ᐅ Energy Self-Sufficiency – Services Offered

Google "Sonnenhaus" for the heating system – household electricity could then be covered with photovoltaic panels and a battery (though it might not be enough to cover everything). However, economically, this is not necessarily viable...

franz_obaz schrieb:
PS: I’m always available for tips & tricks regarding energy self-sufficiency!

Hi Franz,

I’ve upgraded too. An east/west photovoltaic system with a nominal 6.625 kWp. 11 panels at 265 W east, 14 west. With a small buffer battery of 2 kWh (2.2 kWh). The integrated inverter/battery system is from SMA. In April (the system was installed on 07.04., and the S0 meter since 17.04.), I achieved 78% self-sufficiency, and so far in May, 84%.

There are solar irradiation calculators online. With those, I can get a good idea of the outlook: as calculated, an average of around 50% yearly self-sufficiency.

If you increase battery capacity, you also increase (charging/discharging) losses somewhat. Battery size always needs to be adapted to household habits and consumption. A small battery always makes sense, as it immediately increases the self-sufficiency rate significantly. A too-large battery, however, is less sensible.

Covering the house overnight: only low power is needed, and efficiency is also lower. Efficiency rises with higher power demand. I can see this with my system, which nominally achieves 97%, but at 150-400 watts during the night, it operates at about 85-90%.

From April to October, there is usually enough energy from above if the photovoltaic system is well and properly sized. After that: slim pickings. Based on my research, even with a large battery, you can reach about 60-80% max. But that requires a huge collector area, south orientation, optimal tilt, located in southern Germany, and a battery of 8-10 kWh (maybe even more). A huge investment for just a little more self-sufficiency. So make sure your system is precisely sized for a balanced relationship between photovoltaic capacity, battery, and household consumption.

A good photovoltaic system combined with an air/water heat pump or ground source heat pump is ideal, with a COP of 4.5–5.5.... you get a lot out of it.

Wind turbine: If you live in a windy location like I do, great. I would love to have one. Here in Wuppertal, at the model house park, there is a house with a compact 1 kW spiral-shaped generator. From my observations here, that generator would produce at least 15 kWh per day on about 270 days per year, especially when the sun isn’t shining (winter, night). If I had extra money right now, I’d put one on my roof immediately—I think it’s great. But as I said, it depends on the exact location of the house, not just the region. We live in a thermal wind corridor, so a wind turbine like that would be very effective here. If you have such a turbine and space, it’s worth considering increasing the photovoltaic battery buffer accordingly. I’m almost certain: done right, you could achieve an annual self-sufficiency rate of about 80%, maybe slightly more.

You can influence 5-10% yourself. Since I installed the S0 meter (17.04.), I have been able to track several power wasters in the house and reduce my electricity consumption by about 2.5–3 kWh (2.7–3.3 kWh) per day without much effort (reducing standby, cooking habits—the rest is already all LED and modern). I will keep fine-tuning for a few more percent (new fridge and so on).

My conclusion: If you don’t overdo it, 65-70% self-sufficiency is achievable with reasonable effort. 80% and higher is definitely possible but requires a much larger financial investment (possibly exponential increase).

Best regards,
Thorsten

PS: Excerpt of photovoltaic data from 17.04.16 to 15.05.16; April had poor weather, the self-sufficiency rate for electricity in May is 89%.


Annual consumption 240.25 kWh

Grid consumption 38.57 kWh

Self-supplied 201.68 kWh

Battery discharge 63.87 kWh

Direct consumption 137.81 kWh

Annual yield 717.64 kWh

Self-consumption 211.08 kWh

Battery charging 73.27 kWh

Grid feed-in 506.56 kWh

Self-sufficiency rate 84 %

Self-consumption rate 29 %

Direct consumption rate 19 %

PS: With a south-facing system of this size, you could achieve 12-18% more output here in this region. A hipped roof with a system oriented east/south/west would be even more optimal...

A wind turbine is an interesting option, as @T21150 already mentioned, especially in suitable regions where it can provide a solution for nighttime or the darker seasons.

However, you should clarify the following:
Is this allowed in your building area? Country, district, municipality
What about the neighbors? Could there be conflicts? Are there certain rights that need to be recorded in the land registry? (I’m not familiar with this, but I imagine that specific construction height regulations may apply. Wind turbines should generally be taller than the surrounding roof ridges.)

@T21150, I believe I read about half a year ago that a wind turbine for electricity generation is not permitted on a roof. I found the idea very interesting at the time. As far as I know, it must be a standalone installation. If it is allowed on a roof, a reinforced anchoring system would certainly be necessary to prevent the turbine from causing major damage to the house during storms.

Maybe it doesn’t have to be a wind turbine in the strict sense?

A vertical axis rotor with a capacity of 500W to 1000W should be sufficient to cover the 200-300W base load at night.

During the day, the photovoltaic system takes care of that.

You just shouldn’t run the dryer at night.

Hm @toxicmolotow.

However, after reading a bit about it just now, the efficiency is apparently much lower. This means the gap between investment and return will be quite large. Unless you are only motivated by environmental concerns, it should eventually make financial sense.

The article also mentioned another downside: “High vibrations and stresses (fluctuating blades, tower resonances).” This could potentially cause additional stress to the building and roof as well.

Too bad – the idea of energy independence is always interesting to me too.