A performance comparison of SiGe and skutterudite based segmented thermoelectric devices

A three-dimensional model of Segmented Thermoelectric Unicouples (STUs) is developed and incorporated into the ANSYS commercial software. The governing equations are solved, subject to the prescribed boundary conditions, using the Finite Element Methodology (FEM) techniques and meshing capabilities in ANSYS. The model accounts for the side heat losses, handles different types of boundary conditions, and accounts for the non-homogeneity and the change in physical and thermoelectric properties of the segments materials in the n- and p-legs with temperature. The model predictions are compared with experimental data of two STUs, uni8 and uni12, comprised of n-type Bi2Te3 and CoSb3-based alloys and p-type Bi2Te3 and CeFe4Sb12-based alloys, and tested recently at the Jet Propulsion Laboratory (JPL) between hot and cold side temperatures of ∼305 K and 885 K, respectively. The calculations helped determine not only the side heat losses in these tests and the performance parameters of the STUs, but also the spatial dissipation of the heat losses from the various sides of and of the 3-D temperature fields in the n- and p-legs. The estimated values of the total side heat losses in uni8 and uni12 are 3.7 W and 1.83 W, respectively, and of the total contact resistance per leg are 146 and 690 μΩ-cm2, respectively. The predicted peak conversion efficiencies in these tests for uni8 and uni12 are 4.55% and 5.65%, respectively, compared to 11.46% and 9.09%, which could be attainable with zero side heat losses, for the same total contact resistance per leg.

Efficient segmented thermoelectric unicouples for space power applications

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.

The alkali metal thermal to electric converter (AMTEC) used in the Advanced Radioisotope Power System (ARPS) program has been developed around a specific system configuration that was derived from the radioisotope thermoelectric generator (RTG) used for the last 20 years. This configuration, and the restrictions it places on the converter technology, limits the overall generator performance. An advanced AMTEC system design, that is not based on RTG heritage, using AMTEC chimney cells, is better suited for the AMTEC technology and provides substantially better power density and efficiency. It also provides system scale-ability from 10 to 100 Watts. While technology development continues to proceed with the ARPS cell design in order to validate the technology, efforts are also underway to develop the advanced technology to meet the more aggressive mass, efficiency, life and electromagnetic performance requirements of future missions. INTRODUCTION The alkali metal thermal to electric converter (AMTEC) has been considered to be a potential candidate for small radioisotope space power systems since the early 1980's. Recent converter technology advances and system design work by Hendricks et al. and Schock et al.' have shown these systems to be very attractive relative to the state of the art radioisotope thermoelectric generators (RTG's), currently used in all spacecraft radioisotope power system. The AMTEC technology not only reduces the system mass relative to RTG technology, it also requires significantly less radioactive material than the RTG's for any given power requirement. From mid-1997 to mid-1999, the Advanced Radioisotope Power System (ARPS) program, was focused on developing the first AMTEC power system for the Europa and Pluto missions. This power system, which has been described in the literature, is the first generation of AMTEC space systems. It is derived from the RTG system technology and has several features in common with the RTG systems. • The cells are mounted to the inside of a cylindrical housing. This The general purpose heat source (GPHS) is stacked, and the stack is held from each end in much the same way as the RTG. The cells use the same mounting feature used in the RTG unicouple. The cell must support the weight of the multilayer insulation package, system is 14% efficient and 21 kg for approximately 100-120 W, end of mission power. The use of RTG system reduced the system level design effort, however it also increased the AMTEC cell development risk by requiring that the technology be configured for the system as opposed to configuring the system to meet the technology needs. The combination of developing the technology under the constraint of the RTG heritage requirements and a number of changes in the spacecraft power requirements made AMTEC technology development very difficult. During the course of the two years of development, there were two major changes in system power level and one change in configuration. This resulted in 3 different cell revisions that were actually designed and tested. The final E-revision cell is shown in Figure 1. Figure 1. ARPS AMTEC Cell, Revision E. American Institute of Aeronautics and Astronautics (c)2000 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization. With the challenges of developing the materials and fabrication processes for the refractory metal cell (previous designs were stainless steel), these design changes made it very difficult to mature the fabrication process. In mid-1999 DOE and NASA made the decision that AMTEC would not be ready for the first planned ARPS mission in 2003 or 2004. Cell testing had not yet reached the point of demonstrating reliable performance and was not yet ready for life testing at that time. Cell development has continued since mid-1999 and substantial progress has been made, with cells now capable of producing power at or near predicted levels and, in most cases, to operating reliably at nominal and elevated temperatures. These cells are still designed for the RTG heritage system, and while they are not the design that would provide the highest efficiency or power, they are a baseline to fully develop and prove the technology for mission use. Life testing could begin early next fiscal year. ADVANCED SYSTEM DESIGN An AMTEC system design that is significantly lower mass than the current ARPS design has been described in the literature. This design is not constrained by RTG heritage. It places the cells at only two ends of the heat source stack. A new method is used to support only two GPHS. It eliminates the cell mounting features used in the ARPS cell. This system is over 20% efficient and 8.9 kg for approximately 100 W, end of mission. Closure Plate Cell Interconnects

