It's a smaller version of a standard house AC/ heat pump with a unit outside and unit(s) in each room. Sort of like a window unit divided into two sections.
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Heat Pump vs. Geothermal Heat Pump
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It's a smaller version of a standard house AC/ heat pump with a unit outside and unit(s) in each room. Sort of like a window unit divided into two sections.
Ductless Mini-Split Systems - AC & Heating | AlpineHomeAir.com
SageBrush
REJECT Fascism
No central air ducting. Each outside compressor/condensor unit's refrigerant is piped to evaporators with blowers ("air handling units") in one or two rooms.
The main efficiency advantage is moving small amounts of refrigerant over short distances rather than large amounts of air over greater distances. The second advantage is not having leaky ductwork.
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In some parts of the country I believe a geo thermal is a great idea but mainly on new construction. When we built our home in 2010 we got a 30% credit on all parts relating to the geo thermal which made the cost delta much smaller. I believe the tax credit is still there just at a lower percentage.
We use a pump and dump since we are near a small lake. We also use the desuperheater to lower the cost of hot water in the summer.
Since the geothermal is designed to run consistently I believe this has helped limit hot & cold spots in our home. We live in the Midwest and most of the contractors were not familiar with energy saving technologies so we had to lead them. With hot summers and cold winters it also made it ideal, along with workable non rocky soil.
I believe the biggest disadvantage with geothermal on new construction is that it is hard for builders, so they become reluctant. They do not want to increase the cost of the home on a future saving in energy bills. It is hard to sell that if you pay the extra $10-30k now you will be cash flow positive because the increase in your mortgage cost will be offset by your energy bill. Too many builders were caught up in the cost per sq ft game when we built our home. Hopefully that is changing.
We use a pump and dump since we are near a small lake. We also use the desuperheater to lower the cost of hot water in the summer.
Since the geothermal is designed to run consistently I believe this has helped limit hot & cold spots in our home. We live in the Midwest and most of the contractors were not familiar with energy saving technologies so we had to lead them. With hot summers and cold winters it also made it ideal, along with workable non rocky soil.
I believe the biggest disadvantage with geothermal on new construction is that it is hard for builders, so they become reluctant. They do not want to increase the cost of the home on a future saving in energy bills. It is hard to sell that if you pay the extra $10-30k now you will be cash flow positive because the increase in your mortgage cost will be offset by your energy bill. Too many builders were caught up in the cost per sq ft game when we built our home. Hopefully that is changing.
SageBrush
REJECT Fascism
Still present, and not going anywhere. The underlying issue is mortgage qualification. Energy savings are not calculated and in the banker's defense they have a legitimate argument since people tend to waste energy up to their monthly energy bill appetite.
There are so many new homes in my area with these roofs just ideal for solar, south facing, no penetrations, no trees, and none get solar. Correct me if I’m wrong, but I believe the entire electrical system in a new house would be eligible for the tax credit. It’s kind of shame.
When I first got my solar, it was very visually impactful on the house from the street. I’m glad though, because it’s gotten neighbors talking about it. Some hate it, but some like it and it gets their wheels turning.
nwdiver
Well-Known Member
I've often wondered where that line is... If I got a solar carport that cost $20k I don't think anyone would take issue with me using the FTC on the full $20k... why not the full cost of a home. Why is the home for my car different from the home for me?
SageBrush
REJECT Fascism
I think the best way is to build a not too big house, build it well, and install efficient equipment.
Musk says " The best part is no part"
I say the best dollar is one not spent.
I have a 35+ year old 2250 sq ft two story built well for the times and a really good Lennox 2 spd A/C.
My annual electricity use is about 7823 kWh. That was $704.07 for the past 12 months. With my Model 3.
I do have gas heat and water heat.
What would I spend on a system that would be economically viable? Looking at a 5 year payback about $3500.
I don't think that would get me much solar.
Musk says " The best part is no part"
I say the best dollar is one not spent.
I have a 35+ year old 2250 sq ft two story built well for the times and a really good Lennox 2 spd A/C.
My annual electricity use is about 7823 kWh. That was $704.07 for the past 12 months. With my Model 3.
I do have gas heat and water heat.
What would I spend on a system that would be economically viable? Looking at a 5 year payback about $3500.
I don't think that would get me much solar.
nwdiver
Well-Known Member
Our electrician DIY'd this 4.6kW system on his roof (you can tell he's not a roofer...) This cost <$3500 and will generate ~7,000kWh/yr in your area.
nwdiver
Well-Known Member
SageBrush
REJECT Fascism
Very true for summer where the use is for A/C during the day.
