Shape memory alloys help turn waste heat into power
If you run a generator or produce waste heat, then you could benefit from a new design of engine that turns that waste heat into power, at low cost and with a high power density. The Exergyn Drive enables users to increase revenue from power-exporting plant, and/or reduce fuel bills and carbon emissions. It generates zero emissions and there are no hazardous materials involved. The developers say the Exergyn Drive is easy to install and offers a payback in just three years.
The potential of waste heat from industrial processes is enormous, as Exergyn head of product management Michael Langan explains: “To put it into context, double the entire energy output of Saudi Arabia is locked up in waste heat. And the value of the low grade waste heat problem is enormous – some €440 billion based on 2012 figures.”
Langan adds that the Exergyn Drive alone could reduce world carbon emissions by 2% if it was deployed at its full potential, equating to some 750 million tonnes. “That may not sound a lot on its own, but with 30 to 50 companies like us, that would be the climate change problem solved. And crucially, any carbon reduction from using the Exergyn Drive would save companies money by significantly reducing their fuel bills.”
Founded in 2012 by Alan Healy, Barry Cullen and Kevin O’Toole, Exergyn – based on the DCU Innovation Campus in Dublin, Ireland – received €2.48 million in EU funding in 2015 to commercialise the Exergyn Drive engine. This was awarded through the SME Instrument of Horizon 2020, the EU’s research and innovation funding programme.
The Exergyn Drive works wherever there is a hot water or hot fluid stream, and it is particularly suited to industrial waste heat applications such as biogas/landfill gas, syngas, CHP, geothermal and cargo shipping. The technology behind the Exergyn Drive is a shape memory alloy (SMA) of nickel and titanium. Shaped into a long bar, this SMA contracts by around 3-4% as it heats up, for example when cycled between water at 30°C and water at 90°C. And this simple concept forms the core of the Exergyn Drive. The expanding and contracting SMA drives a hydraulic actuator to convert mechanical motion into power. Langan comments: “There are very few moving parts, and most of the parts are available off-the-shelf, with four-fifths of the Exergyn Drive being built around established technologies.
Exergyn has produced a ‘Delta’ prototype of the drive with four cores, each of which lifts 60 tons every 10 seconds, in a total volume of around 3m3. The output can be in the form of electricity or mechanical power, and the technology is scalable, currently built around modules capable of generating 10kW.
The biogas sector is a particular target for Exergyn. Biogas is an attractive commercial prospect for power generation suppliers, project developers and owners alike, but from Exergyn’s perspective it is attractive because its low grade waste heat is an enormous untapped potential just waiting to be unlocked. The UK alone could represent a €90m market for the Exergyn Drive, while the rest of Europe could add up to €267m. And it is a simple retrofit in a market that currently makes no use of its waste heat.
Other attractive markets include CHP, which Exergyn estimates could be worth €6bn. Syngas could contribute another €1.7bn. Combined with biogas and a smaller contribution from geothermal, the initial European markets could be worth over €8bn.
According to Exergyn, the UK has a biogas universe of 968 sites, and the company is looking for partners to help trial the technology within the sector. Independent verification the Exergyn Drive has come from the Institution of Diesel and Gas Turbine Engineers, whose president Emeritus John Blowes said: “I can confirm that 90°C water has been converted to reciprocating and rotational motion. I know from personal experience and detail provided that this technology will function at a range of water temperatures and is scalable. I’m not aware of any other organisation presently converting low-grade heat to useful power on a commercial basis.”
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