Average Conversion Efficiency Research Articles

Adaptive bicycle: A novel approach to design a renewable and energy-efficient electric bicycle with manual charging

This study focuses on developing an adaptive bicycle prototype with a manual charging mechanism for renewable energy. In response to environmental concerns and the demand for eco-friendly transportation, the research introduces a sustainable approach for short-distance travel. The goal is to demonstrate human power as an effective alternative to non-renewable energy by converting cycling’s rotational force into electrical energy. This energy is stored in a specialized battery and used to power the bicycle with an electric motor’s assistance. The methodology involves constructing and testing a prototype to capture and store energy during pedaling, analyzing mechanical components, electrical conversion, and battery efficiency. Controlled experiments assess the adaptive bicycle’s functionality and effectiveness in self-charging without external power. Results indicate successful integration of the manual charging mechanism with an average energy conversion efficiency of X%. The adaptive bicycle offers a sustainable solution for short-distance commuting, minimizing environmental impact and promoting an eco-friendly mode of travel. This innovative approach highlights the integration of renewable energy into everyday transportation, addressing environmental concerns by reducing dependence on non-renewable sources.

Growth performance and meat quality of finishing pigs fed diets supplemented with antioxidants and organic acids in late summer

Context Heat stress compromises growth performance and meat quality and results in economic losses in pork production. Aims We investigated the effects of supranutritional levels of selenium (Se) and vitamin E (VitE), along with organic acid blends, on the growth performance and meat quality of finishing pigs over a period of weeks during late summer to early autumn in Westbrook, Queensland, Australia. Methods A total of 264 crossbred pigs (25.8 ± 2.4 kg, mean ± s.d.) at 11 weeks of age were randomly assigned in a 2 × 2 × 2 factorial design with two aging times (2 or 5 days) nested within each pig. The factors included antioxidants (Se/E, with recommended or supranutritional doses of Se and VitE), an organic acids (OA) blend added to drinking water (control vs supplemented), and sex (female vs male). Key results Between 16 and 18 weeks of age, high Se/E decreased daily feed intake (P = 0.010) but had no effects on average daily gain or feed conversion efficiency (FCE). Male pigs grew faster (P = 0.040) and had a higher FCE than females (P = 0.050). Supplementation with OA increased FCE in males but not females (OA × Sex interaction, P = 0.035). Between Weeks 16 and 20, male pigs grew faster (P < 0.001), tended to eat more (P = 0.057), and had higher FCE (P = 0.002) than females (P < 0.001). There were no main effects of Se/E or OA on meat quality, except protein oxidation was reduced by high Se/E (P = 0.047). Sex impacted only Warner-Bratzler shear force (WBSF), with male pigs having lower WBSF than females (P = 0.053). Meat aging decreased WBSF (P < 0.001), but it increased cooking loss (P = 0.036), myofibrillar fragmentation index (P < 0.001), lipid oxidation (P < 0.001) and colour parameters (P < 0.001 for all). Conclusions Supplementation with Se/E for up to 10 weeks and OA for 5 weeks did not influence production parameters or pork quality in late summer, except that high Se/E decreased protein oxidation, and significant heat stress conditions were not experienced as expected. Implications Supplementation with Se/E and OA may be effective when environmental temperatures are higher.

The influence of particle oxidation catalyst (POC) mode on emissions reduction of a turbo-charging non-road diesel under wide operating conditions

In the present study, the influence of particle oxidation catalyst (POC) on emissions reduction of a non-road diesel engine is experimentally investigated under wide operating conditions. First, the diesel engine with four POC-aftertreatments (other reactors are kept unchanged) is tested under eight operating conditions non-road steady cycle (NRSC). Then, the diesel engine emissions with best POC-aftertreatment combination and without aftertreatment are comparatively tested under universal conditions. The experiments show that under NRSC, POC-3 which has Pt catalysts with Al2O3 support, asymmetrical channels layout and closed outlet form structure has the best overall exhaust purification, especially for nitrogen oxides (NOx) and particulate matter (PM). The PM conversions efficiency of POC-1, POC-2, POC-3 and POC-4 is 15.3%, 51.7%, 60.9% and 58.8%, respectively under NRSC. The contribution rates of emissions analysis results under NRSC indicated that a single POC mode cannot cover the whole engine operating range. Under universal characteristic test, the brake specific fuel consumption (BSFC) of original engine is a little lower than that of POC-3 in the whole engine operating conditions due to higher exhaust back pressure of POC-3. The engine with POC-3 has very good exhaust conversion efficiencies, the average conversion efficiency of NOx, PM, carbon monoxide (CO), and hydrocarbons (HC) is 96.1%, 51.9%, 77.8%, and 95.6%, respectively. The PM capture efficiency of POC-3 at low load of whole speed range and all load of medium speed are more than 50% compared to other operating conditions. There is little effect on carbon dioxide (CO2) emissions by POC.

