New geothermal going in around the block!

[EatenByLimestone]

I drove down the street today and was surprised to see a well drilling rig pulled next to the house. We're on town water. Written down the side in large carnival like letters was Geothermal. Well, that explains it. Drilling a well to do it is a pricy way to get geothermal!

 

[begreen]

If you have limited real estate it may be a good option. Personally though, I'm not in favor of extra holes into the aquifer. Each one presents an opportunity for contamination.

 

[maple1]

I think operating costs might be more as well?

 

[semipro]

I think operating costs might be more as well?

It depends on the system type: open loop or closed loop.
In a system like our open loop ground source we lose efficiency due to the pumping energy lost when water is returned to the standard well that it came from -also our drinking water supply. The returned water falls openly within the well so potential energy is lost there.
In a closed loop system where the heat transfer liquid is pumped down a u-shaped pipe within the well or borehole you don't get those losses.
Both types have friction losses as the liquid is pumped through piping but those are based on the length/size of pipe which should be similar between the two system types.
BTW, most ground source heat pump wells are just a borehole where the u-shaped piping is placed and then the borehole is filled with bentonite clay or some other material.

 

[peakbagger]

I have been looking into geothermal for 15 plus years for a future house or possibly my existing house. Its hard to get info on small systems as the folks at the shows are trying to sell high end HVAC solutions for high end homes or subsidized public projects. The HVAC concepts are air based systems and I have no interest in ductwork as it takes up interior space in order to be efficient. Nevertheless I have studied up a bit on the ground source side of the technology and hoped that water based systems were coming. The fundamental problem with ground source systems available today is they are good at making warm air or water but not so good at making hot. They can be tweaked for higher output temps but the COP drops down big time. With the air based systems, the goal is to run the fans 24/7 and keep the temps steady in the house (no set back theromostats) although outdoor reset seems to be okay so warm air is good enough. Many of the system have some backup resistance coils hidden away in the ductwork. They are complex systems and being in rural area the service techs tend to have to drive up a couple of hours from the city so service calls and ongoing yearly maintenance is an issue.

For the last year or so John Seigenthaler has been pushing ground source and air source units that put out warm water instead of air. He is a big fan of the European move to low source temperature radiant for wood systems which allows an overall increase in efficiency of systems and also stretches storage capacity significantly. His goal is supply temps down in the sub 100 F range preferably lower down to the mid eighties. This works well for new construction or very tight older homes that have been upgraded with properly designed radiant panel radiators, radiant walls and radiant ceilings and possibly properly constructed radiant slabs. He has a recent article in this months PME that improperly built radiant may not be a good fit https://www.pmengineer.com/articles...-explicit-on-tubing-depth-in-a-slab?v=preview. He claims that both air source to water "minisplits" and geothermal to water heat pumps are coming to market but I haven't seen any residential units on the air side. One of the roles I do in my job is review energy efficient commercial building projects and I have recently seen large multistory apartments that will be heated with geothermal variable refrigerant flow (VRF) systems that are effectively what a multihead minisplits are. The VRF head units ultimately end up in air handlers but I expect its just a better fit for the buildings as they are in somewhat warmer climate (Mass) and are more air conditioning dependent. John's contention is that in areas with lower cooling demand compared to heating that a few air to water terminal units fed from a heat pump are the better approach for cooling compared to running ducts for moving hot air around in the winter as in his opinion radiant heat is superior to hot air.

So it looks like ground to water or outdoor air to water is coming and can be integrated with new construction if its set up with low temperature radiant emitters but it comes down to going to the extra big expense to putting in a ground loop or borehole compared to going with an air source unit and have wood or other backup for supplemental heat during really cold conditions. I expect I will be able to buy several air source units compared to the labor and material for either a trenched or drilled ground source. The conductivity of the soil or rock and the presence of ground water makes a big difference in ground loop design. The drilled systems for my area is about 300 feet for every ton (12000 btu/hr) of heating or cooling. The ground loop is fusion welded HDPE loop with 180 return bend welded onto it that is slipped down the hole and then grouted in with high conductivity grout. The grout is intended to increase conductivity and also act as secondary containment for the glycol solution used in the loop so groundwater contamination is less of an issue. The horizontal trench method is less popular in my area as the soil is quite boney and the ground temps lower. Most systems go relatively shallow due to trench depth issues as having to put in trench protection during construction really slows things down. Some folks argue that trench system are more of a very slow thermal battery versus a permanent fixed temp. During the winter the heat is pulled out of the ground and actually depletes the source lowering the ground temp. Before it becomes an issue, its summertime and the lowered ground temp is appreciated although eventually it heats up hopefully in time for summer to be over. I have heard widely variable lengths of horizontal runs but two loops of 500 feet in a 6' wide trench foot seems to be a ballpark for one ton of heating or cooling in well drained soil. That's a lot of diesel and tubing getting buried so expect that's why drilled geothermal is popular. Its still energy intensive in my area due to shallow granite. I see a recent install where they drilled multiple wells in a large field, my guess is they drill through glacial till until the hit bedrock and then move to the next spot, more holes but lower cost. I think there is also a way in some soils to slide the loop down the hole and grout it in place without a permanent casing.

