Friday, August 24, 2007

Wind Turbine Heat Pump (Geothermal Transfer) For The Home

I am a lawyer who has been interested in the subject of energy conservation since the seventies. Back when we had the first OPEC crisis, I thought this country would head in a direction away from the consumption of huge quantities of oil and gas. It didn't happen. Now of course, our thirst for oil has been the primary reason for a preemptive war with no end in sight. Moreover, peak oil seems to be here. And so far nothing much seems to have changed. But the public, may at last be ready for something different.

There are some real promising things happening with new solar energy systems and with wind turbines. It is long past due. But I still keep wondering whether we are approaching this problem of solving our energy demands the right way. With both solar and wind systems all technology seems to be headed toward the creation of electricity. Electricity is definitely useful but often inefficient.

Heating and cooling costs are about 60-70 percent of home energy costs. It is far more cost effective to use heat transfer than to make heat. Water source heat pumps are 300-400 percent efficient while the best ordinary HVAC systems might be forty percent efficient. (Are they that much?) What if you could even vastly surpass the efficiency of a water source heat pump. How? By making the wind pump the water instead of an electric pump.

Why not use wind to its best advantage? Make the wind do what it has done very efficiently for hundreds of years: pump water. Make it pump water from a warm place to a cold place and make it store the heat where the heat is needed or wanted. In the winter pump the heat from under the ground into the house. In the summer pump the heat from house into the ground.
To do this, because of the wind's variability, one would need a huge (?) thermal sink in the house to slowly release the heat transferred from underground to the heat sink or to transfer the heat from the house to the ground while the wind was not blowing.

A four part system. A wind turbine. A pump. A closed loop of pipe. An interior thermal sink.

It is fairly well known that in most climates, five or six feet below ground, the temperature is a about 55 degrees. I think it is quite possible to take advantage of the geothermal underground temperature by using a wind turbine to pump water from underground into an interior thermal sink. If a large enough volume of water could be circulated to where the interior heat sink reached 55 degrees, I think such a home's heating and cooling costs would be drastically reduced.

If the large thermal sink could get the house temperature substantially raised in the winter and substantially cooled in the summer, very little additional energy might be required to bring it to a desirable temperature with the use of a water source heat pump. A water source heat pump would work in tandem very well by using the internal heat sink as a convenient source to operate a water source heat pump.

My idea would be to use a vertical wind turbine on the roof coupled to an Archimedes screw to pumps and circulates water through the closed loop. The vertical wind turbines seem to need less wind, have more torque, and are quieter. I also think that from an architectural point of view, they would look much more attractive, especially the ones that look like spinnerets. They also take advantage of a sloping roof which increases wind speed.

I also think the Archimedes screw would be an ideal pump. It requires no gears or lubrication and could attach by a straight shaft to the vertical wind turbine. An Archimedes screw would be very inexpensive as pumping systems go and extremely reliable as there is really nothing to break.

I have other ideas about roof design and about turbine design for greater efficiency. I also have ideas about the plumbing. What I would like to see is whether there are people out there who think this idea has commercial merit and if so, how we might go about making wind driven water pumping for geothermal transfer a success. We would need some engineering and architectural expertise and some ability to fabricate the wind turbines and pumps.

I look forward to responses.


Unknown said...


Interestingly, I have come to similar conclusions regarding the use of rotational energy from a rooftop VAWT. I did not see the logic of building a complex low RPM permanent magnet alternator just to dump the power into a resistive load to heat water. Right now heating oil is approaching $4/gal. My thought was to use the VAWT to drive a low RPM compressor directly and using it as a heat pump. Although I live on the ocean and have (not too legal) access to boundless salt water, I was originally thinking of designing this as an air to water unit. Your idea of using the VAWT to pump water has merit, but isn't the biggest energy load in such a system the compressor? How much would be saved by pumping and storing 55 degree water? My well has a 1/3 hp pump and is 326 feet deep. I doubt that eliminating it as a load would have as big of an energy impact than heating air or water by driving a compressor.

The idea of a heat sink, presumably a big tank of water also has some practical issues. I have looked into this at length with the idea of storing solar collector energy (perhaps wishful thinking where I live). Plastic (PE) tanks are cheap and can be had in great varieties of sizes and shapes but if stored in the home can be worrisome sources of potential floods. Unfortunately they also lose strength as the water temperature increases-not a problem with your scheme, but think about the effect of 1000 gallons of 55 degree water in your basement. Not exactly a cozy prospect. You'd be better off sinking a plastic septic tank in your yard and using that for your heat pump source--as long as you got rid of the cooled water as it exits the heat pump.

The problem with my scheme is to find and engineer the parts so that the power source is well matched to the downstream components.I have no idea how to go about finding the right compressor, how much rpm and torque it would require, whether a powered clutch would be required, etc. The initial phase would be to cobble something together using auto parts but any input would be appreciated. There are several patents relating to generating heat using wind power, mostly by friction but this seems crude compared to the heat pump idea. Bruce

Pete Schneidler said...

