Alternative energy is any energy source that is an alternative to fossil fuel. These alternatives are intended to address concerns about fossil fuels, such as its high carbon dioxide emissions, an important factor in global warming. Marine energy, hydroelectric, wind, geothermal and solar power are all alternative sources of energy.
The nature of what constitutes an alternative energy source has changed considerably over time, as have controversies regarding energy use. Because of the variety of energy choices and differing goals of their advocates, defining some energy types as "alternative" is considered very controversial.
- 1 Definitions
- 2 History
- 3 Existing types of alternative energy
- 4 Enabling technologies
- 5 Renewable energy vs non-renewable energy
- 6 Relatively new concepts for alternative energy
- 7 Investing in alternative energy
- 8 Making alternative energy mainstream
- 9 Research
- 10 Disadvantages
- 11 Setbacks
- 12 See also
- 13 References
- 14 Further reading
|Oxford Dictionary||Energy fueled into ways that do not use up natural resources or harm the environment.|
|Princeton WordNet||Energy derived from sources that do not use up natural resources or harm the environment.|
|Responding to Climate Change 2007||Energy derived from nontraditional sources (e.g., compressed natural gas, solar, hydroelectric, wind).|
|Natural Resources Defense Council||Energy that is not popularly used and is usually environmentally sound, such as solar or wind energy (as opposed to fossil fuels).|
|Materials Management||Fuel sources that are other than those derived from fossil fuels. Typically used interchangeably for renewable energy. Examples include: wind, solar, biomass, wave and tidal energy.|
|Torridge District Council||Energy generated from alternatives to fossil fuels. Need not be renewable.|
Historians of economies have examined the key transitions to alternative energies and regard the transitions as pivotal in bringing about significant economic change. Prior to the shift to an alternative energy, supplies of the dominant energy type became erratic, accompanied by rapid increases in energy prices.
Coal as an alternative to wood
In the late medieval period, coal was the new alternative fuel to save the society from overuse of the dominant fuel, wood. The deforestation had resulted in shortage of wood, at that time soft coal appeared as a savior. Historian Norman F. Cantor describes how:
Europeans had lived in the midst of vast forests throughout the earlier medieval centuries. After 1250 they became so skilled at deforestation that by 1500 AD they were running short of wood for heating and cooking... By 1500 Europe was on the edge of a fuel and nutritional disaster, [from] which it was saved in the sixteenth century only by the burning of soft coal and the cultivation of potatoes and maize.
Petroleum as an alternative to whale oil
Whale oil was the dominant form of lubrication and fuel for lamps in the early 19th century, but the depletion of the whale stocks by mid century caused whale oil prices to skyrocket setting the stage for the adoption of petroleum which was first commercialized in Pennsylvania in 1859.
Ethanol as an alternative to fossil fuels
In 1917, Alexander Graham Bell advocated ethanol from corn, wheat and other foods as an alternative to coal and oil, stating that the world was in measurable distance of depleting these fuels. For Bell, the problem requiring an alternative was lack of renewability of orthodox energy sources. Since the 1970s, Brazil has had an ethanol fuel program which has allowed the country to become the world's second largest producer of ethanol (after the United States) and the world's largest exporter. Brazil's ethanol fuel program uses modern equipment and cheap sugar cane as feedstock, and the residual cane-waste (bagasse) is used to process heat and power. There are no longer light vehicles in Brazil running on pure gasoline. By the end of 2008 there were 35,000 filling stations throughout Brazil with at least one ethanol pump.
Cellulosic ethanol can be produced from a diverse array of feedstocks, and involves the use of the whole crop. This new approach should increase yields and reduce the carbon footprint because the amount of energy-intensive fertilizers and fungicides will remain the same, for a higher output of usable material. As of 2008, there are nine commercial cellulosic ethanol plants which are either operating, or under construction, in the United States.
Second-generation biofuels technologies are able to manufacture biofuels from inedible biomass and could hence prevent conversion of food into fuel." As of July 2010, there is one commercial second-generation (2G) ethanol plant Inbicon Biomass Refinery, which is operating in Denmark.
Coal gasification as an alternative to petroleum
In the 1970s, President Jimmy Carter's administration advocated coal gasification as an alternative to expensive imported oil. The program, including the Synthetic Fuels Corporation was scrapped when petroleum prices plummeted in the 1980s. The carbon footprint and environmental impact of coal gasification are both very high.
Existing types of alternative energy
- Hydro electricity captures energy from falling water.
- Nuclear energy uses nuclear fission to release energy stored in the atomic bonds of heavy elements.
- Wind energy is the generation of electricity from wind, commonly by using propeller-like turbines.
- Solar energy is the use of sunlight. Light can be changed into thermal (heat) energy or directly into electricity via photovoltaic devices.
- Geothermal energy is the use of the earth's internal heat to boil water for heating buildings or generating electricity.
- Biofuel and ethanol are plant-derived gasoline substitutes for powering vehicles.
- Hydrogen can be used as a carrier of energy, produced by various technologies such as cracking of hydrocarbons or water electrolysis.
Ice storage air conditioning and thermal storage heaters are methods of shifting consumption to use low cost off-peak electricity. When compared to resistance heating, heat pumps conserve electrical power (or in rare cases mechanical or thermal power) by collecting heat from a cool source such as a body of water, the ground or the air.
Thermal storage technologies allow heat or cold to be stored for periods of time ranging from diurnal to interseasonal, and can involve storage of sensible energy (i.e. by changing the temperature of a medium) or latent energy (e.g. through phase changes of a medium (i.e. changes from solid to liquid or vice versa), such as between water and slush or ice). Energy sources can be natural (via solar-thermal collectors, or dry cooling towers used to collect winter's cold), waste energy (such as from HVAC equipment, industrial processes or power plants), or surplus energy (such as seasonally from hydropower projects or intermittently from wind farms). The Drake Landing Solar Community (Alberta, Canada) is illustrative. Borehole thermal energy storage allows the community to get 97% of its year-round heat from solar collectors on the garage roofs. The storages can be insulated tanks, borehole clusters in substrates ranging from gravel to bedrock, deep aquifers, or shallow pits that are lined and insulated. Some applications require inclusion of a heat pump.
Renewable energy vs non-renewable energy
Renewable energy is generated from natural resources—such as sunlight, wind, rain, tides and geothermal heat—which are renewable (naturally replenished). When comparing the processes for producing energy, there remain several fundamental differences between renewable energy and fossil fuels. The process of producing oil, coal, or natural gas fuel is a difficult and demanding process that requires a great deal of complex equipment, physical and chemical processes. On the other hand, alternative energy can be widely produced with basic equipment and natural processes. Wood, the most renewable and available alternative fuel, emits the same amount of carbon when burned as would be emitted if it degraded naturally. Nuclear power is an alternative to fossil fuels that is non-renewable, like fossil fuels, nuclear ones are a finite resource.
