Published Clips
Looking to the Future: Energy Principles and Technologies
Continued...
The chemical energy stored in the carbon bonds in the fuel oil is released
when the oil is ignited in the power plant’s boiler, converting it to heat energy which is used to boil water to create steam. The steam spins a turbine, converting the heat energy to mechanical energy. The turbine then converts the mechanical energy to electrical energy (we’ll return to turbines and how they work later).So the process in the power plant involves three transformations of the energy with a loss of a portion of the energy at each transformation: from chemical to heat, from heat to mechanical, and from mechanical to electrical energy. In this case, the electrical generation process at Canal Electric is about 35 to 40% efficient; in other words, 60 to 65% of the chemical energy in the #6 fuel oil is lost in this step alone! A significant part of the energy lost at Canal Electric escapes as heat out of the 500 foot stack, along with carbon dioxide, sulfur oxides, nitrogen oxides, and several other substances. Canal electric is a relatively old generation facility; more modern natural gas burners are much cleaner and more efficient, consistently harvesting over 40% of the natural gas’s energy.
Once the electricity is generated in Canal Electric’s turbines, it passes through the power grid, New England’s electricity distribution network, often losing between 8 and 10% of the electrical energy to "line losses." When the electricity finally reaches your home, your electric heater converts the electrical energy back into heat energy to keep you warm. In the end, only a small fraction of the energy that the crude petroleum contained is actually used to warm you as you study environmental science--the vast majority of the energy is lost.
This thought experiment shows that each step, adds more inefficiency to the energy system. As a result, many of the newer energy technologies generate electricity in just one or two steps, often without burning any fossil fuels and without some of the wasteful transformations. These technologies are inherently more efficient since they get rid of the "middleman"--the less you need to change or transport the energy, the less energy is wasted.
Many new energy technologies involve harvesting or generating energy on-site, allowing homes and industries to exist "off the grid." For instance, a house might get heat and hot water from passive and/or active solar thermal energy, harvesting the energy of the sun shining directly on their house, never requiring electricity, heating oil, or natural gas for heat. To generate electricity on-site, some households use a combination of wind and solar power, an efficient way to reduce and often eliminate the need for electricity from the power grid.
Our electricity thought experiment also shows that today’s widely used technologies can be much cleaner and more efficient, conserving our energy resources and minimizing the pollution we produce. It bears repeating that the US consumes and wastes more energy per person than any other nation in the world. According to your textbook, the US comprises less than 5% of the world’s human population yet accounts for more than 20% of the world’s energy consumption. And worse, more than 40% of the energy we use is wasted unnecessarily; we could decrease our energy consumption (and the resulting pollution) by up to 40% simply by increasing conservation and efficiency. Such increases in conservation and efficiency would buy us time to develop and implement alternatives to fossil fuels, hydroelectric dams, and nuclear power and make many of those new technologies more viable since they would need to produce less energy.
The environment isn’t the only reason it’s important to save energy. Massachusetts residents pay a relatively high cost per kilowatt-hour, ranking among the nation’s top ten rate-payers in nine out of the last eleven years (we were eleventh in 1998 and 1999). We consistently pay 2.5 cents above the national average. This may not sound like much, but it adds up to $174 per year for the average Massachusetts household. What other characteristics should we look for in future energy technologies and strategies?
How we harvest and use energy in the future will probably be very different from the way we do it today. For one thing, we will probably not rely on a single source of energy for the majority of our needs. More likely, we will use several different technologies because every alternative to fossil fuels, hydroelectric, and nuclear power is appropriate for some uses and not for others. And for obvious reasons, the most promising alternative energy technologies use infinitely renewable sources of energy, rather than resources that will eventually run out. Those that use potentially renewable resources, such as biofuels made from vegetable products, must be managed wisely.
New energy technologies must provide clean energy that is reliable, affordable, safe, and convenient. Americans are used to having an inexpensive and constant supply of electricity and fuel; they are not likely to use solar power or fuel cells if they don’t provide service that is comparable in cost and convenience to fossil fuels, hydroelectric, and nuclear power. Also, infrastructure such as fueling stations, oil tankers and barges, pipelines, power grids, and power plants already exist with the support of major government subsidies, making many energy producers reluctant to change. So providing safe, uninterrupted, inexpensive service with low maintenance costs has been a major challenge to engineers designing alternative energy technologies to compete in the energy marketplace.
Fortunately, many alternative technologies and conservation measures are now within reach of consumers and industry. And many more are on the way.
How can we generate electricity without using fossil fuels?
Electrical current is simply the flow of charges (either positive or negative) through a conducting material. So any device that will induce electrons to leave their proton partners and move around a conducting metal will generate what physicists call electrical potential, the potential for charges to flow from one side of the metal object to another. For instance, a copper wire conducts electricity because negatively charged electrons can leave their proton partners and move around randomly in the metal wire. We can induce the electrons in our wire to wiggle and move by exposing the wire to a magnetic field; the negatively charged electrons will be attracted to one side of the magnet, leave their proton partners, and move through the copper wire, generating an electrical potential because one part of the wire, at least temporarily, has more negatively charged electrons than the other.Physicists say that the magnet exerts an "electromotive force" on the wire. If we keep the magnet moving near the wire, continuously exciting the electrons, electricity will flow through the wire. If we then complete the circuit by connecting the positive and negative sides of a battery with our wire, electricity will flow through the circuit and the battery can collect the electrical energy our system generates. In this way, we can convert the mechanical energy used to move the magnet into electrical energy in the wire.reaction directly into electrical current.
