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Waste Heat Recovery

[Due to the increasing size of the archives, each topic page now contains only the prior 365 days of content. Access to older stories is now solely through the Monthly Archive pages or the site search function.]

MIT team finds chemical functionalization can lead to efficient graphene-based thermoelectric materials

April 14, 2015

Researchers at MIT are predicting that predict that suitable chemical functionalization of graphene can result in a large enhancement in the Seebeck coefficient for thermoelectric materials, leading to an increase in the room-temperature power factor of a factor of 2 compared to pristine graphene, despite degraded electrical conductivity.

Furthermore, the presence of patterns on graphene reduces the thermal conductivity, which when taken together leads to an increase in the figure of merit for functionalized graphene by up to 2 orders of magnitude over that of pristine graphene, reaching its maximum ZT ∼ 3 at room temperature according to their calculations, as reported in a paper in the ACS journal Nano Letters. These results suggest that appropriate chemical functionalization could lead to efficient graphene-based thermoelectric materials.

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Renault Trucks Optifuel Lab 2 vehicle results: reduction in fuel consumption by 22% compared to conventional truck

March 19, 2015

Following several months of road trials and test bench programs adding up to the equivalent of 20,000 km (12,427 miles), Renault Trucks Optifuel Lab 2 laboratory vehicle (earlier post) is recording fuel consumption 22% lower than that of a production Renault Trucks T. This means 7.2 liters of diesel are saved for every 100 km covered, together with a 194 g reduction of CO2 emissions for every kilometre travelled.

Optifuel Lab 2 has been equipped with 20 technologies, each of which meet four major challenges associated with consumption: energy management, aerodynamics, rolling resistance and driving aids. Based on a Renault Trucks T, Optifuel Lab 2 is an ongoing version of the Optifuel Lab 1 introduced in 2009.

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SUTD team proposes low-temperature thermionic converter with graphene cathode; about 45% efficiency

March 09, 2015

Researchers at the Singapore University of Technology and Design (SUTD) are proposing that it is possible to design an efficient graphene-cathode-based thermionic energy converter (TIC)—a device for converting heat to electricity leveraging the phenomenon of thermionic emission, or the release of electrons from a hot body—operating at around 900 K (626 °C) or lower, as compared with a conventional metal-based cathode TIC operating at about 1500 K (1227 °C).

With a graphene-based cathode at 900 K and a metallic anode, the efficiency of the proposed TIC would be about 45%, they concluded in a paper on the work published in the journal Physical Review Applied. If realized, an efficient, low-temperature TIC could provide a supplementary or an alternative approach to thermoelectric devices for waste heat recovery using low grade waste heat—i.e, from engine exhaust or industrial processes.

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Penn State researchers develop thermally regenerative ammonia battery (TRAB) for efficient waste heat recovery

December 08, 2014

Researchers at Penn State University have demonstrated the efficient conversion of low-grade thermal energy into electrical power using a thermally regenerative ammonia-based battery (TRAB). A paper on their work is published in the RSC journal Energy & Environmental Science.

The battery uses copper-based redox couples [Cu(NH3)42+/Cu and Cu(II)/Cu]. Ammonia addition to the anolyte (the electrolyte surrounding the anode) of a single TRAB cell produced a maximum power density of 115 ± 1 W m−2 (based on projected area of a single copper mesh electrode), with an energy density of 453 Wh m−3 (normalized to the total electrolyte volume, under maximum power production conditions).

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GMZ Energy successfully demonstrates 1 kW thermoelectric generator for Bradley Fighting Vehicle

December 03, 2014

GMZ Energy, a market leader in the development of high-temperature thermoelectric generation (TEG) solutions, has successfully demonstrated a 1,000W TEG designed for diesel engine exhaust heat recapture in a Bradley Fighting Vehicle. (Earlier post.) This announcement follows GMZ’s June 2014 demonstration of its 200W diesel TEG. The company integrated five of its 200W TEGs into a single 1,000 W diesel engine solution that directly converts exhaust waste heat into electrical energy to increase fuel efficiency and lower costs.

With this demonstration, GMZ has successfully reached the next milestone in the $1.5 million vehicle efficiency program sponsored by the US Army Tank Automotive Research, Development and Engineering Center (TARDEC) and administered by the U.S. Department of Energy (DOE).

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Vanderbilt/ORNL team discovers new form of crystalline order that could be attractive for thermoelectric applications

November 17, 2014

A team of researchers from Vanderbilt University and Oak Ridge National Laboratory (ORNL) has discovered an entirely new form of crystalline order that simultaneously exhibits both crystal and polycrystalline properties, which they describe as “interlaced crystals.”

The interlaced crystal arrangement has properties that could make it ideal for thermoelectric applications. The discovery of materials with improved thermoelectric efficiency could increase the efficiency of electrical power generation, improve automobile mileage and reduce the cost of air conditioning. Writing in the journal Nature Communications, the researchers reported finding this unusual arrangement of atoms while studying nanoparticles made from the semiconductor copper-indium sulfide (CIS), which is being actively studied for use in solar cells.

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GMZ Energy develops new thermoelectric material with lower raw material costs, higher power output; Hafnium-free p-type half-Heusler

October 21, 2014

Researchers at GMZ Energy, a provider of nano-structured thermoelectric generation (TEG) power solutions for mobile and stationary waste-heat recovery (earlier post), with their colleagues at the University of Houston and Bosch, have developed a new Hafnium-free p-type half-Heusler material which offers substantially lower raw material cost than conventional half-Heusler materials. The material also features enhanced performance and mechanical strength due to GMZ’s patented nanostructuring process.

