Energy resources are under constant pressure to grow to match the rate of energy consumption which has been steadily increasing since the last 50 years. The expected depletion of fossil resources and the global climate change are the major factors that have added pressures to the task of global energy planning. These pressures, however, have helped fuel research and industry drives to find alternative and renewable energy resources and modify the current practices in the energy industry.

Recuperation of waste heat is a rather new concept emerging in the field of process engineering. Waste heat offers a low-grade thermal resource which has previously been overlooked or considered of no value. To obtain work or electrical power from such a resource, an organic Rankine cycle or a trilateral flash cycle can be used in a plant which consists of heat exchangers, pumps and gas expanders. The performance of these plants depends mainly on the efficiency of the gas expander used in them for energy generation. A number of gas expanders are available, such as scroll expanders, screw expanders, reciprocating expanders and rotary expanders. The limaçon expander is a new addition to the existing designs. The limaçon design, however, offers some thermodynamical and mechanical aspects beyond what other designs can offer. This chapter will introduce the limaçon technology and shed some light on its potential to operate thermal power plants fuelled by low-grade heat resources. The application of this endeavour should readily extend to various scenarios such as in residential-scale power generation, to improve the process efficiency in existing power plants, food processing plants and mineral processing plants to name a few.