what refrigerator for off grid system

Re: what refrigerator for off grid system

RV refrigerators tend to be Propane type--and they can last for many years. Some other "fuel" fridges, like kerosene, tend to have more maintenance issues (soot, wicks, etc.?).

I too would stay away from a DC/solar fridge. Very expensive, tend to be small, and some brands have issues with quality, sweating door gaskets, etc.

A standard Fridge (or a chest freezer converted to a fridge with a small air circulating fan and a refrigerator type thermostat) is probably the best bet, and they are very efficient.

For your situation, an ice box, and pre-chilling (and pre freezing) the food and simply storing it in a thick insulated container is probably the better choice (if you are there 4-5 days a couple times a month)...

Problem with solar is that they really make economic sense if the power is used 365 days per year--if you start only using it 10 days per month in the summer--the rest of the power is wasted (if there is nobody there) and the price per generated (used) kWatt*hours become extremely high (and one can argue that this is not a good use of resources regarding the solar panels).

If your usage of the site is so low, your best bet is a good (or a couple) of gas or diesel generators makes most economic sense (if an ice box won't work).

If, however, you can use the power when there is not a hundred people there (neighbors, irrigation, caretaker, eventual full-time living, etc.), then going solar (with generator backup) can make a good investment into the future.

Your last alternative would be to use a generator to charge batteries during the day (or before/after gatherings). It would keep place quiet, and the batteries (with a small solar panel + charger controller) would last for years with the light use (and good maintenance).

-Bill

Re: what refrigerator for off grid system

Here is one thread with lots of discussion about the conversion (it is not hard, and may use up to 1/2 the energy of a standard fridge)...

Also, try the SEARCH function with the terms "chest freezer fridge" and you will find a lot of threads on related topics (DC, Propane, etc.).

In the end, your best bet would be to figure out how much power you will want to run the facility--It may turn out that just by adding a few extra panels or even just sizing the batteries a bit bigger, you may be able to run the extra fridges without much extra money in solar.

Also, if your large retreats are only during good weather (usually a given that people plan retreats for when the sun is shining and not during the rainy/cloudy times), it is possible that sizing your needs for 365 days per year would leave more than enough power for the few times you need the extra power during the "sunny" times of the year.

Check out the US Government's Energy Star program... They have a listing of some pretty energy efficient appliances. It is interesting that some of the very expensive DC solar/battery powered fridge/freezer units are not even efficient enough to meet the standards that a home fridge/freezer unit must meet.

Also, adding features (like auto defrost, ice makers, etc.) do add to the energy draw--if you don't need them, getting the very simple appliances can save some more energy too.

Depending on weather and other issues, you probably will still want a backup generator too--I understand that you want to reduce pollution--but it is better to have solar supply 95%+ of your needs rather than oversizing it by 2x-4x to handle the last few percent (bad weather, the very occasional large conference, if a charge controller or inverter fails, etc.).

To do solar does require a lot of planning and pre-designing in for conservation... While you can always throw more "solar" at a problem--the system gets big and expensive real fast.

I assume that you don't have utility power at this location? Because, if you do have utility power it would be much better for you to go with a Grid-Tied solar system (your solar panels supply power during the day and spin your meter backwards, but at night the utility supplies your power). In very rough numbers, you can do this for something like $0.25 per kWhr (US prices--don't know Mexico)...

Trying to do the same thing but off-grid (no utility power), your price for electricity is going to be more in the $1.00 per kWhr (which is typically 5-10x the cost of utility power in the US).

So, designing a community focused around conservation (CFL lights, energy efficient appliances, using natural air flow, insulation, no air conditioning--if possible, solar powered well pumps, ability to shift loads to when the sun is shining--like washing, etc.) will greatly affect the price of your solar power system.

Also, it is kind of difficult to distribute DC power around a large community... AC power is easier to deal with (use transformers to step up and down voltage for transmission), but you would probably have more losses.

Designing a central core with heavy appliances (washer, fridge, microwave, well pumps, A/C for clinic, etc.) with a large solar system... And using small distributed arrays+batteries for lighting, radio, etc. in the sleeping cabins.

I am certainly not an architect or solar village designer--but working the issues out ahead of time could affect the end costs (of your solar power system) by a factor of ~2x--depending on the final outcome of the design process and the needs of those working/living there.

-Bill

Re: what refrigerator for off grid system

I believe that the DC refrigerators generally use electronic commutator (like a DC computer fan). The ones I looked at don't use a DC motor or pump with external motor (problem with brush wear, belts, or leaking refrigerant seals)...

Many are pretty expensive compared to the standard units you can buy from your local appliance dealer (can buy more solar panels, inverter, batteries with money saved)... Lastly, check your warranty terms (local dealer nearby for repairs, etc.).

I don't have any DC fridges (other than one old propane one in an RV), but you can read Wind-Sun's editorial about one vendor and issues with the solar / RE refrigeration industry.

-Bill