IDENTIFY ALTERNATIVE ENERGY RESOURCES SUCH AS WIND, SOLAR, HYDROELECTRIC, GEOTHERMAL, AND BIOFUELS.

Biofuels are produced from living organisms or from m e t a b o l i c b y - p r o d u c t s (o rgan ic o r food was te products). In order to be considered a biofuel the fuel must contain over 80 percent

renewable materials. It is originally derived from the photosynthesis process and can the re fo re o f t en be referred to as a solar energy source. There are many pros

and cons to using biofuels as an energy source.

Biofuels

Biofuel offers an alternative to gasoline that is carbon-neutral and can be produced in a sustainable fashion. (Image from the U.S. Department of Energy)

FUEL FROM CHICKEN FEATHERS? ALGAE TO ELECTRICITY POWER FROM POTATOES

ALTERNATIVE ENERGY

GEOTHERMAL ENERGY

• Geothermal energy is made inside the Earth.• The world geothermal comes from Greek words

meaning ‘Earth’ (geo) and ‘heat’ (thermos).• The technology behind geothermal electricity generation

has improved substantially but it still only provides a fraction of world electricity generation.

• Geothermal power is clean, reliable and cost effective but its availability is often limited to areas near tectonic plate boundaries.

• Geothermal power plants in the Philippines and Iceland contribute around 30% of their electricity production. In the USA it is less than 1%.

• As of 2010, 24 countries around the world use geothermal power to generate electricity while around 70 use it for various forms of heating.

• Geothermal heating applications include industrial uses, heat pumps, space heating and bathing in hot springs.

• Humans have enjoyed geothermal energy in the form of hot springs for thousands of years.

• The oldest known spa fed from a hot spring is believed to be a stone pool found on Lisan Mountain in China, built in the 3rd century BC.

• In some parts of Iceland, hot water runs from geothermal power plants under pavements and roads to help melt ice.

Hydropower is electricity generated using the energy of moving water. Rain or melted snow, usually originating in hills and mountains, create streams and rivers that eventually run to the ocean. The energy of that moving water can be substantial, as anyone who has been whitewater rafting knows.

This energy has been exploited for centuries. Farmers since the ancient Greeks have used water wheels to grind wheat into flour. Placed in a river, a water wheel picks up flowing water in buckets located around the wheel. The kinetic energy of the flowing river turns the wheel and is converted into mechanical energy that runs the mill.

In the late 19th century, hydropower became a source for generating electricity. The first hydroelectric power plant was built at Niagara Falls in 1879. In 1881, street lamps in the city of Niagara Falls were powered by hydropower. In 1882 the world’s first hydroelectric power plant began operating in the United States in Appleton, Wisconsin.

A typical hydro plant is a system with three parts: an electric plant where the electricity is produced; a dam that can be opened or closed to control water flow; and a reservoir where water can be stored. The water behind the dam flows through an intake and pushes against blades in a turbine, causing them to turn. The turbine spins a generator to produce electricity. The amount of electricity that can be generated depends on how far the water drops and how much water moves through the system. The electricity can be transported over long-distance electric lines to homes, factories, and businesses.

Hydroelectric power provides almost one-fifth of the world's electricity. China, Canada, Brazil, the United States, and Russia were the five largest producers of hydropower in 2004.

The biggest hydro plant in the United States is located at the Grand Coulee Dam on the Columbia River in northern Washington. More than 70 percent of the electricity made in Washington State is produced by hydroelectric facilities.

Hydropower is the cheapest way to generate electricity today. That's because once a dam has been built and the equipment installed, the energy source—flowing water—is free. It's a clean fuel source that is renewable yearly by snow and rainfall.

HydroelectricHYDRO POWER

HTTP://ENVIRONMENT.NATIONALGEOGRAPHIC.COM/ENVIRONMENT/GLOBAL-WARMING/HYDROPOWER-PROFILE/#CLOSE-MODAL

SOLAREvery hour the sun beams onto Earth more than enough energy to satisfy global energy needs for an entire year. Solar energy is the technology used to harness the sun's energy and make it useable. Today, the technology produces less than one tenth of one percent of global energy demand.

