EVs are touted as
the future of cars but that future is not set in stone. Costs and reliability
are current concerns but those will likely improve over time. One wildcard that
could upend that future is groundbreaking improvement in internal combustion
engines coming to fruition. It is still up in the air whether that will happen,
but efficiency improvements continue, and new engine designs are taking shape
and being tested. Some older designs are being revisited as well.
Opposed Piston Engines
The opposed
piston engine is an example of an old design being revisited. These have been
around for a century. They have mostly been used in tanks, ships, trains, and submarines,
but many think they can be adapted for road vehicles. It has no valves or
cylinder heads. It is a two-stroke engine. It is more efficient and offers
lower fuel costs and fewer emissions. A 1930s plane with an opposed piston
engine could go 6000 miles on a tank of fuel. A Top Speed article from October
2023 notes:
“Achates Power, the leading developer of OP engines, aims
to license its technology to automakers and has already achieved success with
engine debuts on a Ford F-150 and a Peterbilt tractor. However, the main
challenge lies in changing people's perceptions of two-stroke engines and
gaining mainstream acceptance.”
The OP engine retains heat, enough to ignite the fuel mixture
so no spark plugs are needed. In a 2021 webinar organized by Calstart, Achates
claimed that its engines can produce 65 percent lower NOx emissions than the
standard set by the California Air Resources Board for 2027. They estimate that
trucks with OP engines can save 20-28.5 % in fuel costs. Achates did a 2018
test of OP technology with Ford. Cummins is building an advanced combat OP
engine for the U.S. military with Achates technology. Achates’s goal is to have
OP engines for sale in 2027. The technology is hoped to compete with EVs as a lower
emissions vehicle. It is expected to be cheaper to build and with fewer parts
than a conventional four-stroke ICE vehicle.
Toyota’s Next-Gen Combustion Engines
Toyota has been at the forefront of increasing
ICE efficiency in recent years. Toyota released engines in 2018 with 40%
thermal efficiency. An article in Slash Gear gives some context about their
successful focus on hybrids and plug-in hybrids as well as their new more
efficient hybrid engines they plan to put in production in a couple years.
“The company's internal documents illuminate its 1:6:90
rule, which states that the same amount of raw material used to generate one
fully electric vehicle can be used to make six plug-in hybrids or as many as 90
hybrid cars. Besides the smaller requirement for raw materials, Toyota
estimates that these 90 hybrid cars combined offset 37 times the carbon
emissions than a single EV.”
That means that 37 times more emissions can be offset with
hybrids than for EVs with a similar amount of raw materials? I’m not sure of
the details or implications here but it would seem that this advocates for
hybrids and plug-in hybrids as better for emissions per raw materials used.
“Studies substantiate this argument to some extent,
indicating that a mid-size hybrid has a lower lifecycle carbon footprint than a
compact EV when driven for 150,000 miles, owing to the energy-intensive battery
production process. Despite criticism, Toyota and its sister companies, Mazda
and Subaru, uphold their commitment to ICEs. They have pledged to continue
investing and working together in fuel-based technology, a move that would also
benefit hundreds of suppliers struggling with the shift to electric vehicles.
With the challenges of lagging charging infrastructure and the high cost of EVs
in mind, Toyota is banking on rising demand for fuel-efficient ICEs, especially
hybrids.”
Toyota’s new
hybrid engines are lighter, 10-20% smaller with comparable power to regular ICE
engines, and up to 30% greater efficiency. Again, Slash Gear explains:
“These improvements are achieved by implementing a
shorter piston stroke. The shorter piston strokes result in decreased torque,
which is compensated for by the electric motor. This approach enhances
efficiency by reducing the maximum RPM these newer engines can make. Smaller
piston strokes, leading to compact engines, can allow for lowered front hoods.
This, in turn, would improve aerodynamics, reduce the center of gravity, and
minimize cabin vibrations. Toyota is expected to commence the production of these
engines in 2026, ...”
Toyota’s new
hybrid engines can run on diesel, gasoline, synthetic e-fuels, and hydrogen.
With hydrogen, they can achieve 50% efficiency. I believe they can run on blends
of fuel as well. The video below shows the engine versions and their
capabilities.