An all-silicon design of a high-efficiency broadband transmissive terahertz polarization convertor

Polarization, a fundamental behavior of electromagnetic waves, holds immense potential across diverse domains such as environmental monitoring, biomedicine, and ocean exploration. However, achieving efficient modulation of terahertz waves with wide operational bandwidth poses significant challenges. Here, we introduce an all-silicon polarization converter designed specifically to operate in the terahertz range of the electromagnetic spectrum. Simulation results demonstrate that the average conversion efficiency of cross-linear waves exceeds 80% across a wide frequency range spanning from 1.00 to 2.32 THz, with the highest conversion efficiency peaking at an impressive 99.97%. Additionally, our proposed structure facilitates linear-to-circular polarization conversion with an ellipticity of 1 at 0.85 THz. Furthermore, by rotating the cross-shaped microstructure, active control over arbitrary polarization states can be achieved. To summarize, the proposed structure offers remarkable flexibility and ease of integration, providing a reliable and practical solution for achieving broadband and efficient polarization conversion of terahertz waves.Graphical abstract

A Universal Design Strategy Based on NiPS3 Nanosheets towards Efficient Photothermal Conversion and Solar Desalination

Abstract2D nanomaterials are proposed as promising photothermal materials for interfacial photothermal water evaporation. However, low evaporation efficiency, the use of hazardous hydrofluoric solution, and poor stability severely limit their practical applications. Here, a mixed solvent exfoliation surface deposition (MSESD) strategy for the preparation of NiPS3 nanosheets and NiPS3/polyvinyl alcohol (PVA) converter is successfully developed. The converter is obtained by drop‐casting the NiPS3/PVA nanosheets onto a sponge. The PVA is mainly deposited on the edge of NiPS3 nanosheets, which not only improves the stability of NiPS3 nanosheets, but also adheres to the sponge to prepare a 3D photothermal converter, which shows an evaporation rate of 1.48 kg m−2 h−1 and the average photothermal conversion efficiency (PTCE) of 93.5% under a light intensity of 1 kW m−2. The photothermal conversion mechanism reveals that the energy of absorbed photons in NiPS3 nanosheets can be effectively converted into heat through non‐radiative photon transitions as well as multiple optical interactions. To the best of the knowledge, this is the first report on the application of 2D metal‐phosphorus‐chalcogen (MPChx) for solar desalination, which provides new insights and guidance for the development of high‐performance 2D photothermal materials.

Bimetallic metasurface broadband perfect absorber for high-efficiency thermal photovoltaics

We theoretically propose and demonstrate that broadband polarization-insensitive perfect visible light absorption can be realized in a periodic bimetallic nanotriangle structure with a thick gold plate. The average absorption is 95.79% from 400 nm to 800 nm. The multiple localized surface plasmon resonances of the bimetallic nanostructure are the major contributions to this broadband perfect absorption in the visible region. Meanwhile, the physical mechanism of the broadband perfect absorption of the bimetallic nanostructure can be well interpreted by impedance matching theory. Moreover, the average photo-thermal conversion efficiency is up to 93% over a wide temperature range.

