Use the sun to power fridge.

[wdc]

Hello, first off, I want to declare I know PV energy to power a fridge is way more expensive than grid power, I'm not looking to save money, just want to use the sun to power my fridge.

I live in a place where I get 7 months a year of sunny days (strong sun) and 5 months of cloudy days, the longest row of cloudy/rainy days is usually five, so I'm looking for a 4 days autonomy. I have grid power, so anytime I can plug my fridge to the wall and use the company's power.

My fridge is a 10 years old no frost 195W 220V 50Hz one, nothing fancy, 1,7mt high, about 0,6mt wide. I don't have a killawatt and don't now how many amperes use and how many watts it takes to surge but I'm guessing between 1000 and 1500.

This is a very early project, I won't buy anything soon, I'm planning to buy in 6 months more when the prices get lower.

I'm thinking about this configuration:

• 2 panels, 500W each, connected in series. (1000W total panels)
• 2 AGM batteries, 225AH each, 12V, connected in series to work at 24V (450AH total)
• 1 Mppt 60A charge controller, known brand.
• 1 Pure sine wave inverter, 1500W at least, known brand.
• Thick cables and a digital voltimeter to keep an eye on the battery bank charge anytime.

There will be nothing more connected to the system, only the fridge. I wish this could work year round but I can live with it working the 7 sunny months only.

Any thoughts? thanks in advance. (sorry for my english)

[J.P.M.]

Since your asking for thoughts: If nothing else, I'd spring for the $25- $30 or so for a kill-a-watt meter and a few bucks on a book on PV power before I sought opinions or bought equipment. Either is never a bad investment. Always good to know the loads you're trying to meet before designing power equipment.

You're welcome in advance.

[wdc]

Since your asking for thoughts: If nothing else, I'd spring for the $25- $30 or so for a kill-a-watt meter and a few bucks on a book on PV power before I sought opinions or bought equipment. Either is never a bad investment. Always good to know the loads you're trying to meet before designing power equipment.

You're welcome in advance.

Thanks, it's a good advice. I'll start to search for a killawatt.

[Mike90250]

Simplest, easiest is to install a small Grid Intertie system, A couple of panels and inverter, and now the sum powers your fridge, and the grid keeps it running 24/7
No batteries, nearly no maintenance .

[wdc]

Simplest, easiest is to install a small Grid Intertie system, A couple of panels and inverter, and now the sum powers your fridge, and the grid keeps it running 24/7
No batteries, nearly no maintenance .

I didn't know there was that option, thanks! I'll think about it.

[SunEagle]

I didn't know there was that option, thanks! I'll think about it.

Since money is not a object then I would go with a grid tied system which will provide lower energy costs for you and still have the ability to run all of your loads at night. Adding batteries is a very expensive option along with requiring you to now keep an eye on them so they don't fail you when you really need them.

[wdc]

Since money is not a object then I would go with a grid tied system which will provide lower energy costs for you and still have the ability to run all of your loads at night. Adding batteries is a very expensive option along with requiring you to now keep an eye on them so they don't fail you when you really need them.

That's so true, batteries are heavy and expensive, but I really would want to depend only on the sun. Nevertheless I will consider a grid tied system, thanks SunEagle!

[SunEagle]

That's so true, batteries are heavy and expensive, but I really would want to depend only on the sun. Nevertheless I will consider a grid tied system, thanks SunEagle!

Well even the best solar panel location with axis control will only get you useful power for much less then 50% each day. So to keep any electrical device running the rest of the day will require either the grid or some other power source like a battery system or generator. Neither of those will be as cheap as the grid prices.

[wdc]

Well even the best solar panel location with axis control will only get you useful power for much less then 50% each day. So to keep any electrical device running the rest of the day will require either the grid or some other power source like a battery system or generator. Neither of those will be as cheap as the grid prices.

Thanks SunEagle, I had no idea that kind of thing existed, are your talking about this?= https://www.amazon.com/Inverter-220V...7424108&sr=8-5

It seems too good to be true.

[SunEagle]

Thanks SunEagle, I had no idea that kind of thing existed, are your talking about this?= https://www.amazon.com/Inverter-220V...7424108&sr=8-5

It seems too good to be true.

While that hybrid inverter would help keep charging batteries you are still susceptible to daylight hours and if the sun is shining. With a generator you can keep loads energized anytime of the day even during a storm or clouds.

[chrisski]

This is a very good sticky about system design:

Solar Off-Grid Battery Design - Solar Panels - Solar Panels Forum (solarpaneltalk.com)

Really depends on what that kilawatt meter says. It will read less when its cool out and more when its hot out, so good to get measurements on the fridge when its working the hardest probably summer. That's how you'll get your Kwhr you plan for.

I think you can do a off-grid system for this. A homemade portable generator may cover it, but the Kwhr will tell you for sure.

With grid tied there is all sorts of permitting and t's to cross and i's to dot. For a whole house, needs to be done correct. A smaller project like a 2 kwhr a day fridge is something different easier.

[bcroe]

Off gridders need a fridge with enough thermal storage, that it is only needed
to actually power it 6 hours a day. Still needs a backup. Bruce Roe

[wdc]

While that hybrid inverter would help keep charging batteries you are still susceptible to daylight hours and if the sun is shining. With a generator you can keep loads energized anytime of the day even during a storm or clouds.

Thanks SunEagle but I don't need a generator, I have stable grid power, I liked that hybrid inverter because, if I'm not wrong, it can choose between three energy sources to power my fridge: solar panels, battery and grid, it can be configured to priorize solar panels, then battery and lastly grid, and it can charge the battery with solar or grid keeping it full charged to be used from sunset until a configurable low battery voltage (and then switch to grid power), that's why I said it looks too good to be true, because it replaces human support completely (if I'm not mistaked)

[SunEagle]

Thanks SunEagle but I don't need a generator, I have stable grid power, I liked that hybrid inverter because, if I'm not wrong, it can choose between three energy sources to power my fridge: solar panels, battery and grid, it can be configured to priorize solar panels, then battery and lastly grid, and it can charge the battery with solar or grid keeping it full charged to be used from sunset until a configurable low battery voltage (and then switch to grid power), that's why I said it looks too good to be true, because it replaces human support completely (if I'm not mistaked)

The problem most people that have batteries is that some days there is not enough sunlight to charge them and if that also happens when the grid is down then a generator (it could be a small one) is necessary to bring the batteries back up to full strength.

Just a thought for you.

[wdc]

Well, I bought a wattmeter and measured the power consumption of my fridge over one exact week=11,5Kwh

Then, I calculated about 500w of solar panels (I'd go with two 500W panels connected in series) needed to run the fridge with my city average solar radiation, and 518Ah worth of AGM batteries to have a 5 day autonomy (I'd go with two 250AH 12V AGM connected in series), and a 50A dc->ac inverter at least (I'd go for a 60A one).

Are these calculations correct, or at least not so wrong? thanks!