Power electronics is the implementation of solid-state electronics to the control and conversion of electric power. It also refers to a subject of research in electrical and electronic engineering which deals with the design, control, computation and unification of nonlinear, time-varying energy-processing electronic systems with fast dynamics. The first high power electronic devices were mercury-arc valves. The potentialities and economy of power electronics system are determined by the active devices that are available. Formerly, the mercury arc valve, the high-vacuum and gas-filled diode thermionic rectifiers were widely used in power electronics. As the ratings of solid-state devices enhance in both current-handling capacity and voltage, vacuum devices have been nearly entirely replaced by solid-state devices. 

An electric power system is a network of electrical constituent used to supply, transmit and use electric power. An example of electric power system is the network that gives a region's homes and industry with power—for sizable regions, this power system is known as the grid and can be widely divided into the generators that supply the power, the transmission system that carries the power from a generating centres to the load centres and the distribution system that feeds the power to nearby industries and homes. Smaller power systems are also found in industry, hospitals, commercial homes and buildings. Direct current power can be supplied by batteries, fuel cells or photovoltaic cells. Alternating current power is typically contribute by a rotor that spins in a magnetic field in a device known as a turbo generator. The speed at which the rotor spins in mixture with the number of generator poles determines the frequency of the alternating current produced by the generator.

Power Engineering deals with the the generation, transmission, distribution and utilization of electricity as well as the design of a range of related devices. These include transformers, electric generators, electric motors and power electronics. Technologies involve to generate the power are called power generation technologies. Generation of electrical power is a process whereby energy is transformed into an electrical form. There are several different transformation processes, among which are chemical, photo-voltaic, and electromechanical. Electromechanical energy conversion is used in converting energy from coal, petroleum, natural gas, uranium, or water flow into electrical energy. Of these, all except the wind energy conversion process take advantage of the synchronous AC generator coupled to a steam, gas or hydro turbine such that the turbine converts steam, gas, or water flow into rotational energy and the synchronous generator then converts the rotational energy of the turbine into electrical energy. It is the turbine-generator conversion process that is by far most economical and consequently most common in the industry today.

Electric power transmission is merely the bulk transfer of electrical energy, from generating power plants to electrical substations located near demand centres. This is well defined from the local wiring between high-voltage substations and customers, which is typically mention to as electric power distribution. Transmission lines, when interconnected with each other, become transmission networks. The consolidate transmission and distribution network is known as the "power grid" in North America. Within UK, "power grid" is also known as the "National Grid”. A wide area synchronous grid, called an "interconnection" in North America, sprightly connects a large number of generators distributing AC power with the same corresponding frequency, to a large number of consumers.

A smart grid is a system which includes a diversity of operational and energy measures including renewable energy resources, smart meters, smart appliances and energy efficiency resources. Electronic power conditioning and control of the production and distribution of electricity are salient appearance of the smart grid.

There are many types of renewable energy. Most of these renewable energies depend in one way or another on sunlight. Hydroelectric and wind power are the direct result of differential heating of the Earth's surface which leads to air moving about (wind) and precipitation making as the air is lifted. Solar energy is the direct conversion of sunlight using panels or collectors. Biomass energy is saved sunlight contained in plants. Other renewable energies that do not based on sunlight are geothermal energy, which is an outcome of radioactive decay in the crust combined with the original heat of approving the Earth, and tidal energy, which is a conversion of gravitational energy.

Since the discovery of electricity, we have sought effective methods to store that energy for use on demand. Over the last century, the energy storage industry has continued to evolve and adapt to changing energy requirements and advances in technology. Energy storage systems provide a wide array of technological approaches to managing our power supply in order to create a more resilient energy infrastructure and bring cost savings to utilities and consumers.

Energy economics is a wide scientific subject area which includes topics related to supply and use of energy in societies. Due to diversity of issues and methods shared and applied with a number of academic disciplines, energy economics does not contemporary itself as a self-contained academic discipline, but it is an applied sub discipline of economics. Energy economics also draws deliberately on results of energy engineering, geology, political sciences, ecology etc. Recent focus of energy economics includes the following issues. Risk analysis and security of supply, climate change and climate policy, Demand response, Sustainability, Energy and economic growth.

Energy policy is the approach in which a given entity (often governmental) has decided to address issues of energy development including energy consumption, production and distribution. The attributes of energy policy may include legislation, international exposition, incentives to investment, and guidelines for energy conservation, taxation and other public policy techniques.

Sustainability science is the study of sustainable development and environmental science.Healthy ecosystems and environments are necessary to the survival of humans and other organisms. Ways of reducing negative human impact are environmentally-friendly chemical engineering, power engineering, environmental resources management and environmental protection. Information is gained from green chemistry, earth science, energy, environmental science and conservation biology. Ecological economics studies the fields of academic research that aim to address human economies and natural ecosystems.

Moving towards sustainability is also a social challenge that entails international and national law, urban planning and transport, local and individual lifestyles and ethical consumerism.

Fuel cells are very important as alternative power source for remote places where electrical sources are unavailable like remote rural area, big parks, faraway weather stations, spacecraft and a few military installations. There is no need to build electrical stations or bring large and expensive electrical components to these faraway areas. Fuel Economy and Emissions , Fuel cells, Fuel cell materials, Fuel cells and hydrogen storage.

Energy technology is an interdisciplinary engineering science having to do with the efficient, safe, environmentally friendly and economical extraction, conversion, transportation, storage and use of energy, targeted towards yielding high efficiency whilst skirting side effects on humans, nature and the environment. For people, energy is an overwhelming need and as a scarce resource it has been an underlying cause of political conflicts and wars. The gathering and use of energy resources can be harmful to local ecosystems and may have global outcomes.

Solar energy is the cleanest, most abundant renewable energy source available. The U.S. has some of the world’s richest solar resources. Today's technology allows us to harness this resource in several ways, giving the public and commercial entities flexible ways to employ both the light and heat of the sun. Solar energy can be deployed through distributed generation (DG), whereby the equipment is located on rooftops or ground-mounted arrays close to where the energy is used. Some solar technologies can also be built at utility-scale to produce energy as a central power plant.

Wind Power as an substitute to burning fossil fuels, is abundant, renewable, widely distributed, clean, produces no greenhouse gas radiations during operation, and uses little land. The net effects on the atmosphere are far less difficult than those of non-renewable power sources. Wind farms consist of many individual wind turbines which are connected to the electric power communication network.