Study examines commercial hybrid-electric aircraft, reduced carbon emissions

Study examines commercial hybrid-electric aircraft, reduced carbon emissions
The study includes a map of the US with values by state of how much carbon is produced per unit of energy. Credit: University of Illinois Department of Aerospace Engineering

Although we're still a long way from commercial airplanes powered by a combination of fossil fuel and batteries, a recent feasibility study at the University of Illinois explored fuel/battery configurations and the energy lifecycle to learn the tradeoffs needed to yield the greatest reductions in carbon dioxide emissions.

"In the energy supply chain there's a phrase, from 'well to wake.' That is, production begins at the oil well and ends at the wake of the airplane. Tracking costs and environmental implications across this entire lifecycle is important, because the implications for fuel and energy production can be substantially different, depending on the source. In this study, we looked at how technologies need to improve to make a hybridized configuration feasible, where feasibility is assessed based on a need to meet a certain range requirement and feature a large reduction in emissions. The net carbon emissions were calculated from a combination of fuel burn and the carbon impact associated with recharging the batteries," said Phillip Ansell, assistant professor in the Department of Aerospace Engineering in the College of Engineering at the U of I.

According to Ansell, that second part has been ignored.

"You can get a fuel burn reduction, but if the cleanliness of the electrical grid that's being used to charge the is not included, you're missing a significant part of the carbon emissions total," he said.

The study compared the relative CO2 emissions produced per kilowatt-hour for each individual state across the United States. It includes a map of the U.S. with values of how much carbon is produced per unit of energy.

But, to be commercially acceptable, a hybrid-electric aircraft needs to be able to carry the same number of passengers and travel the same distances as current all-fossil fuel aircraft do, so the study used the parameters for a single-aisle airplane that can carry approximately 140 passengers as a model. They parametrically varied the proportion of power across the propulsion driveshaft that was electrically derived, using configurations where 12.5 percent, 25 percent, or 50 percent of the necessary power was produced by an electric motor. The study didn't consider cost in dollars, but rather the cost in CO2 emissions—the environmental cost.

The most feasible configuration from the model was a propulsion system that uses a 50 percent electrical-power drivetrain and a specific energy density of 1,000 watt-hours per kilogram. This configuration was estimated to produce 49.6 percent less lifecycle CO2 emissions than a modern conventional aircraft with a maximum range equivalent to that of the average of all global flights, making it a viable option for environmentally responsible aviation. However, current battery technologies are quite far from being able to achieve this configuration. Despite this fact, Ansell did say that improvements in batteries will continue to provide gains in capabilities.

"Obviously, the 12.5 percent is the most near-term accessible configuration that was studied, because we'll need less battery technology progress to get to that point. However, we also see a non-linear relationship between CO2 emissions produced and improvements in hybrid-electric propulsion concepts, where the most rapid proportional reductions in are produced across near-term improvements in technology," Ansell said. "Achieving the technology improvements for a 50% hybrid system certainly has a very long timetable to get to market, by a long shot, because it's entirely uncertain if or when that level of energy density of batteries will be manufactured. But at least in the interim, even small gains in component technologies can make a big difference."

When will technology be able to manufacture a battery lightweight enough yet powerful enough to fly a commercial airplane?

Ansell speculated, "Perhaps in the next 10 years we'll be able to have a battery that is 400 to 600 watt-hours per kilogram. If we project that out, the levels that we need for larger hybridization factors, or even fully electric commercial aircraft, might be within reach in the next 25 years."

The study, "Mission Analysis and Emissions for Conventional and Hybrid-Electric Commercial Transport Aircraft," was authored by Gabrielle E. Wroblewski and Phillip J. Ansell. It appears in the Journal of Aircraft.


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More information: Gabrielle E. Wroblewski et al, Mission Analysis and Emissions for Conventional and Hybrid-Electric Commercial Transport Aircraft, Journal of Aircraft (2019). DOI: 10.2514/1.C035070
Citation: Study examines commercial hybrid-electric aircraft, reduced carbon emissions (2019, March 25) retrieved 16 June 2019 from https://phys.org/news/2019-03-commercial-hybrid-electric-aircraft-carbon-emissions.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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Mar 25, 2019
Seems like biofuels would be a much better answer to reducing carbon footprint for aircraft for the foreseeable future. Batteries have quite a ways to go before they can supplant aviation fuel.

