TROPICAL YACHT REFRIGERATION
Yeah! We all know that putting cold stuff in the fridge versus warm stuff will take less amp hours! But just how many less?
In fine tuning our life style I always knew that the colder the product going into the box it would take less energy to make cold than hot stuff. I would shun buying ice, figuring heck I have a great fridge freezer and I can make my own which I can....but at what cost?
Here is a simple example that can be expanded to any food or product:
Take a 6 pack of beer or soda of the truck anywhere during a Mexican summer at 90 deg. F, now I like to drink stuff at around 40 deg.F
So a 6 pack weighs 5 lbs and 90-40 = 50......this is our delta T or temperature difference between the warm and cold drink.
So 5 x 50 = 250 BRITSH THERMAL UNITS (BTU's) of heat energy you need to remove from the 6 pack.
Now if you are using solar energy to charge your batteries you will loose 10% in and out, totalling 20%, this is solar electric to chemical energy back to electrical energy. So add 20% to your 250 BTU's and you now have 300 BTU's of energy to produce using solar panels.
If you were lucky enough to find a store and purchased your beer or soda at 50 deg. F. you would only need to drop it by 10 degrees x 5 lbs and since most solar installations can make enough power when the sun shines we can almost forget about the energy loss going in and out of your battery bank.
So in short 5lbs of beer or soda dropped by 10 degrees = 50 BTU's, a sixth of the energy of the warm stuff.
So if we are doing this on solar energy alone it would mean having SIX TIMES the square area of solar panels to achieve the same result..........COLD DRINKS and rock hard frozen stuff.
If the rest of the stuff you buy is pre chilled with a bag of ice then you will save even more energy as ice is cheap and diesel and gas are not. Also bear in mind that 1 lb of ice in melting sucks 144 BTU's out of your fridge box or roughly an hour of compressor running time. You'll see that ice if and when you can find it is way cheaper than gas or diesel taking all the other costs of maintenance into account.
I rest my case