The present study investigates the performance of solar photovoltaic integrated thermoelectric cooler using MATLAB Simulink. The enhancement of efficiency has been achieved using an effective heat removal mechanism from the hot side heat sink. Since the hot side temperature is a crucial parameter. The intrinsic material properties like Seebeck coefficient, ?, thermal conductance, K, and electrical resistance, R, of the thermoelectric module are carefully estimated using analytical method and reported. The MATLAB Simulink Peltier module is developed based on the estimated intrinsic properties. The effect of system voltage (V) and current (A) on the thermal parameters like cooling capacity, QC, and coefficient of performance has been investigated. The simulation study is validated by conducting a series of experimental analysis. The experimental model is equipped with a 100 Wp polycrystalline solar photovoltaic module to integrate and power the 12V/5A of the 60 W thermoelectric cooler. Moreover, the results reveal that there is a significant effect of ambient and hot side temperature on the thermoelectric cooler performance. The fin-type conductive mode of heat transfer mechanism is adopted along with the convective forced air-cooling system to achieve effective heat removal from the hot side. The infrared thermographic investigation is carried out for ascertaining effective heat removal.

Enhanced Peltier refrigerator using an innovative hot-side heat-rejection mechanism; Experimental study under both transient and steady-state conditions

Taguchi optimization and analysis of variance for thermoelectric generators with forced convection air cooling

Lockheed Martin contributions to the Cassini mission included power and propulsion for the spacecraft, the Descent Imager / Spectral Radiometer, DISR instrument for the Huygens Probe, as well as the Titan IVB launch vehicle. Cassini is currently in orbit around Saturn performing its primary science mission, investigating Saturn, its many moons, and its complex and beautiful ring system. The Space Power Programs organization in King of Prussia, Pennsylvania, an offsite of Lockheed Martin Space Systems Company, provided the three General Purpose Heat Source — Radioisotope Thermoelectric Generators (GPHS‐RTGs) used to provide electric power to the spacecraft during its mission to Saturn and its moons. The RTGs were the same design as those used to power the Galileo spacecraft on its mission to Jupiter and its moons, and the ESA Ulysses spacecraft on its mission to explore the Sun. Three RTGS provided 880 Watts of electrical power to the spacecraft at the beginning of mission, shortly after launch, 50% more than the power available for the Galileo mission. Other papers will describe the extensive science instrumentation made possible by the abundance of continuous, reliable, and long‐lived power, unprecedented for a deep space planetary mission. The Cassini Propulsion Module Subsystem is the largest interplanetary propulsion system ever to successfully enter orbit around another planet. The propulsion system was designed to be fully redundant for this critical, 11‐year scientific mission to Saturn. The system was designed, assembled and tested at Lockheed Martin’s Space Exploration Systems Company in Littleton, Colorado, before being delivered to the Jet Propulsion Laboratory, JPL in Pasadena California for integration and testing with the spacecraft. The bi‐propellant system design holds 3,000 kg of Monomethyl Hydrazine, MMH and Nitrogen Tetroxide, NTO and uses 132 kg of High Purity Grade Hydrazine for 3‐axis attitude control and Reaction Wheel Assembly, RWA desaturation.

Since the launch of the first radioisotope power system (RPS) on Transit 4A in 1961, numerous research and development activities have been performed centered on increasing the overall thermal to electrical conversion efficiency of the selected nuclear fueled power system. The latest U.S. fielded RPS (MMRTG - Multi-Mission Radioisotope Thermoelectric Generator) contains eight GPHS (General Purpose Heat Source) modules which nominally yield ∼2000W Th from the thirty-two 238PU5O 2 ceramic fuel pellets. MMRTG's PbTe/TAGS-85 based thermoelectric couples have a thermal to electrical conversion efficiency of ∼5.5% thus yielding ∼110W e at launch. This paper centers on the discussion of a conceptual idea that entails employing a second set of thermoelectrics on an MMRTG. These would be employed for possibly converting a portion of the excess “waste heat” (∼1750 W th ) into additional electrical mission power. First-order experiments and calculations employing bismuth telluride (Bi 2 Te 3 ) based thermoelectric modules being considered for a European RPS by the University of Leicester indicate that an improvement in the efficiency of an MMRTG could be achieved by integrating them with the PbTe/TAGS-85 thermoelectrics being utilized in the MMRTG in a “dual” or “cascaded” arrangement. This arrangement of two different integral thermoelectric materials suggests the intriguing possibility of the additional harvesting of a portion of the MMRTG's currently unutilized “waste heat”. This appears to be feasible since the cold side temperature of the PbTe/TAGS-85 in an MMRTG is ∼200°C which corresponds to typical hot-side operating temperatures of the Bi 2 Te 3 thermoelectric modules. It is recognized that extensive thermo-mechanical-electrical design, modeling, and analysis are required to fully investigate the cascaded thermoelectric concept. In addition, materials compatibility and assembly aspects will need to be fully addressed in the future. The present work indicates that system-level performance gains could be achieved via a “cascaded” or cMMRTG which could result in electrical power increases at BOM (Beginning of Mission) of up to ∼25%, and perhaps more significantly, gains in EODL (End of Design Life) power of up to ∼40% which could be utilized on a future space mission.

