Wind mill for heat pump

[Pierre159]

Hello all,

i have listen some heat pump can use a windmill for turning the compressor. do you have some link?
thanks in advance

[Adriaan Kragten]

Heat pumps are normally grid connected. So if you have a grid connected wind turbine, all the energy from the wind turbine goes directly into the compressor motor of the heat pump as long as the compressor motor is consuming less power than the generated power of the wind turbine. Power fluctuations of the wind turbine are absorbed or supplied by the grid. But this is only true if the grid is availble. If the grid falls off, the wind turbine must be shut down automatically to prevent that there is a certain voltage on the grid which makes it unsafe for people to repair the grid. The same counts for grid connected solar panels. So this system normally doesn't work without a grid.

If there is no grid, you have several options. Theoretically it is possible to use the mechanical power of the wind turbine to directly drive the compressor but as a wind turbine has a very fluctuating output, this would also result in a very fluctuating rotational speed of the compressor and a very fluctuating heat supply of the heat pump. I have never heard that this has been done in practice.

It is also possible to make that the wind turbine generates heat and to use the heat directly for heating of the house. This has been done in Denmark in the past using a vertical shaft in the tower and a water brake. However, this system has as main disadvantage that you get even less heat than the mechanical power generated by the wind turbine. If you use a heat pump, you get about a factor 4 more heat than the electrical power needed for the compressor motor. I have described several ways how to use a wind turbine for heating in my public Dutch report KD 709. Normally my KD-reports are in English but this report is in Dutch because it was my contribution to the Dutch discussion about the energy transition.

[Pierre159]

Hello adriaan,
Yes i was thinking to use the mecanical power to drive the compressor. i understand it's can be fluctuant but free...
no one have try this? i was thinking heard something like this on this forum...

[SparWeb]

I have seen many examples of pumping water from a well with wind.
I do not think a heat pump can work that way at all.

[Pierre159]

Thank you adriaan, i have read your report KD709, really intresting
and the 46 pole generator driven by a 6 m windmill for a heat pump is really, in the idea it's near i'm intresting to make.
does it exist heat pomp driven by windmill wich produce electricity and wich accept variation in voltage? and direct voltage  from a windmill?

[mab]

The air-con compressor on a car has to cope with a wide range of speeds - it may be possible to drive one directly with a windmill, but it would normally have a pressure switch to stop the compressor if the high pressure circuit reaches it's limit - and that would un-load your windmill.

Also you would be generating your heat (or cold) near the windmill - i can't help thinking that electricity is easier to transmit to the house - unless your mill in attached to the house.

[Adriaan Kragten]

Thank you adriaan, i have read your report KD709, really intresting
and the 46 pole generator driven by a 6 m windmill for a heat pump is really, in the idea it's near i'm intresting to make.
does it exist heat pomp driven by windmill wich produce electricity and wich accept variation in voltage? and direct voltage  from a windmill?

So you can read Dutch or a translation program has given you enough information.

The 46-pole generator was used in combination with the VIRYA-6.5 which has a rotor diameter of 6.5 m. Information about this windmill is given in the three KD-reports KD 578, KD 579 and KD 624. I think that an electrical connection in between the generator and the asynchronous motor which drives a pump motor or the motor of another load is a better choice than a mechanical or a hydraulic coupling. The big advantage of a so called electrical shaft is that there can be a large distance in between the generator and the motor. Another advantage is that you get a kind of accelerating gear ratio if you go from a high pole number in the generator to a low pole number in the motor. It is true that you have efficiency loss in the generator and the motor but a mechanical or a hydraulical transmission also has losses. An extra disadvantige of a rotating shaft in the centre of the tower is that this shaft has a reaction torque on the head and this torque has an influence on the safety system of the wind turbine if the safety system turns the head out of the wind at high wind speeds.

A centrifugal pump accepts a rather large variation of the rotational speed but there is a certain low rotational speed for which only the static head can be supplied. Below this rotational speed, the pump torque decreases strongly and the output is zero. So it isn't a problem if the generator and the pump motor are connected permanently. A compressor will have a totally different Q-n characteristic than a centrifugal pump. I expect that the torque is about constant for every rotational speed if a certain pressure has to be produced. This means that the compressor motor has to be disconnected from the PM-generator of the wind turbine below a certain rotational speed but this isn't very difficult to realize. This disconnection makes that the rotor of the wind turbine starts unloaded and that the connection is only made when the rotor torque is high. But standard heat pumps are designed for a constant motor voltage and frequency and I doubt if they can work properly at varying rotational speeds. Some serious laboraty tests are needed first to check if this is possible untill you do this in combination with a wind turbine.

