Why Aren’t There Electric Airplanes Yet?
DuKai Photographer / Moment / Getty Images
By Venkat Viswanathan, Shashank Sripad and William Leif Fredericks
As electric cars and trucks appear increasingly on U.S. highways, it raises the question: When will commercially viable electric vehicles take to the skies? There are a number of ambitious efforts to build electric-powered airplanes, including regional jets and planes that can cover longer distances. Electrification is starting to enable a type of air travel that many have been hoping for, but haven't seen yet—a flying car.
A key challenge in building electric aircraft involves how much energy can be stored in a given amount of weight of the on-board energy source. Although the best batteries store about 40 times less energy per unit of weight than jet fuel, a greater share of their energy is available to drive motion. Ultimately, for a given weight, jet fuel contains about 14 times more usable energy than a state-of-the-art lithium-ion battery.
That makes batteries relatively heavy for aviation. Airline companies are already worried about weight—imposing fees on luggage in part to limit how much planes have to carry. Road vehicles can handle heavier batteries, but there are similar concerns. Our research group has analyzed the weight-energy tradeoff in electric pickup trucks and tractor-trailer or semi-trucks.
This artist's concept of NASA's experimental electric plane design shows 14 motors along the wings. NASA
From Electric Trucks to Flying Vehicles
We based our research on a very accurate description of the energy required to move the vehicle along with details of the underlying chemical processes involved in Li-ion batteries. We found that an electric semi-truck similar to today's diesel-powered ones could be designed to travel up to 500 miles on a single charge while being able to carry the cargo of about 93 percent of all freight trips.
Flying vehicles are a bit further away, because they have different power needs, especially during taking off and landing.
What is an e-VTOL?
Unlike passenger planes, small battery-powered drones that carry personal packages over short distances, while flying below 400 feet, are already coming into use. But carrying people and luggage requires 10 times as much energy—or more.
We looked at how much energy a small battery-powered aircraft capable of vertical takeoff and landing would need. These are typically designed to launch straight up like helicopters, shift to a more efficient airplane mode by rotating their propellers or entire wings during flight, then transition back to helicopter mode for landing. They could be an efficient and economic way to navigate busy urban areas, avoiding clogged roads.
Energy Requirements of e-VTOL Aircraft
Our research group has built a computer model that calculates the power needed for a single-passenger e-VTOL along the lines of designs that are already under development. One such example is an e-VTOL that weighs 1,000 kilograms, including the passenger.
The longest part of the trip, cruising in airplane mode, needs the least energy per mile. Our sample e-VTOL would need about 400 to 500 watt-hours per mile, around the same amount of energy an electric pickup truck would need—and about twice the energy consumption of an electric passenger sedan.
However, takeoff and landing require much more power. Regardless of how far an e-VTOL travels, our analysis predicts takeoff and landing combined will require between 8,000 and 10,000 watt-hours per trip. This is about half the energy available in most compact electric cars, like a Nissan Leaf.
For an entire flight, with the best batteries available today, we calculated that a single-passenger e-VTOL designed to carry a person 20 miles or less would require about 800 to 900 watt-hours per mile. That's about half the amount of energy as a semi-truck, which is not very efficient: If you needed to make a quick visit to shop in a nearby town, you wouldn't hop into the cab of a fully loaded tractor-trailer to get there.
As batteries improve over the next few years, they may be able to pack in about 50 percent more energy for the same battery weight. That would help make e-VTOLS more viable for short- and medium-range trips. But, there are a few more things needed before people can really start using e-VTOLS regularly.
It's Not Just Energy
For ground vehicles, determining the useful range of travel is enough—but not for planes and helicopters. Aircraft designers also need to closely examine the power—or how quickly the stored energy is available. This is important because ramping up to take off in a jet or pushing down against gravity in a helicopter takes much more power than turning the wheels of a car or truck.
Therefore, e-VTOL batteries must be able to discharge at rates roughly 10 times faster than the batteries in electric road vehicles. When batteries discharge more quickly, they get a lot hotter. Just as your laptop fan spins up to full speed when you try to stream a TV show while playing a game and downloading a large file, a vehicle battery pack needs to be cooled down even faster whenever it is asked to produce more power.