Astron Aerospace Develops New High-Efficiency ICE
Engines
I wrote
about Astron Aerospace’s Omega 1 prototype engine in my 2022 book, Natural Gas
and Decarbonization. I will reproduce that section below. The company’s latest
version of an automobile engine has changed a bit, running on hydrogen and
offering 60% efficiency, better than hydrogen fuel cells. Apparently, I was
right in my estimation from a few years ago about 60% efficiency.
Astron Aerospace’s Omega 1 Internal Combustion Active
Linear Engine
This new internal
combustion engine design is exciting to read and hear about, but it is still in the early stages, with only a functional prototype so far. Indications thus far are
that it will be cost-competitive, much more fuel efficient and produce less
emissions, and high performance. The new engine design was invented by a
veteran of the aerospace industry and is expected to focus first on aerospace
applications. It is the world’s first engine with an active linear power
transfer. Power is transferred through the single rotating shaft. There is no
offset crankshaft, eccentric shaft, or reciprocating pistons. It comes with “a
pre-chamber, connected to a pair of chambers, that separates cold intake air
from exhaust gas, removing the issue of exhaust gas overlap.” They expect
to produce a small-scale model in a couple of years. It has several advantages
over current ICE engines: a simplified design, air-cooled, and superior
efficiency due to less losses from friction, pumping, and other parasitic
losses. It is touted as “more powerful, lighter, efficient, and simpler than
a turbine engine.” Cost may be an issue for its automotive adoption but
eventually, it may be competitive. An automotive single-engine version is
expected to weigh just 35lbs, have 160 horsepower and, 170lbs of torque, and have
as many parts as a lawnmower engine. Oil changes are expected to have a
50,000-mile interval with maintenance costs much lower. The design can be
scaled in a stacked manner with potential to be used for many applications. The
design can be tweaked to run on any fuel including diesel, gasoline, biofuels, natural
gas, propane, and hydrogen. Running on hydrogen, it could outcompete fuel cells
for use in long-haul trucking. Materials used directly affect cost so the
better aerospace versions with materials like titanium will have better
performance. Combustion improvements decrease pollutants. The prototype is
called Omega 1, with planned stages up to Omega 5. I have not seen numbers on comparative
emissions or fuel efficiency, but it is reputed to be theoretically capable of
80% thermal efficiency, which is a big gain over the 20-30% average. Toyota
released engines in 2018 with 40% thermal efficiency, so my rough guess is that
the automotive version could have 60%. Astron notes: “A large improvement in
combustion and overall efficiency comes from the forced air supercharged intake
at between 200 and 300 psi.” It has less friction and less parasitic heat
and pumping losses compared to a piston engine. It has a “skip-fire” capability
that also increases efficiency so that firing rates decrease when not
accelerating. If the design succeeds it could make ICE vehicles less emitting
and less costly to run and maintain. Time will tell. It could also be used as a
range extender for an EV, running on hydrogen perhaps.
Astron Aerospace’s New 60% Efficiency, Zero Emissions
Hydrogen ICE Engine: H2 Starfire
The Omega 1 has
apparently been superseded by Astron’s new H2 Starfire hydrogen ICE engine that
achieves 60% efficiency with zero combustion emissions. An article in
Interesting Engineering gives some details about the H2 Starfire:
“Astron’s H2Starfire achieves these using two sets of
counter-rotating rotors: one aluminum half does the intake and compression
jobs, while the titanium half at the rear handles expansion and exhaust.”
“Inside the engine, temperatures reach 1,400 Fahrenheit
(760 degrees Celsius), and here, hydrogen can burn cleanly to produce energy,
noise, and mechanical vibrations that motorheads fear they will miss.”
“The company claims it has achieved another major
milestone by eliminating the need for water cooling. This has also helped it
reduce the complexity of its design and weight, which gives it an efficiency
boost.”
“H2Starfire’s design is quite linear and avoids the use
of apex seals. The company claims that the engine is frictionless, and its
tolerances are so tight that only timing gears and bearings need oiling. This
has been achieved with a simplistic design of the engine, which consists of
only 82 parts.”
The H2 Starfire cut
the number of parts from 114 in the Omega 1 to 82 parts. A single H2 Starfire
engine weighs 120 lbs., and produces 400 horsepower and 500 lb-ft of torque. It measures
11.4 x 12.5 x 17.3 inches, making it very compact. Astron claims that the H2
Starfire can compete at one-fourth the cost of hydrogen fuel cells or EV
batteries. While this is great news, I am still not sure of the
commercialization timeline for this engine or if it has technological hurdles
yet to overcome. The video below gives more details.