Ecologically friendly alternatives
A renewable energy source such as biomass is sometimes regarded as a good alternative to providing heat and electricity with fossil fuels. Biofuels are not inherently ecologically friendly for this purpose, while burning biomass is carbon-neutral, air pollution is still produced. For example, the Netherlands, once leader in use of palm oil as a biofuel, has suspended all subsidies for palm oil due to the scientific evidence that their use "may sometimes create more environmental harm than fossil fuels". The Netherlands government and environmental groups are trying to trace the origins of imported palm oil, to certify which operations produce the oil in a responsible manner. Regarding biofuels from foodstuffs, the realization that converting the entire grain harvest of the US would only produce 16% of its auto fuel needs, and the decimation of Brazil's CO2 absorbing tropical rain forests to make way for biofuel production has made it clear that placing energy markets in competition with food markets results in higher food prices and insignificant or negative impact on energy issues such as global warming or dependence on foreign energy. Recently, alternatives to such undesirable sustainable fuels are being sought, such as commercially viable sources of cellulosic ethanol.
Relatively new concepts for alternative energy
Carbon-neutral and negative fuels
Carbon-neutral fuels are synthetic fuels (including methane, gasoline, diesel fuel, jet fuel or ammonia) produced by hydrogenating waste carbon dioxide recycled from power plant flue-gas emissions, recovered from automotive exhaust gas, or derived from carbonic acid in seawater. Commercial fuel synthesis companies suggest they can produce synthetic fuels for less than petroleum fuels when oil costs more than $55 per barrel. Renewable methanol (RM) is a fuel produced from hydrogen and carbon dioxide by catalytic hydrogenation where the hydrogen has been obtained from water electrolysis. It can be blended into transportation fuel or processed as a chemical feedstock.
The George Olah carbon dioxide recycling plant operated by Carbon Recycling International in Grindavík, Iceland has been producing 2 million liters of methanol transportation fuel per year from flue exhaust of the Svartsengi Power Station since 2011. It has the capacity to produce 5 million liters per year. A 250 kilowatt methane synthesis plant was constructed by the Center for Solar Energy and Hydrogen Research (ZSW) at Baden-Württemberg and the Fraunhofer Society in Germany and began operating in 2010. It is being upgraded to 10 megawatts, scheduled for completion in autumn, 2012. Audi has constructed a carbon-neutral liquefied natural gas (LNG) plant in Werlte, Germany. The plant is intended to produce transportation fuel to offset LNG used in their A3 Sportback g-tron automobiles, and can keep 2,800 metric tons of CO2 out of the environment per year at its initial capacity. Other commercial developments are taking place in Columbia, South Carolina, Camarillo, California, and Darlington, England.
|Part of a series about|
Such fuels are considered carbon-neutral because they do not result in a net increase in atmospheric greenhouse gases. To the extent that synthetic fuels displace fossil fuels, or if they are produced from waste carbon or seawater carbonic acid, and their combustion is subject to carbon capture at the flue or exhaust pipe, they result in negative carbon dioxide emission and net carbon dioxide removal from the atmosphere, and thus constitute a form of greenhouse gas remediation.
Such renewable fuels alleviate the costs and dependency issues of imported fossil fuels without requiring either electrification of the vehicle fleet or conversion to hydrogen or other fuels, enabling continued compatible and affordable vehicles. Carbon-neutral fuels offer relatively low cost energy storage, alleviating the problems of wind and solar intermittency, and they enable distribution of wind, water, and solar power through existing natural gas pipelines.
Nighttime wind power is considered the most economical form of electrical power with which to synthesize fuel, because the load curve for electricity peaks sharply during the day, but wind tends to blow slightly more at night than during the day, so, the price of nighttime wind power is often much less expensive than any alternative. Germany has built a 250 kilowatt synthetic methane plant which they are scaling up to 10 megawatts.
Algae fuel is a biofuel which is derived from algae. During photosynthesis, algae and other photosynthetic organisms capture carbon dioxide and sunlight and convert it into oxygen and biomass. This is usually done by placing the algae between two panes of glass. The algae creates three forms of energy fuel: heat (from its growth cycle), biofuel (the natural "oil" derived from the algae), and biomass (from the algae itself, as it is harvested upon maturity).
The heat can be used to power building systems (such as heat process water) or to produce energy. Biofuel is oil extracted from the algae upon maturity, and used to create energy similar to the use of biodiesel. The biomass is the matter left over after extracting the oil and water, and can be harvested to produce combustible methane for energy production, similar to the warmth felt in a compost pile or the methane collected from biodegradable materials in a landfill. Additionally, the benefits of algae biofuel are that it can be produced industrially, as well as vertically (i.e. as a building facade), thereby obviating the use of arable land and food crops (such as soy, palm, and canola).
Biomass briquettes are being developed in the developing world as an alternative to charcoal. The technique involves the conversion of almost any plant matter into compressed briquettes that typically have about 70% the calorific value of charcoal. There are relatively few examples of large scale briquette production. One exception is in North Kivu, in eastern Democratic Republic of Congo, where forest clearance for charcoal production is considered to be the biggest threat to Mountain Gorilla habitat. The staff of Virunga National Park have successfully trained and equipped over 3500 people to produce biomass briquettes, thereby replacing charcoal produced illegally inside the national park, and creating significant employment for people living in extreme poverty in conflict affected areas. 
Biogas digestion deals with harnessing the methane gas that is released when waste breaks down. This gas can be retrieved from garbage or sewage systems. Biogas digesters are used to process methane gas by having bacteria break down biomass in an anaerobic environment.  The methane gas that is collected and refined can be used as an energy source for various products.
Biological hydrogen production
2H2 + O2 → 2H2O + High Energy
High Energy + 2H2O → 2H2 + O2
This requires a high-energy input, making commercial hydrogen very inefficient. Use of a biological vector as a means to split water, and therefore produce hydrogen gas, would allow for the only energy input to be solar radiation. Biological vectors can include bacteria or more commonly algae. This process is known as biological hydrogen production. It requires the use of single celled organisms to create hydrogen gas through fermentation. Without the presence of oxygen, also known as an anaerobic environment, regular cellular respiration cannot take place and a process known as fermentation takes over. A major by-product of this process is hydrogen gas. If this could be implemented on a large scale, then sunlight, nutrients and water could create hydrogen gas to be used as a dense source of energy. Large-scale production has proven difficult. Not until 1999, was it even possible to induce these anaerobic conditions by sulfur deprivation. Since the fermentation process is an evolutionary back up, turned on during stress, the cells would die after a few days. In 2000, a two-stage process was developed to take the cells in and out of anaerobic conditions and therefore keep them alive. For the last ten years, finding a way to do this on a large-scale has been the main goal of research. Careful work is being done to ensure an efficient process before large-scale production, however once a mechanism is developed, this type of production could solve our energy needs.
Hydroelectricity provided 75% of the worlds renewable electricity in 2013. Much of the electricity used today is a result of the heyday of conventional hydroelectric development between 1960 and 1980, which has virtually ceased in Europe and North America due to environmental concerns. Globally there is a trend towards more hydroelectricity. From 2004 to 2014 the installed capacity rose from 715 to 1,055 GW. A popular alternative to the large dams of the past is run-of-the-river where there is no water stored behind a dam and generation usually varies with seasonal rainfall. Using run-of-the-river in wet seasons and solar in dry seasons can balance seasonal variations for both. Another move away from large dams is small hydro, these tend to be situated high up on tributaries, rather than on main rivers in valley bottoms.
