Megawatt solar power systems for lunar surface operations

Lunar surface operations require habitation, transportation, life support, scientific, and manufacturing systems, all of which require some form of power. As an alternative to nuclear power, the development of a modular one megawatt solar power system is studied, examining both photovoltaic and dynamic cycle conversion methods, along with energy storage, heat rejection, and power backup subsystems. For photovoltaic power conversion, two systems are examined. First, a substantial increase in photovoltaic conversion efficiency is realized with the use of new GaAs/GaSb tandem photovoltaic cells, offering an impressive overall array efficiency of 23.5 percent. Since these new cells are still in the experimental phase of development, a currently available GaAs cell providing 18 percent efficiency is examined as an alternate to the experimental cells. Both Brayton and Stirling cycles, powered by linear parabolic solar concentrators, are examined for dynamic cycle power conversion. The Brayton cycle is studied in depth since it is already well developed and can provide high power levels fairly efficiently in a compact, low mass system. The dynamic conversion system requires large scale waste heat rejection capability. To provide this heat rejection, a comparison is made between a heat pipe/radiative fin system using advanced composites, and a potentially less massive liquid droplet radiator system. To supply power through the lunar night, both a low temperature alkaline fuel cell system and an experimental high temperature monolithic solid-oxide fuel cell system are considered. The reactants for the fuel cells are stored cryogenically in order to avoid the high tankage mass required by conventional gaseous storage. In addition, it is proposed that the propellant tanks from a spent, prototype lunar excursion vehicle be used for this purpose, therefore resulting in a significant overall reduction in effective storage system mass

Development of a transient model of a Stirling-based CHP system

Although the Stirling engine was invented in 1816, this heat engine still continues to be investigated due to the variety of energy sources that can be used to power it (e.g., solar energy, fossil fuels, biomass, and geothermal energy). To study the performance of these machines, it is necessary to develop and simulate models under different operating conditions. In this paper, we present a one-dimensional dynamic model based on components from Trnsys: principally, a lumped mass and a heat exchanger. The resulting model is calibrated using GenOpt. Furthermore, the obtained model can be used to simulate the machine both under steady-state operation and during a transient response. The results provided by the simulations are compared with data measured in a Stirling engine that has been subjected to different operating conditions. This comparison shows good agreement, indicating that the model is an appropriate method for transient thermal simulations. This new proposed model requires few configuration parameters and is therefore easily adaptable to a wide range of commercial models of Stirling engines. A detailed analysis of the system results reveals that the power is directly related to the difference of temperatures between the hot and cold sources during the transient and steady-state processes

Engineering Ionomer Materials for Addressing Ohmic Resistances in Electrochemical Desalination and Waste Heat Recovery

Water scarcity and energy availability present important challenges that need to be addressed in the coming centuries. In the front of water technologies, desalting brackish water is of extreme importance for thermal electric power plants, chemical manufacturing plants, and other industrial operations that treat and reuse their water utilities. Membrane capacitive deionization (MCDI) is an energy efficient desalination technique that has drawn attention from commercial entities. Most material research studies on MCDI focus on enhancing electrode performance while little emphasis is given to rationale design of ion-exchange membranes (IEMs). In this work, the ionic conductivity, permselectivity, and thickness for three different IEM chemistries (polyaliphatic, poly (arylene ether), and perfluorinated) were correlated to MCDI performance attributes. A 5-10-fold reduction in area specific resistance (ASR), with unconventional perfluorinated and poly (arylene ether) IEMs reduced the energy expended per ion removed in MCDI by a factor of two, compared to conventional electrodialysis IEMs. For further advancement in energy efficiency of operation, ohmic resistance of the spacer channel needs to be addressed for which, ion-exchange resins bound by a polymeric binder termed resin wafers were explored. A new class of ion-exchange resin wafers (RWs) fabricated with ion-conductive binders were developed that exhibit exceptional ionic conductivities - a 3-5-fold improvement over conventional RWs containing a non-ionic polyethylene binder. Incorporation into a resin-wafer electrodeionization stack (RW-EDI) resulted in an increased desalination rate and reduced energy expenditure. Overall, this work demonstrates that ohmic resistances can be substantially curtailed with ionomer binder RWs at dilute salt concentrations. With respect to energy, thermally regenerative ammonia flow batteries (TRBs) are an emerging platform for extracting electrical energy from low-grade waste heat (T \u3c 130 °C). Previous TRB demonstrations suffered from poor heat to electrical energy conversion efficiency when benchmarked against state-of-the-art thermoelectric generators. This work reports the highest power density to date for a TRB (280 W m-2 at 55 °C) with a 5.7× improvement in power density over conventional designs and thermal efficiency (ηth) values as high as 2.99 % and 37.9 % relative to the Carnot efficiency (ηth/C). The gains made in TRB performance was ascribed to the zero gap design and deploying a low-resistant, inexpensive anion exchange membrane (AEM) separator and implementing a copper ion selective ionomer coating on the copper mesh electrodes. The improved TRB power density and the use of a low-cost materials represent significant milestones in low-grade waste heat recovery using electrochemical platforms

