Siemens reports that it is researching technologies that would allow waste heat from vehicles and industrial facilities to be efficiently used without producing carbon dioxide. To date, exhaust gas has generally only been used if its heat is measured in hundreds of degrees Celsius, as in exhaust gas from the gas turbines in natural gas power plants used to generate steam to drive steam turbines, or the chemical industry’s use of waste heat from reactions to preheat other substances.
The “cooler” waste heat is, the harder it is to use. Against this backdrop, Siemens’ Corporate Technology (CT) global research unit is investigating a number of possible solutions to this problem, including the use of thermoelectric generators to produce carbon-neutral electricity in environments with temperatures between 200 and 300 degrees Celsius. The technology, says Siemens, has tremendous potential because thermoelectric components are inexpensive and can be mass produced, but to date no materials have achieved a sufficiently high level of efficiency within the stated temperature range.
Besides research into thermoelectric generation in industrial and power generation applications, Siemens is also researching the use of thermoelectric generators in vehicles, with partners in the EU-funded HeatReCar project which began in 2010, wherein a prototype developed by a research consortium to study the potential of recovering heat from a 3.5t diesel light commercial vehicle’s exhaust to provide electric power, reducing or even eliminating the work otherwise performed by an alternator.
The main objective of the HeatReCar project is to “massively” harvest electrical energy from the exhaust system and re-use this energy to supply electrical components within the vehicle, or to feed the powertrains of hybrid electrical vehicles; the recovery of the thermal energy will be performed by novel thermoelectric (TE) materials capable of highly efficient performance at the requisite high temperatures. One member of the consortium, Fraunhofer IPM, has already achieved a conversion efficiency of 10% at laboratory scale. With other new materials currently under investigation at the same laboratory, efficiencies of up to 20% may be envisioned in a “far” future.
The HeatReCar project has aimed to automate the production process to reduce costs and has designed, optimised and produced a prototype system for testing on a 3.5t diesel LCV. The HeatReCar base case is a thermoelectric generator producing 1.3kW at 100km/h. If applied to the whole European fleet of trucks and with systems easily scaled up to 5kW, the overall diesel fuel savings could reach 5 million tonnes of oil per year. The reduction in CO2 emissions ranges from 20 to 70g/km of CO2 per vehicle, equivalent to 15 million tonnes CO2/year.
Six consortium partners from four EU Member States joined in the HeatReCar project. Besides Siemens, the other five are the project’s manager, Centro Ricerche Fiat, responsible for systems approach, vehicle integration and testing; Robert Bosch (electric/electronics development); ROM Innovation et Stratégie (disseminations actions, value analysis, market study and management support); Termo-Gen AB (thermoelectric module production and process development); Fraunhofer IPM (thermoelectric material production process development); and Valeo (heat transfer). Siemens is in charge of the complete vehicle simulation, including the thermoelectric generator and responsible for designing and producing the DC/DC converter.
The completion of the HeatReCar prototype is due this month, October 2012.
