Q.4
Name some sources of clean renewable energy.
Answers
The sun is our most powerful source of energy. Sunlight, or solar energy, can be used for heating, lighting and cooling homes and other buildings, generating electricity, water heating, and a variety of industrial processes. The technology used to harvest the sun's energy is constantly evolving, including water-heating rooftop pipes, photo-voltaic cells, and mirror arrays. Rooftop panels are not intrusive, but large arrays on the ground can compete with wildlife habitat.
Wind is the movement of air that occurs when warm air rises and cooler air rushes in to replace it. The energy of the wind has been used for centuries to sail ships and drive windmills that grind grain. Today, wind energy is captured by wind turbines and used to generate electricity. Issues periodically arise about where turbines are installed, as they can be problematic for migrating birds and bats.
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. Tiny turbines can even be used to power single homes.
While it is renewable, large-scale hydroelectricity can have a large ecological footprint.
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 has tremendous potential as a fuel and energy source. Hydrogen is the most common element on Earth—for example, water is two-thirds hydrogen—but in nature, it is always found in combination with other elements. Once separated from other elements, hydrogen can be used to power vehicles, replace natural gas for heating and cooking, and generate electricity. In 2015, the first production passenger car powered by hydrogen became available in Japan and the United States.
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. This application is increasingly used to offset heating and cooling costs in residential and commercial buildings.
The ocean provides several forms of renewable energy, and each one is driven by different forces. Energy from ocean waves and tides can be harnessed to generate electricity, and ocean thermal energy—from the heat stored in seawater—can also be converted to electricity. Using current technologies, most ocean energy is not cost-effective compared to other renewable energy sources, but the ocean remains an important potential energy source for the future.
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