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Looking to the Future: Energy Principles and Technologies

Part of an inquiry-based alternative energy curriculum module developed for Cape Cod Community College Environmental Technology Program, 2001 as a curriculum consultant.

 

You can think of energy as the ability to do work. All heterotrophic organisms derive chemical energy from the food they eat to do biological work: growing, reproducing, controlling body temperature, moving, avoiding predators, and acquiring more food. Humans, by using technology, have figured out how to use energy from other sources to help them do biological work. For instance, we use heaters and make clothes to keep us warm, drive or fly from place to place powered by engines, and use machines to increase our crop yields. All this technology has made human civilization possible and allowed us to live longer lives. But it comes with a price.

Most of our technologies are powered by fossil fuels: coal, oil, and natural gas. These are non-renewable sources of energy which will eventually run out. In the meantime, our fossil fuel consumption is the main cause of environmental problems such as global warming, acid precipitation, smog, and many types of water and soil pollution. Burgeoning environmental awareness in the 1970s led scientists, especially in the US and Europe, to look for viable alternatives to fossil fuels to meet the majority of our energy needs. The aerospace and transportation industries have also participated in developing new energy technologies. Today, several alternatives to fossil fuels are available to heat our homes, provide electricity for our appliances, power industrial processes, and propel our cars, trains, boats, and planes. In addition, we have made major strides in the area of energy efficiency and conservation, though US citizens continue to consume and waste more energy than the citizens of any other nation, while renewable energy sources account for a tiny fraction of our energy use.

Before we begin looking at the some of these alternative technologies, we need to understand a little about of the physics of energy. Remember that everything we do is constrained by the laws of thermodynamics, so we would do well to keep them in mind when we develop energy technologies.

Where does our energy come from?
Because of the first law of thermodynamics, we must acquire energy since we can never "make” it. Of course sunlight is the only source of energy that is constantly being added to the earth’s system, so solar panels for heat or electricity leap to mind when we think of harvesting the sun’s energy, but many other energy technologies also depend on energy from the sun. For instance, the energy in fossil fuels, most likely the fossilized remains of plants and animals that lived millions of years ago, is actually solar energy that ancient photosynthetic organisms captured and stored in chemical bonds. So when you cozy up to the heater, if it is fueled by oil, coal, or natural gas, you are actually being warmed by solar energy that arrived on the earth many millions of years ago. But remember that in modern times very little energy is being stored in the earth’s crust in this way, so fossil fuels are not being replaced as we use them up: they are non-renewable.

The sun also drives the winds and the water cycle, so when we use hydroelectric dams or windmills to generate electricity, we are actually using solar energy. When we burn wood to keep warm, we are using solar energy stored in the process of photosynthesis.
A few energy sources do not rely on light from the sun. Geothermal technologies use heat from the earth’s mantle to heat water and homes or to generate electricity. Nuclear energy technologies use nuclear fission--splitting atoms apart--to harvest the enormous amount of energy stored in matter itself.

What forms of energy do we need?
Think about the ways you use energy in your home. Chances are that you use electrical energy for many of your energy needs, such as operating appliances, cooling your food, and lighting your rooms. You also use heat energy to warm your home and heat your water. This heat energy may be generated by burning fossil fuels or wood in a furnace or stove, harvested by capturing solar or geothermal energy, or it may be converted from electrical energy in an electric heater. So you use energy primarily in two forms: heat and electricity.

How much energy is lost to entropy?
Efficiency is the percent of available energy that is actually used to do work. For instance, if your car’s internal combustion engine converts 15% of the chemical energy in gasoline into mechanical energy to propel your car along the highway, it is said to have an efficiency of 15%. The remaining 85% of energy is wasted as heat--that is why your car’s engine is hot after you drive it. Every time energy is transformed, some is lost as useless heat (remember the second law of thermodynamics?). So your car’s engine will never be able to convert all of the energy in the gasoline to propel your car; no energy technology can be 100% efficient. But your car can be much more efficient than it is; in recent years, internal combustion engines have been developed that are twice as efficient as older models.

Let’s perform a thought experiment to illustrate the importance of efficiency: Suppose you are using an electric heater in your home. Most traditional methods of generating electricity involve burning fossil fuels, catching falling water, or splitting atoms to power electrical generators. If your heater uses electricity generated at the power plant in Sandwich, the heat it gives off began as chemical energy stored in crude petroleum which was pumped from deep wells and carried in pipelines and ships to a refinery. The drills, pumps, and ships which transport the petroleum all require energy to operate. Refining removes impurities and separates the oil into several useful chemicals; this process requires energy and some of the chemical energy in the fuel itself is lost in refining. After refining, #6 fuel oil, a thick black substance sometimes called bunker fuel, is shipped to Canal Electric, using more energy to run the ship and the pumps.

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