Experimental investigation of desiccant dehumidification based thermoelectric air-conditioning system

Vapor compression refrigeration system (VCRS) based conventional cooling systems run on the high amount of electricity and refrigerants responsible for greenhouse emissions. To save the environment and high-grade energy, traditional cooling systems should be replaced with some environment-friendly alternative. This paper proposed alternative eco-friendly air-conditioning systems based on an amalgam of two different technologies, i.e., desiccant dehumidification and thermoelectric (TE) cooling. The proposed air-conditioning system has the following subprocess: dehumidification of moist air by the solid desiccant wheel, cooling of processed air by TE modules, and regeneration of desiccant wheel by an electric heater and waste heat from TE modules. The air conditioning system has been experimentally studied for cooling performance, cooling effect, and energy input. The maximum coefficient of performance of 0.865 can be achieved with the proposed system, and it can be used for cooling effects up to 1442.24 W to maintain the human comfort condition in the chamber i.e. approximately 22 ℃ and RH 50% defined by ASHRAE.

Design of a thermoelectric energy source for water pumping applications: A case study in Sharjah, United Arab Emirates

<p>There are many water pumping power systems that exist nowadays relying on conventional and renewable energy sources such as mechanical windmills, solar photovoltaic (PV) panels, wind turbines, and diesel generators. Few designs utilize thermoelectric modules for the purpose of enhancing the reliability and the performance of the system in order to provide water supply to isolated zones continuously. The use of thermoelectric (TE) modules is increasing due to their reduced prices and the possibility of using them in different applications depending on the required specifications of motors and other connected loads. This paper proposes a renewable energy system design for water pumping applications in Sharjah (Latitude 25.29°N and Longitude 55°E), United Arab Emirates. The system involves TE modules for operating the three-phase AC water pumping motor, voltage regulator, voltage boost converter, and three-phase power inverter while considering the changes of temperature values which affect the performance of the thermoelectric generator (TEG) modules. The aim is integrating TEG modules to cover the increasing demand of water in rural areas since rainy days in Sharjah are limited and the temperature is high. The performances of the proposed system will be demonstrated using Simulink simulations for the overall blocks of the proposed system.</p>

Solar-Powered Thermoelectric-Based Cooling and Heating System for Building Applications: A Parametric Study

Thermoelectric (TE) based cooling and heating systems offer significant advantages over conventional vapor compression systems including no need for refrigeration or major moving parts, high controllability, and scalability. The purpose of the present study is to provide an energy and economic assessment of the performance of a TE-based radiant cooling and heating system for building applications. It is considered that TE modules are integrated in the ceiling to lower/increase the ceiling temperature through the Peltier effect during the hot/cold season to provide thermal comfort for the occupants via radiation and convection. The study explores the possibility of using rooftop PV panels to produce electricity required for the operation of TE modules. An actual office building located in Melbourne, FL, USA is considered for a test study, and the hourly cooling and heating loads of the building are calculated through building energy simulation in eQuest. Various operating conditions, including different input voltages and temperature gradient across TE modules, are considered, and the system is sized to properly address the year-around cooling/heating demand. It is shown that a nominal cooling capacity of 112.8 W and a nominal PV capacity of 31.35 W per unit area of the building is required to achieve the target goal when the system operates at the optimal condition. An economic analysis is also performed, and estimated cost, as well as potential savings, are calculated for each operating condition. The optimal operating condition with minimum cost is selected accordingly. The results demonstrated that the initial cost of the proposed system is considerably higher than conventional heating/cooling systems. However, the system offers other benefits that can potentially make it an attractive option for building cooling/heating applications.

Influence of structural factors on thermal stress in skutterudite-based thermoelectric module

Thermoelectric (TE) modules for power generation usually operate under high temperatures and large temperature differences, which inevitably introduce thermal stress in the modules. Suppressing the thermal stress is then one of the important issues for improving the service reliability of TE modules. In the past decades, various approaches have been developed for the design optimization of TE module primarily being focused on the enhancement of conversion efficiency, while the influence of structural factors on the module’s mechanical reliability is often overlooked. In this work, we proposed a multi-objective optimization strategy by using the finite element method to evaluate the structural reliability of a TE module, which integrates the module mounting mode, configurational structure of ceramic substrates, thickness of ceramic substrates and electrodes, cross-sectional shape of TE legs, and gaps between [Formula: see text]- and [Formula: see text]-type legs. As a typical sample, the thermal stress of an 8-pair skutterudite (SKD)-based TE module with the framework dimensions of 20 × 22 × 12 mm3 was well studied under the service conditions. The results reveal that a split structure of ceramic substrates and a pressing mounting mode with 2 MPa pressure on the module’s hot-side can significantly reduce the thermal stress in the module. Meanwhile, increasing the gap distance between [Formula: see text]- and [Formula: see text]-type legs, rounding the square column shaped legs, using thin ceramic substrate and thick electrode also can relieve the thermal stress somewhat. The simulation gives a comprehensive solution to reduce the thermal stress and enhance the module’s service reliability for the practical applications through structure optimization.

