Green Power - Alternative Energy Sources

Green Power - Alternative Energy Sources

We use energy for industry, business, residential consumption, and transportation. Oil, coal, natural gas, and nuclear are non-renewable energy sources that account for 93% of the energy used worldwide. Only 7% is derived from renewable sources—what we call “green energy” or, more often, alternative energy. Alternative energy sources include hydroelectric, wind, solar, biomass, biofuel, and geothermal.

Hydroelectric Energy
Hydropower, the largest form of alternative energy, is derived by harnessing energy from moving water. From the earliest use of a waterwheel to grind grain, forge metals, or make paper to today’s massive hydroelectric plants that provide electricity to entire cities, mankind has learned to harness the power of moving water.
Hydroelectric Power from Large Dams
Dams were first used for hydropower around 1890. There were more than 45,000 large dams in more than 140 countries by the end of the 20th century. But only a fraction of these dams are used for hydropower. Most are used for irrigation, flood control, and water supply. The percentage of dams constructed for hydropower has been decreasing over the last 20 years. In the year 2000, the distribution of large hydropower dams was as follows: Africa 6%; North America 11%, South America 26%; Asia 7%; Australasia (Australia, New Zealand, New Guinea and neighboring islands) 19%, and Europe 31%.
Hydropower provides 96% of the renewable energy utilized in the United States, though it provides only 10-11% of its electricity.
Hydropower can be generated from the movement of any body of water. Rivers,
movement of any body of water. Rivers, waterfalls, streams, ocean tides, and ocean waves are all potential energy sources.
When we think of hydropower, we usually imagine a massive dam. Behind the dam, water is backed up to form a reservoir or an artificial lake. Gravity pulls water into the intake area from the reservoir where it flows through a penstock (a chute, sluice, tunnel, or pipe) downhill to pass through a turbine propeller, which spins the turbine shaft. The hydraulic turbine converts mechanical energy into electricity. [For an interesting in-depth explanation and great graphics, check out the U.S. Geological Services website.]
Although hydro-electrical power is green energy that is clean, renewable, and sustainable, it has negative environmental and societal impacts.
Damming a river creates a reservoir which floods a large area, burying whatever was there before, whether it was a town or a wilderness area. Rotting vegetation releases methane gas. Habitats are destroyed. Natural fish migration is disrupted. Water released through the dam carries less silt and it scours and erodes the banks and the riverbed downstream.
The World Commission on Dams report (Nov. 2000) estimates 40-80 million people have been displaced through forced
resettlement due to dam construction, with whole societies losing their cultural heritage, their homes, and their livelihoods. Many did not receive any form of compensation or resettlement assistance.
Downstream communities are at great risk if a dam fails. The Association of State Dam Safety Officials has concluded that the U.S. safety expenditures for dams are insufficient. They rate 9,326 of the 80,000 large and small dams in the U.S. as high hazard and 1,600 of these dams lie within one mile upstream of a city. Less than 40% of high hazard dams have an emergency action plan for nearby residents to follow.
Smaller Dams and Run-of-the-River Systems
Smaller dams and run-of-the-river systems exert less environmental and societal impact. A smaller dam may be built with storage and pumping capacity, reusing water it pumps back into its reservoirs. Run-of-the-river systems either place turbines within the river or divert water through pipes which run through a turbine and flow back into the river downstream.
If we are to increase our use of inland hydropower as an alternative power source with low impact on the environment, we must do a better job of assessing and mitigating its
short-term and long-term consequences.
Energy from the Ocean Tides
Tidal energy plants build a low dam or barrage across an inlet. Water passes through gates or sluices into the inlet. When the tide goes out, it turns turbines to produce energy. There is no pollution, the fuel is free, the plants are easy to maintain, and they should last for a hundred years. Unfortunately, there are few locations in which to build them. Construction costs are expensive. Fortunately the environmental impact appears to be minimal. The French tidal plant, La Rance, has been producing electricity since 1968.
Energy from Ocean Waves
There are several ways to capture energy from ocean waves. Wave motion can push air through a pipe; the air spins a turbine. Or water can be focused into a narrow channel to increase its power and is used to spin turbines or can be channeled into a catch basin. Currently this potential energy source is being explored for use in Japan, but there are no large commercial energy wave plants at this time. One demonstration tower built in Norway proves the potential of this technology with one drawback, noise pollution. The whine of the turbines can be heard for miles.
Ocean Thermal Energy Conversion
In tropical areas where the difference between the surface temperature of the water and the deep water temperature is 38 degrees or more, this difference in temperature can be used to create energy. Hawaii has experimented with ocean thermal energy conversion since the 1970s, but it is estimated to be 15-20 years before this technology, which is limited to tropical climates, will be available.
Wind Energy
Windmills have been used to harness energy for thousands of years, first for transportation (sailing ships), later for grinding grain and pumping water. Today, single wind towers are providing green energy to isolated homes or farms, while large-scale wind farms are being built both on land and off shore to provide energy for national electrical grids and pre-planned communities.
The U.S. Department of Energy’s website states, “Today, U.S. wind energy installations produce enough electricity on a typical day to power the equivalent of more than 9.7 million homes. The five-year average annual growth rate for the wind industry is now 39%, up from 32% between 2003 and 2008. America's wind power fleet will avoid an estimated 62 million tons of carbon dioxide annually, equivalent to taking 10.5 million cars off the road, and will conserve approximately 20 billion gallons of water annually, which would otherwise be consumed for steam or cooling in conventional power plants.”
Wind energy is gaining in popularity across the world. Britain is investing in offshore wind farms with a goal of generating enough green power to light every home in Britain by wind energy. European countries, Canada, the U.S., Brazil, China, India, and Mexico are all pursuing wind as a viable source of energy.