Offshore wind farms are similar to land-based wind farms, but are located on the ocean. Offshore wind farms can be placed in water up to 40 metres (130 ft) deep, whereas floating wind turbines can float in water up to 700 metres (2,300 ft) deep. The advantage of having a floating wind farm is to be able to harness the winds from the open ocean. Without any obstructions such as hills, trees and buildings, winds from the open ocean can reach up to speeds twice as fast as coastal areas.
Significant generation of offshore wind energy already contributes to electricity needs in Europe and Asia and now the first offshore wind farms are under development in U.S. waters. While the offshore wind industry has grown dramatically over the last several decades, especially in Europe, there is still uncertainty associated with how the construction and operation of these wind farms affect marine animals and the marine environment.
Traditional offshore wind turbines are attached to the seabed in shallower waters within the nearshore marine environment. As offshore wind technologies become more advanced, floating structures have begun to be used in deeper waters where more wind resources exist.
Marine and hydrokinetic energy
Marine and Hydrokinetic (MHK) or marine energy development includes projects using the following devices:
- Wave power is the transport of energy by wind waves, and the capture of that energy to do useful work – for example, electricity generation or pumping water into reservoirs. A machine able to exploit significant waves in open coastal areas is generally known as a wave energy converter.
- Tidal power turbines are placed in coastal and estuarine areas and daily flows are quite predictable.
- In-stream turbines in fast-moving rivers
- Ocean current turbines in areas of strong marine currents
- Ocean thermal energy converters in deep tropical waters.
In the year 2015 ten new reactors came online and 67 more were under construction including the first eight new Generation III+ AP1000 reactors in the US and China and the first four new Generation III EPR reactors in Finland, France and China. Reactors are also under construction in Belarus, Brazil, India, Iran, Japan, Pakistan, Russia, Slovakia, South Korea, Turkey, Ukraine and United Arab Emirates.
Thorium nuclear power
Thorium is a fissionable material for possible future use in a thorium-based reactor. Proponents of thorium reactors claims several potential advantages over a uranium fuel cycle, such as thorium's greater abundance, better resistance to nuclear weapons proliferation, and reduced plutonium and actinide production. Thorium reactors can be modified to produce Uranium-233, which can then be processed into highly enriched uranium, which has been tested in low yield weapons, and is unproven on a commercial scale.
Investing in alternative energy
As an emerging economic sector, there are limited stock market investment opportunities in alternative energy available to the general public. The public can buy shares of alternative energy companies from various stock markets, with wildly volatile returns. The recent IPO of SolarCity demonstrates the nascent nature of this sector- within a few weeks, it already had achieved the second highest market cap within the alternative energy sector.
Investors can also choose to invest in ETFs (exchange-traded funds) that track an alternative energy index, such as the WilderHill New Energy Index. Additionally, there are a number of mutual funds, such as Calvert's Global Alternative Energy Mutual Fund that are a bit more proactive in choosing the selected investments.
Recently, Mosaic Inc. launched an online platform allowing residents of California and New York to invest directly in solar. Investing in solar projects had previously been limited to accredited investors, or a small number of willing banks.
Over the last three years publicly traded alternative energy companies have been very volatile, with some 2007 returns in excess of 100%, some 2008 returns down 90% or more, and peak-to-trough returns in 2009 again over 100%. In general there are three sub-segments of "alternative" energy investment: solar energy, wind energy and hybrid electric vehicles. Alternative energy sources which are renewable and have lower carbon emissions than fossil fuels are hydropower, wind energy, solar energy, geothermal energy, and bio fuels. Each of these four segments involve very different technologies and investment concerns.
For example, photovoltaic solar energy is based on semiconductor processing and accordingly, benefits from steep cost reductions similar to those realized in the microprocessor industry (i.e., driven by larger scale, higher module efficiency, and improving processing technologies). PV solar energy is perhaps the only energy technology whose electricity generation cost could be reduced by half or more over the next five years. Better and more efficient manufacturing process and new technology such as advanced thin film solar cell is a good example of that helps to reduce industry cost.
The economics of solar PV electricity are highly dependent on silicon pricing and even companies whose technologies are based on other materials (e.g., First Solar) are impacted by the balance of supply and demand in the silicon market. In addition, because some companies sell completed solar cells on the open market (e.g., Q-Cells), this creates a low barrier to entry for companies that want to manufacture solar modules, which in turn can create an irrational pricing environment.
In contrast, because wind power has been harnessed for over 100 years, its underlying technology is relatively stable. Its economics are largely determined by siting (e.g., how hard the wind blows and the grid investment requirements) and the prices of steel (the largest component of a wind turbine) and select composites (used for the blades). Because current wind turbines are often in excess of 100 meters high, logistics and a global manufacturing platform are major sources of competitive advantage. These issues and others were explored in a research report by Sanford Bernstein.
Alternative energy in transportation
Due to steadily rising gas prices in 2008 with the US national average price per gallon of regular unleaded gas rising above $4.00 at one point, there has been a steady movement towards developing higher fuel efficiency and more alternative fuel vehicles for consumers. In response, many smaller companies have rapidly increased research and development into radically different ways of powering consumer vehicles. Hybrid and battery electric vehicles are commercially available and are gaining wider industry and consumer acceptance worldwide.
For example, Nissan USA introduced the world's first mass-production electric vehicle, the Nissan Leaf. A plug-in hybrid car, the Chevrolet Volt also has been produced, using an electric motor to drive the wheels, and a small four-cylinder engine to generate additional electricity.
Making alternative energy mainstream
Before alternative energy becomes mainstream there are a few crucial obstacles that it must overcome. First there must be increased understanding of how alternative energies are beneficial; secondly the availability components for these systems must increase; and lastly the pay-back period must be decreased.
For example, electric vehicles (EV) and plug-in hybrid electric vehicles (PHEV) are on the rise. These vehicles depend on investment in home and public charging infrastructure, as well as implementing much more alternative energy for future transportation.
There are numerous organizations within the academic, federal, and commercial sectors conducting large scale advanced research in the field of alternative energy. This research spans several areas of focus across the alternative energy spectrum. Most of the research is targeted at improving efficiency and increasing overall energy yields.
In the US, multiple federally supported research organizations have focused on alternative energy in recent years. Two of the most prominent of these labs are Sandia National Laboratories and the National Renewable Energy Laboratory (NREL), both of which are funded by the United States Department of Energy and supported by various corporate partners. Sandia has a total budget of $2.4 billion while NREL has a budget of $375 million.
With the increasing consumption levels of energy, it is projected that the levels would increase by 21% in 2030. The cost of the renewables was relatively cheaper at $2.5m/MW as compared to the non-renewables & 2.7m/MW. Evidently, the use of renewable energy is a cost effective method of obtaining energy. Additionally, their use also dispenses with the trade-off that has existed between environmental conservation and economic growth.