Exactly what I'm thinking with this thread. There are so many ways to make the wells cheaper.
That is funny about heating the ground during the summer. The earth is actually heated from within and so it is probably unnecessary to return the heat taken during winter.
Geothermal gradient - Wikipedia
SageBrush
REJECT Fascism
As I recall, the ground 50-10 ft below the surface is usually about the annual average temperature at the surface. Close to the surface there is some seasonal change in temperature but the deeper you go, the lower the seasonal change.
Regarding cost, in order to not pollute the water table, well drillers must be licensed and back fill the hole properly which seals the hole from contamination from above or below. It also serves to promote good heat transfer from the pipe to the earth.
Regarding cost, in order to not pollute the water table, well drillers must be licensed and back fill the hole properly which seals the hole from contamination from above or below. It also serves to promote good heat transfer from the pipe to the earth.
SageBrush
REJECT Fascism
I'm not sure about 50 ft but otherwise you are correct ... IF net heat is not being added or removed by other means.
The designers of these systems talk about a 'balanced' load.
https://woolpert.com/wp-content/uploads/2017/05/Got-Balance-In-Your-Geothermal-System.pdf
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That should have read 50-100 ft.
My proofreader has been fired.
I actually took a course from the 'inventor' of the Ground Source Heat Pump at OSU in Stillwater.
I read that PDF. I don't think I have heard about that. Seems it would depend on the thermal resistivity of the soil as well as annual heating and cooling BTU. Also remember that compressor heat must be added to heat from the building when in cooling mode.
Some of these devices can run solely to heat water. The efficiency can be 3-4 times better than a conventional electric water heater.
My proofreader has been fired.
I actually took a course from the 'inventor' of the Ground Source Heat Pump at OSU in Stillwater.
I read that PDF. I don't think I have heard about that. Seems it would depend on the thermal resistivity of the soil as well as annual heating and cooling BTU. Also remember that compressor heat must be added to heat from the building when in cooling mode.
Some of these devices can run solely to heat water. The efficiency can be 3-4 times better than a conventional electric water heater.
SageBrush
REJECT Fascism
That's right.
People have been using dirt as an insulator for millennia. That should tell you something. This company uses thermal inertia to store heat at 7 meters deep and says that heat moves as slow as one meter a month in the ground. Here is some of the involved math courtesy of Wikipedia. It's a first order differential equation by depth.
Interesting stuff.
This is a pretty big disadvantage to ground source heat pumps. If you need a secondary heater/cooler to even the load, that is not great for costs. Also sounds high maintenance - the imbalance will creep up on the unsuspecting homeowner unless someone tweaks the system.
What is the range of thermal conductivity?
Thermal conductivity ranged from 0.58 to 1.94 for sand, from 0.19 to 1.12 for sandy loam, from 0.29 to 0.76 for loam, and from 0.36 to 0.69 W/m K for clay loam at densities from 1.23 to 1.59 g cm(-3) and water contents from 1.4 to 21.2%. ... Increasing the percentage of soil organic matter decreased thermal conductivity.
Also water can move through dirt/rock. As above moisture content plays a big part.
Since dirt is more dense than water (mostly) then it makes sense to use it instead of underground tanks. Plus their heat source (sun) is 'free'.
For the electric utility I did a study on underground conductor temperatures. It provided us with lots of data. When you plant 8 three phase feeder circuits in a common concrete duct bank, you have to account for the heat generated.
AFAIK the home system can be handles by putting the wells apart from each other and making each one deep enough. I remember it being a 100 ft well needed per ton of A/C. I don't remember the spacing.
Thermal conductivity ranged from 0.58 to 1.94 for sand, from 0.19 to 1.12 for sandy loam, from 0.29 to 0.76 for loam, and from 0.36 to 0.69 W/m K for clay loam at densities from 1.23 to 1.59 g cm(-3) and water contents from 1.4 to 21.2%. ... Increasing the percentage of soil organic matter decreased thermal conductivity.
Also water can move through dirt/rock. As above moisture content plays a big part.
Since dirt is more dense than water (mostly) then it makes sense to use it instead of underground tanks. Plus their heat source (sun) is 'free'.
For the electric utility I did a study on underground conductor temperatures. It provided us with lots of data. When you plant 8 three phase feeder circuits in a common concrete duct bank, you have to account for the heat generated.
AFAIK the home system can be handles by putting the wells apart from each other and making each one deep enough. I remember it being a 100 ft well needed per ton of A/C. I don't remember the spacing.
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