This renewed interest has resulted in vast improvements in wind tower design and efficiency. It has also sparked creative and innovative ideas such as wind kites; deep water (floating rather than fixed), off-shore wind farms; and overhead turbines placed on freeways that are powered by wind created by passing cars.
While wind power is sustainable and pollution free, the power generated is intermittent. Noise has been cited as a factor. A cute video comparing the noise of a single tower to everyday urban and rural noise suggests traffic noise is much more disruptive. Many argue the huge towers are an eyesore, whether onshore or offshore. Bird and bat mortality is also a consideration, but this issue is being researched and addressed by the industry.
Solar Energy
By far the most utilized alternative power source throughout mankind’s history, solar power seems to have been the least exploited in recent years. Solar energy, both active and passive, is a well known source of power. But for years we have heard large scale use is cost prohibitive, takes up too much space, is too affected by the weather, and produces too little output. Due to the rising costs of fossil fuel, new research, new technology, and new application will hopefully give rise to an increase in the use of solar power.
Whether active or passive, or photovoltaic, solar lends itself to onsite green energy applications. Active solar energy can be used to heat hot water, an obvious need, but heated water can also be used to heat a home or pool and solar energy can be used to heat air. Solar panels can also be used to create electricity, while passive solar design utilizes the sun’s rays for both heat and light.
Solar energy plants (also called thermal plants) collect the suns energy and convert it to electricity through various means. Solar cells are the most widely known, but solar energy can also be used to make steam
which is used like wind or water to turn turbines.
Solar energy is clean, renewable, free and worldwide, but of course can be collected only during daylight hours. Pollution and cloud cover adversely affect solar power collection, but newer technology is addressing these factors.
Like wind technology, investment in solar research and design is booming. It will be exciting to see what the next few years hold in store for utilization of this age old resource.
Biomass and Biofuel
Biomass is used as a fuel or is converted to biofuel. Biomass is organic matter, vegetable or animal, including crops, wood, refuse from industry such as paper mills, or matter from landfills. It can be burned to create electricity; gases from decomposition can be collected and used, or crops can be grown to make fuel, such as corn grown to make ethanol.
Proponents argue that burning biomass, which releases CO2 into the atmosphere, is green power because it is part of the carbon cycle. They claim, on the other hand, that burning fossil fuels disrupts the carbon cycle. If the Earth is viewed as a closed system, this logic seems suspect and a weak argument for cutting down forests for biofuel.
It is interesting, however, to remember that Henry Ford built a car out of biomass that was stronger than steel. And the fuel he chose was made from the oil of seeds. Today we are manufacturing new bio-degradable plastics from biomass and raising crops for ethanol. But it is essential we consider the entire impact of turning to biofuels to replace fossil fuels, including the stewardship of croplands and food sources.
Geothermal Energy
Geothermal energy can refer to the use of the Earth to provide heating and/or cooling on a small scale through the design of a home or through the utilization of a heat pump. Or it can refer to the use of the Earth’s heat to run power plants.
Geothermal Design and Heat Pumps
If you dig below the frost line, the temperature of the ground remains constant—about 50 degrees. This median temperature can be used as an aid to cool a building in the summer and heat it in the winter. Combined passive solar and geothermal designs circulate air around and under a building, venting heat in the summer, trapping it in the winter.
Heat pumps pipe water or coolant
underground to heat or cool it to 50 degrees, cutting down on the amount of electricity needed to reach the desired temperature.
Geothermal Plants
The depth of the Earth’s crust varies on average from 5-25 miles deep. But there are places on the Earth where magma oozes or explodes to the surface, mud flats boil and bubble, and steam shoots into the sky. And there are places where the Earth’s crust is thin and drilling below the surface can easily tap into heat sources below.
Geothermal power plants use water, steam, and/or heat from below the Earth’s crust to make electricity or to provide a direct source of heat. Underground bodies of water heated by hot rocks or magma can be pumped through buildings, under streets, and under sidewalks. In Iceland, this method is used to heat most of the homes and commercial buildings in the nation.
Geothermal electric power plants use steam to turn turbines and make electricity in one of three ways: a direct source of steam is tapped, hot water sources are tapped and turned into steam, or above ground water sources are diverted into deep wells where water is heated by hot rocks or magma and turned into steam. One process utilizes chemicals in addition to hot water to make steam.

Proponents of geothermal energy tell us it is safe, sustainable, and non-polluting. These sweeping statements are not entirely true. Destruction from drilling, landslides, earthquakes, and pollution from released gases and toxic elements impact the environment.
A geothermal plant in California, believing their source of steam to be an inexhaustive supply, vented the steam rather than capturing it and returning it to the source. The underground water source, which had produced geysers for thousands of years, was depleted.
Open system plants vent steam along with gases such as hydrogen sulfide, carbon dioxide, ammonia, and methane and toxic elements such as mercury and arsenic, though some systems capture gases and other pollutants and either return them to the source or utilize them. But accidents can happen as well. A blow-out in a Hawaiian geothermal plant caused toxic gases to spew into the sky for thirty hours.
Enhanced Geothermal Systems (EGS) drill down to dry, hot, non-porous rock and pump in water under high pressure into the well to create steam which rises through a second bore hole. The water, once cooled, is again injected into the well in a closed loop system.
One plant in Switzerland was forced to close within days of starting operation due to seismic activity generated by this process. But EGS technology is in its infancy. New research is underway using carbon dioxide instead of water for EGS systems.