Modular Isotopic Thermoelectric Generator

be adapted to various space missions over a wide range of power levels, with little or no redesign. Each RTG slice consists of a 250-watt heat source module, eight multicouple thermoelectric modules, and standard sections of insulator, housing, radiator fins, and electrical circuit. The design makes it possible to check each thermoelectric module for electrical performance, thermal contact, leaktightness, and performance stability, after the generator is fully assembled; and to replace any deficient modules without disassembling the generator or perturbing the others. The RTG end sections provide the spring-loaded supports required to hold the free-standing heat source stack together during launch vibration. Detailed analysis indicates that the present generation of RTGs, using the same heat source modules. There is a duplicate copy of this document. OSTI has a copy of this paper.

Comprehensive study and optimization of concentrated photovoltaic-thermoelectric considering all contact resistances

The research conducted and described in this paper focuses on the design of a cooling system using thermoelectric or peltier module (TEM) and heatsinks with considerations for temperate climatic conditions. A case study of Nigeria has been chosen. Nigeria as a tropical region experiences high temperature difference between the year (18 - 40 with sunhours ranging between (100 – 210 hrs) monthly, such that the desire for chilled beverages almost throughout the day becomes paramount neccesitating the need for a peltier mobile cooler in tropical regions especially with inadequate electricity supply. A 9-litre rectangular shaped cooler was chosen with an area of 1.155m 2 , a dimension of 0.65 estimated to contain 120 beverages with an estimated heat load of 483W. It is estimated to use five thermoelectric modules, a temperature sensor, tec controller, DC powered battery and ten heat sinks. Comparatively, the design criterias of these peltier cooler were compared with the performance evaluation of existng similar designs and found to be within optimum performance levels. At 10 , the thermoelectric modules are powered to start cooling until the beverages are at 0 estimated to be a period of fifteen minutes), afterwhich the tec controller turns off power and the system is temporarily off until a temperature of 10 is detected by the temperature sensor and a re-cooling is initiated. With these the frozen beverage products received in the morning can be re-cooled as many times as possible.

There is enormous military and commercial interest in developing quiet, lightweight, and compact thermoelectric (TE) power generation systems. This paper investigates design integration and analysis of an advanced TE power generation system implementing JP-8 fueled combustion and thermal recuperation. In the design and development of this portable TE power system using a JP-8 combustor as a high-temperature heat source, optimal process flows depend on efficient heat generation, transfer, and recovery within the system. The combustor performance and TE subsystem performance were coupled directly through combustor exhaust temperatures, fuel and air mass flow rates, heat exchanger performance, subsequent hot-side temperatures, and cold-side cooling techniques and temperatures. Systematic investigation and design optimization of this TE power system relied on accurate thermodynamic modeling of complex, high-temperature combustion processes concomitantly with detailed TE converter thermal/mechanical modeling. To this end, this paper reports integration of system-level process flow simulations using CHEMCAD™ commercial software with in-house TE converter and module optimization, and heat exchanger analyses using COMSOL™ software. High-performance, high-temperature TE materials and segmented TE element designs are incorporated in coupled design analyses to achieve predicted TE subsystem-level conversion efficiencies exceeding 10%. These TE advances are integrated with a high-performance microtechnology combustion reactor based on recent advances at Pacific Northwest National Laboratory (PNNL). Predictions from this coupled simulation approach lead directly to system efficiency–power maps defining potentially available optimal system operating conditions and regimes. Further, it is shown that, for a given fuel flow rate, there exists a combination of recuperative effectiveness and hot-side heat exchanger effectiveness that provides a higher specific power output from the TE modules. This coupled simulation approach enables pathways for integrated use of high-performance combustor components, high-performance TE devices, and microtechnologies to produce a compact, lightweight, combustion-driven TE power system prototype that operates on common fuels.

