Johannes 9 kW On-Grid project

[johu]

Will start documenting something that was super popular in Germany until 2012 and is getting popular again now: a full grid export solar system that you get a fixed feed in tariff for. It's not very exciting but super common. I inquired at an engineering company to plan and build the system for me but they had no free capacity until summer 2023. So I'll do all myself except roof mounting (because high and steep and wanting to survive). I will document all formalities here as well.

Solar panels: 23 JA Solar 405W panels, 1.73x1.13m (amazed you get over 400W from the same area that you got 200W from in 2010) - 4100€ delivered
Inverter: SMA Sunny Tripower 8.0 - 1900€ delivered
Mounting rack - 1170€ delivered
Fuse box, cables etc. - 250€
Roof mounting: probably about 3000€
Electrical installation approval: 3100€
Total so far: 13520€

Feed in tariff is 0.134€/kWh and I expect yearly energy production to be around 9000 kWh. So it should pay off in around 12 years.

Prices are without VAT as that is always refunded for PV projects in Germany.

Planning
I took a screen shot off google earth with the roof tilted into the horizontal. Then whacked solar panels in there avoiding shadows. Then found out that I'd assumed the wrong width AFTER ordering the solar panels... So instead of 26 I can only fit 23. Oh well, there is no such thing as redundant solar panels, my dad will buy them off me.

Electrical installation
every other mounting profile is connected to an earthing cable. Panels are arranged as one string with an idle voltage around 850V. DC+ and DC- first go to a string box that contains surge protection and two fuses. These boxes are available cheap and pre-built, no need to build your own. Then + and - go into the inverter while the three earthing cables from inverter, roof rack and string box are collected at a common star point in the fuse box.
The inverter output runs via 3 regular fuses (because it is 3-phase) and through a bespoke energy meter into the grid. Will update that after talking to the electrician.

Cables run completely vertical all the way from the roof, through an existing cable duct, to the basement where I chose to install the inverter. Then AC cable runs back up to the house connection box. Very fun to fiddle 5x2.5mm² cable through some unknown, bendy cable duct. Old trick, first I put the flexible grounding cable in, glued the AC cable to it with some strong tape and pulled it all down.

Legalities
First you need to enquire with your municipal utility whether you there is enough capacity for another solar system. Then I chose to do most of the electrical installation myself and have an electrician do the finishing touch. He will then sign it off and instruct the utility which meter to install in which place. That is being send off and at some point they will show up and install the meters.
Before that the system must be registered with the federal network agency (Bundesnetzagentur)
Most utilities will send you a silly feed-in contract which is NOT needed as everything is regulated by federal law.

[arber333]

I have that mounted for 3 years now and it runs without any thought now.
With about 9kW i could cover annual electricity for my house and my car. But now that i installed 11kw heatpump i overspend by some 500e. Which is stil good considering energy cost for heating in winter.
Also pricing was similar at 1ke for 1kW of solar power installed.
But this year i ran into problems when i wanted to expand my solar to 13kW. Electric company refused because our grid is not strong enough. I now have lots of solar neighbours...

Well i decided to expand on my own and put panels in my garden and connecting inverter to battery. Philosophy behind this is to take the house off grid at least enough for every day use to be sustainable (wont you just love that high political wording) and thus freeing my netmetering of house consumption.

In any case if you dont get approval it is not the end of the world. You just setup system for your own house use combining with battery.

Solar paneling installed martian style...

Joint view of both installations

Volt battery in 48V configuration

I had to rewire the house, what a pain!

I got bms working...

[arber333]

A question? Do you get refunded for the kW you make vs the kW you draw? For example if at the end of the year you make 200kW positive would they reimburse you or just take that and "thank you very much"...

[johu]

Very nice, I like the battery system. Which BMS is it? Hah, why don't you add a thread for it

There are 2 (relevant) models in Germany
- self consumption and feeding in of excess power - you get about 8 ct for every kWh you feed in
- full export - every kWh goes to the grid and you get 13.4 ct/kWh

[arber333]

Very nice, I like the battery system. Which BMS is it? Hah, why don't you add a thread for it

There are 2 (relevant) models in Germany
- self consumption and feeding in of excess power - you get about 8 ct for every kWh you feed in
- full export - every kWh goes to the grid and you get 13.4 ct/kWh

In Slovenia we used to get full export too, but now only old contracts remain.
Netmetering system is accounted to sort of 8c of consumption, but they give you nothing for overproduction. How very socialist...