Energy, exergy, and economic analysis of a geothermal power plant

The current study aimed at designing a geothermal power plant in the Nonal area in Damavand district for simultaneous generation of thermal energy the electric power in the network of Damavand City and a part of Tehran province, the organic working fluid for the above cycle is R245fa which is a non-flammable fluid of dry type. The values of energy efficiency, exergy, the net rate of entropy change, and the specific output power were calculated as 18.2%, 21.3%, 172.97 kW/K, and 31.43 kJ/kg, respectively. The cost of drilling a well, as well as designing and construction of Damavand’s geothermal power plant, were calculated to be 4.2 and 521.5 million (USD), respectively. Also, the cost per generation of each kW/h of power in Damavand power plant was 17 cents. The estimated payback time is calculated as 15 years. The analysis of the cycle in different months of the year showed that exergy efficiency has little change. The only significant effect of temperature changes was on the exergy efficiency as approximately a change of 2% can be seen during a year.Cited as: Kazemi, H., Ehyaei, M.A. Energy, exergy, and economic analysis of a geothermal power plant. Advances in Geo-Energy Research, 2018, 2(2): 190-209, doi: 10.26804/ager.2018.02.0

Space Electrochemical Research and Technology

Individual papers presented at the conference address the following topics: development of a micro-fiber nickel electrode for nickel-hydrogen cell, high performance nickel electrodes for space power application, bending properties of nickel electrodes for nickel-hydrogen batteries, effect of KOH concentration and anions on the performance of a Ni-H2 battery positive plate, advanced dependent pressure vessel nickel hydrogen spacecraft cell and battery design, electrolyte management considerations in modern nickel hydrogen and nickel cadmium cell and battery design, a novel unitized regenerative proton exchange membrane fuel cell, fuel cell systems for first lunar outpost - reactant storage options, the TMI regenerable solid oxide fuel cell, engineering development program of a closed aluminum-oxygen semi-cell system for an unmanned underwater vehicle, SPE OBOGS on-board oxygen generating system, hermetically sealed aluminum electrolytic capacitor, sol-gel technology and advanced electrochemical energy storage materials, development of electrochemical supercapacitors for EMA applications, and high energy density electrolytic capacitor

Energy. A continuing bibliography with indexes, issue 26, 1 April - 30 June 1980

This bibliography lists 1134 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System from April 1, 1980 through June 30, 1980

Space Station needs, attributes and architectural options study. Volume 7-4A: Data book, architecture, technology and programmatics, part A

Various parameters of the orbital space station are discussed. The space station environment, data management system, communication and tracking, environmental control, and life support system are considered. Specific topics reviewed include crew work stations, restraint systems, stowage, computer hardware, and expert systems

Optimización energética de una central térmica para su operación eficiente con un sistema de captura de CO2 por post-combustión