Road vehicles' batteries don't heat up nearly as much while driving, so they can be cooled by the air passing by or with simple coolants. An e-VTOL taxi, however, would generate an enormous amount of heat on takeoff that would take a long time to cool—and on short trips might not even fully cool down before heating up again on landing. Relative to the battery pack size, for the same distance traveled, the amount of heat generated by an e-VTOL battery during takeoff and landing is far more than electric cars and semi-trucks.
That extra heat will shorten e-VTOL batteries' useful lives, and possibly make them more susceptible to catching fire. To preserve both reliability and safety, electric aircraft will need specialized cooling systems—which would require more energy and weight.
This is a crucial difference between electric road vehicles and electric aircraft: Designers of trucks and cars don't have any need to radically improve either their power output or their cooling systems, because that would add cost without helping performance. Only specialized research will find these vital advances for electric aircraft.
Our next research topic will continue to explore ways to improve e-VTOL battery and cooling system requirements to provide enough energy for useful range and enough power for takeoff and landing—all without overheating.
Reposted with permission from our media associate The Conversation.
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By Karen Charman
When President Donald Trump visited California on September 14 and dismissed the state Secretary of Natural Resources Wade Crowfoot's plea to recognize the role of climate change in the midst of the Golden State's worst and most dangerous recorded fire season to date, he gaslighted the tens of millions of West Coast residents suffering through the ordeal.
Foxes Guarding the Henhouse<p>Before he assumed power, Trump attacked regulations as unnecessary barriers to freedom and economic prosperity. Since taking office, he has targeted anything enacted by the administration of his predecessor, Barack Obama, and taken steps to withdraw the U.S. from the Paris agreement, the international effort to combat climate change. He has also staffed heads of key agencies with climate deniers of various stripes, forced out career public servants and created a hostile work environment for those who don't profess loyalty to his deregulatory agenda.</p><p>Like Trump himself, some of his cabinet choices displayed an audacious penchant for <a href="https://www.nytimes.com/interactive/2020/09/27/us/donald-trump-taxes.html?action=click&module=Spotlight&pgtype=Homepage" target="_blank">self-dealing</a> and abusing their positions of authority. One example is Trump's first Environmental Protection Agency (EPA) Administrator, Scott Pruitt, who aggressively worked to overturn Obama's climate regulations, spent most of his time in <a href="https://www.washingtonpost.com/national/health-science/trump-epa-head-steps-down-after-wave-of-ethics-management-scandals/2018/07/05/39f4251a-6813-11e8-bea7-c8eb28bc52b1_story.html" target="_blank" rel="noopener noreferrer">private meetings</a> with fossil fuel and chemical company executives, sidelined career EPA staff and reconfigured independent scientific advisory boards to make them more supportive of the industries EPA is charged with regulating. Dubbed "<a href="https://www.latimes.com/politics/la-na-pol-pruitt-leaves-20180705-story.html" target="_blank" rel="noopener noreferrer">one of the most scandal-plagued Cabinet officials in U.S. history</a>," Pruitt resigned in disgrace after revelations about his multiple brazen abuses, including using the agency as his personal concierge service and piggy bank.</p><p>Pruitt's deputy, Andrew Wheeler, a <a href="https://www.cbsnews.com/news/andrew-wheeler-acting-epa-administrator-former-number-two-before-scott-pruitt-resignation/" target="_blank">former coal industry lobbyist</a> and longtime Republican Washington insider, took over and has continued Trump's deregulatory agenda apace.