Many nations count on coal, oil and natural gas to supply most of their energy needs, but reliance on fossil fuels presents a big problem. Fossil fuels are a finite resource. Eventually, the world will run out of fossil fuels, or it will become too expensive to retrieve those that remain. Fossil fuels also cause air, water and soil pollution, and produce greenhouse gases that contribute to global warming.
Renewable energy resources, such as wind, solar and hydropower, offer clean alternatives to fossil fuels. They produce little or no pollution or greenhouse gases, and they will never run out.
Wind Power
Wind power is actually a form of solar power, because wind is caused by heat from the sun. Solar radiation heats every part of the Earth’s surface, but not evenly or at the same speed. Different surfaces—sand, water, stone and various types of soil-absorb, retain, reflect and release heat at different rates, and the Earth generally gets warmer during daylight hours and cooler at night.
As a result, the air above the Earth’s surface also warms and cools at different rates. Hot air rises, reducing the atmospheric pressure near the Earth’s surface, which draws in cooler air to replace it. That movement of air is what we call wind.
When air moves, causing wind, it has kinetic energy-the energy created whenever mass is in motion. With the right technology, the wind’s kinetic energy can be captured and converted to other forms of energy such as electricity or mechanical power. That’s wind power.
Just as the earliest windmills in Persia, China and Europe used wind power to pump water or grind grain, today’s utility-connected wind turbines and multi-turbine wind farms use wind power to generate clean, renewable energy to power homes and businesses.
Wind power should be considered an important component of any long-term energy strategy, because wind power generation uses a natural and virtually inexhaustible source of power—the wind—to produce electricity. That is a stark contrast to traditional power plants that rely on fossil fuels.
And wind power generation is clean; it doesn’t cause air, soil or water pollution. That’s an important difference between wind power and some other renewable energy sources, such as nuclear power, which produces a vast amount of hard-to-manage waste.
One obstacle to increasing worldwide use of wind power is that wind farms must be located on large tracts of land or along coastlines to capture the greatest wind movement.
Devoting those areas to wind power generation sometimes conflicts with other priorities, such as agriculture, urban development, or waterfront views from expensive homes in prime locations.
As the need for clean, renewable energy increases, and the world more urgently seeks alternatives to finite supplies of oil, coal and natural gas, priorities will change.
And as the cost of wind power continues to decline, due to technology improvements and better generation techniques, wind power will become increasingly feasible as a major source of electricity and mechanical power.
Hydropower
Water flowing downstream is a powerful force. Water is a renewable resource, constantly recharged by the global cycle of evaporation and precipitation. The heat of the sun causes water in lakes and oceans to evaporate and form clouds. The water then falls back to Earth as rain or snow, and drains into rivers and streams that flow back to the ocean. Flowing water can be used to power water wheels that drive mechanical processes. And captured by turbines and generators, like those housed at many dams around the world, the energy of flowing water can be used to generate electricity.
Biomass Energy
Biomass has been an important source of energy ever since people first began burning wood to cook food and warm themselves against the winter chill. Wood is still the most common source of biomass energy, but other sources of biomass energy include food crops, grasses and other plants, agricultural and forestry waste and residue, organic components from municipal and industrial wastes, even methane gas harvested from community landfills. Biomass can be used to produce electricity and as fuel for transportation, or to manufacture products that would otherwise require the use of non-renewable fossil fuels.
Hydrogen
The jury is still out on whether hydrogen will ultimately be our environmental saviour, replacing the fossil fuels responsible for global warming and various nagging forms of pollution. Two main hurdles stand in the way of mass production and widespread consumer adoption of hydrogen “fuel-cell” vehicles: the still high cost of producing fuel cells; and the lack of a hydrogen refuelling network.
Reining in manufacturing costs of fuel-cell vehicles is the first major issue the automakers are addressing. While several have fuel-cell prototype vehicles on the road—Toyota and Honda are even leasing them to the public in Japan and California—they are spending upwards of $1 million to produce each one due to the advanced technology involved and low production runs. Toyota hopes to reduce its costs per fuel-cell vehicle to around $50,000 by 2015, which would make such cars economically viable in the marketplace. On this side of the Pacific, General Motors plans to sell hydrogen-powered vehicles in the United States by 2010.
