• Opening Keynote – Dr. Matthew Ganz
• Session 1: Biomass Cultivation and Conversion
• Session 2: Alternative Auxiliary Power technologies
• Session 3: Technical Impacts of Alternative Fuels
• Session 4: Economic Impacts
• Session 5: Enivronmental Impacts
• Session 6: Policy and Legislation Panel Discussion

More information: http://www.sae.org/events/aafs/

A typical ‘lifter’ design.

When a current passes between two electrodes — one thinner than the other — it creates a wind in the air between. If enough voltage is applied, the resulting wind can produce a thrust without the help of motors or fuel.

This phenomenon, called electrohydrodynamic thrust — or, more colloquially, “ionic wind” — was first identified in the early 20th century. Since then, ionic wind has largely been limited to science-fair projects and basement experiments; hobbyists have posted hundreds of how-to videos on building “ionocrafts” — lightweight vehicles made of balsa wood, aluminum foil and wire — that lift off and hover with increased voltage.

Despite this wealth of hobbyist information, there have been few rigorous studies of ionic wind as a viable propulsion system. Some researchers have theorized that ionic thrusters, if used as jet propulsion, would be extremely inefficient, requiring massive amounts of electricity to produce enough thrust to propel a vehicle.

Now researchers at MIT have run their own experiments and found that ionic thrusters may be a far more efficient source of propulsion than conventional jet engines. In their experiments, they found that ionic wind produces 110 newtons of thrust per kilowatt, compared with a jet engine’s 2 newtons per kilowatt. The team has published its results in the Proceedings of the Royal Society.

Steven Barrett, an assistant professor of aeronautics and astronautics at MIT, envisions that ionic wind may be used as a propulsion system for small, lightweight aircraft. In addition to their relatively high efficiency, ionic thrusters are silent, and invisible in infrared, as they give off no heat — ideal traits, he says, for a surveillance vehicle.

Shooting the gap

A basic ionic thruster consists of three parts: a very thin copper electrode, called an emitter; a thicker tube of aluminum, known as a collector; and the air gap in between. A lightweight frame typically supports the wires, which connect to an electrical power source. As voltage is applied, the field gradient strips away electrons from nearby air molecules. These newly ionized molecules are strongly repelled by the corona wire, and strongly attracted to the collector. As this cloud of ions moves toward the collector, it collides with surrounding neutral air molecules, pushing them along and creating a wind, or thrust.

To measure an ion thruster’s efficiency, Barrett and Masuyama built a similarly simple setup, and hung the contraption under a suspended digital scale. They applied tens of thousands of volts, creating enough current draw to power an incandescent light bulb. They altered the distance between the electrodes, and recorded the thrust as the device lifted off the ground. Barrett says that the device was most efficient at producing lower thrust — a desirable, albeit counterintuitive, result.

“It’s kind of surprising, but if you have a high-velocity jet, you leave in your wake a load of wasted kinetic energy,” Barrett explains. “So you want as low-velocity a jet as you can, while still producing enough thrust.” He adds that an ionic wind is a good way to produce a low-velocity jet over a large area.

Getting to liftoff

Barrett acknowledges that there is one big obstacle to ionic wind propulsion: thrust density, or the amount of thrust produced per given area. Ionic thrusters depend on the wind produced between electrodes; the larger the space between electrodes, the stronger the thrust produced. That means lifting a small aircraft and its electrical power supply would require a very large air gap. Barrett envisions that electrodynamic thrusters for aircraft — if they worked — would encompass the entire vehicle.

Another drawback is the voltage needed to get a vehicle off the ground: Small, lightweight balsa models require several kilovolts. Barrett estimates a small craft, with onboard instrumentation and a power supply, would need hundreds or thousands of kilovolts.

“The voltages could get enormous,” Barrett says. “But I think that’s a challenge that’s probably solvable.” For example, he says power might be supplied by lightweight solar panels or fuel cells. Barrett says ionic thrusters might also prove useful in quieter cooling systems for laptops.

Ned Allen, chief scientist and senior fellow at Lockheed Martin Corp., says that while ionic thrusters face serious drawbacks — particularly for aerospace applications — the technology “offers nearly miraculous potential.”

“[Electrohydrodynamic thrust] is capable of a much higher efficiency than any combustion reaction device, such as a rocket or jet thrust-production device,” Allen says. Partly for this reason, Allen says Lockheed Martin is looking into the technology as a potential means of propulsion.

“Efficiency is probably the number one thing overall that drives aircraft design,” Barrett says. “[Ionic thrusters] are viable insofar as they are efficient. There are still unanswered questions, but because they seem so efficient, it’s definitely worth investigating further.”

