Alternative energy

File:Wind turbine lg.jpg

Wind turbines near farm fields

Alternative energy is a term for any nontraditional energy form, source, or technology differing from the current popular forms, sources, or technologies. Today, it is generally used in the context of an alternative to energy deriving from popular fossil fuels and thus includes energy derived from such environmentally preferred sources as solar, water power, biomass, wind, geothermal, ocean thermal, wave action, and tidal action.

The term alternative energy also is used for energy derived from sources and technologies that do not involve the depletion of natural resources or significant harm to the environment. As such, it is used synonymously with "renewable energy" and "green power." While by most definitions there is substantial overlap between energy forms, sources, and technologies that fit into these three categories, and alternative energy often is applied to energy without undesirable environmental consequences or with lessened environmental impact, the three terms also have been delineated differently. Renewable energy generally refers most specifically to energy derived from sustainable natural resources that are constantly replenished within a relatively short time frame (such as deriving from such renewable natural resources as biomass, sunlight, wind, water, and so forth), while "green power" references that subset of renewable energy that involves the least environmental harm. As delineated in the first paragraph, before natural gas gained popularity, this energy source could be classified under the category of alternative energy, but not that of renewable energy.

Definitions

There are a multitude of definitions used for alternative energy.

Source	Definition
U.S. Environmental Protection Agency	Energy derived from nontraditional sources (e.g., compressed natural gas, solar, hydroelectric, wind).
Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report	Energy derived from non-fossil fuel sources.
Collins English Dictionary	Also called: renewable energy. A form of energy derived from a natural source, such as the sun, wind, tides, or waves.
Random House Dictionary	Energy, as solar, wind, or nuclear energy, that can replace or supplement traditional fossil-fuel sources, as coal, oil, and natural gas.
Princeton WordNet	Energy derived from sources that do not use up natural resources or harm the environment.
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).

Other definitions abound. Nelson (2014) notes that coal could have been considered an alternative energy when it replaced wood, noting "alternative energy can be defined as the search for energy improvements in a humane way." Weaver (2014), noting the variety of definitions, offers both a limited definition referring "only to energy that is derived from a source other than fossil fuels," which would not include natural gas, and a broader definition "as a term to describe energy sources other than petroleum based," which "allows for inclusion of natural gas fueled vehicles and also eliminates debate over whether electric cars should be considered alternative energy vehicles." Smith and Taylor (2008), in their book Renewable and Alternative Energy Resources, define alternative energy technologies as "those that are not derived from fossils fuels but that also are considered nonrenewable" with renewable energy technologies as those that harness energy from an inexhaustible source" (sun, wind, waves, biomass, falling water, heat generated beneath the surface of the earth).

Many definitions of alternative energy, as noted above, use this term interchangeable with renewable energy. The US Environmental Protection Agency (2014) defines renewable energy as "Energy resources that are naturally replenishing such as biomass, hydro, geothermal, solar, wind, ocean thermal, wave action, and tidal action." The EPA's Green Power Partnership (2013) defines the term as "renewable energy includes resources that rely on fuel sources that restore themselves over short periods of time and do not diminish." The Intergovernmental Panel on Climate Change (2001) defines renewables as "energy sources that are, within a short timeframe relative to the earth’s natural cycles, sustainable, and include non-carbon technologies such as solar energy, hydropower, and wind, as well as carbon neutral technologies such as biomass." Gritse

• Green Power Partnership. 2013. [http://epa.gov/greenpower/gpmarket/index.htm Green power defined}. Environmental Protection Agency. Retrieved January 14, 2014.

Alternative energy sources, forms, and technologies

Today, the following are among those energies considered as alternative energies:

• Solar
• Wind
• Geothermal
• Water power or hydropower
• Biomass
  • Biofuel
  • Waste
  • Wood
• Tidal power
• Wave power

http://www.eia.gov/totalenergy/data/monthly/pdf/sec10.pdf

• Biofuel and Ethanol are plant-derived gasoline substitutes for powering vehicles.
• Nuclear binding energy uses nuclear fission to release energy.
• Hydrogen is burned and used as clean fuel for spaceships and some cars.

tides

Solar

About half the incoming solar energy reaches the Earth's surface.

