The internal combustion engine in its modern form has been around for more than 150 years. It’s a mature technology that treads the path of the traditional S curve. Which means that for some time now, companies have been spending billions of dollars for minor increases in performance. LiquidPiston, on the other hand, has decided to approach the problem from a completely different standpoint. Says co-founder and CEO Alec Shkolnik: “We decided to start with a brand-new thermodynamic cycle. We’ve gone right back to the physics of how the engine operates, and we are already demonstrating efficiencies that are better than state-of-the-art engines.” Rather than follow the curve, Shkolnik and LiquidPiston have chosen to disrupt it.
When you add those three features together—high compression, constant volume combustion, and overexpansion—it gives you a thermodynamic efficiency of 75 percent, which is 30 percent higher than the theoretical limits of today’s diesel and Otto cycles.
Their new High Efficiency Hybrid Cycle (HEHC) is the foundation on which their technology is built. “We call it the hybrid cycle because we’re optimizing the thermodynamic cycle for efficiency by combining features of existing cycles, essentially cherry picking the best parts of each one.” Like the highly-efficient diesel engine, the LiquidPiston cycle compresses air to a very high ratio, which increases the pressure and generates more energy than a gasoline engine. However, unlike the diesel engine, in which fuel is added while the piston is moving, leading to loss of potential efficiency, LiquidPiston adds fuel, mixing and burning while holding the volume effectively constant, yielding higher pressures and higher thermodynamic-efficiency—which is similar to the ideal Otto cycle. Like the Atkinson cycle, they continue the expansion process beyond the initial compression process. “When you add those three features together—high compression, constant volume combustion, and overexpansion—it gives you a thermodynamic efficiency of 75 percent, which is 30 percent higher than the theoretical limits of today’s diesel and Otto cycles,” says Shkolnik. Born out of what is now called the MIT $100K Entrepreneurship Competition, LiquidPiston maintains deep ties to the Institute. “That competition helped catalyze and launch this company,” he says. They’ve also been beneficiaries of the MIT Venture Mentoring Service. Now, as inductees into MIT STEX 25, Shkolnik is particularly appreciative of the role MIT and the Industrial Liaison Program have played in the development of his company. “Working closely with ILP, we’ve been able to develop relationships with partners that we would not have been able to connect with otherwise. It’s been extremely helpful for us as we look to expand our influence.” Based on their reimagining of the thermodynamic cycle, Shkolnik and LiquidPiston have rethought everything about how the engine operates and have 45 patents issued or pending internationally. But they have really come into their own with the design of what they’re calling the X Engine. Shkolnik explains that they homed in on rotary engines due to their inherent flexibility. One type of rotary engine, the Wankel engine as it is often called, has garnered a cult following of sorts for its simplicity, elegance, and power. However, the old rotary engines suffered from problems related to sealing, lubrication, cooling, emissions, durability, and efficiency. LiquidPiston’s X Engine, however, solves those problems. By turning the old Wankel rotary engine inside out, they have developed a quiet, powerful engine that is optimized for efficiency.
LiquidPiston currently has $9 million in government contracts through DARPA and the U.S. Department of Defense. “The military has an immediate need for lighter weight and more efficient combustion engines,” explains Shkolnik. “They use engines for much of what they do, and they are the largest consumer of oil on the planet.” What’s more, fuel must be protected, especially as it is transported to the front line. “It can take 100 gallons of fuel to deliver one gallon to the front line. That $400 per gallon is also measured in terms of soldier’s lives.” In other words, efficiency is key. Which is where Shkolnik and LiquidPiston come in.
When charging from the grid, that energy comes from somewhere, and most of it comes from burning fossil fuels. Our solution is more efficient, would lower the C02 footprint, and would allow you to reduce the complexity, weight and cost of your electric vehicles.
They are developing a 5-horsepower engine for the U.S. Army. It’s being used in a hybrid-electric power supply for the M777 Howitzer. With DARPA, they have a 40-horsepower general purpose engine under development, which, Shkolnik explains, is optimized for fuel efficiency. “We’re looking to double the fuel efficiency of today’s engines in a package that is ten times lighter and smaller—it’s really game changing for the military,” he says. However, these military programs are just a starting point for the team at LiquidPiston. “We can replace engines anywhere they are used today,” says Shkolnik. Which means they are looking to collaborate with organizations who have the need for a lighter, more efficient, quieter power source. Of particular interest to the team at LiquidPiston are the possibilities for licensing and co-development relationships with global equipment manufacturers. He cites Dolby Labs as an organization with a similar business model: “Our goal is to develop custom power solutions for partners and then license the technology. At the end of the day, we are a technology company that supplies our expertise to the manufacturers.” LiquidPiston’s giant leap forward is exciting on a number of levels. Not least of which is the fact that their engines can be used to charge batteries in an efficient manner. “This is what gets me very excited, personally—the electrification of vehicles,” says Shkolnik. Everybody wants to go electric, but the search for a lighter, more efficient battery remains one of the greatest stumbling blocks to widespread adoption. Shkolnik proposes using lightweight, efficient generators that would lower an electric vehicle’s carbon footprint. “When charging from the grid, that energy comes from somewhere, and most of it comes from burning fossil fuels. Our solution is more efficient, would lower the C02 footprint, and would allow you to reduce the complexity, weight and cost of your electric vehicles.” By going back to the basics of physics, Shkolnik and LiquidPiston have opened up a host of opportunities for themselves and any company looking to benefit from an improved thermodynamic cycle.