(Jennifer Chu, MIT News Office)

See further coverage at:

• MIT News
• Quirks and Quarks (CBC radio interview) (mp3 file)
• Popular Mechanics
• Bloomberg Businessweek
• The Verge
• Gizmodo
• redOrbit
• Engineering and Technology Magazine
• VR-Zone
• TG Daily
• Txchnologist
• Discovery News
• DPA Magazine
• EV News
• Earth Techling
• Gizmag

The original research article is at Proceedings of the Royal Society A.

The school, which will focus on solar geoengineering, is open to graduate students, post-doctoral fellows, and recently appointed faculty and researchers working in any applicable discipline. The number of participants is limited to 80.  To apply, please submit a short letter (300 words or less) covering your research interests and an explanation of relevance of this summer school to your research. We request a short letter of recommendation from applicants who have not attended a previous geoengineering summer school and whose research is in the early stages (that is Master’s students and PhD candidates in their 1st or 2nd years).

Cost

The summer school will cost $300 USD. This includes shared accommodation, all lunches and a banquet dinner.  Single accommodation will be available at a first-come-first serve basis for an additional $21/night. Please indicate on your application if you would like a single room.  Cost of travel is the responsibility of participants. Some scholarships will be available for participants who would otherwise not be able to attend, and a request for support should accompany the application in such circumstances.

Application deadline

The US Department of State advises that visa applicants from many countries must now apply 3–4 months in advance of their travel date. Please check the U.S.Department of State website for information about travel to the USA and to verify whether you require a visa.  Due to processing times there is an early application deadline for those who need visas of 18 April 2013. The general application deadline is 01 May 2013.

Please contact Hollie Roberts with any questions (hroberts@seas.harvard.edu).

Further information about 16.715.

New MIT graduate level course 16.715 Transportation and the Environment is being introduced this spring term. The course considers the impacts of emissions from aviation, shipping, road and rail on cimate, air quality, human health and noise. Mitigation approaches across technology, biofuels, policy and operational improvements are covered.

The course is taught by LAE’s Professor Steven Barrett with LAE PhD candidates Fabio Caiazzo and Akshay Ashok as teaching assistants.

The dataset was generated using the Aviation Emissions Inventory Code (AEIC). AEIC is an open source emissions inventory tool that has been under development for the last three years, initially at the University of Cambridge for aircraft landing and takeoff emissions, and then at MIT for full-flight emissions. A brief overview of AEIC and more details on the emissions dataset are available in lab report LAE-2012-012-N. The landing and takeoff emissions portion of the code was described in Atmospheric Environment in 2011. A publication and release of the full-flight emissions code is planned for early 2013.

Planes await takeoff at London’s Heathrow Airport

According to the U.K.’s Department for Transport, demand for air travel in the country will more than double by 2030, from 127 million to 300 million passengers per year. A debate over how to accommodate this rising demand has revolved around two main proposals: adding a third runway to London’s Heathrow Airport, or replacing Heathrow with a new airport in the Thames Estuary. Over the years, concerns over cost and environmental impacts have fueled both sides of the debate.

Now a study evaluating the health impacts associated with the two proposals finds that a new hub on the Thames Estuary may be the better option.

The study, published this week in the journal Atmospheric Environment, has found that by 2030, an expanded Heathrow would add 100 early deaths from air pollution annually in the U.K. Compared with the expanded Heathrow scenario, a new airport on the Thames Estuary would cause 60 to 70 percent fewer premature deaths.

Steven Barrett, an assistant professor of aeronautics and astronautics at MIT, says the numbers make sense from a geographic perspective.

“Heathrow is almost in the worst possible place because it’s in the middle of this populated area, and upwind of it,” says Barrett, the study’s lead author and director of the Laboratory for Aviation and the Environment at MIT. “The pollution from an airport [in the Thames] would just blow over the North Sea.”

The findings are part of a wider assessment the team conducted on the health impacts of the U.K.’s 20 busiest airports. To determine the number of premature deaths from airport-related emissions, the team first tracked the number of flights coming in and out of each airport, using 2005 to represent the present day. The researchers also obtained projections from the Department for Transport of the number of flights expected in 2030 under scenarios where Heathrow is and is not expanded.