My estimation is unless I have a spare dry borehole sitting around (its not unusual for some wells in my area to be drilled 900 feet into granite and never meet FHA minimum flow. My well is 320 feet and its on the low end so spare very expensive dry holes are not uncommon), the way to go is Pretty Good House energy efficient design with low temp radiant emitters and one or two air to water units feeding a storage tank with small wood boiler attached to it for cold weather and crappy solar generation. I would then get a couple of air handlers for cooling and integrate them in a closet somewhere. My goal would be to get down to no more than 2 tons of heat pumps to cover 95% of the year and use wood or some other backup for the 5%.

 

[begreen]

webfish has geothermal in his home.

 

[MTY]

I am still having difficulty getting a bid on a system. Both companies that came out said 3.5 ton. The last person to come out was the most experienced. He has 220+ installs under his belt. He wanted 800' of slinky per ton. I believe he is actually working on the bid. It has been about 10 days since he was here.

The first guy was here about 2 months ago, did not seem to have much idea of what he was up to and said 300 feet of straight pipe per ton.
I'll dig the ditches, and from what I have read I have the most desireable type of soil. It is 3' of topsoil over clay. Supposedly the clay retains enough moisture in the dug portion to facilitate the transfer of heat both ways.

I know more about this than I ever wanted to, and I still know next to nothing.

 

[DBoon]

I put in a three ton ground-sourced heat pump in a renovation. The calculated heat loss at 0 degrees F is 18,500 BTUs/hour. Total heat loss for the winter is about 55 MBTU. I have two vertical wells each 250 feet deep. The system heats a large water storage tank and has an outdoor reset for control of tank temperature. Design temperature for supply water is 120 degrees F at 0 degrees outside temperature. I recall at about 40 degrees supply water temperature (design) is about 100 degrees F. I have good water flow around the vertical wells (I knew a little about the underlying soil hydrology from my father-in-law) - the contractor agreed that 500 feet of wells would be fine for my heating needs - 18,500 BTU/hour heating loss is pretty ridiculously low, after all, for an old house renovation that is not "passive house" (but a pretty good house, as someone said).

The hot water is supplied to 9 total 1/2" PEX radiant loops, each between 250 and 300 feet long. The PEX is housed in thick aluminum plates affixed to the bottom of the wood floors. The circulation is through a single Grundfos Alpha pump that uses about 20 watts with all zones open.

The system worked great last year despite the absence of insulation over the PEX and plates. I've fiddled with the outdoor reset control to reduce the supply water temperature, and am now insulating the PEX and plates, and I expect it will work better this year. I'm looking forward to finishing the renovation and moving into the house full-time in about a year. If I ran it full time, I expect it will consume 3-4 MWhr/year. I'm adding to my solar PV system to accommodate this demand, and the demand from my electric car.

There are more details about the system in this thread
https://forum.heatinghelp.com/discu...me-feedback-on-my-radiant-design-plans#latest

 

[David.Ervin]

I've got geothermal at my house, installed with horizontal bores rather than vertical wells or open trenches, and I couldn't be happier with it. It's a 5 ton system, and I've got 5 lines about 10 feet underground spaced 20 feet apart, mostly under the driveway and out into the front yard. Not sure about the 300' per ton figure mentioned previously, but I think that would square with the total lengths I'm working with. The unit has a domestic hot water co-generation capability that when cooling the house will shed excess heat into the hot water tank first before going out to the ground loop. I can't verify this has made much of a difference in the electric bill, but I suppose something is better than nothing.

We're in a rural area, so everybody has big propane tanks and noisy A/C compressor units outside. It's nice to not see or hear anything but the great outdoors, and I can pretty much make it snow in my living room if I really wanted to.

 

[Ashful]

I’m the only house in my entire neighborhood without geothermal, and at least here, they are all deep well systems. Of course, I’m the only one who bothers to burn wood. Houses are 6000 - 12,000 sq.ft. on larger lots, and all owner-built, so the opportunity for recouping costs long-term favors the higher install cost. Most were installed mid-1990’s, but one new house was built last year and another had their system replaced, and both still went deep well.

 

[sloeffle]

Not sure about the 300' per ton figure mentioned previously, but I think that would square with the total lengths I'm working with.

We put in 600' of pipe per ton for our system. IMHO - I'd rather have too much than too little.

 

[maple1]

I am quite curious on how much electricity those with geo are actually using. Along with type of ground system, heatload, etc..

