Energy Resources and Consumption


Energy is a key component of modern human society.  It is used to power our daily lives and the world’s growing population demands considerable increases as non-western economies grow.  We’ll look fundamental aspects of energy and today’s primary sources, as well as the role of alternative fuels.


What are the basic forms of energy?


Energy is the ability to do work or the potential to cause change, and the amount of work (w) is equivalent to the force (f) exerted on an object, times the distance (d) that the object moves.

Work: W = F . d.

There are two main categories of energy, potential and kinetic energy, and within these two categories there are several types of energy. Potential energy is the stored energy associated with a position in a gravitational field. For example, when you are standing on your snowboard at the top of a mountain, you have a large amount of gravitational potential energy. The gravitational potential energy (Ep) of a body is equal to the mass (m) of the object, multiplied by gravity (g), times the elevation (h) of the object:

Potential Energy: Ep= m .  g  . h.

When you push off the top of the mountain to snowboard down to the valley you are applying a force against gravity to move your body; you are doing work. As you move down the mountain you are converting your potential energy to kinetic energy, which is the energy of motion. The amount of kinetic energy (Ek) in a system is measured by ˝ the objects mass (m) times the velocity (v) squared. The amount of work (W) done by kinetic energy is dependent on the change in kinetic energy (rEk) plus the change in velocity (rv) of the object.

Kinetic energy: Ek = ˝ m . v2

Work: W = rEk + rv

As your snowboard glides over the snow, you are creating friction and converting kinetic energy to internal (heat) energy, which is energy that is associated with the speed of atoms and molecules (Figure 7.1).  While going down the slope you may also feel the sun burning your face. This heat is caused by radiant energy or the energy of photons carried by electromagnetic radiation.  When you arrive at the bottom of the hill after a long ride, you may be hungry from expending so much energy, so you go to the lodge to eat a burger, otherwise known as chemical energy, so your body can do more work.  Chemical energy is energy contained within molecular bonds holding the elements of chemical substances together.


The main source of energy that we use is the Sun. Solar energy (or radiant energy) warms the planet and allows photosynthetic plants to grow; it makes up 99% of the energy budget of our planet. The food we eat stores chemical energy that primary producers or plants have captured from the sun through metabolic pathways. This chemical energy is either consumed directly, or indirectly from secondary consumption of an animal, then subsequently used to power the cellular functions in our bodies. To move your body, as in pushing off from the top of the mountain in the snowboard example, you must convert chemical energy to kinetic energy.


The firewood warming the ski lodge at the bottom of the slope is another source of chemical energy that can be readily converted to heat energy for warmth or for cooking. Fossil fuels, such as oil and coal, are other examples of chemical energy that are extracted from the Earth to power our lives.  For example, it is converted to electrical energy that is transported into our homes to power appliances or into the battery of the music player you were listening to as you snowboarded down the mountain slope.


Figure 7.1

Internal heat generated from atomic speed increases with greater friction, so that greater speed means higher heat‑james/a111/lectures/figs/04-03.jpg



What are the laws that govern energy?


When eaming the law that govern energy, we enter the field of thermodynamics, which describes energy as it changes from one form to another. The first law of thermodynamics (also known as the law of conservation of energy) states that energy can be neither created or destroyed, but can be changed from one form to another. Another way to put this is the total input of energy into a system must equal the total output of energy from the system. In the snowboard example, as we went down the mountain, energy was transformed from gravitational potential energy to the kinetic energy of motion. In this process energy was not created or destroyed, it was just transformed from one type of energy to another (Figure 7.2).


Figure 7.2

Energy transformations.


However in practice, the energy available for work in a system is not perfectly conserved as energy changes from potential to kinetic energy. The second law of thermodynamics states that perfectly efficient energy transformations are not possible. This means that there are unavoidable losses in useable energy when we transform it from one type to another. For example as our snowboarder was moving down the mountain, the transfer of gravitational potential to kinetic energy was not perfectly efficient, meaning that 100% of the potential energy was not transformed to 100% of the kinetic energy. We lost useable energy for work in the form of heat energy from the friction of the snowboard on the hill, as well as from our bodies moving through the air, itself creating heat from the friction of the collision with molecules in the air.