Effect of Dietary Inclusion of Garlic (Allium Sativum) on Feed Intake, Growth Performance and Feed Conversion Efficiency in Goat Kids

Background: With the ban on the use of antibiotics as feed additives and growth promoters in animal nutrition, livestock scientists are now shifting their attention towards natural and safe products like organic acids, probiotics, prebiotics and herbal growth promoters. Plants containing essential compounds can be a cost-effective means of improving efficiency of nutrient utilization and growth performance of animals. The medicinal properties of garlic may have beneficial effects on nutrient utilization and health of animals. However, very few studies have been reported whereby garlic has been fed to ruminants. Therefore, the present study was designed to investigate the effect of dietary inclusion of garlic (Allium sativum) on feed intake, growth performance and feed conversion efficiency in goat kids. Methods: Twelve kids of similar age were randomly allotted to two equal groups (n=6) on basis of body weight. All animals were maintained on common feeding regime consisting of required concentrate mixture and roughage as per requirement given by ICAR (2013). Kids in experimental group were supplemented with garlic @ 250 mg per kg body weight whereas; the control group was remaining unsupplemented. The study was conducted for 90 days. Animals were weighed fortnightly in the morning before offering feed and water. The data on growth rate in terms of body weight, average daily gain, feed intake and feed conversion efficiency were analysed as per standard procedures. Result: The results indicated that overall mean body weight and average dry matter intake were statistically (P greater than 0.05) similar in both the groups. No significant difference was observed in feed conversion efficiency between the treatment groups. The average daily gain was statistically similar in both the groups, but numerically 5.31 per cent increased ADG was observed in garlic fed group. From the results it can be deduced that the garlic supplementation improves average daily gain by 5.31%. However, it has no effect on feed intake and feed conversion efficiency of goat kids.

Effect of Supplementation with Concentrate and Groundnut Haulm in Diets on milk yield of Dairy Azawak cows

An experiment was carried out to determine the effect of feeding diet containing concentrate and graded level of groundnut haulms (GH) on the milk yield of Azawak cattle. Five concentrate-groundnut mixed diets were formulated to contain on average 15% crude protein. The ratio concentrate to groundnut was 100:0; 67:33, 50; 50, 33:67 and 0:100 respectively. Twenty Azawak multiparous lactating cow aged 5-6 years and averagely weighing 317-320 kg were randomly divided into five groups of four animals each and were allotted to the five experimental diets in a randomized complete block design. Data were collected for Dry Matter Intake (DMI), Average Daily Intake (ADI), Average Daily Weight Gain (ADWG), Total Milk Yield, Average Milk yield and Feed conversion efficiency in milk (FCEM) throughout the three months experimental period. Results indicated that the average daily weight gain was higher on diet containing 50% inclusion of groundnut haulm in concentrate diet fed to Azawak cattle. The DMI by cattle was significantly (P˂0.05) higher on diet containing 67 and 100% groundnut haulm. The ADWG of lactating cows fed concentrate mixture was significantly higher on diet containing 33 and 50% inclusion levels but the feed conversion ratio was significantly higher at 50% level of groundnut haulm inclusion level. The total milk yield, average daily milk yield, the body score condition and the feed conversion efficiency in milk were not affected by the level of Groundnut haulms in the concentrate diets, but the highest values of these parameters were obtained at 50% inclusion level. It can be recommended that concentrate diet for Azawak cattle should be supplemented with 50% legume haulm for, better body score condition, feed conversion, feed conversion efficiency of milk and enhanced milk production during the long dry season.

Investigation of neutronic and thermal–electric coupling phenomenon in a 100 kWe-level nuclear silent heat pipe-cooled reactor

Heat pipe-cooled reactors are attractive because of their compact structure, high power capacity and reliability, and inherent safety features. These reactors are distinguished by the use of high-temperature heat pipes that directly bridge the reactor core and energy conversion devices, thus creating a tightly knit modular system. However, comprehensive coupled analysis of these reactors remains challenging because of the intricate multiphysics interactions involved. To address this, the neutronic and thermoelectric coupled phenomena of heat pipe-cooled reactors are investigated in this study. Models are introduced for the point reactor kinetics, core heat transfer, channel heat transfer, two-phase two-dimensional heat pipes, thermoelectric coupling, and cold plates. The channel heat transfer is refined in a 100 kWe-level nuclear silent heat pipe-cooled reactor and a model for the three-dimensional heat transfer process in its thermoelectric matrix established, which effectively resolves the calculation distortions of the lumped model. The maximum deviation between the calculation results from the proposed model and the verification data for a full-system coupled computation is less than 10 K. The core temperature difference from the three-dimensional model is five times that of the lumped model with a maximum average fuel temperature difference of 225.7 K. The maximum and average thermoelectric conversion efficiencies are 15.56 % and 14.43 %, respectively. The failures of one, five, and nine heat pipes are analysed. The failure of a single heat pipe has negligible effects with a peak fuel temperature surge of only 121 K. In contrast, a failure involving nine heat pipes leads to a peak fuel temperature spike of 778 K and a 47.1 % increase in the maximum heat transfer power, marking a critical operational threshold. It is therefore imperative to consider the safety margin in the potential failure of multiple central heat pipes during the preliminary design stages.

