Solar Dynamic Space Power System Research Articles

Exergy analysis and parameter optimization of heat pipe receiver with integrated latent heat thermal energy storage for space station in charging process

The heat pipe (HP) receiver with integrated latent heat thermal energy storage (LHTES) is one of the key components of solar dynamic space power system (SDPSS). Therefore, thermodynamic analysis and optimization of SDPSS is significant for improving system efficiency and reducing launch cost. In this paper, a two-dimensional physical model was developed. Meanwhile, we studied further energy and exergy characters during charging process in microgravity environment. The equation of exergy efficiency was deduced by analyzing the relationship between heat flux and mass flow of HP. Through discussing the key parameters to exergy efficiency (length of evaporator (Le), length of phase change material (PCM) (L), and length of condenser with Stirling engine (L1)), the optimization of parameters—Le=0.36m, L=0.41m and L1=0.43m—were obtained by genetic algorithm when exergy efficiency reaches the maximum value of 0.97585. The results provide theoretical guidance for structure design and applications of SDPSS.

Early results from solar dynamic space power system testing

A government/industry team designed, built and tested a 2-kWe solar dynamic space power system in a large thermal vacuum facility with a simulated Sun at the NASA Lewis Research Center. The Lewis facility provides an accurate simulation of temperatures, high vacuum and solar flux as encountered in low-Earth orbit. The solar dynamic system includes a Brayton power conversion unit integrated with a solar receiver which is designed to store energy for continuous power operation during the eclipse phase of the orbit. This paper reviews the goals and status of the Solar Dynamic Ground Test Demonstration project and describes the initial testing, including both operational and performance data. System testing to date has accumulated over 365 hours of power operation (ranging from 400 watts to 2.0-W(sub e)), including 187 simulated orbits, 16 ambient starts and 2 hot restarts. Data are shown for an orbital startup, transient and steady-state orbital operation and shutdown. System testing with varying insolation levels and operating speeds is discussed. The solar dynamic ground test demonstration is providing the experience and confidence toward a successful flight demonstration of the solar dynamic technologies on the Space Station Mir in 1997.

Advanced Solar Dynamic Space Power Systems, Part I: Efficiency and Surface Optimization

The aim of this work is the proposal and the analysis of advanced solar dynamic space power systems for electrical space power generation. The detailed thermodynamic analysis of SDCC (Solar Dynamic Combined Cycle) and SDBC (Solar Dynamic Bynary Cycle) systems is carried out. The analysis is completed with an optimization procedure that allows the maximum efficiency and minimum surface conditions to be obtained. The calculation is carried out for the orbital conditions of the NASA-Freedom Space Station. The results are presented, compared with the data already published for a reference CBC (Closed Brayton Cycle) plant (Massardo, 1993b), and discussed in depth.

Advanced Solar Dynamic Space Power Systems, Part II: Detailed Design and Specific Parameters Optimization

The aim of this work is the proposal and the analysis of advanced solar dynamic space power systems for electrical space power generation. In the first part of this work (Agazzani and Massardo, 1995) a performance optimization procedure for a SDCC (Solar Dynamic Combined Cycle) and a SDBC (Solar Dynamic Binary Cycle) was presented. Results have pointed out improvements obtainable in terms of conversion efficiency and specific area (m2/kWe), this last estimated in a simplified way. Nevertheless, before drawing conclusions about the superiority of these advanced systems, it is necessary to verify the constructive possibility of the single components of the systems, estimating weights and surfaces, the most significant parameters in space applications. In this second part the design procedures of some components will be discussed in detail; a complete optimization procedure (thermodynamic analysis and detailed design) will be presented with the purpose of minimizing specific area (m2/kWe) and specific mass (kg/kWe). The results obtained are presented, discussed, and compared with the data of a reference optimized CBC system (Massardo, 1993b).

Space power system passes first test

The first successful test of a complete, fully integrated solar dynamic space power system has been carried out in a space simulation vacuum chamber at the National Aeronautics & Space Administration's Lewis Research Center in Cleveland. The 25-foot-diameter concentrator (rear) made up of seven hexagonal reflective panels covered with an aluminum-silicon dioxide coating focuses simulated sunlight onto a receiver (tilted canister at lower left), heating a working gas (a helium-xenon mixture). The gas powers a turboalternator/compressor (foil-wrapped apparatus next to receiver), generating 2 kW of electricity. A salt storage material in the receiver (lithium fluoride-calcium fluoride mixture) provides thermal energy storage, absorbing and releasing energy by melting and freezing to ensure continuous production of electricity through sun/darkness cycles. Being developed under a joint U.S.-Russian program, the solar dynamic system is slated for first use in space on Russian space station Mir in September 1997...

Application of high temperature multilayer insulations

Low temperature multilayer insulation systems are highly efficient in usual satellite applications. Thermal control in the field of Earth reentry systems as well as space power plants benefit from the application of high temperature multilayer insulations. The analytic prediction of high temperature multilayer insulation performance in a changing environment is enabled if the dependence of the heat transfer modes on the various design parameters is known. Systematic and tailored design of the insulation becomes feasible then. This is illustrated by three typical examples like a planetary probe for the exploration of the solar system, an Earth based space transportation system and a solar-dynamic space power system for low Earth orbit application.

Thermal Analysis and Fundamental Tests on a Heat Pipe Receiver for a Solar Dynamic Space Power System

Studies and fundamental tests were conducted on the heat pipe receiver. The advantages of this receiver are not only the improvement of reliability by the temperature uniformity, but the effective use of phase change thermal storage materials. The latter makes the receiver lighter and smaller. A performance analysis of the heat pipe receiver containing the thermal storage material was conducted using a computer program. Potassium was used as the working fluid of the heat pipe receiver. Results are compared with conventional receivers. The thermal storage ability of the phase change material (LiF-CaF2) was examined, and the influence of the volume change of the thermal storage material during its phase changes was also examined separately by an elementary test in a thermal storage tube. A prototype of the heat pipe receiver element was fabricated, and its performance was studied by simulating the insolation cycle with an electric heater.