Author Topic: Wind mill for heat pump  (Read 3908 times)

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Adriaan Kragten

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Re: Wind mill for heat pump
« Reply #33 on: February 11, 2022, 04:07:17 AM »
Read my reports about VAWT's. All KD-reports which I have written about VAWT's are specified in point 3 of the note: "Sequence of KD-reports for self-study" which you can find on the top of the menu KD-reports at my website www.kdwindturbines.nl. You can agree with me or you can't agree with me. If you don't agree, build your own VAWT and meet all disadvantages in practice. I wont spend my time on this forum in discussions about VAWT's.
« Last Edit: February 11, 2022, 04:22:41 AM by Adriaan Kragten »

Artful Bodger

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Re: Wind mill for heat pump
« Reply #34 on: February 11, 2022, 08:57:02 AM »
but after some of your comments i'm not sure it's the best to use a heat pump.
A heat pump is almost certainly the best way to heat your house. In France our electricity is largely CO2 free, so electricity is the most environmentally sensitive option. Using a heat pump will give say 3-5kW of heat for every 1kW of energy bought. Using gas, oil, wood or pellets to heat your house will always cost more, unless you have a lot of trees like Adriaan!
How are you currently heating the house?  Add up all the electric heaters or the tell us the boiler size. That will help determine the wind turbine size. If I read the regulations correctly you can have any number of turbines less the 12m tall. https://www.demarches.interieur.gouv.fr/professionnels/installation-eolienne-domestique-agricole - In French

I'm curious why you have no solar PV in winter. Do you live in a valley, or just heavily shaded by trees?
2012 1.1kW PV + SMA SB1700. 2021 740W PV + 600W Hoymiles MI600

electrondady1

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Re: Wind mill for heat pump
« Reply #35 on: February 11, 2022, 09:22:48 AM »
the Chinese emerald ash beetle has killed all my ash trees so i will have a great deal of fire wood for years to come . dealing with wood is labor intensive so that is why our ancestors were happy to move on to other heat sources.
i build vertical mills and  was building 3 bladed drag mills but i now prefer squirrel cage designs because i find them most visually pleasing .
i was doing lots of experiments with wind powered electrolysis .
i like that the more the wind blows the more hydrogen (+ oxygen) i can produce and i can feed those gases into my fire.







Bruce S

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Re: Wind mill for heat pump
« Reply #36 on: February 11, 2022, 09:34:27 AM »
--- Begin Moderator Mode ---
Astro;
Couple things I see going on in your recent posts that are going outside the boundaries & rather than point them out I'm going to copy a link to the FAQs. Specifically the posting guidelines. Please read this ! It is important .

https://www.fieldlines.com/index.php/topic,150244.0.html

--- End Moderator Mode ---
Bruce S
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Pierre159

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Re: Wind mill for heat pump
« Reply #37 on: February 11, 2022, 01:13:20 PM »
 if i tell that i build a 5m in you opininon wich HAWT could fit the best my low wind  (start 2/2.5 m/s)
if choose a 5m vawt wich is best option a squirel cage, savonius, ...?

JW

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Re: Wind mill for heat pump
« Reply #38 on: February 11, 2022, 05:50:05 PM »
Ok check this out :)

Research   TSR

you will find what your looking for there-

Its a pretty dynamic variable.

Astro

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Re: Wind mill for heat pump
« Reply #39 on: February 11, 2022, 11:19:33 PM »
--- Begin Moderator Mode ---
Astro;
Couple things I see going on in your recent posts that are going outside the boundaries & rather than point them out I'm going to copy a link to the FAQs. Specifically the posting guidelines. Please read this ! It is important .

https://www.fieldlines.com/index.php/topic,150244.0.html

--- End Moderator Mode ---
Bruce S

Sorry. Here is an interesting article that says what I was trying to say.
https://www.asme.org/topics-resources/content/vertical-axis-wind-turbines-work-well-together#:~:text=A%20single%20vertical%20turbine%20has,soon%20reach%2050%20as%20well).
« Last Edit: February 12, 2022, 08:09:41 AM by Astro »

Adriaan Kragten

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Re: Wind mill for heat pump
« Reply #40 on: February 12, 2022, 03:43:14 AM »
A well designed HAWT can also start at low wind speeds if it is especially designed for low wind speeds. There are two important low wind speeds Vstart and Vcut-in. Vstart is the wind speed for which the rotor starts rotating. This is the wind speed for which the rotor torque becomes larger than the friction or clogging torque of the generator. Vcut-in is the wind speed for which power production starts. So this is the wind speed for which the Pel-V curve starts. For battery charging wind turbines Vcut-in is the wind speed for which the open DC voltage becomes equal to the open battery voltage. For grid connected wind turbines it is the wind speed for which the open DC voltage is the lowest voltage which is accepted by the inverter.

