on just 2 roof surfaces.
They are really disorganized anyway... We should inform them when our roofer arrives, then they wanted to send a colleague to install the mounts. So, we gave notice 3 weeks before the roofing work started, which was in November. We sent the roofer’s contact details by email, but nobody ever contacted the roofer. A few days later we called to ask what the problem was. They said it was way too short notice and it’s impossible to assign a colleague that quickly.
We thought, well, that’s your problem then, so you’ll just have more work. The scaffolding was taken down on January 31st, and now on March 10th they suddenly realize that the roof is already covered and there’s no scaffolding left. And now they want to make that our problem...
We signed the contract with them in December 2018. They were supposed to start in October 2019, but because of a 5-week delay on our part, there were suddenly no capacities available in 2019 and we had to wait until now...
They are really disorganized anyway... We should inform them when our roofer arrives, then they wanted to send a colleague to install the mounts. So, we gave notice 3 weeks before the roofing work started, which was in November. We sent the roofer’s contact details by email, but nobody ever contacted the roofer. A few days later we called to ask what the problem was. They said it was way too short notice and it’s impossible to assign a colleague that quickly.
We thought, well, that’s your problem then, so you’ll just have more work. The scaffolding was taken down on January 31st, and now on March 10th they suddenly realize that the roof is already covered and there’s no scaffolding left. And now they want to make that our problem...
We signed the contract with them in December 2018. They were supposed to start in October 2019, but because of a 5-week delay on our part, there were suddenly no capacities available in 2019 and we had to wait until now...
S
Stadtvilla1921 Mar 2020 07:49So, we have now clearly been informed that three sides are not possible because the inverter only has two inputs.
S
Stadtvilla1921 Mar 2020 10:21No, I didn’t explicitly ask for that. I only asked whether it might make more sense to use the smaller area instead of the larger one. Then they said they wanted to check the possibility of using the smaller area as well. Two days later, they said it’s not possible to use three roof surfaces because the inverter only has two inputs.
We were also advised against the LG battery and recommended Viessmann devices instead. These are more expensive and larger but can be upgraded later. Right now, for the same price, we would only get 7.8 kW instead of 10 kW, or we could pay more for 11.xx kW.
The Viessmann system apparently has the inverter integrated, so maybe that’s the reason?
We were also advised against the LG battery and recommended Viessmann devices instead. These are more expensive and larger but can be upgraded later. Right now, for the same price, we would only get 7.8 kW instead of 10 kW, or we could pay more for 11.xx kW.
The Viessmann system apparently has the inverter integrated, so maybe that’s the reason?
P
Piotr19816 Aug 2020 07:44I’m joining in here....
Roof structure and orientation are exactly the same as the original poster’s. After initial talks with the solar installer, we can get a maximum of 5.84 kWp on the roof (with 18! modules – 6 modules on one side of the roof).
Honestly, I was a bit surprised that so few modules fit per side.
Planned equipment: Sharp NU-JC 320 + BYD Box LV battery storage.
What are your thoughts? Is 6 modules on one roof surface correct?
The solar installer assumes an average of 850 sunlight hours per year.
Roof structure and orientation are exactly the same as the original poster’s. After initial talks with the solar installer, we can get a maximum of 5.84 kWp on the roof (with 18! modules – 6 modules on one side of the roof).
Honestly, I was a bit surprised that so few modules fit per side.
Planned equipment: Sharp NU-JC 320 + BYD Box LV battery storage.
What are your thoughts? Is 6 modules on one roof surface correct?
The solar installer assumes an average of 850 sunlight hours per year.
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