Thermal and electrical contact resistances (TCR and ECR) of thermoelectric generator (TEG) exert essential impacts on its performance. In this study, through a series of experiments these two important properties have been estimated in a wide range of thermal and mechanical conditions, and with different interfacial materials. The magnitudes of the overall TCR were found in the range of (1.12–2.00) × 10–3 m2⋅K/W with air, (0.82–1.81) × 10–3 m2⋅K/W with graphene sheet, and (3.61–8.37) × 10–4 m2⋅K/W with thermal grease as interfacial materials when the heat-source temperature varied from 348.15 K to 598.15 K and the imposed pressure load from 266 kPa to 1266 kPa. Importantly, the detailed TCRs at different locations across the TEG system were also analyzed. The dominant components, which occupy more than 80 % of the overall TCR, have been identified at the interfaces of the thermoelectric module contacting the heat source and heat sink. In our experiment, the corresponding ECRs under the same working conditions were (1.03–1.52) × 10–9 Ω⋅m2, (0.56–9.60) × 10–10 Ω⋅m2, and (1.05–6.23) × 10–10 Ω⋅m2, respectively. Moreover, it is revealed that the TEG system delivered better performance at relatively low TCR and ECR when it operated at a high heat-source temperature, a large pressure load and using thermal grease as interfacial material. In addition to these experimental findings, a novel fully-connected feed-forward artificial neural network (ANN) model was also proposed to predict the overall TCR. It is shown that such an ANN model, as a promising approach, can achieve a cost-effective TCR prediction in good accuracy, with the mean square error and correlation coefficient being 2.36 × 10–9 and 99.4 %, respectively. These numerical and experimental results in this study will be of particular value for future TEG design and optimization.

Advancements in thermoelectric materials and their performance for thermoelectric generators (TEGs): A short review

A radioisotope thermoelectric generator (RTG) is a device that directly converts the decay heat of a radioisotope into electrical energy using the Seebeck effect of a thermoelectric material. The constant decay of the radioisotope heat source produces heat as a system energy source. The thermoelectric module uses materials to obtain electric energy by Seebeck effect. The structure and size of the thermoelectric converter need to be optimized for different radioisotope heat sources. The power has stable output performance, sustainable operation, and strong environmental adaptability. Space micro-scientific instruments require power supplies that are sustainable, stable, and long-life. The micro radioisotope thermoelectric generator can be invoked as a sustainable long-life power supply in low-power device applications. The miniaturized RTG can be applied in long-term service meteorological/seismic monitoring stations that are widely distributed on the surface of the planet, small landing vehicles at extreme latitudes or areas with low solar flux, atmospheric-surface-flow monitoring systems, underground detectors, deep space micro spacecraft, wireless sensor networks, self-powered radiation sensors, deep-space robot probes, and radio observatories on the lunar surface. This study innovatively proposes micro stacked-integrated annular-radial radioisotope thermoelectric generator and prepares an integrated prototype to drive an RF2500-based radiofrequency wireless sensor network, and monitors the temperature of each node for a long time as a demonstration. A high-performance micro radioisotope thermoelectric generators module based on the flexible printed circuit and bismuth telluride thick film was designed and prepared by screen printing. They are tested by a loading electrically heated equivalent radioisotope heat source. The output performance of the micro-RTG at different ambient temperatures is further evaluated. When loaded with 238PuO2 radioisotope heat sources, an integrated prototype would generate an open-circuit voltage of 0.815 V, a short-circuit current of 0.551 mA, and an output power of 114.38 µW at 0.408 V. When loaded with a 90SrTiO3 or 241AmO2 radioisotope heat source, the prototype produced 66.38% and 6.15% of the output power (compared to 238PuO2), respectively. In the impact evaluation on ambient temperature, the electrical output performance of the prototype increases with increasing temperature (− 30 to 120 °C). In the evaluation of the effects of long-term radioisotope irradiation, the output performance decreased slightly as the irradiation dose was increased during the service period. The stack-integrated micro radioisotope thermoelectric generator developed in this study is expected to provide reliable power support for space micro-scientific instruments, especially distributed wireless sensor networks.

