/r/geothermal

Photograph via snooOG

A reddit focused on geothermal energy and geothermal electricity. All civil discussions aren't just welcome but wanted.


The Geothermal Reddit

Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. The Geothermal energy of the Earth's crust originates from the original formation of the planet (20%) and from radioactive decay of minerals (80%). The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heat from the core to the surface. The adjective geothermal originates from the Greek roots γη (ge), meaning earth, and θερμος (thermos), meaning hot.

Wikipedia: geothermal energy

Geothermal electricity is electricity generated from geothermal energy. Technologies in use include dry steam power plants, flash steam power plants and binary cycle power plants. Geothermal electricity generation is currently used in 24 countries, while geothermal heating is in use in 70 countries

Wikipedia: geothermal electricity


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/r/geothermal

5,180 Subscribers

1

High relative humidity

I have two systems, a package series 7 in the basement and a split series 5 in the attic for the second floor. 3,300 s.f colonial style house built in 1991. I’m in Maryland.

I keep both thermostats set 74 in the summer. The second floor humidity is between 68-72%. The first floor humidity is between 60-65% Day to Day.

I added a dehumidifier tied to the supply in the series 7 with little effect. I can see condensate being produced.

When I’m away for the weekend the humidity will drop between 3-5% but quickly go back upon return. I have no mold or anything but why can’t I get my RH to drop?

Recently closed cell spray foamed the basement, air sealed the attic and added R-60 loose fiberglass.

What else should I be looking at?

9 Comments
2024/06/23
01:27 UTC

3

Loop Temperature for 5 Series WaterFurnace question

Hey y'all. We did it! We went Geo in Maryland, waiting for all the things to be finished, but we have a working 5 Series WF unit. We have the AuroraWeb Link and love the data that it's giving us. Have a question though and it's more so I'm understanding how this works than anything else.

The symphony.waterfurnace.com site allows us to see all the data (along with the app) and I'm not understanding the loop temp data. I understand that it's measuring the temp of the fluid in the pipes, but I'm not understanding how it's relating to the cooling or heating mode of the unit.

Currently in A/C mode we have the house set to 76*F. The loop temp starts at say 57.4*F when the unit kicks in, but slowly rises (as I'd expect it to since it's absorbing heat from the house to reject it into the earth.)

So my question is this. Am I understanding it right that I would expect this temperature to rise over the course of the current cycle since it's removing heat from the house and moving it to the ground (and when it's off and not circulating, regardless of setting, it would move closer to ambient temp in the house), and it'll decrease in the winter since it's gathering heat from the ground and moving it to the house? Since the ground is a constant ~50*F all the fluid needs to do is be warmer/colder than the earth for the mode it's in?

If I haven't asked this clearly enough I'm sorry. I'll try to add more info as it's asked.

25 Comments
2024/06/21
18:31 UTC

2

Is this geothermal pricing reasonable?

Redditors, thanks in advance for your feedback.

We are rebuilding a home on the Front Range in Colorado. We've gotten a quote through our builder, but the builder isn't getting a second quote despite this being one of their first geothermal jobs. I was hoping the community here could sanity check the cost and offer any other advice about the system.

The house is two levels plus a walkout basement, with about 5,000 sq.ft. in total. We will be using a vertical closed loop system, and I think I heard someone say they plan to drill to 275'. Due to the house size and layout we will need a second split unit on the upper floor. Between the two units, I believe it is a 5 ton system. All in, including ducting and drilling the system is coming out to just under $100,000, of which approximately $30,000 is the drilling. We are getting substantial rebates, including some beyond the standard rebates and tax credits that help bring the total cost down.