Broadly speaking, solar energy is energy from the Sun. About 174 petawatts (PW 10¹⁵ watts) of solar radiation reaches the Earth's atmosphere every year (Smil 1991). Approximately 30% is reflected back to space while the rest is absorbed by clouds, oceans, and land masses(for about 3,850,000 exajoules (EJ) per year (Smil 2006)), with roughly 50% reaching the surface of the Earth. Overall, the energy in sunlight yields about 1000 watts per square meter on a cloudless day at noon, and averaged over the entire Earth's surface each square meter collects about 4.2 kilowatt-hours of energy every day (GWSI 2009). This light can be changed into thermal (heat) energy and converted by photosynthesis into chemical energy that can be used to fuel organisms' activities. This solar energy drives climate and the weather and supports virtually all life on Earth.

Part of the 354 MW SEGS solar complex in northern San Bernadino County, California.

In terms of alternative energy, solar energy refers to the energy that is harnessed from solar radiation, using the radiant light and heat from the Sun for practical purposes. The term solar power either is used synonymously with solar energy or is used more specifically to refer to the conversion of sunlight into electricity. Solar energy can be harnessed at different levels around the world, mostly depending on distance from the equator.

In actuality, almost all renewable energies, notably excluding geothermal and tidal, derive their energy from the sun. For example, winds blow partly because of absorption of solar radiation by the Earth's atmosphere. Even non-renewable energy sources such as coal, gas, and oil involve the storing of energy from sunlight preserved under the Earth's crust. Among solar-based renewable resources, wind and wave power, hydroelectricity, and biomass account for over 99.9 percent of the available flow of renewable energy (Smil 2006; Scheer 2002).

Solar energy radiant light and heat from the sun is harnessed using a range of ever-evolving technologies such as solar heating, solar photovoltaics, solar thermal electricity, solar architecture, and artificial photosynthesis (IEA 2011; RSC 2014). Technologies to harness the sun's energy date from the time of the early Greeks, Indian, Native Americans, and Chinese, who warmed their buildings by orienting them toward the sun (Butti and Perlin 1981). British astronomer John Herschel used a solar thermal collector box during an expedition to Africa to cook food (EIA 2014). Modern solar technologies provide heating, lighting, electricity and even flight (USDOE).

There are many technologies for harnessing solar energy within these broad classifications: active, passive, direct and indirect.

• Active solar systems use electrical and mechanical components such as tracking mechanisms, pumps, and fans to capture sunlight and process it into usable outputs such as heating, lighting or electricity.
• Passive solar systems use non-mechanical techniques to control the capture of sunlight and distribute this energy into usable outputs such as heating, lighting, cooling, or ventilation. These techniques include selecting materials with favorable thermal properties to absorb and retain energy, designing spaces that naturally circulate air to transfer energy and referencing the position of a building to the sun to enhance energy capture. In some cases passive solar devices can have mechanical movement with the important distinction that this movement is automatic and directly powered by the sun.
• Direct solar generally refers to technologies or effects that involve a single-step conversion of sunlight that results in a usable form of energy.
• Indirect solar generally refers to technologies or effects that involve multiple-step transformations of sunlight that result in a usable form of energy.

The collecting of solar radiation and converting it into electricity—the production of solar power—can be done in two two ways: (1) directly using photovoltaics (PV devices) or "solar cells"; or (2) indirectly using solar thermal/electric power plants. The first method involves grouping individual PV cells into panels and arraying panels, ranging from small cells to power watches and calculators to those that power single homes to those that produce electricity in power plants covering many acres. The second way uses concentrated solar power (CSP), whereby lenses or mirrors to concentrate a large area of sunlight, or solar thermal energy, onto a small area. Electrical power is produced when the concentrated light is converted to heat, which drives a heat engine (usually a steam turbine) connected to an electrical power generator or powers a thermochemical reaction. In 2012, there were 12 such power plants in the United States (EIA 2014).

Benefits of solar energy system include the huge potential in terms of energy hitting the earth, the low environmental impact, and the lack of producing carbon dioxide and air pollutants. Limitations preventing the large scale implementation of solar powered energy generation is the inefficiency of current solar technology and the cost. In addition, the amount of sunlight varies depending on weather conditions, location, time of day, and time of year, and the need for a large surface to collect the energy, since it does not deliver concentrated energy at any one place (IEA 2014).

Wind

Trends in the top five countries generating electricity from wind, 1980-2012 (US EIA)

Generally speaking, wind energy is the form of energy created by wind. Wind, the flow of air on a large scale, is caused by differences in atmospheric pressure. When a difference in atmospheric pressure exists, air moves from the higher to the lower pressure area, resulting in winds of various speeds. Globally, the two major driving factors of large-scale wind patterns (the atmospheric circulation) are the differential heating between the equator and the poles (difference in absorption of solar energy leading to buoyancy forces) and the rotation of the planet.