Reduction of the initial defects generated during casting of quasi-single crystalline silicon by reserving gaps between seed crystals

The presence of dislocation is a significant impediment to enhancing the quality of quasi-single crystalline silicon cast by seed-assisted directional solidification. A novel approach was proposed to reduce dislocations in G7 166-type silicon ingots, especially in the region of seed crystal seams, by reserving seed crystal gaps during loading. We calculated that the seed crystal's linear thermal expansion after heating from 298.15 to 1683.15 K was 0.9 mm. However, in consideration of the actual deviation in seed processing and measurement, we increased the gap between seeds to 1.2 mm to prevent compressive stress on all 49 seed crystals. The actual residual seed gap measured after ingot casting was approximately 0.325 mm, which is relatively close to the calculated value. It was discovered that the average defect ratio in the silicon blocks decreased from 26.95% (without gaps) to 6.79% (with 1.2 mm seed gaps) for the proposed method. This indicates that a portion of the dislocation source was reduced by reducing compressive stress caused by linear expansion between adjacent unmelted seeds. The average conversion efficiency of the solar cells prepared using the gapless seed method for p-type polycrystalline cells is 22.03%, whereas the novel approach resulted in an average cell efficiency of 22.22%, featuring a higher proportion of high-efficiency sections.

New attempts on acidic anaerobic digestion of poly (butylene adipate-co-terephthalate) wastewater in upflow anaerobic sludge blanket reactor

Poly (butylene adipate-co-terephthalate) (PBAT) wastewater is a highly concentrated, acidic, and toxic wastewater generated from biodegradable plastics production. Large amounts of alkali would be consumed when treating PBAT wastewater by anaerobic digestion due to the low pH value. This study employed acidic anaerobic digestion to treat PBAT wastewater and compared to neutral anaerobic digestion. The results indicated that the COD removal rates in the acidic upflow anaerobic sludge blanket (UASB) reactor were 65.5% and 59.9%, respectively at influent pH 6.0 and 5.0 with the COD concentration of around 11,000 mg L−1, and the methane conversion efficiency were 172.5 and 183.8 mLCH4/gCODr (gCODr: COD removed amount), respectively. Correspondingly, the average COD removal and methane conversion efficiency in the neutral UASB reactor were 63.2% and 188.0 mLCH4/gCODr, respectively. The treatment efficiency of acidic and neutral UASB reactors for PBAT wastewater was similar. The hydrogenotrophic methanogenic activity was further enhanced in the acidic UASB reactor compared to the neutral one. The increase of alkalinity in the acidic UASB reactor (2.4 mmol L−1) was higher than the neutral (2.0 mmol L−1). A higher level of syntrophic acetate oxidation bacteria and hydrogenotrophic methanogen was enriched in the acidic UASB reactor, ensuring efficient treatment and saving costs.

Realizing ultrahigh ZT value and efficiency of the Bi2Te3 thermoelectric module by periodic heating

Thermoelectric power generation is regarded as a promising technology to convert waste heat into electricity. This study aims to address the low conversion efficiency of thermoelectric modules and introduces a novel periodic heating method to enhance their performance. Two new indicators, time average ZTta value and effective conversion efficiency, are introduced to assess the dynamic behavior of thermoelectric modules. A Bi2Te3-based thermoelectric module with n-type Bi2Te3-xSex and p-type BixSb2-xTe3 materials is adopted as the research objective and tested on a designed transient experimental setup. Besides, a transient numerical model is developed to explore the optimal transient heat source and study the effect of various parameters on dynamic behavior. Compared with the steady-state efficiency of 3.76% and ZTta value of 0.78 at a heat supply of 60 W, the time average efficiency and ZTta value are improved by 52.93% and 43.59% respectively using the periodic heating method. Also, a smaller leg height, a larger leg area, more TE couples, and lower thermal conductivity are suggested for improving the dynamic behavior. This work offers a new periodic heating method to improve the output performance of thermoelectric modules, which may promote the broader application of thermoelectric power generation technology.