Mechanical energy associated with human activities such as blood circulation, respiration, walking, typing and running, is ubiquitous but usually wasted. It has attracted tremendous attention from researchers around the globe to find methods to scavenge such mechanical energies. The best solution currently is to use piezoelectric materials, which can generate flow of electrons when deformed. Various devices using piezoelectric materials have been built to scavenge mechanical energy. Considering that the piezoelectric constant of the material plays a critical role in the overall performance of a piezoelectric device, one critical research direction to improve device efficiency is to find new material of large piezoelectric response. Lead Magnesium Niobate-Lead Titanate (PMN-PT) is a next-generation piezoelectric material with super high piezoelectric constant when ideal composition and orientation are obtained. In 2012, PMN-PT Nanowires with a very high piezoelectric constant were fabricated by a hydro-thermal approach and then assembled into an energy-harvesting device. The record-high piezoelectric constant was further improved by the fabrication of a single-crystal PMN-PT nanobelt, which was then used as the essential building block for a piezoelectric nanogenerator.
Solar heat has long been employed in passively and actively heated buildings, as well as district heating systems. Examples of the latter are the Drake Landing Solar Community is Alberta, Canada, and numerous district systems in Denmark and Germany. In Europe, there are two programs for the application of solar heat: the Solar District Heating (SDH) and the International Energy Agency's Solar Heating and Cooling (SHC) program.
The obstacles preventing the large-scale implementation of solar powered energy generation is the inefficiency of current solar technology and the cost. Currently, photovoltaic (PV) panels only have the ability to convert around 16% of the sunlight that hits them into electricity.
Both Sandia National Laboratories and the National Renewable Energy Laboratory (NREL), have heavily funded solar research programs. The NREL solar program has a budget of around $75 million and develops research projects in the areas of photovoltaic (PV) technology, solar thermal energy, and solar radiation. The budget for Sandia's solar division is unknown, however it accounts for a significant percentage of the laboratory's $2.4 billion budget.
Several academic programs have focused on solar research in recent years. The Solar Energy Research Center (SERC) at University of North Carolina (UNC) has the sole purpose of developing a cost-effective solar technology. In 2008, researchers at Massachusetts Institute of Technology (MIT) developed a method to store solar energy by using it to produce hydrogen fuel from water. Such research is targeted at addressing the obstacle that solar development faces of storing energy for use during nighttime hours when the sun is not shining. The Zhangebei National Wind and Solar Energy Storage and Transmission Demonstration Project northwest of Beijing, uses batteries to store 71 MWh, integrating wind and solar energy on the grid with frequency and voltage regulation.
In February 2012, North Carolina-based Semprius Inc., a solar development company backed by German corporation Siemens, announced that they had developed the world's most efficient solar panel. The company claims that the prototype converts 33.9% of the sunlight that hits it to electricity, more than double the previous high-end conversion rate.
Wind energy research dates back several decades to the 1970s when NASA developed an analytical model to predict wind turbine power generation during high winds. Today, both Sandia National Laboratories and National Renewable Energy Laboratory have programs dedicated to wind research. Sandia's laboratory focuses on the advancement of materials, aerodynamics, and sensors. The NREL wind projects are centered on improving wind plant power production, reducing their capital costs, and making wind energy more cost effective overall.
The Field Laboratory for Optimized Wind Energy (FLOWE) at Caltech was established to research alternative approaches to wind energy farming technology practices that have the potential to reduce the cost, size, and environmental impact of wind energy production.
Renewable energies such as wind, solar, biomass and geothermal combined, supplied 1.3% of global final energy consumption in 2013.
Biomass can be regarded as "biological material" derived from living, or recently living organisms. It most often refers to plants or plant-derived materials which are specifically called lignocellulosic biomass. As an energy source, biomass can either be used directly via combustion to produce heat, or indirectly after converting it to various forms of biofuel. Conversion of biomass to biofuel can be achieved by different methods which are broadly classified into: thermal, chemical, and biochemical methods. Wood remains the largest biomass energy source today; examples include forest residues (such as dead trees, branches and tree stumps), yard clippings, wood chips and even municipal solid waste. In the second sense, biomass includes plant or animal matter that can be converted into fibers or other industrial chemicals, including biofuels. Industrial biomass can be grown from numerous types of plants, including miscanthus, switchgrass, hemp, corn, poplar, willow, sorghum, sugarcane, bamboo, and a variety of tree species, ranging from eucalyptus to oil palm (palm oil).
Biomass, biogas and biofuels are burned to produce heat/power and in doing so harm the environment. Pollutants such as sulphurous oxides (SOx), nitrous oxides (NOx), and particulate matter (PM) are produced from this combustion. The World Health Organisation estimates that 7 million premature deaths are caused each year by air pollution, and biomass combustion is a major contributor of it. The use of biomas is carbon neutral over time, but is otherwise similar to burning fossil fuels.
As the primary source of biofuels in North America, many organizations are conducting research in the area of ethanol production. On the Federal level, the USDA conducts a large amount of research regarding ethanol production in the United States. Much of this research is targeted toward the effect of ethanol production on domestic food markets.
The National Renewable Energy Laboratory has conducted various ethanol research projects, mainly in the area of cellulosic ethanol. Cellulosic ethanol has many benefits over traditional corn based-ethanol. It does not take away or directly conflict with the food supply because it is produced from wood, grasses, or non-edible parts of plants. Moreover, some studies have shown cellulosic ethanol to be more cost effective and economically sustainable than corn-based ethanol. Sandia National Laboratories conducts in-house cellulosic ethanol research and is also a member of the Joint BioEnergy Institute (JBEI), a research institute founded by the United States Department of Energy with the goal of developing cellulosic biofuels.
From 1978 to 1996, the National Renewable Energy Laboratory experimented with using algae as a biofuels source in the "Aquatic Species Program." A self-published article by Michael Briggs, at the University of New Hampshire Biofuels Group, offers estimates for the realistic replacement of all motor vehicle fuel with biofuels by utilizing algae that have a natural oil content greater than 50%, which Briggs suggests can be grown on algae ponds at wastewater treatment plants. This oil-rich algae can then be extracted from the system and processed into biofuels, with the dried remainder further reprocessed to create ethanol.
The production of algae to harvest oil for biofuels has not yet been undertaken on a commercial scale, but feasibility studies have been conducted to arrive at the above yield estimate. In addition to its projected high yield, algaculture— unlike food crop-based biofuels — does not entail a decrease in food production, since it requires neither farmland nor fresh water. Many companies are pursuing algae bio-reactors for various purposes, including scaling up biofuels production to commercial levels.
Several groups in various sectors are conducting research on Jatropha curcas, a poisonous shrub-like tree that produces seeds considered by many to be a viable source of biofuels feedstock oil. Much of this research focuses on improving the overall per acre oil yield of Jatropha through advancements in genetics, soil science, and horticultural practices. SG Biofuels, a San Diego-based Jatropha developer, has used molecular breeding and biotechnology to produce elite hybrid seeds of Jatropha that show significant yield improvements over first generation varieties. The Center for Sustainable Energy Farming (CfSEF) is a Los Angeles-based non-profit research organization dedicated to Jatropha research in the areas of plant science, agronomy, and horticulture. Successful exploration of these disciplines is projected to increase Jatropha farm production yields by 200-300% in the next ten years.