Energy tends to change from a higher quality, that is a more usable type of energy, to a lower quality, that is a less usable type of energy.  This property is described by the entropy, which dictates that systems tend to drift from a high energy to a lower energy state (i.e., a more disorganized form). For example, energy moves from kinetic energy to heat or thermal energy, which easily dissipates and is thus more difficult to harness and used for work. It is not possible to recapture the heat energy that we lost as we moved down the mountain; therefore, potential energy was useable energy in our example that was then lost from the system. In another example, when burning gasoline in our cars we are converting chemical energy from the gasoline to the energy of motion or kinetic energy. In the process, we are losing large amounts of thermal energy through friction of the engine parts rubbing together, as well as from the resistance of the tires on the road and the resistance of the car moving through the wind.  Because we cannot transfer 100% of the available energy to useable energy, these processes have energy transfer rates that are not 100% efficient.


Energy efficiency refers to the ratio between energy output (services such as light, heat and mobility) and input (primary energy like gasoline or food). In general, the greater the number of energy transformations, the larger the fraction of energy wasted in the form of avoidable and unavoidable energy losses. Approximately 50% of all of useable energy from primary inputs are lost today from inefficient energy transformations. These losses can be decreased or avoided with the right technology.  For example, some avoidable useable energy losses include poorly designed appliances, low efficiency incandescent lights and poorly insulated homes, which allow useable energy to escape the system, often as heat energy (Figure 7.3).  Simple strategies to save energy include converting incandescent lights to fluorescent lights for an efficiency gain from 5% to 22%. Similarly, designing more efficient combustion engines for cars will have profound impacts on energy demands. A powerful way for achieving sustainable development in the near future depends on our ability to improve energy efficiency. This would both reduce the amount of energy that we consume, and it would decrease the greenhouse gas emissions and pollution waste into the atmosphere from burning fossil fuels.


Figure 7.3

Heat energy lost around the house that can be reduced by more efficient insulation.




What are the major sources of today’s energy?


Energy used for human applications can be broken down into two broad categories: non-renewable energy sources (fossil fuels and nuclear) and renewable energy sources (biomass, hydrologic, solar, wind, and geothermal). Fossil fuels preserve solar energy that was stored in organic compounds millions of years ago. Coal, oil and natural gas are today the dominant forms of fossil fuels used around the world accounting for 80% of all energy used globally (Figure 7.4). Coal accounts for ~24% of the energy used around the world, which is harvested from rock layers that originate from ancient swamps. Oil (~34%) and natural gas (~21%) account for more than half of all energy used around the world, and is trapped in rocks that form natural containment vessels.  Because fossil fuels were formed tens to hundred of millions of years ago, they and cannot be replenished, so these energy resources are finite.


Nuclear fuel accounts for ~7% of global energy use and is also considered a non-renewable form of energy because the uranium needed to create nuclear fuel is a finite, mined resource. Nuclear fuel goes through many steps before it can be used in a nuclear power plant to generate electricity, but is involves more efficient energy transformations than other fossil fuels.  Whereas no significant greenhouse gases are emitted, radioactive waste products greatly complicate the use of nuclear power plants as a energy source.


Figure 7.4

Primary energy supply by fuel type


In 2003, renewable energy resources accounted for ~13% of the total global energy supply. Of that, combustible renewables or biomass burning accounted for the greatest proportion of energy. Combustible renewables are distinct from fossil fuels because they are a renewable resource. Combustible renewables and renewable waste are organic material and waste from plants, trees and crops that are traditionally used as firewood for cooking and heating in many developing countries. However, modern uses include combustion to produce energy in the form of electricity, steam and biofuels.  Hydroelectric energy accounts for the second largest proportion of renewable energy with ~2% of global energy use. Hydroelectric power plants use the kinetic energy of falling water to generate electricity. A turbine and a generator convert this energy into mechanical and then electrical energy.


Modern renewable forms of energy account for less than 1% of global energy used today. However, their use is on the increase as the impact of fossil fuels burning is become clearer and this resource is becoming scarcer or politically more difficult to secure.  Modern renewables are generated from solar, wind, water and geothermal energy, and are produced on local scales; therefore, their use would result in renewable energy development, changes in infrastructure, and job creation in many regions of the world.


Solar panels use photovoltaic cells that convert light energy into electricity at the atomic level. Photovoltaic systems can be constructed to any size based on individual energy requirements, and are low-maintenance. They are ideal for supplying power to homes far from utility power lines in remote areas, especially when their efficiency is further improved. Electricity generating wind turbines are used to harness the kinetic energy from wind created by the uneven heating of Earth lower atmosphere (or troposphere).  Renewable energy can also be generated from wave and tidal movement at coastal areas or it can be captured from Earth's internal heat. Typically, geothermal energy is used where access to hot rocks and water is available.