The major components of the system are below:

Climate Master-QEV0930AGE02BLS Trilogy 45 QMode up to 2T with dedicated water heater

Climate Master-VEV0930AGE02BLS

Climate Master-AWS085AW1245S 85-gallon Smart Water tank for QEVs

ClimateMaster Auxilliary Heat Geothermal Back Up Heater 10KW ELECTR HEATER SIZE 036-069

2x Climate Master Web Based Thermostat AWC99U01

2x 20x25 MERV 13 Media Air Cleaner

2x Broan B130E65RT ERV - tied into main ducting

Does this seem reasonable? Is there anything you would add or change? We are hoping to have very clean indoor air to help with allergies as well as wildfire smoke.

29 Comments
2024/06/20
22:24 UTC

1

Geothermal loops vs mini split coils

Sorry if this is a stupid question but my understanding is that geothermal and mini split works on the same concept of taking heat out of one area and depositing it to another. Ie from the ground to the house or from the air to the house or visa versa. For a geothermal your loops are massive often thousands of feet but for an air source minsplit the heat pump coil is very small comparatively. Why is this. Wouldn’t a mini split work better if it had more coils? Like if you out door unit was the size of a refrigerator there could be so many more coils for heat exchange or is it already optimized so that with the limited number of coils in the current design already performs the “best” it can and adding more is not useful?

7 Comments
2024/06/20
05:19 UTC

3

Is it bad to oversize a heat pump if it has variable speed?

24 Comments
2024/06/19
13:09 UTC

3

Geothermal system for heating, cooling, and hot water?

My dad is wanting to replace his gas furnace before it fails and is considering geothermal as an option. Currently his house only has hydronic heat and no cooling other than window AC units. The gas furnace also provides hot water for the house so that would ideally also be provided by the geothermal system. Is there a good way to get heat, cooling, and hot water from a geothermal system in a house that doesn't have ducting? Is it even possible to do all of these things? He doesn't want to cool the current hydronic system because the way it's set up he's worried about condensation in the floors, so cooling would have to be done by ductless air handlers. Is this feasible?

8 Comments
2024/06/17
22:05 UTC

5

How far away from your house can you drill for geothermal?

How much energy Will be lossed When the pipe exists the hole and go to your house(like if it is really hot/cold outside and you have cold/hot air in the pipe)? How much of the pipe is insulated?

22 Comments
2024/06/17
14:46 UTC

0

Building a residential geothermal system to generate electricity

Was looking for ways to reduce home expenses using a large backyard, and stumbled upon residential geothermal systems to generate electricity.

I know these are typically large plants, but why can't we build small, binary cycle generators in our backyard with the right economics? I found that water temps as low as Chena hot springs in Alaska have worked at 135 degrees F, so I wondered if even lower could work. Millions of Americans could make money utilizing their vacant backyards and generating electricity 24/7.

Worked on a basic design/economics over the past couple of weeks. Experts, please pick apart this concept before I spend $ building it. Where am I off?

  • Design: Binary cycle system reaching a depth of 1000 feet, with 10 degree Celcius difference in temperature (an optimal location like CA or CO. Put heated water through a heat exchanger to boil and vaporize a working fluid (hydrofluorocarbons, ammonia, etc) which then powers a turbine while water gets pumped back down

  • Assumptions: Flow rate of 5 kg/second. 15% efficiency for converting Q into electricity. 70% pump efficiency.

  • Energy generation: Q = 5 kg/s * 4.18 kJ/kg * 10 C = 209 kW * 15% efficiency = 31.35 kW. Annual revenue = 752 kWh/day * $0.20/kWh * 365 days = $54,924

  • Pumping Costs: Power input = 1000 kg/(m^3) * 9.81 m/(s^2) * 305m × 0.005 (m^3)/s​ / (70% pump efficiency) = 21.39 kW per hour. Annual costs = 513 kWh/day * $0.20/kWh *365 days = $37,474 + ~$3000 in annual maintenance.

  • Build Costs: 1000 sqft * $50/foot = $50,000 drill cost (~rate of water wells at that depth). $30k for equipment. $10k for labor. $10k for permits/misc costs. $100k all-in. No tax credits included here.