In terms of alternative energy, wind energy refers to the energy that is harnessed from wind for practical purposes. The term wind power is used synonymously as the conversion of wind energy into a useful form of energy, or more specifically as the generation of electricity from the wind. Among ways in which wind energy can be harnessed are wind turbines to make electrical power, windmills for mechanical power, windpumps for water pumping or drainage, or sails to propel ships.

Large wind farms consist of hundreds of individual wind turbines that are connected to the electric power transmission network. For new constructions, onshore wind is an relative inexpensive source of electricity, while small onshore wind farms provide electricity to isolated locations. Utility companies increasingly buy surplus electricity produced by small domestic wind turbines. Offshore wind is steadier and stronger than on land, and offshore farms have less visual impact, but construction and maintenance costs are considerably higher. Floating wind farms are similar to a regular wind farm, but the difference is that they float in the middle of the ocean. Offshore wind farms can be placed in water up to 40 meters (130 ft) deep, whereas floating wind turbines can float in water up to 700 meters (2,300 ft) deep (Horton 2008). 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.

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 warmest hours of 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 (Pearson 2012).

Wind power offers a number of benefits as an alternative to fossil fuels. It is plentiful, renewable, widely distributed, clean, produces no greenhouse gas emissions during operation, and uses little land. The effects on the environment are generally less problematic than those from other power sources. Costs are relatively low and once the infrastructure is paid for it is virtually free (Siegel 2012).

The main disadvantage of wind power is the fact that wind is unpredictable, inconsistent, and unsteady, as well as the concern that the full costs of harnessing wind power are not cheap and thus rely on government subsidies to be set up and be competitive. There also are aesthetic concerns, with wind farms being considered by some to be an eyesore, whether restricting the normally picturesque view offshore or in rural areas. Furthermore, there are complaints of noise from turbines, and some communities have been required to shut off their turbines during certain times because of the noise. Older type wind farms have turbines that spin at high speeds and can thus kill wild birds and bats, although this design has changed so newer wind farms largely avoid such a problem (Siegel 2012).

As of 2011, Denmark is generating more than a quarter of its electricity from wind and 83 countries around the world are using wind power to supply the electricity grid (Sawin et al. 2011). In 2010 wind energy production was over 2.5% of total worldwide electricity usage, and growing rapidly at more than 25% per annum.

Geothermal

Geothermal resource map of the United States

In general terms, geothermal energy is thermal energy (the energy that determines the temperature of matter) generated and stored in the Earth. The geothermal energy of the Earth's crust originates from the original formation of the planet (20%) and from radioactive decay of minerals (80%). The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heat from the core to the surface.

In terms of alternative energy, geothermal energy is the use of the Earth's internal heat for practical purposes and in particular to boil water for heating buildings or generating electricity. Geothermal energy is produced by tapping into the thermal energy created and stored within the earth. It is considered sustainable because that thermal energy is constantly replenished (Ryback 2007). 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, conduct 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.

In the United States, geothermal is one of the renewable energy resources used to produce electricity, but its growth is slower than that of wind and solar energy development and a November 2011 report noted that it produced just 0.4% of the electricity from all sectors nationally during the first 8 months of that year, with 10,898 million kilowatthours (kWh) produced during that time. However, about 5% of the electricity generated in California was produced from geothermal, although there are significant geothermal resources that could be utilized (EIA 2011).

Geothermal thermal energy is used to generate electricity typically via a well that is drilled into an underground reservoir of water that can be as hot as 371 degrees Celsius (700 Fahrenheit). At the surface, a turbine is turned using the trapped steam. Heat pumps are used to move fluids through pipelines buried underground at depths where the temperature does not change much and delivered to a home or commercial building. During the summer, this pipeline can pull heat out of a building and uses cooler fluid to cool the building. Geothermal water also is found in geysers or hot springs on the Earth's surface (EIA 2011).

Geothermal provides a clear, sustainable, environmentally friendly and substantial resource. However, it also faces challenges in that geothermal plants generally are site-specific and limited to regions with accessible deposits of high temperature ground water, the completing of a geothermal plant takes significant time (four to eight years) versus the times for wind or solar, and there is a lack of transmission lines (EIA 2011).