Effect of dietary supplementation of inulin with low and high concentrate diet on growth performance and nutrient digestibility in Barbari goats

This study aimed to determine the effect of dietary supplementation of inulin on growth performance, feed conversion and nutrient digestibility in Barbari goats fed high and low concentrate diet for a period of 90 days. Twenty four yearling female Barbari goats were randomly divided into four equal groups (n=6) according to average body weight (18.24±1.16 kg). Treated animals in Group 1 were fed low concentrate diet (LCD; concentrate roughage ratio 40:60) and Group 2 (LCIN) with 2% inulin supplementation (% DM basis). Similarly, Group 3 was fed high concentrate diet (HCD; concentrate roughage ratio 60:40) and Group 4 (HCIN) with 2% inulinsupplementation. Results showed that average daily gain (ADG) and feed conversion efficiency (FCE) were higher in inulin supplemented groups than the non-supplemented group. There was no increase in mean live body weight (BW) and dry matter intake (DMI) with inulin supplementation either in LCD or HCD treatment groups.The mean body condition score (BCS) was also similar in all groups. However, faecal score (FS) was superior in inulin supplemented group observed after 30 days of feeding trial. There was significant improvement in the digestibility coefficient of crude protein and DCP intake. It was concluded that inulin supplementation either in high concentrate and low concentrate diet of growing goats resulted in improvement in growth performance, faecal score and nutrient digestibility.

From Theory to Practice: A Sustainable Solution to Water Scarcity by Using a Hybrid Solar Distiller with a Heat Exchanger and Aluminum Oxide Nanoparticles.

The study presently conducted focused on analyzing a solar-powered desalination setup that had a double slope. It can recycle blackish water into drinking water with solar energy. Not only does this result in a significant decrease in carbon emissions but it also represents an environmentally beneficial alternative that is particularly suited for arid locations that are lacking of electrical infrastructure. This system was equipped with a PVT system which makes the system self-sustainable and a CPC collector and implemented the use of aluminum oxide (Al2O3) nanoparticles to enhance its energy efficiency. Energy matrices, economic analysis, and life cycle conversion efficiency were evaluated. The study was conducted annually in New Delhi, with input data provided by IMD in Pune, India. MATLAB was used for the analytical calculations. Energy and exergy were utilized to determine the average annual energy output, which was found to be 8.5%. Additionally, the average energy payback time was calculated to be 16.16%, the average energy payback factor was 13.91%, and the average life cycle cost conversion efficiency was 7.15% higher. The proposed system demonstrated superior performance compared to the previous system in terms of annual yield, energy payback time (EPBT), efficiency of life cycle cost (LCCE), and factor of energy payback (EPBF). The hybrid system has the potential to meet the future demand for potable water and become self-sustainable.

Waste management of solar cells in South Asia: an environmental concern of the emerging market.

The share of solar energy in the energy mix has become a major concern, and the global effort is to increase its contribution. Photovoltaic technology is an environment-friendly way of electricity production compared to fossil fuels. Currently, third generation of solar cells with a maximum average conversion efficiency of 20% has been achieved. Asia is an emerging market for photovoltaic technology, and it has recorded the highest installation capacity for 2018 (280 MW), 2030 (1860 MW), and 2050 (4837 MW). Meanwhile, Asia is estimated to be the highest producer of PV waste by 2040, with 5,580,000 metric tons of waste volume. Solid waste management is already a big environmental issue in South Asian countries, and untested landfilling of solar cells can further increase the burden. This review emphasizes the end-of-life scenario of solar cells in developing South Asian countries. Solar cell waste is hazardous e-waste that can lead to environmental and health impacts if not managed properly. It consists of metals with market value, which can be waste or gold, depending on its management. The study finds that recycling is the economically and environmentally effective waste management option for solar cells in South Asia. This paper reviews the deficiencies in the existing solar cell waste management framework in South Asian countries. Moreover, practical implications are presented for designing an effective waste management plan for solar cells in South Asian countries. Strong legislation, sufficient recycling infrastructure, and high stakeholders' interests are required to resolve this environmental concern.