[Astro]

The air-con compressor on a car has to cope with a wide range of speeds - it may be possible to drive one directly with a windmill, but it would normally have a pressure switch to stop the compressor if the high pressure circuit reaches it's limit - and that would un-load your windmill.

Also you would be generating your heat (or cold) near the windmill - i can't help thinking that electricity is easier to transmit to the house - unless your mill in attached to the house.

 Somehow you have to narrow down the varying speeds. The reason Adrian had good luck with a 46 pole is because it kind of does that. More poles means a more steady output. Mainly because more pole equals a bigger machine that is less affected by small wind changes. You could build a tiny one with tiny little mags, but your amp output is going to be low due to winding wire size and it is going to change speeds easy. Both of which are not going to be good for a more constant supply of higher amperage usage. (which heating is going to require)
 As you said clutch of some kind, be it mechanical or otherwise would also help.
If it is heat and not cooling, a guy would be better off trying to heat veg oil, as it heats up faster and with less energy than water. It is about the safest thing to heat up outside of a very controlled situation.
That said with costs and everything figured in, off the top of my head, I would say to heck with a high pole count generator as that is going to get expensive. To heck with a clutch, as that is going to add cost. I would attempt to build the highest amp output generator I could. In another thread, someone was making blades for one that is charging at 40-60 amps. Then I would make a heat exchanger, I would do nothing with the mill but heat veg oil (in the summer you could always run the power through a charge controller) and have the veg oil heat the water/glycol mix being used for heating. You might have to add a couple controls but nothing major, to get the mill to stay spinning, as it is going to be in a constant state of wanting to stall due to the resistive load of a heating element. As I said in another thread, something simple like a high/low voltage (because voltage and amperage are tied together) relay that lets the mill spin up to a point, then applies the load until it slows down to an rpm that is no longer conducive to what you are trying to do, then cuts the load loose until the mill spins back up again.
 That would be my first attempt anyway. Simple and cheap. I am sure you could make something more efficient, but it would be more expensive as well.
 The fact is heat is very inefficient to make from electricity. That is why we do not want our coils getting hot or our batteries getting hot, because it cuts into the efficiency. Guess what compressors make a lot of..... heat.

[Astro]

The air-con compressor on a car has to cope with a wide range of speeds - it may be possible to drive one directly with a windmill, but it would normally have a pressure switch to stop the compressor if the high pressure circuit reaches it's limit - and that would un-load your windmill.

Also you would be generating your heat (or cold) near the windmill - i can't help thinking that electricity is easier to transmit to the house - unless your mill in attached to the house.

 Somehow you have to narrow down the varying speeds. The reason Adrian had good luck with a 46 pole is because it kind of does that. More poles means a more steady output. Mainly because more pole equals a bigger machine that is less affected by small wind changes. You could build a tiny one with tiny little mags, but your amp output is going to be low due to winding wire size and it is going to change speeds easy. Both of which are not going to be good for a more constant supply of higher amperage usage. (which heating is going to require)
 As you said clutch of some kind, be it mechanical or otherwise would also help.
If it is heat and not cooling, a guy would be better off trying to heat veg oil, as it heats up faster and with less energy than water. It is about the safest thing to heat up outside of a very controlled situation.
That said with costs and everything figured in, off the top of my head, I would say to heck with a high pole count generator as that is going to get expensive. To heck with a clutch, as that is going to add cost. I would attempt to build the highest amp output generator I could. In another thread, someone was making blades for one that is charging at 40-60 amps. Then I would make a heat exchanger, I would do nothing with the mill but heat veg oil (in the summer you could always run the power through a charge controller) and have the veg oil heat the water/glycol mix being used for heating. You might have to add a couple controls but nothing major, to get the mill to stay spinning, as it is going to be in a constant state of wanting to stall due to the resistive load of a heating element. As I said in another thread, something simple like a high/low voltage (because voltage and amperage are tied together) relay that lets the mill spin up to a point, then applies the load until it slows down to an rpm that is no longer conducive to what you are trying to do, then cuts the load loose until the mill spins back up again.
 That would be my first attempt anyway. Simple and cheap. I am sure you could make something more efficient, but it would be more expensive as well.
 The fact is heat is very inefficient to make from electricity. That is why we do not want our coils getting hot or our batteries getting hot, because it cuts into the efficiency. Guess what compressors make a lot of..... heat.