For each scenario, the team developed a model, detailed in a previous paper, to estimate emissions from aircraft, as well as ground support vehicles such as trolleys and tractors. The team then used a model called Weather Research and Forecasting to simulate wind patterns and other atmospheric conditions throughout the country. They plugged the aircraft emissions data into the model to see where the winds carried the pollution, and then used a simulation of chemical reactions in the atmosphere to understand conversion of emissions into fine particles. Finally, the group superimposed the fine-particulate data over population-density maps in the country.

Previous epidemiological studies have determined the health risk associated with long-term exposure to given concentrations of fine particulate matter. Barrett and his colleagues applied the health-risk data to their fine-particulate map to determine the number of premature deaths caused by a given airport scenario.

In a present-day scenario in which Heathrow operates under current demands, the researchers found the airport-related emissions cause 50 premature deaths throughout the U.K. If Heathrow undergoes no expansion, the number of early deaths would increase to 110 by the year 2030, possibly as a result of other U.K. airports expanding to meet growing demand.

If officials decide to expand Heathrow, adding a third runway, the study projected, the resulting air pollution would cause 150 early deaths annually; a new replacement airport on the Thames Estuary would drop that number to 50, as any emissions created by the new hub would be carried across the English Channel, away from population centers.

Barrett says there are several factors the group did not account for in evaluating a Thames Estuary scenario. For example, if a new airport were built, populations might grow around that airport, while traffic around a retired Heathrow might decrease, creating less pollution around London (and more to the west). Barrett says that overall it is not clear if these additional factors would increase or decrease the relative benefits of the Thames Estuary option, but thinks these will be smaller than the effect of moving aircraft.

“Even by expanding the hub airport’s capacity and moving it, you would cause fewer deaths than not expanding the hub and leaving it where it is,” Barrett says. “When you look at the results, they’re environmentally quite interesting.”

The team also found that the number of early deaths in all scenarios would decrease if airports adopted several key mitigation measures: removing sulfur from jet fuel, using one engine instead of two to taxi, converting ground transportation to electric power, and using preconditioned air from the airport terminal to cool aircraft cabins when their engines are off.

“If the cost was no object, and the air quality and health impacts were the priority, then clearly the Thames airport would make more sense,” Barrett says. “But obviously, it would cost a lot of money. If people decided to do this, it would be a very long process.”

(Jennifer Chu, MIT News Office)

LAE director Professor Steven Barrett met with the each of the students listened to their presentations on biofuels and answered questions about the lab’s work with alternative fuels. The students also met earlier in the day with program sponsor, AeroAstro Professor and Associate Provost Wesley Harris.  The curriculum was designed to introduce the students to modern themes in aerospace research and to inspire students to pursue engineering majors at university.

The AeroAstro MOSTEC group in summer 2012 with Prof. Steven Barrett. (Photo: Jon Gibbs)

The researchers analyzed data from 2005, the most recent year for which information is available. They found that among the various sources of emissions in the country, car and truck exhaust was the single greatest contributor to premature death, affecting some 3,300 people per year. By comparison, the researchers note, fewer than 3,000 Britons died in road accidents in 2005.

The researchers found that emissions originating elsewhere in Europe cause an additional 6,000 early deaths in the U.K. annually; U.K. emissions that migrate outside the country, in turn, cause 3,100 premature deaths per year in other European Union nations. In some areas on the periphery of the U.K. — such as northern Scotland — almost all air pollution comes from the rest of Europe, the researchers say.

MIT’s Steven Barrett and his co-author Steve Yim began the study in light of recent events in the U.K.: London is currently in violation of air quality standards set by the E.U., and the British government may face significant E.U. fines if it fails to address its air pollution.

“We wanted to know if the responsibility to maintain air quality was matched by an ability to act or do something about it,” says Barrett, the Charles Stark Draper Assistant Professor of Aeronautics and Astronautics at MIT. “The results of the study indicate there is an asymmetry there.”

Dust in the wind

Barrett worked with MIT postdoc Steve Yim to analyze emissions data provided by the British government. The team divided the country’s emissions into sectors, including road transport; power generation; commercial, residential and agricultural sources; and other transport, such as shipping and aviation.

The group then simulated temperature and wind fields throughout the country using a weather research and forecasting model similar to those used to predict short-term weather. Barrett and Yim entered emissions data into the model to see how weather might disperse the emissions. They then ran another simulation — a chemistry transport model — to see how emissions from different sectors interacted.

Finally, the group overlaid their simulation results on population density maps to see which locations had the greatest long-term exposure to combustion emissions. Barrett observed that most of the emissions studied were composed of particles less than 2.5 microns in diameter, a size that epidemiologists have associated with premature death.