- Payback: $14,450 net profit / $100,000 build cost = 7 year payback.

With electricity demand in America expected to double in next 15 years (while power grows 0.5%/year), this seems like a great way to meet that demand and help Americans make money by generating clean electricity 24/7.

7 Comments
2024/06/17
04:53 UTC

3

Vertical vs horizontal loop length; why do verticals tend to be shorter in total length than horizontal?

I see lots of posts that essentially seem to imply that horizontal closed loops need to be a lot longer than the vertical drilled loops. Why is this? Why can't the horizontal loops be just as long (short) as the vertical loops, provided they are at a stable ground temperature depth?

I have seen posts on here that require two 400ft vertical drilled loops to supply a 6 ton geo unit, but the same 6 ton unit requires something like 1200ft 1600ft of horizontal loop? Why the difference?

12 Comments
2024/06/17
00:07 UTC

6

Quote in Midwest

Good day! We would like to replace our current geothermal system with a new one. It is 20 yrs old and the AC is no longer working. I know nothing about geothermal - except the fact that it seems to be the way to go. Does this quote look reasonable overall? Is there other equipment that we should be considering? I really appreciate the feedback! This group has educated me a lot already!

Will this system heat/cool both levels? I am a bit concerned because the salesperson is pushing me towards removing our current geothermal and replacing it with a Trane furnace/AC heat pump that will cost $26,000! With the geothermal credit, this system would be cheaper overall. That is why I am so confused. It seems like a no brainer to replace our current geothermal system with another geothermal!

9 Comments
2024/06/14
17:58 UTC

1

Help with set up design

Good afternoon everyone, I'm currently trying plan and design a system to help cool my home in the summer. I live in maine so our ground temperature at 3 to 5 ft in depth averages 45⁰ to 50⁰ F . My home is 1200 square feet and is 2 levels with a basment. Summer days can average 78⁰F to 66⁰F in late evenings. I want to dig down after having the utilities marked by the city/ electrical company and do a sand bed lay down my pipe loops probably pvc or plastic. I also plan on running a piece of THHN green jacketed wire along my lines so the utilities company can find it later on if i sell the home one day. Then pressure test the system as I plan to use liquid in the lines probably something similar to antifreeze to avoid lines freezing in winter. Another layer of sand and then fill in the trench with the excavated soil again. I plan to get an old ac unit like a cubical shaped condenser unit , remove the actual condenser from inside and install a water pump ( probably one from the coolant system of a car just need to look at flow rate needs ) then hook up my inlet and return lines so we have ground loop > liquid pump > radiator > back to ground loop. I'm pretty well versed electrically but hvac and plumbing I dabble in just enough to troubleshoot and make simple repairs. I also plan to eventually power the system via solar power but that's a task to do after I have a working cooling system. Any tips or sources would be appreciated. I would love help doing the math to find out how much pipe I would need to get the right BTU for my home.as I can't find anything on that. Or if the liquid is 50⁰ then how cool will the air will come out after passing through the coils of the radiator exposed to the 75⁰F air. Thanks everyone!

2 Comments
2024/06/13
03:02 UTC

2

Maybe I should do some consulting..

I’ve noticed the trend where people can’t find qualified installers. This is an unfortunate side effect of the trade deficit in HVAC most of the experienced tradesman are retiring en masse and not being replaced en masse, and furthermore there is a movement to push fast easy money instead of actual expertise.

I would recommend looking for IGSPHA certification among companies. www.igshpa.org is the International ground source heat pump association. Anyone who has any real interest in installing geothermal systems of any merit is a member, and certified. That’s not saying there aren’t smart contractors out there who do a good job but this is probably the best resource for quality that a layperson could use to gauge a company. It’s like hiring an ASE mechanic for your car, NATE also has some geothermal certifications that would identify someone who knew what they were doing.

I’m not actually sure my IGSPHA is current as my company performs a broad spectrum of service but we have a record going back to 1981. I’m not selling anything but I’m interested in answering some questions if anyone here is interested.

