The Indian Institute of Science has unveiled a breakthrough compact tandem cylinder reciprocating engine for CO₂-based power generation, offering a 100 kW output with a footprint ten times smaller than conventional systems and a technology readiness level of 6.

This innovation directly addresses the limitations of supercritical CO₂ turbomachinery at sub-megawatt scales, opening new opportunities for aerospace, automotive, and energy industries.

The problem with conventional supercritical CO₂ power-generation systems lies in their reliance on high-speed turbomachinery. At sub-megawatt scales, these systems demand turbine speeds between 60,000 and 1,00,000 rpm, which introduces rotor-dynamics challenges, sealing difficulties, and high manufacturing costs.

The complexity of precision components has limited commercial viability, particularly for decentralised and compact applications.

The innovation developed at IISc replaces turbomachinery with a reciprocating piston-cylinder arrangement. This compact tandem cylinder reciprocating engine integrates compression, expansion, and heat exchange within a single-cylinder design.

By adopting this approach, the system reduces operating speeds by nearly 90–95 per cent compared to conventional designs, while maintaining efficiency and scalability.

Performance parameters are notable. The engine generates more than 100 kW of power, achieves a round-trip efficiency of approximately 35 per cent, and occupies a footprint ten times smaller than traditional power blocks.

These attributes make it highly suitable for industrial waste-heat recovery and decentralised energy generation. The reduction in size and speed also enhances reliability and lowers maintenance requirements.

The technology readiness level has reached stage 6, indicating prototype demonstration in a relevant environment. This positions the engine close to commercial deployment, with opportunities for collaboration and licensing actively being sought. The IISc’s IPTel office is facilitating industry partnerships, with contact available through office.iptel@iisc.ac.in.

Relevant industries include aerospace, automotive, and energy. In aerospace, compact CO₂ engines can provide auxiliary power units with reduced weight and improved efficiency. In automotive applications, they can support hybrid systems and waste-heat recovery. In energy, they offer decentralised solutions for sub-megawatt generation and industrial waste-heat conversion.

The IISc team, led by Dr Pramod Kumar, has already filed patents internationally and domestically. The Indian patent was filed in December 2020, with subsequent filings in the United States and under PCT frameworks. The technology has been granted protection under US patent US12209553B2, published in January 2025, ensuring intellectual property security for commercialisation.

Supporting infrastructure at IISc includes a supercritical CO₂ test loop and high-speed turbomachinery rigs. The department has produced 154 publications, secured seven granted patents, and undertaken eight consultancy projects. Sixteen students are actively engaged in research, contributing to the development of sustainable energy technologies.

The broader context of supercritical CO₂ research highlights its potential as a replacement for steam in power plants. With properties combining the density of a liquid and the behaviour of a gas, sCO₂ enables compact, efficient power cycles.

India’s efforts, supported by the Department of Science and Technology, have already demonstrated indigenous sCO₂ power blocks. The reciprocating engine represents a critical step in overcoming the engineering challenges of turbomachinery at small scales.

This innovation aligns with global priorities in sustainability and energy efficiency. Industrial waste-heat recovery, which accounts for nearly 63 per cent of global primary energy consumption, can be significantly enhanced through compact CO₂ systems. By reducing dependence on water and lowering capital costs, the reciprocating engine contributes to climate-conscious energy solutions.

The commercialisation opportunity is significant. Industries seeking compact, efficient, and scalable power solutions can collaborate with IISc to integrate this technology. The invitation for licensing discussions underscores the readiness of the innovation for market adoption.

Agencies