According to the Energy Information Administration, “renewable energy refers to resources that are replenished in a relatively short period of time.” Renewable energy sources include hydropower, wood biomass (used to generate heat and electricity), alternative biomass fuels (such as ethanol and biodiesel), waste, geothermal, wind, and solar.
The use of renewable fuels dates to Neolithic times, when cave dwellers made fire from wood and other biomass for cooking and heating. For thousands of years thereafter, renewable energy was all humans used. The small amounts of energy accessible to humans through traditional dispersed renewable energy sources meant that for millennia, human lives remained unchanged.
Today, many are seeking to to use technology made possible by modern, concentrated energy forms to capture and harness dispersed renewable energy potential into concentrated forms. Renewable energy plays a major role in the economies of the developing world.
Renewable energy relies upon the natural forces at work upon the earth, including the internal heat represented by geothermal, the pull of lunar gravity as it affects the potential for tidal power, and solar radiation such as that stored through photosynthesis in biomass.
Renewable Energy in the US
About 7 percent of all energy consumed in the US in 2007 was from renewable sources, and they account for about 9 percent of the nation’s total electricity production.
While a relatively small fraction of our overall energy supply in 2004, the US is the world’s largest consumer of renewable energy from geothermal, solar, wood, wind, and waste using some 28% of the world’s total. In 2007, the distribution of U.S. renewable consumption by source was:
- Hydropower 36%
- Biomass Wood 32%
- Biomass Waste 6%
- Biomass Biofuels 16%
- Wind 5%
- Other 6%
While hydropower is by far the biggest source of renewable energy in the US, solar power - particularly photovoltaic cell conversion to electricity - is far and away the smallest, accounting for slightly more than one 100th of one percent of the net electricity produced in the US in 2007.
Globally, the use of hydroelectricity and other grid-connected renewable energy sources is expected to grow only minimally over the next couple of decades, increasing at a rate of 2.1 percent per year until 2030, according to the EIA. Most of that growth will come from the construction of new hydropower facilities in Asia and Central and South America. The renewable share of total world energy consumption is expected to rise from 7.7 percent in 2005 to 8.5 percent in 2030.
Renewable Obstacles
One of the most significant obstacles to making most renewable energy sources competitive with more widely adopted energy sources is that they are relatively dilute. In fact, some of today’s more promising processes for tapping biomass energy involve using chemical or thermal conversion in an attempt to mimic the results of a process that, through immense pressure and over geologic time scales, created energy-rich fossil fuels from biomass. Despite such developing technologies, the amount of energy in a given amount of raw biomass tends to be significantly less than that contained in an equal amount of its concentrated cousin, fossil energy.
In the US, demand for all sources of energy is expected to rise between now and 2030 to keep pace with growth in the economy, population and standard of living. Renewable sources are anticipated to participate more broadly in this growth being spurred by State and Federal legislation, including the Energy Independence and Security Act of 2007.
In 2006, hydropower accounted for 2.89 quadrillion Btu of energy, a figure the EIA projects to rise to 3.0 quadrillion Btu by 2030. All other sources of renewable fuels accounted for 3.93 quadrillion Btu in 2006 and are anticipated to increase to 10.84 quadrillion Btu by 2030. According to EIA’s 2008 forecast, the increase is due to the Federal Renewable Fuel Standard, mandating the use of ethanol in transportation fuels, and state Renewable Portfolio Standards, mandating the use of renewable generating technologies in the electric sector of 25 states and the District of Columbia.
Of the slightly over 118 quadrillion Btu the U.S. is expected to consume in 2030, renewable sources are projected to account for 13.84 quadrillion Btu, or 11.7 percent.
