Energy and Health

Why study we study energy when this is a class on environmental health? Simply because energy is needed to improve health. For example, food protection may require the energy of refrigeration. Treatment facilities for air pollution, water pollution, and solid waste all require energy to operate. On the other hand, energy is not just part of the solution, but can be part of the problem. Energy is a unifying cause of environmental health problems. For example, gas, coal, and nuclear power all entail environmental problems.In this section, we provide basic definitions and explain environmental health problems from a thermodynamics perspective. This approach is designed to provide insight into controls, and we will discuss various forms of energy in this regard.

Background

Energy is the capacity to do work. Work is when force is exerted against resistance, and something moves or stops moving. For example, when you push your car uphill, you are doing work. When you push your car and it does not move, you use energy but do not do work. The point here is that energy is necessary for all activities, physical, chemical, and biological. Where does energy come from? If it comes from movement, we call it kinetic energy (for example, a moving car). If it comes from position (relative to other matter), we call it potential energy (for example, car on top of the hill). The car on the hilltop holds gravitational energy, but potential energy is also held in chemical bonds.

Energy has important properties. First, energy moves. For example, radiation is energy in motion. It is energy propagated from a source, that spreads out in pulses (called waves). We measure this energy by wavelength and frequency. The electromagnetic spectrum is the range of wavelengths, which includes cosmic rays, gamma rays, X-rays, U.V., visible light, I.R., microwaves, and radio energy.

A second major property is that energy degrades. High quality energy is easily converted to low quality energy. For example, electricity is readily converted to heat. Low quality energy can be converted to high quality energy, but only by being concentrated. For example, solar energy can be focussed and stored.

Newer technologies

Renewable energy sources, by definition, ultimately cannot be depleted. Thus, there is a great interest in these sources for newer energy technologies. Non-renewables include sunlight, which can be used in two forms. The first is passive solar (for example, deciduous trees can provide shade in summer and protect exposure in winter). The other form is active solar (for example, solar hot water heaters as panels on roofs of houses and buildings). Another example of passive solar is photovoltaics, which convert sunlight to electricity.

Another 'newer' technology is organic matter. For example, producing methanol or methane from organic wastes. Other technologies include wind power. Newer wind machines are more efficient than the windmills of the past. Water power is also being used by harnessing the energy from waves and tides. We have improved the efficiency of hydroelectric power. There is also hydrogen fusion, which will be discussed in a later chapter, and geothermal energy, which taps non-active areas.

The second major category of energy is the non-renewables. This includes not only the traditional fossil fuels, but also includes synfuels. For example, gasified coal is oil from oil shale and coal liquefaction (which is a higher quality energy). Another example is nuclear power. An exception to this is the breeder reactor, which is discussed in a later chapter.

A third strategy for energy consumption is to increase the efficiency of existing sources. This can be done is a variety of ways. For example, cogeneration may use heat from power plants. Superconductivity allows storage and transfer without appreciable energy loss, but requires more powerful electromagnets. Finally, the magnetohydronometer converts heat directly to electricity with high efficiency.

Trends

Globally, if we look at total energy resources we see that energy use has been greatly increasing in this century. Industrial uses dominate energy consumption. Developed countries dominate the use of energy, both by total amount and per capita consumption. The U.S. is #1 by far in energy consumption. We still show relatively poor efficiency, but it has improved since 1970s. Future trends indicate the greatest increase in less developed countries, and also in centrally planned economies.

With renewable resources, less developed countries show the heaviest use in the form of firewood. In developed countries, there is a large demand only in progressive countries. With non-renewable resources, nuclear energy shows an uncertain growth. Fossil fuels represent the heaviest global use, and is heaviest in developed countries. The demand should grow at least until the next century. Oil will decrease, but coal will increase.

In the less developed countries, the demand is low, but less flexible because of limited technology. There is heavy reliance on renewables because they are cheaper. The outlook is that real demand will grow with population. With urbanization, demand for higher quality energy will increase, but not necessarily fossil fuels. Here the crucial issue is a choice of appropriate technology. It should be small scale, cheap, and easily maintained.

Wood, crop residue, and dung represent major sources. Although the data are extremely limited, it is mostly used for non-commercial purposes. Yet, it provides almost 1/2 of energy in developed countries. In rural areas, it provides more than 90% for homes. Overcutting of forests can lead to erosion and desertification. Dung and plant residue provide badly needed nutrients to soil. So, conservation is also important in less developed countries, but for more ominous reasons.