Geothermal energy is produced by tapping into the heat within the earths crust. It is considered sustainable because that thermal energy is constantly replenished. However, the science of geothermal energy generation is still young and developing economic viability. Several entities, such as the National Renewable Energy Laboratory and Sandia National Laboratories are conducting research toward the goal of establishing a proven science around geothermal energy. The International Centre for Geothermal Research (IGC), a German geosciences research organization, is largely focused on geothermal energy development research.
Over $1 billion has been spent on the research and development of hydrogen fuel in the United States. Both the National Renewable Energy Laboratory and Sandia National Laboratories have departments dedicated to hydrogen research. Much of this work centers on hydrogen storage and fuel cell technologies
The generation of alternative energy on the scale needed to replace fossil energy, in an effort to reverse global climate change, is likely to have significant negative environmental impacts. For example, biomass energy generation would have to increase 7-fold to supply current primary energy demand, and up to 40-fold by 2100 given economic and energy growth projections. Humans already appropriate 30 to 40% of all photosynthetically fixed carbon worldwide, indicating that expansion of additional biomass harvesting is likely to stress ecosystems, in some cases precipitating collapse and extinction of animal species that have been deprived of vital food sources. The total amount of energy capture by vegetation in the United States each year is around 58 quads (61.5 EJ), about half of which is already harvested as agricultural crops and forest products. The remaining biomass is needed to maintain ecosystem functions and diversity. Since annual energy use in the United States is ca. 100 quads, biomass energy could supply only a very small fraction. To supply the current worldwide energy demand solely with biomass would require more than 10% of the Earth's land surface, which is comparable to the area use for all of world agriculture (i.e., ca. 1500 million hectares), indicating that further expansion of biomass energy generation will be difficult without precipitating an ethical conflict, given current world hunger statistics, over growing plants for biofuel versus food.
Given environmental concerns (e.g., fish migration, destruction of sensitive aquatic ecosystems, etc.) about building new dams to capture hydroelectric energy, further expansion of conventional hydropower in the United States is unlikely. Windpower, if deployed on the large scale necessary to substitute fossil energy, is likely to face public resistance. If 100% of U.S. energy demand were to be supplied by windmills, about 80 million hectares (i.e., more than 40% of all available farmland in the United States) would have to be covered with large windmills (50m hub height and 250 to 500 m apart). It is therefore not surprising that the major environmental impact of wind power is related to land use and less to wildlife (birds, bats, etc.) mortality. Unless only a relatively small fraction of electricity is generated by windmills in remote locations, it is unlikely that the public will tolerate large windfarms given concerns about blade noise and aesthetics.
Biofuels are different from fossil fuels in regard to net greenhouse gases but are similar to fossil fuels in that biofuels contribute to air pollution. Burning produces airborne carbon particulates, carbon monoxide and nitrous oxides.
This article possibly contains original research. (March 2017) (Learn how and when to remove this template message)
Renewable alternative forms of energy have faced opposition from multiple groups, including conservatives and liberals. Around twelve states have passed proposals written to inhibit the alternative energy movement. Kansas lawmakers struck down a bill to phase out renewable energy mandates but face the possibility of the bill reappearing.
The opposition cites the potentially high cost of branching out to these alternatives in order to support the continuation and reliance on fossil fuels. Ohio's mandate to phase in alternative energy faces opposition who believe higher electricity prices will result, while supporters fear the loss of economic development and jobs that alternative energy could bring.
With nuclear meltdowns in Chernobyl and Fukushima, nuclear power presents a constant danger and is more unlikely to be a popular alternative source. The costs of maintaining nuclear facilities, the potential risk of meltdowns, and the cost of cleaning up meltdowns are cited as reasons behind the movement away from the use of nuclear energy. In some countries nuclear power plants cannot compete with fossil fuels currently due to the latter's lower price and availability. Nuclear power plants also face competition from the increasing renewable energy subsidies.
Renewable energy does have some setbacks when relying on them completely. Spikes in the wholesale price of electricity occurred in South Australia when wind was not powering the turbines responsible for a large proportion of the region's power. This led to the government to reintegrate a gas-powered station to supply power while the wind turbines were unable to.
Solar panels are an icon of the 'green power' movement, however the process of manufacturing the quartz based panels can be detrimental to the environment. Raw quartz (silica) is used to create solar cells must be mined using harsh chemicals that harm the surrounding environment, as well as those working in the mines. Silicosis is a form of lung disease that is caused by the inhalation of crystalline silica dust resulting in nodule lesions in the lungs. The silica must be cultivated into metallurgical-grade silicon, the process requiring a massive amount of energy as the quartz is placed into electric arc furnaces. The metallurgical grade silica must be processed into polysilicon. This process also produces tetrachloride, a toxic substance that, if not disposed of correctly, can be harmful to the surrounding environment. Hydrochloric acid is formed when tetrachloride interacts with water, lowering water and soil pH. Incidents of tetrachloride spills are common in China, as the production of solar panels has shifted from Europe and the United States to Asian countries within the early 2000s. Because of such, the villagers of Gaolong are unable to leave their homes due to air and soil becoming toxic. This was due to Luoyang Zhongui High-Technology Co. repeatedly dumped tetrachloride in a nearby field for almost a year.
- Sustainable energy
- Alternative energy indexes
- Energy conservation
- Energy development
- Renewable energy commercialization
- Natural Bridges National Monument Solar Power System
- The Center, New Mexico
- Zehner, Ozzie (2012). Green Illusions. Lincoln and London: University of Nebraska Press. pp. 1–169, 331–42.
- Concise OED Alternative Energy. Accessed May 2, 2008.
- WordNet. Alternative Energy entry[permanent dead link].
- RICC 2007. Term Glossary Archived 2016-04-10 at the Wayback Machine..
- NRDC. Glossary.
- MMS. Definitions Archived 2010-07-05 at the Wayback Machine..
- Torridge District Council. TDLP Part 1 - Glossary Archived 2009-07-27 at the Wayback Machine..
- Gregory Clark; David Jacks (April 2010). "Coal and the Industrial Revolution, 1700-1869" (pdf). European Review of Economic History. European Historical Economics Society. Archived (PDF) from the original on 17 December 2008. Retrieved 2008-12-14. Lay summary. Clark and Jacks specifically refer to 18th century "alternative energy"
- Dr Roger White (2006-05-13). "Trees and Woods: Myths and Realities". Lecture: The Essential Role of Forests and Wood in the Age of Iron. Commonwealth Forestry Association. Archived from the original (doc) on 17 December 2008. Retrieved 2008-12-14. Note: Dr. White specifically refers to coal as a 17th-century alternative fuel in this paper.
- Douglas B. Reynolds. "Energy Grades and Historic Economic Growth" (doc). Hubbert Peak of Oil Production website. Archived from the original on 22 December 2008. Retrieved 2008-12-14.
- Norman F. Cantor (1993). The Civilization of the Middle Ages: The Life and death of a Civilization. Harper Collins. p. 564. ISBN 978-0-06-092553-6.
- "The City's Evolution–From Old Dartmouth to New Bedford, Whaling Metropolis of the World". Old Dartmouth Historical Society. Retrieved 2015-01-30.