I will create other thread, try to find more photos and elaborate on the topic. I stil have plans to make a hsg motor into generator for one small liger diesel and make some sort of cogeneration system. That combines with openinverter would be fun...but my family might throw me out because of noise... wont know untill i try.

[johu]

The system is now installed but not yet running. A new meter box needs to be added and the utility need to mount the meter. Might be a matter of weeks. I did however give away 45 kWh to one of the tenants. System peaked at 7.3 kW, I'm guessing we'll see more when it is cooler.

[philbrennan]

Very nice, and good that the govt encourages this for so long, building a culture of feeding to the grid.
In Ireland even with a feed in tariff, people seem obsessed with batteries, past the point of economic sense ( I mean off the shelf batteries - not DIY )
I've just done install on my house, was not DIY as same as you I want to live, its a high steep roof. there is a govt subsidy which comes with strict rules on panel setback from roof boundaries, so all that would fit were 8 panels. I still think that 9 were possible but I will add more myself when the dust settles. Turns out the panels were 415w so that was some comfort - 3.3kw whereas the original quote was for 2.92 with 370w panels.

I'm intrigued with the long dc cable run on your system, does that not lead to appreciable losses? I guess not as you know these things. Gives me an idea on how I might approach my next install.
The feed in tariff is only just being activated in Ireland, I'm lucky to be with one of the more decent companies which is paying 14c, its a self consumption tariff and I've no battery. total cost 3600, 30 euros a month interest free over 10 years, it was a no brainer.

[johu]

Yes I'm very happy they make full feed in profitable again. In Germany many houses are rent out so there is no economic point for the owners to do self consumption on them. Selling electricity to tenants was a bureaucratic nightmare up until now but supposedly they made that easier as well. I think I can still change it later but for now will leave it running full feed in.

Didn't spend much thought on the cable run to be honest. It is 25m per pole, 13.5A max and 4mm² cables. Should only drop a volt or two which doesn't really matter at a 600V operating voltage

[muehlpower]

The regulation allows a maximum of 1% power loss. At 600V, 13.5A, 2x25m and 4mm² copper there is a 0.5% power loss.

[johu]

nice, thanks for checking

[philbrennan]

Nice.. yup at that voltage it isn't an issue. food for thought for my next installs which will likely have decent sized cable runs.

[johu]

You won't believe it but it actually took until today to get the system officially feeding in. Had I known this before I'd have reconsidered the feasibility...

My very naive plan was to put a digital 3-phase energy counter onto the 4th position and meter the collective electricity separately. But this is Germany. There are procedures to follow. And I hate procedures!
This cabinet is too old, as long as it remains unchanged you can use it but as soon as you change something you'd have to upgrade the entire cabinet to the latest and greatest safety standards.

So that plan was up in the air, and additional cabinet must be installed in the basement, and it's gigantic! 1.1m high and 0.8m wide or something. Now that there's a second cabinet the main power line must be spliced. Requiring yet ANOTHER cabinet with more fuses in it. And because rules it must be attached with 16mm² cable despite just 8 kW going through it. The electricians didn't seem to believe that themselves so they started out with a simple splicing box and, I think, 10mm² cable. The utility said they wouldn't place the meter because 10mm² is very unsafe! So another 2 months passed until this was all corrected.

The disastrous financial end result: 3100€ extra instead of a few 100€ could the meter have been installed in the original cabinet. Wow, just wow. German Energiewende FTW.

Will update the post above with the final cost.

[arber333]

I am not sure physics are the same for everyone on earth. We have a rule that 5x6mm2 should be enough for 10kW application. That is AC current. DC is different.

That kind of unknowns are why i make offgrid solar stations with batteries. They are considered as consumer devices. Like your fridge...

[johu]

Yeah I'm glad I just did the system in my home without needing to inform anyone. I'm sure naysayers would find plenty.

Here's a recent Swedish cabinet. I'm sure installing that doesn't set you back 3000€. And it's not 16mm² either.