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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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The Geysers in Northern California.
Geothermal power is generated from the high temperatures that can be found in various parts of the earth's crust such as volcanoes, hot springs, and geysers. The water that surrounds and fills the gaps between the rocks in the crust is raised in temperature by these natural processes. This hot water is then pumped to the surface and its steam is captured and used to create electrical power through a turbine system.

There are three common types of geothermal power: dry steam, flash steam, and binary cycle. Dry steam is rare and uses the steam directly from the earth, flash steam pumps the hot water that naturally occurs in the earth to the surface and utilizes its steam, and binary cycle uses a secondary fluid and its vapor to power a generator.

Dry stream geothermal plants use natural steam directly from the Earth. Once the steam pocket is tapped, the steam is channeled directly into a turbine which converts the thermal energy into electrical power.

Flash stream power hot water is pumped up to the surface of the earth, where its pressure is lessened and it is separated into steam and cool water. The steam is then collected and sent to a turbine to generate electrical power, while the cooled water is pumped back down to the geothermal area in the crust to continue in the cycle.

Power from the geothermal binary cycle is generated when water with a small amount of heat is pumped from the source to a heat exchanger to vaporize a secondary liquid with a much lower boiling temperature than water. That vapor is sent to the turbine to generate electrical power. The water returns to the source to complete the cycle again.

Floating drum biogas digestor

Above ground portion of floating drum biogas digestor - used chiefly for digesting animal and human feces on a continuous-feed mode of operation, i.e. with daily input.

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Selected topics (Book)

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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