 Now I in no way am saying to do this, learn about this or attempt this, but ammonia has so pretty cool things about it when it is heated and cooled.

[Adriaan Kragten]

If you can read Dutch, there might be another report which I wrote recently and which might interest you. This is the report: "Ideeën over de realisatie van dertien huizen geschikt voor dubbele bewoning in Boskant" (Ideas about the realization of thirteen houses which can be used by two families in Boskant). This report can be copied for free from my website at the menu: No wind energy.

The plan could be realized on my property if the municipality would have interest (which they don't have). Each house has a big roof with 44, 300 W peak solar panels but in December this isn't enough to power the heat pump as only about 2 % of the yearly output is generated in December. So in chapter 7 of this report I have added one windturbine of EAZ-wind in the north-west corner of the plan. This wind turbine has a rotor diameter of 13.2 m and supplies enough power in December for the heat pumps of all thirteen houses if the houses are well isolated.

[Pierre159]

for Adriaan, i will check your report"Ideeën over de realisatie van dertien huizen geschikt voor dubbele bewoning in Boskant" but i don't think it will be possible for me.
the problem is that i still wind but low wind,
the medium of my wind on my site from 15 november to 15 february 2021, the period that we need heat because no sun on solar panel, was 5.2 m/s. every day i have 2 to 3 m/s
i don' t think an heavy rotor like a 6.5/ 9 and more could make something in my condition. i'm agree it big rotor like you study are effective with bigger wind.
Now know that all the energies will come more and more expensive. some of our reflexions wich are not the most profitable at he momment as we speak will very profitable in 3/4 year. and there is only the profitability there is the autonomy...

For my low wind does itclever to use smaller rotor/design? wich model of windmill could perform the best in my low wind?
if the model have enough torque we can tought to use a gearbox to have enough rpm for the generator.
even if some model are more expensive to build than a 3 blade, some are only one  solution reach the objective.

For astro: "In another thread, someone was making blades for one that is charging at 40-60 amps. Then I would make a heat exchanger, I would do nothing with the mill but heat veg oil (in the summer you could always run the power through a charge controller) and have the veg oil heat the water/glycol mix being used for heating. You might have to add a couple controls but nothing major, to get the mill to stay spinning, as it is going to be in a constant state of wanting to stall due to the resistive load of a heating element. As I said in another thread, something simple like a high/low voltage (because voltage and amperage are tied together) relay that lets the mill spin up to a point, then applies the load until it slows down to an rpm that is no longer conducive to what you are trying to do, then cuts the load loose until the mill spins back up again."
 
i don't see what you want to make, you have link or video?

thanks to all

[Astro]

for Adriaan, i will check your report"Ideeën over de realisatie van dertien huizen geschikt voor dubbele bewoning in Boskant" but i don't think it will be possible for me.
the problem is that i still wind but low wind,
the medium of my wind on my site from 15 november to 15 february 2021, the period that we need heat because no sun on solar panel, was 5.2 m/s. every day i have 2 to 3 m/s
i don' t think an heavy rotor like a 6.5/ 9 and more could make something in my condition. i'm agree it big rotor like you study are effective with bigger wind.
Now know that all the energies will come more and more expensive. some of our reflexions wich are not the most profitable at he momment as we speak will very profitable in 3/4 year. and there is only the profitability there is the autonomy...

For my low wind does itclever to use smaller rotor/design? wich model of windmill could perform the best in my low wind?
if the model have enough torque we can tought to use a gearbox to have enough rpm for the generator.
even if some model are more expensive to build than a 3 blade, some are only one  solution reach the objective.

