Wind for room heating, want to build a controller, maybe Arduino, PWM? ideas?

[kilohertz]

Hi all, my first post here.

I have had my wind turbine up since 2008, it's an Asian 3KW HAWT and has performed very well into a grid tied inverter but after about 4 inverter failures I've had enough and just parked this with the brake on for the last few years. I have been thinking about using it to either heat my shop or the house basement, at least put some heat in there.

I have been playing with Arduino boards for the last 5 years or so and am ok at programming. This would be as complicated as I would like to make it.

I also thought just simple set point type dump load coming on at various voltages using comparator type op-amps or ?? driving relays or SSRs.

I have a number of different sized baseboard heaters from 300W-1.8KW and am planning to use those.

Anyway, I searched around here and haven't really found any applications dedicated to heating, I could only find "dump load" or inverter protection schemes.

I have several ideas for the Arduino, either set point switching of relays or SSRs or FETs to directly turn on the heaters in stages, or put enough heaters in parallel and PWM from one output into a big FET or IGBT or ??
 
My turbine rectifier is still functional and puts out a nice clean DC, and also has over voltage protection-internal dump load so my plan is to continue using it and work with the DC output.

So I would like to hear from any of you who have some experience in working with wind based heating and I'm open to any other ideas beyond what I have suggested. I am not too worried about MPPT right now but if it could be implemented, I would certainly entertain it.

Look forward to a nice discussion.

Cheers

[DamonHD]

Welcome, and thanks for the detailed intro and problem description!

Rgds

Damon

[electrondady1]

you will need to find something to do with the energy in the summer.
(heat your swimming pool)
 augmenting your heating system in winter is an ideal use of wind energy. the fiercer the wind, the cozier your house gets.
you can shunt the power to you shop when you have a project to do .

[kilohertz]

you will need to find something to do with the energy in the summer.

I'll just shut it down again like it's been for 3 years.    I just tied all 3 AC phases together.

Thanks for the replies guys. Yes it's -22 here this week and steady 10-30km winds with 40k gusts, perfect to put a little heat into the house.  I have some time off this winter and am going to make a real go of this, I have all the ideas, just need to figure out the details.

cheers

[Mary B]

IF you know the output curve vs wind speed into a load start there. You may need to monitor wind speeds to make this work... at X wind speed switch on x amount of heater coil by unshorting the relay across it, next wind speed step unshort the next relay in line until you reach the 3kw of heating coil all on as needed. Would need to buy nichrome wore and make your own heating elements or find 500 watt heaters and series them(maybe baseboard heaters?).

You didn't mention the voltages form the WT... so that will change how this works. Going to need heaters to match the voltage curve under load...

[kilohertz]

Thanks!

Here's the MPPT curves we came up with, power vs voltage. I was working with an engineer at Power One to get these. We didn't use wind speed but plotted voltage vs power and input this into the inverter. There were a number of times that even with this curve and a dump load the DC voltage got to 500 and power over 4KW. The turbine was only rated at 2KW, it seems to be very well built and under rated. I think the 240 VAC baseboard heaters I have will work fine, may put a couple in series/parallel to get the right values. I'm going to have to dig them all out of the lean to, we have 2' of snow on the ground right now and it's -25C today and for a few more days. Brrrrr. 

I think at this point my task will be to start collecting data for each of the BB heaters, both hot and cold, R, current and voltage thru them etc. It may take a little while but I have all the tools to do it, current clamps, shunts, DVMs etc. I think it will be best to build a nice big rectifier to run off the line voltage so I am working with DC, maybe a variac and step up isolation xfmr . Lot's of fun for the winter break. One important thing for those of you contemplating baseboard heaters, some of them, maybe all, have overheat protection thermal switches, which you DON'T want opening under high load. I'll need to figure out how to bypass those.

It might take a few tries to get the MPPT curve to post properly...standby.

Cheers

MPPT 1   (All DC values)   
Volts   Watts   AMPS
50   20.00   0.40
65   43.94   0.68
80   81.92   1.02
95   137.18   1.44
110   212.96   1.94
125   312.50   2.50
140   439.04   3.14
155   595.82   3.84
170   786.08   4.62
185   1076.38   5.82
200   1360.00   6.80
215   1689.52   7.86
230   2068.39   8.99
245   2500.04   10.20
270   2952.45   10.94
300   3780.00   12.60

[joestue]

i build a voltage clipper for a friends's milling machine which sent 70 amps back up the ac line during spindle stop.

a full wave rectifier and a 150 ohm resistor sends voltage through a string of 24v 1 watt zener diodes to turn on a SSR which connects a 10 ohm resistor from the 208v line back to neutral, to hold the voltage down during regeneration. a 10uf capacitor across the SSR keeps it turned on for the next line cycle. a 24v zener across the ssr protects it from over voltage (which gets burned up in the 150ohm resistor)

given you have enough voltage to make such a solution work, you can use multiple SSR's and a single string of zener diodes to send current into transistors.. to turn on a string of SSR's.

