To give you an idea, we run our entire 1200 sq. foot cottage on solar, our entire array is 1.4 kw (kilowatts) or 1400 watts. Our little freezer (5.6 cu. feet) uses about .8 kwh per day in the summer. I would estimate that a few hundred watts of solar would be enough for yours, but if it is really large and really old, I'd consider replacing it with a newer, maybe slightly smaller chest model, they use about half the power. That amount of solar in todays market might cost you $600 - $800 USD. You'll also need the batteries, I would think 2 T-105 golf cart batteries would be plenty, another $200 USD, and at least a 1500 watt inverter, but a cheaper modified sine wave inverter would work, another $250 USD. If you just want to run the freezer, you could do it with a $1000 system.
What I would suggest is you get a subscription to Home Power Magazine, then do some more general research in solar power and inverters. We did 13 years ago, now we are completely powered by the wind and sun. Panels do not degrade even measurably after 5 years, mine are 12 years old, and most good quality ones are warrantied to put out 90 % of their rated power for at least 25 years. What you should take away from this is that you can't put too much investement in information you get here on these online general forums for unusual equipment like this. In my 13 years using, and teaching solar power at the local schools, I've learned that 2 things are in vast supply, sun, and missinformation. I'm always amazed how many people are willing to weigh in with information on this, who have never laid a hand on a panel or inverter. Check out the sources below, do some more reading, call some suppliers you find in the magazine and ask questions. If it were me, I'd make your system a bit larger, and add in some small 12 volt LED lighting strips in high traffic places in your home, like the kitchen and bath. Then you'll be offsetting more electricity use, and have lighting and refrigeration backup power if the main power is out. Our regular home works just this way, and our lower electric bill reflects it, as well as our house is always the place people come visit when the lines are down. Good luck M, and take care, Rudydoo
It depends on the duty cycle of the freezer, outside temperature and how full, how often it is opened, etc, but generally speaking you will need several square meters worth of solar panels and the cost will be in the lower single digit thousands of dollars, plus installation if you don't DIY.
They do not last indefinitely, the least expensive type will have significant degradation in output within 5 years, while others more slowly degrade over about 20 years. It also depends on the environment, some can be damaged by hail or need more maintenance if there are large swings in cold winter vs high summer temps, but this also depends on how well the panel is constructed.
The batteries will need replaced every few years, usually under 5 years (unless you buy a larger, more expensive battery bank so it drains less each time it is used but even then the lifespan is finite) and given reasonable quality panels expect to pay 50% of their cost again in maintenance and towards replacement funds every decade, although there are some advancements being made in efficiency so that 50% figure may shrink in the future.
Some people get lucky and have lower long term maintenance and replacement costs but that tends to be those who paid more for higher quality panels in the first place and they still need a new battery bank periodically.
Solar panels lose efficiency over time (most silicon panels are guaranteed to have 80% of their output over 25 years), but the main thing that would require maintenance is your battery. Even deep cycle lead acid batteries will require replacing every 5-10 years. There are batteries called Edison cells that have a much longer life, but they are bulky, expensive, and work poorly at low temperatures.
If the freezer draws 200 watts when it is running, and runs 50% of the time, that's 2.4 kwh/day. You need enough battery to supply that for three days with no input (because of clouds and snow cover) without discharging them more than 50%, so that's about a 15 kwh battery bank. That's 6 L16H batteries in series/parallel, or 6 2V L16's (Trojan 2V L16RE batteries SUCK - don't even consider them) batteries in series. You'll need a 2000 watt plus inverter, a charge controller capable of putting out 60-80 amps, and about 1000 watts of panels.
If you grid tie, you can cut your system size in half, and not worry about the batteries or charge controller. It will require a grid tie inverter and approval/inspection from your power company, which is a significant expense. This system will work as long as the grid is up..
DK
Solar panels last indefinitely, generally solar panels lasts 25-30 years. Total of 1000 watt approx will be needed for solar panel. You can use in single panel or you can use by combining more than one panel.
How many solar panels are needed to power a big freezer? (And at the same time save enough electricity in batteries to cool during night as well)
Would there be any parts in the "circuit" that would need replacing or would such a set-up work indefinitely?
