By N. Domitrovich & Z. Nevado

The process of refrigeration is defined by the cooling of a space or material below room temperature to preserve and prolong the shelf life of perishables. Over the last 150 years, this has been adapted to the current needs of the consumer – from the ancient technique of ice harvesting and underground storage to today’s refrigerator with improved efficiency, kitchen design integration, and advanced technological features.  With 145 million units in the U.S., accounting for 5% of household energy usage, continued improvement in refrigerator efficiency is necessary.  Here you will find our design for the refrigerator of the future…

History

Refrigeration began in ancient times with Hebrews, Greeks, and Romans placing large amounts of snow into underground pits and covering it with insulating material such as hay, wood, or animal skin.  Egyptians filled jars with boiled water and let it cool by exposing it on the rooftop.  The first known modern artificial refrigeration was demonstrated by Scottish inventor, William Cullen, in 1756.  He used a pump to create a vacuum over a container of a boiled chemical called diethyl ether which absorbed heat from the surrounding air.  This was improved upon by General Electric when they designed the first refrigerator to gain popularity, which like all the other refrigerators at that time, used harmful and toxic chemicals such as sulfur dioxide or ammonia which caused loss of vision, skin burns, or even death when inhaled or ingested.  The invention of Freon (CFC , chlorofluorocarbon) in the 1920s further catapulted this industry by providing a much safer and more efficient refrigerator.

Refrigerators did not go into mass production for residential use until after World War II.  Innovations like automatic defrosting and ice makers occurred during the 1950s and 1960s.  In the 1970s, Freons were banned from cooling equipments as it was found to have adverse effects on the ozone layer.  Over the past sixty years, numerous styles such as the bottom-drawer, side-by-side, and French door refrigerator/freezer have been developed using different materials such as porcelain, plastic, and stainless steel.  In 1992, ENERGY STAR, a joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy was created to help the consumers save money and protect the environment through energy-efficient products and practices. Through this label, consumers are now more aware of the developments and impacts of energy-consuming products, refrigerators being one of them, to the environment.

Refrigerator Efficiency Today

Thanks to technological improvements and the work of ENERGY STAR, today’s refrigerator is approximately 80% more efficient than one from the 1970s.  This is mainly due to major improvements in insulation, compressors and temperature controls. Below are some current facts about refrigerator efficiency.

Energy efficiency has increased 25-40% each decade since the 1970s:

  • 1970 to 1980: 37% increase
  • 1980 to 1990: 40% increase
  • 1990 to 2000: 32% increase
  • 2000 to 2010: 27% increase

Today there are 145 million refrigerators in the U.S. which account for 5% of household energy usage:

  •  30% are ENERGY STAR qualified
  • 35% are older than 10 years old
  • 20% are second units

Side by Side refrigerators models are the least efficient

  • Bottom freezer models use approximately 16 percent less energy
  • Top freezer models use about 13 percent less energy

Through-the-door icemakers and water dispensers are not as efficient as you may think:

  • Reductions in the need to open the door save energy, however, these features increase energy usage by 14-20%

 What’s Next?

 There is a great interest in drawer-type refrigeration, driven by the concept of accessibility, ability to control temperature for specific food separately, and the compactness of the unit which is beneficial for small, urban spaces. Since drawer refrigerators are fairly new, cost-effectiveness is one of the major drawbacks of it, as studied by Consumer Reports. However, as the technology improves, the cost will go down and we believe that these drawers represent the future of refrigerators. One design particularly of interest is “Celsius” a unit that received an Australian Design Award in 2009, developed by Angeline Meloche, a design student from University of New South Wales. The modular refrigerator is equipped with an LCD screen for food monitoring, five preset temperature controls which can also be adjusted based on the consumer’s needs, and adjustable feet and rubber hand grips for ease on transportation and drawer configuration, in addition to compliance to the current energy efficiency standards.

Other advances in refrigeration may involve alternative energy sources and materials. For example, student Emily Cummins designed a solar-powered refrigerator that is based on evaporation. The system is composed of two cylinders.  The outer cylinder is made of any solid material, allowing for an opportunity to use recycled or naturally-found materials and the inner cylinder is made of metal. The gap between the two cylinders is filled with sand or soil that is soaked with water.  In hot weather, the water evaporates, removing heat and keeping the inner cylinder at a cool temperature. This has proven to be a cheap and efficient way to introduce refrigeration to developing countries.

