Connecting Wind Generator to Heater

[baviewboy]

I have a lake property which I only use in the summer. In the winter we have high winds and I was wondering if I it is possible to have a small wind turbine connected to a heater so as to create heat on windy days. It matters not if the heat is consistent.

Is it possible to have the wind turbine connected directly to an electric heater.

This could be my first project to introduce m to wind power so I was hoping to keep it simple.

[BB.]

If you are looking at installing a HAWT (horizontal axis wind turbine), the answer is is that it probably would not be practical/cost effective... You cannot connect a HAWT directly to a resistance load (electric heater) and get optimum heating without using a battery bank + shunt charger in between.

Wind turbines vary RPM / output voltage / output current a lot. You would have to size the resistance/watt rating of the heater to your maximum wind (perhaps 40+ miles per hour), and then it would operate very inefficiently (as a heater) at your normal 10-15 MPH that most "good wind" sites have as average wind speed.

Have you thought about installing a solar thermal array instead? If you are looking for 9+ months of water heating in a good sun area--The starting rule of thumb is ~20 square feet per person for hot water.

Solar Thermal panels will be much cheaper and, probably, be more reliable/less costly overall than a wind turbine based electric hot water system.

Winter may be a bigger issue (subfreezing weather? Poor sun due to weather?), but even in freezing climates people have build solar thermal systems for home heating.

Solar Thermal can be a nice source for space heating and hot water... And usually is "cheaper" per kWhr/BTU vs Solar PV Electric/wind turbines. Also, Solar Thermal lends itself very well to do it yourself projects. Note, these are plumbing projects and have their own issues (leaks, pump failures, installation issues trapping air, anti-freeze, storage, heat exchangers, etc.):

Solar Shed and other Solar Thermal Links

A good place to start reading is Home Power Magazine... They have a free past issue online--and have a lot of articles you can read for free. I don't always agree with them and their reviews--but they are a fun and enlightening read:

Home Power Mag

-Bill

[Cariboocoot]

Welcome to the forum.

Yes, it's possible. How practical it is ... that's different.
For one thing electricity is not a very efficient way to heat things. You may find it doesn't provide enough heat to be worth the effort and expense. And there will be considerable amounts of both.
The #1 problem with wind power is that the site isn't really suitable for it, despite appearances. Turbines like sustained 20+ mph winds for good output. That's a lot of wind. They don't like light breezes which produce nothing nor gusts which spin them up and down and put terrible stresses on them.
The #2 problem is that most of the small wind turbines available are quite frankly junk. They don't produce anyplace near their rated values and they tend to fail fairly quickly and easily.
The #3 problem is the installs don't follow directions. You really do need it up in the air, away from turbulent winds. Lots of clear, open space. And a firm mast with guy wires all well anchored so the whole thing doesn't come crashing down around your ears - and possibly through your skull.

Otherwise, the idea of a turbine feeding a resistive heating element isn't uncommon at all; it is the typical "dump load" required on systems used to charge batteries. Once the batteries are full you need something to do with the continued energy production so that the turbine doesn't over-speed and fly apart. Sinking the excess Voltage to a water heater is quite common.

Keep in mind this would be very erratic and uncontrolled heat, as there would always have to be some element connected to take the power for the reasons mentioned above. No thermostats; it could conceivably get quite warm.

[jmar]

@BB: >>If you are looking at installing a HAWT (horizontal axis wind turbine), the answer is is that it probably would not be practical/cost effective... You cannot connect a HAWT directly to a resistance load (electric heater) and get optimum heating without using a battery bank + shunt charger in between.


Your claim is unsubstantiated. Battery banks and chargers are hideously inefficient, while nothing could be more efficient than pushing the DC or AC directly into heating coils.

The question is how much heating would you get? Would you need 30mph winds just to warm up a space heater? Would those same winds instead cause that same space heater to catch fire or otherwise burn out?

I think that with some control circuitry to switch in additional loads, first with the baseboard electric heaters, then an electric water heater, and then perhaps extra additional banks of room heaters, and possibly after that a trickle charger for batteries.

