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Comment by Gasp0de | Hacker News Reader

This doesn't seem cost efficient at all, my (medium sized) house in Germany consumes about 3000kWh of electricity during winter. This does not include heating, which consumes another 15.000kWh (of heat energy from oil, so around 5000kWh electrical energy with a heat pump).

If I were to use this battery I would need to get 3000(8000)kWh of energy storage at 23$ per kWh which would amount to 69000(184000)$. There are better hydrogen-based solutions for that cost. Also, did I read correctly that I have to keep the battery heated to 180°C during discharge? This is going to waste a lot of energy in winter.

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You're assuming that the battery needs to store the total energy requirements of a house for the entire year. Much of the time the energy needs can be met by conventional energy generation (wind turbines, solar, hydro, etc) and the battery is only called upon when there's a shortfall. So you'd only need a fraction of the annual consumption to make it useful. The whole idea is to make renewables more effective by storing the excess. Grid storage will be an important part of the transition to renewables.

But yes, it is expensive, but it's only at the R&D stage. I'm sure could be made cheaper, and the article mentions reducing the cost to $6/kWh.

If you use solar power in a climate like Germany you will get that kind of math.

Let's say you use 8000 kwh per year, and you have the solar capacity to create 8000 kwh per year. Assume you already have a normal home battery of ~14kwh so day/night is not an issue, the solar production during daytime charges the battery and all night time power comes from the battery.

Now your big problem is that 70% of the 8000 kwh solar per year is produced from May to September. You need 670 kwh per month for usage, so in those four months you have just under 3000 kwh too much. Then in April and October the panels roughly produce what you use. And November to March you have a total shortfall of 3000 kwh.

So you need seasonal storage capacity of about 3000 kwh to be able to run an 8000 kwh yearly usage on solar in this climate.

The other option is to buy much more solar panel capacity than you need, then you can use a smaller battery which in total could be cheaper since solar panels aren't that expensive anymore.

> The other option is to buy much more solar panel capacity than you need,

You need the space to install them also. I have a 6.6kW array, and would need 3x that capacity to heat my home using electrically-powered air source heat pumps during the winter months. Even with 0.75 acres / 0.30 hectares, that would be quite a lot of my property covered by panels, and way more than could ever feasibly fit on the roof (the current array is ground mount).

Good roof space may become a sales argument for houses in the future. Mine happens to have a huge flat roof slightly sloped to the south. I have 8 kW solar and that’s less than half the roof covered.

I use 6000/8000kWh between September and May though, because that is when I'm using a Heatpump to generate electricity.

The economics is not great as described, but I wouldn't see this at being an individual level solution. The larger it is, the easier it is to insulate.

You heat you house with oil? I thought Germany was environmentally conscious

It's called "greenwashing". A fair bit of electricity is produced with solar (at a far higher cost than their neighbor's carbon-free electricity) but their gasoline and diesel vehicle manufacturing continues unbounded and their heat primarily comes from fossil fuel.

Germany is still mining coal but they are environment conscious so they sell it to Poland to burn and buy electricity from them.

That seems like complete bullshit, since Germany doesn't mine anything apart from lignite, which can't feasibly be transported. Do you perhaps have a source on coal export to Poland? Also, Germany exports more electricity than it imports.

Unfortunately, Germany has been ruled by a conservative party for the last 16 years and they did everything in their power to sabotage renewable energy so that lignite mining could stay longer.

However, heating in Germany is a difficult problem to solve with renewable energy: You need lots of power in winter, when there is (close to) no power from solar. One solution would be excessive wind power and heat pumps that can be controlled remotely by the power grid operators.

Gosh, it's still coming out of academia. It takes awhile before these kinds of things are economically viable.

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