Simply said, renewable energy comes from natural cycles and systems, turning the ever-present energy around us into usable forms.
Renewable or “alternative” energy is generally cleaner than energy from nonrenewable sources such as petroleum, natural gas, and coal. Yet right now in the U.S. over 80% of our energy still comes from nonrenewable sources.
Like the name says, renewable energy can be replenished constantly. Its sources include radiant energy like solar, thermal energy like geothermal, chemical processes like biomass, gravitational energy like hydropower, and motion energy like wind.
Some of the major current sources of renewable energy include:
Wind power is one of the cleanest technologies, and also one of the most abundant and cost-competitive energy resources, making it a viable alternative to the fossil fuels that harm our health and threaten the environment. Yet wind power is unreliable as a constant source of electricity, impacts vast tracts of land, and is unavailable where wind is intermittent.
Solar power has the ability to one day solve much of the world’s energy needs, but that day is still very far off. Still, solar technologies are getting more efficient and cost-effective each year, and it is the fastest-growing type of renewable energy.
Ethanol is the product of crops high in sugar or starch, while biodiesel is the product of plants with a high oil content. Both are biofuels, and both provide viable energy sources that have not yet reached their full potential. Scientists continue refining foodstocks to obtain higher efficiencies.
Heat from the earth, or geothermal energy, is cost effective, reliable, and clean, but is mostly confined to areas near tectonic plate boundaries. Some progress has been made recently in expanding the range of geothermal resources, but geothermal power remains a limited solution to our energy needs.
Harnassing the kinetic power of moving water to generate electricity is the largest source of renewable power in the United States and worldwide. Hydropower can be a sustainable and nonpolluting power source that can help decrease our dependence on fossil fuels and reduce the threat of global warming, but is limited to areas with large and consistent water supplies.
Another form of kinetic power generation, the ocean’s constant movement by way of waves, tides, and currents is a powerful and clean energy resource. Like other hydro power, though, its geographic range is limited.
Climate Change and Renewable Energy
There is general agreement among the world’s major economies that it is essential to reduce carbon emissions by 50% by 2050. And with energy-related CO2 accounting for 61% of global greenhouse gas emissions today, the energy sector will have to be at the heart of change.
The European Union is committed to a 30% reduction by 2020 and a 60-80% reduction by 2050, under condition that other industrialized nations also commit. To do so will require $22 trillion in global energy investments over the next 25-30 years. Much of that investment will be in new power plants and distribution systems.