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jimeli

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Joined: 05/11/2013
Location: Ireland
Posts: 1

Posted: 11:47am 06 Nov 2013

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Hi - I have a wind turbine (2.1 - 2.5 kw) with 3 / 1.5 m blades. It is 24 volt and I bought it last year. My question is - can I use it to heat a 24 volt immersion heater in my domestic hot water cylinder. I would only expect it to assist my current heating system. So I have the turbine and the immersion heater but I need to know what else I need to purchase in order to get going eg type of battery, type of regulator etc ???.

thanks
jimeli

Madness

Guru

Joined: 08/10/2011
Location: Australia
Posts: 2498

Posted: 01:22pm 06 Nov 2013

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What is the current rating of the heating element?

If it is around 2.5 KW you could connect it directly to the generator. However you would need to consider that you will boil the hot water system after some time and will need to either shut down the generator when the temperature is too high or bleed off hot water to regulate the temperature.

If the element is a different rating it makes it more complicated.Edited by Madness 2013-11-07

There are only 10 types of people in the world: those who understand binary, and those who don't.

Don B

Senior Member

Joined: 27/09/2008
Location: Australia
Posts: 190

Posted: 10:02pm 09 Nov 2013

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Hi Jimeli,

You could connect your wind turbine directly to your immersion heater, but you would probably be disappointed in the results. The immersion heater is probably designed for 240V operation, so connecting it to a 24V supply means that it will only draw one tenth of its operating current. With one tenth of its operating voltage supplying one tenth of its rated current, it would only be providing one one hundredth of its nominal wattage (and hence heating). Bottom line - cold showers - even in strong winds.

If you could find a much lower resistance (or higher wattage) 240 volt element, you might see some heating, but you really need an element designed to work at 24V.

To put some numbers to this, a 2 kW 240V element will draw around 8.3 amps when supplied at 240 Volts, and have a resistance of around 29 Ohms. With 24V applied, only 0.83 Amps would be drawn by this element, and the resulting wattage would be 20 Watts. Brass monkeys would be advertising for welders after showering under hot water from this heater in this circumstance.

You need to realize that, at 24 Volts, the DC current that flows for, say, 2kW output is 83 Amps. This requires big cables, and a substantial immersion heater with a very low resistance of around 0.29 Ohms. Moreover, wind turbines generate (at least) 3 phase AC. Each phase is therefore contributing around 28 Amps of the total 83 Amp output. Ideally, you would need a 3 phase heating element, as this would let you avoid needing high current rectifiers to permit you to combine the output of the three phases into one 83 Amp DC output.

There is then the concern of what happens when you have somehow obtained a suitable low resistance element, and you experience sustained strong wind. When your water is as hot as you need, the thermostat will then switch the element off, and unload the turbine. Most turbines need a load, otherwise they will overspeed in windy conditions. This is usually catered for by a dump load of some sort, plus furling.

Bottom line is that I think your system needs some more research and thought.

Regards

Don B

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