As the generated mechanical power of the rotor increases proportional to the cube of the wind speed, the availabel power at wind speeds below V = 3 m/s is very low so generally one is not going lower than Vcut-in = 3 m/s for battery charging wind turbines and Vcut-in = 2.5 m/s for grid connecting wind turbines. The 13.2 m diameter rotor of the wind turbine of EAZ-wind has a Vcut-in of 2.5 m/s. Another reason to go not lower than Vcut-in = 3 m/s for battery charging wind turbines is that you may get some little power at V = 2 m/s but the power at higher wind speeds will be less because of not optimal matching or because of a low generator efficiency.

If Vstart is higher than Vcut-in, there is hysteresis in the Pel-V curve. So idially, Vstart is lower or equal to Vcut-in. To get a low value of Vstart for a HAWT, one needs a rotor with a rather high starting torque coefficient and a generator with a low friction or clogging torque.
« Last Edit: February 12, 2022, 03:57:19 AM by Adriaan Kragten »

Pierre159

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Re: Wind mill for heat pump
« Reply #41 on: February 12, 2022, 04:19:32 PM »
i have work on wind  statistics of last winter
67% of my wind is between 2.05 m/s to 5.47 m/s
and
95% of my is between 0.8 m/s to 7.48 m/s

it give a better idea to chose a design



Pierre159

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Re: Wind mill for heat pump
« Reply #42 on: February 14, 2022, 03:30:54 AM »
in you opinion wich vawt or  hawt design is best for my wind ?

Adriaan Kragten

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Re: Wind mill for heat pump
« Reply #43 on: February 14, 2022, 07:00:30 AM »
You should make a wind speed distribution for the hub height with intervals of 1 m/s for the three winter months December, January and February. A wind speed distribution gives the number of hours that the wind is in between 0.5 and 1.5 m/s, in between 1.5 and 2.5 m/s, in between 2.5 and 3.5 m/s and so on. The wind speed should have been measured and averaged for very short periodes like 10 seconds. If you take the average of about 10 minutes, you can get a very different result. This wind speed distribution normally gives one interval with the highest number of hours. Assume this is the interval in between 4.5 and 5.5 m/s. So the average wind speed is 5 m/s for this interval. If this most important interval has an average wind speed lower than 4 m/s, I think that you can better forget wind energy.

Next you chose a certain wind turbine but you must have the Pel-V curve of that wind turbine. For all my HAWT's, I give the calculated Pel-V curves in the design reports but for most VAWT's reliable Pel-V curves are not available. If a Pel-V curve isn't availble, it is impossible to calculate the output for the three winter months. Assume that you chose the VIRYA-5B3 for which the Pel-V curve is given as figure 8 of my public report KD 710. This curve starts at V = 3 m/s. So you can read that Pel = 110 W at V = 3 m/s, 259 W at V = 4 m/s, 506 W at V = 5 m/s, 875 W at V = 6 m/s and so on. Next you multiply the power for a certain wind speed as read from the Pel-V curve with the number of hours of each interval for the same average wind speed and you find the energy generated for that wind speed interval in Whours. The total energy in the three winter months is the sum of the energy of all wind speed intervals.

What you find is the generated electrical energy. If all energy is supplied to a heat pump, you get about a factor four more heat energy depending on the COP-value of the heat pump. But you need a lot of heat even for a well isolated house and therefore you need a big wind turbine especially if the best wind speed interval is gained for a low wind speed. You should also make a calculation of the heat loss of your house to find out how much heat you really need. I expect that with a HAWT with a rotor diameter of 5 m and a tower height of a least 12 m you will get a good result for a well isolated house in a good wind regime. But such a large HAWT is out of the range to design and build by most amateurs. So you should find a grid connected windmill of this size which can be bought somewhere. I can't advise you which brand is best as this requires careful investigation of different brands.

But if you take a VAWT like a Savonious rotor with a Cp value which is less than half of that of a well designed HAWT, you need more than the double swept rotor area. So this results in a Savonious rotor with a diameter and height of about 7 m. For the same wind speed, this Savonious rotor should have a tower of about 8.5 m high. This Savonious rotor will be extremely heavy but also very dangerous as you can't limit the rotational speed at high wind speeds. May be now it will be clear why a Savonious rotor is only a reasonable option if you need only a very little power.

