Total power to run it is now down to about 3.5 amps from a 24v solar panel.... usually about 1.5-2lpm. Long summer days you can get in the >1000liters per day.....
Goodness. I have 3.5 acre-feet / year water right at the Nevada place. That could deliver a tenth of it as battery-grade water.
A near-dewpoint water chiller could get me air conditioning at about 4 gallons / day / ton refrigeration (TR), and using neraly deionized water I wouldn't have to blow down anywhere near an additional gallon or two per TR
to keep the heat exchangers clean.
I'm curious: What is the brand/model of the reverse-osmosis device, and what does it take for maintenance?
winter only about 500........... Colder water and shorter days. ( viscosity goes up as temp drops.)
That thing's running just under a hundred watts. Almost none of it is spent replacing the heat of solution from extracting the salts/minerals from the water, so that's nearly a hundred watts of heat. Much of it ends up in the product and waste water.
Seems to me you could build a counter-current heat exchanger out of a few feet of copper pipe and use the heat i the output water to warm the incoming raw water in the winter, and get your winter production up to the summer levels for essentially free. (It also cools the product water.)
With a hundred watts of heat your exchanger doesn't have to be TOO efficient. Your main problem would be keeping it from getting TOO warm for the reverse osmosis machine - which you could avoid by using a mixing valve between the heat-exchanger output raw water and a bypass. (I'd try to find something like a thermal - rather than a pressure-balancing - shower control valve to automate that. Since it's futzing around with the INPUT water you don't even have to worry about the valve metal contaminating the output water, because the ions won't make it through the filter.)
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Though it isn't timely, one thing I've been looking for is the patent for an invention I heard of many years ago. It was a very efficient water purification still - so efficient at scavenging heat that the inventor at first had the patent application rejected as supposedly being a perpetual motion machine.
Basic idea was twofold:
First it was a low pressure still. It achieved this by being tall - in the 30 foot range. The vacuum was provided by the weight of the water in the up and down plumbing. The condensed product and waste water pulled the vacuum, which also pulled up the raw water. At low pressure it takes a LOT less heat to boil the water.
Second, the product and waste flows down vs. the raw water up were in a counter-current heat exchanger, scavenging nearly all the heat to be reused. (In principle, if this heat exchanger and the insulation around the whole thing were 100% efficient, you'd only have to provide the heat of solution lost to purifying the water. In practice they're not, so you need to add more. But it's FAR less than you'd need to boil away that water at atmospheric pressure.)
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I seem to be haunted by counter-current heat exchangers these days:
- The near-dewpoint chiller uses up to four:
- Air-water, to pre-cool the air and preheat the water before they hit the evaporator packing.
- The evaporator packing itself is counter-current and does some heat exchange: Water flows down, air up.
- A water-water isolator if the chill water loop to the cold air delivery is not also the contaminant-exposed evaporative loop water.
- A water-air exchanger to cool the air using the chill water. That really needs to be counter-current if you're in an environment where the dewpoint is only 20ish degrees below the desired room temp.
(A nice thing about dewpoint evaporative systems is that, unless you have a HELL of a big water vapor source in the conditioned space, the air cooling coils don't get cold enough to generate condensation that needs to be disposed of.)
- Two for the reverse-osmosis filter suggestion. (One using the product water, the other the waste water, to preheat the raw water.)
- One for the highly-efficient still.