Libertine: Accelerating Market Adoption of Linear Generators

As the world adopts more solar and wind power, there’s an increasing need for clean, on-demand electricity from renewable sources. Global electricity demand is expected to double by 2050. This surge is due to several factors: the shift from fossil fuels to electric vehicles and heating systems, the dramatic increase in energy needs of data centers running AI models and services, and continued economic growth in many areas. This surge in demand, coupled with a surge in intermittent renewable electricity supply, has prompted energy companies and engine makers to explore novel technologies for decentralized, dispatchable power generation to better complement intermittent renewables and battery energy storage solutions.

For power generation to be ‘dispatchable’ it must be controllable in response to the imbalance between other sources of intermittent supply, and the electrical power demands that must be served. As the share of intermittent renewables grows there will be periods of hours or days when little dispatchable power is required. And yet there will be some periods of days or weeks when dispatchable power will be required to keep the lights on, and to keep society running. While batteries can supply dispatchable power for several hours, renewable fuels are a more cost-effective solution for storing energy over longer periods until it is needed.

Power generation technologies such as gas turbines, fuel cells and conventional internal combustion engines can convert renewable fuels to electrical power on-demand, but each have their drawbacks: fuel cells are expensive and have limited life; gas turbines and conventional internal combustion engines are less efficient and offer little fuel flexibility. Linear generators are a new category of dispatchable power generator, now entering commercial use, that leverages advances in power electronics and control technologies to deliver clean, efficient, fuelflexible power generation. A linear generator does away with the crankshaft and mechanical complexity of a conventional engine, and instead generates electrical power directly from piston motion using software-controlled linear electrical machines. This arrangement also allows for softwarecontrolled ‘electronic compression’ of the fuel and air mixture. This advanced control orchestrates the reaction more precisely, enhancing efficiency and reducing harmful emissions, regardless of the type of renewable fuel used.

An emerging leader in this new category is UK company Libertine, whose efficient, fuel-flexible and compact linear generator technology is designed for on-demand power generation. Unlike US company Mainspring Energy, Libertine does not make complete linear generator products, but instead provides the linear electrical machines and controls that sit at the heart of linear generators. Linear electrical machine efficiency, durability, cost effectiveness and above all linear motion control have been the sticking points for most linear generator product development efforts since the mid 1990s. For this reason linear generator technology has yet to enter mainstream use across multiple applications. By focusing on solutions to these problems, and providing its technology to linear generator product developers together with engineering support for product integration, Libertine aims to change that.

Libertine’s technology has been over a decade in the making, and following some recent notable technical and commercial progress with customers such as Hyliion and partners including MAHLE Powertrain, Libertine is now poised to bring linear generator technology to multiple engine OEMs seeking to integrate Libertine’s technology into their new product development, and accelerating time to market entry.

Libertine has created intelliGEN and HEXAGEN, two technology platforms for linear generator product developers that combine high-performance linear electrical machines, embedded power and motion control systems, and a suite of simulation and data processing tools. Both platforms integrate recent advances in the external technology environment: proven advances in component technologies, new material classes, advanced manufacturing methods, modular power electronics, embedded control hardware, and more capable design and simulation tools.

For example, the cost and performance of power electronics have been transformed by the large scale deployment of distributed wind and solar renewables, since every installation must convert its output to grid-synchronised electrical power. In parallel, Moore’s law has dropped the cost of controllers whilst advances in microprocessor design and networking technologies have enabled more effective embedded controller architectures.

High performance magnetic materials, new manufacturing techniques using powder-pressed metals, and ever more sophisticated computer aided design, simulation, data acquisition and post-processing tools all contribute to a technology environment that, for the first time, provides all the necessary ingredients for linear generator product development. These advances have been developed independently for a wide range of scale-up applications, but when combined they now cross a threshold that makes linear generator development both technically and economically feasible.
Located in Sheffield, at the heart of the UK’s advanced manufacturing and electrical machines technology clusters, Libertine is ideally placed to take advantage of these recent advances. Libertine’s platform technologies combine its proprietary control software and electrical machine architecture with combustion and control system interfaces and developer tools designed to speed up and de-risk the development cycle for linear generator product developers. For example, US customer Hyliion Inc. recently integrated Libertine’s HEXAGEN platform with their additive manufactured heat engine technology to create the KARNO generator. Hyliion compressed a complex first-of-a-kind product development and demonstration programme into less than two years, showing the impact that using Libertine’s technology can have on linear generator development productivity.

“Our intelliGEN and HEXAGEN platforms focus on the mechanical, electrical, and control interfaces to provide flexibility to customers such that they can incorporate the platform into their own proprietary linear generator product development,” says Sam Cockerill, CEO at Libertine. “In a period of just 20 months from the initial purchase order, Hyliion were able to rapidly close out key technical milestones through detailed design and simulation, prototype hardware integration, and complete several months of dyno testing before integration into a rolling demonstration vehicle that was exhibited at the ACT Expo in California during May 2023. A strategic review that followed this successful demonstration has resulted in Hyliion pivoting its entire focus towards the commercialization of its KARNO generator technology”.

A modular technology platform for more applications

Libertine’s intelliGEN and HEXAGEN technology platforms have been developed with modularity in mind. An individual cylinder or Linear Power System ‘cell’ combines Libertine’s linear electro-mechanical systems with an opposed free piston internal combustion system. Libertine provides a reference design, but supports customer integration of their own proprietary combustion systems since that is often an area of deep customer expertise.

“We’re not a combustion engine developer” says Cockerill, “But we know what that takes. Our intelliGEN system incorporates a reference internal combustion system to provide a performance baseline, but ultimately it’s our customers who are the experts when it comes to combustion systems development, product integration and calibration. Our goal is to provide the linear electro-mechanical hardware platform and ‘driver-layer’ power and control software as a platform on which their future products can be built.

Libertine expects to see more engagements along similar lines to its work with Hyliion and its continuing collaboration with Ashok Leyland, whose Advanced Engineering group is evaluating the company’s technology for use in their commercial vehicle portfolio.
In the past year, Libertine has been working with leading research organizations to integrate the intelliGEN platform into OpenFPE, a turn-key research engine solution for advanced combustion research. The company is launching OpenFPE in 2024 and is seeking further opportunities to provide this solution to research programs formed to advance or make use of linear generator technology.

Research engines are a low-volume, high-value niche, but high-quality published research using OpenFPE can play an important role in helping build OEM awareness and interest in the category. It will also provide Libertine and its OEM customers with operating hours that will help further accelerate and de-risk the performance trajectory of commercial products.

“Electronic fuel injection, ignition and boost have provided the means for OEM developers to create today’s clean, efficient engines. Electronic compression provided by Libertine will empower OEMs to create the engines of the future that will be more fuel-flexible, cleaner and more efficient than anything we have seen so far” says Cockerill. “Our whole team is driven by a shared vision of the positive social and economic impacts that linear generator technology will have, allowing the global economy to continue growing even as it decarbonizes. We are sure this change will happen with or without Libertine. Our mission, then, is to make sure it happens sooner by doing what we do best.”