At what COP does any geothermal type become competitive with mod-cons in NY area?

D107

Just heard about this water-to-water heat pump and wondered, given our 26¢/kw actual cost of delivered electricity in our area and installation costs, if I should get my hopes up about someday having a single non-combustion source for my cooling and heating. (heat loss 40kbtu, cast iron rads.) I'd settle for just a heating system... http://residential.geocomfort.com/products/series/guide-wv-water-to-water

hot_rod

What other fuel source would you have to compare it to LP and NG. As you know LP can fluctuate quite a bit year to year, so it is tougher to pin down a number.

I'd look to IGSHA the ground source association for some number crunching.

The key will be very low temperature heat emitters. Siggy is running one on his office this winter up in Holland Patent, I'll be interested to hear his results with sub zero conditions.

I would like to get off the LP and wood burning ritual also. And with enough PV array I could offset some of the electrical costs.

pecmsg

Heres a fuel cost calculator.
https://coalpail.com/fuel-comparison-calculator-home-heating
Geo done right should run all the time. Where in NY The wells can be real expensive!

scrook_2

What's your natural gas total cost/Therm (or propane per gallon)?
Looks like at $2.00/Therm and 80% eff. vs. $0.26/kWh, you'd a need COP ~3.0, at 90%, a little higher.
Propane at $2.50/gal and 80% eff. COP ~2.2, at 90% COP ~2.5?
Than sound reasonable? As you can assume very low emitter temperatures, 90% eff is prob a better number than 80%

D107

Generally NG total cost is considered $1.50/therm, though last month with the severe cold it went down a bit. The unit featured in the link I put up at full load claims 3.0 COP. As I think about it I don't think WSHP would work with me; maybe ASHP. Not interested in ground source. Have had preliminary talks with a great installer about a condensing hwh for heating and DHW--I may not be in the position to wait for the ASHP technology to improve to the degree it would have to--although as Hot Rod points out, combining with solar may be the ticket for some.

mikeg2015

The killer is that in colder weather you’ll be running heat strips unless you massively oversized or have a crazy tight and well insulated house. Real world a COP is probably close to 2.5 for the season. The fancy inverter units are better, which I think you linked to. But installed cost is high as is replacement costs. You won’t get it back unless NG wasn’t an option. Comfort is better. They have more capacity at low temps.

Rich_49

Dave ,

There are 29.3 KWh needed to equal 1 therm of NG . That should make the math easier .

100,000 (therm) x .90 ( 90% ) = 90,000 BTUh

90,000 / 3414 ( BTUh per KWh ) = 26.3

.26 x 26.3 = 6.83 / Cop of 3 = 2.27

Break even point would require a CoP of 4.55 . That's assuming a low end efficiency of 90% , you should be higher than that on average .

VBHs are quite an expensive ordeal and it must be designed correctly and you'd have to watch the drillers like a hawk since many of them ignore the depths they've been instructed to drill . They use pipe smaller than they've been instructed to use to save a few dollars , this raises the head and you'll use more pump energy to move the fluid through . Also remember that CoP is just for the machine , the pump/s use a masive amount of energy that everyone conveniently leaves out , either that or they don't know .

Leonard

Other issue to consider is if you have frequent power outages and need generator power to make heat. Then with heat pumps you may need a higher kw rated gen to start the pump. Larger gens have proportionately larger baseline no-load fuel consumption. Fuel costs over a long outage (week) are not insignificant.

SuperJ

mikeg2015 said:

The killer is that in colder weather you’ll be running heat strips unless you massively oversized or have a crazy tight and well insulated house. Real world a COP is probably close to 2.5 for the season.

This isn't quite true, there are different sizing programs but generally it makes sense to size for a certain percent of your heat loss, and make up the deficit with heat strips. If you size for 100% of the heat load you are putting a lot of extra loop in the ground to only cover a percent or two of the run time making it cost prohibitive.

But sizing to 75%(just an example) covers way, way more than 75% of your run hours (probably over 95%). My parents have a heat pump installed this way (installed in 1996), and he's had the breaker off to the heat strips for 15years and never had the house drop below 72f.
His heat pump is sized to put out about 40,000 but his heat loss calc came in closer to 60,000.

Real world COP (including pumps/fans) with half decent equipment (think Climate Master or Water Furnace) should be between 3.0 - 4.0+, and can exceed 5.0 with low temp infloor applications. Even with our cold ground up here in Canada.

I agree that pumping is probably the most often thing that gets screwed up with GSHPs (especially commercially), I used to work in the GSHP industry and we always did our COP calcs including pump power. But, when correctly sized, the pumps do not use a "massive" amount of energy. With a properly designed loop/pump combo the pumps were only only a decimal point or two on the COP (usually one or two grundfos 26-99s, loop sized to flow 3gpm per ton). Dealers often want to upsize to bigger pumps or use 2/3 when one would do because of the more or bigger is better mentality.

I agree, it's hard to start a big compressor on a small generator.
And, I agree VBHs are expensive (another reason to size equipment and the loop field intelligently). That's the main reason you don't size a heat pump like a boiler (you work down from the heat loss using annual performance modelling software, not up).

If your heatpump is not running 100% of the time on the coldest nights then it's likely oversized (at least financially) IMHO. Incrementally it's expensive to add loop that isn't necessary especially vertically. Burning fossil fuel there is no financial barrier to oversizing way past your heat load, just a slightly bigger burner and you only pay for fuel you burn.

hot_rod

I agree that pumping is probably the most often thing that gets screwed up with GSHPs (especially commercially), I used to work in the GSHP industry and we always did our COP calcs including pump power. But, when correctly sized, the pumps do not use a "massive" amount of energy. With a properly designed loop/pump combo the pumps were only only a decimal point or two on the COP (usually one or two grundfos 26-99s, loop sized to flow 3gpm per ton). Dealers often want to upsize to bigger pumps or use 2/3 when one would do because of the more or bigger is better mentality.

Looks like more and more ECMs in GEO versions, that should cut pumping power in half or more. And maybe some could communicate to the HP.

Rich_49

mikeg2015 said:

The killer is that in colder weather you’ll be running heat strips unless you massively oversized or have a crazy tight and well insulated house. Real world a COP is probably close to 2.5 for the season. The fancy inverter units are better, which I think you linked to. But installed cost is high as is replacement costs. You won’t get it back unless NG wasn’t an option. Comfort is better. They have more capacity at low temps.

Mike , Please stay on point with these discussions . We are discussing a water / water HP . Heat strips are not applicable , they only have a place in a ducted application , this is a hydronic application