The post-combustion separation technology (PCC) is one out of three main types of CO2 separation. PCC is mainly characterized by the fact that the intervention in the conventional power plant process is the smallest one compared to the other capture technologies. Furthermore postcombustion can be applied to the conventional power plant process as well as to a CO2-producing industry plant. Therefore for Austria's point of view, PCC is the most promising technology. A state-of-art coal- red power plant retro tted with a post-combustion CO2 capture system was modeled with the process simulation tool EBSILONr Professional. The drastic CO2 emissions reduction comes together with a signi cant net e ciency penalty. A series of simulations were carried out to nd what further opportunity exists to reduce the impact of the capture system on net e ciency via astute integration of both plants. Within this thesis several heat integration measures were implemented and their results compared with the reference non integrated retro tted power plant, showing a signi cant e ciency penalty reduction after heat integration. ____________________________________________________La separación por post-combustión (PCC) es una de las tres principales tecnologías para la Captura y Con namiento de CO2. Esta técnica se caracteriza por poder ser implementada en centrales térmicas convencionales, requiriendo en ellas el mínimo número de modi caciones comparado con las demás tecnologías de captura. Más allá, esta tecnología puede ser aplicada también a otras grandes industrias emisoras de CO2. De este modo, la separación de CO2 por post-combustión es, desde el punto de vista austriaco, la opción más prometedora. La substancial reducción de emisiones de CO2 que este sistema posibilita, tiene como consecuencia directa una importante caída en el rendimiento neto de la central. A lo largo de este proyecto, llevado a cabo mediante el software comercial EBSILONr Professional, se ha simulado una central térmica de vanguardia alimentada por combustible carbón pulverizado, para su operación conjunta con un sistema de captura por post-combustión. La serie de simulaciones llevadas a cabo han demostrado como, a través de una astuta integración energética entre ambas; planta de captura y central térmica, es posible reducir la caída de rendimiento de una forma signi cativa y con ello los propios costes de reducción de emisiones.Ingeniería Industria

Modelling, Simulation and Optimisation of Multistage Humidification and Dehumidification Desalination Plant Using Solar Energy. Performance Evaluation and Improvement of the Humidification-Dehumidification Desalination Process through Modelling, Simulation and Optimisation Techniques

Serious social and economic disruptions are unfolding worldwide over the finite water and energy resources; hence, securing fresh water supply and employing renewable energy sources will help avoid catastrophic conflicts, continue modern lifestyles, and circumvent global warming and pollution. For this reason, a new method known as Humidification-Dehumidification (HDH) desalination process has been developed to address the challenge of water shortage. The aim of this research was to build the detailed mechanistic models with the increased capability to predict more accurately as well as to simulate and optimise the Multistage Humidification-Dehumidification (MHDH) desalination plant which is powered by solar energy. The poor prediction accuracy is major bottleneck for most of conventional models. Mechanistic models for HDH desalination process derived from non-linear mathematical equations offers a promising solution to overcome this challenge. This study proposes a mechanistic model which is formulated by combining the enthalpy equations with the models which govern the mass and heat transfer across a thin film that separates water and air phases within the humidifier and dehumidifier. The proposed model is validated by using the data which were obtained from the physical experiments. Moreover, an experimental rig was designed and fabricated to specifically generate the physical data. From the experimental and mathematical analysis, it was observed that the Recovery Ratio (RR) attained was increasing as temperature of the feed water increased. The RR was also increasing with the increase of dehumidifier’s surface area while it decreased with an increase of the packing size. Moreover, through a sensitivity analysis the highly influential parameters to the process model were identified to better understand the energy-efficient design principles and operating strategies for the maximum performance of the system. Finally, a two stages HDH hybrid system that uses solar and biomass as source of energy is proposed whereby, an optimisation problem is solved to achieve the optimum RR. A maximum of 2 stages were required for a system to operate optimally.Commonwealth Scholarship Commission in the UK (CSC) under PhD Scholarships Plan for Low and Middle Income Countrie

Energy: A continuing bibliography with indexes, issue 17

This bibliography lists 1292 reports, articles, and other documents introduced into the NASA scientific and technical information system from January 1, 1978 through March 31, 1978