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+--- Thread: A question about solar panels (/showthread.php?tid=10281)
RE: A question about solar panels - Cagary - 04-19-2014
quote:
Originally posted by peteadams
We're entirely off grid with 2.6 kw of panels installed in 2005. We've had several L16 battery replacements since then. Back when I was measuring our daily usage I found we averaged about 4 kw per day. One does have to be frugal with electrical consumption off grid. Our major loads are refrigeration and a 1 hp pump that usually runs on and off over a period of about an hour per day. After asking any number of on grid people, local and mainland, what their usage is (many of course didn't know), it seemed to range from 10-20 kw a day. I once read an article about a couple in Portland, OR who were trying to go green and they stated they had whittled down their consumption to 7 kw per day and found that a bit onerous. After one of our common very gray days here in Puna it's always a good idea for us to run the generator in the evening to pump the batteries back up a bit.
Could you install several more panels so you wouldn't have to worry quite so much during cloudy days?
-Veritas odium parit”(Terence 195–159 BC))-"Truth begets hatred".
RE: A question about solar panels - peteadams - 04-19-2014
"Could you install several more panels so you wouldn't have to worry quite so much during cloudy days?"
You could, though that would have to be a calculation you would have to have confidence in if you wanted to do without a generator. I wouldn't want to be without one in an off grid situation. Also, enough panels to obviate the need for the generator on a gray day would likely be wasted on sunny days and there are limitations in the amount of current the charge controllers can handle. And then there are space issues. We have the lower power panels (160 watt) that were available in 2005 and our 20' rack is full with sixteen of them.
RE: A question about solar panels - Cagary - 04-20-2014
quote:
Originally posted by peteadams
"Could you install several more panels so you wouldn't have to worry quite so much during cloudy days?"
You could, though that would have to be a calculation you would have to have confidence in if you wanted to do without a generator. I wouldn't want to be without one in an off grid situation. Also, enough panels to obviate the need for the generator on a gray day would likely be wasted on sunny days and there are limitations in the amount of current the charge controllers can handle. And then there are space issues. We have the lower power panels (160 watt) that were available in 2005 and our 20' rack is full with sixteen of them.
Can you please tell us about these "charge controllers"?
-Veritas odium parit”(Terence 195–159 BC))-"Truth begets hatred".
RE: A question about solar panels - Tink - 04-20-2014
That would be the control module that "regulates" the power, commonly known as the "inverter". Original solar technology is a DC current panel system, routed through the inverter which converted the DC power into AC, or "normal" house current, and if off grid, switch between batteries and your house current. With technological advancement there are now micro inverters attached to the panel ( you now have a choice, but cannot mix) which are run through the inverter and into your home electrical panel. On homes with solar systems, you might notice another "box" nearby the main electric panel ( might be in their garage) about the size of a tankless water heater, that is it.
Are you a human being, or a human doing?
RE: A question about solar panels - tgalarneau - 04-20-2014
A charge controller is the device that controls the charge to the batteries from the solar panels. If not there your batteries could be overcharged and quickly destroyed. It is a different component than the inverter which converts DC to AC and which may also include a charge controller for charging from the generator when solar is unavailable.
A charge contoller is limited by its amp rating and cannot handle more power from the solar panels than its rating. Because of this I use 2 charge controllers to handle my 3500 watts of panels as the system is 24 volts. If I ran a 48 volt system I could probably get by with 1 contoller because of the reduction in amps.
I use 12 regular golf cart batteries and need between 7,000 to 9,000 watts per day for our household use. This is a minimal battery configuration for 1 day power reserve as I will use the generator to fully charge on any cloudy day so do not need a bigger battery bank. These batteries need replacement after approximately 3 years if treated well.
We are fully off grid and use a refrigerator and small freezer, computers, TV, washing machine, dishwasher and many kitchen appliances and water pump. Pretty much a normal household but do watch the sun and make sure the batteries are fully charged daily and will cut down on use during cloudy periods to minimize generator use.
RE: A question about solar panels - peteadams - 04-20-2014
Charge controllers transfer the current from the solar panels into the batteries. As the batteries get more and more charged the controllers also limit the amount of current delivered to prevent overcharging. Charge controllers are rated on the amount of current they can handle. I've seen ratings from five amps to eighty.
RE: A question about solar panels - Tink - 04-20-2014
An interesting read, albeit somewhat technical, is the book "Photovoltaic Power Systems for Inspectors and Plan Reviewers" by John Wiles. He is highly respected and is considered somewhat the Solar Guru by Building Inspectors, as well as Installers.
Are you a human being, or a human doing?
RE: A question about solar panels - Bullwinkle - 04-20-2014
a good primer for off grid folks - simple and factual - boats have long been a good source for off grid technology
nigel calder a good real as well, remember to size the wire correctly and fuse everything .... under size wire will cause fires.
http://www.amazon.com/12-Volt-Bible-Boats-Miner-Brotherton-ebook/dp/B001AMU8NQ
http://www.powerstream.com/Wire_Size.htm
RE: A question about solar panels - pahoated - 04-20-2014
There seem to be several people referring to kilowatts per day. This doesn't make any useful sense. Electric rate has the units kilowatt-hours or KWH or kw-h.
You have differing loads at different times of the day and these define your minimum and maximum power required. Kilowatts are a unit of power. It is multiplied by time to get a rate.
Then, there is how long these loads last. For instance, a 1000 watt microwave uses 1 KW of power but it only does that for 10 minutes or so (most of the time). All the various electric loads are added for the 24 hour day and that ends up being kilowatt-hours per day. The utility reports it as kilowatt-hours per month. For a single person, it can be about 500 kw-h per month, for a family of four, it can be over 1,500 kw-h per month very easily.
The key factor for a solar PV is what is the peak power it can provide at any time. During the night, this is zero. During the mid day, the sun directly overhead, no cloud cover, is the only time the maximum peak of a solar panel is reached. Any other time, the output power is fluctuating wildly, usually leveled with regulation and batteries.
So, determine what your maximum load is. Take your highest use scenario, the load each device is taking and add those up, keeping in mind the worst case is having every device turned on. For houses with ceiling fans, big screen TV's, computers, electric stove/oven, electric washer/dryer, electric water heater, air conditioning, etc. and everybody is at home with everything turned on, a maximum load of 5KW is about average.
For better instructions, watch Green Acres and see how Mr. Douglas used to handle his electric loads. Also, his interactions with the county, the reliability of his local help, and how it was his dream to live the simple life in the country. Is Puna Hooterville or is Hooterville Puna?
"This island Hawaii on this island Earth"
RE: A question about solar panels - Bullwinkle - 04-20-2014
There is also a big difference in the power produced in winter as opposed to summer - summer is easy - winter requires many more panels to produce the same wattage
good read on the kochs bros. trying to undermine solar:
http://www.latimes.com/nation/la-na-solar-kochs-20140420,0,7412286.story#axzz2zSAWhmKQ