geothermal stirling engine

[preoccupied]

If I pump underground air (here in Michigan I think it would be 47F) into a hallway and on its opposite wall it has outside air possibly 30F, then what kind of Stirling engines would be best to harness that energy?

I think V shaped Alpha Stirling engines would be good because one piston could sit out in the cold and the other could be in the 47F temperature. But I can't help but feel my scope of imagination isn't whole. Please guys, I would really like this to be an addition to a house in the future. Also how many thousands of Stirling engines running at a temperature difference of 17-25 degrees would it take to power a generator that could power the house? EIA says in 2012 average daily electrical usage per month was 903 kWh per month.

[jim_mich]

The problem with trying to harness heat from the Earth is that ground temperature averages about the same as air temperature for much of the time.

Michigan's well water temperature is about 55ºF This also happens to be the air temperate averaged over a year's time period in Michigan.

Yes, average electrical use in the USA is about 900 kWh/month. My usage is about 380 kWh/mo. except it peaks around 600 kWh/mo in the middle of summer (air conditioning) and middle of winter (furnace fan motor).

Heat engines become more efficient with greater heat difference. Inversely, heat pumps become less efficient with greater heat difference.

When I built my house, I contemplated installing ducts (PVC pipes) buried at about basement floor level and extending about 10 feet outward, zig-zag fashion. I then intended to use a simply roof mounted solar collector to heat summer air and pump it through the underground piping. I ran short of funds, and simply built a normal house. It could still be retrofitted in such fashion. I calculated I could store enough heat within the ground to heat my home completely. Styrofoam sheets would be placed as a cap a foot or so below the surface. thus allowing a normal yard and such.

[preoccupied]

How much heat would a solar tube give to the underground air? That solar heat might help if I create a hallway with warm pistons on the inside and cold pistons on the outside.

I know it might not be the most efficient method to generate energy. I still don't know the answer to my question, how many thousands of Stirling engines on the side of a house would be needed to generate enough electricity for the house? I know Stirling engines have limited torque so they would work together simultaneously and assuming that their collective force is equal to each of them running individually plus each other, how much would be need to generate that power? I guess what I'm asking is that I don't know the answer to is how much power would one Stirling engine have exchanging 17 degree heat difference?

[preoccupied]

I want to use earthairtubes.com to provide high air pressure in the home that I am wanting to design, cold air during the summer and constant fresh air during the winter. I've been exploring the net and earthairtubes.com looks like a good geothermal source of air. Any better finds in the same product line elsewhere, guys?

I want to use a product similar to solatube.com for day lighting and actually I don't intend to install light fixtures in the house. In the dark of night creatures delight or at least I will, with like a flashlight or glow in the dark stuff because there is no way I'm spending electricity on anything other than kitchen appliances and electronics.

I don't want to spend anything on heating my water or heating the air in the house. I want like solar powered heating so I looked for it on the net and found this website solartubs.com. It would heat the pool, hot tub, and hot water heater and heat my air. The warm air from this solar power would help power my Stirling engines which I want located covering entirely a 10 feet by 45 feet outer wall of the building.

I believe with the help of the solar power that I could have like 110F air in a hallway on the opposite walls of the stirling engines during the winter for the Stirling engines to interact with. And then I could have 50-60F degree air or if I dig really deep 47F degree air during the summer to interact with 80 degree air potentially. Since there is already a 33 degree difference with that, maybe an electric/solar cooling mechanism could be used. The heated coolant according to the solartubs.com website makes air cooling or refrigerant liquid more efficient. That efficiency might produce positive return for the Stirling engines. Knowing for sure would require much more effort by me but maybe not to someone else who is more talented.

Finally I would like to be completely independent of city utilities by adding a water tower and a private water treatment system. I want to thermal depolymerize the human feces and urine and get the byproduct of fuel and clean water. I would take the water byproduct from the thermal depolymerization and put it through additional purification to remove impurities like heavy metals if I can. This is a bit over my head, I'm not going to lie. I want to use the process owned by changing world technologies but on a smaller scale. Changing world technologies is now owned by ridgeline Canada inc. They don't respect the patents on pharmaceuticals so I can just ignore the patents they own for fuel conversion, right? Just kidding.

I remember other water purification methods like what is on gravityassistedpower.com. I'm not sure this would be a good reverse osmosis method but I have an open mind. I would need one more step to make sure the water is perfectly clean after it leaves the thermal depolymerization even though I am pretty sure after thermal depolymerization it is basically distilled water.

The house I drew is for a 0.34 acre lot. People say I drew it too big and wouldn't be able to afford to build it. Maybe they are right because it is a two story 60 by 100ft house. I wanted to think of ways to make the construction really cheap so that I could have this design made, since my budget is never going to be very much. I thought that if I lay the foundation myself with friends and free help that maybe I could get a good price on cement, and install a pool right into the foundation and have over half of the first floor be a large pool room with a 20 by 40 pool and a hot tub. The pool and the foundation should only cost as much as laying the foundation for the house so I would get a huge bonus in laying my foundation by also creating a high quality cement pool. If I could do the construction myself and with free help and engineer the building myself and create a detailed construction plan myself I would save and maybe fall within a budget I could afford. However, I fear that I will have to settle for a smaller building since this is just ridiculous, what I'm proposing.

