[RE-wrenches] Off grid heat pumps

[Ray Walters]

I'd 2nd Hilton's comments.  Energy efficiency can reduce heating loads 
to almost nothing.  The German standard "passive solar" design uses 
almost R100 insulation, triple pane Lo E windows, doors with multiple 
seals, and are so tight they require an air to air heat exchanger to 
insure fresh air.  The occupants own body heat accounts for a large 
percentage of the heating, and small amounts of passive solar gain do 
the rest.
I've worked with a builder in Taos that is building to this standard, 
and it works.

2nd,  If that's too extreme for the customer, they can utilize an active 
solar thermal system that works in conjunction with floor heating.  With 
efficient pumps and closed loop design, pumps only run in the day when 
the sun is shinning anyway.
3rd, the old fashioned off grid method: air tight wood stove.  No 
electric load, and we have a lot of beetle kill firewood that is being 
turned into CO2 by decomposition already.  Might as well use it to heat 
your home.

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 2/4/2014 12:28 PM, Hilton Dier III wrote:
> I've done a couple of load profile studies for heat pumps and solar 
> and unless the load is primarily air conditioning it's a bad match. 
> Ground sourced heat pumps in general only pencil out if there is a big 
> air conditioning load.
>
> The only time I'd recommend a heat pump with an off grid system is if 
> there was a wind turbine that massively over-produced in the winter. 
> The PV production curve is exactly backwards.
>
> The clients should take half the money they would have spent on 
> installing a heat pump and do a thermal efficiency/passive solar 
> retrofit. Better ROI.
>
> Best,
>
> Hilton
> -- 
> Hilton Dier III
> Renewable Energy Design
> Partner, Solar Gain LLC
> 453 East Hill Rd.
> Middlesex, VT 05602
>
>
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