I live in rural western Alaska where it is very cold and very windy all winter. Even in summer we don't get over 80 degrees F and wouldn't need any kind of cooling aspect. I initially was interested in a turbine for electricity which retails at some of the highest rates in the nation ($.46/kWh) due to small populations and the distance they have to haul the fuel for the diesel-powered generators. But the power co-op isn't keen on net metering. So as an alternative to a big fight with them I wondered about using a turbine to displace heating fuel, which costs well over $5/gallon. I can't believe there is nothing commercially available that will do this. Maybe we haven't looked hard enough?

Unknown said...

I have reference to a system which converts wind energy directly to heat energy using friction. It was a project by the swiss in asia. Its big, but can boil water or make hot forced air.

cant seem to find anything modern like it:

Village Earth Appropriate Technology Reference Library

The Heat Generator (A device to convert mechanical power directly into process heat)
By Reinhold Metzler
Published by: Swiss center for Appropriate Technology
Varnbuelstrasse 14
CH-9000 St.Gall

garrymile said...

I have been working on a project for the last couple of years to convert summer solar heat to winter heating. The idea is to have a storage tank (underground, but outside my new house) in Southern Ireland.

I had already considered the idea of using wind to power a ground source heat pump, which can triple or quadruple the energy input.

As you can expect, there are complications and obstacles but where I have got to at present is as follows:

I am about to build an underground tank that is highly insulated, so much more efficient than using the ground as suggested. There is a system called insulated concrete formwork - ready made shuttereing or casing into which concrete is poured. The intention is to have about 10" insulation altogether plus an internal liner.

I will then have a bank of 8-10 solar panels to heat the water in the summer. I intend to supplement this in time with EPDM solar pool heaters, which are not as efficient but are much cheaper and can be laid out on a south facing roof.

My thinking is that I could have two chambers in my tank, the lower one producing low grade heat from the EPDM panels, which is then bolstered by the main solar panel array.

If I could also take the warm water through a heat pump, I could make it really hot. This is a new house into which I have installed underfloor heating that runs at a much lower temperature (up to 40C or 104F). I aim to try to get about 10 tons of water in my underground tank up to, or hopefully higher than, this temperature in summer and then use it for winter heating.

As for a wind driven heat pump, development costs of the system proposed would be high. Better maybe to get an off the shelf turbine and charge lead acid batteries with the d/c current produced. Then, when this gets to a pre-defined charging level, invert it to a/c to run the heat pump in bursts. Maybe a bit inefficient but it is more than compensated for by the high efficency (3-400%, as indicated above)of the heat pump , plus the fact that the component technology and parts are already out there.

It seems to be a heck of a lot better than a friction source of heating, where parts will wear out. It is also maybe 10 times more efficient than pv panels which, as they stand, will never give payback.

Steve T

Unknown said...


Please don't forget about us as you proceed with your system. Also, it would be nice to know what your climate particulars are. Perhaps tell us a nearby city so we can look it up. I'll bet you don't get much snow. Bruce

Duane Tilden said...


Hi, I am a Mechanical Engineer who has been involved in the building services industry since 1990.

Firstly, I would like to say that I like your ideas, especially the roof mounted spinnarets. I currently am living in Grande Prairie, Alberta where we get significant wind year round, and attractive retrofits could be a feasible market, as well as new construction.

Heat pump systems are great, versatile with COP's of 3 to 6. They can provide both cooling, heating and are modular. Sometimes, depending on climate, we can use the outdoor air, in an water/air fluid cooler. Geological investigations must be performed to establish ground conditions for drilled or trenched geo-exchange systems.

One question I have, is rather than try to build a wind driven heat pump, why not use these ideas to provide electricity to the whole building. Depending on the loads and power capability, coupling a secondary power supply system, something an electrical engineer might have some idea about, then I think this would be a better usage of your proposal, and be more efficient to develop.

Duane M. Tilden, P.Eng

Joseph P. Reynolds said...

I like to keep things simple
The basic law of thermal dynamics states a compressed gas with a constant volume increases temperature.
This is the law that makes traditional heat pumps and refrigerators work.
Have you ever put your hand on the pipe that goes from the pump to the air storage tank of a compressor, that baby is hot.
VAWT can generate enough torque to run an air compressor.
You can improve the system by using refrigerants, such as a car ac system, but I like the idea of an open system using air. Air is still free, less of a pollutant, and the energy not transferred as heat is stored as compressed air to run pneumatic power tools.
Energy is always on my mind. My back ground is in physics, I work as a systems engineer and my wife owns a green house. On a sunny day in the winter a green house needs to be cooled and at night heated, we can go through 150 gallons of fuel oil in a week. Were I live we import large amounts of cold Canadian air off of Lake Ontario, high winter winds and even higher snow drifts.