For astro: "In another thread, someone was making blades for one that is charging at 40-60 amps. Then I would make a heat exchanger, I would do nothing with the mill but heat veg oil (in the summer you could always run the power through a charge controller) and have the veg oil heat the water/glycol mix being used for heating. You might have to add a couple controls but nothing major, to get the mill to stay spinning, as it is going to be in a constant state of wanting to stall due to the resistive load of a heating element. As I said in another thread, something simple like a high/low voltage (because voltage and amperage are tied together) relay that lets the mill spin up to a point, then applies the load until it slows down to an rpm that is no longer conducive to what you are trying to do, then cuts the load loose until the mill spins back up again."
 
i don't see what you want to make, you have link or video?

thanks to all

 With low wind conditions, you have 2 options. Go big. Think of the great big wind mills or even the old great big Dutch wind mills. Or go with many small wind mills.
 Again the fact is, making heat from electricity is not efficient. Heat is actually almost the enemy of making and using electricity.
 As for what I was describing, imagine a oil filled tank inside of a larger tank.
 I finally got off my butt and started to build, because I did not like how much my electric bill was in the summer, when my air was running. I thought long and hard about how to get that air conditioning load off of my monthly bill. Problem #1 is that it draws a good amount of electricity. Problem 2 is that it starts and stops a lot, so I have a high start up current. Those 2 things means EVERY item must be over sized, from wire to the generator to the charge controller. Everything. That gets expensive.
 Compressors use lots of electricity and make lots of heat. This is why they have had a big push in the last 10 years to make them more efficient. Some simple math tells me that I can get a heat pump/ac unit that requires 6 300 watt solar panels. The heat pump/ac cools at about 13,000 btu. I have a 3 ton (36,000 btu) central air unit and it cools my home. So I am going to need 20 or so 300 watt panels to cool my home. WOW!! Like I said  there has been a push to make compressors more efficient. However, these new compressors do not last as long and will need replaced more often. A bad deal, within 2-5 years. One that lasts longer, 10-12 years.
SO again compressors are not efficient. Neither is making heat from electricity.
But if one must, one must and then one must figure out the most efficient way to do it.
 
 

[Astro]

 In the end if you want a heat pump and you want to run it from a wind mill. Do a internet search for DC powered heat pump. Figure out how many watts/amps it takes and put up enough wind power (plus some for losses and such) to power it.
You are still going to need to make it so it does not run when there is not enough wind to produce enough power, or you will harm the compressor.
You are also going to need to protect it from over voltage in case you get a bunch of wind.
SO during times of a little to much or to little wind, your wind system is not going to be doing anything. BUT it has to do something in to much wind, so a dump load.
 That does not sound all that efficient. When you could use 1-2 amps or 70 amps or whatever is available to heat oil in a heat exchanger. SO no matter what the wind does, it is always heating, if only a little.

[Adriaan Kragten]

The calculations which I have made in my report about the thirteen houses are for my village Boskant (near Sint-Oedenrode in the south-east part of The Netherlands). The average yearly wind speed in Boskant is rather low and about 4 m/s at a height of 10 m in open terrain. As there is more wind in the winter than in the summer, the average wind speed during December, January and February is higher; I assumed 5 m/s at a height of 10 m in open terrain. It is assumed that the wind turbine of EAZ-wind has a tower height of 24 m but that there are about 12 m high trees around the wind turbine. But the average wind speed during the three winter months will still be higher than 5 m/s; I assumed 5.5 m.s. The power for a certain average wind speed is larger than for a certain constant wind speed because the power increases with the cube of the wind speed. So it was assumed that the Pel-V curve of the wind turbine could be read at V = 6 m/s. For this wind speed, the power is 6827 W (see figure 5). So every house receives 525 W. This is more than the average need of the heat pump motor which is about 450 W in December. If the heat pump has a COP of 4, the heat power which is produced is 1800 W and this is about the power loss for a very well isolated house (see chapter 6).

This calculation shows that even for areas with rather low average wind speeds, a wind turbine is a good choice. If you have an individual wind turbine for each house, a rotor diameter of 5 m should be enough but you need a tower with a height of at least 12 m and may be even more if there are trees around. The wind speed at hub height during the three winter months should be that high that the Pel-v curve of the wind turbine can be read at a wind speed of 5 m/s.

Calculations for a grid connected wind turbine with a rotor diameter of 5 m (the VIRYA-5B3) using an axial flux PM-generator of Hefei Top Grand are given in my public report KD 710. The estimated Pel-V curve is given in figure 8. In this figure it can be read that Pel = 506 W for V = 5 m/s. So this is enough if the needed electrical power of the heat pump is 450 W.