If you take a Darrieus rotor, the maximum Cp is about 0.35 but the required swept rotor area is still larger than for a well design VAWT. A H-Darrieus rotor needs a diameter and a height of about 5 m to get the same power as a HAWT with a rotor diameter of 5 m. But Darrieus rotors have a lot of disadvantages (see report KD 215). It might be possible to solve the starting problem (see KD 601) but the other disadvantages remain. A H-Darrieus rotor is very sensible to vibrations and it is also very difficult to limit the rotational speed and thrust at very high wind speeds. So you should forget this if you don't have the needed skills and money to solve all problems.
« Last Edit: February 14, 2022, 07:48:28 AM by Adriaan Kragten »

Bruce S

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Re: Wind mill for heat pump
« Reply #44 on: February 14, 2022, 09:48:15 AM »
Adriaan;
There are a few other factors that come into play with the "S" style of VAWTs, they are somewhat self-limiting with due to wind speeds. They are much slower and can easily be stopped with the same style of braking used for HAWTs. IF a person chooses to build one knowing that building either style that for the most part wind speed below ~3m/s really just does not have enough harvest-able energy to be anything but a test of building skills. Otherwise the mill of either type will need to be large. Down home, we have large water-pumping HAWTs they are specifically built for water pumping which means they are used for torque. Of the 3 still working and pumping from a well the "S" style handles this wonderfully.

I also remember the calcs you graciously posted being used much much more when ceramic magnets where used more.

Thanks again for the information it's still a great read!

Bruce S   
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Adriaan Kragten

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Re: Wind mill for heat pump
« Reply #45 on: February 14, 2022, 01:31:25 PM »
Adriaan;
There are a few other factors that come into play with the "S" style of VAWTs, they are somewhat self-limiting with due to wind speeds. They are much slower and can easily be stopped with the same style of braking used for HAWTs. IF a person chooses to build one knowing that building either style that for the most part wind speed below ~3m/s really just does not have enough harvest-able energy to be anything but a test of building skills. Otherwise the mill of either type will need to be large. Down home, we have large water-pumping HAWTs they are specifically built for water pumping which means they are used for torque. Of the 3 still working and pumping from a well the "S" style handles this wonderfully.

I also remember the calcs you graciously posted being used much much more when ceramic magnets where used more.

Thanks again for the information it's still a great read!

Bruce S

Why would a VAWT be self limiting the rotational speed? I see only one reason and that is blade flutter. If the blade is shaking that severe that the airfoil is stalling due to increased angles of attack, you get a strong increase of the drag and this reduces the increase of the rotational speed. But if the blade is shaking that much that the airfoil is stalling, it won't live long.

I have seen the effect of blade flutter for a rotor with tapered and cambered aluminium blades in the wind tunnel (see report KD 616). Flutter for a HAWT happens at a very special tip speed and results in very strong forwards and backwards movements of the blade combined with strong torsion fluctuations. These strong movements result in strong increased drag and this slows down the rotor untill the flutter stops. But then the blade accellerates again until flutter starts again. This happens at a constant speed of the wind tunnel. But if the wind speed is high enough, the flutter doesn't stop and a blade can be destroyed due to flutter within some minutes.

So if there is no flutter for a VAWT, the rotational speed will increase about proportional to the wind speed and there will be a high wind speed for which the whole rotor explodes due to too high centrifugal forces, due to a too high thrust or due to too high vibrations. A mechanical brake can reduce the maximum rotational speed but this brake can become very hot at high wind speeds. Braking is no safe way to reduce the rotational speed also because it is not working automatically. You should reduce the generated power by aerodynamics. For a HAWT you have two options, turning the rotor out of the wind or pitch control but for a VAWT these options are not possible. So to my opinion the idea of self limiting rotational speed of a VAWT is a fairy tail and therefore I see VAWT's as that dangerous that they should be forbidden.

Astro

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Re: Wind mill for heat pump
« Reply #46 on: February 14, 2022, 02:37:03 PM »
Adriaan;
There are a few other factors that come into play with the "S" style of VAWTs, they are somewhat self-limiting with due to wind speeds. They are much slower and can easily be stopped with the same style of braking used for HAWTs. IF a person chooses to build one knowing that building either style that for the most part wind speed below ~3m/s really just does not have enough harvest-able energy to be anything but a test of building skills. Otherwise the mill of either type will need to be large. Down home, we have large water-pumping HAWTs they are specifically built for water pumping which means they are used for torque. Of the 3 still working and pumping from a well the "S" style handles this wonderfully.

