Ask HN: Ideas for useful uses of excess electricity?

5 points by mogoman 3 years ago | 19 comments

I'm trying to think up ideas of what I could do with an intermittent "excess" of electricity - only at certain hours of the day up to a certain (fixed) amount. Let's say around 10kW hours a day between 12pm and 3pm (I've described my case below, but other people would have different scenarios).

Ideally the extra energy would be used to help reduce environmental impact rather than making money, so crypto mining (for example) is not an option.

Here are some of my thoughts:

- heat water for home usage (heat pump); this solution is already deployed, but there is only so much hot water one needs - charge an EV; I don't own one presently, but it an option for the future - fight the current 70% rule in Germany (this is the cause of my excess, see below) - generate H2 via electrolysis; not sure what to do with H2 then. What would be interesting would be to be able to "charge" fuel cells and store them for use in winter, or compress H2 into cylinders? Not sure what can fit into my garage / would be affordable. - pumped water storage; I suspect the energies involved at home are insignificant vs industrial hydro solutions - convert to microwave and beam into space - run an industrial press to compress my lawn cuttings / garden waste into pellets and dump them into a deep lake - a magical machine that extracts Co2 from the air and produces a fine black powder which I could compress and dump into a deep lake - ...

Some background:

In Germany, excess domestic solar panel production can be pushed into the grid for a small (cash) refund, but there is a strange rule : only 70% of the maximum panel output is allowed to be pushed. So if the panels could generate 10kW at midday, without anything turned on at home, a maximum of 7kW can be pushed. This effect is only for a few "peak sun" hours (say 12pm to 3pm), but means that roughly 10kW hours of electricity is "lost" (the system is throttled back via the charge controller, so the energy isn't lost or wasted, it just isn't produced)

HWR_14 3 years ago |

I mean, wouldn't the simple and easy solution be to store that 30% energy and use it at night to reduce your load then? A quick search suggests home battery systems that store 30kw hrs might be around 9,000 euro. Plus the various inverters, etc.

Reducing peak load has to be more efficient than removing the CO2 after the fact, at least until that load is no longer generated by fossil fuels. It also lets you reduce your country's dependence on said fossil fuels which has been a hot button for the past few months.

mogoman 3 years ago | |

Sure, 30kW storage is fine, but it implies you use all the energy every day (or night). In the summer months my current set up uses basically 0 grid hours (as I already have some storage for night time). The 30% really is an excess after storage, running home appliance, charging batteries etc.

HWR_14 3 years ago | | |

If you store 30% for 3 hours, that's 90% of peak generation. It seems, by law, you could then finish selling that excess power for the next ~1.3 hours at your maximum rate (less storage inefficiencies).

You could figure out what time of day rates are highest, because that would imply you're releasing the most pressure on fossil fuel generators.

toomuchtodo 3 years ago |

Buying an EV and charging during daytime hours when export is restricted is the most cost effective mechanism for consuming this excess solar generation if batteries for storage and consumption aren't an option.

Too much clean energy is a great problem to have.

mogoman 3 years ago | |

Fully agree, this is probably the most viable future option.

Kon-Peki 3 years ago |

Do you have an electric oven? Bake fresh bread (or other food) for yourself and your neighbors.

Fresher, healthier, lower transportation costs, etc.

mogoman 3 years ago | |

I LOVE the simplicity of it!

Kon-Peki 3 years ago | | |

When I was younger, one of the parents in the neighborhood was a bread delivery driver. I can still remember her ranting about an incident one snowy winter day. She couldn't drive as fast as all the other trucks on the highway and they were complaining to her over the radio. Her response was "I have no traction, I'm hauling a load of bread!"

A truck carrying bread is pretty close to the weight of an empty truck. The fuel efficiency of this truck is better than a truck hauling a load of flour. But... my guess is that per kilogram of cargo, hauling flour is much more fuel efficient than hauling bread and therefore it is better for the environment to haul flour around and then bake the bread as close to the source of consumption as possible.

35mm 3 years ago |

Like you suggested, convert to Hydrogen[1] to store for winter or filling a H2 EV.

https://newatlas.com/energy/lavo-home-hydrogen-battery-stora...

f0e4c2f7 3 years ago |

You could mine crypto and donate the proceeds to environmental causes.

ZeroGravitas 3 years ago |

When you say "is already deployed" are you saying that you have a heat pump already and that it is set to run based on when the excess electricity is available?

How much is left after that usage?

If you fit an EV charger for future use you could allow access to friends/neighbours at the specific times until you need it yourself.

mogoman 3 years ago | |

I have a heat pump driven boiler and I do run it when the excess is available - it uses 500W, so I'm still left with a potential 2-2.5kW. I can of course set the boiler hotter, but then I'm just wearing out the components to lose the heat at night (since I don't need so much hot water).

I do have an EV charger, but no nearby neighbours yet with EVs.

However "sharing the excess" is an interesting idea, since everyone needs electricity. I could run an extension cable to the neighbour and let him run his washer/dryer from it at peak times.

perrygeo 3 years ago |

If you've got property with a slope you can build a gravity battery. Pump water and store it uphill, later release the water and spin a turbine to recover a portion of the energy.

mogoman 3 years ago | |

Would pumping up into a tank in the roof work? Any idea of the amount of energy vs weight can be stored?

toomuchtodo 3 years ago | | |

https://hackaday.com/2021/10/08/power-your-home-with-a-water...

https://youtu.be/CMR9z9Xr8GM

Nextgrid 3 years ago |

Nothing wrong with mining crypto using energy that would otherwise be wasted anyway (absorbed and then dissipated as heat back in the surrounding environment).

euroderf 3 years ago |

The obvious answer is smelting bauxite into aluminum. It is so energy-intensive that it is done in Iceland of all places. Iceland itself has no bauxite mines.

endisneigh 3 years ago |

Modify physical things:

- distill water - filter water - 3D print objects

Etc