I have the same idea, and only want heat. I don't want to cut my electricity bills. I want to cut my Propane heating bills.

Solar and wind are complementary and a good strategy is using both. But, given that nighttime winds are the first choice for an energy source for home heat, I am of the same mind as the poster. It's great to see someone else with the same idea. Thanks for posting. Now let's get some real answers, rather than simple diversions.

[Cariboocoot]

jmar;

Did you read post #3?

Bill's comments are not "unsubstantiated" they are factual: in order for a heater to function properly as a heat it needs a consistent power supply to draw upon as needed, so that it may turn on and off in accordance with the demands of heating the area. Otherwise you would simply be dumping random amounts of heat into the room. Heaters do not work correctly with low or varying Voltage, as the elements are designed to function at a particular Voltage and current level. The conversion rate is not linear, so supply 1/2 the Voltage does not produce 1/2 the amount of heat or even 1/2 the amount of Watts (the resistance value of the heating element changes with its temperature).

As for what you could actually expect from running a wind turbine directly to a room heater, the answer is: trouble. Say you have a turbine rated as 500 Watts @ 20 mph. Also say you've got the 20 mph wind consistent enough to sustain the power output. You feed that to a 500 Watt heater. Leaving aside the drop in output caused by Voltage difference (the Watts may be the same, but the heater is likely 240 VAC whereas the turbine's output is more probably 24 VDC) a 500 Watt heater won't heat much space. Most room heaters are 1500 Watts, so you would either need a very large turbine or some multiple of small ones just to power one heater.

You would not have to worry about over-heating it, because heaters have built-in thermal protection which prevents this. That means the connection will be broken if the heating element gets too hot. That also means the wind turbine will suddenly be unloaded, just as it would with a thermostat disconnecting, which is when they can over-speed and come apart. There would have to be a diversion load control on the turbine to keep it loaded at all times, perhaps switching power out to other heaters. This gets complex.

Then there's another problem; the turbine's output is likely DC, whereas the heaters are meant to run on AC. Even on lower Voltage, the controls will not handle DC well. They may arc and burn leaving them permanently disconnected or they may weld themselves shut leaving the heat on all the time. This includes the thermal safety. If the Voltage is at the right operating level for the heater (120 or 240 Volts) the damage to the controls is certain to happen.

When people use heating elements for dump loads they are only used when the batteries are full; not all the time. DC rated switching is employed, and there is no need to gain "real heat" so much as to be sure the turbine stays loaded. Most often the heating is of water, where there is a significant mass to sink the energy to and little danger of over-heating of the element.

To repeat my original statement, yes it can be done. But after looking over some of the difficulties involved as outlined above you can see it is not really a practical solution to heating. It is hardly likely to be economically feasible. The money would no doubt be better spent on improving insulation, stopping drafts, et cetera. It nearly always is. Propane is actually a very good value per $ for heating, unlike any form of electric.

How's that for "real answers"?

[john p]

simple solution . cost negligable
connect in series and parallel some(lots??) 5w resistors and place them under a metal plate then put your feet on the plate and at varing times you will have nice warm feet. no disconnect from wind generator problems

[BB.]

Adding to Marc's post above:

@BB: >>Your claim is unsubstantiated. Battery banks and chargers are hideously inefficient, while nothing could be more efficient than pushing the DC or AC directly into heating coils.

Battery banks are actually pretty efficient running from 80% to 98% (depending on battery type and how it is operated).

The question is how much heating would you get? Would you need 30mph winds just to warm up a space heater? Would those same winds instead cause that same space heater to catch fire or otherwise burn out?

People "run heaters" all the time with wind turbines as shunt loads (keep battery bank from over charging) and/or as "emergency" loads to prevent the HAWT from over-speeding if there where no loads (battery fully charged, circuit failure, etc.).

I think that with some control circuitry to switch in additional loads, first with the baseboard electric heaters, then an electric water heater, and then perhaps extra additional banks of room heaters, and possibly after that a trickle charger for batteries.

From a first approximation, power is:

• Power = V*I = V^2/R = I^2*R

So--you can see, if your voltage varies by a factor of two--assuming a fixed resistance, the power will vary by a factor of 4--Same thing with current.