- Alexander Graham Bell (1917). Prizes for the Inventor: Some of the Problems Awaiting Solution. The National Geographic Magazine. National Geographic Society. p. 133. Retrieved 2008-12-14. Lay summary.
In relation to coal and oil, the world's annual consumption has become so enormous that we are now actually within measurable distance of the end of the supply. What shall happen when there is no more coal or oil! .... There is, however, one other source of fuel supply which may perhaps this problem of the future. Alcohol makes a beautiful, clean and efficient fuel, and where not intended for human consumption can be manufactured very cheaply from corn stalks and in fact from almost any vegetable matter capable of fermentation.
- "Industry Statistics: Annual World Ethanol Production by Country". Renewable Fuels Association. Archived from the original on 2008-04-08. Retrieved 2008-05-02.
- Macedo Isaias; M. Lima Verde Leal & J. Azevedo Ramos da Silva (2004). "Assessment of greenhouse gas emissions in the production and use of fuel ethanol in Brazil" (PDF). Secretariat of the Environment, Government of the State of São Paulo. Archived from the original (PDF) on 28 May 2008. Retrieved 2008-05-09.
- Daniel Budny; Paulo Sotero, eds. (April 2007). "Brazil Institute Special Report: The Global Dynamics of Biofuels" (PDF). Brazil Institute of the Woodrow Wilson Center. Archived from the original (PDF) on 28 May 2008. Retrieved 2008-05-03.
- Biofuels look to the next generation
- Cellulosic Ethanol: Not Just Any Liquid Fuel Archived 2008-10-23 at the Wayback Machine.
- Building Cellulose
- bioenergywiki.net:Second-generation biofuels
- Inbicon - about the plant Archived 2014-02-21 at the Wayback Machine.
- Wong, Bill (June 28, 2011), "Drake Landing Solar Community" Archived 2016-03-04 at the Wayback Machine., IDEA/CDEA District Energy/CHP 2011 Conference, Toronto, pp. 1–30, retrieved 21 April 2013
- Wong B., Thornton J. (2013). Integrating Solar & Heat Pumps. Renewable Heat Workshop.
- Including solar and radiant energy.
- Elisabeth Rosenthal (2007-01-31). "Once a Dream Fuel, Palm Oil May Be an Eco-Nightmare". New York Times. Archived from the original on February 11, 2012. Retrieved 2008-12-14.
- Lester R. Brown (2007-06-13). "Biofuels Blunder:Massive Diversion of U.S. Grain to Fuel Cars is Raising World Food Prices, Risking Political Instability". Testimony before U.S. Senate Committee on Environment and Public Works. Archived from the original on 2009-04-04. Retrieved 2008-12-20.
- Leighty and Holbrook (2012) "Running the World on Renewables: Alternatives for Transmission and Low-cost Firming Storage of Stranded Renewables as Hydrogen and Ammonia Fuels via Underground Pipelines" Proceedings of the ASME 2012 International Mechanical Engineering Congress & Exposition November 9–15, 2012, Houston, Texas
- Graves, Christopher; Ebbesen, Sune D.; Mogensen, Mogens; Lackner, Klaus S. (2011). "Sustainable hydrocarbon fuels by recycling CO2 and H2O with renewable or nuclear energy". Renewable and Sustainable Energy Reviews. 15 (1): 1–23. doi:10.1016/j.rser.2010.07.014. Retrieved September 7, 2012. (Review.)
- Holte, Laura L.; Doty, Glenn N.; McCree, David L.; Doty, Judy M.; Doty, F. David (2010). Sustainable Transportation Fuels From Off-peak Wind Energy, CO2 and Water (PDF). 4th International Conference on Energy Sustainability, May 17–22, 2010. Phoenix, Arizona: American Society of Mechanical Engineers. Retrieved September 7, 2012.
- "First Commercial Plant". Carbon Recycling International. Archived from the original on 3 July 2013. Retrieved 11 July 2012.
- "George Olah CO2 to Renewable Methanol Plant, Reykjanes, Iceland" (Chemicals-Technology.com)
- "First Commercial Plant" Archived 2016-02-04 at the Wayback Machine. (Carbon Recycling International)
- Center for Solar Energy & Hydrogen Research Baden-Württemberg (2011). "Verbundprojekt 'Power-to-Gas'" (in German). zsw-bw.de. Archived from the original on February 16, 2013. Retrieved September 9, 2012.
- Center for Solar Energy & Hydrogen Research (July 24, 2012). "Bundesumweltminister Altmaier und Ministerpräsident Kretschmann zeigen sich beeindruckt von Power-to-Gas-Anlage des ZSW" (in German). zsw-bw.de. Archived from the original on September 27, 2013. Retrieved September 9, 2012.
- Okulski, Travis (June 26, 2012). "Audi's Carbon Neutral E-Gas Is Real And They're Actually Making It". Jalopnik (Gawker Media). Retrieved 29 July 2013.
- Rousseau, Steve (June 25, 2013). "Audi's New E-Gas Plant Will Make Carbon-Neutral Fuel". Popular Mechanics. Retrieved 29 July 2013.
- "Doty Windfuels". Windfuels.com. Retrieved 2012-11-01.
- "CoolPlanet Energy Systems". Coolplanetbiofuels.com. 2012-10-24. Retrieved 2012-11-01.
- "Air Fuel Synthesis, Ltd". Airfuelsynthesis.com. Retrieved 2012-11-01.
- Lackner, Klaus S.; et al. (2012). "The urgency of the development of CO2 capture from ambient air". Proceedings of the National Academy of Sciences of the United States of America. 109 (33): 13156–62. Bibcode:2012PNAS..10913156L. doi:10.1073/pnas.1108765109. PMC . PMID 22843674. Retrieved September 7, 2012.
- Eisaman, Matthew D.; et al. (2012). "CO2 extraction from seawater using bipolar membrane electrodialysis" (PDF). Energy and Environmental Science. 5 (6): 7346–52. doi:10.1039/C2EE03393C. Retrieved July 6, 2013.
- Goeppert, Alain; Czaun, Miklos; Prakash, G.K. Surya; Olah, George A. (2012). "Air as the renewable carbon source of the future: an overview of CO2 capture from the atmosphere". Energy and Environmental Science. 5 (7): 7833–53. doi:10.1039/C2EE21586A. Retrieved September 7, 2012. (Review.)
- Pearson, R.J.; Eisaman, M.D.; et al. (2012). "Energy Storage via Carbon-Neutral Fuels Made From CO2, Water, and Renewable Energy". Proceedings of the IEEE. 100 (2): 440–60. doi:10.1109/JPROC.2011.2168369. Retrieved September 7, 2012.
- Fraunhofer-Gesellschaft (May 5, 2010). "Storing green electricity as natural gas". fraunhofer.de. Retrieved September 9, 2012.
- SolarLeaf - bioreactor facade, ARUP Creates First Algae Facade That Produces Energy.
- "Biomass Briquettes". 27 August 2009. Retrieved 19 February 2009.
- "Biogas Technology". 27 March 2009. Archived from the original on 25 May 2009. Retrieved 24 June 2009.
