Solar powered refrigerator
Encyclopedia
Solar-powered refrigerators may be most commonly used in the developing world to help mitigate poverty
and climate change
. By harnessing solar energy, these refrigerator
s are able to keep perishable goods such as meat and dairy cool in hot climates, and are used to keep much needed vaccines at their appropriate temperature to avoid spoilage. The portable devices can be constructed with simple components and are beneficial for areas of the developing world where electricity is unreliable or non-existent.
depletion and global warming
. Refrigerators which contain ozone depleting and global warming substances such as chlorofluorocarbons (CFC’s), in their insulation foam or their refrigerant cycle are the most harmful. After CFC’s were banned in the 1980’s they were replaced with substances such as hydrochlorofluorocarbons (HCFCs), which are ozone depleting substances and hydrofluorocarbons (HFCs). Both are environmentally destructive as potential global warming chemicals. If a conventional refrigerator is inefficient or use inefficiently, it will also contribute more to global warming than a highly efficient refrigerator. The use of solar energy to power refrigeration strives to minimize the negative impacts refrigerators have on the environment.
Most battery-free solar refrigerators will simply use ice or another phase change material to store the energy required for cooling. This can practically provide limited cooling for a day or so but with no control over the temperature or the cooling rate this is not suitable for delicate payloads like vaccine.
In order to solve this problem new technology such as Sure Chill developed in the UK and the SunDanzer Direct Drive technology are available. Vaccine refrigerators using Sure Chill and Direct Drive technology have demonstrated outstanding performance by keeping vaccines at stable temperatures for two weeks with no power even at an ambient temperature of 32C.
and convection
, requires no electricity and can be made for commonly available material such as cardboard, sand and recycled metal. The device is composed of two cylinders. The inner metal cylinder is fitted inside the outer cylinder which can be made from what ever the person has access to including wood or plastic. Space is left between the inner and outer chamber to be filled with organic material which can include sand, wool or soil that is then saturated with water. As heat from the sun evaporates the water, the inner chamber cools reducing and maintaining the temperature at 43 °F (6.1 °C).
, Namibia
, and South Africa
in areas where electricity is often not readily accessible to help preserve perishable foods such as meat and dairy, however, is not yet being used for vaccines. It is easily transported and reduces negative environmental impacts but is limited by size and requires the availability of water.
Poverty
Poverty is the lack of a certain amount of material possessions or money. Absolute poverty or destitution is inability to afford basic human needs, which commonly includes clean and fresh water, nutrition, health care, education, clothing and shelter. About 1.7 billion people are estimated to live...
and climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
. By harnessing solar energy, these refrigerator
Refrigerator
A refrigerator is a common household appliance that consists of a thermally insulated compartment and a heat pump that transfers heat from the inside of the fridge to its external environment so that the inside of the fridge is cooled to a temperature below the ambient temperature of the room...
s are able to keep perishable goods such as meat and dairy cool in hot climates, and are used to keep much needed vaccines at their appropriate temperature to avoid spoilage. The portable devices can be constructed with simple components and are beneficial for areas of the developing world where electricity is unreliable or non-existent.
Environmental Impacts of Refrigerators
There is major environmental concern regarding conventional refrigeration technologies including contribution to ozone layerOzone layer
The ozone layer is a layer in Earth's atmosphere which contains relatively high concentrations of ozone . This layer absorbs 97–99% of the Sun's high frequency ultraviolet light, which is potentially damaging to the life forms on Earth...
depletion and global warming
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
. Refrigerators which contain ozone depleting and global warming substances such as chlorofluorocarbons (CFC’s), in their insulation foam or their refrigerant cycle are the most harmful. After CFC’s were banned in the 1980’s they were replaced with substances such as hydrochlorofluorocarbons (HCFCs), which are ozone depleting substances and hydrofluorocarbons (HFCs). Both are environmentally destructive as potential global warming chemicals. If a conventional refrigerator is inefficient or use inefficiently, it will also contribute more to global warming than a highly efficient refrigerator. The use of solar energy to power refrigeration strives to minimize the negative impacts refrigerators have on the environment.
History of Solar Refrigeration
"In developed countries, plug-in refrigerators with backup generators store vaccines safely, but in developing countries, where electricity supplies can be unreliable, alternative refrigeration technologies are required”. Solar fridges were introduced in the developing world to cut down on the use of kerosene or gas-powered absorption refrigerated coolers which are the most common alternatives. They are used for both vaccine storage and household applications in areas without reliable electrical supply because they have poor or no grid electricity at all. They burn a liter of kerosene per day therefore requiring a constant supply of fuel which is costly and smelly, and are responsible for the production of large amounts of carbon dioxide. They can also be difficult to adjust which can result in the freezing of medicine. There are two main types of solar fridges that have been and are currently being used, one that uses a battery and more recently, one that does not.Most battery-free solar refrigerators will simply use ice or another phase change material to store the energy required for cooling. This can practically provide limited cooling for a day or so but with no control over the temperature or the cooling rate this is not suitable for delicate payloads like vaccine.
