Just a guy, his idea, some parts & cash and a few students.
In St. George, Utah, they don’t use furnaces to heat their homes, they use heat pumps. They work very well, even when the temps drop down into “zero” territory.
So the guy refrigerates his incoming water and sets the exhaust heat into the feed side of his hot water heater. No big deal.
He’d get better results if he tried to do the same thing with the waste water from shower, dishwasher and clothes washer drains instead of the incoming water.
However, I have my doubts that the efficiency numbers work out, or enough to justify the cost of the equipment.
If the cold water is already at 70 F, what colder water source would you transfer the heat to and why? Just fill the water heater with the 70 degree water. o.0 I must be missing something.
Extracting latent heat from one tank of water and transferring it to another is going to have a cost above and beyond the reduced heating expense in the hot water tank benefitting from the transfer. If you want colder tap water you might get it for “free,” cost of the system notwithstanding, imho.
I know that I have to use warm water for washing because cold water (as defined for washing clothes) is around 85°F while the cold water from my pipes is below 50°F in the winter and may be up to 60°F in the summer. That's not washing or rinsing anything well. If I get a new washing machine that only has a cold rinse, I'll have to premix hot and cold water before it goes into the cold washer intake.
Tankless water heaters work pretty well and save money. In three years, mine has just about paid for itself and the upgrade in electrical wiring. The wiring cost more than the heater.
Most residential users mix hot and cold to about 90-100 degrees. That is still 30-50 degrees of overall heating. I suppose it can be offset by toilets but those only use 1-1.5 gallons today.
Only the warmest places get 70 degree water out of the ground. That is far from typical in the USA. I did a project at the equator and it was 74 degrees from the ground.
There ARE already heat-pump water heaters that take heat from the air. I think those are far better. Especially if it sits inside a hot mechanical room.
I could heat my water with a few students (in shifts):
Ground source heat pumps have been around for over 100 years. They are hands over more efficient than burning fossil fuels or air to air heat pumps. Their drawback.....huge first costs.....
After a couple of test projects in the Reno area, the State of Nevada determined that they reached payback for the high initial (construction) costs in 3-5 years. Nevada now mandates usage of these type systems in many School and public buildings....
Radiant in floor heating systems are often designed with water to water ground source heat pumps to good effect......
nothing really new here as far as I can see......
I’ve found I can make money with just a cheap computer and an old color printer.
Heat pump type water heaters fail miserably in real life use; it might be a function of the number of duty cycles but I think they’re just too complex for something that needs to be 100% reliable ,It shouldn’t matter if it’s a heat pump pulling heat from air like your A/C or it’s a water to water system as this guy wants to build.
I’ve had 2 tankless electric heaters fail over a 5 year period BIG 3*60 AMP ones ,, with 3 chambers theres a lot of possible failure points and don’t try to reason with the wife when she has to take a cold shower...
What works in any climate is/are GAS tankless water heaters ... my Aunts home in Brooklyn still has their original tankless water heater from 1926 ,, just updated to eliminate the pilot light... amazingly simple , just a copper coil about 6” in diameter and 2 feet in length(THICK COPPER) inside a tube that narrows to become the chimney/exhaust.
The 1970’s/1980’s solution was to capture waste heat from the A/C pressure/liquid side with a sealed heat exchanger box... WORKED GREAT and improved A/C efficiency also... don’t know why it has fallen out of favor.
Best solution now in warm climates is passive solar heat with electric backup.
I would think that the parts of the world which have 70 degree ground water would also have plenty of sunlight and ambient air temps.
A solar hot water heater, or even just heating the pipes to ambient air temp would probably be a far better primary solution in these places.
Perhaps the groundwater heat pump could be used in the “cold” season in those areas to some effect...
Improving hot water heating efficiency ... with cold water
Why is he heating hot water?
To preheat water, solar energy is the cheapest.
Best for non-freezing climbs, the pipes can be laid right below the roof. You’ll get 150F water.
Damn near any proposal containing the word "green" can get funding these days.
It was great while it worked, if the maintenance costs were ignored. I also just dumped the cold water. There was a convenient lake nearby. The deer liked the open water. BTW, the well water was a consistent 50 degree year round. Ground water is always at the average annual temperature (or warmer).