- Hijikata, Tsuneo (2001). "Research and Development of International Clean Energy Network Using Hydrogen Energy". International Journal of Hydrogen Energy. 27: 115–129. doi:10.1016/s0360-3199(01)00089-1.
- P. 12, BMW Group Clean Energy ZEV Symposium, September 2006
- Ghirardi ML; Togasaki RK; Seibert M (1997). "Oxygen Sensitivity of Algal H2-Production". Applied Biochemistry and Biotechnology. 63-65 (1): 141–51. doi:10.1007/BF02920420. PMID 18576077.
- Radmer R; Kok B (1977). "Photosynthesis: Limited Yields, Unlimited Dreams". BioScience. 29 (9): 599–605. doi:10.2307/1297655.
- Gaffron H; Rubin J (1942). "Fermentative and Photochemical Production of Hydrogen in Algae". Journal of General Physiology. 26 (2): 219–240. doi:10.1085/jgp.26.2.219. PMC . PMID 19873339.
- Melis A; Neidhardt J; Benemann JR (1999). "Dunaliella salina (Chlorophyta) with Small Chlorophyll Antenna Sizes Exhibit Higher Photosynthetic Productivities and Photon Use Efficiencies Than Normally Pigmented Cells". Journal of Applied Physiology. 10: 515–52.
- Melis A; Happe T (2001). "Hydrogen Production — Green Algae as a Source of Energy". Plant Physiology. 127 (3): 740–8. doi:10.1104/pp.010498. PMC . PMID 11706159.
- Doebbe A; Rupprecht J; Beckmann J; Mussgnug JH; Hallmann A; Hankamer B; Kruse O (2007). "Functional Integration of the HUP1 Hexose Symporter Gene into the Genome of C. reinhardtii: Impacts on Biological H2 Production". Journal of Biotechnology. 131 (1): 27–33. doi:10.1016/j.jbiotec.2007.05.017. PMID 17624461.
- Historical Data Workbook (2013 calendar year) Archived 2014-06-22 at the Wayback Machine.
- "Archived copy" (PDF). Archived from the original (PDF) on 2016-03-03. Retrieved 2016-01-18.
- Renewables 2015. Global Status Report Ren21, retrieved 20th January 2016.
- Horton, Jennifer. (19 August 2008). "5 Wacky Forms of Alternative Energy". Archived from the original on 22 June 2009. Retrieved 15 June 2009.
- "Hywind by Statoil". 11 February 2009. Retrieved 24 June 2009.
- Kang, J.; Von Hippel, F. N. (2001). "U‐232 and the proliferation‐resistance of U‐233 in spent fuel". Science & Global Security. 9: 1–32. doi:10.1080/08929880108426485. "Archived copy" (PDF). Archived from the original (PDF) on 2014-12-03. Retrieved 2015-03-02.
- Nuclear Materials FAQ
- Robert Hargraves; Ralph Moir (January 2011). "Liquid Fuel Nuclear Reactors". American Physical Society Forum on Physics & Society. Retrieved 31 May 2012.
- McKenna, Paul (5 December 2012). "Is the "Superfuel" Thorium Riskier Than We Thought?". Popular Mechanics. Retrieved 2 March 2015.
- Rees, Eifion (23 June 2011). "Don't believe the spin on thorium being a greener nuclear option". Guardian. Retrieved 2 March 2015.
- "SolarCity Stock Market Cap Makes It No. 2 Solar Firm".
- "WilderHill New Energy Global Innovation Index".
- "Calvert Global Alternative Energy Fund (CGAEX)". Archived from the original on 2014-11-06.
- "Solar Mosaic fully crowd funds its new solar projects in less than 24 hours".
- Konrad, Tom (2013-01-08). "New Ways to Invest in Solar Like Buffett". Forbes.
- http://electronicdesign.com/article/power/is-solar-energy-really-ready-to-rumble-19153.aspx[permanent dead link]
- Bruce Upbin (2007-12-24). "Greenhouse Stocks". Forbes. Archived from the original on 11 December 2007. Retrieved 2007-12-24.
- Gas Prices post third straight record, CNN Money
- Foster, Peter (24 Mar 2009). "China takes on America in electric car race." London: Telegraph Media Group Limited. Archived from the original on 27 March 2009. Retrieved 2009-05-11.
- "Transform Your Drive".
- S.C.E. Jupe; A. Michiorri; P.C. Taylor (2007). "Increasing the energy yield of generation from new and renewable energy sources". Renewable Energy. 14 (2): 37–62. doi:10.5772/7379.
- "Defense-scale supercomputing comes to alternative energy research". Sandia National Laboratories. Retrieved 2012-04-16.
- "Sandia National Laboratories" (PDF). Sandia National Laboratories. Retrieved 2012-04-16.
- *Chakrabarty, Gargi, April 16th, 2009. "Stimulus leaves NREL in cold" Denver Post"
- International Renewable Energy Agency (IRENA). (2016). Renewable Energy Benefits: Measuring the Economics. Abu Dhabi, United Arab Emirates
- Jacobson, M.Z. Delucch, M.A. Bauer, Z.A. (2017, April 7). 100% Clean and Renewable Wind, Water, and Sunlight (WWS) All-Sector Energy Roadmaps for 139 Countries of the World. Atmosphere/Energy Program, Department of Civil and Environmental Engineering, Stanford University. pg 1-12
- Wu, Fan; Cai, Wei; Yeh, Yao-Wen; Xu, Shiyou; Yao, Nan (2016-03-01). "Energy scavenging based on a single-crystal PMN-PT nanobelt". Scientific Reports. 6: 22513. Bibcode:2016NatSR...622513W. doi:10.1038/srep22513. ISSN 2045-2322. PMC . PMID 26928788.
- Holm L. (2012). Long-Term Experiences with Solar District Heating in Denmark[permanent dead link]. Presentation. European Sustainable Energy Week, Brussels. 18–22 June 2012.
- Pauschinger T. (2012). Solar District Heating with Seasonal Thermal Energy Storage in Germany. Presentation. European Sustainable Energy Week, Brussels. 18–22 June 2012.
- Solar District Heating (SDH) platform website. Europe.
- Solar Heating and Cooling programme, of the International Energy Agency. website.
- "Improvement of efficiency for solar photovoltaic cell application" (PDF). BRAC University. Retrieved 2012-04-16.
- Chakrabarty, Gargi. "Stimulus leaves NREL in cold". Denver Post. Retrieved 2012-04-16.
- "Solar Research". NREL. Retrieved 2012-04-16.
- "Photovoltaics". Sandia. Retrieved 2012-04-16.
- "'Major discovery' from MIT primed to unleash solar revolution". MIT News. Retrieved 2012-04-17.
- "DOE Global Energy Storage Database". www.energystorageexchange.org. Retrieved 2017-05-10.
- "Breakthrough: World's most efficient solar panel". SmartPlanet. Retrieved 2012-04-17.
- "Wind energy research reaps rewards". NASA. Retrieved 2012-04-17.
- "Wind energy". Sandia. Retrieved 2012-04-17.
- "Wind research". NREL. Retrieved 2012-04-17.
