[stevehull]

Pete

Great idea but the numbers simply won't support it. Here is why . . .

First, the specific heat of water is ~ 1000 times that of air. By removing a small amount of temperature from air, it will minimally heat up water.

In other words you can heat up a given mass of water by 1 degree, but you have to move 1 degree of heat from 1000 times that mass of air. The volume of air in a fridge is small and increasingly constrained from temperature changes by better and better insulation.

The ability of a home 'fridge to overheat almost any amount of water to boiling over a weekend is numerically impossible. Well, perhaps an ounce - maybe not even that.

Your points are well taken, the kitchen operated, food preservation heat pump does always give off heat and in the summer it does contribute to the homes heat load. That said, most desktop computers and the monitor give off even more heat!

The difference between heat and temperature is not intuitive. I did not truly understand the concept of specific heat until I literally felt the input and exit water lines from a water to air geothermal heat pump. The temperature difference across the water pipes was maybe 5 degrees F, but the unit was blowing out 120F hot air. The rise in air temp was some 50 degrees F with a hardly perceptible decrease in output water temp. That was a HUGE "a ha" moment where the specific heat of air vs water finally sank in.

Capturing heat requires a substantial amount of "stuff". And the cost of that equipment is not trivial. But in applications where you can move a lot of heat, like a geothermal heat pump, you can heat/cool the house with it. I know, as I do it.

My perspective is that using the home fridge to heat water is not a practical solution on a mass scale. Fun to do, great to play with intellectually, but difficult to put into widespread production.

But I REALLY like the idea . . . .


Steve