What are some of the costs and benefits associated with today’s sources of energy?


Fossil fuel burning accounts for more than 70% of all electricity generated in the United States and almost 90% globally.  One of the advantages of fossil fuels is that presently there are large quantities of fossil fuels available for extraction and they can be easily transported from areas where they are extracted. For example, pipelines are used to transport oil to other parts of the world and to ports for shipping and refinement. Coal, oil and gas are safely moved in trucks, trains and ocean going freighters; although, sometimes environmental costly accidents occur, such as the Exxon Valdez oil spill in Alaska in 1989 or the Galicia oil spill in Spain in 2002. Fossil fuels are also convenient because we have build a supporting infrastructure for their use. This transportability and infrastructure have facilitated the creation of a powerful global market for fossil fuels. However, the uneven occurrence of coal, oil and natural gas around the globe also accounts for much of today’s civil unrest and wars.


The combustion of coal, oil, and natural gas to generate electricity and power our vehicles contributes to global warming through increasing the concentration of carbon dioxide (CO2) in the atmosphere (Figure 7.5). Furthermore, the secondary emissions associated with fossil fuel burning, such as sulfur oxides (SOx), nitrogen oxides (NOx), hydrocarbons, soot, dust, smoke and other suspended particulate matter cause persistent health problems like cancer and asthma. Atmospheric emissions from power plants alone are responsible for roughly two-thirds of SOx emissions, one-third of NOx emissions, and one-third of all CO2 emissions in the United States.  In addition to atmospheric emission, waste from fossil fuel burning, the extraction processes such as strip mining and ocean floor drilling, also degrade land and water resources. The finite nature of fossil fuel resources as well as their negative health and environmental costs and the extraction process are leading to the development of alternative forms of energy.


Figure 7.5

Global fossil carbon emissions over time



In some ways, nuclear fuel is cleaner than fossil fuels, because nuclear power plants emit no significant greenhouse gases or generate particulate air pollution. However, the radioactive nature of nuclear fuel creates risks of nuclear accidents, like the 1986 disaster at Chernobyl in the former USSR (now Ukraine).  Nuclear accidents can have disastrous consequences for the population and the environment through radiation poisoning and contamination of land and water resources.  There is also no simple way to dispose of the spent nuclear waste that is left after the nuclear fuel has been used in the reactors. Finally, nuclear fuel can be used to create nuclear weapons, which are a major concern for escalating regional conflicts.


Presently, renewable energy resources only account for ~13% of total energy needs.  Biomass burning, mostly in developing countries, and hydroelectric power are currently the most widely used sources of renewable energy. However, biomass burning is a major cause of deforestation and threatens biodiversity around the world. In addition, hydroelectric dams can be damaging to local people, riparian ecosystems, native species and migrating coldwater fish populations. Hydroelectric dams also release methane from decaying organic matter trapped within dam reservoirs, contributing to global warming.  The huge Three Gorges Dam project in China is one of the most controversial dam projects in the world, with large scale environmental costs for short-term economic benefit. Less ecologically invasive renewables such as wind, solar, geothermal and wave energy may be able to mostly avoid undesirable atmospheric emissions, waste and negative impacts on land and water resources.



What drives our need for energy?


Energy is a key requirement for economic and social development. Throughout human history, development has been tied to energy resources, whether that was through human or animal muscle energy for work, or from more modern types of energy such as machines that use fossil fuel or electric energy to do work. The industrial revolution radically altered the relationship between humans and energy, allowing for the rapid expansion of the human population and economic development in many regions of the world. However, about three quarters of the people on earth currently still do not have access to the benefits from advanced energy resources and still rely on human or animal muscle power to do the majority of their work.


Figure 7.6

Population growth and energy use over time


Adapted from:


Access to energy is directly related to the quality of human life, social welfare and social development.  A society’s quality of life or standard of living can be measured by the amount of total per capita energy used (Figure 7.6). Societies with high levels of energy infrastructure and availability are better able to meet the basic needs of their population. The availability of energy also contributes to social development by improving access to education and public health. Agricultural productivity and food security is coupled with energy availability, with reliable energy sources substantially improving the livelihoods of people living in rural communities.