Water power or hydropower

The 22,500 MW Three Gorges Dam in the Peoples Republic of China, the largest hydroelectric power station in the world.

The energy of falling water and running water can be utilized to provide water power or hydropower—the form of renewable energy derived from the gravitational force of falling or flowing water harnessed for useful purposes. Since ancient times, hydropower has been used for irrigation and the operation of various mechanical devices, such as watermills, sawmills, textile mills, dock cranes, domestic lifts, and power houses.

Since the early 20th century, the term hydropower has been used almost exclusively in conjunction with the modern development of hydroelectric power, which allowed use of distant energy sources. Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water.

Another method used to transmit energy used a trompe: a water-powered gas compressor, commonly used before the advent of the electric-powered compressor, which is somewhat like an airlift pump working in reverse. A trompe produces compressed air from falling water. Compressed air could then be piped to power other machinery at a distance from the waterfall.

Hydroelectricity today is the most widely used form of renewable energy (unless all biomass categories, such as wood and biofuels, are lumped together), accounting for 16 percent of global electricity generation—3,427 terawatt-hours of electricity production in 2010. China is the largest hydropower producer, producing 721 terawatt-hours in 2010 and having the highest installed hydropower capacity, with 213 gigawatts (GW) at the end of 2010. Hydropower is produced in at least 150 countries, with five countries (China, Brazil, United States, Canada, and Russia) accounting for about 52 percent of the world’s installed hydropower capacity in 2010 (Worldwatch 2012).

The cost of hydroelectricity is relatively low, making it a competitive source of renewable electricity. The average cost of electricity from a hydro plant larger than 10 megawatts is 3 to 5 U.S. cents per kilowatt-hour (Worldwatch 2012). Hydro is also a flexible source of electricity since plants can be ramped up and down very quickly to adapt to changing energy demands. Once a hydroelectric complex is constructed, the project produces no direct waste, and has a considerably lower output level of the greenhouse gas carbon dioxide (CO₂) than fossil fuel powered energy plants (Sawin et al. 2011). However, damming interrupts the flow of rivers and can harm local ecosystems, and building large dams and reservoirs often involves displacing people and wildlife.

Biomass

US Renewable Energy Consumption

Biomass refers to biological material derived from living or recently living organisms, such as plants or plant-derived materials. 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. This biomass conversion can result in fuel in solid, liquid, or gas form.

Wood remains the largest biomass energy source today.

Biofuel

US Renewable Energy Consumption (quadrillion BTU)

A biofuel is a fuel (a material that stores potential energy in forms that can be practicably released and used as heat energy) that contains energy from geologically recent carbon fixation. These fuels are produced from living organisms. Examples of this carbon fixation occur in plants and microalgae.Biofuels have increased in popularity because of rising oil prices and the need for energy security.

In 2010, worldwide biofuel production reached 105 billion liters (28 billion gallons US), up 17% from 2009 (Worldwatch 2011). Global ethanol fuel production reached 86 billion liters (23 billion gallons US) in 2010, with the United States and Brazil as the world's top producers, accounting together for 90% of global production. The world's largest biodiesel producer is the European Union, accounting for 53% of all biodiesel production in 2010 (Worldwatch 2011).

Bioalcohols. Biologically produced alcohols, most commonly ethanol, and less commonly propanol and butanol, are produced by the action of microorganisms and enzymes through the fermentation of sugars or starches (easiest), or cellulose (which is more difficult). Biobutanol (also called biogasoline) is often claimed to provide a direct replacement for gasoline, because it can be used directly in a gasoline engine (in a similar way to biodiesel in diesel engines). Alcohol fuels are produced by fermentation of sugars derived from wheat, corn, sugar beets, sugar cane, molasses and any sugar or starch from which alcoholic beverages can be made (such as potato and fruit waste, etc.).

Bioethanol. Ethanol fuel, or bioethanol, is the most common biofuel worldwide, particularly in Brazil, but also in the United States and elsewhere. The ethanol production methods used are enzyme digestion (to release sugars from stored starches), fermentation of the sugars, distillation, and drying. Ethanol is produced mostly from carbohydrates produced in sugar or starch crops such as corn or sugarcane. The distillation process requires significant energy input for heat (often unsustainable natural gas fossil fuel, but cellulosic biomass such as bagasse, the waste left after sugar cane is pressed to extract its juice, can also be used more sustainably). 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. Current plant design does not provide for converting the lignin portion of plant raw materials to fuel components by fermentation.

