Alternative Energy Sources

The use of energy defines the beginning of human civilization: when the prehistoric human mastered the use of fire for domestic comfort and cooking, human civilization began and evolved to reach the age of the locomotive, the nuclear power plant, the automobile, the airplane, the personal computer and the wireless internet. Throughout the centuries, the human society has evolved by increasingly using energy to the point where the consumption of energy is necessary for the functioning of the contemporary society, the prosperity of the nations and the survival of our civilization. Energy is produced and is being used in different forms: airplanes and automobiles use liquid hydrocarbon fuels; electric power plants convert primarily the energy in coal, natural gas, nuclear and hydroelectric into electricity; and a contemporary household uses electricity and natural gas for domestic comfort, entertainment and the preparation of meals. Because most functions of our society are based on the use of energy, elaborate networks of energy supply have been developed in the last three centuries: electricity is fed into communities by the transmission lines of the electric grid at high voltage; natural gas by a complex system of pipelines, which transcend national boundaries; and tanker ships crisscross the oceans daily to supply crude oil to refineries. The economic impact of the energy supply and the energy trade is of paramount importance to all nations. The geopolitical activities of most modern nations are significantly influenced by their need for a constant and secure energy supply. Most of modern wars (those after 1950) have been fought for the control and security of energy supplies and many treaties and international agreements have been cemented with energy resources as the primary issue. This is a general chapter on energy, not just alternative energy, which explains in a quantitative way what is the quantity we call “energy,” whence it comes and where it goes. The forms that energy is produced and consumed are, first, explained. The several units that are commonly used for different energy forms and quantities are listed and their equivalencies are explained. Secondly, the importance of energy in the economic activities of the contemporary society is described qualitatively and the primary energy resources are identified. The current energy trade between groups of nations is also described briefly and the main flow of primary energy resources is identified. Thirdly, historical data on energy production and consumption in several groups of nations are offered as well as some acceptable predictions for the future demand and supply of energy.

The exponential increase of energy consumption, since the beginning of the industrial revolution, has produced significant changes in the global environment, chief among which is the increase of the average concentration of carbon dioxide in the atmosphere from 280 ppm in 1750 to more than 390 ppm in 2011. Climatologists predict that this change will cause an increase of the average temperature of the planet as well as regional and global and climatic changes. Other significant environmental effects of energy consumption are: the several ecological problems caused by acid rain, which has threatened in the past the ecosystems of several lakes and rivers; lead contamination of the atmosphere; nuclear waste, which is produced by the more than 430 nuclear power plants in continuous operation worldwide; and, the waste heat rejection by all thermal power plants, which is accompanied by fresh-water consumption. Environmental threats are neutralized by public policy, either national policy or concerted international efforts and protocols that are ratified by several countries. Despite the efforts of the environmental community, there is not yet a global agreement for the mitigation of the effects of high carbon dioxide concentration, which poses the principal environmental threat of the twenty-first century. The problem of nuclear waste is being addressed at several national and regional levels and it appears that solutions for the long term storage of radionuclides will become available in the near future. National public policies and international collaboration has almost solved the acid rain and lead contamination problems. The two are viewed as success stories stemming from international collaboration and successful public policy. This chapter starts with a short section on the environment and ecosystems, continues with descriptions of the most significant environmental problems that are caused by energy consumption and delineates adopted and proposed suggestions on the mitigation of environmental threats.

It is often taught in layman’s terms that “energy may be neither created nor destroyed” and this brings into question the meaning of “energy conservation.” Basic principles, such as energy conservation, stem from more general laws of Physics. The principles that govern the exchange and transformations of energy are succinctly examined in this chapter. The governing equations of energy conversion processes, or Laws of Thermodynamics, their corollaries and some of their applications to energy conversion processes are presented. A historical perspective is first given on the origins of modern energy conversion principles. The characteristics, significant variables/properties and types of Thermodynamic Systems are briefly explained. The two fundamental Laws of Thermodynamics (first and second) are postulated and the implications on the energy conversion processes are given succinctly. The operation of the simple gas and vapor power cycles is elucidated as well as several processes that are commonly used for the improvement of these cycles. Finally, the concept of exergy is introduced quantitatively and in detail. Based on exergy, several ways are presented on how this concept may be used to improve thermodynamic processes and cycles.

