[Greenbuilding] Heat pump HWS

[Nick Pyner]

Hi Bob

There is nothing particularly detailed about my figures and there is not 
much in the way of calculation! It is all simply an extension of about 
fifteen years of work with grey water heat exchangers. I have a standard 
Rheem electric storage heater with its own exclusive kWh and water 
meters. The heat exchanger works with a Maddalena heat meter which gives 
a daily output in kWh and total water flow. The testing arrangement is 
not ideal but I do know _exactly_ what is going on!

I think it is a big mistake to try to plan for "just enough panels" for 
your HWS. You are bound to get it wrong, and your wife will be far from 
impressed.

The reason why I am looking at 3kW of panels is because that is all that 
will fit in a single group on a north-facing roof. That's real planning 
for you - architecture and environment, not numbers.

The 3kW means I only need about 1.5 hrs of peak power equivalent, so I 
can be reasonably confident of getting that regularly, particularly as 
the roof is pretty ideally pitched at 45 degrees. It was actually built 
to take a (gasp!) solar thermal HWS, but that never happened. For all 
that, I don't think the HWS is so important since, if it was not on 
solar, it would be getting power off-peak after 10pm. Far more important 
is the stuff that has unavoidable daytime demand - the fridge, the 
stove, and winter space heating.  If you want to do some serious 
planning, that is the place to look. All I have done there is confirm 
that the energy label on the back of the fridge was correct on an annual 
basis, and all that really meant was that getting a new one is not such 
a high priority.  Your power bills should tell you all you need to know.

Nick Pyner

Dee Why Beach   NSW





On 23/04/2016 11:48 PM, Jake jakaitis wrote:
>
> Helpful to understand how you arrived at these numbers?
>
> I am interested in starting out my PV system with just enough panels 
> to power my new energy efficient whirlpool hot water tank. T
>

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