[preoccupied]

Yes, average electrical use in the USA is about 900 kWh/month. My usage is about 380 kWh/mo. except it peaks around 600 kWh/mo in the middle of summer (air conditioning) and middle of winter (furnace fan motor)

Jim_mich,
If you are interested in a good insulation for your house, aerogel is possibly the best insulation out there. You can take a blow torch to this baby without exchanging heat to the other side. Super special awesome ! Having good insulation might be more cost effective than having free geothermal air.

http://www.buyaerogel.com/

In my design for this house that I want to make I am planning to design it to be built with autoclaved aerated concrete which is also a good insulator. I don't think it will be in my budget to use aerogel, but that would be sweet though.

This looks like a great autoclaved aerated concrete company. Does anyone know a better one?

http://aerconaac.com/index.html

[preoccupied]

I started drawing the floors of the two story building that I have in mind. It's a work in progress. I don't know much about the subject of home design. In my mind, I want to reduce the number of walls to make it cheaper to build using autoclaved aerated concrete bricks. Like, imagine a regular house, 1250 sq ft and times the open space by 4, and you have 5,000 sq ft. So a 12,000 sq ft home is about the material cost of a 3,000 sq ft home with 4-5 times the open space. Wide open space in rooms and hallways is trendy. And I think large kitchens are the bomb too.

I want to use geothermal stirling engines on the bottom left corner of the first floor drawing, picture 17. That hallway space is supposed to have stirling engines and hot or cold air in it that is interacting with the hot or cold air outside. If the Stirling engines are interacting with 55 degree air outside the inside air would be colder or warming and would be solar powered to be that, using the solar tubes which can make air conditioning and heating more efficient.

In picture 17 I want to save on walls not having as many walls and install a pool at the same time which would be a huge value. Indoor pool rooms are really cool. I think if I made the pool part of the slab for the house that I will save huge on the installation of the pool, especially if I design it myself set it up in advance very carefully and have volunteer labor and friends help me lay the cement instead of a construction crew.

The second floor picture sixteen has enormous 4 bedrooms, one bath and wide open space for two areas that are like dens. The hallways are enormous like 8 feet wide. Maybe I'm thinking too big but the way I see it, it is just like a 3,000 sq ft house with 4-5 times the open space.

On the roof, picture 15, I have drawn a flat roof with solar tubes spread out to collect heat from the sun and circles on the utility room on top that collect light through tubes for lighting.

There are some really cheap okay size lots in poor black neighborhoods that this would fit nicely into. If I can buy a large lot for under $4,000, maybe I could cheaply build a huge house there and be the big man on the block. What I really want is stirling engines powered by geothermal and solar powered heat and cold to produce electricity to sell back to the grid - the huge house thing is just a side effect of thinking about it...

[daanopperman]

Hi preoccupied ,

U are going to have to purchase half of the state of Michigan for a erection site for all your Stirling Engines .

[preoccupied]

I only require 180 sq ft for my stirling engine wall. Michigan has 511,156,800 sq ft in which I can place this wall which means I do not require 50% but rather 180/511,156,800=0.000035%.

Why do you think I would need 50% of Michigan? Show me your numbers and then I will give you a ham sandwich and a beer.

[daanopperman]

Hi preoccupied ,

First , the temp. difference between hot and cold , (take the volume of your hot chamber ) and calculate the (Boils Law ) expansion coefficient of the volume of air for that temp rise , that will be the amount of pound per square in. you will be able to use in your stirling , Different gas will give you more or less expansion , don't use Nitrogen , it is almost non expanding with small difference in temp . If you use the Stirling you intend to use ,the displacer is the same volume as the working cyl. so calculating the force on the axel is not to complicated . These engines is good for high temp. differences , so is the rhombic , alpha and beta .
If you use a simple Stirling (which I think will suit you best ) , you have to decide how much volume for the amount of expanding gas you will be able to use in your power piston , this will give you the volume or dia of the power piston . With one side of the power piston open to atmosphere you could use the atmospheric pressure to help you return the displacer piston to the hot side of the engin . The displacer piston should be of a material that does not take up heat readily , and it is not needed to shield the hot components from the cold components as in the rhombic or alpha engines . The displacer should not be of a too close fit in the hot chamber or you will suffer pressure biuld up inside the cold side of the engine when the hot gas is transferred to the cold side , but it should be such that as much as possible of the hot gas is transferred to the cold side . The displacer should reach almost to the hot "head" and the cold "head" to maximize expansion and contraction of the working gas .
You will have to build your own Stirling . After calculating all the data , you should be able to see how many of these engines you will need to power your LED lights in your house . Personally I don't think a Stirling engine is worth what it is claimed .

[preoccupied]

daanopperman,

I had changed my method a little for how I want to add stirling engines to the house. I wanted to solar power the heating and cooling using solar tubes. That way I can have boiling air on the inside during the winter and freezing air on the inside during the summer. If I have boiling air, at like maybe 170F, then would an alpha stirling engine work best?

I think I'm really barking up the wrong tree by thinking I can calculate an optimal stirling engine for a given temperature since my abilities are not that great, I'm not going to lie. I'll look into it carefully but I just know I will be met with an intellectual challenge that will bring me to a grinding halt.

[daanopperman]

Hi preoccupied ,

I don't know how hot boiling air is , but 170 deg f is only 76 deg c , to little to Boyle water to drive a steam engin , but enough to run a displacer type Stirling engin for show , but does the hot air come out of the ground under pressure , then you are in business . You can amplify the pressure by using a large cyl for the low pressure air from the ground , connected to a smaller dia cyl for high pressure to drive almost anything wrt the pressure available .