Energy
Chapter 13

Section 13-1

WHAT IS NET ENERGY AND WHY IS IT IMPORTANT?

Basic science: Net energy is the only energy that really counts
• The usable amount of high-quality energy available from a given quantity of an energy resource is its net energy yield: the total amount of useful energy available from an energy resource minus the energy needed to make it available to consumers. • We can express net energy as the ratio of energy produced to the energy used to produce it. As the ratio increases, the net energy also rises. When the ratio is less than 1, there is a net energy loss.

Net energy ratios for various energy systems over their estimated lifetimes differ widely

Fig. 13-2a, p. 301

Fig. 13-2b, p. 301

Fig. 13-2c, p. 301

Fig. 13-2d, p. 301

Energy resources with low or negative net energy need help to compete in the marketplace
• Any energy resource with a low or negative net energy ratio cannot compete in the open marketplace with other energy alternatives with higher net energy ratios unless it receives financial support from the government (taxpayers) or other outside sources of funding.
– For example, the low net energy yield for the nuclear power fuel cycle is one reason why many governments throughout the world must heavily support nuclear power financially to make it available to consumers at an affordable price.

Section 13-2

WHAT ARE THE ADVANTAGES AND DISADVANTAGES OF FOSSIL FUELS?

Fossil fuels supply most of our commercial energy
• The direct input of solar energy produces several other forms of renewable energy resources that: wind, flowing water, and biomass. • Most commercial energy comes from extracting and burning nonrenewable energy resources obtained from the earth’s crust.
– 87% from carbon-containing fossil fuels (oil, natural gas, and coal). – 6% from nuclear power. – 8% from