This paper analyses the working principles of hybrid thermoelectric photovoltaic generators under negative illumination (also referred to as thermoradiative configuration). These kinds of systems combine a thermoradiative photovoltaic cell (TR-PV cell) and a thermoelectric generator (TEG), placed in thermal contact with each other. In this configuration, the TR-PV part cools while irradiating toward the cold sky. For this reason, in addition to the generation of electrical output, the cell can set a difference of temperature (ΔT) across the TEG legs. A theoretical model describing the behavior of these kinds of hybrid devices is reported as a function of the emitter energy gap and temperature, the sky temperature, and the ΔT across the TEG. In analogy with the positive illumination case, the key parameter is found to be the cell temperature sensitivity, which sets the convenience of the hybrid approach. The results show that while the hybrid power density is in general smaller than the sole TR-PV case, a wide window of positive efficiency gains exists. This is possible because the outgoing power density varies with the cell temperature, in contrast with the positive illumination case where the incoming power density is fixed by the temperature of the Sun. This work sets the first theoretical attempt to understand the convenience of TR-hybrid thermoelectric-photovoltaic generators (TR-HTEPVG), quantitatively assessing the suitability of these novel kinds of devices.

A thermoelectric generator (TEG) is a clean electricity generator from a heat source, usually waste heat. However, it is not as widely utilized as other electricity generators due to low conversion efficiency from heat to electricity. One approach is a system-level net power optimization for a TEG system composed of TEGs, heat sink, and fans. In this paper, we propose airflow reuse after cooling preceding TEGs to maximize system net power. For the accurate system net power, we model the TEG system, air, and heat source with proper dimension and material characteristics, and simulate with a computational fluid dynamics program. Next, the TEG power generation and the fan power consumption are calculated in consideration of the Seebeck coefficient and internal electrical resistance varying with hot and cold side temperatures. Finally, we find the optimal number of TEGs and fan speed generating the most efficient system net power in various TEG systems. The results show that the system with a side fan with a specific number of TEGs provides a system net power up to 58.6% higher than when with a top fan. The most efficient system net power with the side fan increases up to four TEGs generating 1.907 W at 13,000 RPM.

A shielded storage rack has been installed as part of the Radioisotope Power Systems Facility (RPSF) at the U.S. Department of Energy’s (DOE) Hanford Site in Washington State. The RPSF is designed to replace an existing facility at DOE’s Mound Site near Dayton, Ohio, where General Purpose Heat Source (GPHS) modules are currently assembled and installed into Radioisotope Thermoelectric Generators (RTG). The overall design goal of the RPSF is to increase annual production throughput, while at the same time reducing annual radiation exposure to personnel. The shield rack design successfully achieved this goal for the Module Reduction and Monitoring Facility (MRMF), which processes and stores assembled GPHS modules, prior to their installation into RTGs. The shield rack design is simple and effective, with the result that background radiation levels within Hanford’s MRMF room are calculated at just over three percent of those typically experienced during operation of the existing MRMF at Mound, despite the fact that Hanford’s calculations assume five times the GPHS inventory of that assumed for Mound.

In the current study, the concept of building a power plant using thermoelectric generator (TEG) modules is investigated, both technically and economically. The hypothesized thermoelectric generation power plant is a modular system, consisting of a large array of electrically connected thermoelectric generator units for generating clean electricity with-out greenhouse gas (GHG) emissions, noise, or hazardous solid wastes. The envisioned thermoelectric generation power plant (TEGPP) considered here is assumed to utilize solar radiation as a heat source, and water as a heat sink. The viability of such a concept is examined in the current study based on available specifications of a high-output thermo-electric generator module released in the market (TEG1-24111-6.0). Benchmarking is car-ried out considering a high-efficiency photovoltaic (PV) panel in the market (SunPower SPR-MAX3-400), assuming that it operates under standard solar radiation of 1,000 W, and with a standard panel temperature of 25 C, causing it to give an output electric power of 400 W (DC or direct current). It is found that in order to have an electric power of a thermoelectric generator unit similar to that of a photovoltaic panel of equal surface area, the temperature at the hot side of the thermoelectric generator unit should be about 70 C if the cold-side temperature is 30 C. However; under this output power equiva-lence, the price of the thermoelectric generator unit is about 90 times that of a photovol-taic panel of equal size (based on prices of October 2023). At an elevated hot-side tem-perature of 300 C for the thermoelectric generator unit (with the cold-side temperature being still 30 C), the thermoelectric generator unit can generate electric power that is about 25 times the power generated by a photovoltaic panel of an equal geometric area. This big boost in the output power still does not counteract the large cost difference be-tween the thermoelectric generator technology and the photovoltaic technology, where the per-watt(electric) cost in the case of thermoelectric generators is 3.5 times its value in the case of photovoltaic panels. Thus, the TEG technology in its intensified generation mode is still relatively more expensive compared to the PV technology. The practical im-plications of the current study are excluding the thermoelectric generation (based on the Seebeck effect) concept from large-scale commercial power plants, and viewing thermoe-lectric generators as sources of small electric power for waste heat management or con-venient power sources for small mobile devices.