Comparative analysis of photovoltaic thermoelectric systems using different photovoltaic cells

The photovoltaic-thermoelectric (PV-TE) system has emerged as a focal point in research endeavors aimed at harnessing the full spectrum of solar energy and enhancing the efficacy of solar power generation. Owing to the variations in bandgap and inherent material properties across diverse photovoltaic cells, the capacity to utilize the solar spectrum of PV-TE systems can be significantly affected when using different photovoltaic cells. Historically, investigations into the influence of photovoltaic cells on PV-TE systems have been predominantly rooted in theoretical simulations. These examinations have primarily concentrated on the holistic system efficiency under varying temperature conditions. In this study, we integrated three distinct types of photovoltaic cells into PV-TE systems. Both simulation and experimental methodologies were employed to evaluate the impact of these photovoltaic cell types on the PV-TE systems' performance. Additionally, we compared the back temperatures of standard PV systems with those of PV-TE systems. The average photovoltaic conversion efficiencies of PV-TE systems equipped with CIGS, CdTe, and a-Si photovoltaic cells were 21.9%, 19.7%, and 12.7%, respectively. Meanwhile, the average efficiencies of TEG were 0.256%, 0.102%, and 0.083% respectively, with average backplate temperatures of 39.3 °C, 44.0 °C, and 40.5 °C. The temperature disparities between the back of standard photovoltaic systems and PV-TEG-PCM systems stood at 4.70 °C, 2.32 °C, and 3.43 °C, respectively. Notably, CIGS photovoltaic cells, which harness a specific range of the solar spectrum more effectively, showcased superior performance. Furthermore, a broader usable solar spectrum band for a PV cell doesn't always translate to enhanced performance. These findings offer valuable insights for optimizing the power generation capabilities of photovoltaic-thermoelectric systems leveraging full-spectrum solar energy.

Research on cross sensitivity of NOx sensor and Adblue injection volume in accordance with the actual situation based on cubature Kalman filter

Due to the nitrogen oxide (NOx) sensor's cross-sensitivity and inability to monitor ammonia coverage, it is critical to eliminate these flaws for a significant percentage of in-use diesel vehicles without NH3 sensors. In this study, a platform for multi-model co-simulation was established. The results showed that the downstream NOx concentration of the selective catalytic reduction (SCR) could be more accurately calculated using the filtering model based on cubature Kalman filter (CKF). Under European Steady-State Cycle (ESC) and European Transient Cycle (ETC), the prediction errors of the filtering model based on CKF were 4.6% and 7.7%, respectively. Under ESC, compared with the old control strategy, the prediction accuracy of temperature model of the new control strategy was increased by 2.6%, the average Adblue injection rate was increased by 9.1%, and the average NOx conversion efficiency was increased by 4.3%. Under ETC, the prediction accuracy of the temperature model of the new control strategy was increased by 2.5%, leading to a high average NOx conversion efficiency of 87.9%. Regarding the old control strategy, although the average NOx conversion efficiency reached 92.1%, the average ammonia slip concentration exceeded the threshold (10 ppm) by more than five times.

Optimal sizing design of the hydrogen-based system for the stand-alone island

The main barriers to using Renewable Energy Sources (RES) to generate electricity are intermittency with low penetration in the electricity network and high seasonal demand fluctuation. An optimum hydrogen-based system configuration is designed for absorbing the maximization of RES curtailments using water electrolysis to produce and store hydrogen. This paper also developed a simulation model to optimize the proper size of electrolyzers and other parameters of the whole system. In order to validate the model, a hybrid electricity network for relatively stand-alone islands, located in eastern coastal China, has been used as a case study. Our analysis showed that the sizing of the required electrolyzer was determined by the operational temperature, the cell U-I curves, and the input of usable RES curtailments. For the application, a large amount of available hydrogen could be produced from the RES curtailments with an average conversion efficiency higher than 75.4%. And almost half of the rejected RES energy (54.7%) was returned to the electrical network through fuel cell stacks during high demand periods.

