14.4 Nuclear Energy FIGURE 16: Structure of the atom

Uranium atoms that undergo fission release additional neutrons, causing additional fission and heat. Understanding Nuclear Fission

FIGURE 18: Nuclear fission

Understanding Nuclear Fission The chain reaction in a nuclear reactor is kept from running rampant by: – bathing the reactor core with water – using control rods – maintaining the proper concentration of the fuel in the fuel rods Courtesy of Mark Marten/U.S. Department of Energy

FIGURE 19: Anatomy of a pressurized nuclear power plant

FIGURE 26: Nuclear reactions in a breeder reactor

FIGURE 27: Two types of fusion reactions Helium- 3 2 protons, 1 Neutron Mass = ~3 amu

Although it is the most expensive of the major sources of electricity, it fits well into the established electrical grid and produces very little air pollution. Nuclear Power: The Benefits FIGURE 21: The containment building of a nuclear power plant © Corbis/age fotostock

Interest in nuclear power has declined substantially because of major problems, among them: – questions over reactor safety – unresolved waste disposal issues – low social acceptability – high costs Nuclear Power: The Drawbacks

The effects of radiation on human health depend on many factors, such as: – amount of radiation – length of exposure – type of radiation – half-life of the radionuclide – age of the individual – the part of the body exposed Nuclear Power: The Drawbacks

FIGURE 23: Relative Cancer Risks

Several major accidents at nuclear power plants have raised awareness of the potential damage a small mechanical or human error might cause. Estimates suggest that many additional accidents are bound to occur in the future, with costly social, economic, and environmental impacts. Nuclear Power: The Drawbacks FIGURE 24: The Chernobyl Number 4 Reactor after the explosion Courtesy of U.S. Department of Energy

Nuclear power has become a socially unacceptable form of electricity in part because of high costs during all phases of operation, from construction to operation, repair, and retirement. Countries with nuclear power plants can develop atomic bombs from waste products. Nuclear Power: The Drawbacks

FIGURE 27: Two types of fusion reactions Helium- 3 2 protons, 1 Neutron Mass = ~3 amu

Geothermal Energy The Nesjavellir Geothermal Power Plant in Þingvellir, Iceland Þingvellir

Geothermal Heating And Cooling Systems Heating and cooling homes and businesses using the relatively constant temperature of the earth are referred to as Geothermal heating and cooling or Geoexchange.Geothermal Geoexchange These systems take advantage of the more or less constant temperature found below the ground to transfer heat into the building in the winter and transfer heat out of the building in the summer.

How Geothermal Heating and Cooling Work The device used to accomplish this exchange is called a geothermal heat pump. (It is also referred to as a Ground Source Heat Pump.)Ground Source Heat Pump It operates just like a regular air to air heat pump, except instead of using air as the heat exchange medium; it uses a heat transfer fluid, usually water with an antifreeze solution. This fluid is circulated through a closed loop system of tubes buried in the ground either in long trenches or deep well-like vertical bore holes.

Ground Source Heat Pumps offer great benefits: Can be a combination heating/cooling and hot water heating system Some can save you up to 50% on your water-heating bill by preheating tank water Made of mechanical components that are either buried in the ground or located inside the home About the same size as a traditional heating/cooling unit Can cut energy consumption by 20 to 50% and reduce maintenance costs Keep the air warmer in the winter ( ¡ F) and at a more consistent temperature throughout the home, eliminating the hot and cold spots common with other systems Very quiet, providing a pleasant environment inside & outside the home No noisy fan units to disturb outdoor activities No exposed equipment outdoors; children or pets cannot injure themselves or damage exterior units No open flame, flammable fuel or potentially dangerous fuel storage tanks

GSHPs are environmentally friendly: Conserve natural resources by providing climate control efficiently and thus lowering emissions Minimize ozone layer destruction by using factory-sealed refrigeration systems, which will seldom or never have to be recharged Uses underground loops to transfer heat, with no external venting and no air pollution

Economic Incentives for renewables, including geothermal ?re=1&ee=1&spv=0&st=0&srp=1&state=TX

14.5 General Guidelines for Creating a Sustainable Energy System Creating a sustainable energy future will require a careful analysis of options for such factors as:

TABLE 2: Energy Quality of Different Forms of Energy

14.6 Establishing Priorities Short-term goals (within 10–20 years) – In the near term, efforts are needed to: improve the efficiency of all energy-consuming technologies find sustainable alternatives to coal, crude oil, and their derivatives Long-term goal (within 50 years) – In the long term we must find sustainable replacements for natural gas.