I've gotten mixed messages from those here I ask. The one guy who threw some actual numbers at me had some pretty scary numbers. He has loops in trenches.

 

[David.Ervin]

I am quite curious on how much electricity those with geo are actually using.

The thermostat displays how much energy its using at the current instant, broken down by fan, pump, compressor, and aux heat if it's on. In cooling mode, the highest I've seen this get is a total of ~2800 watts. There's also displays for the total today, this week, and a month by month bar graph. I think I'll average 4 hours runtime on a hot day. Heat is pretty close to that too, but I'm running wood stoves in the winter so the geothermal doesn't run a lot. When the electric heat kicks on (i.e. it's 65 in the house and you set it on 75), it'll jump up to ~10,000 watts. If you're curious, I can take a picture or something when I get home.

What would constitute "scary" numbers?

 

[maple1]

The thermostat displays how much energy its using at the current instant, broken down by fan, pump, compressor, and aux heat if it's on. In cooling mode, the highest I've seen this get is a total of ~2800 watts. There's also displays for the total today, this week, and a month by month bar graph. I think I'll average 4 hours runtime on a hot day. Heat is pretty close to that too, but I'm running wood stoves in the winter so the geothermal doesn't run a lot. When the electric heat kicks on (i.e. it's 65 in the house and you set it on 75), it'll jump up to ~10,000 watts. If you're curious, I can take a picture or something when I get home.

What would constitute "scary" numbers?

$900/month.

 

[Z33]

2800 watts seems high for what's supposed to be an Uber efficient system.

That's the same wattage my 14 seer 3 ton heat pump and air handler use according to my solar edge meter.

 

[begreen]

2800 watts seems high for what's supposed to be an Uber efficient system.

That's the same wattage my 14 seer 3 ton heat pump and air handler use according to my solar edge meter.

At 5 tons, his system is 66% (2 tons) larger. And it's not running 24/7, just a few hours a day.

 

[peakbagger]

Be real careful making comparisons. About the only way to do it is do detailed heat loss calculation for two comparable structures and then see what the actual difference in cost to heat is.

Before I went to University of Maine one of the professors had his field of "outhouses" they were identical 4'by 4' by 8' structures built of different construction type and materials including a couple of log cabin designs. I think they had a standard door on one side. Each had the same sun exposure with shading taken into account. The instrumentation was line voltage thermostat and 100 watt lightbulb for heat and power meter. They let the outhouses sit over the course of year and came up with actual heat load calculations. At the time log cabins were being pushed as superior to conventional framing due to high mass of walls. This is pre internet days so I have never found a report on it but if I remember the log cabins did not fare well. I expect to make a good comparison of heat source types including geothermal a similar methods would be the best approach.

 

[David.Ervin]

It's impossible to tell you what would constitute "good" or "scary" energy usage; too many variables from each situation. My house is pretty well insulated being only 5 years old, and it's in central ohio so winters get cold and summers get hot. I've never seen an electric bill over $275 / month, and that includes the hot water tank, well pump, and literally everything else you can imagine in the house. Also, your mileage will vary with the price of electricity in your area.

About the only way to do it is do detailed heat loss calculation for two comparable structures and then see what the actual difference in cost to heat is.

Bingo. Is this going in a 1960s home with balloon framing and foil "insulation" in the walls next to original windows, or a 2010s energy conscious home built to modern codes with R40 in the ceilings and 2x6 exterior walls full of spray foam?

 

[sloeffle]

@maple1 I posted this awhile ago on another thread

Where are you?
North Central Ohio ( climate zone 2 )

-How much space are you heating and how is it distributed (radiant, forced air, etc)?
Roughly 3,000sq ft via forced air

-DHW too?
Indirectly via HPHW

-What’s your heat source
Geothermal and PSG Caddy Wood Furnace. Run the wood furnace when temps are generally below freezing.

Geothermal Cost below:

May 2018 - $7.46
June 2018 - $9.64
July 2018 - $18.86
August 2018 - $24.43
September 2018 - $16.25
October 2018 - $39.75
November 2018 - $66.59
December 2018 - $54.12
January 2019 - $38.88
February 2019 - $13.89

Grand Total for the heating season so far ( October to present ) = $213.23 plus free hot water

Grand Total for last years cooling season ( June - September ) = $69.18 plus free hot water.

How much wood have you burned and what kind:
1.6 cords of mostly marginal Ash firewood.

-Normal year for you?
1.5 - 2.5 cords

If you need up to date numbers, please let me know. I just need to pull them off of the efergy.