The Cassini spacecraft is designed to carry out an orbital tour of the Saturnian system and an investigation of the planet, its satellites, atmosphere, and its ring system. The space vehicle is powered by three Radioisotope Thermoelectric Generators (RTGs) which are mounted normal to the thrust axis of the vehicle. The nuclear heat source for each RTG consists of a stacked column of eighteen General Purpose Heat Source (GPHS) modules. Each module primarily consists of an aeroshell, two Graphite Impact Shells (GIS), and four Fueled Clads (FC). Each FC consists of a fuel pellet of plutonium-238 in the form of the oxide PuO2 encased in an iridium shell which serves to contain the fuel. An extensive program of experimental tests and analyses was conducted in support of previous missions (Galileo and Ulysses) which served to calibrate and validate the PISCES 2D-ELK continuum mechanics code. This paper describes the response of the GPHS-RTG system to a large number of potential launch accident environments employing the MSC/PISCES Euler Lagrange shell coupled hydrocode as an analytical tool. The results of these calculations quantified the integrity of the iridium clad fuel containment system and provided a data base for a determination of the overall risk for the Cassini mission by others.

Thermoelectric cooler (TEC) is a kind of solid hot pump performed with Peltier effect. And it is small, light and noiseless. The cooling quantity is proportional to the TEC working current when the temperature difference between the hot side and the cold side keeps stable. The heating quantity and cooling quantity can be controlled by changing the value and direction of current of two sides of TEC. So, thermoelectric cooling technology is the best way to cool CCD device. The E2V's scientific image sensor CCD47-20 integrates TEC and CCD together. This package makes easier of electrical design. Software and hardware system of TEC controller are designed with CCD47-20 which is packaged with integral solid-state Peltier cooler. For hardware system, 80C51 MCU is used as CPU, 8-bit ADC and 8-bit DAC compose of closed-loop controlled system. Controlled quantity can be computed by sampling the temperature from thermistor in CCD. TEC is drove by MOSFET which consists of constant current driving circuit. For software system, advanced controlled precision and convergence speed of TEC system can be gotten by using PID controlled algorithm and tuning proportional, integral and differential coefficient. The result shows: if the heat emission of the hot side of TEC is good enough to keep the temperature stable, and when the sampling frequency is 2 seconds, temperature controlled velocity is 5°C/min. And temperature difference can reach -40°C controlled precision can achieve 0.3°C. When the hot side temperature is stable at °C, CCD temperature can reach -°C, and thermal noise of CCD is less than 1e-/pix/s. The controlled system restricts the dark-current noise of CCD and increases SNR of the camera system.

A new system to generate electric energy using thermoelectric generators (TEG’s) based on Peltier cells has been conceived, designed and built. The system consists of a Peltier cell assembly installed in a replica of an air conditioning circuit to benefit from hot and cold air flow to generate the appropriate temperature gradient. The new system has been characterized using a group of Peltier cells mounted on a dual thermostatic chamber where cold air from air conditioning equip and hot air coming from an industrial heater are flowing through independent half-chambers. The two half-chambers are separated by an insulation wall where Peltier cells have been inserted. Temperature difference between hot and cold air flow is used by the Peltier cells to generate a voltage and current using the Seebeck effect. Peltier cells are connected in series and parallel to increase voltage and current to obtain appropriate values compatibles with external applications. Experimental tests have been developed to characterize the new design obtaining electric current and voltage, thus power, from the Peltier cell assembly. The amount of power is proportional to the temperature difference between hot and cold side of the chamber through an exponential evolution with maximum performance for specific temperature difference. Power density of the TEG has been found of 2.5x10 4 W/m 2 for a temperature difference of 160º C. TEG assembly generates a current of 8 A and 5 VDC voltage at the peak power point. The system has been tested at temperature differences compatible with those created in air conditioning ducts to recreate a real situation. Power generation for set up conditions of 50º C at the hot side and 5º C at the cold one, like in conventional air conditioning ducts, has been found of very low value because of the low temperature difference. However, when using industrial conditions with hot temperature in the range 100º C to 130º C and cold temperature between -30º C and 0º C, the power generation has increased significantly, showing the critical influence of the temperature difference. The simulation analysis indicates that the new design is capable of generating enough power to cover energy demand in residential buildings.