NYSID’s Refrigerator of the Future

In the continued attempt to improve the energy efficiency of the refrigerator, we have added some design features to the drawer model refrigerators already in the market.  We believe this is the model of the future.  As discussed in the previous section, the drawer model design decreases both the energy cost and functionality of the appliance.  Outlined below are a few additional features which we believe should be added to these refrigerators of the future.

Sketchup Model designed by N. Domitrovich

Feature:  UPC reader scans items when moved into and out of drawers.
Energy Efficiency:  Ability to keep track of inventory, dates, and usage trends means less waste.  This will also make it so that it is not necessary to open the door to take inventory when going to grocery store.  In the case where too many items are in a drawer, this inventory can be displayed in list format on the screen.

Feature:  Ability to turn off drawer with a click of a button
Energy Efficiency:  When a drawer is not needed it can simply be turned off and not use up energy.  Often people buy refrigerators larger than they need for those special occasions (holidays, parties, etc).  Instead cooling that space year round, it could be done for the few times a year it’s actually needed.

Feature:  Linked to online grocery store (such as http://www.freshdirect.com)
Energy Efficiency:  Items added to grocery cart automatically (via UPC scanner), making for less frequent trips to the grocery store due to forgotten items.  Groceries can also be delivered to many people in same area at the same time, introducing economies of scale and reducing the amount of gas used going to and from grocery store.

The Mechanics

Photo Courtesy of How Stuff Works

The basic principle behind refrigeration is the Law of Thermodynamics. Refrigerators use a continuous cycle that reuses a chemical coolant to keep the unit below room temperature. As previously mentioned, the use of chemicals used as coolants have evolved from the toxic to safer and more environmental-friendly solutions. Currently, the main coolant used is a type of gas HFC-134a, also called tetrafluoroethane. HFC turns into a liquid when it is cooled to -15.9 degrees Fahrenheit (-26.6 degrees Celsius). The refrigeration process, explained by howstuffworks is as follows:

  • The compressor compresses the gas and the compressed gas heats up as it is pressurized (orange).
  • The coils on the back of the refrigerator let the gas dissipate its heat.
  • The gas condenses into liquid (dark blue) at high pressure.
  • The high-pressure liquid flows through the expansion valve.

On one side of the hole is high-pressure liquid and on the other side of the hole is a low-pressure area (because the compressor is sucking the gas out of that side).

  • The liquid immediately boils and vaporizes (light blue), its temperature dropping to -27 F. This makes the inside of the refrigerator cold.
  • The cold gas is sucked up by the compressor, and the cycle repeats.

Bibliography

Refrigerator. Retrieved from: http://en.wikipedia.org/wiki/Refrigerator

Krasner-Khai, B. (February/March 2011). The Impact of Refrigeration. History Magazine. Retrieved from:  http://www.history-magazine.com/refrig.html

Brain, M. How Refrigerators Work. Retrieved from: http://home.howstuffworks.com/refrigerator.htm

(August 2007). Refrigerator Drawers Slide into the Home. Retrieved from: http://www.consumerreports.org/cro/appliances/kitchen-appliances/refrigerator-drawers/refrigerator-drawers-10-06/overview/1006_refrigerator-drawers_ov.htm

Celsius. Retrieved from: http://student.designawards.com.au/application_detail.jsp?status=2&applicationID=4081

(10/29/2009). U.S. Department of Energy: ENERGY STAR Qualified Refrigerators Partner Resource Guide.  Retrieved from: http://www.energystar.gov/ia/partners/manuf_res/downloads/Refrigerator_PRG.pdf

(2005).  U.S. Energy Information Administration: Residential Energy Consumption Survey. Retrieved from: http://www.eia.doe.gov/emeu/recs/recs2005/c&e/detailed_tables2005c&e.html 

(2005).  U.S. Energy Information Administration: Residential Energy Consumption Survey. Retrieved from: http://www.eia.doe.gov/emeu/recs/recs2005/c&e/detailed_tables2005c&e.html

(February 2009). Student Invents Solar-Powered Fridge for Developing Countries. Retrieved from: http://www.solarpowerwindenergy.org/2009/02/04/student-invents-solar-powered-fridge-for-developing-countries/

 

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