I have an off grid solar system and I'm playing with it with a Raspberry Pi and an Arduino.

I'm looking for an automatic usage of the 12V power produced when the battery is full. (The Arduino has a sensor for voltage and my Raspberry is ready to do activate/deactivate with relays.)

Here are some ideas I had :

  1. Use a water pump to store water as potential energy 6 meters high and convert it later to power with a water turbine. (Seems really inefficient and too much investment into nothing.)

  2. Use Peltier systems to convert electricity into water for later usage. (Dehumidifier) - Didn't try yet.

What do people do usually ? I can't sell it back to the grid, I'm not connected to it.

  • \$\begingroup\$ If your net total production is greater then you net total usage then there is nothing to do other then waste it. If however you want to save some for a rainy day, add more batteries. \$\endgroup\$
    – Tyler
    Jul 31, 2019 at 21:27
  • 1
    \$\begingroup\$ How much excess power are you talking about? Water storage is useful - Dinorwig is a good example... \$\endgroup\$
    – Solar Mike
    Jul 31, 2019 at 21:34
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    \$\begingroup\$ My suggestion is to use it to destil ethanol. Storage capability is as much as you have space and then convert your gasoline generator to run on E85. \$\endgroup\$
    – winny
    Jul 31, 2019 at 21:35
  • \$\begingroup\$ Many people just burn it up as heat with a resistor \$\endgroup\$
    – Voltage Spike
    Jul 31, 2019 at 21:43
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    \$\begingroup\$ What "most people do", if they aren't connected to the grid, is they don't generate the energy in the first place (by leaving the solar panels open circuit). This wastes the energy as heat in the solar panels. Of course, they don't do that consciously; their charge controller does it automatically. \$\endgroup\$
    – user253751
    Jul 31, 2019 at 22:32

2 Answers 2


Large buildings often run chillers during off-peak to make ice, then use the ice for cooling during the day. That’s a bit opposite of what you want, but it explains the principle of using phase change to store energy.

The pump idea isn’t so dumb at all. It’s been used at larger scale in hydro dam projects to store energy during off-peak.

Simplest thing? Use the excess PV energy to heat water. It’s 100% efficient, and with a well-insulated tank the losses are low.

  • 1
    \$\begingroup\$ Still less efficient than heating water directly from sunlight, though. \$\endgroup\$
    – user253751
    Jul 31, 2019 at 22:33
  • \$\begingroup\$ Thermionic systems are more efficient for sure, but they have two issues: they only produce heat, not electricity; and they are complex to maintain. That said, water-cooled solar panels are a thing - you get double use of the rooftop space. \$\endgroup\$ Jul 31, 2019 at 22:40
  • \$\begingroup\$ About the water heating system. I already have a water heating system that is working well with black pipes on the roof. But yeah I would have done that for sure otherwise, that's a great idea. \$\endgroup\$
    – bob dylan
    Jul 31, 2019 at 23:08
  • \$\begingroup\$ About the temperature system. I ordered online some Peltier modules but I'm still looking for something that would be useful. (Using heat and/or cold) - other than dehumidifier. \$\endgroup\$
    – bob dylan
    Jul 31, 2019 at 23:13
  • \$\begingroup\$ About the pump. It's good in theory, but I think what i will be able to do is meaningless. If I had a good turbine it would be way more effective to put it on the main water pipe which has 70psi. Raising water to 6m will be about 8psi. And I need a pump, and 2 water tanks. :/ I'm not sure how much Watt i can take for a liter of water this way but i think incredibly low... And even with a 200L container it will drain very fast, so not much Ah storage if the generator can't turn for long... \$\endgroup\$
    – bob dylan
    Jul 31, 2019 at 23:20

1 - Use a water pump to store water as potential energy 6 meters high and convert it later to power with a water turbine. (Seems really inefficient and too much investment into nothing.)

You can also lift up large weight using motor/generator and later on use the potential energy of weight to generate electricity. This technology is called gravitricity.

  • \$\begingroup\$ Are you associated with the link in any way? If you are then please explain how you are, Thanks \$\endgroup\$
    – Voltage Spike
    Jun 4, 2020 at 15:33
  • \$\begingroup\$ No, but I had to mention gravitricity to verify my claims. \$\endgroup\$
    – Marino
    Jun 4, 2020 at 17:16

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