What size battery is needed to power the house?

Tesla Batteries

Tesla announces battery development for home use. Cool. But why? Here are a couple of options:

- autonomous house, powered by solar or wind energy. These sources do not provide a constant flow of energy, which means that it should be stored somewhere.
- Many homeowners keep a diesel or gasoline generator. It is used infrequently, but when it is suddenly needed, it is irreplaceable. You can use a battery instead of a generator
- The electricity supplier company would like everyone to have batteries. Then it would be possible to reduce the peak load on the network. For example, when you turn on the air conditioner or other consumers.
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But what size should a battery have to meet our needs?

How long should the battery be able to work? Mask said something about the week. OK. Now - energy consumption. I will make an assumption - 2000 watts of constant consumption. Of course, sometimes you need more, but sometimes less. On average, let it be 2 kW. If you are confused by this figure, you can easily substitute your own.



A watt is a joule per second, so the time is recalculated for seconds.



Now you can calculate the amount of energy stored in the battery.



To imagine how much energy is in Joule, let's do an experiment. Take the book and place it on the floor. Now lift and place on the table. To raise a book, you spent energy (increasing its potential energy in a gravitational field). A book weighing a kilogram raised to 1 meter receives an energy of about 10 Joules.

Let's go back to the batteries. The size of the battery depends on its type. Tesla has lithium-ion batteries. According to Wikipedia , the energy density of such a battery is 0.9 - 2.23 MJ / l (megajoules per liter). Let's say Tesla will supply the best batteries in the world. Then the cubic meter of the battery will contain 2.3 * 10 ⁹ Joules.

Denote the energy density as σ, and the volume as V:



Substitute the known values:



We get about half a cubic meter. Not bad. In the house in general, you can make it to the height of the ceilings, somewhere 2.5 meters. And for beauty we will make a battery 10 cm thick. Then its width should be about 2 meters. It might work.

For fun, it is estimated here that they need about 40 cubic meters to power the house from the “tablet” batteries. And also you can calculate for the warm-up yourself:

- How many AA batteries will be needed to power the house and how much volume will they take? We can assume that it stores about 10 KJ of energy .
- if you decided to power your home from a nuclear plant operating on a torium, how much thorium would you need? Energy density can be taken from wikipedia
- since Apple decided to build a 130 MW solar power plant for internal use, can you calculate what size of panel you would need to power your own home? Suppose that the Sun produces 1 kW of energy per square meter, and the efficiency of the panel is 25%. Do not forget that during the day the angle of incidence of the rays changes. In calculations this post can be useful.

This is a translation of the article. As you know, the best way to learn something on the Internet is to post the wrong answer. In this regard, taking this opportunity, I would love to listen to stories about how you made a power supply system, backup or standalone, in your home.