Hazy outlook

After road transport, the researchers found that emissions from shipping and aviation were the second greatest contributor to premature deaths, causing 1,800 early deaths annually, followed by powerplant emissions, which cause an estimated 1,700 premature deaths each year.

Barrett and Yim found that powerplant emissions have larger health impacts in northern England, where emissions from five major plants tend to congregate. In London, the researchers found that shipping and aviation emissions had a greater impact on health, possibly due to the proximity of major airports to the city.

Emissions from the country’s powerplants, which are mostly northeast of major cities and emit pollution well above ground level, are less damaging to the general population than other sources of pollution, Barrett says. In contrast, he says emissions from cars and trucks, which occur closer to where people live and work, pose a more serious risk to human health.

“People have a number of risk factors in their life,” Barrett says. “Air pollution is another risk factor. And it can be significant, especially for people who live in cities.”

Fintan Hurley, scientific director of the Institute of Occupational Medicine in Edinburgh, Scotland, says the group’s findings provide a detailed analysis of the sources of air pollution in the country. Hurley led a similar study by the Committee on the Medical Effects of Air Pollution, and says Barrett’s results are in line with that analysis. The implications, he adds, go beyond Britain’s borders.

“It’s helpful to have a detailed analysis of effects in the U.K., but outdoor air pollution from combustion sources is an important public health issue worldwide,” Hurley says. “With outdoor air pollution everybody is exposed, because fine particles and gases also penetrate indoors. It’s possible for individuals to do some things to limit their personal exposures, but the main need is to act together to reduce emissions.”

(Jennifer Chu, MIT News Office)

See further coverage at:

• MIT News
• BBC News
• Daily Mail
• Medical Daily
• The Telegraph
• The Guardian
• The Financial Times
• The Scotsman
• NERC Planet Earth Online
• Forbes
• CNN

The original research article is available at DOI: 10.1021/es2040416.

Warmer colors indicate locations of warming caused by desulfurizing jet fuel related to the reduction of scattering sulfate particles from the atmosphere.

A new MIT-led study has been released that assesses the economic and environmental costs and benefits of desulfurizing jet fuel.

Aircraft emissions can reduce air quality, leading to adverse health impacts including increased risk of premature mortality. A technically viable way to mitigate the health impacts of aviation is the use of desulfurized jet fuel, as has been done with road transportation in many jurisdictions. To attain levels of 15 ppm – a measure of the sulfur concentration in fuel – from the current average levels of 400-800 ppm would increase the cost of jet fuel by 1.6-6.6 ¢/gal, i.e. an increase in the cost of a gallon of just over 1% at 2011 prices.

Although the environmental implications are complex, the MIT-led research indicates transitioning to an ultra-low sulfur jet fuel is likely to prevent 1000-4000 premature mortalities per year (if implemented globally), but may increase globally averaged climate warming caused by aviation by 1-8%.

Commercial aviation fuel (Jet A/A-1) contains sulfur at concentrations of 400-800 ppm, although there is significant variation. By contrast, US road transportation fuel is subject to an ultra-low sulfur fuel standard of 15 ppm, which is about 97% less than jet fuel. Other jurisdictions including Australia, Canada, New Zealand, Mexico, Japan, India, Argentina, Brazil, Chile, Peru and the European Union have instituted similar standards for road transportation. Marine fuels are being subjected to increasingly stringent standards too, but marine bunker fuels have higher sulfur content than aviation or road transportation fuels.

Sulfur in fuel results in the emission of SOx (sulfur oxides) upon combustion. SOx is predominantly a gas when emitted, but gets converted in the atmosphere to a form of fine particulate matter (i.e. small particles) called sulfate. Sulfate particles predominantly scatter solar radiation, some of it back into space, therefore offsetting a fraction of global warming, although whether this is climatically beneficial or not is a subject of continuing research. A second important effect of SOx emissions is to increase the amount of fine particles that people inhale. There has been substantial quantitative evidence collected over decades that links human exposure to fine particulate matter to an increased risk of premature mortality and other adverse health effects. Finally, SOx emissions result in acid rain and associated damages.

Jet fuel can be desulfurized in the same way as road transportation fuels. Jet fuel is chemically very similar to diesel and there are no significant technical challenges in doing this, although a corrosion inhibitor/lubricity improver (CI/LI) may need to be added to the resultant fuel in order to prevent excessive component wear within engine fuel pumps. This is done routinely in the military and the cost is negligible compared to the cost of desulfurization. This hydrodesulfurization process will increase the cost of fuel by just over 1% at present-day prices, which maps to an industry total $1.3-3.8bn per year (in 2006 US$) if implemented globally, or $0.5-1.4bn per year for the US alone.

