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This paper proposed one novel Thermo-Electric Ventilation (TEV) system driven by the concentrated photovoltaic-thermoelectric generator (CPV-TEG), which could use the electric power converted directly from solar energy by CPV-TEG. The effects of incident solar irradiance, number of thermoelectric generators, and ambient air temperatures on the power output of CPV-TEG have been analytically investigated through energy balance and first law of thermodynamics. Furthermore, input current and number of thermoelectric coolers were sensitively varied to optimize the performance of TEV system respectively in heating and cooling modes. Finally, an integrated theoretical and numerical approach was proposed to match the power output of CPV-TEG with the power input of TEV. Modeling results indicate that the output power from CPV-TEG could satisfy the energy demand of TEV system when the input currents of thermoelectric coolers were no more than 2.5 A and 2.8 A respectively for cooling and heating modes. Minimum energy and exergy efficiencies of the system in winter heating mode were confirmed to be 1.67 and 0.24 respectively, which were far higher than that in summer cooling mode. This research may be helpful for enhancing performance and reducing exergy destruction of thermoelectric ventilation system, simultaneously. • A thermoelectric ventilation system driven by photovoltaic-thermoelectric generators was proposed. • Thermodynamic model jointly with energy and exergy analysis fully predicts system performance. • Parameters of thermoelectric ventilation system were identified for improving overall system design. • Performance enhancement and exergy reduction could be simultaneously achieved by strategy operations. • Proposed thermoelectric ventilation system could be an alternative solution for green buildings operation. [ABSTRACT FROM AUTHOR]

In order to effectively harvest solar energy and waste thermal, pulsating heat pipes (PHPs) could be utilized to promote the hot end temperature of the thermoelectric modules (TEMs) and thus enhance its conversion efficiency. This paper explored a novel approach of recovering low grade energy and conversion to electricity utilizing PHP assisted with TEG. This research fully analyzed the effects of various working fluids, input powers, filling ratios, inclination angles and air velocities on the thermo-hydrodynamic and electricity conversion performance of PHP-TEG hybrid system. Our results demonstrated that the peak-to-peak amplitude of output voltage mainly depends on heat inputs and working fluids, and independent of the filling ratios; the inclination angle (from 30° to 90°) has slight effects on the heat transfer performance and thermoelectric generation of PHP-TEG system, due to the advantages of surface tension. In addition, the inlet temperature and flow velocity of cooling water on the thermal recovery efficiency and thermo-electricity conversion performance were further investigated. These results indicated the best heat recovery performance of 80.12% and the maximum thermoelectric conversion efficiency of 1.22% were achieved simultaneously at the situation of 10 °C and 600 mL/min of cooling water. Present investigation could contribute to waste thermal recovery and electronic cooling applications. • A system with pulsating heat pipe (PHP) and thermoelectric generator (TEG) was developed. • Maximum output power was highly dependent on the thermal performance of PHP. • The best performance of this TEG-PHP system mainly depended on working fluid and filling ratio. • Inclination angle has slight influence on the comprehensive performance of PHP-TEG system. • This novel system of TEG-PHP could facilitate efficiently exploitation of solar energy. [ABSTRACT FROM AUTHOR]

Annular thermoelectric power generator has been increasingly considered in application of ambient energy harvesting owing to the advantages of simple structure and no pollution. To improve thermal stability and energy harvesting performance of this system, the latent heat of phase change materials to improve thermal management and the high thermal conductivity of the heat sink to enhance heat transfer with the ambient are harness to annular thermoelectric power generator. Motivated by this, a phase change material based annular thermoelectric energy harvester (PCM-ATEH) with fins is developed for ambient energy harvesting and its three-dimensional transient model is also built up through jointly with thermo-electric and phase change processes. This paper considers the influence of key parameters such as temperature fluctuation amplitude, temperature fluctuation period, height ratio of PCM and thermoelectric generator (TEG) and melting temperature on liquid fraction, temperature difference, voltage and power density. Moreover, the comparison of PCM-ATEH and PCM based thermoelectric energy harvester (PCM-TEH) with/without fins is further conducted in this study to explore thermal management and energy harvesting performance. The energy harvesting characteristics of PCM-ATEH with fins is developed concerning the combination of power generation of TEG and melting process of PCM. Based on the results, it is found that the temperature difference and power density of PCM-ATEH with fins vary periodically with the sinusoidal temperature boundary, and results show that increasing temperature fluctuation period is not always feasible. Additionally, the comparative results indicate that the peak power density and energy efficiency of PCM-ATEH with fins are increased by 0.126 W/m2 and 0.02 % compared with PCM-TEH with fins, and increased by 0.195 W/m2 and 0.041 % compared with PCM-ATEH without fins. The results of energy harvesting characteristics show that a maximum of 0.77$ per watt can be reached to power generation cost of PCM-ATEH with fins. This paper can provide theoretical guidance for thermal management and energy conversion of energy harvesting system. [ABSTRACT FROM AUTHOR]

