Energy development is the ongoing effort to provide abundant an accessible energy, through knowledge, skills and constructions. When harnessing energy from primary energy sources and converting them into ever more convenient secondary energy forms, such as electrical energy and cleaner fuels, both quantity (harnessing more energy) and quality (more efficient use) are important.

Dependence on external energy sources

All biological life needs a supply of external energy. Most plants are capable of photosynthesis, some bacteria employ natural sources of chemical energy. Many other organisms thrive on energy passed along in food chains.

Beyond the biological needs of humanity, energy sources are used to eneable advanced activities such as heating, cooking, transport, communication, warfare and social and leisure activities. This allows us, in general, to live under diverse climatic conditions, in great numbers and often in comfort. Level of dependence of human societies on external energy sources differs, as does the climate, comfort and output of each society.

Increased levels of human comfort require increased dependence on external energy sources. Energy development therefore embodies the idea of increasing human comfort and freedom by researching and implementing increasingly effective and responsible energy harvesting and utilisation schemes.

Limitations to energy development

Use of any given energy source in human societies encounters limits to quantitative expansion. At the beginning of the 21st century some issues have achieved global dimension. Principal fossil energy sources, such as oil and natural gas are approaching exhaustion that may occur within the span of a generation (see Hubbert peak hypothesis). Closely linked to energy development are concerns about the environmental effects of energy use, such as climate changes. Energy development issues are part of the much debated sustainable development problem.

Energy sources

Energy sources are substances or processes with concentrations of energy at a high enough potential to be feasibly encouraged to convert to lower energy forms under human control for human benefit. Except for nuclear fuels, tidal energy and geothermal energy, all terrestrial energy sources are solar. And ultimately, solar energy itself is nuclear.

• Biomatter

All animals use food as an energy source. More recently, biomatter has been used to generate other forms of energy through burning, gasification, wet oxidation and bioconversion.

• Wind power

Wind turbines are used to generate electricity from the kinetic energy in winds.

• Hydropower

Water mills have been an important source of energy both anciently and in modern times. Nowadays dams generate 1/5th of the worlds electricity, mostly in large dams such as the Three Gorges Dam, or the planned Tekeze Hydro in Ethiopia.

• Solar cells

Photovoltaic cells use arriving light to excite electrons and produce usable electrical current.

• Geothermal energy

Nuclear fission inside the Earth produces heat. That heat is used to produce steam, which powers a turbine, generating electricity.

• Fossil fuels

Fossil fuels are ancient plant or animal matter that has decayed and been acted upon by geologic forces to produce hydrocarbons such as petroleum, natural gas or coal.

• Nuclear energy

Controlled nuclear reactions provide energy as one chemical element (atom) decays into a different one (fission), or as atoms are fused to form other atoms (fusion). In the process, some matter is transformed into energy.

Energy transportation

While new sources of energy are only rarely discovered or made possible by new technology, distribution technologie continually evolves. The use of fuel cells in cars, for example, is an anticipated delivery technology. This section presents some of the more common delivery technologies that have been important to historic energy development. They all rely in some way on the energy sources listed in the previous section.

• Fuels

Shipping is a flexible delivery technology that is used in the whole range of energy development regimes from primitive to highly advanced. Currently, coal,petroleum and their derivatives are delivered by shipping via boat, rail, or road. Petroleum and natural gas may also be delivered via pipeline. Refined hydrocarbon fuels such as gasoline and LPG may also be delivered via aircraft.

• Electric grids

Electricity grids are the networks used to transmit and distribute power from production source to end user, when the two may be hundreds of kilometres away. Sources include electrical generation plants such as a nuclear reactor, coal burning power plant, etc. A combination of sub-stations, transformers, towers, cables, and piping are used to maintain a constant flow of electricity.

Grids may suffer from transient blackouts and brownouts, often due to weather damage. During certain extreme space weather events solar wind can interfere with transmissions.

Grids also have a predefined carrying capacity or load that cannot safely be exceeded. When power requirements exeed what's available, failures are inevitable. To prevent problems, power is then rationed.

Industrialised countries such as Canada, the US, and Australia are among the highest per capita consumers of electricity in the world, which is possible thanks to a widespread electrical distribution network.

In the week of 3 August 2003 , the US set an all-time national record for electricity use of 90,000 gigawatts. CurrentEnergy provides a realtime overview of the electricity supply and demand for California, Texas, and the Northeast of the US. African countries with small scale electrical grids have a correspondingly low annual per capita usage of electricity. One of the most powerful powergrids in the world supplies power to the state of Queensland, Australia. This network's service provision and its administration is an ongoing issues for that states politicans.

Energy storage

Main article: Energy storage

While most fuels can be stored, electricity in itself cannot. For that reason, many methods of energy storage have been developed, which transform electrical energy into other forms of energy. A method of energy storage may be chosen based on stability, ease of transport, ease of energy release, or ease of converting free energy from the natural form to the stable form.

• Chemical

Some natural forms of energy are found in stable chemical compounds such as fossil fuels. Most systems of chemical energy storage result from biological activity, which store energy in chemical bonds. Man-made forms of chemical energy storage include hydrogen fuel, batteries and explosives such as cordite and dynamite.

• Gravitional

Dams can be used to store energy, by using excess energy to pump water into the reservoir. When electrical energy is required, the process is reversed. The water then turns a turbine, generating electricity. Hydroelectric power is currently an important part of the world's energy supply, generating one-fifth of the world's electricity. :[1].

Another example of gravitational energy storage is the counter-weight on elevators.

• Electrical capaticance

Electrical energy may be stored in capacitors. These are often used to produce high intensity releases of energy (such as a camera's flash)

• Mechanical

• Pressure:

Energy may also be stored pressurised gases or alternatively in a vacuum. Compressed air, for example, may be used to operate vehicles and power tools. Large scale compressed air energy storage facilities are used to smooth out demands on electricity generation by providing energy during peak hours and storing energy during off-peak hours. Such systems save on expensive generating capacity since it only needs to meet average consumption rather than peak consumption.

• Flywheels and springs

Energy can also be stored in mechanical systems such as springs or flywheels. Flywheel energy storage is currently being used for uninterruptible power supplies.

Historic energy development schemes

Human societies have relied and currently rely on various energy development schemes. Schemes that are most powerful are considered in the energy development field to be more advanced in that they contribute better to human comfort and freedom. As humans and societies move from more primitive energy development schemes to more advanced ones, it is typically said from an energy development point of view that they are advancing because the energy limits on comfort and freedom are shrinking. Sources and technologies in this section are presented in order of increasing energy development.

Future energy development

Main article: Future energy development

Extrapolations from current knowledge to future energy development offer a choice of energy futures. Some predictions parallel the Malthusian catastrophe hypothesis. Numerous are complex models based scenarios as pioneered by Limits to Growth. Modelling approaches offer ways to analyse diverse strategies, and hopefuly find a road to rapid and sustainable development of humanity. Short term energy crises are also a concern of energy development.

Existing technologies for new energy sources, such as new renewable energy technologies, nuclear fissionand fusion are promising, but need sustained research and development, including consideration of possible harmful side effects.