Alternative Energy that works!

Solar energy

In this context, "solar energy" refers to energy that is directly collected from sunlight. However, most fossil and renewable energy sources are ultimately derived from "solar energy" so some ascribe much broader meanings to the term.

Solar energy can be applied in many ways, including to:

* generate electricity using photovoltaic solar cells
* generate electricity using concentrated solar power
* generate electricity by heating trapped air which rotates turbines in a Solar updraft tower.
* heat buildings, directly. Careful positioning of windows and use of brises soleil can maximise inflow of light at the times it is most needed, heating the building while preventing overheating during midday and summer.
* heat foodstuffs, through solar ovens.
* heat water for domestic consumption and heating using rooftop solar panels.
* heat and cool air through use of solar chimneys.

Obviously the sun does not provide constant energy to any spot on the Earth, so its uninterrupted use requires a means for energy storage. This is typically accomplished by battery storage. However, battery storage implies energy losses. Some homeowners use a grid-connected solar system which feeds energy to the grid during the day, and draw energy from the grid at night; this way no energy is expended for storage.

Advantages from solar energy sources include the inexhaustible supply of energy and zero emissions of greenhouse gas and air pollutants. Shortcomings include, depending on application:

* intermittency, e.g. that it is not available at night.
* Solar panels are in many applications considerably more expensive than alternatives.
* The current generated is only of DC type, and must be converted if transmission over the grid is needed.



Geothermal energy

Geothermal energy is energy obtained by tapping the heat of the earth itself, usually from kilometers deep into the Earth's crust. Ultimately, this energy derives from the radioactive decay in the core of the Earth, which heats the Earth from the inside out. This energy can be used in three ways:

* Geothermal electricity
* Geothermal heating, through deep Earth pipes
* Geothermal heating, through a heat pump.

Usually, the term 'geothermal' is reserved for thermal energy from within the Earth.

Geothermal electricity is created by pumping a fluid (oil or water) into the Earth, allowing it to evaporate and using the hot gases vented from the earth's crust to run turbines linked to electrical generators.

The geothermal energy from the core of the Earth is closer to the surface in some areas than in others. Where hot underground steam or water can be tapped and brought to the surface it may be used to generate electricity. Such geothermal power sources exist in certain geologically unstable parts of the world such as Iceland, New Zealand, United States, the Philippines and Italy. The two most prominent areas for this in the United States are in the Yellowstone basin and in northern California. Iceland produced 170 MW geothermal power and heated 86% of all houses in the year 2000 through geothermal energy. Some 8000 MW of capacity is operational in total.

Geothermal heat from the surface of the Earth can be used on most of the globe directly to heat and cool buildings. The temperature of the crust a few feet below the surface is buffered to a constant 7 to 14 °C (45 to 58 °F), so a liquid can be pre-heated or pre-cooled in underground pipelines, providing free cooling in the summer and, via a heat pump, heating in the winter. Other direct uses are in agriculture (greenhouses), aquaculture and industry.

Although geothermal sites are capable of providing heat for many decades, eventually specific locations cool down. Some interpret this as meaning a specific geothermal location can undergo depletion, and question whether geothermal energy is truly renewable.

Small scale geothermal heating can also be used to directly heat buildings: there are many names for this technology including "Ground Source Heat Pump" technology, and "Geoexchange".


Biofuel

Plants use photosynthesis to store solar energy in the form of chemical energy. Biofuel is any fuel that derives from biomass, including living organisms or their metabolic byproducts, such as cow manure.

Typically biofuel is burned to release its stored chemical energy. Research into more efficient methods of converting biofuels and other fuels into electricity utilizing fuel cells is an area of very active work. Biomass, also known as biomatter, can be used directly as fuel or to produce liquid biofuel. Agriculturally produced biomass fuels, such as biodiesel, ethanol and bagasse (often a by-product of sugar cane cultivation) can be burned in internal combustion engines or boilers.

Biogas is a biofuel produced through the intermediary stage of anaerobic digestion. Biogas consists mainly (45-90%) biologically produced methane.

A drawback is that all biomass needs to go through some of these steps: it needs to be grown, collected, dried, fermented and burned. All of these steps require resources and an infrastructure. However, the United States government passed legislation that requires the integration of 7.5 billion U.S. gallons (28,000,000 m³) of ethanol into the gasoline supply experts estimate that six billion dollars of investment will be created along with 200,000 additional jobs in the United States.

Biomatter energy, under the right conditions, is considered to be renewable.


Liquid biofuel

Liquid biofuel is usually bioalcohol such as ethanol and biodiesel and virgin vegetable oils. Biodiesel can be used in modern diesel vehicles with little or no modification to the engine and can be obtained from waste and virgin vegetable and animal oil and fats (lipids). Virgin vegetable oils can be used in modified diesel engines. In fact the Diesel engine was originally designed to run on vegetable oil rather than fossil fuel. A major benefit of biodiesel is lower emissions. The use of biodiesel reduces emission of carbon monoxide and other hydrocarbons by 20 to 40 percent. In some areas corn, sugarbeets, cane and grasses are grown specifically to produce ethanol (also known as alcohol) a liquid which can be used in internal combustion engines and fuel cells. Ethanol is being phased into the current energy infrastructure. E85 is a fuel composed of 85% ethanol and 15% gasoline that is currently being sold to consumers.

The EU plans to add 5% bioethanol to Europe's petrol by 2010. For the UK alone the production would require 12,000 square kilometres of the country's 65,000 square kilometres of arable land assuming that no biofuels are created using waste produces from other agriculture. The supermarket chain Tesco has started adding the 5% bioethanol to the petrol it sells as of January 2006.

In the future, there might be bio-synthetic liquid fuel available. It can be produced by Fischer-Tropsch processes, also called Biomass-To-Liquids (BTL).


Solid biomass

Direct use is usually in the form of combustible solids, either wood, the biogenic portion of municipal solid waste or combustible field crops. Field crops may be grown specifically for combustion or may be used for other purposes, and the processed plant waste then used for combustion. Most sorts of biomatter, including dried manure, can actually be burnt to heat water and to drive turbines.

Sugar cane residue, wheat chaff, corn cobs and other plant matter can be, and is, burnt quite successfully. The process releases no net CO2.

Solid biomass can also be gasified, and used as described in the next section.


Biogas

Many organic materials can release gases, due to metabolisation of organic matter by bacteria (anaerobic digestion, or fermentation). Landfills actually need to vent this gas (called landfill gas) to prevent dangerous explosions. Animal feces releases methane under the influence of anaerobic bacteria.

Also, under high pressure, high temperature, anaerobic conditions many organic materials such as wood can be gasified to produce gas. This is often found to be more efficient than direct burning. The gas can then be used to generate electricity and/or heat.

Biogas can easily be produced from current waste streams, such as: paper production, sugar production, sewage, animal waste and so forth. These various waste streams have to be slurried together and allowed to naturally ferment, producing methane gas. This can be done by converting current sewage plants into biogas plants. When a biogas plant has extracted all the methane it can, the remains are sometimes better suitable as fertilizer than the original biomass.

Alternatively biogas can be produced via advanced waste processing systems such as mechanical biological treatment. These systems recover the recyclable elements of household waste and process the biodegradable fraction in anaerobic digesters.

Renewable natural gas is a biogas which has been upgraded to a quality similar to natural gas. By upgrading the quality to that of natural gas, it becomes possible to distribute the gas to the mass market via the existing gas grid.'