So--it would take a fair amount of electronics (or load switching) to attempt to keep the wind turbine matched with it loads (not too big, not too small).

I have the same idea, and only want heat. I don't want to cut my electricity bills. I want to cut my Propane heating bills.

IF, (a "big if") I was forced to design an efficient wind based heating system... I would use a Wind Turbine + a MPPT type charge controller (Midnite Solar said they can get something like 2x the power from a wind turbine with properly designed/configured MPPT charge controller like their "Classic" system), a Battery Bank, and a Mini-Spit heat pump (16-26 SEER) and/or a Heat Pump based electric water heater (~2x as efficient as pure resistive heating).

So, the losses of the battery bank (80% worse case), charge controller (95%) and the 2x more efficient heat pump--and 2x wind turbine output with an expensive (MPPT) controller:

• 0.80 batt * 0.95 inverter * 2 heat pump * 2 wind turbine = 3x more efficient with "high tech" system

To run "high tech" heat pumps directly from a variable power source (solar, wind, etc.) at maximum efficiency could possibly be done--But nobody is doing it today.

Solar and wind are complementary and a good strategy is using both. But, given that nighttime winds are the first choice for an energy source for home heat, I am of the same mind as the poster. It's great to see someone else with the same idea. Thanks for posting. Now let's get some real answers, rather than simple diversions.

So, a "simple" resistive load connected wind turbine would generate less than 1/3rd (possibly much less than 1/3rd) as the same wind turbine with MPPT controller + battery bank + heat pump based "heating".

May still not be cost effective--but it would work (assuming the wind turbine performs well).

Again, not trying to stop anyone from experimenting--But suggesting that do a little work with pencil and paper first before spending the time and money to build a working prototype.

-Bill

[The Only Sarge]

I won't get into "efficiencies" etc. here and am not advocating anything.

I will share with the original poster my "experiment" in the barn.

The barn is on top a hill. Fairly constant breeze up there and I needed some lights etc. So I wanted to experiment with wind and solar this time.

The business driver was to have one small (100 watt equivalent CFL light burning about 25 watts) outside light, a 4' florescent light in the feed area and a plug in outlet for whatever. The outside light is driven by a on-off at dusk/dawn socket. Nothing difficult here and very low power usage.

I had some leftover harbor freight panels totaling 90 watts from my beginner days :)
Got one 12v deep cycle 125 amp battery and a 40 amp wind/solar controller a 150 watt small wind generator and a dump load "heater".
For the inverter I got a el cheapo ChinaMart 300 watt inverter.

Bottom line is the barn lights are used so little and the nighttime light draws so little the battery stays charged and the wind generator pretty much stays in dump. The resistors (2 100 watt) put out some heat. Now it is a little difficult for me to tell how much heat they put out as the barn is around 100f during the day....but you can feel the heat from the resistors when you get within a few feet of them.

So to the original poster...is it doable...yup....inexpensive....yup....how much heat....I dunno....but it puts out heat.

I will comment on the lil wind generator.....I thought it would be toy quality....nope...it is tough/solid and built very well.

Take all of this for what it is....just sharing my experiment and maybe it will add some value to what the original poster is looking for and maybe not.

[GreenPowerManiac]

Oh Geez, here we go again.....

My setup is as follows: 4 PMA's wired 3 phase A/C to the rectifiers within 2 feet of each battery bank. I hook up all my turbines after the diodes, D/C straight to the batteries. Any extra power produced from the array(s) is a diversion load to a D/C output. In my case a small fridge/heater box, whichever I choose. That about sums up the heat production from the turbines. Now, to make things simpler, I'd set up a row of small heat lamps (NON-CFL bulbs) direct from the turbines for heat.

I'm aware that it may be illegal to use non-cfl bulbs in California.

[ggunn]

I'm aware that it may be illegal to use non-cfl bulbs in California.

I understand the thinking behind such legislation, but it's a baby-with-the-bathwater approach. Incandescent bulbs are a cheap, convenient low-intensity heat source for things like protecting plants from freezing in cold weather. CFL's are useless for that.