The dominant adverse environmental result of desulfurization is that removing sulfur from fuel results in increased CO2 emissions because hydrodesulfurization involves the release of relatively small amounts of CO2 and consumes additional energy. A second potentially adverse effect is that the reflection of solar radiation into space by sulfate particles would be reduced. In combination, these are estimated to increase the globally-averaged climate warming caused by the production and use of a gallon of jet fuel by 1-8% if it is desulfurized.

See further coverage by:

• Chemistry World
• Fuel Handler Magazine

The original research article is available at DOI: 10.1021/es203325a. The research is also available as PARTNER report PARTNER-COE-2011-006.

However, researchers at MIT say the industry may want to cool its jets and make sure it has examined biofuels’ complete carbon footprint before making an all-out push. They say that when a biofuel’s origins are factored in — for example, taking into account whether the fuel is made from palm oil grown in a clear-cut rainforest — conventional fossil fuels may sometimes be the “greener” choice.

“What we found was that technologies that look very promising could also result in high emissions, if done improperly,” says James Hileman, principal research engineer in the Department of Aeronautics and Astronautics, who has published the results of a study conducted with MIT graduate students Russell Stratton and Hsin Min Wong in the online version of the journal Environmental Science and Technology. “You can’t simply say a biofuel is good or bad — it depends on how it’s produced and processed, and that’s part of the debate that hasn’t been brought forward.”

Hileman and his team performed a life-cycle analysis of 14 fuel sources, including conventional petroleum-based jet fuel and “drop-in” biofuels: alternatives that can directly replace conventional fuels with little or no change to existing infrastructure or vehicles. In a previous report for the Federal Aviation Administration’s Partnership for Air Transportation Noise and Emissions Reduction, they calculated the emissions throughout the life cycle of a biofuel, “from well to wake” — from acquiring the biomass to transporting it to converting it to fuel, as well as its combustion.

“All those processes require energy,” Hileman says, “and that ends up in the release of carbon dioxide.”

In the current Environmental Science and Technology paper, Hileman considered the entire biofuel life cycle of diesel engine fuel compared with jet fuel, and found that changing key parameters can dramatically change the total greenhouse gas emissions from a given biofuel.

Land-locked

In particular, the team found that emissions varied widely depending on the type of land used to grow biofuel components such as soy, palm and rapeseed. For example, Hileman and his team calculated that biofuels derived from palm oil emitted 55 times more carbon dioxide if the palm oil came from a plantation located in a converted rainforest rather than a previously cleared area. Depending on the type of land used, biofuels could ultimately emit 10 times more carbon dioxide than conventional fuel.

“Severe cases of land-use change could make coal-to-liquid fuels look green,” says Hileman, noting that by conventional standards, “coal-to-liquid is not a green option.”

Hileman says the airline industry needs to account for such scenarios when thinking about how to scale up biofuel production. The problem, he says, is not so much the technology to convert biofuels: Companies like Choren and Rentech have successfully built small-scale biofuel production facilities and are looking to expand in the near future. Rather, Hileman says the challenge is in allocating large swaths of land to cultivate enough biomass, in a sustainable fashion, to feed the growing demand for biofuels.

He says one solution to the land-use problem may be to explore crops like algae and salicornia that don’t require deforestation or fertile soil to grow. Scientists are exploring these as a fuel source, particularly since they also do not require fresh water.

Feeding the tank

Total emissions from biofuel production may also be mitigated by a biofuel’s byproducts. For example, the process of converting jatropha to biofuel also yields solid biomass: For every kilogram of jatropha oil produced, 0.8 kilograms of meal, 1.1 kilograms of shells and 1.7 kilograms of husks are created. These co-products could be used to produce electricity, for animal feed or as fertilizer. Hileman says that this is a great example of how co-products can have a large impact on the carbon dioxide emissions of a fuel.

Hileman says his analysis is one lens through which policymakers can view biofuel production. In making decisions on how to build infrastructure and resources to support a larger biofuel economy, he says researchers also need to look at the biofuel life cycle in terms of cost and yield.

“We need to have fuels that can be made at an economical price, and at large quantity,” Hileman says. “Greenhouse gases [are] just part of the equation, and there’s a lot of interesting work going on in this field.”

The study is the culmination of four years of research by Hileman, Stratton and Wong. The work was funded by the Federal Aviation Administration and Air Force Research Labs.

(Jennifer Chu, MIT News Office)

The original research article is available at DOI: 10.1021/es102597f.