He, Z. (Zhineng)

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    Thermoelectric active window frame: Constructive integration and preheating analysis
    (Elsevier, 2024) He, Z. (Zhineng); Sacristán-Fernández, J.A. (José Antonio); Martín-Gómez, C. (César); Vidaurre-Arbizu, M. (Marina); Zuazua-Ros, A. (Amaia); Arias-Salazar, P. (Pablo)
    Building heating and cooling systems using thermoelectricity appear to be a feasible alternative, as it presents several features including versatility and high reliance. While most applications of thermoelectricity in buildings are found in wall systems, window integration shows excellent potential for enhancing the thermal performance of buildings at the façade level, compensating heat losses that take place in windows. Combining energy efficient ventilation with heat recovery leads to a significant reduction of the required energy, keeping desired comfort conditions inside buildings. Thus, the following study presents the design of an active window frame with an integrated thermoelectric system, attaining two functions: pre-heating the supply air, while simultaneously recovering the waste heat energy from exhaust air. Two full-scale prototypes were built, each featuring a different airflow pattern, and preliminary tests for heating mode were carried out under laboratory conditions. The results revealed a similar performance comparing both prototypes, achieving a COP ranging 1.56 to 2.71 for prototype A, while prototype B ranged from 1.62 to 2.65. The results showcase superior heating efficiency compared to a previous experiments conducted by the research group, where a maximum COP of 1.91 was achieved. From a building perspective, wider adoption of thermoelectricity applied to thermal conditioning is hindered by lack of suitable products for architectural integration. Therefore, the system's innovation stems from optimized design, integrated construction, and industrialized production, enhancing energy efficiency in buildings via a compact façade integrated system without space compromise.
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    Thermoelectric system applications in buildings: A review of key factors and control methods
    (Elsevier, 2023) He, Z. (Zhineng); Martín-Gómez, C. (César); Zuazua-Ros, A. (Amaia)
    A low coefficient of performance (COP) limits the development of thermoelectric (TE) systems in buildings. However, considering their good integration with solar systems and budling structures, there is good application potential for TE systems in buildings. In many previous works, control systems indeed help TE systems to improve their performance. Therefore, the objective of this work is to analyze and summarize key factors in the control process and control methods for designing and optimizing the control systems for TE systems in buildings. This work reviews relevant publications from 2000 to 2022 on control applications of TE systems in different fields and groups them into key factors and control methods. The analysis of the key factors indicates the power strength of Peltier cells, the number of working Peltier cells, the temperature difference between the cold and hot sides, and the temperature difference between the object side and the indoor space as significant factors. Additionally, the most relevant control methods for the operating voltage or current are also classified. It is crucial to appropriately adjust these key factors using suitable control methods to achieve improved COP. Regarding the control application of TE systems in buildings, this is an issue that has not been studied with specific attention. Therefore, the analysis of key factors and control methods is meaningful for control systems to improve the performance of TE systems in buildings, especially under dynamic operating conditions of the built environment.
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    Current-dependent temperature change model of a thermoelectric window frame
    (Elsevier, 2024) He, Z. (Zhineng); Martín-Gómez, C. (César); Zuazua-Ros, A. (Amaia)
    Compared to conventional air-conditioning systems, Thermoelectric (TE) window systems exhibit a lower coefficient of performance (COP). To improve their COPs for practical use, it is essential to establish and validate a numerical model for optimizing the system in the pre-design phase. This work develops a thermoelectric window frame (TEWF) and validates its current-dependent temperature change model based on experimental results. The TEWF is integrated as an auxiliary window frame to address the limitations observed in existing TE window systems and its model enables simulations of the operation of the TEWF under various operating currents without the assumptions of the object-side temperature, the temperature difference between the two sides, or the desired supply air temperature. The results indicate that as the operating current increases, the hot-side temperature exhibits a more significant rise than the cold-side temperature, resulting in an increasing temperature difference between the hot and cold sides. Simultaneously, both thermal capacities at the hot and cold sides demonstrate a growing trend. However, the COP on both sides drops with the increasing current. Most variables in the simulation exhibit errors of less than 5% compared to the experimental results under identical conditions. Furthermore, their CV (RMSE) values all comply with the acceptable tolerances of 15% according to the ASHRAE 14 and FEMP standards. Therefore, the proposed current-dependent temperature change model of the TEWF demonstrates good accuracy and proves helpful in optimizing TE systems by simulating their thermal behavior under different operating conditions.