solar fridge design project

[kgmilano]

hi

i've been given a project to deisgn a solar fridge that can keep contents below 5deg. is there any advise that you guys can give on how to tackle the project?how to culculate the solar energy needed, which refrigerant is best for his type of application, ways available to achive this, anything will be highly appreciated. thank you for all the help.

[mikeref]

Hi Kgmilano, you must be looking to run this fridge through a battery first right? Using solar pannels to keep the battery charged is not a problem. This is the convential way portable 12 volt fridges are powered today. As for designing the fridge, there are various methods but the first item on your list is the capacity in litres you want to keep cool, then the box insulation (critical for compressor and power requirements). Let me know what you think...mike

[buddy]

I could help and send you an old Ppt presentation I have on this subject conducted in Africa that may assist you...problem is i dont know how to email such a big file to you?

[kgmilano]

hi Mike

i've choosen to design a 50litre fridge. i was thinking of using aerogel for insulation. is it better to recharge a battery and power the fridge from there or power it straight from the solar panel?

[kgmilano]

hi Buddy

that would be highly appreicated my address is kmafatshe@gmail.com or i could setup an email address where u can save it as a draft there and i go retrieve it.

[mikeref]

hi Kgmilamo, definately have to run fridge through a battery when using a compressor, apart from damaging voltage then low amps from cloud cover, you eventually run into NO power overnight, and therefore no refrigeration. Solar power to battery(with a regulator to avoid overcharging) then fridge runs off battery. Anyway i'll wait to see if "Buddy" has the info your looking for... mike.

[RLK]

Danfoss has a solar powered variable speed compressor that is designed to operate without a battery. It operates 10 to 40 volts of DC power. Overnight energy to maintain box temperature is achieved with eutectic holdover plates. For a complete design see Danfoss’s BD compressor web site: then click on Complete Guidelines Danfoss Compressors-BD Solar.

[mikeref]

RLK, thanks for your input, i had spoken to danfoss (Australia) and downloaded files they sent however nothing along these lines appeared. Guess you have to ask the right questions.

[nike123]

http://www.ra.danfoss.com/TechnicalI..._pa100a202.pdf

http://www.who.int/immunization_stan...ity/pis_e3/en/

[mikeref]

Hey thanks NIKE123, makes me wish i had started this thread.

[joeparera]

Use battery of best quality for your project.

[kgmilano]

Thank you for the input. which calculations do i have to do for the for to determine the amount of energy i have to use for the application, the type of refrigerant, the refrigiration cycle and all.

[mikeref]

Kgmilano, given the above info, you will have to decide on which project to run with. Do you want to run the compressor directly from solar ( THANKS to RLk's post),or go with solar to battery then compressor off battery?

[toprunner]

Why not use the Einstein or Platen-Munter absorbtion processes with sun as heat source? Then cool a TES material to keep temperature.

[icecube51]

Go for the Einstein refrigerator.All you need is heat.

Ice

[icecube51]

sorry, did not see the answer of toprunner, but he is correct.

Ice

[mikeref]

I'm thinking Kgmilano is looking to design his fridge rather than using a working item, i mean it would be educational in theory. To actually build a working model will still require a licenced mechanic to complete.

[kgmilano]

Mikeref- i'll have to go with compressor off battery because the fridge has to run even at night. i have to design a frigde it can be from existing methods but there must be some sort of a "different" mechanical element that i must come up with.. maybe a different refrigerant that has better properties

Icecube51 and Toprunner- i'll look into Einstein, thank u.

[mikeref]

Hey Kgmilano, i had a look through info supplied above, plenty of help there but how do define different? The danfoss compressor is tried and true as is the applications they are put to use in.Going back to your origional post of "design a solar fridge to keep contents below 5c", i'm wondering what the specifics of this project is? Is it about efficiency/reliability or reinventing the wheel <so to speak>. let me know.. I'm all ears.. mike

[kgmilano]

hi Mike its about efficienct/reliabity but it must include something that give "my fridge" an advantage over the other ones.

[mikeref]

Kgmilano, yesterday i finished off repairs to a well known Australian camping fridge/freezer and was looking at how it could be improved, (knowing it has an excellent track record for performance/ reliability and can bounce around the back of a 4wd in the outback for years). The best advantage is insulation, as most brands cut back in thickness for a compact design with large refrigerated space. Then ditch all the electronics not necessary for cooling function, use mechanical thermostat, and base the fridge on a chest design, not upright where all the cold air falls out.What do you intend to keep chilled in this 50L space and why does the fridge have to run overnight, could use eutectic? (as RLK said)..mike

[kgmilano]

Mikeref, i have to design the fridge for rural areas and camping where there's no electricity hence night cooling. food and drinks will be stored. good point on chest design i'll design it in that way!