In order to solve this problem new technology such as Sure Chill developed in the UK and the SunDanzer Direct Drive technology are available. Vaccine refrigerators using Sure Chill and Direct Drive technology have demonstrated outstanding performance by keeping vaccines at stable temperatures for two weeks with no power even at an ambient temperature of 32C.
Technology
- Conventional motor compressor refrigerator powered by solar photovoltaic produced electricity.
- ThermoelectricThermoelectric coolingThermoelectric cooling uses the Peltier effect to create a heat flux between the junction of two different types of materials. A Peltier cooler, heater, or thermoelectric heat pump is a solid-state active heat pump which transfers heat from one side of the device to the other side against the...
solid-state refrigerator powered by solar photovoltaic electricity. - Absorption refrigeratorAbsorption refrigeratorAn absorption refrigerator is a refrigerator that uses a heat source to provide the energy needed to drive the cooling system...
in which the boiler heat is generated from concentrated sunlight. - Stirling engineStirling engineA Stirling engine is a heat engine operating by cyclic compression and expansion of air or other gas, the working fluid, at different temperature levels such that there is a net conversion of heat energy to mechanical work....
refrigerator in which the compressor is mechanically driven by a Stirling engine.
Battery Supplemented Solar Refrigerator
Traditionally solar-powered refrigerators and vaccine coolers use a combination of solar panels and lead batteries to store energy for cloudy days and at night in the absence of sunlight to keep their contents cool. These fridges are expensive and require heavy lead-acid batteries which tend to deteriorate, especially in hot climates, or are misused for other purposes. In addition, the batteries require maintenance, must be replaced approximately every three years, and must be disposed of as hazardous wastes possibly resulting in lead pollution. These problems and the resulting higher costs have been an obstacle for the use of solar powered refrigerators in developing areas.Portable Solar Powered Fridge
A Portable solar powered fridge has been produced for use in the developing world. The basic design uses the principle of evaporation. The fridge is solar powered, but does not require solar panels, and can be made from basic household material lowering the cost and making access to the developing world easier. Without using any power the fridge can keep perishable at a temperature of 6 degrees Celsius for days. Also see zeer.How it works
The refrigerator employs a combination of heat conductionHeat conduction
In heat transfer, conduction is a mode of transfer of energy within and between bodies of matter, due to a temperature gradient. Conduction means collisional and diffusive transfer of kinetic energy of particles of ponderable matter . Conduction takes place in all forms of ponderable matter, viz....
and convection
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
, requires no electricity and can be made for commonly available material such as cardboard, sand and recycled metal. The device is composed of two cylinders. The inner metal cylinder is fitted inside the outer cylinder which can be made from what ever the person has access to including wood or plastic. Space is left between the inner and outer chamber to be filled with organic material which can include sand, wool or soil that is then saturated with water. As heat from the sun evaporates the water, the inner chamber cools reducing and maintaining the temperature at 43 °F (6.1 °C).
Usage
The portable solar fridge is used in areas of Africa such as ZambiaZambia
Zambia , officially the Republic of Zambia, is a landlocked country in Southern Africa. The neighbouring countries are the Democratic Republic of the Congo to the north, Tanzania to the north-east, Malawi to the east, Mozambique, Zimbabwe, Botswana and Namibia to the south, and Angola to the west....
, Namibia
Namibia
Namibia, officially the Republic of Namibia , is a country in southern Africa whose western border is the Atlantic Ocean. It shares land borders with Angola and Zambia to the north, Botswana to the east and South Africa to the south and east. It gained independence from South Africa on 21 March...
, and South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
in areas where electricity is often not readily accessible to help preserve perishable foods such as meat and dairy, however, is not yet being used for vaccines. It is easily transported and reduces negative environmental impacts but is limited by size and requires the availability of water.
See also
- Renewable energy in developing countriesRenewable energy in developing countriesMost developing countries have abundant renewable energy resources, including solar energy, wind power, geothermal energy, and biomass, as well as the ability to manufacture the relatively labor-intensive systems that harness these...
- Solar power in South AsiaSolar power in South AsiaRenewable energy is a viable means of generating energy in Asia.For solar power, South Asia has the ideal combination of both high solar insolation and a high density of potential customers....
- UN-EnergyUN-EnergyUN-Energy is an interagency mechanism within the system of the United Nations related to energy. It was created after the 2002 World Summit on Sustainable Development in Johannesburg, and its purpose is to create a coherent approach towards a sustainable energy system especially in developing...
- SolarAidSolarAidSolarAid is a British international development charity that promotes the use of solar energy to help reduce global poverty and climate change. SolarAid installs solar photovoltaic systems, for community centres, medical clinics, schools and other communal buildings. It also trains local...
- Solar vaccine refrigeration in developing countries
- Batteryless Solar Vaccine Refrigerator
- SunDanzer battery free vaccine refrigerators