Hyliion acquired the Karno generator technology from GE Additive in August 2022 to employ as a fuel-agnostic power system on its Hypertruck platform, which was revealed as a demonstration vehicle at the Advanced Clean Transportation (ACT) Expo in Anaheim, California, in May 2023. What a difference a half-year makes.

The Austin, Texas-based company changed its vehicle-propulsion strategic focus in October 2023 to concentrate solely on stationary power generation applications. “This is a solution that we see being able to solve distributed power generation, where you make your own electricity onsite and reduce your dependency on the grid,” Hyliion founder and CEO Thomas Healy said in mid-December during a virtual “tech fireside chat.”

“We do still have the Hypertruck technology, but we’ve put that on the shelf and saved it for later,” he said, adding that the company will continue to evaluate the market for opportunities to bring the Karno generator back into the vehicle space “when the time is right.” He cited the marine and freight-rail sectors as other use cases that could be explored in the future.

“A lot of locomotives today are using diesel gensets that convert [diesel fuel] into electricity, and then it’s an actual electric-drive locomotive,” Healy said. “A lot of those players have also started experimenting with hydrogen and fuel cells. We see the Karno as a way where you could make a fuel-agnostic locomotive and power that off hydrogen, natural gas, diesel or whatever fuel is available in that area.”

The unit reportedly can operate on more than 20 different fuels including ammonia, which is gaining significant interest in the shipping industry.

“When we say ‘fuel agnostic,’ we mean part-number identical,” said Chief Technology Officer Josh Mook, who also participated in Hyliion’s virtual event to detail how the generator works and to present a side-by-side performance comparison of the Karno and a conventional diesel engine. “More typically when people refer to fuel-agnostic, they say the [engine] block is agnostic [but] you need to go replace the head and the valvetrain and all these other components. That is not our case. We really can handle most of that in software by optimizing the fueling schedules and everything to accommodate the different gases.”

Healy added that although some competitors say they can run on hydrogen, it may only be up to a certain percentage. “That’s not the case for the Karno. We can run one-hundred percent hydrogen,” he said.

EV charging and other opportunities
Hyliion also hit pause on further development and commercialization of its Hypertruck ERX renewable natural gas (RNG) electric range extender, which received CARB certification as near-zero emission vehicle (NZEV) technology, due to slower-than-anticipated market adoption of electric trucks. One challenge limiting quicker adoption is the EV charging infrastructure, an area that can benefit from the Karno generator, according to Healy.

“EV charging, we see as a great opportunity,” Healy said, noting plans to start customer deployments of Karno in the second half of 2024.

“They’re trying to go out and deploy 50 EV charging pedestals; they’re going to their utility provider and their utility’s telling them, ‘Come back in three years and maybe we can give you a grid interconnect,’” Healy said. “Or there was another instance where the utility just flat out said, ‘Until we start building more power plants, we are not going to have the capability of putting an EV charging site at your location.’ These are some of the pain points that EV charging sites are facing.”

“They’re looking at Karno as a way to not only deploy the EV charging setup faster – because you’re [essentially] just bringing your own power plant and putting it on site – but also offer the ability to be fuel-flexible as well as have a very high efficiency level and lower costs of electricity generation in most instances,” Healy added.

Prime power is another “massive market opportunity,” Healy said. Hospitals, hotels and warehouses, for example, can use the Karno generator as a primary power source and the grid becomes the backup power supply.

Peak shaving presents another opportunity. “Throughout the day, your power consumption fluctuates – in a facility, at your house. In some instances, utilities will charge you more for when you’re consuming more power,” Healy said. “Peak shaving allows you to offset that and keep your power consumption that you’re pulling from the grid more steady.”

“It’s very different than a diesel genset, which you’re only going to really use if the grid’s down and you need backup power – the maintenance, the cost associated with those gensets just don’t bode well for prime power,” Healy continued. “With the Karno, it’s more the opposite; we think you should be running it continuously.”

In October 2023, Hyliion announced that its Karno generator achieved successful grid matching in Ohio, a key step in validating the technology’s capability in grid-tied applications, Healy said. During continued testing, Hyliion says it has demonstrated a distributed grid model, where the Karno generator interfaces seamlessly with the grid, matching voltage, frequency and power factor.

How it works
The Karno is a linear heat generator that is nothing like an internal-combustion engine, Healy stressed: “It has superior efficiency. We’re getting near powerplant-level efficiency out of this small generator that would normally take hundreds of acres out of a powerplant.”

The system is made up of four major components: the linear motor, a compression space, an expansion space, and the reactor. Inside of the linear motor is a shaft that rides on air bearings – similar to how a puck floats along the top of an air-hockey table, Healy said. The shaft oscillates back and forth to create the electricity.

