At the recent Engine ORC Consortium event at Queen’s University Belfast, Emily McDaid sat down with the speakers to discuss the growth of heat recovery for an energy-efficient future.
In mid-September, Queen’s University Belfast (QUB) played host to an important meeting of clean energy researchers from large automobile companies, stationary engine manufacturers, and the world’s leading universities.
Held this year at Riddel Hall, the Engine Organic Rankine Cycle (ORC) Consortium visits a different worldwide location each year, and will move to Detroit in 2017. By coming to Belfast, the event showcased the groundbreaking research happening at QUB and around Northern Ireland in waste heat recovery.
96 registrants to the conference hailed from 15 countries and 59 companies including General Motors, Fiat Chrysler, Volvo Trucks, Renault, AgriAD and the Centre of Advanced Sustainable Energy, part of the Invest NI Competence Centre Programme, were amongst the sponsors.
Workshops brought together the transport sector (automobile and heavy transport) with static energy producers.
The conference chairman, Kevin Laboe, and several researchers from QUB discussed why this event represented a critical coming-together of academia with commercial interests.
According to the researchers, it’s about taking lessons learned in waste heat recovery from huge, stabile systems like power plants, and enabling that same level of energy efficiency in automobiles – a considerably trickier feat of engineering.
Anything from 55-80pc of the energy produced by an internal combustion engine is wasted as heat in coolant and exhaust. For 100 units of energy poured (literally) into a car as fuel, only 15 units are used for forward momentum, with 60 to 70 units lost as heat.
By capturing this waste heat, it can be converted into electricity, reducing or replacing the load on the car’s alternator, or providing propulsion via an electric motor in a hybrid vehicle.
Moving away from diesel to a cleaner-burning fuel like natural gas, and introducing waste heat recovery systems to make vehicles (whether non-hybrid or hybrid) much more fuel efficient, is the holy grail of clean transport.
‘In ten years, ORC heat recovery will be as commonplace as turbo technology is today’
– DR STEPHEN GLOVER
The technology behind heat recovery
Conference speakers discussed various technologies that drive this waste heat recovery, such as TEGs, or thermoelectric generators, which create voltage through temperature differentials. Heat exchangers and free piston expanders are other types of technology being tested and deployed.
In general, thermodynamically, the higher the temperature and pressure of the ORC, the more efficient the system.
“That’s why passive, more steady-state operating systems (like a power plant) are recovering waste heat in a more scalable and durable way. To bring that same tech to a dynamic vehicle brings challenges, because the temperatures aren’t as stable, and it needs to be miniaturised,” said Dr Stephen Glover, from QUB’s School of Mechanical and Aeronautical Engineering.
The technology needs to take heat from inside the exhaust system and ultimately be packaged somewhere in the vehicle outside of the passenger cabin, nominally under the bonnet. For this reason, the technology will be deployed in heavy, long-haul trucks before cars.
From an economic standpoint, the efficiency gains need to achieve close to 10pc before the automotive industry would accept this technology as feasible for smaller vehicles.
Belfast heritage encouraging modern innovation
Interestingly, the Titanic was powered by steam piston expanders that were groundbreaking in their day, but now sit at the bottom of the ocean.
During his keynote speech, pro vice-chancellor Mark Price said, “Rather than 22,500kW expanders like in the Titanic, today we’re looking for 1 to 100 kW expanders for automotive and stationary engine applications.
“Operating at up to 2.5 times the pressure of Titanic, but at slightly lower temperatures, the challenge is to apply modern materials and technology to produce these new highly efficient expanders at a cost-effective price.”
Future of heat recovery
The researchers indicated that we are around five to 10 years away from seeing this in vehicles everywhere.
“In ten years, ORC heat recovery will be as commonplace as turbo technology is today,” said Glover.
He continued, “There are growth areas beyond just automotive that would be relevant to our local NI market. For instance, abattoirs are ejecting a steady rate of steam at around 120 degrees Celsius, and anaerobic digesters that turn agricultural and food waste into methane for combustion to produce electricity via an IC engine, are rejecting high-grade heat at 450 degrees Celsius. These stable heat sources could be captured and turned into electricity.”
With factory and plant process efficiencies as low as 15 to 25pc, and stationary gas engines running at around 35pc efficiency, even turning a small percentage of the wasted heat into energy could be a world-changing innovation.
By Emily McDaid, editor, TechWatch
A version of this article originally appeared on TechWatch.