A lot of contractors have abandoned geo because it’s a hard sell due to initial install price, instead they choose to perpetuate this myth that split inverter systems are equivalent in energy savings vs cost. For your average spec home, or low square footage you may have an argument that the cost isn’t worth the savings. But if you’re building a high end home, business, or have a lot of square footage it’s absolutely the best option in my opinion. The equipment won’t work as hard, has a potentially longer lifespan, and savings compound when you go with an inverter driven geothermal. Plus the added benefit of creating domestic hot water, pool heating, or radiant floor tie in, plus avoiding unsightly outdoor equipment and noise. It doesn’t hurt for contractors either that an air to air system can be installed in a day, and geothermal take more effort.

Anyways I’m going to monitor this thread for a few days and help if I can, I have some contacts all over the country from my days teaching and working with manufacturers.

23 Comments
2024/06/11
05:22 UTC

2

repair or replace with on demand water heat

Hi, I'm in a moderate climate, typically just a few weeks below zero. I just bought a ~1400 square foot two floor house that came with a ten year old Waterforce Envision system connected to loops in the floors. But it has a problem, probably the compressor is broken due to a failed capacitor.

The setup is jammed in a tiny closet, so half the repair estimate is getting access for the repair. A neighbour has the same system, he says it's a good system but the installer didn't really know what they were doing and there are some questionable choices in how it was set up. It seems to me to be a very complex system, with many things that can go wrong.

I'm considering adding a mini split system to the house, with attic based ducts from it for the second floor and maybe a wall unit on the main floor.

This is probably sacrilegious, but I'm wondering if it would be possible to … simplify the floor loop. I've read that on demand water heating (eg Takagi TH-3) can be substituted for the geothermal part to heat the existing floor loops. The home already uses an on demand water system, from what I've read it might be possible to use it for household and heating use. It would pain me to do this because geothermal heating was a positive factor in the purchase, and electricity isn't cheap here (natural gas is an option), but I think between what the mini split can do with the floor heat for backup/comfort, it's maybe not worth the complexity, and I'd gain some closet space.

I'm definitely open for other ideas, but simplification with ultimately similar costs would be really appreciated.

7 Comments
2024/06/07
15:07 UTC

7

So is geothermal worth ~2x an air source pump plus a ruined back yard ?

So I have space for a geothermal system on my property but it is 2x of a ducted air source plus my back yard being drug up with including the trees I planted with my now dead mom .

I’m trying to convince myself that the geothermal makes sense at double the price . I don’t think I will get pay back in a reasonable period .

I live in a very cold region which will require some backup with a air source even the most high end type

I also know I’m asking on the geothermal sub

Edited to add

In Canada so litres and CND

Current system

Oil ~ 1000 litres at ~$2 litres

Cost of power

It’s tiered but marginal (so only the powers in the bracket is charge at that rate )

1<1000kwh .

$.201 kW

1000kwh<25000 keh $.22

2500khw < $.24

Cost is about double 30 v 60k with rebates being the 40% up to a total of $8,000 .

I could also do a mini spilt at 16k

51 Comments
2024/06/07
09:11 UTC

1

Sanity check on new house build geothermal

I am building a new house around 2800 sq/ft. High performance build. It will have full basement, but not finishing it out to start and when we do it will only partially be finished. All electric. The Manual J I had do has 32k btuh heating and 26.5k btuh cooling with around a 43.5k btuh heating if you include future basement. I didn't plan to go geothermal initially and was having some higher end heat pumps quoted, but one of the HVAC places mentioned they also install geothermal. The price difference wasn't that far off from some of my other quotes. Since the the tax credit for new construction only covers geothermal it seems like this is the best option, but just making sure. I reached out to 4 different HVAC contractors for quotes and two carried Bryant, one Carrier, then last one Trane/Mitsubishi.

