Germany Finances Major Push Into Home Battery Storage For Solar

mdsolar writes with this bit of news from Green Tech Media "The German government has responded to the next big challenge in its energy transition – storing the output from the solar boom it has created — by doing exactly what it has successfully done to date: greasing the wheels of finance to bring down the cost of new technology. ... Now it is looking at bringing down the cost of the next piece in the puzzle of its energy transition — battery storage. ... KfW’s aim, according to Axel Nawrath, a member of the KfW Bankengruppe executive board, is to ensure that the output of wind and solar must be 'more decoupled' from the grid. ... This is seen as critical as the level of renewable penetration rises to around 40 per cent — a level expected in Germany within the next 10 years. ... According to Papenfuss, households participating in the scheme will spend between €20,000 and €28,000 on solar and storage, depending on the size of the system (the average size is expected to be around 7kW for the solar array and around 4kWh for the battery)."

Re:so green

[sribe]

The problem, as always, is that's it not "just a battery", but "battery with charger with load monitor with safety protection with replacement batteries every few years", which greatly adds to the cost.

Perhaps this would be a use case for nickel-iron batteries? They have an extremely long life; the reason they fell out of use is because of low energy density and poor charge retention. But energy density matters much less in your crawl space than it does in your tablet or your car, and for this use, being able to hold a charge for only a few days would be fine.

skeptical of home batteries for large-scale use

[Trepidity]

I agree with the general drive towards decoupling immediate production vs. use with better energy storage, but even with improved battery technology, everyone having batteries in their house is a particularly inefficient (and high-maintenance) way of doing it. Better approaches need quite large sinks for excess energy. For example, pumped-storage hydro [wikipedia.org] is good for very large amounts. For medium-sized amounts, especially transient spikes, Denmark is experimenting with (PDF) [ramboll.com] dumping the excess production into district heating, since the heat reservoir handles fluctuations better than the grid does.

Better prediction and integration between sources can also help. For example, Denmark is largely managing its fluctuating wind energy these days not by literally storing it, but by predicting much of the variation, and offsetting discretionary production within the integrated Nordic energy market. What mostly happens is that on high-wind days, Sweden and Norway just reduce production at their hydro plants, and use the excess Danish wind power instead. In a sense the excess wind therefore gets stored as potential energy in the hydro reservoirs, but just by not producing the hydro in the first place, rather than pump-storage.

Re:Disaster waiting to happen

[JaredOfEuropa]

Nothing, until there's many so people dumping power into the grid that buying it from you at the fixed market rates becomes economically unsustainable. That's what is happening in Germany right now; utilities are complaining at having to buy this power and having no place to send it (we in NL have been buying it on the cheap, not that the consumer will notice this on their bill, but still). Since the utilities also have to run regular power plants for peak loads, their costs have soared. Electricity in Germany is expensive these days.

Unless they come up with a viable storage option, either in the home or in the neighbourhood, I expect the price of the power you sell back to the grid to drop sharply in the coming years.

Re:Disaster waiting to happen

[taiwanjohn]

Ditto! Liquid metal (aka: molten salt) batteries are NOT about thermal storage, they are for storing electricity. You (the GP) are thinking of the molten salt systems used in concentrating solar-thermal power plants (aka: solar tower). Check dmbasso's link (above) for more info on liquid-metal battery tech.

Dr. Sadoway has been working with Khosla Ventures the last few years, commercializing this stuff. They expect to begin beta-test field trials with customers next spring, and hope to be in full production by the end of 2014. Khosla is also backing a compressed air solution that uses a sort of water carburetor to achieve isothermal compression (solving an old bugbear of compressed air, the loss of energy to heat).

In short, there are robust, inexpensive storage solutions in the pipeline. (And not a moment too soon.) This will radically alter the "landscape" of renewable energy. When you can couple dirt-cheap solar PV with dirt-cheap storage, you have a recipe for rapid transition.