Quote:
Originally Posted by S-F
He said he could convert a minisplit to geothermal for me but I don't need to bother since the new ASHP's are going to eviscerate the geothermal market.
|
He may be a genius, but I think he's been to too many sales presentations...
One of the biggest determiners of vapor-compression efficiency is the delta-T between the source temperature (ground temp or air temp) and the sink temperature (inside temp of house)... a lot of people refer to this as 'lift' or 'temperature lift'.
I came across
a very interesting British study that compared ASHP and GSHP COP from various manufacturers (in the UK). Here are some relevant charts from that study:
It is a true marvel how much mini-split efficiency has improved, and I for one am enjoying that improvement. But all of the incremental efficiency improvements that are going into mini-splits can be equally applied to GSHPs.
In the end, GSHPs will always have the advantage of lower 'lift'.
If exceedingly good insulation practices were fiendishly followed, I can see that the onerous cost of earthwork could be reduced to the point where the cost of earthwork would become quite modest.
There's also the advantage that sheltering the compression equipment inside the house makes it last much longer.
Inverter technology is about to burst upon the scene of whole house ASHP units. I have already seen the sales literature. I have also seen reports from the UK of inverter technology being available to the GSHP installers there.
It is pretty standard already for whole house ASHPs to have ECM fans, but the real efficiency will come from ECM compressors (inverter tech).
BTW, I came across some really great "webinars" about GSHPs and radiant floors. I'll be posting links in a couple of days.
One of the things I did find out from the webinar is that the understanding that we generally display on this blog is
actually ahead of the cutting edge of the industry... something to be proud of.
-AC_Hacker