Comment by hagbard_c | Hacker News Reader

Comment by hagbard_c | Hacker News Reader

Parent Full thread

Don't give energy away to the operator, they don't (want to) give you energy for free either. Get something which can soak up excess energy - a battery, an electric water heater, whatever - and run that on whatever excess energy you have. Assuming you don't invest too much money in such a project you'll end up saving a bit more money and you'll avoid being fined for pushing energy into an already overloaded network once everyone and his dog have installed solar which pushes up the voltage from nominal 230VAC to somewhere around 245-250VAC (250VAC is the usual cutoff for inverters where I live (Sweden)).

I installed 14.5 kW of PV panels on the barn roof a few years ago and hooked them up to a 10 kW hybrid inverter. Hybrid inverters can divert energy (from the PV panels or from the net) to a battery which can be used at a later stage to feed consumers in the local installation or to backfeed to the net. Since we currently have a contract which allows us to sell energy at market rates we do not have a battery yet but I don't know yet what the next contract (in 2 years) will look like. Assuming that we can no longer sell at market rates I'll install around 60-80 kWh in battery capacity to soak up excess production and dump the rest in the water heater etc. If we ever get a hybrid or electric car/tractor/whatever I'll add battery capacity so as to be able to charge those with excess energy. By that time we'll be close to ready to go off-grid which is fine by me, electricity prices here in Sweden have skyrocketed due to the demand from (mostly) Germany for excess capacity since you shut down your nuclear power plants. The more transmission capacity is built in the Baltic, the higher our prices get.

A battery isn't profitable for me atm, and I have no problem giving the electricity away.

Do you have a source that shows that shutting down nuclear power plants has in any way influenced German power import? I'd doubt that. Power is imported when it is cheaper to import it than produce it ourselves (there has not been a situation yet where Germany couldn't meet it's own demand).

You're answering your own question here:

Power is imported when it is cheaper to import it than produce it ourselves

After shutting down the remaining 6, then 3 nuclear power plants it became cheaper to import power from Sweden - which used to be blessed with relatively low electricity prices due to to the large hydro and (diminishing) nuclear generation capacity - than to generate it in Germany. While this might have been positive for Germany and for electricity producers in Sweden it is a definite negative for electricity users in Sweden who have seen their prices skyrocket. As to the direct effects of the nuclear shutdown there's quite a bit written, e.g.

https://www.cleanenergywire.org/factsheets/qa-germanys-nucle...

4) What changed in electricity imports and why?

For the first time in many years, Germany became a net electricity importer in 2023. The trade balance for electricity switched from 21 TWh of exports to 22 TWh of imports in the same period. Imports have risen despite sufficient plant capacity in Germany to cover domestic demand entirely. In March 2024, the country announced the shutdown of seven more coal-fired power plant units after the winter, as they are no longer needed to guarantee supply security.

This leaves aside other costs involved with the nuclear phase-out [1] and the knock-on effects of the increased energy prices as well as lower guaranteed availability which is part of the cause of German deindustrialisation. If you doubt whether this actually happening I invite you to peruse a search engine of your preference on the subject which is more effective than me linking to a number of articles from many different sources.

[1] https://olivierdeschenes.weebly.com/uploads/1/3/5/0/13506865...

Why did you quote something that basically repeats the argument of the person you replied to?

> Imports have risen despite sufficient plant capacity in Germany to cover domestic demand entirely. In March 2024, the country announced the shutdown of seven more coal-fired power plant units after the winter, as they are no longer needed to guarantee supply security.

> Why did you quote something that basically repeats the argument of the person you replied to?

Because it answers his question and it is relevant in the context of Germany shutting down its nuclear power plants since this created a gap which needed to be filled with imports. Had those plants not been shut down there would not be a need to import power at the scale Germany currently does, especially not given the fact that power from existing nuclear power plants running on an existing load of nuclear fuel is far cheaper than imported power. With nuclear power the large majority of costs are concentrated in the construction phase - including all the costs incurred due to regulations - as well as the decommissioning stage. Fuel costs - including those of treating and storing nuclear waste - are but a fraction of the total costs. This means that once you have a working nuclear power plant you want to run the thing at full capacity as long as possible to recoup those initial costs and to earn income to finance the decommissioning of the plant at the end of its life. The plants which were shut down were not at the end of their useful lifetimes and could have produced many TWh of energy still - e.g. Isar 2 produced around 11 billion kWh per year and supplied around 3.5 million households with electricity which it could have continued to do for many years still.

BTW, on the subject of batteries being too expensive it might be an interesting experiment to see how far you'd get using a common full sine wave UPS with a number of external batteries. Charge the external batteries using the inverter, pull power out of the UPS. Expenditure would consists of a UPS - you'll find these on auction sites, often without or with expired battery packs - and a number of batteries. A reasonably-sized UPS which can deliver a kilowatt or more often uses 24/48/72 volt battery packs, i.e. 2 to 6 lead-acid batteries in series. If you have a way of getting these for a reasonable price it may be worth experimenting with if you're the experimenting type (I am).

Our inverter is built for high-voltage batteries (120V to 580V) so I'm aiming for either using expired EV batteries or - once prices go down more - LiFePO4 battery stacks. As it stands prices are still too high which - calculated over the life span of the batteries combined with compound interest on the investment - makes power from such batteries cost around the same as power taken from the 'net. Battery prices are steadily going down so this situation should change, hopefully within 3 years they'll have gone down so far as to make it a worthwhile investment.

A UPS isn't designed to run continuously. It will overheat and die.

An on-line UPS is designed to run continuously. Equipment connected to such devices never directly connect to utility power, they always run off the UPS which uses double conversion (AC -> DC) to charge the batteries and (DC -> AC) run the outlets. You'll find off-lease online UPSes on auction sites, as said often without their battery packs but given that you'll want to run them using bigger batteries than normal that is not a problem.

You're right. I forgot about those.

Reply on news.ycombinator.com