[Greenbuilding] DHW COP

[nick pine]

Paul Eldridge <paul.eldridge at ns.sympatico.ca> writes:

> I installed our new Nyle Geyser heat pump water heater earlier today 
> (http://www.nyle.com/water-heating/geyser-r/)

Hmm... "the GEYSER® is an add-on unit that can be added to any existing 
storage tank water heater. The GEYSER® will save you an average of 50%-65% 
over the operating costs of an electric tank water heater... for every unit 
of electricity used, the GEYSER® produces over two units of heat for making 
hot water."

> I'm pleased to report that the results are even better than I had 
> anticipated.  It took 1.64 kWh to bring 115 litres of water from 16.7?C to 
> 49?C... All in all, not too shabby given that it would have taken 4.3 kWh 
> to do the same job using electric resistance.

115Lx1000g/L(49-16.7)4.186J/g-K = 15,548,897 Joules, ie 15,548,897/3600 = 
4.319 kWh, with a COP of 4.319/1.64 = 2.63. I guess that saves 
100(1-1.64/4.319) = 62%. Nice...

> I've plugged ours into a simple mechanical timer that has a twenty-four 
> push-pull pin wheel, so it's not scheduled to come back on until 06h00, at 
> which point it's free to run for up to two hours before the timer kills 
> the power again; if need be, we'll add a second cycle for the evening, but 
> I expect that once per day will suffice.

Last time I checked, a 4-watt mechanical timer would use more daily energy 
than than the heat loss from a well-insulated electric resistance (vs heat 
pump) tank running 24/7.

I estimated a 1.6 COP for a dehumidifier with a measuring cup and a 
Kill-A-Watt meter. What's the COP of a fridge or freezer? We might cool 50 1 
liter water bottles from 70 to 10 F with a freezer and measure the 
electrical energy consumption. If that's promising,  we might heat DHW by 
running a little outdoor air through the freezer.

Nick