ᐅ Solar Power System: Yes or No?

Skunk schrieb:

Facing the midday sun, i.e., south direction. Depending on the longitude, a different tilt is necessary. I read somewhere about approximately 30° tilt, but that depends on the location. Minor deviations shouldn’t be a big issue. With southeast or southwest orientation, about 90% efficiency should still be achievable.

Hello

Unfortunately, in this discussion both photovoltaic (PV) systems and solar thermal systems are being mixed up.
Please keep these clearly separate!

Photovoltaics:
- Optimal orientation is as close to due south as possible, with a slight deviation towards the east (5°-10°) preferred. The panels perform best when they are cool — meaning it’s better to catch a bit more morning sun than afternoon sun, since the panels heat up during the day.
- Optimal tilt in Germany: The sun is about 62° above the horizon at midday in summer and around 16° above the horizon in winter. A flatter mounting angle captures more summer sun, while a steeper tilt favors winter sun. 30° is a common compromise between summer and winter. However, other tilt angles don’t make a huge difference in annual yield.
- Financially: This needs to be calculated on a case-by-case basis. Two years ago, a private builder could realistically achieve around 12-13% return over 20 years (the duration of government-guaranteed feed-in tariffs). Currently, a realistic return is about 3-4%, assuming the system is well planned. With daytime self-consumption (e.g., a parent with children at home all day, a home office...), higher returns are possible.

Whether photovoltaics are worthwhile must—surprise surprise—be calculated by a professional in each situation.

Solar thermal systems:
- Orientation and tilt probably follow similar principles as photovoltaics — although optimal orientation might be more towards the west, since the goal is to use heat later on.

- Regarding economics: How long does the temperature stay in the hot water tanks? Given how well insulated modern tanks are, I would estimate about 12-14 hours. So in summer, solar thermal water can still serve the whole family’s showers/baths in the evening. And by the next morning, there should still be warm water available. In winter (assuming good weather), the hot water tank should still be warm enough to cover evening demand. Additionally, I connect my dishwasher and washing machine to the hot water system. It seems wasteful if heating for these appliances continues electrically or with geothermal energy while the tank cools unused nearby.

Personally, all the people I know with solar thermal systems have only had positive experiences. No one has been dissatisfied so far.

I will definitely get one myself — then in 2-3 years I can report back here with a summary.

That’s my two cents
Micha

Micha&Dany schrieb:
...Personally, from acquaintances who have solar thermal systems, I have only heard positive feedback. No one seems dissatisfied...

That is quite satisfactory. Perhaps instead of general satisfaction, there are also specific data? How many kWh were actually generated with which system and which installed heat meter?

Best regards

Hello €uro

I haven’t asked in detail yet...
I’ll have to do that, and then I can answer your question.

Regards
Micha

Micha&Dany schrieb:
Hello

Unfortunately, there is constant confusion here between photovoltaic (photovoltaics) and solar thermal systems (solar thermal).
Both need to be please distinguished clearly!

Solar thermal system:

- Regarding cost-effectiveness: How long does the temperature stay in the hot water storage tanks? Given how well insulated they are nowadays, I would estimate about 12-14 hours.

In winter (assuming good weather), the hot water tank should still be warm enough in the evening to cover my demand.
Also, I connect my dishwasher and washing machine to the hot water. It wouldn’t make sense if I keep heating the water electrically for these appliances and let the stored heat go unused by cooling down next to the tank...

Just my two cents
Micha

Hello!

I have had my solar system for only a few weeks. The temperature in the 300-liter (79-gallon) tank naturally drops steadily without sunlight and isn’t maintained. I don’t see this as a problem in winter since it basically functions as heating support.

From my initial impression, the energy lasts for several days because the water is heated well above shower temperature. I’m still not very happy with the system control, though. When the tank’s 300 liters (79 gallons) of water are heated to 45°C (113°F), theoretically four people could shower with it. But apparently, when water is drawn off, cold water is immediately added again. This means the first person showers hot, the second warm, the third lukewarm, and the fourth preferably not at all. I hope this can be adjusted somehow!?

Connecting electrical appliances is an interesting idea, but I’m not sure if the electronics of washing machines and dryers can handle it. Also, if the solar-heated water is very hot, you would need to mix it down with a mixing valve before feeding it to the machines for items like shirts!?

By the way, my neighbor has a 210-liter (55-gallon) tank that takes up the relatively unused space under his boiler. Compared to that, the 300-liter (79-gallon) tank (maybe due to better insulation) seems huge and limits the use of the utility room.

Best regards,
TomTom1

TomTom1 schrieb:
...At least in winter, I don’t see a problem; it basically works as heating support.

How would that be possible???

TomTom1 schrieb:
...But apparently, the extracted water is immediately replenished with (cold) water.

Well, there seem to be significant shortcomings here! What temperature level should the refilled domestic water have?

TomTom1 schrieb:
...At first impression, the energy lasts for several days, since the water is heated well above shower temperature.

“Temperature” is something completely different from energy!!! Surely, no heat meter was installed here, otherwise the conclusions would be completely different!

TomTom1 schrieb:
...I am still not satisfied with the system’s control... I hope there is a way to adjust it differently!?

Well, then good luck!

Best regards.

€uro schrieb:
How could that be possible???
Well, there seem to be significant deficiencies here! What temperature level should the reheated buffer tank have?
"Temperature" is something completely different from energy!!! Surely no heat meter was installed here; otherwise, the conclusions would be completely different!
Well then, good luck!

Best regards.

Hi!

Euro got me – energy consultant versus home builder!
Question 1: Law of conservation of energy.
Question 2: Wrong approach. First use the heated water, then reheat it.
Statement about temperature and energy: I’ve never thought about that – but it sounds like nonsense.
Heat meter: If there is one, it must have been installed without my knowledge – do you mean the TV transmitter or the washing machine control center?

Best regards,
TomTom1.