[Astro]

The calculations which I have made in my report about the thirteen houses are for my village Boskant (near Sint-Oedenrode in the south-east part of The Netherlands). The average yearly wind speed in Boskant is rather low and about 4 m/s at a height of 10 m in open terrain. As there is more wind in the winter than in the summer, the average wind speed during December, January and February is higher; I assumed 5 m/s at a height of 10 m in open terrain. It is assumed that the wind turbine of EAZ-wind has a tower height of 24 m but that there are about 12 m high trees around the wind turbine. But the average wind speed during the three winter months will still be higher than 5 m/s; I assumed 5.5 m.s. The power for a certain average wind speed is larger than for a certain constant wind speed because the power increases with the cube of the wind speed. So it was assumed that the Pel-V curve of the wind turbine could be read at V = 6 m/s. For this wind speed, the power is 6827 W (see figure 5). So every house receives 525 W. This is more than the average need of the heat pump motor which is about 450 W in December. If the heat pump has a COP of 4, the heat power which is produced is 1800 W and this is about the power loss for a very well isolated house (see chapter 6).

This calculation shows that even for areas with rather low average wind speeds, a wind turbine is a good choice. If you have an individual wind turbine for each house, a rotor diameter of 5 m should be enough but you need a tower with a height of at least 12 m and may be even more if there are trees around. The wind speed at hub height during the three winter months should be that high that the Pel-v curve of the wind turbine can be read at a wind speed of 5 m/s.

 Are you talking a geo thermal pump? Because making much heat from 4 amps (120v), 500 watts, is going to be tough. A refrigerator compressor draws 3 amps.
 On a side note, look at the wind here today. ( I went to town to stock up on a few things and I bet it is stronger then that. It is blowing pretty strong)

[Pierre159]

For adriaan,

a tower of 12 is a bit difficult to make in autoconstruction, and due to the local legislation 12m is the total of the height of the windmill with rotor inclusive.


on my registration on the wind from 15 november to 15 frebruary
7 days on 10 have wind beetwen 2 to 3m/s
2 days on 10 have wind more 5m/s
1 days on 10 have wind more 6m/s

having a windmill to see it turn 3 days on 10 is a problem and more if we expect to heat...

[Adriaan Kragten]

To Astro. I am talking about a normal modern heat pump. For a heat pump we don't talk about the efficiency as an efficiency higher than 100 % isn't possible but we talk about the COP-value. Modern heat pumps realize a COP-value of more than 4 if the input temperature of the medium from which the heat is extracted is about 0 °C and if the temperature of the water which is used for heating is about 30 °C.

So it might seem strange but for a COP of 4 you get four times more heat power than the electrical power which is going into the compressor motor. The input medium can be water or air. If you extract energy from the input medium, the temperature of the input medium is reduced some degrees. So this reduction of the temperature of the input medium supplies the power and this power is much higher than the power needed to drive the compressor. The COP-value is higher if the temperature of the input medium is higher and if the temperature of the water which heats the house is lower. As the output water temperature for a high COP is rather low, you need a large area of the heaters and therefore heat pumps are normally used in combination with floor heating which has a large area if compared to normal radiators.

So a heat pump is always very much better than direct transformation of electricity in to heat by using a resistor.

[Adriaan Kragten]

For adriaan,

a tower of 12 is a bit difficult to make in autoconstruction, and due to the local legislation 12m is the total of the height of the windmill with rotor inclusive.


on my registration on the wind from 15 november to 15 frebruary
7 days on 10 have wind beetwen 2 to 3m/s
2 days on 10 have wind more 5m/s
1 days on 10 have wind more 6m/s

having a windmill to see it turn 3 days on 10 is a problem and more if we expect to heat...

If the maximum height of rotor plus tower is 12 m and if the rotor has a diameter of 5 m, it means that the centre of the rotor is at a height of 9.5 m. You will get only enough power at this height in areas with low average wind speeds if there are no trees or buildings which reduce the wind speed for the prevailing wind direction. So I agree that a tower height of 9.5 m may be too low for your wind regime. But a maximum total height of 12 m is very low. You should try to increase this up to at least 12 m hub height. On my property some of the trees have a height of 15 m. So I have experienced that my 12 m tower of the former VIRYA-4.2 was too low for certain wind directions.

