Energy self-sufficiency - Offers

Google "Sonnenhaus" for heating - household electricity could then be covered with photovoltaics and battery (not sure if it’s enough completely). Economically, however, it is not necessarily all that viable...

PS: For tips & tricks regarding energy self-sufficiency, feel free to contact me anytime!

Hi Franz,

I also upgraded. An O/W photovoltaic system with a nominal 6.625 kWp. 11 collectors at 265 W east, 14 west. With a tiny buffer battery, 2 kWh. The integrated inverter/battery system is from SMA. I reached 78% self-sufficiency in April (the system has been installed since 07.04., the S0 meter since 17.04.) and 84% so far in May as of today.

There are solar irradiance calculators on the internet. With them, I can quite well see where the journey is headed: As calculated, an average of about 50% self-sufficiency per year.

If you increase the battery capacity, you also increase (charge/discharge) losses slightly. The battery capacity must always be adjusted to household habits/consumption. A small battery always makes sense, it immediately and sharply increases the self-sufficiency rate. A battery that is too large, on the other hand, makes less sense.

Supplying the house overnight: Only low power is required, and efficiency is also lower. The efficiency increases with high withdrawal power. I also see this on my system which nominally achieves 97%, but at 150-400 watts at night, it operates at about 85-90%.

From April to October, usually enough energy comes from above anyway, if the photovoltaic system is well and adequately sized. After that: slim pickings. You can say, based on my research: even with a large battery you reach about 60-80 % maximum. But at that point, the collector area is already huge, facing south, optimal tilt, southern Germany, and the battery is 8-10 kWh, maybe even more. Huge investment for little more self-sufficiency. So make sure your system is exactly sized, so that the balance between photovoltaic power, battery, and household consumption is appropriate.

A good photovoltaic system combined with a WWWP or brine-water heat pump is of course optimal, with a COP of 4.5-5.5… you get a lot out of it.

Wind turbine: If you live wind-exposed like me: great. I would love to have one. Here in Wuppertal in the model house park there is a house with a cool 1 kW spiral generator. From my observations here in my area, the generator would produce at least 15 kWh per day on 270 days per year, especially when the sun does not shine (winter, night). If I had money left over: such a device would go immediately on my roof, I think it’s great. But as I said, it depends on where you live. Not the region but exactly where the house stands (we live here in a thermal wind corridor, here such a wind turbine would be turbo effective). If you have such a turbine and space, the consideration/calculation would be to expand the photovoltaic buffer battery by a meaningful size. I am almost sure: done right, you can achieve an annual self-sufficiency rate of about 80% with this, maybe even a little more.

You can do about 5-10% yourself. Since I have had the S0 meter (17.04.), I have addressed one or two big power consumers in the house and so further reduced my electricity consumption by about 2.5-3 kWh/day without much effort (further standby, cooking habits – the rest here is already all LED and modern). I will keep fine-tuning, for a few % (new fridge and so on).

My conclusion: If you don’t overdo it, you can achieve 65-70 % self-sufficiency with reasonable effort. 80 % and more is definitely possible, but the financial effort increases sharply (exponentially?) for that.

Best regards
Thorsten

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

Annual consumption 240.25 kWh

Grid import 38.57 kWh

Self-supply 201.68 kWh

Battery discharge 63.87 kWh

Direct consumption 137.81 kWh

Annual yield 717.64 kWh

Self-consumption 211.08 kWh

Battery charge 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 that size, 12-18% more would be possible here in the region. Even better would be a hip roof with an E/S/W system there.......

A wind turbine is an interesting thing, as already wrote, it provides a solution for the night / the dark season in suitable regions.

You should clarify the following:
Is something like this allowed in your building area? Country, district, municipality
What about neighbors? Could there be trouble? Do certain rights need to be recorded in the land register (I’m not familiar with this. But I can imagine that certain building height requirements might arise. Wind turbines should be higher than the surrounding roof ridges).

I think I read about half a year ago that a wind turbine for power generation is not allowed on a roof. I found the idea very interesting back then. To my knowledge, it has to be stand alone. If it is allowed on the roof after all, you definitely have to plan for reinforced anchoring so that the wind turbine doesn’t tear half the house down in a storm.

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

A vertical rotor with 500W-1000W output should be enough to cover the 200-300W base load at night.

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

You just shouldn’t run the dryer at night.

Hm . However, after having just read something about it, the efficiency is apparently significantly lower. Thus, the gap between investment & return will widen considerably. Unless you are solely following a green soul, it really has to pay off at some point. Furthermore, the article stated that another disadvantage is "High vibrations and stresses (fluctuating blades, mast resonances)". Therefore, this could also potentially lead to stress on the building and roof. It's a pity – the idea of self-sufficiency is always interesting to me as well.