Energy is the driver of economic growth and economic development, as its availability supports the expansion of businesses, schools and other aspects of the social infrastructure. In addition, energy supports the transportation of goods, supplies and working people, which are necessary for businesses and economies to flourish. Energy and petroleum products are also key ingredient for the development of products, such as medicines and electronics.


Economic activity and energy use is expected to expand rapidly in the next twenty years, especially in emerging economies such as China and India (Figure 7.7). Mature economies, such as the United States and Western Europe, will continue to increase economic activity and energy needs on the current path, while transitional economies of Eastern Europe and the former Soviet Union are expected to reestablish mid-range economic activity and energy use increases in the coming years.


Figure 7.7

World marketed energy use by region 1970-2025


Recognizing the key role of energy in today’s human society is well illustrated by the strong positive relationship between wealth [measured in gross national product,  GNP, or gross domestic product, GDP) and energy use (Figure 7.8). In the wealthier nations, energy availability stimulates economic development, which in turn creates more energy infrastructure, services and economic growth. Many people in impoverished nations have little access to energy resources or infrastructure, which limits social and economic development. 


Energy availability is also critically tied to the environment and sustainable development. Our use on fossil fuels is fundamentally changing the composition of the Earth’s atmosphere, which has major environmental and social consequences. Sustainable development of energy depends on society to provide reliable sources of clean energy to the growing number of people in emerging economies, as well as altering the energy infrastructure to cleaner and perhaps distributed technologies.


Figure 7.8

Energy consumption versus GNP




What does the future hold for our global energy needs?


Global demand for energy is expected to increase by more than 50% by the year 2030, based on economic predictions. Although western nations are still the dominant users of energy, other parts of the world are on a track to surpass North America as the largest user, as Western Europe and North America are stabilizing their usage of energy (albeit at a high level). Stabilization has been achieved mostly through conservation and efficiency approaches. In contrast, energy use in developing nations is driven by two factors: population growth and economic growth. Two-thirds of this increase in energy demand is expected to be from countries with rapidly growing economies such as China and India. While many nations have adopted family planning methods to control their population growth, all developing nations are striving to reach greater social and economic development and this drives their growing demand for energy.  To stabilize the global use of energy, therefore, we will need to seek a new model of economic development that allows for growth without the associated surge in energy demand.


On our current path, by the year 2030, fossil fuels are expected to meet 85% of the new demand for energy, with oil supplying much of that need due to its importance in the transportation and industrial sectors. Sixty two percent of electricity generation needs are expected to occur from coal and natural gas, with consumption of natural gas expected to increase two-fold by 2030. (Figure 7.9).


Figure 7.9

World marketed energy use by energy type 1970-2025



Although fossil fuels are expected to supply the majority of global energy needs in 2030, total renewable energy use is also expected to increase significantly to meet the greater and longer-term demand for power (Figure 7.10). It is predicted that this increase may just keep pace with demand, rather than exceed it.  Overall, renewable energy resources are expected to account for 20% of world electricity generation in 2030, which is only a 2% increase from today. Ninety percent of the electricity generated from renewable energy resources today comes from hydroelectric power plants with combustible renewables accounting for 6% of electricity generation, and other modern renewables such as wind, solar, and geothermal, accounting for the rest.


Figure 7.10

Renewable supply by energy source 2003-2030


In developing countries, heating and cooking currently account for the majority of renewable energy consumption, with traditional biomass burning contributing the largest portion, and this trend is expected to continue into the near future. Of the renewable resources, hydroelectricity is still expected to supply the greatest amount of electricity, with wind power the second-largest renewable energy source. Biomass and geothermal energy used for electricity generation are both expected to increase three-fold by 2030, while solar, wave and tidal energy are projected to increase substantially after 2025.


The current level of renewable energy development represents only a small proportion of what can be developed with technological investment. The cost of many of these technologies has already decline significantly, and it is estimated that use of renewable energy sources could meet 50-80% of the US energy needs in the next 25 years. For example, the potential of wind, solar and geothermal energy in the US is equivalent to more than 15,000 times the amount of energy that the nation currently uses. Given that carbon emissions are projected to increase by 60% in the next 25 years from continued use of fossil fuels, leading to global climate change, the expansion into safe, cleaner and more efficient technologies to meet our global energy needs will directly benefit our environment and the global community, while allowing continued economic growth.