Saving heat waste by improving thermal efficiency

A researcher has proposed a more efficient way to generate electricity from waste heat

Spotted: Most waste heat from industry is currently ejected into the environment — which is a lot of energy going up the flue. If this wasted energy could instead be recovered, it could help to significantly reduce the environmental footprint of a number of manufacturing industries. In a recent paper, Dr Martin White, a lecturer in Mechanical Engineering at the University of London, proposes a novel system for improving the thermal efficiency of power production.

Dr White’s work focuses on Organic Rankine Cycle (ORC) systems, which are used to convert waste heat into energy in steam turbines and engines that operate at low to medium temperatures. The main difference is that ORCs use organic substances instead of water steam, as working fluid. The organic working fluid has a lower boiling point and a higher vapour pressure than water and is, therefore, able to use low-temperature heat sources to produce electricity. 

In a conventional ORC system, the turbine is designed to operate with a fluid that is in a gaseous state. This is done to avoid the presence of liquid droplets within the turbine that could damage or erode the machine. However, Dr White suggests that a turbine design using a two-phase system (a combination of liquid and vapour) would enhance the performance of ORC systems.

Dr White explains: “One of the most promising groups of waste-heat recovery technologies are those that are able to convert this waste heat into electricity. However, current technologies, typically based on the organic Rankine cycle (ORC) – which is similar to a steam cycle but operates with a different fluid rather than water – typically have relatively poor thermodynamic performance and are associated with high costs.”

A lot of energy is wasted in manufacturing and power generation, and finding ways to minimise this, or convert it to energy, could lead to important improvements in sustainability. Some innovations in this area we have recently covered include a thinner, more resilient electric engine power inverter which increases the efficiency of EV engines and the use of WiFi as a power source.

Explore more: Agriculture & Energy Innovations | Sustainability Innovations