Another problem is the lack of hydrogen refuelling stations. Major oil companies have been loath to set up hydrogen tanks at existing gas stations for many reasons, ranging from safety to cost to lack of demand. But obviously the oil companies are also trying to keep customers interested in their highly profitable bread-and-butter product: gasoline. A more likely scenario is what is emerging in California, where some 38 independent hydrogen fuel stations are located around the state as part of a network created by the non-profit California Fuel Cell Partnership, a consortium of automakers, state and federal agencies, and other parties interested in furthering hydrogen fuel-cell technologies.
The benefits of ditching fossil fuels for hydrogen are many, of course. Burning fossil fuels like coal, natural gas and oil to heat and cool our buildings and run our vehicles takes a heavy toll on the environment, contributing significantly to both local problems such as elevated particulate levels and global ones such as a warming climate. The only by-product of running a hydrogen-powered fuel cell is oxygen and a trickle of water, neither of which will cause any harm to human health or the environment.
But right now, 95 percent of the hydrogen available in the United States is either extracted from fossil fuels or made using electrolytic processes powered by fossil fuels, thus negating any real emissions savings or reduction in fossil-fuel usage. Only if renewable energy sources-solar, wind and others-can be harnessed to provide the energy to process hydrogen fuel can the dream of a truly clean hydrogen fuel be realized.
Stanford University researchers in 2005 assessed the environmental effects of three different hydrogen sources: coal, natural gas, and water electrolysis powered by wind. They concluded that we’d lower greenhouse gas emissions more by driving gasoline/electric hybrid cars than by driving fuel-cell cars run on hydrogen from coal. Hydrogen made using natural gas would fare a little bit better in terms of pollution output, while making it from wind power would be a slam-dunk for the environment.
Geothermal Energy
The heat inside the Earth produces steam and hot water that can be used to power generators and produce electricity, or for other applications such as home heating and power generation for industry. Geothermal energy can be drawn from deep underground reservoirs by drilling or from other geothermal reservoirs closer to the surface.
Ocean
As any board or body surfer will tell you, the ocean’s tidal currents pack considerable wallop. So why wouldn’t it make sense to harness all that formidable ocean power-which is not unlike that of the rivers that drive hydropower dams or the wind that drives wind turbines-to make energy?
The concept is simple, says John Lienhard, a University of Houston mechanical engineering professor: “Every day the moon’s gravitational pull lifts countless tons of water up into, say, the East River or the Bay of Fundy. When that water flows back out to sea, its energy dissipates and, if we don’t use it, it’s simply spent.”
According to Energy Quest, an educational website of the California Energy Commission, the sea can be harnessed for energy in three basic ways: using wave power, using tidal power, and using ocean water temperature variations in a process called “ocean thermal energy conversion”.
- In harnessing wave power, the back-and-forth or up-and-down movement of waves can be captured, for example, to force air in and out of a chamber to drive a piston or spin a turbine that can power a generator. Some systems in operation now power small lighthouses and warning buoys.
- Harnessing tidal energy, on the other hand, involves trapping water at high tide and then capturing its energy as it rushes out and drops in its change to low tide. This is similar to the way water makes hydroelectric dams work. Already some large installations in Canada and France generate enough electricity to power thousands of homes.
- An OTEC system uses temperature differences between deep and surface waters to extract energy from the flow of heat between the two. An experimental station in Hawaii hopes to develop the technology and someday produce large amounts of electricity on par with the cost of conventional power technologies.
Proponents say that ocean energy is preferable to wind because tides are constant and predictable and that water’s natural density requires fewer turbines than are needed to produce the same amount of wind power. Given the difficulty and cost of building tidal arrays at sea and getting the energy back to land, however, ocean technologies are still young and mostly experimental. But as the industry matures, costs will drop and some analysts think the ocean could power nearly two percent of U.S. energy needs.
Tidal energy pioneers are also hard at work on the U.S. Atlantic coast. The New Hampshire Tidal Energy Company is developing tidal power in the Piscataqua River between New Hampshire and Maine.
