Portal:Energy

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The Energy Portal

Aleiha's parabolic solar cooker
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems. Since work is defined as a force acting through a distance (a length of space), energy is always equivalent to the ability to exert pulls or pushes against the basic forces of nature, along a path of a certain length.

Sustainable energy is the provision of energy that meets the needs of the present without compromising the ability of future generations to meet their needs. Sustainable energy sources are most often regarded as including all renewable energy sources, such as hydroelectricity, solar energy and power, wind power, wave power, geothermal energy and power, biomass fuel and energy, and tidal power. It usually also includes technologies that improve energy efficiency.

While many renewable energy projects are large-scale, renewable technologies are also suited to rural and remote areas, where energy is often crucial in human development. As of 2011, small solar photovoltaic (PV) systems provide electricity to a few million households, and micro-hydro configured into mini-grids serves many more. Over 44 million households use biogas made in household-scale digesters for lighting and/or cooking, and more than 166 million households rely on a new generation of more-efficient biomass cookstoves.

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Micro hydro scheme showing the power house, the penstock and the transmission lines
Microhydro power. Water power can be harnessed in many ways; tidal flows can be utilized to produce power by building a barrage across an estuary and releasing water in a controlled manner through a turbine; large dams hold water which can be used to provide large quantities of electricity; wave power is also harnessed in various ways. It is a technology that has been utilized throughout the world, by a diverse range of societies and cultures, for many centuries. Water can be harnessed on a large or a small scale. Micro-hydro power is the small-scale harnessing of energy from falling water; for example, harnessing enough water from a local river to power a small factory or village. This fact sheet will concentrate mainly at micro-hydro power.

In the UK, water mills are known to have been in use 900 years ago. Their numbers grew steadily and by the 19th century, there were over 20,000 in operation in England alone. In Europe, Asia and parts of Africa, water wheels were used to drive a variety of industrial machinery, such as mills and pumps. The first effective water turbines appeared in the mid 19th century and it was not long before they were replacing water wheels in many applications. In contrast to water wheels and the early turbines, modern turbines are compact, highly efficient and capable of turning at very high speed. Hydropower is a well-proven technology, relying on a non-polluting, renewable and indigenous resource, which can integrate easily with irrigation and water supply projects. China alone has more than 85,000 small-scale, electricity producing, hydropower plants. Over the last few decades, there has been a growing realisation in developing countries that micro-hydro schemes have an important role to play in the economic development of remote rural areas, especially mountainous ones. Micro-hydro schemes can provide power for industrial, agricultural and domestic uses through direct mechanical power or by the coupling of the turbine to a generator to produce electricity.

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Biofuels: Anaerobic digestion · Alcohol fuels · Algae fuel · Biodiesel · Biogas · Biogasoline · Wood


Energy crops: Barley · Cassava · Hemp · Potato · Rice · Soybean · Wheat


Energy use: Heating and cooling ·


Energy storage: Alkaline versus rechargeable batteries · Animal-based · Electrochemical cell · Fuel cells · How to - Battery charger · Mass-based · Solar panel · Spring based


Geothermal power:


Greenhouses: Construction of an Affordable Greenhouse · Humboldt greenhouse gallery


Passive solar design: Parras passive solar design gallery · Thermal mass · Thermosiphon


Photovoltaics: Energy · System energy · Grid connection · Holographic solar · Humbolt gallery · Maintenance · Panels · Parras gallery · Refrigeration · Vaccine refrigeration · Test field · Troubleshooting · Rural lighting · Water pumping


Solar cooking: Analysis of a solar cooker  · and development · and health


Solar dehydrating: Food Drying with Superheated Steam · Solar drying in Uganda


Solar distillation: Compound parabolic concentrator · Effect of water on light transmission of glass · Improving Basin Solar Stills · Solar distillation TB · Solar fuel alcohol distillation


Solar energy: Open Solar Outdoors Test Field · Smart windows · The solar resource


Solar hot water: DIY solar thermal collectors · Installation and Design Principles · System types


Solar power: Heliostats · Solar thermal energy


Water: Hydraulic ram pumps · Hydroelectricity · Microhydro power · Rope pump


Wind power: Types of wind turbines (Small) · Windmill · Windpumps

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