</p><p>At the Department of Interior (DOI), a sprawling agency that oversees 75 percent of the country's public federal lands and includes the U.S. Geological Survey, which is tasked with evaluating natural hazards that threaten life and the health of our ecosystems, Trump installed another flamboyant anti-environmentalist to head the agency. Like Pruitt, Trump's first Interior Secretary Ryan Zinke aggressively attacked environmental regulations, <a href="https://www.washingtonpost.com/news/energy-environment/wp/2017/05/07/epa-dismisses-half-of-its-scientific-advisers-on-key-board-citing-clean-break-with-obama-administration/" target="_blank">ditched more than 200 advisory panels</a>, and pushed to open up vast swaths of public land to oil and gas drilling. Described by one environmental group as "<a href="https://www.washingtonpost.com/national/health-science/interior-secretary-zinke-resigns-amid-investigations/2018/12/15/481f9104-0077-11e9-ad40-cdfd0e0dd65a_story.html" target="_blank" rel="noopener noreferrer">the most anti-conservation Interior secretary in our nation's history</a>," Zinke was forced out after numerous highly publicized conflict-of-interest scandals.</p><p>The DOI is now run by Zinke's deputy secretary, David Bernhardt, another longtime Republican Washington insider and former oil industry lobbyist who has also been the subject of <a href="https://slate.com/news-and-politics/2020/05/this-is-still-happening-david-bernhardt-trump-lincoln.html" target="_blank">several government ethics complaints</a> for various violations favoring polluting industries.</p><p>More recently, longtime climate change denier David Legates, a climatologist at the University of Delaware previously <a href="https://insideclimatenews.org/news/19032015/u-delaware-refuses-disclose-funding-sources-its-climate-contrarian" target="_blank">funded by fossil fuel interests</a>, was hired for a <a href="https://www.npr.org/2020/09/12/912301325/longtime-climate-science-denier-hired-at-noaa" target="_blank" rel="noopener noreferrer">top job</a> advancing weather modeling and prediction at the National Oceanic and Atmospheric Administration (NOAA). Legates has called for <a href="https://www.democracynow.org/2020/9/18/noaa_david_legates_climate_crisis" target="_blank" rel="noopener noreferrer">increasing carbon emissions</a>.</p><p>The Trump administration has done much more than stack government agencies with fossil fuel industry proponents. It has removed or diluted discussion of climate change from as many government platforms as it can and decimated independent scientific advisory boards that provide unbiased, fact-based information the government needs to enact policies that protect the public. It has also <a href="https://thehill.com/policy/energy-environment/482352-trump-budget-slashes-funding-for-epa-environmental-programs" target="_blank" rel="noopener noreferrer">slashed environmental agency staffing and budgets</a>.</p>
The Damage So Far<p>A September 17 <a href="https://rhg.com/research/the-rollback-of-us-climate-policy/" target="_blank">report</a> by the Rhodium Group calculates that 1.8 billion tons more greenhouse gases will be released over the next 15 years as a result of climate change rollbacks the Trump administration has achieved so far. These include repealing Obama's main climate policy, the Clean Power Plan, which was intended to reduce dirty emissions from power plants; increasing pollution from cars by rolling back fuel economy standards and challenging California's longtime authority to set stricter emissions standards; targeting controls on hydrofluorocarbons, powerful greenhouse gases used mainly in refrigerators and air conditioners that also destroy the Earth's protective ozone layer; and allowing unreported and unregulated emissions of methane, another potent greenhouse gas, by oil and gas companies.</p><p>Besides these measures, Trump is also trying to gut core environmental statutes like the Clean Air Act, the Clean Water Act, the National Environmental Policy Act and the Endangered Species Act, all of which were enacted to protect human health and preserve a livable world.</p><p>The Paris agreement aims to keep the rise in average global temperatures at less than 2 degrees Celsius above pre-industrial levels and hopefully cap it at 1.5 degrees C or lower. We are now at approximately 1.2 degrees C and counting.</p>
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By Jan Ellen Spiegel
It wasn't so long ago that the issue of climate change was poised to play a huge – possibly even a decisive – role in the 2020 election, especially in the race for control of the U.S. Senate. Many people supporting Democratic candidates saw a possible Democratic majority as a hedge against a potential Trump re-election … a way to plug the firehose spray of more than 100 environmental regulation rollbacks and new anti-climate initiatives by the administration over its first term.