Many people are familiar with so-called photovoltaic cells, or solar panels, found on things like spacecraft, rooftops, and handheld calculators. The cells are made of semiconductor materials like those found in computer chips. When sunlight hits the cells, it knocks electrons loose from their atoms. As the electrons flow through the cell, they generate electricity.

On a much larger scale, solar thermal power plants employ various techniques to concentrate the sun's energy as a heat source. The heat is then used to boil water to drive a steam turbine that generates electricity in much the same fashion as coal and nuclear power plants, supplying electricity for thousands of people.

In one technique, long troughs of U-shaped mirrors focus sunlight on a pipe of oil that runs through the middle. The hot oil then boils water for electricity generation. Another technique uses moveable mirrors to focus the sun's rays on a collector tower, where a receiver sits. Molten salt flowing through the receiver is heated to run a generator.

Other solar technologies are passive. For example, big windows placed on the sunny side of a building allow sunlight to heat-absorbent materials on the floor and walls. These surfaces then release the heat at night to keep the building warm. Similarly, absorbent plates on a roof can heat liquid in tubes that supply a house with hot water.

The technology is also versatile. For example, solar cells generate energy for far-out places like satellites in Earth orbit and cabins deep in the Rocky Mountains as easily as they can power downtown buildings and futuristic cars.

But solar energy doesn't work at night without a storage device such as a battery, and cloudy weather can make the technology unreliable during the day. Solar technologies are also very expensive and require a lot of land area to collect the sun's energy at rates useful to lots of people.

Despite the drawbacks, solar energy use has surged at about 20 percent a year over the past 15 years, thanks to rapidly falling prices and gains in efficiency. Japan, Germany, and the United States are major markets for solar cells. With tax incentives, solar electricity can often pay for itself in five to ten years.

WIND ENERGY

Wind is the movement of air from an area of high pressure to an area of low pressure. In fact, wind exists because the sun unevenly heats the surface of the Earth. As hot air rises, cooler air moves in to fill the void. As long as the sun shines, the wind will blow. And as long as the wind blows, people will harness it to power their lives.

Ancient mariners used sails to capture the wind and explore the world. Farmers once used windmills to grind their grains and pump water. Today, more and more people are using wind turbines to wring electricity from the breeze. Over the past decade, wind turbine use has increased at more than 25 percent a year. Still, it only provides a small fraction of the world's energy.

Most wind energy comes from turbines that can be as tall as a 20-story building and have three 200-foot-long (60-meter-long) blades. These contraptions look like giant airplane propellers on a stick. The wind spins the blades, which turn a shaft connected to a generator that produces electricity. Other turbines work the same way, but the turbine is on a vertical axis and the blades look like a giant egg beater.

The biggest wind turbines generate enough electricity to supply about 600 U.S. homes. Wind farms have tens and sometimes hundreds of these turbines lined up together in particularly windy spots, like along a ridge. Smaller turbines

erected in a backyard can produce enough electricity for a single home or small business.

Wind is a clean source of renewable energy that produces no air or water pollution. And since the wind is free, operational costs are nearly zero once a turbine is erected. Mass production and technology advances are making turbines cheaper, and many governments offer tax incentives to spur wind-energy development.

Some people think wind turbines are ugly and complain about the noise the machines make. The slowly rotating blades can also kill birds and bats, but not nearly as many as cars, power lines, and high-rise buildings do. The wind is also variable: If it's not blowing, there's no electricity generated.

Nevertheless, the wind energy industry is booming. Globally, generation more than quadrupled between 2000 and 2006. At the end of last year, global capacity was more than 70,000 megawatts. In the energy-hungry United States, a single megawatt is enough electricity to power about 250 homes. Germany has the most installed wind energy capacity, followed by Spain, the United States, India, and Denmark. Development is also fast growing in France and China.

Industry experts predict that if this pace of growth continues, by 2050 the answer to one third of the world's electricity needs will be found blowing in the wind.

Energy Pro Con

How it is harnessed,

and/or from what

it halesBiofuel-

Geothermal-

Hydroelectric-

Solar

Wind Energy-

Fossil Fuels-