 

[Rhone]

I've not seen a good apples-apples comparison between geothermal and say natural gas or oil. Think this through from start to finish, power plants are around 35% efficient converting fuel into electricity, then there's an 8-15% loss delivering the electricity so the electricity coming into your house is around 30% efficient. If you plugged in an electric heater at 100% efficiency means you're using 100% of the 30% efficient energy coming into your house so you have 30% total efficiency (you have to pay for 100% of the fuel they burned at the plant though). Then electricity has the highest charges for taxes, delivery, maintenance, research, etc. Why people who switch to electricity because it's 100% efficient get a wake-up call when their heating bill increases 350%+. I also read an interesting article geothermal is not as efficient at heating than cooling so if used mostly for heating one should not expect the rated efficiency.

I read...
1kWh of electricity produces 3,412 btu's and costs me $0.32/kWh so to produce 118,150 btu's costs me $11.08 in electricity.
1 gallon of heating oil has 139,000 btu's through an 0.85% oil boiler = 118,150 btu's as well but oil is $2.55/gallon
Natural gas costs about $1 through a 95% efficient boiler where I live to produce the same 118,150 btu's.

***Of Note in winter my electricity is $0.15/kWh + $0.145 per kWh delivery & other fees + $10 flat fee per bill which works out to $0.32/kWh.

So to produce the same btu's where I live electricity costs 423% more than oil and 1086% more than natural gas. Geothermal is typically 300-400% efficient (but as mentioned earlier apparently not when used for heating), there's not enough geothermal efficiency to offset electricity costing 423% - 1086% more per btu. The price when I was quoted for geothermal was $36,000, a high efficient oil boiler $7,500, and natural gas $10,500. It's not cheap either.

Just something to ponder, it doesn't make sense where I live if looking at savings. But, if you live in a more cooling dominated climate, with cheap electricity (preferably made by renewable resources) then possibly. It does have the benefit you can put PV panels on your house and become self sufficient my friends did that. Their PV panels make more electricity than the electricity + geothermal they use for the year and haven't paid a utility bill in some years (probably cost them over $60,000 though!) but they are living green and paying nothing for utilities but we don't know their future. Power companies are really into doing tricky things now making it harder if not impossible for solar people to not pay in some form or another (by having their credits expire, or charging a $/kWh used regardless of solar or not).

 

[begreen]

Right. Your electricity is really expensive. As noted, heat pumps have greater efficiency than resistance electric heating. Geothermal systems have a COP of 3-4.5 meaning a good unit is going to be 400% more efficient than resistance electric heat. Works out well for our milder climate and better electric rates of about $0.11/kWh. Even air to air heat pumps make good cents here. We have no natural gas available and oil is up around $3.50/gal. delivered. Propane is just as bad.

 

[Ashful]

Even air to air heat pumps make good cents here.

Don’t think your pun went unnoticed, intentional or not!

 

[begreen]

 

[sloeffle]

***Of Note in winter my electricity is $0.15/kWh + $0.145 per kWh delivery & other fees + $10 flat fee per bill which works out to $0.32/kWh.

If I was paying that much for electric, the roof of my house would be covered in solar panels. Are you in Hawaii ?

Why people who switch to electricity because it's 100% efficient get a wake-up call when their heating bill increases 350%+. I also read an interesting article geothermal is not as efficient at heating than cooling so if used mostly for heating one should not expect the rated efficiency.

I read...
1kWh of electricity produces 3,412 btu's and costs me $0.32/kWh so to produce 118,150 btu's costs me $11.08 in electricity.
1 gallon of heating oil has 139,000 btu's through an 0.85% oil boiler = 118,150 btu's as well but oil is $2.55/gallon
Natural gas costs about $1 through a 95% efficient boiler where I live to produce the same 118,150 btu's.

I don't disagree with you that NG is probably cheaper than geothermal for your specific situation. I'm interested to see what the price of NG will be in about 10 - 20 years after all of the cheap NG has been found and burned. I think the prices will be back to what they were in the early 2000's. Probably another topic for another thread.

In my case though, I don't have NG at the road. My heating fuel options are electric, fuel oil, propane and wood. Of those options, wood and electric do not fluctuate in cost like propane, and oil. So, we chose the electric / wood route. Slow and steady wins the race IMHO. I know people who heat with propane and have had over $700 a month bills. Our electric company offers metered propane at a locked in cost. I've heard of people paying close to $5 per gallon for fuel oil. When those fuels hit those prices I'm pretty sure my geothermal at $0.14/kWh ( what I pay ) is cheaper to run than propane and fuel oil.

If I use the NG defaults ( I am not sure what the going rate of NG is ) on this web site and change my geothermal efficiency to 350% ( 3.5 COP ) and change my electric rate to $0.14/kWh, it is actually cheaper than NG per 100 million BTU's. At $0.32/kWh ( what you pay ) it costs about double per 100 million BTU's as NG. Please see my post above for my actual heating / cooling costs.

I guess my point is, everyone's situation is different. Before you go and spend a lot of money on a heating / cooling system you probably equally vet out each type of fuel and your specific situation.