翻译| 陈霞 审校|许少欢
Offshore wind turbines near Copenhagen
Alternative energy is any energy source that is an alternative to fossil fuel. These alternatives are intended to address concerns about such fossil fuels.
The nature of what constitutes an alternative energy source has changed considerably over time, as have controversies regarding energy use. Today, because of the variety of energy choices and differing goals of their advocates, defining some energy types as "alternative" is highly controversial.
In a general sense, alternative energy as it is currently conceived, is that which is produced or recovered without the undesirable consequences inherent in fossil fuel use,
particularly high carbon dioxide emissions, an important factor in global warming
2.1 Coal as an alternative to wood/煤炭替代木材
2.2 Petroleum as an alternative to whale oil/石油替代鲸油
2.3 Alcohol as an alternative to fossil fuels/乙醇替代化石燃料
2.4 Coal gasification as an alternative to petroleum/气化煤替代石油
3 Common types of alternative energy/常见的替代能源类型
4 Enabling technologies/使能技术
5 Renewable energy vs non-renewable energy/可再生能源与不可再生能源的竞争
5.1 Ecologically friendly alternatives/生态友好型替代能源
6 Relatively new concepts for alternative energy/关于替代能源的几个新概念
6.1 Carbon-neutral and negative fuels/碳中和以及负燃料
6.2 Algae fuel/藻类生质燃料
6.3 Biomass briquettes/生物质成型燃料
6.3.1 Biogas digestion/沼气发酵
6.4 Biological hydrogen production/生物制氢
6.5 Offshore wind/离岸风
6.6 Marine and hydrokinetic energy/海洋流体能源
7 Investing in alternative energy/对替代能源的投资
7.1 Alternative energy in transportation/替代能源在交通运输方面的应用
8 Making alternative energy mainstream/让替代能源成为主流
9.3 Ethanol biofuels/乙醇生物燃料
9.4 Other biofuels/其他生物燃料
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 煤炭替代木材
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 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 石油替代鲸油
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 Pennsylvaniain 1859.
Alcohol as an alternative to fossil fuels乙醇替代化石燃料
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.
1917年，Alexander Graham Bell提倡使用从玉米、小麦和其他农作物中提取的乙醇作为煤和石油的替代能源，并声称人类离化石燃料用尽的那一天已经不远了。在Bell看来，需要替代能源是因为现有的主要能源再生能力都不强。从20世纪70年代开始，巴西就制定了乙醇燃料项目，并成为仅次于美国的世界第二大乙醇生产国和世界上最大的乙醇出口国。在该项目中，巴西使用现代化的生产设备，将廉价的甘蔗作为原料，把剩下的甘蔗残渣用来供热和发电，此后，巴西的街道上再也没有完全依靠石油驱动的轻型车。到2008年底，巴西全国至少配有一个乙醇燃油加油泵的加油站已有35000家。
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 气化煤替代石油
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.
Common types of alternative energy常见的替代能源类型
• Solar energy is the use of sunlight. Light can be changed into thermal (heat) energy and electric energy.
• Wind energy is the generation of electricity from the wind.
• 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.
• Nuclear energy uses nuclear fission to release energy.
• Hydrogen can serve as a means of delivering energy produced by various technologies.
Enabling technologies 使能技术
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.
热能存储技术能够让温度在几天甚至几个月内保持不变，不论是保热还是保冷，而且还能储存显热（通过改变介质的温度）或潜热（通过改变物体的状态，也就是从固态向液态转变或逆向转换，比如说从水到冰水混合物或到冰）。能量来源可以是自然能源（通过太阳能集热板吸收热量或干式冷却塔来收集冬天的低温）和废料能源（比如来自暖通空调系统、工业生产过程或者发电厂）或者过剩能源（比如由于水力发电的季节性或风力发电的间歇性而产生的）。加拿大亚伯达省的Drake Landing 太阳能社区就是一个很好的例子。地孔热能存储器通过车库屋顶上的太阳能收集器为该社区提供一年中所需热量的97%，其中大部分热量都是在夏天收集的。存储器可以是保温储罐，以碎石子到基岩等各种石材为构成的钻孔群，或者排列整齐能够保温的浅坑。其中有些应用需要热泵技术。
Renewable energy vs non-renewable energy 可再生能源与不可再生能源的竞争
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 naturally basic processes. Wood, the most renewable and available alternative energy, burns the same amount of carbon it would emit if it degraded naturally.
Ecologically friendly alternatives生态友好型替代能源
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 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 关于替代能源的新概念
Carbon-neutral and negative fuels/碳中和以及负燃料
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.
冰岛格林达维克国际碳回收公司旗下的George Olah二氧化碳回收工厂从2001年起每年都能从Savrtsengi发电厂排放的废气中生产出200万升车用甲醇燃油，它的年产量可达到500万升。在德国的巴登-符腾堡州，由太阳能与氢能研究中心和弗劳恩•霍夫协会共同建造的一个250千瓦的甲醇合成燃料工厂在2010年开始生产，目前正在向千万瓦级扩建，预计将于2012年秋完成。奥迪公司也在德国的韦尔特建造了一家碳中和液化天然气厂，旨在生产出能够抵消它们的A3 Sportback g-tron型车所消耗的液化天然气的车用燃油，按照该工厂最初的生产力，它每年可减少2800公吨的二氧化碳排放量。在南卡罗莱纳州的哥伦比亚、加利福尼亚州的卡马利洛和英格兰的达林顿等地也出现了类似的加工工厂。
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 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. Germany has built a 250 kilowatt synthetic methane plant which they are scaling up to 10 megawatts.
Algae fuel 藻类生质燃料
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. 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.
Biomass briquettes 生物质成型燃料
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 生物制氢
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
2H 2 + O 2 → 2H 2 O + 高能量
高能量 + 2H 2 O → 2H 2 + O 2
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.
Offshore wind 离岸风
Offshore wind farms are similar to regular wind farms, but are located in 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 a great deal of 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 海洋流体能源
Marine and Hydrokinetic (MHK) or marine energy development in U.S. and international waters includes projects using the following devices:
• Wave energy converters in open coastal areas with significant waves;宽阔近海大风地区的风能转换器
• Tidal turbines placed in coastal and estuarine areas;江河入海口的潮汐涡轮机
• In-stream turbines in fast-moving rivers;流速较快水域中的水下汽轮机
• Ocean current turbines in areas of strong marine currents;洋流强烈水域的洋流涡轮机
• Ocean Thermal Energy Converters in deep tropical waters.赤道深水区的海洋热能转换器
Investing in alternative energy 对替代能源的投资
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, 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 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. 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替代能源在交通运输方面的应用
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.
比如说，尼桑美国首次批量生产了电动汽车“尼桑聆风”； 一款可充电混合动力车—“雪佛兰- Volt”也已经被研发出来，该车使用电动马达驱动，配有一个小型四汽缸引擎来产生额外的电能。
Making alternative energy mainstream 让替代能源成为主流
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.
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.
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