Solar panels for running a fridge

[Ellinor Smith]

Good morning,

I live on a farm without electricity and would like to be able to use a low energy fridge that has an output of 60 watts. I have a small solar system with 200 watt panel and a 200 volt battery. I been told that it would be enough to add extra 200 watts panels, and only run it at daytime. Would that work?

I also have been suggested to buy a separate solar system only for the fridge. What is the best solution?

Thanks,

Ellinor Smith

[Rob Beckers]

Hi Ellinor,

The Wattage of the fridge is not all that relevant, they have a thermostat that switches the fridge compressor on and off all the time, and the real question is how much energy per day it uses.

Very much in general, a small bar fridge clocks in around 0.5 kWh per day, while a large 18 cu ft would be closer to 1 kWh per day (the yellow tag that comes with the fridge will show annual energy use, add 20% for real-world conditions). Those are regular fridges, AC or DC (such as the Unique brand of DC fridges). There are very efficient DC fridges such as those made by Sundanzer, they clock in around 0.25 kWh per day.

For an AC fridge you also have to run an inverter to create the 120V AC (from battery DC), and those use energy too. A general number is around 0.5 kWh per day for the inverter. So that gives a range of fridge with or without inverter between 0.25 and 1.5 kWh per day.

In our general area (Ottawa, Canada) a single 300 Watt panel produces around 0.8 kWh per average day between spring and fall, and half that in winter. That assumes a decent tilt-angle, south-facing, and no shading (and no snow in winter). Your area may be different of course. So, over here it takes 1 panel of 300 Watt to run a smallish DC fridge, and 2 panels for an AC one.

Hope this helps!

-RoB-

[Joe Blake]

Hi Ellinor,

Have you got access to a "caravan/ camping" store in Ethiopia? In Australia they have an interesting selection of camping fridge/freezers which run on 12/24v DC/ 240 AC. I've been using three(!) Engel freezers, 2x40 litre capacity and 1x60. I'm unable to give you exact figures on consumption, but when running on 240 volt AC via a 12 volt inverter, the three draw about 150 watts together. During the day their temperature can go as low as -19 degrees C, then they can switch to 12 volt DC overnight which draws less power, and the temperature can rise to -4 degrees C. I've found putting bottles of water (which freezes) in them gives a "cold bank" which helps stabilise the temperature.

The Engel uses a SwingMotor.

https://www.engelaustralia.com.au/about_SwingMotor.html

https://www.engelaustralia.com.au/editor/attached/20121023/20121023120447533404.jpg

They are running probably about 95% of the time and are a case of "slow and steady". My original freezer is into its 12th year I think and still chugs merrily away.

I have 5 solar panels (the oldest being 12 years) with a nominal capacity totalling about 500 watts @ 12 volts and a battery bank of about 4 kWh (roughly) (Trojan T105)

https://www.12volt.com.au/General%20Htmls/webcat2003/Batteries/T105_L16H_TMH_SCS150_SCS225.jpg

Good luck with building your system.

PS Perhaps you could use the freezer as a source of ice and put bottles in a "big" fridge to use as the old "ice chest" of my youth, or a large capacity insulated cooler.

[Ellinor Smith]

Thank you so much, I am totally GREEN in this area. We have rain seasons which reduce the power as well. Only ordinary fridge is available, but now I know how to calculate it better. The bottles from the freezer is a great idea! Thanks for a great forum. //Ellinor

[Ralph Day]

Hi Joe
Those Engel fridge/freezers look interesting. I checked prices in Canada...wow! Have the compressors ever been ramped up to house sized units, or do you just have to make do with a whack of smaller ones?

If I camped a lot it would be nice...the camper has a 120/propane unit that does ok. I've used my daughter's plug in Peltier type 12v cooler a few times. Last time it was to replace the use of a full sized fridge in a cottage for a couple of days. The pv/battery system was sketchy and the cooler kept perishables safe. But over $1100 Cdn would be too much for a once in a while use.

How's your winter going? Solstice yesterday, sunny and not too hot here so excellent for pv production.

Ralph

[Joe Blake]

Hi Ralph,

My present compressors are a little larger than a beer can, but I haven't heard of a swing motor being made much bigger.

The freezers are pretty expensive here as well, but given that I use them daily, and the oldest one is probably going to celebrate 12 years, they give me a feeling of good value for money. As the advertising blurb says, there's only a single moving part, and I've read somewhere that it is "self lubricating"(?) so that should last some time. (I use the ice bottle in the (240 volt) fridge quite a lot during summer. This reduces my power consumption for the fridge from 4 kWh to 3 kWh over about 12-13 days.)

Our weather is suddenly very "winterish". We've had a very serious dry spell both in the West and on the Eastern side (many parts are into several years of drought, and several cities, including Sydney and Perth, are relying upon desalination plants for their daily water.) We've had the wettest June in quite a few years but still below the long term average, both for the month, and worse, only about 75% of the year to date. And with all the grey skies, my monthly solar generation is at about 55% of monthly consumption. (But that is the case as normal. For 9 months of the year I'm generating more than 100% for the month, peaking at over 140% during the "happy times".)

Ellinor, yes, this forum is a very interesting (and occasionally fun) place to hang out. Keep us posted on your progress. :idea: