Thermoelectric exhaust energy recovery with temperature control through heat pipes

Currently, a great deal of the automotive industry’s R&D effort is focused on improving overall vehicle environmental and energy efficiency. For instance, one of the things that Electric Vehicles (EVs) and Hybrid cars (HEV) have in common is the recovery of waste energy, namely during braking. But, when an I.C. engine is operating (e. g. as a range extender in an EV), a large amount of energy is also wasted within the exhaust gases and with engine cooling, energy that could otherwise be recovered by different methods. This paper reports on the recovery of waste thermal energy using thermoelectric generators (TEG) for application in hybrid, extended range electric vehicles and more generally in any vehicle that could benefit from the generation of a small amount of electric current that would reduce the alternator operation time. Although some manufacturers are trying to develop TEGs to use at exhaust temperatures, there are still no commercially available TEG modules capable of withstanding these extreme temperatures. The present work assesses the potential of the use of heat pipes (HP) as a means of transferring energy from the hot exhaust gases to the TEG modules at a compatible temperature level while minimizing the loss of efficiency due to temperature downgrading. The type of HP used in this study is called Variable Conductance Heat Pipe (VCHP), and its deployment has the advantage of inducing good temperature control. Various types of HPs were designed, manufactured, tested and improved with the aim of enhancing the overall heat transfer process, enabling an optimal level of electric energy recovery from the referred TEG modules. This was accomplished by the testing of different fluids inside the HP and by regulating the pressure of the gas chamber. Although the system is still under improvement, the results indicate that the use of VCHPs in conjunction with thermoelectric generators is a convincing technique for recovering otherwise wasted energy from the exhaust gases.MIT Portugal (MIT-Pt/EDAM-SMS/0030/2008)Fundação para a Ciência e a Tecnologia (FCT) (bolsa SFRH / BPD / 51048 / 2010

Modelling of thermoelectric generator with heat pipe assist for range extender application

Recent trends towards electrification of vehicles favour the adoption of waste energy recovery into electricity. Battery-only Electric Vehicles (BEV) need a very large energy storage system so the use of a Range Extender (RE) may allow a significant downsizing of these bulky components. The Internal Combustion Engines (ICE) have two major discarded energy fluxes, engine cooling and exhaust gas. In Extended Range Electric Vehicles (EREV) and hybrids the potential for heat conversion into electricity is particularly convenient. The direct conversion of thermal energy into electricity, using Thermoelectric Generators (TEG) is very attractive in terms of complexity. However, current commercial TEG modules based on Seebeck effect are temperature limited, so they are unable to be in direct contact with the exhaust gases. A way to downgrade the temperature levels without reducing its potential is to interpose Heat Pipes (HP) between the exhaust gas and the modules. This control of maximum temperature at the modules is achieved by regulating the pressure of phase change of the HP fluid. Such design is convenient for engines with large thermal load variations, such as the RE being developed by the team, with a low (15kW) and a high (40kW) power mode of operation. This system will be able to operate efficiently in both modes. The present work presents the thermal modelling of such a system in order to assess the suitability of this approach. This work is complemented with the experimental work being carried out by the team in this subject, already with some published results. The model was validated with experimental data with a good correlation. Therefore, it was possible to demonstrate the potential of this system for wasted heat recovery.MIT Portugal, Fundação para a Ciência e a Tecnologia (FCT

Temperature controlled exhaust heat thermoelectric generation

The amount of energy wasted through the exhaust of an Internal Combustion Engine (ICE) vehicle is roughly the same as the mechanical power output of the engine. The high temperature of these gases (up to 1000°C) makes them intrinsically apt for energy recovery. The gains in efficiency for the vehicle could be relevant, even if a small percentage of this waste energy could be regenerated into electric power and used to charge the battery pack of a Hybrid or Extended Range Electric Vehicle, or prevent the actuation of a conventional vehicle's alternator.SFRH / BPD / 51048 / 2010MIT-Pt/EDAM-SMS/0030/200

Heat-pipe assisted thermoelectric generators for exhaust gas applications

Millions of hybrid cars are already running on our roads with the purpose of reducing fossil fuel dependence. One of their main advantages is the recovery of wasted energy, namely by brake recovery. However, there are other sources of wasted energy in a car powered by an internal combustion engine, such as the heat lost through the cooling system, lubrication system (oil coolers) and in the exhaust system. These energies can be recuperated by the use of thermoelectric generators (TEG) based on the Seebeck effect, which transform heat directly into electricity To recover the energy from the hot (up to more than 700 ºC) exhaust gases it is possible to use controlled heat transfer, but this would limit the heat transfer potential at partial loads, as commercialy available TEG are limited by their maximum allowable temperature (~250ºC). Therefore Heat Pipes were used as an alternative heat transfer mean, so it would be possible to retain the heat transfer potential, while controlling the maximum temperature at a reasonable level. This is the method to recover the exhaust heat presented in this work. Numerical simulations were performed to assess the potential for this design, involving internal combustion engine simulation, thermoelectric generators simulation and heat transfer modelling. Additionally, the use of variable conductance heat pipes (VCHP) is discussed, as a means of achieving TEG module maximum temperature limitation.MIT Portugal, Fundação para a Ciência e a Tecnologia (FCT

Influence of heat pipe operating temperature on exhaust heat thermoelectric generation

Increasingly stringent targets on energy efficiency and emissions, as well as growing vehicle electrification are making attractive the electric recovery of the energy normally wasted through the tailpipe of Internal Combustion Engines. Recent developments in thermoelectrics (TE) may soon make them a viable solution for such applications. This team has been exploring the potential of using TE modules in combination with variable conductance heat pipes for transferring the exhaust heat to the generator with very low thermal resistance and at a constant, prescribed temperature. This passive temperature control eliminates the need for by-pass systems in the event of temperature overshoots. The operating temperature of a generator should be as high as possible in order to maximize the Seebeck effect. However, currently available modules are temperature limited. Moreover, the higher the HP temperature the less the usable thermal power at the exhaust will be (heat can only be transferred to from a hotter to a colder body). The present work assesses both theoretically and experimentally the influence of the HP temperature in the electric output of a thermoelectric generator. A small diesel engine and a generator were tested and it was found that a high HP operating temperature is only limitative for performance in the cases where low exhaust temperature and low engine power are present. In those cases it is possible to estimate an optimal HP temperature in order to maximize power output. The combined use of Seebeck modules and heat pipes was found to be highly advantageous in various ways.Fundação para a Ciência e a Tecnologia (FCT), FEDER e POFC CompeteMIT Portugal EDAM, Project MOBI-MP

Checklist of the shallow-water marine molluscs of the Azores: 1 - Pico, Faial, Flores and Corvo

An up-to-date commented check-list of the shallow-water marine molluscs of Pico, Faial, Flores and Corvo islands (Azores, Portugal) is provided, based on literature records, on material deposited at the Department of Biology of the University of the Azores (DBUA) as a result of the scientific expeditions "Flores/89", "Açores/89" and "Pico/91", and on photographic material at the Department of Oceanography and Fisheries/University of the Azores (DOP/UA). The collections of the Museu Carlos Machado - Historia Natural, MCM-HN, of the Museu de Zoologia - Museu de Historia Natural da Faculdade de Ciencias e Tecnologia da Universidade de Coimbra, MZ/MHN-FCTUC, and the mollusc collection deposited at DOP/UA were surveyed and the results are included in this report. Two hundred and fifty five taxa of shallow-water molluscs are reported to Pico, Faial, Flores and Corvo Islands (196 Gastropoda, 50 Bivalvia and 9 Cephalopoda). Of these, 32 are dubious records (23 Gastropoda, 8 Bivalvia and 1 Cephalopoda), there remaining 197 confirmed species to these islands. A total of 26 taxa were identified only down to the genus level (25 Gastropoda and 1 Bivalvia)

Examination of Grasmick et al.’slow Self-control Scale and of a Short Version With Cross-Gender Measurement Invariance

Grasmick et al.’s Low Self-Control Scale (LSCS) is considered the gold-standard of self-control measures due to the frequency of its use in criminology. The aim of the present study is to examine the psychometric properties of the LSCS from a more modern psychometric perspective and develop a shorter version. Our sample consisted of young adults (N=610, M=21.33years, SD=3.09) from Portugal. The six-factor intercorrelated model of the LSCS showed an adequate fit, but models that would legitimate using a total score could not be confirmed. The subscales’ intercorrelations revealed some low non-significant correlations. The six subscales showed distinctive correlates with other measures, with three subscales presenting some problematic correlations. Confirmatory factor analysis was subsequently used to develop a three-factor shorter version with strong cross-gender measurement invariance and good reliability. Findings have implications for the validity of the general theory of crime specifically which components of self-control have the greatest empirical linkages to conduct problems and related deviance.Fundação para a Ciência e Tecnologia - FCTinfo:eu-repo/semantics/publishedVersio

Effects of different slipping methods on the mortality of sardine, Sardina pilchardus, after purse-seine capture off the Portuguese Southern coast (Algarve)

The effects of two different slipping methods on the survival, physical and physiological response of sardines, Sardina pilchardus, captured in a purse-seine fishery were investigated in southern Portugal. Sardines were collected and transferred into holding tanks onboard a commercial fishing vessel after being captured, crowded and deliberately released using two slipping procedures: standard and modified. The standard slipping procedure aggregated fish at high densities and made them "roll over" the floatline, while the modified procedure aggregated the fish at moderate densities and enabled them to escape through an opening created by adding weights to the floatline. Both slipping methods were compared with minimally harmed non-slipped sardines (sardines collected from the loose pocket of the purse seine). Survival rates were monitored in captivity over 28 days using three replicates for each treatment. The estimated survival of sardines was 43.6% for the non-slipped fish, 44.7% for the modified slipping and 11.7% for the standard slipping treatments. Scale loss indicated the level of physical impact experienced, with dead fish from the non-slipped and modified slipping technique showing significantly lower scale loss than those fish from the standard slipping treatment within the same period. Of the physiological indicators of stress measured, cortisol, glucose, lactate and osmolality attained peak values during slipping and up to the first hours after introduction to captivity. This work indicates that although delayed mortality after release may be substantial, appropriately modified slipping techniques significantly enhance survival of slipped sardines.FCT [SFRH/BPD/116307/2016]; European Commission's Horizon 2020 Research and Innovation Programme [634495