Hydroelectric dams represent a significant portion of total overall world renewable energy production and can easily be installed in remote rural areas. Dams, both large and smaller scale, produce little direct waste, and require little maintenance. Ocean waves, currents and tides represent dynamic, abundant sources of renewable energy that remain completely environmentally friendly. However, these ocean sources remain geographically dependent, as the energy can only be developed along coastlines.
Wind power is the conversion of energy by wind turbines into a useful form, i.e. mechanical energy, and electricity. Large scale wind farms are much more common than units for individual homes. Residential units are increasing in production, however, and are capable of powering large appliances to entire houses, depending on the size of the turbine. Wind farms installed on agricultural land or grazing area, or offshore, have some of the lowest environmental impacts of all large scale renewable energy sources.
Biomass includes biodegradable wastes that can be used as fuel (biofuel), or that can produce energy for a municipality in a biomass power plant. Industrial, cellulosic and non-cellulosic, biomass/ biofuel (biodiesel and ethanol) can be derived from numerous types of organic plants in addition to waste, including algae, switchgrass, palm, sorghum, corn, soybean and sugarcane. Algae are among the fastest growing plants in the world, and as much as 60 percent of their weight is oil. Algae are a very promising renewable energy source. Wood and wood by-products (such as wood chips) are also viable sources for biomass. Many varieties of tree species can be used for cellulosic biofuel production, such as those mentioned above, and others.
Photovoltaic (PV) solar power entails harnessing the sun’s energy to produce electricity through PV cells. One of the fastest growing energy sources, new technologies are developing at a rapid pace, bringing solar closer to cost parity with fossil fuels as a viable energy source to power the grid. Solar cells are becoming more efficient, thinner, smaller, transportable, flexible, and even spray-on (like paint), allowing for easy installation. PV has been used to power small and medium sized applications, from the calculator powered by a single solar cell to off-grid homes powered by a photovoltaic array. Large-scale, or mega, solar parks are growing in deployment worldwide. Concentrated Solar Power (CSP), solar towers, dishes and troughs, are growing sources of renewable energy.
Solar thermal, including CSP, uses technology to harness the sun’s energy, but then uses that energy to heat a working fluid, which is ultimately the energy source. As opposed to PV, solar thermal uses solar energy indirectly, to heat water, oil, molten salt, or another fluid. One benefit of solar thermal is that a few forms of energy storage become available when this form of renewable energy is employed.
Geothermal power also has small and large scale designs. Geothermal heat pumps, on the small end of the spectrum, are much less common than industrial plants. Geothermal plants are located near natural energy sources: tectonic plate boundaries, volcanoes, hot springs and geysers. Geothermal energy is primarily power generated from natural steam, hot water, hot rocks, or lava in the earth’s crust. The majority of geothermal power is produced by conveying heated water or steam back to the surface so that its heat can be extracted through a heat exchanger, or its pressure can be used to drive turbines.
Of course, there are a couple of other renewable energy sources. Other types of renewable energy include hydrogen and hydrogen fuel cells, most notably. Hydrogen can eventually be used to help meet the world’s energy needs. In Iceland, and some other European countries, hydrogen fuel cells are being used efficiently. More R&D is needed for the rest of Europe, the USA and Australia to use hydrogen/ hydrogen fuel cells efficiently and effectively as a major energy source. However, places like Iceland prove that it is a viable option.