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12 or 110 volt system
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adria...@gmail.com
Mar 29, 2012, 10:39:07 AM3/29/12
to
I am setting up 240 watts of 12 volt solar panels (maybe adding wind
power later) for an off-the-grid system at my cabin. I only use the
cabin some weekends, and plan to use the system for a water pump,
refrigerator, lighting, computer and other small appliances, but not
for heating or cooking. I assume there would be some loss of
efficiency if I used an inverter to change to a 110 volt ac system.
Would this loss of efficiency make it cost-effective to use all 12 v
dc appliances, compared to using an inverter and conventional 110 volt
ac appliances?
power later) for an off-the-grid system at my cabin. I only use the
cabin some weekends, and plan to use the system for a water pump,
refrigerator, lighting, computer and other small appliances, but not
for heating or cooking. I assume there would be some loss of
efficiency if I used an inverter to change to a 110 volt ac system.
Would this loss of efficiency make it cost-effective to use all 12 v
dc appliances, compared to using an inverter and conventional 110 volt
ac appliances?
Mho
Apr 2, 2012, 4:46:37 PM4/2/12
to
Real toss up depending on how far you will pursue this.
If you want to get serious later with 120Vac appliances you will need to go
48Vdc system sooner, rather than later, but....
You will not be able to stick 12Vdc appliances and lights on available quite
readily from the automotive industry. A friend of mine is doing this exact
same thing. He is wiring the cottage (camp, cabin) for 120Vac, getting the
wiring inspected and recorded for later, and running the place with 12Vdc.
He is currently converting a ceiling fan to 12Vdc and a few lamp sockets.
All his normal house wiring switches will function as they would on the
grid. He will use an inverter for the small appliances he needs to run and
he will get an education on 12Vdc systems, the old fashioned way, like the
rest of us.
Some things to watch for:
- If you conceal wiring that could become "on the grid" get it inspected
first! The wall finish (drywall or panelling), vapour barrier and insulation
will have to come off to be inspected.
- If you get an inspection make sure the records are kept. They make have
lost the file in 15 years from now and the same, above would apply.
- Research "Peukert factor" for battery capacity. It basically states that
that 120 Ah battery you paid so much for is only 120Ah at it's rated
discharge. Push it to 5C load factor (=600A@12Vdc= 50A@120Vac) and cool it
to 0C degrees and you end up with about 20 AH capacity. Go big or go home.
- Calculate wire sizes for these 12Vdc appliances. Look up the copper and
connections required for the 600A example currents above. This is one of the
reasons why the bigger systems go 48Vdc
- Get a Honda generator for backup. If you never need it, you spent too much
money. EU2000i is quiet and cheap and has prevented me from freezing to
death or checking into a motel a few times.
Best of luck! It's a great hobby!
------
wrote in message
news:1b2f2ab9-987e-42b5...@k6g2000vbz.googlegroups.com...
If you want to get serious later with 120Vac appliances you will need to go
48Vdc system sooner, rather than later, but....
You will not be able to stick 12Vdc appliances and lights on available quite
readily from the automotive industry. A friend of mine is doing this exact
same thing. He is wiring the cottage (camp, cabin) for 120Vac, getting the
wiring inspected and recorded for later, and running the place with 12Vdc.
He is currently converting a ceiling fan to 12Vdc and a few lamp sockets.
All his normal house wiring switches will function as they would on the
grid. He will use an inverter for the small appliances he needs to run and
he will get an education on 12Vdc systems, the old fashioned way, like the
rest of us.
Some things to watch for:
- If you conceal wiring that could become "on the grid" get it inspected
first! The wall finish (drywall or panelling), vapour barrier and insulation
will have to come off to be inspected.
- If you get an inspection make sure the records are kept. They make have
lost the file in 15 years from now and the same, above would apply.
- Research "Peukert factor" for battery capacity. It basically states that
that 120 Ah battery you paid so much for is only 120Ah at it's rated
discharge. Push it to 5C load factor (=600A@12Vdc= 50A@120Vac) and cool it
to 0C degrees and you end up with about 20 AH capacity. Go big or go home.
- Calculate wire sizes for these 12Vdc appliances. Look up the copper and
connections required for the 600A example currents above. This is one of the
reasons why the bigger systems go 48Vdc
- Get a Honda generator for backup. If you never need it, you spent too much
money. EU2000i is quiet and cheap and has prevented me from freezing to
death or checking into a motel a few times.
Best of luck! It's a great hobby!
------
wrote in message
news:1b2f2ab9-987e-42b5...@k6g2000vbz.googlegroups.com...
amdx
May 10, 2012, 11:55:53 AM5/10/12
to
I think you are very optimistic.
I'm not the right one to run the numbers but here's my guess.
If you assume you will get 240 watts 6 hrs per day on average, (this may
be optimistic) that's 1440Wh or call it 1.5kWh.
If you charge and discharge lead acid batteries your efficiency is
near 50%.
http://photovoltaics.sandia.gov/docs/PDF/batpapsteve.pdf
So now you have 0.75 kWh of energy to run your pump per day.
I don't think that will run your refrigerator for the day.
If you have an inverter it may run at 85% efficiency.
Mikek
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