The building of more nuclear power plants is one of the proposed solutions to the increasing production of anthropogenic CO₂ and the mitigation of the global warming threat. Had the USA constructed an additional 56 nuclear power plants in the 1990s, the country would have been in compliance with the Kyoto protocol. Nuclear power plants are typically very large (1,000 MW) and very complex power producing units. The nuclear reactor itself contains large amounts of radioactive materials, which if released in the environment, may cause large-scale environmental accidents. For this reason, a nuclear reactor must have multiple levels of safety systems and its controls must be designed to shut down the reactor within a very short time. All nuclear reactors have six basic components, which are described in detail in this chapter. Several types of nuclear reactors and nuclear power plants have been developed by different countries. The special design characteristics and the operation of these plants are summarized. Because accidents in nuclear power plants are feared the most by the public, the three accidents that received the highest notoriety, at the Three-Mile Island in the U.S.A., at Chernobyl in the former Soviet Union and at the Fukushima Dai-ichi power plant in Japan are described in detail. The causes of the accidents are examined and early actions that could have been taken by the operators are presented. Finally, it is apparent that, if the world is to rely on nuclear energy in the long-term, the more abundant uranium-238 and other fertile nuclear materials must be utilized. This makes necessary the use of breeder reactors, which may become the next generation of nuclear reactors.

Fusion is the energy that powers the stars, including our own Sun. Deep in the mass of the stars common hydrogen is converted first to deuterium. Two nuclei of deuterium combine to form helium, while releasing a large amount of energy. Since the fusion reactions were first discovered, it was realized by the scientific community that the controlled harnessing of fusion may provide enough energy to the human society for millions of years. Fusion energy may solve the “energy problem” for humanity. Fusion energy is a panacea whose realization may not be too far in the future. Multinational research and development efforts have produced plasma confining methods, which may lead to continuous and controlled fusion during the twenty-first century. While several technological breakthroughs are still needed, enough progress has been made to elucidate the basic mechanisms of the fusion reactions and to point fusion research to the right direction. Because of fusion and its great promise, the time when the energy of the stars will be harnessed on Earth and when the produced power will be abundant and inexpensive may not be too far in the future.

At an average rotational radius around the Sun of 1.49*10¹¹ m and with an average radius of 6,378 km, the planet Earth receives solar radiation power of approximately 1.73*10¹⁴ kW, a quantity that surpasses by far all the power requirements of the Earth’s inhabitants. This continuously received power, which is called incident solar radiation and shortened to insolation , integrates to a total energy of 5.46*10²¹ MJ per year, or more than 100 million times the total energy used by earthlings in a year. This tremendous amount of energy is abundant, free of charge, almost uniformly distributed and available to all nations and inhabitants of the planet. However, only a very small fraction of the incident solar radiation is used by the Earth’s population. Passive solar heating systems provide with space heating and hot water a low fraction of the buildings, primarily in OECD countries, while thermal solar power plants and photovoltaic cells provide a small fraction of the electricity consumed. Despite its low utilization at present, and because of the enormous amounts of power reaching the Earth, solar energy is a prime alternative energy source and has the potential to supply a very high fraction, if not all, of the power used by the Earth’s population. This chapter starts with a short exposition on the amount of solar energy available and continues with the exposition of the two main families of systems that are currently used for power production from solar energy: solar thermal systems and photovoltaic systems. Photovoltaic solar cells and solar thermal systems utilize the solar energy in entirely different ways and are examined separately. Emphasis is given on the electric power production by solar energy as well as the current and proposed systems used for electric power production. A brief mention of the passive heating systems and the environmental effects of solar energy utilization are also included in the chapter.

Since the time of the ancient sailboats and windmills, the power of the wind has been harnessed for ship propulsion and the performance of mechanical work. In the modern era, wind has been increasingly used for the production of electric power. In the first decade of the twenty-first century alone, the production of electricity from wind power worldwide has increased by a factor of eight. Similar to solar energy, wind is also a distributed, renewable source of energy. The energy density of the wind is low, but wind is available in all the geographical regions of the world and its geographical distribution is more uniform than that of solar energy. Wind turbines of different sizes and designs are currently used successfully for the production of electric power. The bigger and more efficient types of these engines have blades with lengths between 20 and 50 m, are located at the top of 50–140 m towers and are becoming ubiquitous in the landscape of several OECD countries. Wind is probably the most environmentally benign energy source. In theory, it has the capacity to satisfy the energy needs of entire countries and even that of the whole planet. However, it is also an intermittent source with availability and intensity much less predictable than any other source of alternative energy. This intermittency is a significant drawback and will limit the more widespread use of wind power, unless suitable energy storage systems are developed that would store part of the energy produced during windy periods.