you don't need to uniformly load all three phases until you get to higher currents.

alternatively, buy dc solid state relays (a bit more expensive) and combine all the loads after the rectifier. this will result in slightly worse efficiency at high loads due to losses in the rectifier and the lower powerfactor of a simple diode rectifier compared to a resistor directly on the ac line, but it won't be significant to you.

another option given your unusually high voltage is to put capacitors in series with the resistors. the leading power factor both increases excition in the generator (if its an iron cored machine, if air core then it won't, at least not significantly)
and the increasing frequency in combination with the increase in voltage produces a cubic power curve that can match the turbine...

you also have enough voltage to run a vfd.. i have a circuit i can send you to show you how to use two transformers to drive a split capacitor motor (such as the 1 ton compressor in a 120v portable air conditioner) from a 3 phase vfd.

you can then use the varying voltage from the turbine to control the vfd output frequency (which will control the load) and directly drive a heat pump to heat your house. i realize its -25C and this may not work for you part of the year.

[Mary B]

Thanks!

Here's the MPPT curves we came up with, power vs voltage. I was working with an engineer at Power One to get these. We didn't use wind speed but plotted voltage vs power and input this into the inverter. There were a number of times that even with this curve and a dump load the DC voltage got to 500 and power over 4KW. The turbine was only rated at 2KW, it seems to be very well built and under rated. I think the 240 VAC baseboard heaters I have will work fine, may put a couple in series/parallel to get the right values. I'm going to have to dig them all out of the lean to, we have 2' of snow on the ground right now and it's -25C today and for a few more days. Brrrrr. 

I think at this point my task will be to start collecting data for each of the BB heaters, both hot and cold, R, current and voltage thru them etc. It may take a little while but I have all the tools to do it, current clamps, shunts, DVMs etc. I think it will be best to build a nice big rectifier to run off the line voltage so I am working with DC, maybe a variac and step up isolation xfmr . Lot's of fun for the winter break. One important thing for those of you contemplating baseboard heaters, some of them, maybe all, have overheat protection thermal switches, which you DON'T want opening under high load. I'll need to figure out how to bypass those.

It might take a few tries to get the MPPT curve to post properly...standby.

Cheers

MPPT 1   (All DC values)   
Volts   Watts   AMPS
50   20.00   0.40
65   43.94   0.68
80   81.92   1.02
95   137.18   1.44
110   212.96   1.94
125   312.50   2.50
140   439.04   3.14
155   595.82   3.84
170   786.08   4.62
185   1076.38   5.82
200   1360.00   6.80
215   1689.52   7.86
230   2068.39   8.99
245   2500.04   10.20
270   2952.45   10.94
300   3780.00   12.60

(Attachment Link)

I see approximate 45 volt steps to turn on 4 heaters of 1kw each... maybe 5 heaters in case of a gale...

[Bruce S]

 One important thing for those of you contemplating baseboard heaters, some of them, maybe all, have overheat protection thermal switches, which you DON'T want opening under high load. I'll need to figure out how to bypass those.

(Attachment Link)

When you dig them out, go looking for some kind thermistor (normally a single wire, but might look like one they use inline for coffee pots) They open and close according to the dial) most in-line ones are set at 105C then they're like an infinite resistor.  You can get them for a higher cutoff I've seen them up to 145C as snap disks and 216C for the inlines. I prefer the inlines, the snap disks break quicker. They aren't real expensive, I use to buy them at $5USD and and sell the pot for $10USD.

Hope this helps

Bruce S

[kilohertz]

Thanks Bruce,

My BB heaters are the wall mounted type that connect to an external t stat, no onboard dial. I know they cut out when they overheat as I was using one this past fall to load my backup gen and it tipped over and went open cct, I righted it and it snapped back on within 10 seconds.

It might be a few more days, or even post Christmas before I get to this, it's brutally cold and windy right now, supposed to warm up next week.

Cheers

[Bruce S]

No worries on the timing, that weather is heading to the lower Midwest too. Our high is St Louis,MO Friday is to be around -2F ,,,, so yea.
Take your time.
The tipping over may be the internal gyro, our kerosene heater has one, so does the 500w 120Vac heaters we have around in the offices here at work.
IF there's an external dial , then you should be able to check the different resistances as you turn the dial, kinda like a rheostat.
   
Cheers
Bruce S

[OperaHouse]

I did a proportional system with a micro.  As each new heater turned on it would be PWM until full on.  This can be done with MAP function.  Just turning an additional element on dramatically changes the voltage so it will be rapidly cycling anyway.  I don't have wind and do this with solar and a capacitor bank.  You can probably just deal with the inertia of the mill, but some capacitance will be needed for stability.  This will not be a piece of cake program. You will run into things never thought about.