The American Recovery and Reinvestment Act of 2009 included more than $70 billion in direct spending and tax credits for clean energy and associated transportation programs. This policy-stimulus combination represents the largest federal commitment in United States history for renewable energy, advanced transportation, and https://www.youtube.com/edit?o=U&video_id=tgE8ZfZwWyM conservation initiatives. These new initiatives were expected to encourage many more utilities to strengthen their clean energy programs. While the Department of Energy has come under criticism for providing loan guarantees to Solyndra, its SunShot initiative has funded successful companies such as EnergySage and Zep Solar.
Among sources of renewable energy, hydroelectric plants have the advantages of being long-lived—many existing plants have operated for more than 100 years. Also, hydroelectric plants are clean and have few emissions. Criticisms directed at large-scale hydroelectric plants include: dislocation of people living where the reservoirs are planned, and release of significant amounts of carbon dioxide during construction and flooding of the reservoir.
Bioethanol is an alcohol made by fermentation, mostly from carbohydrates produced in sugar or starch crops such as corn, sugarcane, or sweet sorghum. Cellulosic biomass, derived from non-food sources such as trees and grasses is also being developed as a feedstock for ethanol production. Ethanol can be used as a fuel for vehicles in its pure form, but it is usually used as a gasoline additive to increase octane and improve vehicle emissions. Bioethanol is widely used in the USA and in Brazil. Biodiesel can be used as a fuel for vehicles in its pure form, but it is usually used as a diesel additive to reduce levels of particulates, carbon monoxide, and hydrocarbons from diesel-powered vehicles. Biodiesel is produced from oils or fats using transesterification and is the most common biofuel in Europe.
Pumped-storage hydroelectricity stores energy in the form of water pumped when energy is available from a lower elevation reservoir to a higher elevation one. The energy is recovered when demand is high by releasing the water, with the pump becoming a hydroelectric power generator.
Other renewable energy technologies are still under development, and include cellulosic ethanol, hot-dry-rock geothermal power, and marine energy. These technologies are not yet widely demonstrated or have limited commercialization. Many are on the horizon and may have potential comparable to other renewable energy technologies, but still depend on attracting sufficient attention and research, development and demonstration (RD&D) funding.
There has been much attention and investment in the oil and gas industry in the area of carbon capture and sequestration, but we hear much less about creating value from recovered off-gas – quite simply, money and CO2 that is disappearing into flares from petrochemical plants and refineries throughout the Middle East.
Another solar generating technology uses photovoltaic cells (PV) to convert sunlight directly into electricity. These are more commonly called ‘solar panels.’ PV cells are made of semiconductors, such as crystalline silicon or various thin-film materials. Photovoltaics can provide tiny amounts of power for watches, large amounts for the electric grid, and everything in between.
Green Energy is energy that can be extracted, generated, and/or consumed without any significant negative impact to the environment. The planet has a natural capability to recover which means pollution that does not go beyond that capability can still be termed green.
^ Jinqing Peng, Lin Lu, Hongxing Yang, Review on lifecycle assessment of energy payback and greenhouse gas emission of solar photovoltaic systems. In: Renewable and Sustainable Energy Reviews 19, (2013), 255–274, Fig. 5, doi:10.1016/j.rser.2012.11.035.
Depending on construction, photovoltaic modules can produce electricity from a range of frequencies of light, but usually cannot cover the entire solar range (specifically, ultraviolet, infrared and low or diffused light). Hence, much of the incident sunlight energy is wasted by solar modules, and they can give far higher efficiencies if illuminated with monochromatic light. Therefore, another design concept is to split the light into different wavelength ranges and direct the beams onto different cells tuned to those ranges. This has been projected to be capable of raising efficiency by 50%.
Renewable energy resources exist over wide geographical areas, in contrast to other energy sources, which are concentrated in a limited number of countries. Rapid deployment of renewable energy and energy efficiency is resulting in significant energy security, climate change mitigation, and economic benefits. The results of a recent review of the literature concluded that as greenhouse gas (GHG) emitters begin to be held liable for damages resulting from GHG emissions resulting in climate change, a high value for liability mitigation would provide powerful incentives for deployment of renewable energy technologies. In international public opinion surveys there is strong support for promoting renewable sources such as solar power and wind power. At the national level, at least 30 nations around the world already have renewable energy contributing more than 20 percent of energy supply. National renewable energy markets are projected to continue to grow strongly in the coming decade and beyond. Some places and at least two countries, Iceland and Norway generate all their electricity using renewable energy already, and many other countries have the set a goal to reach 100% renewable energy in the future. For example, in Denmark the government decided to switch the total energy supply (electricity, mobility and heating/cooling) to 100% renewable energy by 2050.
^ M.R. Schmer, K.P. Vogel, R.B. Mitchell, R.K. Perrin; Vogel; Mitchell; Perrin (2008). “Net energy of cellulosic ethanol from switchgrass”. Proceedings of the National Academy of Sciences of the United States of America. 105 (2): 464–469. Bibcode:2008PNAS..105..464S. doi:10.1073/pnas.0704767105. PMC 2206559 . PMID 18180449.
Linear Fresnel reflector (LFR) systems are similar to parabolic trough systems in that mirrors (reflectors) concentrate sunlight onto a receiver located above the mirrors. These reflectors use the Fresnel lens effect, which allows for a concentrating mirror with a large aperture and short focal length. These systems are capable of concentrating the sun’s energy to approximately 30 times its normal intensity. The only operating linear Fresnel reflector system in the United States is a compact linear Fresnel reflector (CLFR)—also referred to as a concentrating linear Fresnel reflector—a type of LFR technology that has multiple absorbers within the vicinity of the mirrors. Multiple receivers allow the mirrors to change their inclination to minimize how much they block adjacent reflectors’ access to sunlight. This positioning improves system efficiency and reduces material requirements and costs.
Not all renewable energy resources come from the sun. Geothermal energy taps the Earth’s internal heat for a variety of uses, including electric power production, and the heating and cooling of buildings. And the energy of the ocean’s tides come from the gravitational pull of the moon and the sun upon the Earth.
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Jan. 15, 2018 — Researchers have made significant efficiency improvements to the technology used to generate solar fuels. This involves the direct conversion of energy from sunlight into a usable fuel (in this case, … read more
Deciduous trees and plants have been promoted as a means of controlling solar heating and cooling. When planted on the southern side of a building in the northern hemisphere or the northern side in the southern hemisphere, their leaves provide shade during the summer, while the bare limbs allow light to pass during the winter. Since bare, leafless trees shade 1/3 to 1/2 of incident solar radiation, there is a balance between the benefits of summer shading and the corresponding loss of winter heating. In climates with significant heating loads, deciduous trees should not be planted on the Equator-facing side of a building because they will interfere with winter solar availability. They can, however, be used on the east and west sides to provide a degree of summer shading without appreciably affecting winter solar gain.