Behavior of a thermoelectric power generation device based on solar irradiation and the earth’s surface-air temperature difference

The objective of this study is to produce the thermoelectric (TE) module called as a Peltier module or element using new and promising materials that work at high temperature for generation of electricity with thermoelectric energy conversion from waste heat at high temperatures. Peltier modules used commercially nowadays can work at relatively low temperatures and their efficiency increase in proportion to the temperature difference between the surfaces of the modules. They consist of a pair of p- and n-type semiconductor. In this study, calcium cobalt oxide was chosen as a p-type semiconductor whilst zinc oxide was chosen as n-type semiconductor. Pure and aluminum-doped zinc oxide and silver-doped calcium cobalt oxide powders were synthesized via sol–gel processing successfully. The obtained powders were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), fourier transform infrared (FTIR), differential thermal analysis-thermogravimetry (DTA-TG), and scanning electron microscopy (SEM). In addition, the particle size distribution of the powders obtained via sol–gel processing was determined using a particle size analyzer. One and two leg oxide thermo-electric modules consisting of one pair of p-type 0.03 percent silver doped calcium cobalt oxide and n-type 0.02 percent aluminum doped zinc oxide bulks of 25 square millimeter cross-section and 3 millimeter heights were constructed. The thermoelectric module constructed was tested at high temperatures, and compared to other similar oxide modules reported in literature. Ultimately, the thermal stress and alteration of thermal stress depending on the leg length and side length of semiconductors were calculated using the finite element analysis (FEA) model in ANSYS 15.0 software. According to the results of the analysis, TE module was optimized in terms of mechanical behavior.

Development of a numerical method for the performance analysis of thermoelectric generators with thermal and electric contact resistance

The prosperity of intelligent wearables brings an increasingly critical problem of power supply. Regular rechargeable lithium or disposable button batteries have some problems, such as limited capacity, frequent replacement, environmental pollution, etc. Wearable energy harvester (WEH) can fundamentally solve these problems. Among WEHs, thermoelectric generator (TEG) is a promising option due to its independence of light condition or the motion of the wearer, and thermoelectric conversion (TEC) has the characteristics of quietness and continuity. Therefore, TEG has become a suitable choice for harvesting low-grade heat energy such as human body heat. Ionic thermoelectric gel (iTEG) has the advantages of a large Seebeck coefficient, freely defined shape and size, low processing cost, wide material sources, easy encapsulation, etc. In this paper, the gelatin-based iTEG is regulated and optimized by silica nanoparticles (SiO2 NPs). The optimal compound quantity of SiO2 NPs is determined, and the optimization mechanism is discussed through a series of characterization tests. Based on the iTEG, a kind of scalable flexible TEGs is proposed, and its preparation method is described in detail. A small wristband TEG (STEG) was made, and its Seebeck coefficient is 74.5 mV/K. Its bendability and stretchability were verified, and the impedance matching experiment was carried out. By charging a capacitor, the STEG successfully lights up an LED at a temperature difference (ΔT) of ~15.5 K. Subsequently, a large extended oversleeve TEG (LTEG) was prepared, and a set of heat sinks was added at the cooling end of the LTEG. Being worn on a volunteer’s forearm, the LTEG output a voltage of more than 3 V at ~20 °C. Through storing the converted energy in a capacitor, the LTEG directly drove a calculator without a DC–DC booster. The proposed iTEG and TEGs in this paper have the prospect of mass production, extending to people’s clothes, harvesting human body heat and directly powering wearable electronics.