New Geothermal Heat Pump

Archer; no. where do you come up with 3 or 4 times ? perry

Actually, yes.

Electricity can be generated in excess of the amount required to pump heat transfer fluid to the surface. There are geothermal plants that generate elctricity in operation today. Though currently not as cheap in dollar per watt terms as many other alternative energy sources, it is very steady.

Overunity is not occuring though. A heat source is being utilized. None of the laws of thermodynamics are violated, and Nessie, Bigfoot, or Mescalito are unlikely to be designated plant operator.....ruling out overunity.

Benbenben

I think this might warrant some number crunching and research on your part. The idea is not completely implausible. If you were asking "Would it be possible to use a heat source (such as a fire) to cause a phase change (boil water) and power a turbine, while supplying only a small amount of electricity to run a recirculating pump, I think we'd all say yes.

However, an air conditioning compressor is not just a recirculating pump. It is doing a relatively large amount of work to compress a gas. And of course cool-to-warmish ground is not supplying a lot of heat energy.

For ordinary geothermal power, the temperatures must be quite high for the plant to be profitable. This leads to drilling very deep, and in turn means that there are few small geothermal electrical generating systems.

If a heat pump which transfers 400 watts of heat energy for 100 watts of electrical input runs a 25% efficient Stirling engine, which runs a 90% efficient generator, then you have not reached break even, and would have been better off just heating (or running a motor, etc) with the original electricity. With a low grade heat source, I don't know that a Stirling engine would operate at even 25% efficiency. But I'm just guessing. I think it would be worth figuring out the various efficiencies.

I am not at all sure my logic is correct here. The situation could be worse than I think.

You may want to play around with the small Stirling demo engines that will run from just the heat of your hand. You might also sketch up a system and post it to see what people think.

Here is something to look at.

You are thinking of the coefficient of performance or cop. It is true for a typical heat pump if it is inside the building for one unit of electrical energy you will get around three or four units of heat which inludes the heat produced by running the pump. It is not free energy, it is not electrical energy it is heat energy. It is very good value but requires a higher financial investment than simply burning a fuel for heat. If you want to be clever buy natural gas at your door, drive an internal combustion with it and recover the heat, and use the mechanical output to drive a heat pump and an alternator then sell any excess electricity into the grid or use it (you have just uprated the energy of gas into a more valuable commodity) and bask in the waste heat of your machine and that of the heat you have pumped from the ground.

I like this sort of idea, and feel that it should be much more widely implemented than it is. Honda makes a nice home cogenerating unit for this purpose (although it generates only electricity and heat, without running a heat pump compressor) and they claim an overall efficiency of 85%.

An appealing part of such a process is that (provided you can make use of the "waste" heat -- which in many areas is pretty easy to do) then the efficiency of the actual engine -- and even the generator, if it is water cooled too -- can be low (so the engine can be cheap) but the overall system efficiency can still be very high.

This whole thing's come up from confusing 'coefficient of performance' with 'energy used'.

A heat pump's coefficient of performance is the ratio between the energy is pumps from a heat source/reservoir to somewhere else and the quantity of energy used to drive the pump.

Thus, if a heat pump draws 10 KW of power to 'pump' 30 KW of ground heat into a house (or whatever), its coefficient of performance = 30/10 = 3.

In their normal operating range, most heat pumps have coefficients of 3.0 - 3.6.

Heat pumps provide more heat than resistive heaters such as baseboard heaters. The latter have a coefficent of one ... each KW of electricity that goes into the baseboard heater gets transformed to one KW of heat. Thus, since heat pumps provide more heat than the energy put into them, they're more performant than electric baseboards (provided that the heat source is warm enough) ... and that's why electric utilities encourage people to heattheir homes with heat pumps rather than electric baseboard heaters.

Cheers! DZ

The average outside temperature will make or break overall efficiency calc's

it 54 degrees all year 4 feet down

arche

Underground temperature for a given location is either known or easily determined. İt is not universally 10 deg C (50 deg F) as is commonly thought. The problems with the GSHP (ground source heat pump) are the cost of the loop required to collect the heat from or distribute the heat to the ground.

Hello The cost of the collector loop is not the issue - here in Germany it is just the equivalent of around 1000 gal of heating oil I need now to burn during one winter season in the 25 year house I live in by now. The heatpump cost is an equivalent of 3000 gal of oil or around twice the cost of an efficient natural gas burning heating boiler. The COP for a modern heat pump is now improved to 4 to 4.6.

To utilize this you need a floor heating system in your house, as the temperatures you can get with the heat pump are too low for radiator based heating systems and you need lots of isolation in your house. Even a woodframe based exterior wall is around 1 to 1.5 (or even 2!) feet thick. That is where the real cost are! But looking forward to move to the new house.

Again 'out here in Montreal, Canada', heat pumps are pretty common, but GSHP systems are pretty rare. The heat pumps we use for homes exchange heat with ambient air, which is nowhere near as good as exchanging with a ground source. That being said, the pump-to/from-air systems are much less expensive than GSHPs. The downside is that below 12 C, our heat pumps become ineffective, so we then have to run on baseboard or in-duct heaters

As concerns radiant floors ... they are becoming better known, here but they're still fairly rare. Central air-heating is the way heat pumps are principally used here.

