Nitinol helps energy-efficient engine turn waste heat into electricity


A new energy-efficient engine that generates electricity from waste hot water could reduce both carbon emissions and energy consumption within the shipping industry and many other sectors.

The application uses the special ‘shape memory’ properties of Nitinol (UNS N01555)—a nickel-titanium alloy—and is being developed by Dublin-based firm Exergyn.
According to Exergyn’s Head of Product Management Mike Langan, “the technology will make recovery of ‘low-grade waste heat’1 cost effective for the first time.”

Langan says the technology can help ship owners to improve efficiency and reduce emissions, helping them to comply with the increasingly stringent regulations.
Indeed, the International Maritime Organisation (IMO) has forecast a 250% increase in shipping emissions if actions are not taken to improve engine efficiency.
Furthermore, the technology is safe for shipping as there are no hazardous fluids prone to leakage and it has a low operating pressure.

Exergyn aims to deliver a product that is one of the lowest cost forms of power generation, with a LCOE2 (levelised cost of electricity) of 0.045 €/kWh or less.
Exergyn were awarded 2.5 million euros from the European Commission’s Horizon 2020 fund to help bring the product to market. Industrial tests are due to start later this year.
Tests for the shipping sector are scheduled for 2019, with a further 6,000 hours of testing the full system in the pipeline.

How Nitinol’s unique properties help shape the new waste heat technology

As a metal alloy of nickel and titanium, Nitinol exhibits the unique properties of shape memory and superelasticity. Its key properties are that although it can be bent out of shape, it reverts to its original structure when heated to a certain temperature. Nitinol also expands when cooled, making it an ideal component of the new technology.

A bundle of metre-long Nitinol wires is attached to a piston, with cold and hot water being alternately flushed over the wires every ten seconds. This rapid expansion and contraction of about four centimetres drives the piston. A linked hydraulic system then drives a generator.

Most existing applications for Nitinol only require small quantities of the material, e.g. medical devices. The new technology could be the first industrial-
scale application of Nitinol. Each unit would contain several kilograms of this shape memory alloy.

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