Geothermal energy is the primordial energy of the Earth, produced in the interior of the Earth by nuclear reactions. It is a thermal form of energy that is conveyed by the magma to the crust of the planet. In the crust, some of the Earth’s heat is advected by the water of deep aquifers to the surface. While, high-quality, high-temperature geothermal resources are met in regions that are close to the tectonic boundaries, other lower temperature resources are abundant in all geographic locations. Geothermal energy is primarily utilized by extracting dry steam or high-temperature liquid water from an aquifer and by using the steam or the vapor of another substance for the production of power with a turbine. Depending on the type and the characteristics of the geothermal resource, flashing or binary power plants are used for the production of steam and electricity. The geothermal electric power plants are simpler than fossil or nuclear power plants, i.e. they have a lesser number of components. Because the geothermal fluid emanates from the Earth’s interior and carries other substances, including solids and non-condensable gases, the design of the equipment of a geothermal power plant poses several challenges, such as the avoidance of scale in the well and flashing chambers; and the removal of non-condensable gases from the condenser.

Wood, agricultural crops, agricultural residues, herbaceous grasses, algae, sea plants, municipal solid waste, sewage, and animal waste are all forms of biomass that are being used in order to satisfy the energy demand of modern society. Biomass is still the principal fuel used for cooking and domestic heating in most agrarian societies and many developing nations, while in the industrialized nations it is primarily used for the production of other fuels, the biofuels, or it is burned for the production of electricity. The production of agricultural crops necessitates large areas of arable land and significant amounts of fresh water for irrigation, two scarce resources on Earth. The consumption of these crops to satisfy the energy demand of the population is fast becoming a controversial socioeconomic issue because of the direct competition of energy production with food production and food availability to the poorer segments of the society and poorer nations on the planet. This “to eat or to burn” dilemma in conjunction with the increasing population of Earth, is expected to introduce limitations on the use of agricultural crops and to increase the use of waste products for energy production. This chapter describes the types of biomass that are available as well as their energy content. It presents several useful calculations and facts on the conversion of biomass to transportation fuels and computes, as a special case, the energy balance related to the conversion of corn to ethanol. It appears that in the conversion of corn to ethanol, more energy goes into the materials and processes needed than the energy content of the produced ethanol. The chapter also investigates the environmental effects, social, economic and regulatory issues that will play an important role to the increased utilization of the various types of biomass as energy sources.

More than two-thirds of the planet’s surface is covered by water, and power may be obtained from both the surface water and the deep oceans. Hydroelectric, tidal, ocean current, wave, and OTEC power installations are among those that may convert the power of the water directly to electricity. Unlike wind power, these renewable energy sources are either continuous or predictably variable. The naturally occurring water cycle and the resulting rainfall transfer millions of tons of water annually to high elevations with significant potential energy. River flows on the planet carry the very high amounts of potential and kinetic energy, which currently turn the turbines of several hydroelectric power plants and have the capability to provide at least 25% of the total electric energy demand of the planet. The 240 MW tidal power plant in La Rance, France, has proven that there are reliable systems in operation to convert the tidal energy of the sea to electric power. Tidal power plants in prime locations in England, Norway, USA, Canada and other parts of the world have the capability to produce between 25 and 100% of the electricity demand in several coastal countries. The harnessing of the energy in ocean currents, such as the Gulf Stream, is at present a rather futuristic idea, which has the potential to cover the entire global demand for electricity. Several wave power systems and devices have been invented in the last half of the twentieth century, which are now in the testing and pilot-plant phases. If successful, harnessing the waves and the widespread use of wave power have the potential to produce more than 50% of the electric demand in island and coastal countries, such as Portugal, Norway, Great Britain, Japan, South Africa. and Australia. The Ocean Thermal Energy Conversion (OTEC) cycle also has the potential to supply almost unlimited electric power to coastal communities, but needs significantly more research and development efforts to reliably and economically meet this promise. All these electric power sources associated with the flow of water are examined in this chapter in a scientific manner. Engineering systems and cycles for the utilization of these resources are described. The environmental and ecological impacts of these systems are also examined critically.

