View Single Post
Old 03-22-10, 10:56 AM   #142
AC_Hacker
Supreme EcoRenovator
 
AC_Hacker's Avatar
 
Join Date: Mar 2009
Location: Portland, OR
Posts: 4,004
Thanks: 303
Thanked 723 Times in 534 Posts
Default Hacking Potential...

Quote:
Originally Posted by AirSepTech View Post
I would guess with improvments, marketing, and more Eco awareness, the inverter/ductless type of system could destroy the old FAU/duct systems long held ground. With R22 phase out, these new systems have a real chance, not just retrofit, new housing also.

Well, after we sell the ones that are empty.

I liked the fact they were HACKING. Made me think of this site.

The GSHP industry could be a lot farther along than it is.
AirSepTech,

Yeah, all good points...

What with the higher cost of energy in Asia, they have made great strides in efficiency. I sure do agree that we should be seeing more displacement of Forced Air (Scorched Air) units.

In fact, I think we should be seeing more radiant floor installations displacing FA. There are many comfort and efficiency benefits to radiant floors. From what I have read, radiant floors dominate new construction in Europe, by about the same margin as FA dominates new construction in the US.

So, getting back to hacking, before the advent of inverter technology (and other improvements) in air-source heat pumps, there was a goodly advantage in efficiency of GSHP over ASHP, even when both types of units were used to heat air. Some of the numbers I saw were like this:

ASHP = 2.2 COP
GSHP = 2.5 to 3.5 COP

The greater efficiency of GSHP was due to having a higher and more stable source temperature and also, because moving the heat via liquid was more efficient and used less energy than using air.

When comparing the efficiencies of ASHP heating air to GSHP heating radiant floor, the efficiencies looked like this:

ASHP = 2.3 COP
GSHP = 3.7 to 5 COP

This time the greater efficiency of the GSHP was due to higher source temp, the greater efficiency of moving the heat into the house via liquid, and also the very large area of radiant floors means that the temp of the working fluid does not have to be as high to achieve the same heat transfer, thus favoring efficiency.

So, in the meantime, mini-split engineers have improved the efficiency of their units by modulating the power used by the compressors to match the variable heat load requirements. The same idea is used to modulate the fan that drives air though the outdoor unit. and ditto the fan in the indoor unit.

So now, mini-splits ASHPs are exceeding, sometimes by a large margin, the efficiencies formerly found in early GSHPs.

To my knowledge, GSHPs haven't started applying the benefits of power modulation to their compressors and circulation pumps. However, I have seen that variable-rate radiant floor circulation pumps are coming available, not as integral to the GSHP industry, but as improvement to the radiant floor trade.

So, what this suggests for hacking, is that substantial advantages in efficiency might be obtained by successfully converting an inverter technology mini-split to a GSHP, feeding a radiant floor.

So I looked on ebay using this search term: mini-split inverter heat pump ...

I found some new, smaller inverter type units selling for about $500, the shipping would add about $150. Not chump change to be sure, but it does put good hacking material within the reach of many courageous hackers. I even checked out the COP of one of these units and the COP can be calculated by deviding the HSPF by 3.412...

COP = HSPF / 3.412

One cheap unit I looked at had a COP of 4.1

Compare that to early GSHPs and you can see the potential.

Best Regards,

-AC_Hacker

Last edited by AC_Hacker; 03-22-10 at 11:05 AM.. Reason: not finished posting
AC_Hacker is offline   Reply With Quote