Refrigeration requirements range from uses in health applications (vaccines and medications) to food preservation and comfort (cold drinks). Refrigerators are vital tools in clinics and hospitals, guesthouses, residences (public and private), hotels, restaurants, schools, and other institutions.
If you are in a remote location without access to grid electricity and you need refrigeration, there are a number of technologies you can choose to meet your needs.
When selecting a refrigerator and power system, you need to consider your specific refrigeration needs. Various types of refrigerators use different fuel sources and different amounts of energy.
Before choosing a fridge, you should consider your requirements. Important considerations include the following:
- How large are the items you need to refrigerate? Vaccine refrigerators need very little space, and hence require a relatively small amount of energy. A refrigerator for a restaurant, however, requires a much larger space, which will be much more expensive to cool.
- Do you need freezer space? Freezing takes more energy than simple refrigeration. You should thus consider whether the unit you buy needs to be a combined fridge/freezer, a simple one-compartment refrigerator, or a freezer only.
- How often do you need to access the refrigerator? Frequently accessing the cold space allows heat to enter, and will increase the size and cost of the energy system required to power it.
- How hot is your location? Warmer locations require more energy for refrigeration. You should be able to provide ambient temperatures of your site for system designers.
- Is the requirement critical? When the requirement is absolutely critical, then the power source must be 100% reliable (and over-sized), which increases costs significantly. A refrigerator storing critical vaccines would need 100% reliability, while a household fridge storing food would not.
Table 1: Typical Refrigeration Applications
|Application||Freezer (space required liters)||Volume required (liters)||Critical/non-critical|
|Vaccine refrigeration||0-5 l||30 liters||Yes|
|Institutional & commercial food preservation||50-550 liters||200-1000 liters||Yes|
|Institutional & commercial drinks, etc. cooling||N/A||200-300 liters||No|
|Dedicated freezing (institutional or commercial)||500-1000 liters||N/A||Yes|
|Household refrigeration/freezing||15-250 liters||200-550 liters||No|
Essentially, there are 2 approaches to off-grid cooling and refrigeration. Table 2 summarizes refrigeration choices and the most appropriate off-grid energy sources for each.
The first approach is self-powered, self-contained refrigerator units powered by LPG/kerosene or PV. This is most appropriate with small isolated refrigeration requirements.
The second approach is to drive refrigerators/freezers as part of an energy system with electricity supplied from PV, diesel, or petrol generators, wind turbines, water turbines, or other renewable energy sources. This is most appropriate when you have large refrigeration requirements or when you have other appliances you need to power in addition to fridges.
Table 2: Refrigerator type, power consumption and appropriate power sources
|Fridge Type||Monthly Fuel/Energy Consumption||Appropriate Off-Grid Power Source|
Operate on heat cycle which requires fuel or electric heat source
|Option 1: Gas fridges
(Electrolux, Servel Propane)
|24-30 l/propane/ standard 300l unit||LPG gas|
|Option 1: Kerosene fridges
|15-30 [??] liters per 40-150 l/mo for a 300 l unit. There is a wide range in quality||Kerosene fuel|
Operate using compression cycle which requires electricity
|Option 2: Super-Efficient 12 V DC HH fridges
(i.e. Sunfrost, Vestfrost, Nova Kool)
|10-60 kWh/ 300l unit||PV
|Option 3: Vaccine fridges
|Option 4: Standard Commercial fridges
(Bosch, Siemens, Electrolux, Frigidaire, etc.)
|110 kWh/mo or 300l unit more||Generator/Hybrid System|
|Option 5: Evaporative fridges
Operate on evaporative cooling effect
Option 1: Kerosene or LPG Absorption Fridges
Absorption refrigerators operate on a heat cycle normally powered by a kerosene or gas burner. A flame or heat element powers the heating cycle, which creates the cooling effect. Because of their high energy consumption, PV should never be used to power absorption fridges.
Kerosene and LPG fridges may present a fire hazard, and kerosene fridges emit particulates (and/or gases) which may make them inappropriate in some situations Several studies recommend PV or LPG fridges over kerosene fridges for vaccine use.
Kerosene and LPG absorption refrigerators are available throughout the tropics and in both the developing and the developed world. Both types are available in standard sizes (e.g., 300 – 600 liters for cooling, 50 – 100 liters for freezing). They can be used in isolated clinics, hospitals, schools, restaurants, cafes, butcheries, hotels, homes, and camps.
Kerosene fridges are ordinarily refilled with fuel on a weekly basis, while LPG fridges are refilled on a more intermittent basis. Kerosene/paraffin is widely and relatively easily available. LPG poses far more difficulties, particularly in rural and remote situations. LPG bottles must be purchased, and supplies are often irregular outside urban areas.
Spare Parts and Service
Kerosene/paraffin and LPG refrigerators are relatively reliable. Kerosene fridges require their wicks and mantles to be changed or adjusted regularly and hence need frequent attention (though not by highly skilled technicians).
Kerosene refrigerators also need to be cleaned regularly because of the soot build-up in the exhaust flue. LPG refrigerators have far fewer maintenance requirements. Note that finding spare parts for either type of fridge can be problematic in some locations.
Absorption fridges are best where self-contained units are necessary. Kerosene-powered units are better in many remote situations because of kerosene’s wide availability. However, kerosene refrigerators should be avoided unless: (1) LPG is not available, and/or (2) spare parts and maintenance for PV fridges are not available. LPG is better where gas supplies are readily available.
