Geothermal

Geothermal energy is heat taken from below the surface of the earth in the form of either steam or hot water. This energy can be used to generate electricity, but also has use in heating and cooling homes and some direct uses, such as gold mining, food dehydration, and milk pasteurizing. There are four basic types of geothermal power plants including steam, flash, binary, and enhanced geothermal system (EGS). The first three rely on permeable aquifers that have water flowing through them such that hot water or steam can be extracted. EGS, however, extracts heat from deep in the earth by injecting water and creating artificial fractures in the rock. A great deal of the world’s potential for geothermal energy exists in the so-called Ring of Fire, a ring of volcanoes around the Pacific Ocean.

Solar

There are two basic approaches for using solar energy to generate electricity. The first type, solar photovoltaic (PV) energy, uses semiconductors to convert sunlight into electricity. Crystalline silicon semiconductors are the most common type in use. The second approach is called concentrating solar power (CSP), also referred to as solar thermal. Basically, CSP uses mirrors to concentrate sunlight and generate steam, which is used to power a turbine. The most common method employed commercially is the parabolic trough, where the mirrors are horizontally disposed in a parabolic shape. Solar PV is more commonly used commercially because of high capital costs for building a CSP power plant. Solar PV has experienced rapid growth over the last ten years, increasing by more than twentyfold in the United States. Growth for CSP has increased threefold over the same ten years, but no growth over the last four years. Spain and the United States lead the world in commercial CSP plants.

Coal

Coal has two main energy applications, with about 90% used for electricity generation and 10% used for commercial and residential heating. In terms of electricity generation in the United States, coal is responsible for about 28%, a significant decrease from 53% twenty years earlier when it was the leading energy for producing electricity. There are two primary commercial methods for generating electricity from coal including pulverized coal combustion and fluidized bed coal combustion. To safely burn coal, sulfur, nitrogen, and heavy metals are removed at the electric plant. The sequestering of sulfur and nitrogen are important steps for limiting acid rain and ground level ozone. To generate electricity, the United States has about 360 coal plants with about 790 generators, of which greater than 90% use pulverized coal technology. Most coal is transported by rail.

Ethanol

This chapter examines the use of biomass to make ethanol, or bioethanol, as a transportation fuel. Biomass is defined as any organic material that can be used as a fuel. However, in the United States and Brazil, the two countries that dominate the bioethanol market, most ethanol is produced from corn grain (United States) or sugarcane (Brazil). There has also been research and some commercial trials using cellulosic material, such as corn stover, switchgrass, and sugarcane bagasse, to produce ethanol, but the approach is hindered by high capital and operating costs. In the United States, more than 35% of the total corn production goes towards ethanol production and ethanol makes up about 10% of the gasoline market. Since 2007, the gallons of ethanol produced has more than doubled, and much of this growth has been driven by federal subsidies and mandates.

Fischer-Tropsch Synthesis

The Fischer-Tropsch synthesis is a catalytic polymerization reaction that can be used to make transportation fuels, primarily gasoline and diesel. The process was invented in 1925 and used commercially by Nazi Germany in World War II as well as South Africa, starting in the 1950s. Initially, the fuel of choice to start the process was coal, but recently there has been increased interest in natural gas and biomass. The interest in natural gas is of most interest, as it provides an option for taking stranded natural gas and converting it into a liquid. This avoids the need for pipeline or liquefied natural gas (LNG) transport, which may be difficult to implement due to both geography and geopolitical reasons. The levelized cost of producing gasoline and diesel through this process is competitive with refining, but new commercial implementation has been hindered by the high capital cost of building the plant.

Conclusions

This concluding chapter summarizes some of the information presented for the twelve different energy technologies examined in the book. The first section explores current trends in energy and some of the driving forces affecting these trends. The second section examines the electric vehicle, the bridge that can connect the electric sector with the transportation sector. The third section examines the potential for reducing carbon dioxide (CO2) emissions in the United States by the use of renewable fuels. Following this, a summary of proven and potential reserves is presented for both nonrenewable and renewable energy types. Finally, a summary is presented for the land and energy footprint of each technology.

Wind Energy

A wind farm is a collection of wind turbines, sufficiently spaced to avoid wind interference between turbines. Onshore and offshore are the two basic types of wind farms. The cost of building an offshore farm is greater because of the need for turbines that withstand high wind and corrosive conditions of the sea, plus the expense of installing underwater transmission cables to shore. For an onshore wind farm, the land area for the farm is large, but the direct impact area is relatively small. The direct impact area includes the turbine pads, roads, substations, and transmission equipment, and only makes up about 2% of the total wind farm area. Since the direct impact area is small compared to the total wind farm area, agriculture and ranching can coexist with the wind farm. Wind is a very fast growing renewable energy technology. In the ten years since 2009, the worldwide capacity for wind power increased 276% while US capacity increased 175%.

Introduction

Energy is something we use every day, seamlessly delivered to our home in the case of electricity and abundantly available in the case of gasoline and diesel fuels. Energy has come a long way since the early 1800s, when wood and whale oil were common energy sources. And coal, once a major part of the energy mix in the United States, is being rapidly replaced by natural gas and renewable energy sources, especially wind and solar photovoltaic (PV) energy. China, the most populated country in the world, is still highly dependent on coal, but is also rapidly implementing renewable energy sources. An examination of worldwide energy use shows that for different countries, energy use per capita is correlated with average income. This indicates that an increasing world population coupled with growing economies, especially for China and India, will put pressure on energy availability and cost in the future.

Hydroelectric

There are two methods for generating electricity from hydropower. The first, and by far the most common, is the use of flowing water to rotate a turbine, which then turns the generator shaft to generate electricity. For this type of “conventional” hydroelectric, there are two general approaches. The first is a storage dam, where water impoundment upstream of the dam is used to make a reservoir to store water, thus creating a vertical drop in water elevation and giving control over water flow. The second is a run-of-river scheme, such that a portion of a flowing river is diverted to generate electricity. The second method for generating electricity is called pumped storage. In this scheme, water is pumped from a lower to upper reservoir in order to store energy in the form of gravitational potential energy to be used later. In this respect, the system is operating as a battery to store energy for future use. The states of Washington, California, and Oregon control about half of the total US capacity.

Natural Gas

Natural gas, which is primarily methane, is used in the electric power industry, various industrial applications, residential heating, and, to a small extent, as a transportation fuel. In terms of electricity generation for the United States, natural gas is responsible for about 35%, a large growth from only 15% twenty years earlier. In 2015 natural gas overtook coal and is now the primary energy for producing electricity. It is a relatively clean burning energy type and, compared to coal and petroleum crude oil, it contains small amounts of sulfur and nitrogen and no heavy metals such as selenium, mercury, and cadmium. To support the use of natural gas to generate electricity, the United States has about 1,800 plants with close to 6,000 generators and 1.6 million miles of pipelines.