In a Stirling Radioisotope Power System (RPS), heat must be continuously removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling convertor normally provides this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS at the cost of an early termination of the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) can be used to passively allow multiple stops and restarts of the Stirling convertor. In a previous NASA SBIR Program, Advanced Cooling Technologies, Inc. (ACT) developed a series of sodium VCHPs as backup cooling systems for Stirling RPS. The operation of these VCHPs was demonstrated using Stirling heater head simulators and GPHS simulators. In the most recent effort, a sodium VCHP with a stainless steel envelope was designed, fabricated and tested at NASA Glenn Research Center (GRC) with a Stirling convertor for two concepts; one for the Advanced Stirling Radioisotope Generator (ASRG) back up cooling system and one for the Long-lived Venus Lander thermal management system. The VCHP is designed to activate and remove heat from the stopped convertor at a 19 degC temperature increase from the nominal vapor temperature. The 19 degC temperature increase from nominal is low enough to avoid risking standard ASRG operation and spoiling of the Multi-Layer Insulation (MLI). In addition, the same backup cooling system can be applied to the Stirling convertor used for the refrigeration system of the Long-lived Venus Lander. The VCHP will allow the refrigeration system to: 1) rest during transit at a lower temperature than nominal; 2) pre-cool the modules to an even lower temperature before the entry in Venus atmosphere; 3) work at nominal temperature on Venus surface; 4) briefly stop multiple times on the Venus surface to allow scientific measurements. This paper presents the experimental results from integrating the VCHP with an operating Stirling convertor and describes the methodology used to achieve their successful combined operation.

In a Stirling Radioisotope Power System (RPS), heat must be continuously removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling convertor normally provides this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS at the cost of an early termination of the mission. An alkali-metal variable conductance heat pipe (VCHP) can be used to passively allow multiple stops and restarts of the Stirling convertor by bypassing the heat during stops. In a previous NASA Small Business Innovation Research (SBIR) Program, Advanced Cooling Technologies, Inc. (ACT) developed a series of sodium VCHPs as backup cooling systems for the Stirling RPS. In 2012, one of these VCHPs was successfully tested at NASA Glenn Research Center with a Stirling convertor as an Advanced Stirling Radioisotope Generator (ASRG) backup cooling system. The prototype; however, was not optimized and did not reflect the final heat rejection path. ACT through further funding has developed a semioptimized prototype with the finalized heat path for testing at Glenn with a Stirling convertor. The semioptimized system features a two-phase radiator and is significantly smaller and lighter than the prior prototype to reflect a higher level of flight readiness. The VCHP is designed to activate and remove heat from the GPHS during stoppage with a small temperature increase from the nominal vapor temperature. This small temperature increase from nominal is low enough to avoid risking standard ASRG operation and spoiling of the multilayer insulation (MLI). The VCHP passively allows the Stirling convertor to be turned off multiple times during a mission with potentially unlimited off durations. Having the ability to turn the Stirling off allows for the Stirling to be reset and reduces vibrations on the platform during sensitive measurements or procedures. This paper presents the design of the VCHP and its test results with a Stirling convertor at Glenn. Tests were carried for multiple on and off cycles to demonstrate repeatability. The impacts associated with the addition of the VCHP to the system are also addressed in terms of mass and additional heat losses due to the presence of the VCHP.

Heat dissipation is extremely important for electronic component such as CPU or GPU of the computer. Now most researchers only design optimal heat sink for CPU for better heat dissipation, while few of them consider waste heat recycling of CPU. The CPU can be used as the heat source, while the original system has fan and heat sink as the cooling system. Thus, the original CPU working condition is very suitable for thermoelectric power generation and will bring great benefit to system itself. However, adding thermoelectric generator will increase the temperature of CPU, which will decrease the performance of the computer. It is necessary to reduce the hot side temperature while generating energy as much as possible. To achieve this, this paper designed a kind of intelligent waste heat generation system based on thermoelectric power generator. Three different shape heat sinks are designed, contrasted, and tested. By building experimental platform and establishing simulation model, the power of thermoelectric power generation and temperature change of the three heat sink structures are compared. The fin shaped heat sink is considered has the best output performance while keeping the hot side temperature within the acceptance range. The maximum output power is 10.67mW, and the maximum hot side temperature is 72°C during the experiment.