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colinmcc

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Posts: 149
Reply with quote  #1 
I'm currently involved with a building project in Canada that has stopped due to the winter (-17Degs C this week [frown]) . We have placed 24, 250w 60 cell Solar PV panels on racks on the roof, currently none are wired in and will eventually be adding 24 m215 enphase inverters to create a grid tied system, but at present the site has no hydro power and is shut up 'till the spring.

I was asked if we could use the power generated by the PV panels to provide some temporary heat to the interior of the property, and since the panels are installed and capable of producing power wondered if I could temporarily hook them up to some baseboard heaters in the house.

Baseboard heaters are just resistance wire and couldn't care less whether they are fed DC or AC, so has anyone any practical thoughts or advice?

Thanks,

stillalive

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Posts: 1
Reply with quote  #2 
I have solar PV connected to grid. UK mains are 215-240 volts. Max output is 2440 watts. I run a 3kw immersion  heater through a 120v transformer so it produces about 750watts. I turn it off when the system produces less than 800 watts so that I don't buy expensive electricity unnecessarily.
I can't think of any reason why a simple resistance heater would be any different. There are no electronics that would be sensitive to under-supply. If your panels don't supply enough volts or amps it will use what is available and by its very nature it shouldn't use more than its max wattage..
Solar panels are often connected direct to batteries to charge them; just a diode to stop back-flow of current discharging the battery.

Dave

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sundug

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Posts: 109
Reply with quote  #3 
Quote:
Originally Posted by colinmcc
I'm currently involved with a building project in Canada that has stopped due to the winter (-17Degs C this week [frown]) . We have placed 24, 250w 60 cell Solar PV panels on racks on the roof, currently none are wired in and will eventually be adding 24 m215 enphase inverters to create a grid tied system, but at present the site has no hydro power and is shut up 'till the spring.

I was asked if we could use the power generated by the PV panels to provide some temporary heat to the interior of the property, and since the panels are installed and capable of producing power wondered if I could temporarily hook them up to some baseboard heaters in the house.

Baseboard heaters are just resistance wire and couldn't care less whether they are fed DC or AC, so has anyone any practical thoughts or advice?

Thanks,



The Enphase micro inverters will not produce power without being fed grid power or at least 240AC from another source, substitute not advised. So you are left with using the DC directly from the panels-possible, but dangerous and requiring heavier wiring. Sundug

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mvas

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Posts: 9
Reply with quote  #4 
You stated, "currently none are wired in and will eventually be adding 24 m215 enphase inverters..."
So these Panels are producing a DC voltage, now.
Connect them in Series, to add up the voltage.
Are they ~ 30 volts @ 8.3 Amps MPPT ?
8 Panels in SERIES would produce about 240 Volts DC @ 8.3 amps = 2,000 watts per set of 8 PV Panels.
The wire for that would not be very thick at all.

Are your baseboard heaters ~2,000 watts each?
colinmcc

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Posts: 149
Reply with quote  #5 
Mvas, Yes the inverters are not yet fitted, and I agree with your comment "8 Panels in SERIES would produce about 240 Volts DC @ 8.3 amps = 2,000 watts per set of 8 PV Panels." MPPT is built into the enphase inverters so is not part of the present install, and I am really uncertain as to the power production without it.


The Polar High is still here with about -15degs today, and the metal roof is like glass. I tried getting to the panels last week (with a rope and harness on) and decided that it was far to dangerous and cold to mess around with temporary wiring that would have to be replaced later anyway, so the project is shelved 'till the 220V Enphase M215 set up can be completed in the spring. 

Thanks everyone though for your input. ;-)
GaryBIS

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Posts: 243
Reply with quote  #6 
Hi,
If the south face of the house gets good sun, you might consider doing a temporary (poly film) low thermal mass sunspace, and using a blower and some short ducting to get the heat into the house.

Low mass sunspace produce a lot of heat -- my test one which is only 200 sqft of glazing produces 235K BTU on a cold but sunny mid winter day -- equivalent to 3.6 gallons of propane burned in a 70% efficient furnace.

Low Thermal Mass Sunspaces: http://www.builditsolar.com/Projects/Sunspace/sunspaces.htm#LowMassSS

Just a thought [smile]

Gary
colinmcc

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Posts: 149
Reply with quote  #7 
Thanks Gary, It isn't my property, but I read the article you linked to and it gave me food for thought!
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