Mar 25, 2019
Energy beaming would also allow the aircraft to be powered by electricity for the takeoff portion and use the traditional fuel for cruising, without adding tons of batteries that are only useful during takeoff.

Mar 25, 2019
Well, jetplanes are suppose to make air travel faster & more profitable for heavily taxpayer subsidized manufacturers & airlines & airports.

So why do the disembarking passengers resemble refugees from a death march?

Let's be honest about this.
(yes I already feel the hate boiling off of you for forcing you to confront the facts)

This is all about feeding the gluttony of the military-industrial complex. The need to maintain large pools of experienced air & ground crews, who like to pretend they are not conscripts for the rest of their lives. Dispersal of military & support resources.. Spreading the opportunities for kickbacks, payola & under-the-table campaign contributions to as many Congressional Districts as possible. & even to places that are totally stupid to have a factory or airfield.

A reasonable, conservative airline betwork would have slower, less fuel-hogging turbo-props servicing modest-priced tickets to a larger number of smaller, convenient airports.

Mar 25, 2019
High speed electric trains: no batteries required.

Mar 25, 2019
Trains do have the problem of right-of-way.
When you sell your land-rights to the Supertrain Conglomerate?
Tell me, you are not going to squeeze every dime out of them? You & you alone, insist your property is worth?
Now try & repeat that with a straight face this time...

There are two reasons we wound up with the National Highway Trust/Civil Defence projects.
The second was Eisenhower seeing how airpower in The European Theater of WWII was able to cripple the railroads.

First reason? Ikes personal experiences in 1920?
Leading a USArmy experimental truck column across the United States from the East Coast to the West Coast.
& all the problems they encountered with getting supplies & fuel deposited along the route by the railroads.

I suppose if we stuck with a Nationalized Train System from the beginning. Avoiding National Turnpikes?
Perhaps a modernized railroad network might make sense?

But it would have resulted in a very different America!

Mar 26, 2019
"You can get a fuel burn reduction, but if the cleanliness of the electrical grid that's being used to charge the battery system is not included, you're missing a significant part of the carbon emissions total,"
Solar and wind are a joke at recharging electric cars, just imagine recharging aircraft.
"How many solar panels does it take to fill up a hydrogen car? To generate the electricity needed to fill one Mirai every day would take 2,858 square feet of solar panels – in sunny Phoenix. In other parts of the country it could take twice as much."
https://www.treeh...car.html
"Tesla Factory Store Uses Diesel Generators to Recharge Slow-moving Model 3 Inventory"- Mar 14, 2019
https://4k4oijnpi...re-2.jpg
https://wattsupwi...ventory/

Mar 26, 2019
Seems like biofuels would be a much better answer to reducing carbon footprint...
"Biomass: Not Carbon Neutral and Often Not Clean"
https://www.nrdc....ot-clean
"Biomass More Polluting Than Coal, New Study Finds"
https://www.ecowa...699.html
"Biodiesel: cure worse than the disease"
https://pbs.twimg...QYZp.jpg
Biofuels, wind and solar, are land-intensive, trillion-dollar fiascos at reducing emissions, they cause more ecological impacts/environmental damages than reduce emissions, they should be excluded from the tools against Climate Change.

"With Ethanol And Biomass No Longer Viewed As "Green," Will Other Renewables Soon Follow?"
https://www.forbe...-follow/
In a world of limited hydro, carbon-free nuclear is the only way to go.

Mar 26, 2019
Seems like biofuels would be a much better answer to reducing carbon footprint for aircraft for the foreseeable future.

Biofuels bring with them all the ancillary issues of burning fossil fuels at high altitude (besides CO2)

Batteries have quite a ways to go before they can supplant aviation fuel.

If fluoride batteries pan out I think we'll be there faster than anyone is expecting.

Aviation is one of the few areas where I'd even see hydrogen fuel cells as a viable way to go (at least for now). Airports can afford centralized production, storage and fueling infrastructure. Even though the efficiency of H2 is no better than fossil fuel engines (well-to-wheel) it would get rid of the CO2 issue.

Mar 26, 2019
Ao, weewilliewart. How many avgas stations/refineries are overhead?
That civil aircraft enroute may pull over to conveniently
"fill her up!" a few miles in the sky?

Except of course for USAF/AG tankers.
I can hear you whining already about the taxes you do not pay, since you are a useless, unproductive child of affluenza.

Just try to imagine the ticket prices you would have to pay?
To fly a civil airline that relied upon mid-air flight refueling tankers!

Now you got something to whine about!

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