Numerical Analysis and Parametric Study of a Thermoelectric-Based Radiant Ceiling Panel for Building Cooling Applications

Buildings are known as one of the foremost energy consumer sectors in the world with a share of nearly 40% and hence the design and development of clean and energy efficient building energy systems is an important step towards a sustainable future. Cooling and air conditioning systems, as an essential component for occupants’ comfort, are among the largest energy end-users in buildings. Additionally, most air conditioning systems rely on using refrigerants that are harmful for the environment with considerable potential for ozone depletion and global warming. Solid-state cooling technologies that do not require refrigerant are therefore of interest to eliminate these environmental concerns. Thermoelectric (TE) modules, as a solid-state cooling technology, when supplied by DC electricity, produce a temperature gradient through the Peltier effect that can be used for cooling purposes. Due to the attractive characteristics that TE technology offers, mainly high controllability, lack of refrigerant and large moving parts, quiet operation, promising efficiency and requiring minimum maintenance required, TE-based systems are becoming an emerging technology for building cooling applications. TE-based cooling technologies have been developed and tested through integrated and non-integrated systems in the building envelope. In the present paper, the design of a TE-based radiant cooling ceiling panel is investigated through numerical modeling and parametric study. The system can be incorporated in the ceiling and will maintain a reduced ceiling temperature to provide cooling through radiation and convection for the occupants. COMSOL Multiphysics is used for modeling and simulation purposes and the performance of the system under various configurations is assessed. The effect of number and placement of TE modules for a given size of ceiling panel are investigated using several simulations in COMSOL to achieve a desired and uniform surface temperature in the minimum amount of time. The impact of incorporating various amounts of phase change material (PCM) in the ceiling panel is also assessed. PCM allows the ceiling panel to maintain the desired temperature for an extended amount of time, but it also increases the time that it takes for the panel to reach the desired temperature. Transient thermal simulations are performed for both start up and shut down scenarios and the amount of time that it takes for the ceiling temperature to cool down to the desired level (on-mode) or heat up (off-mode) to the temperature at which it has to turn back on again are calculated for various system configurations. The results from this study can be used for optimal design of TE-based radiant cooling ceiling panels to achieve high energy efficiency and low operating cost while maintaining occupants’ comfort in the buildings.

Sticky thermoelectric materials for flexible thermoelectric modules to capture low-temperature waste heat

ABSTRACTWe examined a working hypothesis of sticky thermoelectric (TE) materials, which is inversely designed to mass-produce flexible TE sheets with lamination or roll-to-roll processes without electric conductive adhesives. Herein, we prepared p-type and n-type sticky TE materials via mixing antimony and bismuth powders with low-volatilizable organic solvents to achieve a low thermal conductivity. Since the sticky TE materials are additionally injected into punched polymer sheets to contact with the upper and bottom electrodes in the fabrication process, the sticky TE modules of ca. 2.4 mm in thickness maintained temperature differences of ca. 10°C and 40°C on a hot plate of 40 °C and 120°C under a natural-air cooling condition with a fin. In the single-cell resistance analysis, we found that 75∼150-µm bismuth powder shows lower resistance than the smaller-sized one due to the fewer number of particle-particle interfaces in the electric pass between the upper and bottom electrodes. After adjusting the printed wiring pattern for the upper and bottom electrodes, we achieved 42 mV on a hot plate (120°C) with the 6 x 6 module having 212 Ω in the total resistance. In addition to the possibility of mass production at a reasonable cost, the sticky TE materials provide a low thermal conductivity for flexible TE modules to capture low-temperature waste heat under natural-air cooling conditions with fins for the purpose of energy harvesting.

Investigating the Effect of Medium Liquid Layer Circulation on Temperature Distribution in a Thermoelectric Generator Heat Exchanger Assembly

Thermoelectric generators (TEGs) are used to produce electricity utilizing two energy reservoirs. Despite the extensive research conducted on thermoelectric (TE) modules, their efficiencies are still low; therefore, any contribution to increase the efficiency of TE modules is valuable. It is known that the efficiency of individual TE modules depends on the temperature difference between their hot and cold faces. In practical applications employing an array of TE modules, the temperature distribution along the flow direction varies, which adversely affects system's efficiency. In this study, it is aimed to attain a homogeneous temperature distribution along a number of TE pieces by focusing on the structure of TEG heat exchanger. The proposed design includes an intermediate layer of liquid that plays a key role in keeping the temperature distribution homogeneous and at the desired temperature difference level. A three-dimensional (3D) computational fluid dynamics (CFD) model was developed for analyzing the circulation of liquid layer and the thermal behavior in the system. Results show decrease in temperature deviation both on cold and hot sides of TE modules, while the decrease is more on the latter. With more homogeneous temperature distribution along the TE surfaces, it is possible to tune the system to operate TE modules in their optimum temperature differences. It is illustrated that the heat transfer rate is increased by 11.71% and the electric power generation is enhanced by 19.95% with the proposed heat exchanger design. The consumption of pumping power has taken into account in the efficiency calculations.

Realizing high thermoelectric performance with comparable p- and n-type figure-of-merits in a graphene/h-BN superlattice monolayer

We demonstrate that the superlattice monolayer consisting of light, earth-abundant, and environmentally friendly elements can be designed as perfect TE modules with comparable p- and n-type energy conversion efficiency.

An experimental investigation on the performance of a thermoelectric dehumidification system

A thermoelectric (TE) air-cooling system for dehumidifying indoor air in a building was investigated. The system was composed of 4 TE modules. The cold sides of the TE modules were fixed to an aluminum heat sink to remove moisture in the air of a test chamber of 1 m3 volume, while a heat sink with circulating cooling water at the hot sides of the TE modules was used for heat release. The effects of input electric current to the TE modules and air flow rate through the heat sink were experimentally determined. The system’s performance was evaluated using dehumidification effectiveness and coefficient of performance (COP). A suitable condition occurred at 18.5 A of current flow and 240 W of power being supplied to the TE modules with a corresponding cooling capacity of 149.5 W, which gave a dehumidification effectiveness of 0.62. Therefore, it is anticipated the proposed TE dehumidifier concept will contribute to the air conditioning system’s reduction of room humidity.