In the beginning of the twenty-first Century, our society mostly uses energy that has been accumulated for millennia: Fossil fuels have stored in their chemical compounds vast amounts of energy, which we now use for our primary energy needs, unfortunately, at a very high rate that cannot be sustained. When fossil-fuels are exhausted or when their use is curtailed because of environmental factors, such as the production of greenhouse gases, humans will have to rely more on alternative energy sources among which are nuclear, wind, and solar power. While the production of power by nuclear energy may be controlled, wind and solar power are intermittent or periodic sources, which may produce power when there is limited demand and may not produce power at all, when demand is high. For example, during the night hours of July 17th, when there is high demand for air-conditioning and electricity in the northern hemisphere, there is no Sun and the average wind power is significantly lower than average. If the society relies on alternative energy sources and stored energy is not available during this night, humans will experience a significant shortage of energy with the inconvenience this entails. As the human society moves more to the direction of alternative energy sources, the need for energy storage becomes apparent and more acute in order to satisfy the fluctuating energy demands. This chapter provides an exposition to the several energy storage methods that are currently used to smoothen the electric power demand and those that may become feasible and popular in the future. First, the electric energy demand patterns in a contemporary society that makes significant use of air-conditioning in the summer are explained. Secondly the various methods for energy storage, such as electromechanical, thermal—in both latent and sensible heat form—and chemical are explained with the devices/systems that make energy storage possible. The alternative method of storing “coolness” with materials that exhibit a temperature hysteresis in their melting/solidification processes is elucidated within the context of thermal storage methods. Finally, details are given on the possible switch to hydrogen as a clean energy storage medium, the long advocated “hydrogen economy” and the inherent advantages of Fuel Cells as devices for the direct conversion of chemical energy to electricity.

In a strict sense, the term “energy conservation” is a misnomer. As demonstrated in Chap.​ 3 with the First Law of Thermodynamics, energy is conserved by nature. “Energy conservation” does not require any action by engineers or by the general population. What is usually meant by this colloquial term is the eventual conservation of natural primary energy resources, when we perform tasks that are necessary for the functioning of the human society. The colloquial “energy conservation” may be more scientifically expressed as exergy conservation , minimum exergy destruction or minimum entropy production while the societal tasks are being performed. The use of the exergy concept and exergetic calculations ultimately lead to the minimum consumption of primary energy resources and, finally, to the conservation of natural resources. While most of the other chapters in this book pertain to the supply side of the energy equation, conservation and improved efficiency are directly related to the demand side. By “conserving energy” and forgoing the use of a fraction of primary energy sources for the performance of societal tasks, the human society demands less primary sources that supply the global energy demand. As a result, less primary energy is demanded and consumed and the natural resources that supply this energy are conserved. In this chapter we distinguish between conservation and higher efficiency, we apply the concept of exergy in order to perform tasks with the minimum possible exergy destruction and we present several examples of methods that lead to the lesser consumption of natural resources in the areas of transportation and comfort in buildings. These methods include the use of fluorescent or LED devices for lighting, geothermal heat pumps for heating and air-conditioning, evaporative cooling, and electric cars.

When one asks the question, “why there are no more wind or solar photovoltaic power generation units in the world?” the simple answer is: “because fossil fuels and nuclear energy were cheaper sources to produce electricity in the near past.” When a new coal power plant produces a kWh at 3.5 cents and an old nuclear power plant for less than 1 cent per kWh, it is difficult for an electricity producing corporation to justify purchasing a wind turbine that would produce electricity at 12 cents per kWh or a solar farm that would produce at 16 cents per kWh. When the price of electricity produced from renewable sources of energy becomes less than the price produced from conventional energy sources, the economic considerations will favor the development of more geothermal units, solar plants, wind generators, etc. A combination of rising fossil fuel prices, the probable initiation of carbon credits, and a favorable regulatory environment that provides tax credits and accelerated depreciation may change these economic and financial circumstances for alternative energy. This chapter provides a succinct exposition of the entire decision making process that leads to the construction and operation of a power plant, from the realization of the need for more electric power, to the enumeration of the alternatives, to the choice of the optimum alternative solution that maximizes profitability for a corporation or, equivalently, provides the needed amount of electric energy at minimum cost. Central to the financial considerations are the concept of the time-value of funds and the Net Present Value method for the appraisal of an investment. Because this book is aimed for the engineering student with little or no knowledge of economics and finance, the level of this chapter is rather elementary. There are no highly sophisticated economic concepts and methods to be presented, while simple and comprehensive definitions of all the concepts used are offered in the text.