The three quotes between the Bryant and Carrier places were almost all quoting the exact same system so only need to list one. All ductwork is included in these.

Bryant dealer, which was very helpful had two options either

$26,700 - 4 ton Bryant 38MURA system

$30,300 - 4 ton Bryant Evolution 284ANV048

Trane/Mitsubishi/Waterfurnace Dealer. Initially I came to him since he was a Mitsubishi dealer. He quoted me Mitsubishi system and said they are nice, but he wanted to let me know if down the road any repairs could be costly compared to the Waterfurnace system.

$19,800 - 3 ton Mitsubishi HyperHeat

$26100 - 3.5 ton Mitsubishi HyperHeat (commercial unit)

$31400 - 3 ton Waterfurnace 5 Series two speed

$33500 - 4 ton Waterfurnace 5 Series two speed

Closed ground loop system(120'x50'). He recommended the 3 ton and thinks it will handle the basement fine and only on coldest days the backup heat strips would be needed.

Does the geo make the most sense and any other specific question I should ask?

23 Comments
2024/06/07
04:08 UTC

4

Can I drive over geothermal systems with a semi truck

As the title suggests, can I drive over geothermal water systems with a semi truck, and can I plow snow off of the ground it’s laid in or will that cause it to freeze up in winter?

9 Comments
2024/06/06
15:30 UTC

2

Considering Additional Vertical Well

Hi all. I'm in the process of getting an estimate for adding an additional vertical well to my existing GSHP, which has been running since about March 2024. For background, I have a bit of an atypical setup: 2x 3T WF7 units (one cabinet, one split) running on a vertical loop using 2x 375' wells (in parallel) that go through a ton of limestone in the ground. These two wells were drilled before my new construction started in August 2023.

I've been concerned for a while that my loop size is too small, as I'm essentially running 6T of compressor capacity on a 5T loop (and only 150' *5) to heat and cool about 4500 sq feet of living area. My installer originally planned on a single 5T system, but I went with 2x 3T for redundancy and additional heating/cooling power. Despite that change, they recommended sticking with the original 2x 375' loops primarily because it was already done and the high cost of drilling through so much bedrock.

I realize this decision almost certainly won't provide much or any ROI, but it will give me some additional capacity comfort which is valuable to me as we plan to stay in this home for 20+ years. I'm a bit of an "overkill is underrated" guy.

My questions:

  1. Any "gotchas" that I should be thinking about as we start the estimate process? (Note: u/djhobbes, u/zrb5027, u/Engineer22030, I've really valued your insights as I've dug into this subreddit. Thanks so much for your contributions and I'd appreciate your thoughts if you have any).
  2. I'm assuming the 30% geothermal tax credit would apply to this additional well as it's part of my install. Anything special I do there?
11 Comments
2024/06/06
14:55 UTC

1

Circuit designing for geothermal systems

Does anyone design these in their own business or work for a company that does this? How much does the schematic help the people on field? What do you think schematics get right and wrong?

5 Comments
2024/06/06
04:12 UTC

5

Thinking of Geothermal cooling system for new PEB factory shed in India

Hi all, I am from India. During summers the temp. goes upto 50degC here and it becomes difficult for manufacturing workers to work in this climate.

I am setting up a new 20,000sqft PEB factory building on my 2 acre land. I am thinking of installing Georhermal air cooling system with underground HDPE pipe in either horizontal spiral or through vertical closed loop inside rainwater harvesting tanks which will be 12ft deep.

The cost of excavation will be zero in my case as I have to fill up my complete land 6ft high with soil to match with the road NGL level.

I have few questions: a) Horizontal air system inside soil or vertical system dipped in water tanks, which will be efficient?

b) How to prevent mold and dust in pipes. What maintenance and type of heat exchange pump required?

c) Which are the good heat exchangers available in India/Asia?

d) Since I am not able to find consultant or contractors in India, so is there any suggested book/YouTube channels to DIY geothermal system.