“To make that movement, we expand and contract a sealed gas inside of the system. We do that through the compression and expansion spaces,” Mook said. The reactor is where the fuel and air come together and react using a proprietary flameless oxidation process. “That heat is captured by our hot side and transferred into the system,” he said. “We’re putting about 4,000 pounds of linear force in there to move [the shaft] to the other side.”

In one of Hyliion’s test areas, the experts demonstrated the flameless oxidation process using natural gas. “You can see all the metal components around are glowing orange because they’re so hot, but because of that unique flameless oxidation process, you really can’t see a flame,” Healy said, which contributes to lower emissions.

“Another interesting observation versus an internal combustion engine is you’ll notice this process is continuous and complete,” Mook added. “It’s not a series of explosions like you would normally see [with] internal combustion.” Running the process using a conventional fuel like diesel is very similar to running natural gas, according to Mook: “You’re seeing a very clean flame with minimal soot and particulate, which just shows the cleanliness of this system.”

Enhanced durability and lower maintenance costs are other reported benefits of the system design. Karno will operate for about 20,000 hours before requiring an overhaul, compared to a few thousand hours for an internal-combustion system, according to Mook. “This genset has no oils, no lubricants and it’s really designed to deploy it and then forget about it,” Healy added.

The Karno consists of four shafts, each providing about 50 kW of power output. The rough dimensions of the 200-kW unit, which also includes DC to AC converters as well as fans and radiator setup, is roughly 8-ft by 6-ft and 2-ft wide, according to Healy.

“Today we have these 200-kilowatt ‘building blocks,’ is the way I think about it,” Mook said. “We assemble those together into essentially whatever power level that the application would call for. We’re very excited about the scalability of the system.”

Healy said that Hyliion’s roadmap could include a two megawatt-plus unit, which would be about the size of a 20-foot shipping container. “You would have a bunch of those shafts on the inside and then combine together the radiator fan cooling-loop system, versus in the 200-kilowatt boxes [in which] you have independent cooling loops per each four-shaft setup,” he said.

Future developments also could include different shaft sizes. “We do see an opportunity moving to 10- to 25-kilowatt, more like a household generator size unit,” Healy said. “People like the idea of not buying a generator for outside your house that only gets used a couple hours a year – [instead] buy a generator that becomes prime power and now the grid is your backup.”

For production units deployed later in 2024, Hyliion plans to design and build the entire linear generator system in-house; the current system demonstrated in the Hypertruck Karno vehicle at ACT Expo features a linear motor from UK-based Libertine. “That will give us the ability to not only own the technology around the linear generator, but also to have those three elements – the chiller, the heater and the reactor – all be Hyliion components as well,” Healy said.

Karno vs. ICE and fuel cells
Mook mentioned that the Karno generator could use other sources of heat to produce electricity, including nuclear, geothermal or solar. This capability contributes to the “future-proof” nature of the system, he said.

“We often talk about fuel as a source of heat, and that’s because in the infrastructure that we mostly have, that’s the most practical,” he said. “The system won’t know the difference between heat entering that comes from nuclear versus heat entering that comes from fuel and a chemical release.”

The reactor is the only part of the system that would need to change depending on the heat source, Healy added. “The heater, the chiller, the actual genset, that can all stay the same because that sealed middle section, all it needs is heat coming in and that’s what’s going to make the electricity,” Healy said.

Hyliion quotes about a 50% efficiency for its Karno generator converting the BTUs of a fuel or energy source into electricity. “If you think about traditional diesel generators, it’s not atypical that you’ll see half of that relative to our system,” Mook said. “It’s a tremendous step change that really moves the needle on things like operating costs and fuel usage, as well as emissions.”

Healy responded to a question regarding the minimum and maximum load for the Karno compared to about 30% to 80% for conventional generators. “If you think about the normal efficiency of an internal-combustion engine, there’s a sweet spot that you would want to operate it in where you’re going to get most efficient use of the fuel,” he said. “We’re saying 40 to 100 percent would be where you’re getting a pretty flat efficiency band with the Karno. This is great for applications where you might have oscillating power levels; now you’re not giving up a lot of efficiency if you need to change how much power you need.”

The Karno holds an advantage in this regard compared to fuel cells as well, according to Healy.

“Fuel cells can have a very high peak efficiency, actually very comparable to our peak efficiency, but then as you get into high power levels, it falls off a cliff,” Healy said. “What fuel-cell providers are saying is, ‘Hey, you’re going to want to operate this around 60 percent power, so size the amount of fuel cells you need so that you’re only running them at 60 percent power.’ The problem with that is that becomes very costly. We’re quoting a 200-kilowatt generator and we’re telling customers, ‘You can really run this thing at 200 kilowatts.’ "