Using Rainwater and Sewage for Power

While this summer Minnesota apparently had the worst drought since 1988 (Not that I noticed–it just meant I didn’t have to mow the grass as often), September and October have had three to four times the normal amount of rain. It has rained almost every day in October. We’re beyond raining cats and dogs.

So one night a few weeks ago I was lying awake in my bed listening to the rain splatter on my roof and pour out of my gutters. And an idea came to me–if we harness rivers and waterfalls and build dams to create hydroelectric power, why couldn’t we do the same and generate electricity from the rain that falls from the sky?

You’d need to get the rainwater to turn a turbine or wheel to generate electricity. Seems simple enough to modify a downspout so it has the right equipment. You might need to pool all the water in one spout so you can maximize your power and it might be handy to collect the water in a rain barrel so you can store up enough water to make it worth spinning the wheel (for those wussy rains that don’t amount to much water). And you could probably put another rain barrel at the bottom end so you can reuse the rainwater for gardening, but that’s another story.

It would obviously be a pretty weak turbine and we’re not talking about generating lots of power. I have no idea how turbines and generators and such work, but I would guess we’re talking less than 5% of a home’s energy needs. Maybe less than 1%. The whole system would need to be very cheap and simple to pay for itself. But imagine if every home could generate that little bit of power. That 1% isn’t much, but if every house on the block is generating that 1% it starts to add up. Best of all it’s a completely free and renewable resource that otherwise just spills out the gutter as waste.

And that got me thinking. If we could generate power from falling water, where else do we have falling water that we’re not taking advantage of? Every time you flush the toilet or take a shower water is rushing to the lowest point–down your drain. Using the same idea I wonder if it’d be possible to install some sort of power generator in the main drain stack of your house and generate electricity every time you flush the toilet or wash the dishes?

It’d have to be more of a robust system, since there’d be solids and such in the water–you might even need to have some filtering system to avoid clogs or a bypass so you don’t even deal with the solids (two drain stacks?). But those seem like minor engineering problems. In general you’ve got water falling and it could easily be used to generate power. And you can’t just turn on your faucet to generate power–that’d be wasting it, since the water from your faucet is pumped from somewhere and that takes energy. But once you use the water and that water pressure is lost the water just falls down the drain. Why not put it to work while it’s falling?

I’m not an engineer and I have no idea how practical these ideas are. But it seems to me not many systems we create are very practical. Have you ever looked at how complicated it is under the hood of a car? An internal combustion engine creates a lot of problems, and there are a lot of systems under the hood to deal with those problems. Getting energy out of wasted water seems like the same kind of thing. The end result might be worth some complication.

As a side note, I have heard of systems that recapture heat from drain water, but I haven’t heard anything like this before. My guess is that there simply isn’t enough water falling a great enough distance to generate enough power to make it worthwhile. But it seems like even if there’s a little bit and you multiply that by all the buildings that have drains and get rained on, and it seems like there might be something there.

2 thoughts on “Using Rainwater and Sewage for Power”

  1. great idea, kevin! I don’t think I’ve ever heard of anything like this, but I think it’s a good one.
    Is our governer still having that invention fair?

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