I am open to any suggestions. Thanks in Advance.

1 Comment
2024/06/05
20:09 UTC

3

Geothermal Cooling

Planning a geothermal hydronic system. Want to use radiant floor heat. What would be the most economical options for cooling?

13 Comments
2024/06/05
19:49 UTC

1

Prefilter mesh for geothermal

I have an old WaterFurnace Premier 2 geothermal system, open loop, that runs off well water. Right now there is a spin down filter between the well and the geo. It has a 1” slip and currently has 60 mesh stainless steel screen. My problem is that it seems that too much sediment is still making it in to the system but the spin down filter ALSO gets clogged up pretty quickly. So I’m wondering if it’s a bad idea to step it up to a 100 mesh filter (or higher). My other thought was adding a second spin down filter with 100 mesh after the 60 mesh filter so the 60 mesh catches big pieces then feeds into the 100 mesh for a bit finer screening before feeding in. Would either of those options be too detrimental to flow rate into the system or cause any other problems? Any other suggestions would be welcome.

0 Comments
2024/06/05
00:17 UTC

1

Air Source Forum

I'm sure there is an airsource heat pump forum. So why do we talk about airsource so much on this geothermal forum? Hardly a geo post goes by without someone bringing up airsource as a "better" option.

I'll add this is not an US forum either so don't assume so.

Let's stick to the OP's question and if they ask us to compare, sure go ahead.

Edit. I concede. Air source it is.

14 Comments
2024/06/04
21:06 UTC

8

how efficient is a geothermal heat pump compared to an AC unit?

how much energy can you save if you switch from ac to geothermal?

13 Comments
2024/06/04
16:51 UTC

2

Adjusting "Dealer" settings?

I had a waterfurnace series 5 system installed with AWL and a Symphony thermostat. After a couple years I'm wondering if I can and if it would be a good idea to adjust some of the dealer settings.

  1. The air filter change reminder - the dealer has it set to every 6 months but the April Air filter says it should be good for 12 months. Any issue to changing the reminder to 12 months? How many hours run time do you have your system set to?

  2. Differential - Looking to change the differential to 1.5 degrees for the stage 2 and Aux heat. My thought process is to allow the first stage time to bring up(or down) the temperature if I change it and limit any Aux heat.

  3. Aux Heat Lockout - thinking about locking out the auxiliary heat until the outdoor temp is below 20 deg. Again just trying to limit the auxiliary heat coming on if I change the temperature.

  4. Completely separate - anyone know how hard it would be to install a loop temperature sensor? I'm fairly handy and it's not worth paying a dealer to install it but I would like the data.

Edit: I was able to figure how to change the settings but I'm still curious if anyone else has done the same or seen negative consequences from changing them.

Thank you!

5 Comments
2024/06/04
15:55 UTC

0

Horizontal loop install.... Can I used standard HDPE service tube?

Hey all, Looking at doing a DIY install and starting to source components. I see a few place selling kits but I'm curious if the pipe they are using is just standard "Poly"?

I.E. If I just used normal CTS HDPE tube would that be the exact same stuff being recommended for a best practices install? And when people are calling for 3/4" are they measuring OD, nominal, or ID?

Thanks!

6 Comments
2024/06/02
18:26 UTC

3

Cost to run

I have an 1,100 square foot house in northwestern Pennsylvania. I currently have an oil forced air furnace in the house. I primarily heat with firewood with my total fuel oil consumption only being 50 gallons this past winter. I current electric provider kills me on the KWH which is right at .15 cents per KWH. I keep walking the line with installing a horizontal geothermal system. I own equipment and dig the trenches and backfill everything myself. I am looking at moving away from the firewood. With my current KWH would i save money heating with the geo vs oil? I have never tried heating the house a whole winter on just oil. I burn roughly 4-5 cords a winter. Thanks everyone!

11 Comments
2024/06/02
02:40 UTC

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