I also remember the calcs you graciously posted being used much much more when ceramic magnets where used more.

Thanks again for the information it's still a great read!

Bruce S

Why would a VAWT be self limiting the rotational speed? I see only one reason and that is blade flutter. If the blade is shaking that severe that the airfoil is stalling due to increased angles of attack, you get a strong increase of the drag and this reduces the increase of the rotational speed. But if the blade is shaking that much that the airfoil is stalling, it won't live long.

I have seen the effect of blade flutter for a rotor with tapered and cambered aluminium blades in the wind tunnel (see report KD 616). Flutter for a HAWT happens at a very special tip speed and results in very strong forwards and backwards movements of the blade combined with strong torsion fluctuations. These strong movements result in strong increased drag and this slows down the rotor untill the flutter stops. But then the blade accellerates again until flutter starts again. This happens at a constant speed of the wind tunnel. But if the wind speed is high enough, the flutter doesn't stop and a blade can be destroyed due to flutter within some minutes.

So if there is no flutter for a VAWT, the rotational speed will increase about proportional to the wind speed and there will be a high wind speed for which the whole rotor explodes due to too high centrifugal forces, due to a too high thrust or due to too high vibrations. A mechanical brake can reduce the maximum rotational speed but this brake can become very hot at high wind speeds. Braking is no safe way to reduce the rotational speed also because it is not working automatically. You should reduce the generated power by aerodynamics. For a HAWT you have two options, turning the rotor out of the wind or pitch control but for a VAWT these options are not possible. So to my opinion the idea of self limiting rotational speed of a VAWT is a fairy tail and therefore I see VAWT's as that dangerous that they should be forbidden.

 Don't tell these guys.
https://surfiran.com/still-working-windmills-iran/#:~:text=The%201%2C000%20year%20old%20windmills,to%2074%20miles%20an%20hour.

Pierre159

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Re: Wind mill for heat pump
« Reply #47 on: February 14, 2022, 03:43:10 PM »
Quote
Vous devez faire une distribution de la vitesse du vent pour la hauteur du moyeu avec des intervalles de 1 m/s pour les trois mois d'hiver décembre, janvier et février. Une distribution de la vitesse du vent donne le nombre d'heures pendant lesquelles le vent est entre 0,5 et 1,5 m/s, entre 1,5 et 2,5 m/s, entre 2,5 et 3,5 m/s et ainsi de suite. La vitesse du vent aurait dû être mesurée et moyennée sur de très courtes périodes comme 10 secondes. Si vous prenez la moyenne d'environ 10 minutes, vous pouvez obtenir un résultat très différent. Cette distribution de la vitesse du vent donne normalement un intervalle avec le plus grand nombre d'heures. Supposons qu'il s'agit de l'intervalle entre 4,5 et 5,5 m/s. La vitesse moyenne du vent est donc de 5 m/s pour cet intervalle. Si cet intervalle le plus important a une vitesse moyenne du vent inférieure à 4 m/s, je pense qu'il vaut mieux oublier l'énergie éolienne

i understand i would like to have these data but i don't see how to obtain it (i can't make it)

Bruce S what is style "S" VAWT, savonius?

there is no brake for savonius?

for the link post by astro (thank you) which cp can reach a rotor like this does it make for low or big wind?

JW

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Re: Wind mill for heat pump
« Reply #48 on: February 14, 2022, 09:23:55 PM »
God I hate this

"TSR"

Benz limit

Adriaan Kragten

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Re: Wind mill for heat pump
« Reply #49 on: February 15, 2022, 02:07:58 AM »
There is another effect that counts and that is the Reynolds number. The Reynolds number for a stationary blade is given by formula 3.4 in report KD 35 and for a rotating blade by formula 5.5 in KD 35. So the Reynolds number is increasing with the undisturbed wind speed V. A Darrieus rotor needs a symmetrical airfoil because the angle of attack is positive if the blade is at the front side of the rotor and negative if the blade is at the backside. Aerodynamic characteristics of the symmetrical NACA 0015 airfoil are given in figure 1 of report KD 601. In this figure it can be seen that the airfoil starts stalling at higher angles of attack if the Reynolds number is higher and that the Cd/Cl ratio is lower if the Reynolds number is higher. So a Darrieus rotor will have a higher maximum Cp if the wind speed is higher. But this is just opposite the self limiting effect! This positive effect of a high Reynolds number is valid for all wind turbines so also for other VAWT's and for HAWT's.

