Energy use is increasing along with the growth in population and the changes in our energy consumption habits. This brings up the question: How can we better prepare for a future so that we use less energy? This question can be answered with two phrases: energy conservation or energy efficiency. The two terms may seem similar; however, there is a basic difference between the two, which results from quality engineering. Energy conservation is an action of using less energy, either through personal choice, or because of necessity. Energy efficiency, on the other hand, is the engineering outcome of technologies that consume less energy to conduct the same function without giving up the standards. Turning off the lights in the evening, when there is a need for light, is energy conservation.

Energy engineering has a multidisciplinary nature including disciplines such as mechanical, electrical, chemical, civil, and environmental engineering that study the theory and applications of energy systems. The theoretical aspects of such applications stretch over these disciplines. In this chapter, the theoretical basics of five major fields are covered to help engineers and professionals have an understanding of how each discipline and field is associated with energy. The fields covered are electrodynamics, chemical energy conversion, thermodynamics, fluid mechanics, and heat transfer. It is important to keep in mind that each individual field is a wide ocean, and there are many textbooks written on each field. This chapter is intended to give the reader some brief information on each field accompanied by pertinent equations.

Nuclear energy is one of the key players in the energy world due to its immense potential to deliver energy and it being free of greenhouse gas emissions. It is not an intermittent energy source. While the construction cost is high, operating costs are lower than its rivals such as coal and natural gas. It does, however, come with the obvious question of whether or not it is safe, especially after several notable accidents of the past 40 years, which we will examine in this chapter. The other concern about nuclear energy is nuclear waste, which is harmful to the environment and takes a long time to degrade. Following the last significant nuclear trauma, the Fukushima accident, there has been increasing motivation, research, and investment in nuclear energy. Improvement of the technology requires progress in various fields including exploration of new fuel resources, development of advanced reactor designs, more economic, safe, and sustainable waste management methods, and enhancement in the use of nuclear fusion for energy generation.

Biomass is organic material that comes from plants and animals. It can be defined as organisms that are living or have recently died, and the byproducts of these organisms. It is a renewable source, and it is known to be the oldest source of energy for human beings, after the Sun. Biomass also gets its energy from the Sun. For instance, during photosynthesis, sunlight gives plants the energy they need to convert water and carbon dioxide into oxygen and sugars. These sugars are carbohydrates, and they supply the plants with energy. They are a good source of energy for animals and humans as well. Photosynthesis is the process by which plants and some other organisms convert sunlight into chemical energy. The chemical energy is stored in carbohydrate molecules, such as sugars.

Renewable energy is the energy that can be harvested from natural resources that are not exhaustible as they are naturally replenishing, such as sunlight or wind. These resources are inexhaustible over time; however, the amount of energy they can provide within a unit amount of time is limited and differs depending on the type of renewable energy resource. Renewable energy is an environmentally friendly alternative to the conventional energy that relies on fossil fuels. It is a key instrument in mitigating climate change due to its little or no greenhouse gas emissions.

Future prospects attributed to energy topics are covered in three sections in this chapter. First, energy consumption projections are reviewed to have some idea about what can be expected on the energy demand side. Then, prospects that can address the energy supply and demand concerns for the coming decades are examined from two perspectives. One of these points of view is centered around technology-based prospects that focus mainly on energy generation and storage solutions. The second perspective is sector-based prospects where possible future solutions on energy efficiency and reduced energy demand for the building, transportation, and industry sectors are communicated.

Global population was 1 billion in 1800, doubled in the next 127 years to 2 billion, then doubled to 4 billion in the following 47 years. Besides the significant increase in human population, changes in living standards, evolving consumption habits, urbanization, and growth in industrialization have made it obvious that there is a need for understanding sustainability, identifying areas on which to reflect, and defining indicators for measuring and evaluating it.

Achieving sustainable development goals (SDGs) that are associated with energy relies on improvements in energy efficiency, clean power generation through conventional means, and renewable energy technologies. Yet, in achieving these goals there is another significant player in the game. The increasing contribution of renewables in total energy production and a global trend towards smart grids comes at the cost of the necessity to be able to store energy in a cost-effective manner with minimal losses possible. The need for such energy storage systems is greater than ever with the increase in energy consumption, and energy generation using both non-renewable and renewable sources. The increase in the capacity of electricity that renewable energy systems supply into the grid comes with the risk of increased uncertainty in managing the grid due to the intermittent and incalculable nature of these renewable sources.

The oceans possess a vast amount of energy in different ways. All these forms are studied under the generic term of ocean energy, which can also be referred to as marine energy or marine and hydrokinetic energy. Energy from the ocean can be harnessed through kinetic, potential, thermal, and osmotic energies with each form of energy encompassing a variety of technologies. Energy in kinetic and potential forms can come from tides or waves. Tidal energy can be categorized within itself into tidal barrages and tidal streams. Barrages work on the idea of converting potential energy to electricity, while streams allow making use of kinetic energy. Wave energy technologies also can operate based on converting kinetic or potential energy into mechanical and then electrical energy. The thermal energy potential that the oceans have is another significant resource. Solar radiation on the oceans causes the upper segments of the water to heat up, while the deeper segments where sunlight penetration gradually reaches minimal values are much cooler.

Wind energy is one of the most promising and mature renewable energy technologies. Similar to hydropower, wind energy also is a result of solar energy which causes the formation of air currents in the atmosphere. Wind is caused by non-uniform heating of the Earth’s surface due to different bodies making up the surface. An example of this is coastal winds. As the Sun rises, it heats the land faster than it heats the sea. Air above the land becomes less dense by heating up and rises. This results in a pressure gradient, pulling the air from over the sea towards the land. This is the sea breeze. After sunset, the land cools off faster than the water. Hence, the air over land becomes denser and tends to lower while the air over the sea rises.