Biodiesel. Biodiesel is made from vegetable oils and animal fats. 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.

Other biofuels.

Straight unmodified edible vegetable oil is generally not used as fuel, but lower-quality oil can and has been used for this purpose. Used vegetable oil is increasingly being processed into biodiesel, or (more rarely) cleaned of water and particulates and used as a fuel.

Cellulosic ethanol commercialization is the process of building an industry out of methods of turning cellulose-containing organic matter into fuel. Companies, such as Iogen, POET, and Abengoa, are building refineries that can process biomass and turn it into bioethanol. Companies, such as Diversa, Novozymes, and Dyadic, are producing enzymes that could enable a cellulosic ethanol future. The shift from food crop feedstocks to waste residues and native grasses offers significant opportunities for a range of players, from farmers to biotechnology firms, and from project developers to investors.

As of 2013, the first commercial-scale plants to produce cellulosic biofuels have begun operating. Multiple pathways for the conversion of different biofuel feedstocks are being used. In the next few years, the cost data of these technologies operating at commercial scale, and their relative performance, will become available. Lessons learnt will lower the costs of the industrial processes involved.

Although corn-to-ethanol and other food stocks have implications both in terms of world food prices and limited, yet positive, energy yield (in terms of energy delivered to customer/fossil fuels used), the technology has led to the development of cellulosic ethanol. According to a joint research agenda conducted through the US Department of Energy, the fossil energy ratios (FER) for cellulosic ethanol, corn ethanol, and gasoline are 10.3, 1.36, and 0.81, respectively. [cellulose|Cellulosic biomass]], derived from non-food sources, such as trees and grasses, is also being developed as a feedstock for ethanol production.

Even dry ethanol has roughly one-third lower energy content per unit of volume compared to gasoline, so larger (therefore heavier) fuel tanks are required to travel the same distance, or more fuel stops are required.

other biofuel

Algae biofuels. Algae fuel is a biofuel that is derived from algae. The production of algae to harvest oil for biofuels has not yet been undertaken on a commercial scale. Algae potentially can be grown in environments such as algae ponds at wastewater treatment plants and the oil extracted from the algae and processed into biofuels. The benefits of algal biofuel are that it can be produced industrially, thereby obviating the use of arable land and food crops (such as soy, palm, and canola), and that it has a very high oil yield as compared to all other sources of biofuel. Thus, algaculture, unlike food crop-based biofuels, oes not entail a decrease in food production, since it requires neither farmland nor fresh water.

Jatropha. 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 (Divakara et al.).

Fungi

A group at the Russian Academy of Sciences in Moscow, in a 2008 paper, stated they had isolated large amounts of lipids from single-celled fungi and turned it into biofuels in an economically efficient manner. More research on this fungal species, Cunninghamella japonica, and others, is likely to appear in the near future. The recent discovery of a variant of the fungus Gliocladium roseum points toward the production of so-called myco-diesel from cellulose. This organism was recently discovered in the rainforests of northern Patagonia, and has the unique capability of converting cellulose into medium-length hydrocarbons typically found in diesel fuel.

Animal Gut Bacteria

Microbial gastrointestinal flora in a variety of animals have shown potential for the production of biofuels. Recent research has shown that TU-103, a strain of Clostridium bacteria found in Zebra feces, can convert nearly any form of cellulose into butanol fuel. Microbes in panda waste are being investigated for their use in creating biofuels from bamboo and other plant materials.

• Germany has built a 250 kilowatt synthetic methane plant which they are scaling up to 10 megawatts.

Waste

Waste-to-energy (WtE) or energy-from-waste (EfW) is the process of generating energy in the form of electricity and/or heat from the incineration of waste. WtE is a form of energy recovery. Most WtE processes produce electricity and/or heat directly through combustion, or produce a combustible fuel commodity, such as methane, methanol, ethanol or synthetic fuels.

Incineration, the combustion of organic material such as waste with energy recovery, is the most common WtE implementation. All new WtE plants in OECD countries incinerating waste (residual MSW, commercial, industrial or RDF) must meet strict emission standards, including those on nitrogen oxides (NO_x), sulphur dioxide (SO₂), heavy metals and dioxins. Hence, modern incineration plants are vastly different from old types, some of which neither recovered energy nor materials. Modern incinerators reduce the volume of the original waste by 95-96 percent, depending upon composition and degree of recovery of materials such as metals from the ash for recycling.

