How to generate energy from industrial waste heat

What if excess heat from energy-intensive industrial processes could be harnessed for energy generation? This is the idea behind the POWHER project, funded under the NRRP as a Research Project of National Interest (PRIN – MUR). The project is coordinated by Professor Andrea Spinelli (Principal Investigator, Department of Energy of Politecnico di Milano) and Professor Lisa Branchini (Head of Local Unit, Department of Industrial Engineering of the University of Bologna).

"Exploiting industrial waste heat is crucial for a sustainable energy future," they explained. "POWHER aims to turn this potential into a reality thanks to innovative solutions."

Energy-intensive industries, such as glass, cement, metal, paper and food processing, waste huge amounts of heat – a neglected resource that could cover 5% of total electricity demand in the European Union. In other words, the electricity consumption of 20 million households or the production of 19 large power plants.

The POWHER project seeks to unleash this potential through an approach based on Organic Rankine Cycles (ORCs) – a similar technology to traditional steam cycles, used for energy generation from low to medium-high temperature heat. Through the vaporisation of an organic fluid instead of water, organic Rankine cycles allow building simpler and cheaper plants with good conversion efficiency.

The research group will focus in particular on the implementation of Partial Evaporation Organic Rankine Cycles (PE-ORCs), an innovative version of organic Rankine cycles that, through a non-complete evaporation of the organic fluid, could increase plant efficiency by up to 30%.

"Both theoretical and experimental studies will aim to overcome the obstacles that have been holding this technology back – the development of efficient turbines for two-phase (liquid-vapour) fluids and the optimisation of plant control strategies," said Spinelli and Branchini.

Experimental activities will take place at the Test Rig for Organic VApors (TROVA) of Politecnico di Milano and at the micro-ORC test rig in the Laboratory of Microgeneration Technologies of the University of Bologna.