Annular thermoelectric power generator has been increasingly considered in application of ambient energy harvesting owing to the advantages of simple structure and no pollution. To improve thermal stability and energy harvesting performance of this system, the latent heat of phase change materials to improve thermal management and the high thermal conductivity of the heat sink to enhance heat transfer with the ambient are harness to annular thermoelectric power generator. Motivated by this, a phase change material based annular thermoelectric energy harvester (PCM-ATEH) with fins is developed for ambient energy harvesting and its three-dimensional transient model is also built up through jointly with thermo-electric and phase change processes. This paper considers the influence of key parameters such as temperature fluctuation amplitude, temperature fluctuation period, height ratio of PCM and thermoelectric generator (TEG) and melting temperature on liquid fraction, temperature difference, voltage and power density. Moreover, the comparison of PCM-ATEH and PCM based thermoelectric energy harvester (PCM-TEH) with/without fins is further conducted in this study to explore thermal management and energy harvesting performance. The energy harvesting characteristics of PCM-ATEH with fins is developed concerning the combination of power generation of TEG and melting process of PCM. Based on the results, it is found that the temperature difference and power density of PCM-ATEH with fins vary periodically with the sinusoidal temperature boundary, and results show that increasing temperature fluctuation period is not always feasible. Additionally, the comparative results indicate that the peak power density and energy efficiency of PCM-ATEH with fins are increased by 0.126 W/m2 and 0.02 % compared with PCM-TEH with fins, and increased by 0.195 W/m2 and 0.041 % compared with PCM-ATEH without fins. The results of energy harvesting characteristics show that a maximum of 0.77$ per watt can be reached to power generation cost of PCM-ATEH with fins. This paper can provide theoretical guidance for thermal management and energy conversion of energy harvesting system. [ABSTRACT FROM AUTHOR]

The published literature focuses on the electrical performance of thermoelectric envelope and scarcely investigates its impact on indoor cooling and heating loads, which cannot comprehensively reflect the energy saving potential of thermoelectric envelope. In this work, a solar thermoelectric wall with phase change material (STEW-PCM) is developed to investigate its potential for power generation round-the-clock and its influence on the indoor thermal environment in the subtropical climate. Sensitivity analyses have been conducted to characterize the matching relationship between PCM parameters (melting temperature, latent heat and thickness) and the proposed system. Meanwhile, the energy saving potential of STEW-PCM system is forecasted in terms of annual electrical energy, environmental benefit and cooling load. The results show that STEW-PCM system has the potential of power generation round-the-clock judging from the temperature and output voltage. The annual electrical energy of STEW-PCM system can reach 1740.66 kJ/(m2·year), corresponding to Levelized Cost of Electricity (LCOE) of 35.37 c$/kJ and CO 2 saving cost of 6.74 $/(m2·year). The cooling load can be effectively reduced by more than 25% with STEW-PCM system in the subtropical climate. This paper will be helpful to understand the dynamics characteristics of a solar thermoelectric wall with PCM for harvesting energy from environment. • Round-the-clock power generation of STEW-PCM is proposed for green buildings. • A numerical model is developed to explore the dynamics characteristics of STEW-PCM. • Influence of melting temperature, latent heat and height of PCM is determined. • The energy distribution of STEW-PCM for the three working modes is analyzed. • The annual energy saving potential of STEW-PCM are comprehensively performed. [ABSTRACT FROM AUTHOR]

Phase change materials (PCM) are widely seen as a cooling medium in thermoelectric systems capable of effectively reducing the hot end temperature of thermoelectric device and improving energy conversion efficiency. In this study, a comprehensive numerical model is developed to investigate the active cooling performance of a PCM-based thermoelectric device where the phase-change dynamics and thermoelectric conversion physics take place simultaneously. The dynamic changes of key parameters, such as hot and cold end temperatures of thermoelectric device, liquid fraction of PCM over time under typical operating conditions are simulated to better understand the dynamic characteristics of the PCM-based thermoelectric device. The thermoelectric operating current, cooling load, component height ratio and PCM melting temperature have been parametrically swept to evaluate their effects on the system's cooling performance. And then a comparison analysis on active cooling potential of thermoelectric device with and without PCM is performed in terms of the energy and exergy efficiencies. Furthermore, temperature distribution and cooling region of PCM-based thermoelectric device are sensitively determined to better reveal their dynamic matching mechanism. Numerical results demonstrated that the cooling time of the PCM-based thermoelectric device has been obviously extended due to the constant maintenance in the cold end temperature of thermoelectric device during phase change period. The energy and exergy efficiencies of the PCM-based thermoelectric device are found to be 30.08%, 402.08% greater, respectively, than that of the thermoelectric device without PCM when the time is 20 s. Present research could be beneficial for cooling performance improvement of the thermoelectric-phase change coupling processes. • A comprehensive numerical model is developed for PCM-based thermoelectric devices. • Dynamic characteristics of a PCM-based thermoelectric device were conducted. • Effects of main parameters on system performance were sensitively identified. • Comparison analysis on efficiency improvement potential with and without PCM is preformed. • Coordinated coupling relationship between the thermoelectric conversion and phase transition processes are determined. [ABSTRACT FROM AUTHOR]