Incinerators may emit fine particulate, heavy metals, trace dioxin and acid gas, even though these emissions are relatively low from modern incinerators. Other concerns include proper management of residues: toxic fly ash, which must be handled in hazardous waste disposal installation as well as incinerator bottom ash (IBA), which must be reused properly.

Critics argue that incinerators destroy valuable resources and they may reduce incentives for recycling. The question, however, is an open one, as countries in Europe recycling the most (up to 70%) also incinerate their residual waste to avoid landfilling.

Incinerators have electric efficiencies of 14-28%. In order to avoid losing the rest of the energy, it can be used for e.g. district heating (cogeneration). The total efficiencies of cogeneration incinerators are typically higher than 80% (based on the lower heating value of the waste), and may even exceed 100% when equipped with flue gas condensation.

According to ISWA there are 431 WtE plants in Europe (2005) and 89 in the United States (2004). The following are some examples of WtE plants.

Biomass briquettes

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

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.

Hydrogen

Over $1 billion of federal money 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.

Lightning

Since the late 1980s, there have been several attempts to investigate the possibility of harvesting energy from lightning. It has been proposed that the energy contained in lightning be used to generate hydrogen from water, or to harness the energy from rapid heating of water due to lightning, or to use inductors spaced far enough away so that a safe fraction of the energy might be captured. In the summer of 2007, an alternative energy company called Alternate Energy Holdings, Inc. (AEHI) unsuccessfully tested a method for capturing the energy in lightning bolts.

History

Offshore wind turbines near Copenhagen

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

Historian Norman F. Cantor describes how in the late medieval period, coal was the new alternative fuel to save the society from overuse of the dominant fuel, wood:

"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 C.E. 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.

Alcohol 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.

Enabling technologies

Heat pumps and Thermal energy storage are technologies which use energy sources that normally can't be obtained. Also, heat pumps have the advantage of leveraging electrical power (or in some cases mechanical or thermal power) by using it to extract additional energy from a low quality source (such as sea or lake 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, which most of the heat collected in summer. 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.

Ecologically friendly alternatives

Renewable energy sources such as biomass are sometimes regarded as an alternative to ecologically harmful fossil fuels. Renewables are not inherently alternative energies for this purpose. 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 Template: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.

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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.

Biological Hydrogen Production

Hydrogen gas is a completely clean burning fuel; its only by-product is water. It also contains relatively high amount of energy compared with other fuels due to its chemical structure.

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 we could implement this on a large scale, then we could take sunlight, nutrients and water and create hydrogen gas to be used as a dense source of energy. Large-scale production has proven difficult. It was not until 1999 that we were able to even 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.

Investing in alternative energy

As an emerging economic sector, there are limited 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, such as Warren Buffett, 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%.^{[citation needed]} In general there are three subsegments of “alternative” energy investment: solar energy, wind energy and hybrid electric vehicles. Alternative energy sources which are renewable, free and have lower carbon emissions than what we have now are 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 5 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.^{[citation needed]} 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. Some of its key conclusions are shown here.

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 "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 main-stream there are a few crucial obstacles that it must overcome: First there must be increased understanding of how alternative energies work and why they are beneficial; secondly the availability components for these systems must increase; and lastly the pay-off time must be decreased.

For example, electric vehicles (EV) and Plug-in Hybrid Electric Vehicles (PHEV) are on the rise. These vehicles depend heavily on an effective charging infrastructure such as a smart grid infrastructure to be able to implement electricity as mainstream alternative energy for future transportations.

Alternative Energy Research

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.

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.

Disadvantages

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 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.

There are additional issues that may arise from switching to alternative energy. “Increasing the nation’s use of natural gas for electricity generation could result in adverse economic consequences”, especially since “natural gas currently costs about four times more than coal”. Furthermore, if there were a widespread switching to natural gas from coal some countries would become increasingly dependent on international supplies. Also, “large-scale fuel switching would require substantial investments in pipeline storage and storage capacity and new terminals to process imported natural gas”. There is also the question of whether to convert existing coal-burning plants or to construct new ones. “Burning natural gas at an existing coal plant would require a pipeline with the ability to meet the plant’s fuel supply requirements”. It would also require “expansion of interstate and intrastate pipelines to transport increased volumes of natural gas” Overall it would be more feasible and cost-effective to construct new natural gas units than to switch coal-burning plants.

References

ISBN links support NWE through referral fees

Much of this research focuses on improving the overall per acre oil yield of Jatropha through advancements in genetics, soil science, and horticultural practices.

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