As presented in a paper published in the RSC journal Energy & Environmental Science, the new material improves thermoelectric power output compared to a conventional Hafnium-based product. Further, by replacing the costly Hafnium element with GMZ’s proprietary formulation, the overall cost-per-watt of the TEG is lowered. Cost reduction is beneficial for vehicle and industrial waste heat recovery applications, the developers noted in their paper.

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MIT/Stanford team refines TREC battery for harvesting low-grade waste heat

October 17, 2014

In May, researchers at MIT and Stanford University reported the development of new battery technology for the conversion of low-temperature waste heat into electricity in cases where temperature differences are less than 100 ˚Celsius. The thermally regenerative electrochemical cycle (TREC) uses the dependence of electrode potential on temperature to construct a thermodynamic cycle for direct heat-to-electricity conversion. By varying the temperature, an electrochemical cell is charged at a lower voltage than discharged; thus, thermal energy is converted to electricity. (Earlier post.)

Now, in a paper in the ACS journal Nano Letters, the team reports a refinement of the earlier Prussian blue analog-based system system, which although it operated with high efficiency, used an ion-selective membrane which, in turn, raised concerns about the overall cost. The refined system is a membrane-free battery with a nickel hexacyanoferrate (NiHCF) cathode and a silver/silver chloride anode. When the battery is discharged at 15 °C and recharged at 55 °C, thermal-to-electricity conversion efficiencies of 2.6% and 3.5% are achieved with assumed heat recuperation of 50% and 70%, respectively.

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GMZ Energy announces new, high-power thermoelectric module: TG16-1.0

October 01, 2014

TG16. Click to enlarge.

GMZ Energy, a developer of high temperature thermoelectric generation (TEG) solutions, has introduced the TG16-1.0, a new thermoelectric module capable of producing twice the power of the company’s first product, the TG8-1.0. By doubling the power density, GMZ’s new module substantially increases performance while maintaining a minimal footprint.

GMZ has been using TG8 modules in developing vehicular thermoelectric generators for the Bradley Fighting Vehicle (1 kW TEG) as well as to design and to integrate a light-duty vehicle TEG into a Honda Accord as part of a DOE-funded project. (Earlier post.)

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Renault Trucks’ Optifuel Lab 2 lab vehicle integrates technologies for more efficient big rigs; road test results coming in 2015

September 11, 2014

Renault Trucks’ heavy-duty Optifuel Lab 2 laboratory vehicle brings together various technologies designed to reduce fuel consumption in heavy-duty trucks and to prepare the way for future production models. Renault Trucks will display a scale model of Optifuel Lab 2 at the upcoming IAA. The vehicle is currently on the road to calculate the fuel savings it can achieve. These figures will be announced during the first quarter of 2015.

Optifuel Lab 2 has 20 technologies on board, each one of which addresses the four main issues associated with consumption: energy management, aerodynamics, wheel resistance and driving aids. Based on a Renault Trucks T, Optifuel Lab 2 is an ongoing version of the Optifuel Lab 1 introduced in 2009. The project has been developed with support from eight partners: Plastic Omnium, Michelin, Sunpower, Renault, IFP Energies Nouvelles, CEP-Armines, CETHIL-INSA from Lyon and LMFA-Ecole Centrale from Lyon. It is also supported by ADEMA, the French Agency for the Environment and Energy Control.

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MIT/Stanford team develops battery technology for the conversion of low-grade waste heat to power; TREC

May 22, 2014

Researchers at MIT and Stanford University have developed new battery technology for the conversion of low-temperature waste heat into electricity in cases where temperature differences are less than 100 degrees Celsius. Their approach is based on a phenomenon called the thermogalvanic effect—the dependence of electrode potential on temperature—and is described in a paper published in the journal Nature Communications by postdoc Yuan Yang and professor Gang Chen at MIT, postdoc Seok Woo Lee and professor Yi Cui at Stanford, and three others.

The MIT and Stanford team devised an electrochemical system using a copper hexacyanoferrate cathode and a Cu/Cu2+ anode to convert heat into electricity. The thermally regenerative electrochemical cycle (TREC) entails a four-step process: (1) heating up the cell with waste heat; (2) charging at high temperature; (3) cooling down the cell; (4) discharging at low temperature.

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Dearman-led consortium awarded $3.1M to develop waste-heat-recovery system using liquid air engine

April 23, 2014

A consortium led by the Dearman Engine Company has been awarded £1.86 million (US$3.12 million) in the latest round of IDP10 funding from the UK’s Technology Strategy Board to support the development of a heat-recovery system for urban commercial vehicles. The tenth competition under the Low Carbon Vehicles Innovation Platform’s integrated delivery program (IDP), IDP10 is targeting the building of an integrated low-carbon-vehicle innovation chain, from the science base, through collaborative R&D to fleet-level demonstration.

The Dearman project is to deliver a production-feasible waste-heat recovery system for urban commercial vehicles, which offers life-cycle CO2 savings of up to 40%; fuel savings of 25%, with the potential of up to almost 50%; and potential payback in less than three years. The project uses the Dearman Engine, a highly-efficient liquid nitrogen or air (LiN) engine (earlier post) that harvests low-grade heat sources and, in this configuration, is most effective in urban duty cycles, working with the internal combustion engine (ICE) as a hybrid powertrain.

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