Improving hot water heating efficiency ... with cold water
 

Apart from heating and cooling the house, water heating is one of the biggest energy drains in the average home. But what if you could literally use cold water to create hot water? That’s just what San Diego inventor Hal Slater claims to have done with the creation of a water heater system that promises to improve water heating efficiency by as much as 50 to 100 percent.

The system works on the basis that cold water supplied to households in temperate climates averages around 70° F (21° C), which the researchers say is 15° to 20° F (8° to 11° C) warmer than it needs to be. By using a small water-to-water heat pump, the system extracts this excess heat from water in a 20-gallon (76 liter) cold water tank and delivers it to a typical 50-gallon (189-liter) water heater.

With funding from a grant from the California Energy Commission, Slater teamed up with a research team from the University of California, San Diego (UCSD), led by Dr. Jan Kleissl of the Mechanical and Aerospace Engineering Department, to test the system. To test real-world performance and determine the effects of different incoming cold water temperatures, they installed three prototype systems in homes in coastal, mountain and desert climates. They also monitored each system for a year to compare performance over different seasons.

Slater told us that all the systems performed better during the summer months when the cold water comes in at over 80° F (26° C), providing more heat that can be extracted. In the winter months in the mountain test home, the incoming water temperature dropped to 55° F (13° C), which is the temperature the cold water tanks are set to. The system basically reverts to an electric water heater at those times.

According to Slater, test results showed an improvement in water heating efficiency by as much as 50 percent over current efficiency leading air-source heat pump water heaters, such as the GE Geospring. However, he believes that with additional refinements the efficiency can be increased to 100 percent, putting it on a par with the best solar water heaters, but without the need for a rooftop solar panel.

Slater has patented the system and is now seeking funds and a manufacturer to commercialize it for single- and multi-family applications.

Improving hot water heating efficiency ... with cold water

Re: Improving hot water heating efficiency ... with cold water
 

A good way of putting aviable technology to use.

Re: Improving hot water heating efficiency ... with cold water
 

Too complicated.... just use this:

http://kenmaysplumbing.com/wp-conten...er-heater2.jpg

Re: Improving hot water heating efficiency ... with cold water
 

Not complicated at all, just a heat pump and a source of relative modest heat that you can excite. Usually a really energy effective way of creating heat for your house or to make warm water. Over here the incoming heat usually comes from geothermal heat or ground heat but I like this concept. I wonder what the energy consumption for that burner in your picture is compared to a regular heat pump.

Re: Improving hot water heating efficiency ... with cold water
 

Storage vs. Tankless Water Heaters | GreenBuildingAdvisor.com

Estimating Costs and Efficiency of Storage, Demand, and Heat Pump Water Heaters | Department of Energy

Re: Improving hot water heating efficiency ... with cold water
 

I was going to say. So how does this work.

Re: Improving hot water heating efficiency ... with cold water
 

The more i read on the subject the more I feel like a tankless water heater is good if you just need it for tap water, say in a cottage or cabin where you might want it for showering, dishwashing etc. I don't get the feeling hower that it would be cost effective if used to heat a whole house.

Re: Improving hot water heating efficiency ... with cold water
 

A tankless water heater is not a whole home heating system. This technology has been around for seemingly ever, and is still more mainstream in Europe than the USA. It is, however, much more efficient than having to keep a tank of water hot for some future use. It's also cheaper to maintain as you don't have to worry about a tank rusting out or your home flooding if the PRV fails or the drip pan clogs up. Installing a whole home water filter first will solve your concern. If you want a combo of the two, geothermal is likely the way to go. It is very expensive to install and certainly not cost effective when retrofitting a home. But it makes sense for new construction. I had one. It is eerily quiet. I did not get to enjoy it, sadly.

Re: Improving hot water heating efficiency ... with cold water
 

Modern NG tankless water heaters are very efficient . I know friends that use just one for whole home.