Ultra-High Efficiency Alcohol Engines Using Optimized Exhaust Heat

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Daniel Cohn
MIT Energy Initiative
Leslie Bromberg
Plasma Science and Fusion Center, MIT
Managed By
Christopher Noble
MIT Technology Licensing Officer - Clean and Renewable Energy
Patent Protection

Ultra-high Efficiency Alcohol Engines Using Optimized Exhaust Heat Recovery

US Patent 9,234,482


A primary application for this technology is found in internal combustion engines.

Problem Addressed

In recent years, there has been increasing interest in methanol as an alternative fuel for both light and heavy-duty vehicles, particularly in China. This interest has resulted from methanol being the most efficiently and inexpensively produced liquid fuel that can be made from coal and natural gas and also from thermochemical conversion of biomass and waste materials.

In addition to these advantages methanol has a unique set of properties that give it the potential for a substantial increase in efficiency of vehicular engines, such as knock suppression in spark ignition engines and low temperature endothermic reforming into hydrogen-rich gas. Previous work has been done on taking advantages of these properties. However, it fell substantially short of obtaining the full efficiency increase that can be obtained from methanol-fueled engines.


This invention pertains to an engine system using alcohol Rankine heat recovery where the engine heat converts alcohol into hydrogen-rich gas which is then introduced into the engine cylinders. The engine system includes a source of liquid alcohol along with an internal combustion engine generating a high-temperature exhaust. A structure is provided for introducing a first portion of the liquid alcohol into the engine and a series of heat exchangers forming a Rankine heat recovery cycle is provided to extract heat from the exhaust and transferring the heat to a second portion of the liquid alcohol, causing it to change phase to a gaseous alcohol. A heat exchanger/catalyst is heated by the exhaust to reform the gaseous alcohol into a hydrogen-rich reformate. Valve structure rapidly introduces the reformate into the engine for combustion and a control system is provided for controlling the ratio of the first and second portions of the liquid alcohol to maximize the amount of the second portion of the liquid alcohol while using a minimum amount of the first portion needed to prevent knock. The heat recovery system uses metallic foams on fin heat exchangers.



  • Substantial improvement in efficiency
  • Improves economic and environmental attractiveness of natural gas and coal-derived fuel