Process Description
The GreenFridge process uses outside air, when cold enough, to cool the interior of
electric refrigerators and freezers. A sensor connected to the refrigerator that monitors
the outside temperature, ducts to convey air into the refrigerator from the outside and out
to the outside from the refrigerator, valves to stop air flow through the vents when not in
use, and fans to move the air are the important components of the process.
Electric refrigerators already have sensors that detect the temperature of the
refrigerator cavity. When the temperature rises to a certain point, the refrigeration cycle
is switched on. With the GreenFridge process, if the outside air is cold enough the fan to
bring in air from the outside turns on instead of the refrigeration cycle. The same process
applies to the freezer portion of the GreenFridge.
The important inputs for the GreenFridge process are electricity and cold air. The
output is the cool and cold air in the refrigerator and freezer cavities. The process set
control is the same as in traditional refrigerators, being the desired temperatures of the
cavities, which is controlled to some degree by the user.
Refrigerators have transformed the lives and lifestyles of those who are lucky enough to
own them. Many medicines, notably most vaccines, require refrigeration to retain
potency. By inhibiting bacterial growth, refrigerators also increase the safe shelf life of
many foods (USDA 2005). Freezers provide ice during dangerous heat waves and hot
summers and also preserve food for long periods of time. Refrigeration allows fresh
fruits and vegetables to be shipped all over the world.
Traditional electric refrigerators and freezers depend on chemical refrigerants to
remove heat from inside their cavities. Refrigeration cycles are energy intensive and
inefficient. Given concerns about fossil fuel consumption, greenhouse gas emissions and
global warming, the need to find ways to conserve energy is urgent. The GreenFridge
process allows users in colder climates to reduce their dependence on the refrigeration
cycle during the winter and makes use of the “free” cold outside. Reducing the amount
of electricity used not only can help the environment, it can also lower consumer’s
electric bill at the time when heating costs are the highest.
According to the Second Law of Thermodynamics, heat will not flow from a cold
reservoir into a warmer one unless work is put into the system (Perry 1997). Because of
this, refrigeration cycles are inherently inefficient. The efficiency of new refrigerators
and freezers has increased, but they remain one of the most energy consumptive
appliances in the average household and are responsible for 8% of residential electricity
use in the United States (DOE 2008). Current federal standards limit refrigerator
electricity use to about 725 KWh/year; a typical refrigerator uses about 500 kWh/year
(Energy Star 2008), costing about $50 annually (with electricity costing $0.10/kWh).
Because of inefficiencies of electricity production and transport, energy available
as electricity is only one third of the total energy consumed (DOE 2008). For example, to
produce the 500 kWh to run a refrigerator, another 1000 kWh is lost while creating and
moving the electricity. So a typical refrigerator really consumes about 1500 kWh/year.
As global warming and greenhouse gas emissions become more of a concern,
improving energy efficiency wherever possible is important. As of 2006, residential
electricity production was responsible for the emission of 2,328 Tg of CO2 equivalent
(EPA), meaning that residential refrigerators are RESPONSIBLE for about 66 Tg CO2
Eq., or about 1% of the greenhouse gases produced by the United States. While true that
global warming could decrease the areas where the GreenFridge process would be
practical, …
Additionally, as the price of energy continues to rise, people living in cold
climates are having an increasing difficult time in paying their heating bills. Already,
millions in the northern parts of the U.S. are eligible for government and private
assistance in paying their winter utility bills. The GreenFridge process can lower the cost
of winter electricity bills, leaving more money for households to pay for heat.
Recent years have shown many individuals and companies willing to invest in
energy efficiency. There is a strong market for the GreenFridge process not just in the
United States, but also in Canada and northern Europe where governments have ratified
the Kyoto Treaty and reducing greenhouse gas emissions is required by law.
References Cited
[CDC] U.S. Centers for Disease Control and Department of Health and Human Services.
Vaccine Management: Recommendations for Storage and Handling of Selected
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[DOE] United States Department of Energy. 2008 Buildings Energy Data Book. 2008
Sept [Cited on 30 Sept 2008]. Office of Energy Efficiency and Renewable
Energy. Available from:
*[EIA] United States Energy Information Administration. Annual Energy Outlook 2008
with Projections to 2030. 2008 June [cited on 28 Sept 2008]. Report #:DOE/
EIA-0383(2008). Available from:
Energy Star. Energy Star Qualified Refrigerators & Freezers. 2008 Sept [Cited on 30
Sept 2008]. U.S. Environmental Protection Agency and U.S. Dept of Energy.
Available from:
[EPA] United States Environmental Protection Agency. U.S. Greenhouse Gas Inventory
Reports Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990 – 2006.
2008 April [cited 30 Sept 2008]. USEPA #430-R-08-005. Available from:
Perry, R.H.; Green, D.W. Eds. Perry's Chemical Engineers' Handbook (7th Edition)
McGraw-Hill Co.; 1997.
[USDA] United States Department of Agriculture. Safe Food Handling Fact Sheets:
Refrigeration and Food Safety. 2005 Nov [cited on 28 Sept 2008]. Available