Originally Posted by JasonC SBB (Post 1102261)

If so inclined to build one, here's my suggested control system, using an Arduino or some such:

Regulate fan speed proportionally to water outlet temperature minus ambient temperature, something like over a 5-10* band.

Regulate water flow rate proportionally to target ambient temperature minus actual ambient temperature, over say a 2* band, but clip flow when water outlet minus ambient temp is more than say 12* or 15*F.

When room is warming up fan will max out and water flow will be regulated to 15*F outlet temp over ambient. When ambient is within 2* of target, water will regulate proportionally to ambient temperature, and fan will regulate to maintain the outlet temperature to minimize heat loss in the outlet water.

Originally Posted by mgeoffriau (Post 1102235)

I use the same UPS that you do, Joe.

Originally Posted by Erat (Post 1117963)

Bump on this, it's getting warmer now. Has the new system kept up, and worked well?

Originally Posted by Stein (Post 1117981)

Also, will you be trying this with cold water in the summer?

Originally Posted by Joe Perez (Post 1117998)

The reliableness of the new system has been perfect.

Originally Posted by sixshooter (Post 1118079)

Is that anything like reliability?

Originally Posted by Joe Perez (Post 1118081)

Only superficially.

Originally Posted by sixshooter (Post 1118085)

I am meeting a friend in a few minutes for a drink and I believe I am in the mood for a cider. As an adult beverage connoisseur, would you perhaps be able to recommend a good cider?

Originally Posted by Joe Perez (Post 1118098)

I'm honestly not much of a cider fan, sorry.

Originally Posted by mx5autoxer (Post 1118779)

Strongbow if you like it dry, Woodchuck if you're a woman.

You could build a tiny hydroelectric dam in your tub.

https://www.miataturbo.net/attachmen...ine=1397062515

It would generate power, though not very much of it. The formula for power is pressure times flow rate. Since bathtubs are pretty shallow, the pressure at the bottom isn't very high, so this works out to around two watts of power, or about 25 cents per month.

https://www.miataturbo.net/attachmen...ine=1397062515

You can get more power if you increase the pressure of the water passing through the generator. To do this, you could increasing the depth of the water. If you have two floors in your apartment, you could have the water column stretch from the second to the first floor, generating at least ten times the pressure and ten times the power. In effect, the local authorities would be paying to pump the water up to your apartment, and you're getting some of that energy back when you let it flow back down.

https://www.miataturbo.net/attachmen...ine=1397062515

Could you use the faucet to pump the water up arbitrarily high, and get more and more power out of it as it falls back down?

https://www.miataturbo.net/attachmen...ine=1397062515

No. First, you couldn't pump the water arbitrarily high. Household faucets have a pressure of around 4 atmospheres.[3] You can lift water about 10 meters per atmosphere of pressure, which means that a household faucet can only pump water up by about 40 meters.

Second, as you can probably guess by looking at the above picture, pumping the water up 40 meters with water pressure and then back down doesn't accomplish anything—you can just hook the faucet up to your device, and let the water pressure drive the generator directly. In either case, for a bathtub faucet, this works out to almost 200 watts, or $25 per month.

You'd have to make sure your plumbing could handle the water. If your pipes get plugged up and stop draining, the faucet could fill your house in a matter of days. And either way, eventually someone from the city would probably show up to ask why you're using 40 tons of water every day.

https://www.miataturbo.net/attachmen...ine=1397062515

And really, with California suffering through its worst drought in history, this system might earn you some dirty looks. Sure, if you live far away from California, it's not like your water would have gone to ease their drought, but wasting a gigantic amount of water (and investing a bunch of money) to save a few dollars on your electricity bill might come across as a little rude.

A bathtub's flow rate is five or six orders of magnitude less than that of a river, but it's still a lot of water. Could we put it to a less selfish use?

There's a common piece of advice that says you should drink 8 glasses of water a day. No one really knows where this advice came from; people claim you should drink anywhere from 2 to 12 glasses of water daily,[4] and none of them have any real evidence behind them. The only real solid advice I've heard is that if you're thirsty, you should drink some water.

If we stick to the "8 glasses of water" standard, then a bathtub faucet provides enough drinking water to sustain about 10,000 people indefinitely. In other words, the city of Manhattan could survive on the water from just 150 bathtubs.

https://www.miataturbo.net/attachmen...ine=1397062515

But if your goal is to save money on your electric bill, there's a much more lucrative option.

Single servings of bottled water sells for a dollar or two per half-liter. A lot of bottled water comes from municipal sources—that is, it's tap water. Bottled water isn't necessarily about the water; often, people are paying for convenience or because there's an issue with their water supply. Whatever the reason, however, there's no reason to let Coca Cola keep all the profits.

If you bottled the water from your bathtub faucet and managed to sell each bottle for $1.50, you'd make $72 per minute—$38 million every year.

https://www.miataturbo.net/attachmen...ine=1397062515

Then you won't have to worry about your power bill.