Experimental validation and numerical assessment of a temperature-controlled thermoelectric generator concept aimed at maximizing performance under highly variable thermal load driving cycles

Although the internal combustion engine (ICE) dominance in mobility is being challenged, ICE R&D enables a non-disruptive transition towards sustainable transportation through hybridization and carbon neutral fuels. The efficiency improvement of ICE-based mobility through Waste Heat Recovery (WHR) is thus a priority, especially in the area of hybrid, plugin hybrid and long-haul transportation, where the recovery potential is high, and ICEs will still be used for a long time. Thermoelectric (TE) Generators (TEGs) have been assessed as a possible low maintenance WHR solution for long. However, viable market solutions are still not a reality. While material costs are steadily being overcome with novel affordable TE materials, there is still the issue of low average conversion efficiency under realistic driving conditions. This is caused by the fact that the efficiency of TEGs is further deprecated by the big challenge of thermally optimizing the TEGs under highly variable conditions of exhaust flow rate and exhaust temperature during real-world driving. This thermal optimization mainly means that the hot side temperature should be as close as possible to the maximum allowable temperature of the modules, but not higher.The authors have been exploring exhaust heat exchanger (HX) concepts that allow achieving this thermal optimization under highly variable thermal loads by using phase change. The strategy used incorporates the spreading of excess heat along the HX by variable conductance heat pipes (VCHPs) embedded in it, thus enabling to maximize the energy conversion without thermal dilution under low thermal loads or overheating risk under high thermal loads. This was done by pre-regulating the pressure of the non-condensable gas (NCG) present inside the VCHPs so that these devices would start performing the spreading of excess heat from over-heated to under-heated regions of the HX at a precise phase change temperature, optimized to the optimal thermal level of the thermoelectric generators.The merit of the aforementioned strategy was confirmed through modelling and illustrated in previous work. The scientific novelty of present study relatively to previous work by the authors or other researchers is that it finally provides a full experimental validation of this concept with two different prototypes attached to a light duty engine. The experimental proof-of-concept results were successfully compared against predictions. Finally, theoretical performance analysis of the impact of the application on a light duty vehicle in terms of fuel economy and GHG emissions during the WLTC class 3 b was assessed with the help of driving cycle and engine simulations performed with AVL Suite software.The unique heat spreading and temperature control features of the concept were confirmed experimentally. In addition, predictions made by the model were far beyond the current state of the art for light duty automotive TEG generators. Namely, maximum output powers exceeding 2 kW and 1.2 kW were predicted during the WLTC cycle when using commercial bismuth telluride and the silicide-Tetrahedrite modules explored by the authors, respectively. Average fuel/CO2 savings of 4% were predicted for the WLTC cycle, with these savings raising to 12% during the highway portion of the cycle. This unparalleled performance is explained by the possibility of achieving both an optimized hot face temperature and a high heat exchanger effectiveness even under highly variable thermal loads.

PEI-GOs/PVA photothermal sponge with enhanced interfacial solar steam generation and seawater desalination

Solar water evaporation technology based on photothermal materials is regarded as one of green and critical technologies for addressing freshwater scarcity. However, practical application of photothermal materials is limited by their high preparation cost, low evaporation efficiency, and poor photothermal conversion. In this study, a facile sponge with excellent photothermal and mechanical properties has been fabricated by mechanical-mixing and chemical-crosslinking of polyethyleneimine modified graphene oxide nanosheets (PEI-GOs), formaldehyde, polyvinyl alcohol (PVA) and sulfuric acid catalyst. The as-prepared PEI-GOs/PVA sponge shows excellent light absorption (95.1 %) under standard sunlight intensity of 1.0 sun (1 kW m−2) and a wide wavelength range of 200–2500 nm. The achieved high evaporation rate (1.80 kg m−2 h−1) is 4.7 times those of pure water (0.38 kg m−2 h−1). Moreover, the simulated seawater desalination experiment shows that the sponge has a good long-term stability and an average photothermal conversion efficiency of 88.5 %. The water purified by the sponge exceeds the quality of urban daily water. Therefore, this study offers a new facile route for fabricating a kind of photothermal sponge with good light absorption capacity, and water evaporation properties, which has potential application in seawater desalination.