Cheers!
DZ

With a direct exchange ground source hp its pulling from 54 Deg. all the time.

(DX system)

Out here in Montreal, Canada (45 degrees north, continental weather), the temperature three metres down is about 8 C year-round.

As concerns the cost of the loop ... have a look at this system, which a firm two hours from Montreal manufactures.

In English: www.technometalpostusa.com

In French: www.technopieux.com

Instead of drilling holes and sinking deep shafts and pipe for fluid flow, all you need to do is to get a small excavator to dig two-metre (six-foot) deep trenches. Then, a special machine 'screws' in pre-manufactured metal posts whose points reach around 607 metres (around 20 feet). All that's left to do is to connect thermoplastic piping for underground service, add a fluid pump, connect the whole to a heat pump, and the system is ready.

All of this greatly reduces the cost of setting up a GSHP system. For a single home here in Canada, a 'classic' system costs around $25,000 Canadian (so around the same in US dollars these days), whereas the new system costs around $5,000. Yow!

Cheers! DZ

That sounds good.

I installed my geothermal with a horizontal loop in 2001. I used 1Km of pipe buries 2m deep.

The temperature of the ground near the loop does change through the year. At the end of the heating season, it is just a 2-3 degrees C above freezing. While it rises to about 15C in the summer once I dumped enough heat back in the ground. Of course if I had 2 Km of loop and a larger lot, the temperature variation would be lower and the efficiency of the heat-pump would increase.

I have been very happy with this system up to now. My energy cost is about $1700 per year for a 2000sq ft, two floors home with basement. (I spend more on phone, TV, and internet connection!). I have a heated pool in the summer from the AC heat. I also have two teenagers taking long showers with water partially heated by the heat-pump.

How does this compare with other home owners? Did I make the right choice?

Hello:

To date: harrisburg PA

2700 sq ft/ over 3/4 basement:

Single man

Radiant basement, when wanted: Chose oversized "6ton" dual compressor 3-staging for all Domestic HW production and Radiant and Forced air, in all ductboard system (!) but kept under 700 ft per min as that was his spec to use duct board...

BUDGET since 2007 has not exceeded 97/mo to date. - EVERYTHING ON THE PROPERTY, with a nice glass area overlooking a golf course and woods.

~

5500 sq ft liv area/ rec basement is radiant, 8 ton GTHP (dual compressor 3 staging 3 & 5t) with both dual Priorities of 100% instant HW and Radiant heating as Hydro-Temp does it with out additional Wtr:wtr units...

Entire fam of 6, total billing, under $220/ mo budget, 2013

~

3200-3400 sq ft 6" cellulose homes and r(50) attics, uninsulated basements (kept cool)

52f ground zone 6 6600-6700 deg day average coldest winters,

@ $ under $135.oo / mo budget all HW in heat recovery in cooling and by GTHP 100% On-Demand Priority

These homes are heating under 12 btuh/ sq ft , forced air with all high return airs, as similar to n-Ohio has little cooling demands, and that cuts the humidity causing a little longer cooling runs.

~

Now VFD 4.1/2 ton in 3000 sq ft has not had a $200 bill since NOV 2013, but that is open well 52f water. ~ 6gpm, lift under 70ft from dynamic well level.- ALso instant HW and will be Heat-Reclaim HW in the summer, the well is shut off, at those heat-recoveries.

yes and i know how at $2.50/ foot

Had an engery audit done last fall, 5+ air changes per hour (yea it leaks like seive) in a 1500 sq. ft. 1960's side split in Mississauga, On. Gas heat with an older Claire Mega Save II (I called it Mega Spend for years but fixed that.)

My gas bill is $1200-1300 per year and includes a Gas 40 gal hot water heater.

How much for electricity on top of the heating? Do you have AC in the summer?

Thank you.

Marco

Yes we have AC and except for last year (worst summer i've ever seen) run it about 4-6 weeks of the year. Also have an inground 16 x38 pool with the required 3/4 HP pool pump (on a 8 hour "on" time timer per day) No pool heater but have been working on building a wood boiler to heat the pool (Still in drawing stage!) Electric bill is about $1,000 -1,200 per year maybe less.

I went from 1200 gal of propane at $1.85 /gal to $360 /year on a air to air HP. I started at $.35/gal. in 1975 and finale converted in 2002. The cost to convert is the killer. I did the conversion my self ad saved about $3000. The secret is sweat equity. rent a small drill rig, your only drilling 50 feet per hole, and install your HP yourself. I had to farm out the sheet metal work and the r-22 and final installation (no license for HVAC) Google geothermal HP's

Archer

Total heat pumped by a heat pump (such as an AC) can be three times the energy used by the compressor, as we are only moving heat from a lower to a higher temperature and not creating heat. An immersion heater on the other hand produces an exact equivalent of heat to the consumed energy. Is this what you are looking for?

Your moving 4 times the heat at 1/4th the cost. Electric rester heat is 1 to 1 and costs 4 time as much.

Right you are. That is the advantage of a heat pump.