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AndrewHighlands
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# Posted: 14 Oct 2020 11:52pm - Edited by: AndrewHighlands
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Hello,
I'm new to this forum, having just discovered it. It seem like a nice community.
I've recently moved off-grid to the Highlands of Scotland after 14 years in academia and industry as a gasification engineer.
I've already put the foundations in for my cabin (which I'm building myself), so I'm currently in a caravan.
Though I have a basic understanding of electrics and have done simple fitting of wires and plug sockets in my old house, I am less knowledgeable about this than other aspects of self sufficiency. I wonder therefore whether someone can help me with some advice?
I'm planning on buying a small wind turbine to keep my caravan battery charged and which I'll then use for my cabin. I understand that turbines need a dump load to stop them over-speeding in very high winds, and that this is connected via a bypass controller. What I don't understand is how to determine what specification of resister/immersion heater to buy and connect as a dump load. The turbine will produce 12v DC as it has an inbuilt rectifier. Can I just collect this to a standard 240v immersion heater element? I was thinking of connecting it to the one in my caravan.
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ICC
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# Posted: 15 Oct 2020 01:26am
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Yes you can use a 240 volt heater element as a dump load for a 12 volt turbine generator. However, the power used by that 240 volt element at 12 volts is greatly reduced. This is becsuse of Ohm's law which governs how the volts, amps and watts interrelate.
Note that the output voltage of the 12 volt turbine generator would be about 15 volts in round figures. The following chart info shows how to easily calculate the watts that a 240 volt element would consume on different battery/generator voltages.
Note that a 240 volt element on 120volts uses 1/4 the watts... only 500 watts.
240 VOLT HEATING ELEMENTS
12 VOLT BATTERY SYSTEM DIVIDE BY 256 (2000W@240V=8W@15V)
24 VOLT BATTERY SYSTEM DIVIDE BY 64 (2000W@240V=31W@30V)
48 VOLT BATTERY SYSTEM DIVIDE BY 16 (2000W@240V=125W@60V)
That heater which can use 2000 watts at 240 volts does almost no good at 12 volts. 8 watts is virtually nothing. Less than 1 ampere. There are heater elements made for low voltage use. They will be harfer to find and likely more expensive.
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Brettny
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# Posted: 15 Oct 2020 08:12am
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I have been to Scotland and it can be very windy. The emerson hot water heater is a good idea. You can also use any other type of resistance...and electric heating element. Either way I would make provisions in the wind turbine tower to lower it out of the wind.
Most of these wind turbines are 500w. 500w for 24hrs a day becomes alot of power.
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AndrewHighlands
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# Posted: 16 Oct 2020 07:56am
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Thanks for the replies,
Yes, its the best wind resource in Europe, but (as you say) this has its downside because it increases the wear on turbine bearings.
Thanks ICC, but I can't follow your numbers. I see that you are saying that it uses a quarter of the Watts, but (in the table) where do you get the '256' '64', and '16' from.
So, do I understand that the immersion heater will provide resistance, but it won't heat the water?
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NorthRick
Member
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# Posted: 16 Oct 2020 01:51pm
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How about an inverter to go from the 12 volts to 240 and then to a 240v heater element?
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ICC
Member
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# Posted: 16 Oct 2020 03:00pm - Edited by: ICC
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Quoting: AndrewHighlands Thanks for the replies, Yes, its the best wind resource in Europe, but (as you say) this has its downside because it increases the wear on turbine bearings. Thanks ICC, but I can't follow your numbers. I see that you are saying that it uses a quarter of the Watts, but (in the table) where do you get the '256' '64', and '16' from. So, do I understand that the immersion heater will provide resistance, but it won't heat the water?
Read through this link. It should explain in an understandable fashion. It is where I copied the table from. Basically everytime you cut the voltage in half, the watts used is reduced by 1/4.
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