A Savonious rotor has an optimum tip speed ratio of about 0.9, so it will run at low rotational speeds if compared to a VAWT with a tip speed ratio of about 6 and the same rotor diameter. But the maximum Cq value of a Savonious rotor is rather high which means that the peak torque level is much higher at the same wind speed. So if you want to stop a Savoniuos rotor at high wind speeds with a mechanical brake, you need a very heavy brake.
« Last Edit: February 15, 2022, 02:18:59 AM by Adriaan Kragten »

Pierre159

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Re: Wind mill for heat pump
« Reply #50 on: February 15, 2022, 03:17:40 AM »
is the heavy brake is still in loaded on the turbine?
do you have a picture ?

MattM

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Re: Wind mill for heat pump
« Reply #51 on: February 15, 2022, 07:12:41 AM »
If you're going for a large HAWT for wintertime use there probably aren't many weather conditions where you would need to brake.  If the weather is going to turn that bad then why would you not block if off beforehand?  Winter storms tend to roll in for short enough durations, when it passes you could let it go again.  But severe winter storms also imply severe cold spells.  You might want direct heat rather than thermal pumping in those situations until the air warms up.

Adriaan Kragten

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Re: Wind mill for heat pump
« Reply #52 on: February 15, 2022, 07:49:38 AM »
is the heavy brake is still in loaded on the turbine?
do you have a picture ?

Mostly one uses a disk brake from a car or a motorcycle. The brake can be used by hand to stop the rotor completely. However, if the brake is used to limit the maximum rotational speed, it must be activated by a signal derived from the rotational speed and braking must be that hard that the maximum rotational speed is maintained. Technically this is possible but it requires acurate regulation of the braking torque. A lot of heat can be generated in the brake if the rotor continues rotating. There will also be substantial wear of the brake pads and the disk in windy areas.

Mary B

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Re: Wind mill for heat pump
« Reply #53 on: February 15, 2022, 12:21:26 PM »
is the heavy brake is still in loaded on the turbine?
do you have a picture ?

Mostly one uses a disk brake from a car or a motorcycle. The brake can be used by hand to stop the rotor completely. However, if the brake is used to limit the maximum rotational speed, it must be activated by a signal derived from the rotational speed and braking must be that hard that the maximum rotational speed is maintained. Technically this is possible but it requires acurate regulation of the braking torque. A lot of heat can be generated in the brake if the rotor continues rotating. There will also be substantial wear of the brake pads and the disk in windy areas.

I see the use of a car torque converter and hydraulic valving making the perfect brake to limit the speed... Can use a stall converter that doesn't start pumping until a higher RPM... and electronic controls on the valve to maintain RPM at a safe speed. Unless the VAWT is massive it will never develop the force required to shear off the blades in a torque converter. They make ones that can handle 2,000HP!! I would thin one off a smaller automatic trans would be perfect... as you block fluid flow resistance increases... below a certain RPM losses are fairly low but there so factor that in.

Astro

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Re: Wind mill for heat pump
« Reply #54 on: February 15, 2022, 02:35:55 PM »
is the heavy brake is still in loaded on the turbine?
do you have a picture ?

Mostly one uses a disk brake from a car or a motorcycle. The brake can be used by hand to stop the rotor completely. However, if the brake is used to limit the maximum rotational speed, it must be activated by a signal derived from the rotational speed and braking must be that hard that the maximum rotational speed is maintained. Technically this is possible but it requires acurate regulation of the braking torque. A lot of heat can be generated in the brake if the rotor continues rotating. There will also be substantial wear of the brake pads and the disk in windy areas.

I see the use of a car torque converter and hydraulic valving making the perfect brake to limit the speed... Can use a stall converter that doesn't start pumping until a higher RPM... and electronic controls on the valve to maintain RPM at a safe speed. Unless the VAWT is massive it will never develop the force required to shear off the blades in a torque converter. They make ones that can handle 2,000HP!! I would thin one off a smaller automatic trans would be perfect... as you block fluid flow resistance increases... below a certain RPM losses are fairly low but there so factor that in.

 I was going to respond as well, but sometimes I can come off as a jerk and not even mean to. To me the principals of a cv clutch come to mind. Or just look at the physics of an ice skater. I just do not think it is an unsolvable problem. I worked with mostly people who did not want to hear that something couldn't be done, they wanted ideas on how it could. I know it is off topic but spinning is spinning and this video shows it pretty well.

https://youtu.be/0RVyhd3E9hY