Option 2: Efficient Household Fridges and Freezers
Low voltage super-efficient 12 V DC (direct current) fridges for off-grid applications are available in a number of sizes (though they typically have less capacity than standard AC fridges).
These fridges are also available for 240 VAC, but 12VDC is generally preferable for PV and RET systems. Such fridges have very thick insulation, and often place the heat-generating compressor unit above the unit to save energy.
Efficient household refrigerators and freezers are increasingly common on the world market. However, they are still specialty items that are produced only in a few countries in Europe and North America. They can be sourced from catalogs and specialist retailers.
DC fridges need to be powered by a battery set that is charged by PV, wind, a genset or another RET. Correct sizing of the battery set, and the PV or wind power system is absolutely critical.
Technology Spare Parts and Service
Battery spares should be available. Critical spares for the fridges (compressor, etc) and energy systems should be available as long as electric fridge maintenance expertise.
Efficient fridges/freezers are optimal for institutional, commercial, or domestic uses in areas with good wind or solar energy supplies, and where consumers have enough funds for large upfront capital costs.
Low power, 12VDC refrigerators can easily be powered by simple PV systems with regulators and batteries. Wind, hydro or small gensets with battery sets can also be used for power supply. They can easily be incorporated into existing 12 VDC RET systems.
Option 3: PV Vaccine Fridges
For vaccine storage and medical uses, the World Health Organization’s Global Programme for Vaccines and Immunization and its Expanded Programme on Immunization/EPI has approved several low voltage DC PV vaccine refrigerators.
Solar vaccine refrigerators are designed specifically to meet health needs, and are not appropriate for private use (e.g., refrigerating food and drink). EPI Vaccine refrigerators are made to be powered by PV and are available as complete kits from a variety of distributors.
The WHO has certified a number of models from companies in the world for their GPV/EPI programs. PV fridges and freezers are generally only available on order from source manufacturers.
Most areas in the tropics have sufficient solar energy availability for PV vaccine refrigeration systems. Individual systems may have to be designed based on the particular needs of the clinic or health program.
Technology Spare Parts and Service
Battery spares should be available. Critical spares for the fridges (compressor, etc) and energy systems should be available. Systems should be checked by a qualified technician two times per year.
Off-grid rural health clinics and hospitals with more than 4 kWh/m2/day of solar radiation. Note that there must be sufficient technical infrastructure and manpower in place to service, monitor, and maintain the fridges. In cases where infrastructure is insufficient, consider LPG or kerosene fridges.
Option 4: Conventional Household and Commercial Fridges
Conventional fridges are readily available in a number of sizes and fridge/freezer configurations. They run on standard 240/120V AC power. They are not good choices for off-grid locations, as they generally consume too much power for RET systems to supply. In addition, wind and PV systems require inverter/battery systems.
Therefore, conventional fridge/freezers require generators to run continuously.
Where large power systems are already in place (especially when the energy system is oversized), it may make economic and practical sense to buy a commercial refrigerator. When choosing standard units, pay careful attention to energy consumption specifications, and do not choose units with power consumption above 1 kW.
With diesel or petrol gensets, require constant power availability (i.e. genset must be run continuously!) and therefore fuel must be regularly available. For RET applications, you must have an inverter and battery source.
Technology Spare Parts and Service
Critical spares for fridges (compressor, etc) and energy systems should be available. Constantly running gensets will require regular servicing.
Commercial fridges are best used where there is an over-capacity in power supply, where power is constantly available. A genset of about 1.5 kVA would be a minimum for a small refrigerator if no other applications are in use. PV arrays or wind generators might provide additional power, but in general would not be economical as a sole power source unless the site is unreachable by diesel/petrol suppliers.
Evaporative fridges are a relatively well-tested, proven, low-tech approach to cooling, which cool produce, other food, and beverages at about 15-20°C below ambient temperatures.
They are most appropriate in hot, dry (not humid) climates where there are no other alternatives, and cannot be used for critical purposes such as vaccine storage.
Table 3: Indicative Cooling and Refrigeration Technologies and Costs (US$)
|Item||Avg capital cost||PV power System Cost||Running, O&M costs pa||Lifetime years||Life cycle cost|
|Option 1: Kerosene fridge/freezer (300 l fridge, 50 l freezer)||$1,500||N/A|
|Option 1: LPG fridge/freezer (300 l fridge, 50 l freezer)||$1,300||N/A|
|LPG/Kerosene Freezer (240 l)||$1,800-2,200||N/A|
|Option 2: Efficient 12 V HH fridge/freezer (300 l fridge, 50 l freezer)||$2,500|
|Option 3: Vaccine refrigerator (30 l)||$900-1,400|
|Option 4: Commercial fridge 300l fridge, 50 l freezer, 240 V AC||$500-1,200|
|PV freezer (250 l)||$1,500|
Cooling, Refrigeration, and Freezing
Refrigerators are in increasing demand in rural areas for domestic and institutional requirements. However, powering refrigerators is surprisingly complicated and expensive. Refrigeration requires relatively constant energy input and the most common 240 VAC models are not suited for off-grid situations.
Specially made efficient off-grid refrigerators are available, but will usually cost more than US$1000 per unit. When powering off-grid refrigerators with electricity, plan to pay as much (or more) for the power source as you do for the refrigerator itself.