Hydrogen ICE Retrofits and Newbuilds for Long-Haul
Trucking
Companies such as
Volvo and MAN are developing hydrogen ICE retrofits for long-haul trucks. These
include replacing the conventional ICE engine with a hydrogen ICE engine. The
cost of these is expected to be below that of hydrogen fuel cells. Reuter
reported in August that:
“In its first pilot project, MAN will deliver around 200
trucks with engines that run on hydrogen to European customers next year to
test in their fleets, a key step on the way towards mass production.”
Volvo plans to
test their hydrogen combustion engines in 2026. Both companies will continue to
build hydrogen fuel cell trucks as well. Westport Fuel Systems provided fuel
systems for 6000 ICE trucks in Europe that run on natural gas that can later be
converted to run on hydrogen. Many of these engines can run on diesel, then be
converted to natural gas when it is more available, then be converted to hydrogen
when it becomes more available and decarbonized, whether blue hydrogen made
from natural gas with carbon capture or green hydrogen from electrolysis of
water.
Hydrogen
vehicles also need pressurized fuel tanks that are larger than diesel tanks.
These can be included with new vehicles or retrofitted. Getting them to fit can
be a challenge. However, that problem is being addressed, partially by changing
the shape of the tanks.
References:
Your
Next Green Car May Run on Gas and Get 100 Miles to the Gallon. David H.
Freedman. Newsweek. September 11, 2023. Your Next Green Car May Run on Gas
and Get 100 Miles to the Gallon (msn.com)
Weight,
Efficiency, and Environment. Astron Aerospace.
A New
Internal Combustion Engine Produces Nearly Zero Harmful Emissions. Chris Young.
Interesting Engineering. January 28, 2022.
Savior
Of Internal Combustion: Here’s Why Opposed-Piston Engines Are Becoming Popular
Again. Moses Karomo. Top Speed. October 4, 2023. Savior Of Internal Combustion: Here’s
Why Opposed-Piston Engines Are Becoming Popular Again (msn.com)
Opposed
Piston Engines: What To Know About The Crazy New Configuration. Michael De Kock.
Hot Cars. September 2023. Opposed Piston Engines: What To Know
About The Crazy New Configuration (msn.com)
Thermal Efficiency Of Diesel Engines Explained: Why It's Important. Joe Capraro. Slash Gear. May 2024. Thermal pend thast future Efficiency Of Diesel Engines Explained: Why It's Important (msn.com)
Everything
We Know So Far About Toyota's Game-Changing Next-Gen Combustion Engines. Top
Speed. July 25, 2024. Everything We Know So Far About
Toyota's Game-Changing Next-Gen Combustion Engines (msn.com)
Everything
We Know About The New Combustion Engines Toyota's Working To Release Soon. Tushar
Mehta. Slash Gear. August 11, 2024. Everything We Know About The New
Combustion Engines Toyota's Working To Release Soon (msn.com)
Truck
makers look toward hydrogen to keep old combustion engines on the road:
'Everybody is working on this'. Stephen Proctor. The Cool Down, August 30,
2024. Truck makers look toward hydrogen to
keep old combustion engines on the road: 'Everybody is working on this'
(msn.com)
The H2
Starfire Engine May Be the Most Promising Disruptor in The EV Industry. Top
Speed. September 8, 2024. The H2 Starfire Engine May Be The
Most Promising Disruptor In The EV Industry (msn.com)
Astron’s
hydrogen engine achieves record 60% efficiency with 0 emissions. Ameya Paleja.
Interesting Engineering. August 26, 2024. Astron’s
hydrogen engine achieves record 60% efficiency with 0 emissions (msn.com)
The
Future of Driving Is Here: E-Fuels vs. EVs. José Bossellini. Tork US. August 30,
2024. The
Future of Driving Is Here: E-Fuels vs. EVs (msn.com)
Big
truckmakers bet on hydrogen to extend combustion engine life. Christina Amann
and Nick Carey. Reuters. August 1, 2024. Big
truckmakers bet on hydrogen to extend combustion engine life | Reuters
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