- "Wind resource evaluation at the Caltech Field Laboratory for Optimized Wind Energy (FLOWE)" (PDF). Caltech. Retrieved 2012-04-17.
- "Archived copy" (PDF). Archived from the original (PDF) on 2015-07-21. Retrieved 2015-08-28. page 27
- In many context the term "biomaterial" refers specifically to the body-friendly materials in medical implantation, etc.; here it is used literally.
- Biomass Energy Center. Biomassenergycentre.org.uk. Retrieved on 28 February 2012.
-  Retrieved on 12 April 2012.
- T.A. Volk; L.P. Abrahamson (January 2000). "Developing a Willow Biomass Crop Enterprise for Bioenergy and Bioproducts in the United States". North East Regional Biomass Program. Retrieved 4 June 2015.
- "Archived copy". Archived from the original on 2016-01-04. Retrieved 2013-10-24.
- American Coalition for Ethanol (2008-06-02). "Responses to Questions from Senator Bingaman" (PDF). American Coalition for Ethanol. Archived from the original (PDF) on 2011-10-04. Retrieved 2012-04-02.
- National Renewable Energy Laboratory (2007-03-02). "Research Advantages: Cellulosic Ethanol" (PDF). National Renewable Energy Laboratory. Archived from the original (PDF) on 2012-01-25. Retrieved 2012-04-02.
- M.R. Schmer; K.P. Vogel; R.B. Mitchell; R.K. 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 . PMID 18180449.
- Charles E. Wyman (2007). "What is (and is not) vital to advancing cellulosic ethanol". Trends in Biotechnology. 25 (4): 153–157. doi:10.1016/j.tibtech.2007.02.009. PMID 17320227.
- Sandia National Laboratories. "Biomass". Sandia National Laboratories. Archived from the original on 2012-05-10. Retrieved 2012-04-17.
- Joint BioEnergy Initiative. "About JBEI". Sandia National Laboratories. Archived from the original on 2012-05-25. Retrieved 2012-04-17.
- "Valcent Products Inc. Develops "Clean Green" Vertical Bio-Reactor". Valcent Products. Archived from the original on 18 June 2008. Retrieved 2008-07-09.
- "Technology: High Yield Carbon Recycling". GreenFuel Technologies Corporation. Archived from the original on 2007-08-21. Retrieved 2008-07-09.
- B.N. Divakara; H.D. Upadhyaya; S.P. Wani; C.L. Laxmipathi Gowda (2010). "Biology and genetic improvement of Jatropha curcas L.: A review". Applied Energy. 87 (3): 732–742. doi:10.1016/j.apenergy.2009.07.013.
- Biofuels Digest (2011-05-16). "Jatropha blooms again: SG Biofuels secures 250K acres for hybrids". Biofuels Digest. Retrieved 2012-03-08.
- Biofuels Magazine (2011-04-11). "Energy Farming Methods Mature, Improve". Biofuels Magazine. Retrieved 2012-03-08.
- L. Ryback (2007). "Geothermal Sustainability". GHC Bulletin: 2–6.
- NREL. "Geothermal Technologies". NREL. Retrieved 2012-04-17.
- Sandia. "Geothermal". Sandia. Retrieved 2012-04-17.
- GFZ Helmholtz Center Potsdam. "International Centre for Geothermal Research". GFZ Helmholtz Center Potsdam. Retrieved 2012-04-17.
- Jeff Wise. "The Truth about hydrogen". Popular Mechanics. Retrieved 2012-04-17.
- NREL. "Hydrogen". NREL. Retrieved 2012-04-17.
- Sandia. "Hydrogen". Sandia. Retrieved 2012-04-17.
- Huesemann, Michael H., and Joyce A. Huesemann (2011). Technofix: Why Technology Won’t Save Us or the Environment, "Challenge #1: Serious Environmental Impacts of Large-scale Renewable Energy Generation", New Society Publishers, ISBN 0865717044, pp. 125-133.
- Rojstaczer, S.; Sterling, S.M.; Moore, N.J. (2001). "Human appropriation of photosynthesis products". Science. 294: 2549–2552. Bibcode:2001Sci...294.2549R. doi:10.1126/science.1064375.
- Vitousek, P.M.; Ehrlich, P.R.; Ehrlich, A.H.; Matson, P.A. (1986). "Human appropriation of the products of photosynthesis". BioScience. 36 (6): 368–373. doi:10.2307/1310258.
- Pimentel, D.; et al. (1994). "Achieving a secure energy future: environmental and economic issues". Ecological Economics. 9: 201–219. doi:10.1016/0921-8009(94)90078-7.
- Hoffert, M.I.; et al. (2002). "Advanced technology paths to global climate change stability: energy for a greenhouse planet". Science. 298: 981–987. Bibcode:2002Sci...298..981H. doi:10.1126/science.1072357. PMID 12411695.
- Nakicenovic, N., A. Gruebler, and A. McDonald (1998). Global Energy Perspective, Cambridge University Press
- Elliott, D.L., L.L. Wendell, and G.L. Gower (1992), "Wind energy potential in the United States considering environmental and land use exclusions", In: Proceedings of the Biennial Congress of the International Solar Energy Society – Solar World Congress in Denver, Colorado, edited by M.E. Ardan, S.M.A. Burley, and M. Coleman, Pergamon, Oxford, UK.
- Elliott, D., (1997). Energy, Society, and Environment – Technology for a Sustainable Future, Chapter 11, "Case Study: Public Reaction of UK Windfarms", Routledge
- Wuestenhagen, R.; Welsink, M.; Buerer, M.J. (2007). "Social acceptance of renewable energy innovations – an introduction to the concept". Energy Policy. 35: 2683–2691. doi:10.1016/j.enpol.2006.12.001.
- Cardwell, Diane. "A Pushback on Green Power". The New York Times. The New York Times. Retrieved February 22, 2017.
- Porter, Eduardo. "How Renewable Energy is Blowing Climate Change Efforts off Course". The New York Times. The New York Times. Retrieved 26 February 2017.
- Eunjung Cha, Ariana (March 9, 2008). "Solar Energy Firms Leave Waste Behind in China". The Washington Post.
- Armstrong, Robert C., Catherine Wolfram, Robert Gross, Nathan S. Lewis, and M.V. Ramana et al. The Frontiers of Energy, Nature Energy, Vol 1, 11 January 2016.
- NREL Publication Database - a list of publications from the National Renewable Energy Laboratory
- Unintended Consequences of Green Technologies - a concise University of California, Berkeley summary of the unintended consequences of alternative energy technologies
- "A Skeptic Looks at Alternative Energy," by Vaclav Smil, IEEE Spectrum, July 2012
- "Rethinking the world's power: alternative energy sources" by Wilson da Silva, Cosmos, April 2012
- Tethys - an online knowledge management system that provides the marine and hydrokinetic (MHK) and offshore wind (OSW) energy communities with access to information and scientific literature on environmental effects of MHK and OSW developments
- GA Mansoori, N Enayati, LB Agyarko (2016), Energy: Sources, Utilization, Legislation, Sustainability, Illinois as Model State, World Sci. Pub. Co., ISBN 978-981-4704-00-7