[Pierre159]

i will never have autorisation to rise higher than 12m, in your opinion does some models/shape HAWT or VAWT could be more efficient for my condition?
at the momment i have made a prototype of a 1.2m diameter 1m high Lenz 2.
unloaded it start at 2 m/s easily
with my mesurement of last week i was having 55 rpm at 2.8 m/s unloaded
i don't know if it's the best option
but this 1.2 diam i'm far that i need

[Adriaan Kragten]

i will never have autorisation to rise higher than 12m, in your opinion does some models/shape HAWT or VAWT could be more efficient for my condition?
at the momment i have made a prototype of a 1.2m diameter 1m high Lenz 2.
unloaded it start at 2 m/s easily
with my mesurement of last week i was having 55 rpm at 2.8 m/s unloaded
i don't know if it's the best option
but this 1.2 diam i'm far that i need

A rotor diameter of 1.2 m is nothing if you want power to drive the motor of the compressor of a heat pump. Look at figure 8 of my report KD 710 and then you can see what you can expect from a wind turbine with a rotor diameter of 5 m.

[Pierre159]

I know 1.20 is average nothing it was for experience
i check the KD 710 fig 8
do you think 2 windmill 2.5m rotor is equal to 1 of 5m ?
(2 can have a better starting point)

[JW]

sorry to interrupt,

What is the main purpose of the heat-pump, what are the expected output, loads water heating, climate control, refrigeration etc.
 I think if you focus on the "load" you can do it better without the heat-pump. Its not like to power a lightbulb. 

[JW]

To power a compressor is kind of vague

[Pierre159]

due to fact it's have not been made ,the question what heat pump can a windmill is abble to drive

[JW]

well it should have a rating such as foot-pounds torque to rpm. It can be measured by a dynamometer.

Again, what is the end use of the heat-pump?   

[Astro]

To power a compressor is kind of vague

Exactly.  I also agree with "I think if you focus on the "load" you can do it better without the heat-pump.".
 

[JW]

Yes... as a Thermodynamicist

I understand that a heat-pump is actually a refrigeration system run backwards, so that the evaporator gets hot and condenser gets cold. It has its limits on a really cold conditions. Then a AUX heater has to take over.

But none of this has any compressor requirement, since this is on the (main) refrigeration system involved. its a two way system.

We cannot give you the answer you seek, without the actual existing system which is tuned by a baseline existing refrigeration cycle and the existing compressor required are same in both systems... It will be equal for both uses./ 

[Pierre159]

the final use of the heat pump is to heat the house during our cold period in nothern europe when there is no sun for the solar panel.
the first idea is to produce heat with a windmill not mather if it is by mechanical way or other but the more efficient way for a low wind like i have

[Astro]

the final use of the heat pump is to heat the house during our cold period in nothern europe when there is no sun for the solar panel.
the first idea is to produce heat with a windmill not mather if it is by mechanical way or other but the more efficient way for a low wind like i have

 In the end, with low wind, you are going to need many small windmills or a very large one.
For example a 10kw wind turbine that has a cut in speed at 2 m/s can produce about 3160kwh per year. At 3 m/s it can produce 8257 kwh per year. A 20 kw can produce 4080 kwh in 2 m/s per year and at 3 m/s 10700 kwh per year.
A 20 kw has a radius of about 10 meters.
 That is not a lot of power over a year and you said you do can not have one that high uo.
I did come across a vawt that looked like it might help do what you are trying to do, it was rather large. I think it was about the size of an suv. So there are people trying to make them. I can not remember where I saw it or the name of it. I am not even sure if it went into production as what I saw was more of a prototype, but it looked like it should work. I have no idea what the company was charging for such a unit.
 Sometimes the answer is not what we think it should be. If you look around and pay attention though, you can almost always find a way. I am sure there is a way to help heat your home, but I do not know the area or really anything about it, so I really can not say what that answer is. There are many topics on this site, from wind and solar to water and steam (which is why I like it here). So there is something that will work for your situation, you just have to figure out what the good Lord is providing you. Me? I watch the wind blow and all I can see is dollar bills flying by the window. That kind of tells me, that the good Lord is providing wind and maybe I should not ignore a gift from above.

[Pierre159]

thank you to all for your answer my fist was question was about a heat because i was thinking it was the best way to produce heat for a house.
but after some of your comments i'm not sure it's the best to use a heat pump.
does some of you have some ideas?

due to my low wind to you think a vawt is more suitable?

