Reduce energy costs with physics

This year’s winter has been worse than recent ones.  Are you worrying about heating bills? When the outside temperature falls below freezing, keeping your house warm and cozy costs money. 

As you know, hot summer days are no different. Keeping your house cool in the summer can also get pricey.

And while many of us accept this as a fact of life, do you ever wonder what can be done to reduce these bills? Understanding the basic physics behind heat transfers can actually give you some ideas that may help you save money.

Heat is a form of energy, and it always transfers from a body of high temperature to one of low temperature.  There are only three ways heat can transfer. Understanding these heat transfer methods actually gives you an idea of how to stop or reduce heat transfers, which can save heat energy and, ultimately, money.

The first method of heat transfer I’ll cover is conduction. Here, you need a medium, which is generally a solid object.  There are some materials which transfer heat more easily than others. Materials which transfer heat energy easily are called conductors, and the substances which resist transferring heat are called insulators.

You want to use good conductors of heat for your frying pan or cooking pot.  Using good conductors helps to cook your food faster. Metals are good conductors of heat, which is why we use metal pot to cook our food. Heat spreads across the bottom and is conducted up to the sides and then directly to whatever you’re cooking.

To stop heat from transferring, you want to use insulators. On cold winter days, you want to wear a woolen sweater which blocks the heat transfer from your body to the cold outside. Some excellent insulating materials are fiberglass, mineral wool, cellulose, polyurethane foam, and polystyrene. These materials are commonly used as insulators in our homes. Other common insulation materials are natural fibers such as hemp, wool, cotton, and straw.

Another method of heat transfer is called convection. This is the method we use to heat our homes.  Here, our atmosphere is either heated or cooled. When air is heated, it begins to expand and become less dense. This less dense air rises, and colder air displaces it. That’s convection.

As warmer air rises, it diffuses its heat and warms the air that’s not as close to the heat source. In order to reduce the heat transfer due to convection, you have to reduce the airflow from your home to the outside. Obviously, keep your doors and windows shut when the heat is on. Some homeowners cover their windows with a plastic film to reduce heat loss as well. 

Radiation is the third heat transfer method.  This is how the sun heats Earth. In this method, there’s no transfer medium; no metal, no air.  Heat radiation travels as electromagnetic waves, or as light waves.  Every object in our universe with a temperature higher than its surroundings emits heat as electromagnetic radiation. 

A large percentage of heat escapes via radiation, and this is pretty difficult to address. Some may use a windshield sun shade--shiny reflecting paper you put in the front windshield of your car-- but I doubt many of us would cover our walls and windows with the stuff all winter long! 

There are other things to consider if you hope to decrease your energy bills. The efficiency of your heating unit is one thing to examine. Electric, gas as well as oil heaters should get regular professional attention. It’s also important to replace air filters. But if you know the basic physics, reducing heat transfer is an easy thing to do in order to save money on your energy bill.



(Dr. Yadav Pandit is an experimental nuclear physicist currently working at Allen Community College as a physical science instructor. He writes a column of general interest in science for the Register.)

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