Unknown said...

Joe, Isn't the big advantage of heat pumps their use of heat of fusion and not just pressure vs. temperature? Would just compressing air without phase change be any advantage over simple friction? One would need to pick a gas which would change phase under the conditions of a low rpm VAWT under a broad range of temps. Simple, no. That's where people smarter than me come in, like engineers! Bruce

Duane Tilden said...

I have been looking at the latest responses and it seems to me there is some confusion about this idea.

Firstly, heat pump technology, as pointed out achieves it's high COP's from the phase change. It is through the leveraging of the refrigerant phase change from a fluid to the gas phase where heat energy can be obtained from low temperature heat sources. This is how geothermal heat pumps can obtain heat energy from relatively low temp sources such as the ground where nominal ambient water temp would be at 55F and deliver hot water at temps of 90F to 140F.

Alternatively heat pumps can be used in air/air, air/water, water/air and water/water configurations. These are generally stand alone devices where in a properly engineered installation do not require supplemental heat sources.

Wind energy is a separate sustainable, environmentally friendly application. In my opinion the OP's idea of using wind energy to move water around for a heat pump application is marginal and likely too capital intensive to realize any real benefit. Also, it is just too restrictive, in my opinion.

Wind energy converted directly to electricity, or other dedicated pumping applications where electricity is not available is best (water pumping up to a reservoir in agricultural or power generation schemes for example). There also may be some merit to the idea of storing the energy as compressed air, but the amount of heat generated would not be significant, usable heat source. Try heating your home with a candle.

Electricity is used by a wide range of applications, so why not use the wind energy to best effectiveness? The operation of the compressor in the heat pump and the pumps to run the water loop(s) require electricity, so do common home appliances.

There may be some applications where the proffered idea would make sense, but not likely widely applicable for single family residences unless you have a large property and money to burn.

Unknown said...

Geothermal power plants drill holes into this heated rock to capture this naturally created steam and then use the steam to drive a traditional turbine/generator system to create electricity. Geothermal fluid temperatures should be at least 300 degrees Fahrenheit, although geothermal plants are operating on fluid temperatures as low as 210 degrees Fahrenheit.

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Unknown said...

Heat pumps are machines that can take heat from one place and then deliver that heat to another place at a higher temperature. Your home refrigerator is similar to a heat pump.

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Unknown said...

Hi All,

Have just come accross this post as I too had the same idea, I think the more efficient way of doing this would be to find a suitable refrigerant compressor pump that could be mechanically driven directly by the wind turbine. something along the lines of those used by chiller trucks that have a stand alone diesel engine driven cooling unit. the rest of the system would be similar to standard air source or ground source heat pumps. will obviously only work when its windy but used as a supplemental should provide savings.


Joseph P. Reynolds said...

It is true if the fluid goes through a phase change, the heat pump will be more efficient, but the cost of air is a lot less than a Freon type fluid.

if you have an air compressor you can feel the large amount of heat in the pipe just before the storage tank.

It is true that storing energy as compressed air is inefficient compared to electricity. The concept is to generate heat directly vice create electricity then heat. The stored compressed air is a beneficial bi-product of the heating system.

demotutorial said...

Hi David: Is it true that using heat transfer could easily save you 40% or more on your home energy expenses?

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Nulabert said...

Steve T,

Just wondering if you built your water storage tanks in the ground and how did the system work out?


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brian said...

I built a wind driven heat pump simulation test rig in 2002 for my final year project at university of limerick. Still have it is a cool thing. But only a test rig.

There are some problem like all good ideas.

1 wind speed change rapidly. To keep the turbine efficient you need to change the speed of the turbine. causing the pump to change speed. this cause the pressure in the heat pump circuit to drop. There is a valve you can adjust but i dose not like quick adjustment in the range need for heat pump.

There is currently a german company developing a wind driven heat pump in the range of 1 to 10 kw. The use a HAWT shaft to ground and heat pump on the flower.

This is all grate fun? but, the problem is small wind turbine do not pay for them selves. (depending on where you are but at 19 cent/kwh will not give a pay back here in the winde ireland).

if you check out how much your heat cost you will find it is far less maybe 5 Cent/ kwh. So you make four time more heat with a heat pump.(if you are looke).

I have battled away in this area for 8 years know and know work in a university here in ireland. I have a test site for over 7 years with some of the above technologies. I implemented and designed software for the development of a large 4 MW wind 2.1MW CHP and 6MW factory here in ireland and currently build controls to consume as much power on site as possible.

If there is interested parties in working in this are it can be a bit bleek and hard to get time. It is grate to chat these thing though and hopefully some day we will have live with out electricity? electricity is not inefficient but power plants are.

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Unknown said...

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