[Adriaan Kragten]

I know 1.20 is average nothing it was for experience
i check the KD 710 fig 8
do you think 2 windmill 2.5m rotor is equal to 1 of 5m ?
(2 can have a better starting point)

The generated power for a certain wind speed is proportional to the rotor area (see formulas given in chapter 4.1 of report KD 35). So you need four and not two rotors of 2.5 m diameter to get the same area as for one rotor of 5 m diameter. But even if the total area is the same, a wind turbine with a rotor diameter of 5 m will produce more power at the same wind speed because the Reynolds value of the airfoil is higher which results in a lower drag/lift ratio and therefore in a higher maximum Cp (see KD 35 chapter 3 and chapter 4.3.3). The generator efficiency also increases if the generator is bigger. So there is no reason why small is better than big in terms of output at the same wind speed.

There is another very important aspect which favors big rotors and that is the tower height. If you need an 18 m tower to come above the trees to get a sufficiently high wind speed, this tower is relatively expensive for a rotor diameter of 2.5 m but it is relatively cheap for a rotor diameter of 5 m. So generally rotors with a diameter of 2.5 m have towers of maximal 12 m but an 18 m tower for a rotor with a diameter of 5 m isn't a strange choice. But the wind speed increases with the height and the power increases with the cube of the wind speed. So the increase of the output per square meter rotor area is much higher for a big wind turbines than for a small wind turbine because of the higher tower. This is the main reason why the costs to generate 1 kWh for a big wind turbine is much lower than for a small wind turbine.

[Adriaan Kragten]

thank you to all for your answer my fist was question was about a heat because i was thinking it was the best way to produce heat for a house.
but after some of your comments i'm not sure it's the best to use a heat pump.
does some of you have some ideas?

due to my low wind to you think a vawt is more suitable?

Any VAWT is worse than a well designed HAWT in low and in high wind speeds. I have written several KD-reports about different types of VAWT's to explain this statement. These reports are specified in the note: "Sequence of KD-reports for self-study" which you find at the top of the menu KD-reports.

It depends on where your house is situated but burning wood might be an option if you have no close neighbours. Wood is concentrated solar energy. It can be harvested and stored during the year and used when needed. But you need a sufficient large area if you want to grow your own wood. I have planted many trees fourty years ago and now I have enough wood for the rest of my live.

[Astro]

thank you to all for your answer my fist was question was about a heat because i was thinking it was the best way to produce heat for a house.
but after some of your comments i'm not sure it's the best to use a heat pump.
does some of you have some ideas?

due to my low wind to you think a vawt is more suitable?

Any VAWT is worse than a well designed HAWT in low and in high wind speeds. I have written several KD-reports about different types of VAWT's to explain this statement. These reports are specified in the note: "Sequence of KD-reports for self-study" which you find at the top of the menu KD-reports.

It depends on where your house is situated but burning wood might be an option if you have no close neighbours. Wood is concentrated solar energy. It can be harvested and stored during the year and used when needed. But you need a sufficient large area if you want to grow your own wood. I have planted many trees fourty years ago and now I have enough wood for the rest of my live.

 Actually, several people have written about the fact a vawt is possibly better in low wind then a hawt. Are they less efficient?? Define the parameters.
 If you are saying that in 20 mph winds or 15 mph winds, that a hawt can outperform a vawt, I would say you are correct. By the math, given exactly what is needed, a hawt does very well. It does very well on a large scale in many different situations and wind speeds. I know I watch them spin round and round every day.
 But last I checked there are not very many people on here putting up million plus dollar machines.
The reason so little was ever spent on the vawt concept is because......... there is no money in it. It is not suitable for large scale. Like I said do not go thinking the government or big business is going to do anything to help you or I. NOW if they can make money off it... they will do it.
 Again, it is not suitable for wind fields.
However that does not mean it is not better in certain areas. That is the way it works, that is what I said about paying attention to what the good Lord provides. He takes away in some areas and gives in others. If there is not a scientific name for that, there should be. A fish will lose a climbing test, every time, but put it in the water and see what happens. It is like Darwinism or something.
 So just because big money and the government did not make great big ones, I actually never heard them say that small ones do not work well. I mean come on....... think. If they didn't........... why would they have tried to make them bigger?
 Help a brother out here. I think we know why.
 So again it is my contention that vawts are very viable on a smaller scale.