Potential Climate Voters<p>In a September 1 memo on climate and the election, Andrew Baumann, vice president of the consultants Global Strategy Group, wrote: "Few issues have seen as dramatic a shift in public opinion as climate change has over the last few years. Only marriage equality and the recent shift in views around racial justice outpace the rapid growth in the salience of climate change as an issue."</p><p>Calling it a "winning political issue" the memo says: "First, it is clearly a motivator for both younger and Latinx voters. Second, it has the power to move swing voters, particularly center-right white women."</p><p>Baumann points to a finding that when a group of such women were asked generic ballot questions, Democrats trailed by nine percentage points. But when the question was revised as a choice between:</p><p>"A Democrat who supports taking strong government action to combat climate change.<br>A Republican who opposes taking strong government action to combat climate change."</p><p>… the result was a 29 percentage point shift, putting Democrats ahead by 20 percentage points among that same group.</p><p>"I think it is playing a role," says Senator Sheldon Whitehouse, D-RI, a longtime outspoken climate activist who is on the Senate Environment and Public Works Committee and also on the Senate Democrats' Special Committee on the Climate Crisis. If Democrats win back the Senate, he stands to play an even more pivotal climate role as part of the majority. He is not up for re-election this year.</p><p><span></span>"I think from the Democratic side it's playing a role in generating enthusiasm – particularly making younger voters feel that they have a real stake in this election. On the Republican side, I think things have moved enough that candidates can no longer get away with simply scoffing about climate change."</p>
Climate a Top Concern for Youths, Latinx<p>So who's still thinking climate? Mostly young voters – 18 to 25 or 29 and Latinx voters.</p><p>Climate and the environment are the top concern among young voters, just above racism and healthcare according to <a href="https://circle.tufts.edu/latest-research/poll-young-people-believe-they-can-lead-change-unprecedented-election-cycle" target="_blank" rel="noopener noreferrer">CIRCLE</a>, the Center for Information and Research on Civic Learning and Engagement at Tufts University, which focuses on the political life of young people in the U.S. For Latinx youth, it drops a bit but remains in the top three.</p><p>The issues young people care about have an impact on how they volunteer their time, says Kristian Lundberg, an associate researcher at CIRCLE. He says that's played out most notably through the Sunrise Movement, which focuses on climate change and the environment along with other key activist groups such as Black Lives Matter and March for Our Lives.</p><p>He points to polling this summer that showed that 83% of 18-to-29-year-olds felt they had the power to change things. "Young people feel much more empowerment than in 2016 and 2018," Lundberg says. "It's intentional these movements are carving out space for young people. It's an important strategy."</p><p>In positions of power in these organizations, young people have developed peer-to-peer outreach on activism. And Lundberg says young people have made the leap that connects activism to voting as a lever for change. "In the past in very close races, young people breaking heavily have provided the margin of victory," he says.</p><p>CIRCLE is highlighting 10 U.S. Senate races as ones in which young voters can be decisive. Several of them have notable climate or environmental components – most prominently the Colorado and Montana races.</p><p>The Republican incumbents in each state – Cory Gardner in Colorado and Steve Daines in Montana – are running against a popular Democratic governor – John Hickenlooper in Colorado, now out of office — and Steve Bullock, still the governor of Montana. Both governors have had to balance their state's fossil fuel economic interests with supporting climate change solutions.</p>
Tying Climate Change to the Economy<p>In August, Data for Progress, a progressive research think tank, released polling on climate change – including in the battleground Senate elections in Arizona, Iowa, Maine, and North Carolina – showing voters back a Senate candidate supporting strong climate action.</p><blockquote>Climate change as 'mobilizing issue … key persuasion issue.'<br></blockquote><p>It also showed that linking climate change to the economy may be key. That means talking about clean energy and jobs together, says Danielle Deiseroth, climate data analyst for <a href="https://circle.tufts.edu/latest-research/poll-young-people-believe-they-can-lead-change-unprecedented-election-cycle" target="_blank">Data for Progress</a>. She says that in addition to jobs, climate change issues include climate justice and economic equality – both of heightened interest because of fallout from western wildfires.</p><p>"Climate change, we've observed over the last year or so, is a key mobilizing issue and a key persuasion issue," she says. "Climate issues can only grow support for Democratic candidates.</p><p>"I think it's pretty naive to say climate is the key issue for voters. For a lot of voters it really exemplifies so many things that are wrong with the Trump presidency," Deiseroth says.</p><p>So a factor among others. Helpful, but pivotal only in narrow circumstances.</p><p>At the League of Conservations Voters, a progressive environmentalist organization putting a lot of money and effort into the 2020 races, Senior Director of Political Affairs Craig Auster says: "I'll push back that climate change doesn't matter or isn't registering."</p><p>"It's still showing up in several Senate races. It's been playing a role in almost all of them."</p><p>Candidates are still talking about it, he says, pointing to Colorado, Montana, Iowa, and other states where ads are addressing climate and environmental issues. That shows the candidates believe their opponent is vulnerable on the issue or they're strong on it, he says.</p><p>Like others, Auster calls climate a motivator.</p><p>"Climate change matters," he says. "We have proof point after proof point about what's happening, whether it's a hurricane, a superstorm, derechos in Iowa, or wildfires out west.</p><p>"Pre-COVID it was top tier for Democratic voters along with healthcare. If COVID didn't happen I think climate would be a big deal."</p>
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