Adaptive thermal modeling architecture for small satellite applications

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 189-190).The United States Air Force and commercial aerospace industry recognize the importance of moving towards smaller, better, and cheaper spacecraft to support the nation's increasing dependence on space-based technologies. Whether large or small, all spacecraft will require the same basic bus systems and environmental protection, simply scaled to fit the mission. The varying thermal environment in space is particularly important to spacecraft design and operation because of its affect on hardware performance and survivability. The Adaptive Thermal Modeling Architecture (ATMA) discussed in this thesis is meant to bridge the gap between the commercially available thermal modeling tools used for larger, more expensive satellites, and the low-fidelity algorithms and techniques used for simple first order analysis. The ATMA consists of the MATLAB based Adaptive Thermal Modeling Tool (ATMT) and its user's manual, as well as the process by which an inexperienced engineer can quickly and accurately perform on-orbit thermal trades studies for a range of space applications. The ATMA tools and techniques have been validated with an industry standard thermal modeling program (Thermal Desktop) and correlated to thermal test data taken from MIT's CASTOR nanosatellite. The concepts derived and evaluated within ATMA can be extended to a variety of aerospace modeling applications. The ATMT program and modeling architecture are currently being utilized by members of MIT's Space Engineering Academy (SEA) and undergraduate satellite team as well as the U.S. Air Force Academy's FalconSAT-6 program.by John Anger Richmond.S.M

Control Algorithms for Large-scale Single-axis Photovoltaic Trackers

The electrical yield of large-scale photovoltaic power plants can be greatly improved by employing solar trackers. While fixed-tilt superstructures are stationary and immobile, trackers move the PV-module plane in order to optimize its alignment to the sun. This paper introduces control algorithms for single-axis trackers (SAT), including a discussion for optimal alignment and backtracking. The results are used to simulate and compare the electrical yield of fixed-tilt and SAT systems. The proposed algorithms have been field tested, and are in operation in solar parks worldwide

Champs-Multizone and Virtual Building for Integrated Building Systems Design and Performance Evaluation

The ultimate goal of this research was to develop an integrated framework that facilitates performance-based multi-stage design of buildings and comparison between the performance predicted at the design stage and that monitored at operation stage. Such an integrated framework would not only enable design optimization, but also enable confirmation of design intent or diagnosis of performance deficiency, and thus provide feedbacks for future building design. This dissertation study represents the first step toward this ultimate goal, and had the following specific objectives:: 1) developing a combined heat, air, moisture and pollutant transport model for whole building performance simulation; 2) developing a real-time building IEQ and energy performance monitoring system using a Virtual Building structure to facilitate fast comparison between design and montored performance.; 3) developing a methodology to use CHAMPS-Multizone for a green building design throughout its initial and final design stage. The CHAMPS-Multizone model consists of building envelope model, room model, HVAC model and airflow model, and has an efficient and accurate numeric solvers. The model is tested under different building cases including ASHRAE 140 standard test and a three zones building test and comparision with EnergyPlus calculation results. The Virtual Building is a digital representation of the physical building with a hierarchical data structure, containing both static data such as enclosure assemblies, internal layout, etc. and dynamic data such as occupant activity schedule, outdoor weather conditions, indoor environmental parameters, HVAC operation data and energy consumption data. Then, the Virtual Building approach has been demonstrated in a LEED office building with its monitoring system. Finally, a multi-stage design process was formulated that considers the impact of climate and site, form and massing, external enclosure, internal configuration and environmental system on the whole building performance as simulated by CHAMPS-Multizone. Using the testbed building, both simulation results were also compared with the results monitored by the Virtual Building monitoring system. Future research includes refining CHAMPS-Multizone simulation capability and adding modules such as water loop calculation and integrating HVAC calculation with EnergyPlus

Conceptual design and performance evaluation of a hybrid concentrating photovoltaic system in preparation for energy

Concentrating sunlight and focussing it on smaller sized solar cells increases the device's power output per unit active area. However, this process tends to increase the solar cell temperature considerably and has the potential to compromise system reliability. Adding a heat exchanger system to regulate this temperature rise, can improve the electrical performance whilst simultaneously providing an additional source of low temperature heat. In this study the performance of a low concentrator photovoltaic system with thermal (LCPV/T) extraction was conceptualised and evaluated in depth. An experimental analysis was performed using a first-generation prototype consisting of 5 units of Cross Compound Parabolic Concentrators (CCPC) connected to a heat extraction unit. A bespoke rotating table was used as experimental apparatus to effectively evaluate the optical performance of the system, as a function of its angular positions to replicate the motion of actual sun. Key design performance parameters for the LCPV/T collector are presented and discussed. This work also provides a useful technique to effectively calculate system performance, as a function of the orientation-dependant electrical characterisation parameters data. Finally, a Computational Fluid Dynamics (CFD) model was also applied to investigate the efficacy of the heat exchanger and hence estimate the overall co-generation benefit of using such optimisation techniques on realistic CPV systems. It was highlighted through these simulations that the water flow rate had the potential to be a critical power-generation optimisation criterion for LCPV-T systems. The maximum power output at normal incidence with concentrators and no water flow was found to be 78.4 mW. The system was found to perform with an average electrical efficiency ranging between 10 and 16% when evaluated at five different geographic locations. Experimental analysis of the data obtained showed an increase in power of 141% (power ratio 2.41) compared to the analogous non-concentrating counterpart. For example, in the case of London which receives an annual solar radiation of 1300 kWh/m2 the system is expected to generate 210 kWh/m2. This may reduce further to include losses due to temperature, reflectance/glazing losses, and electrical losses in cabling and inverter by up to 36% leading to an annual power output of 134 kWh/m2 of module

Estimación de la radiación solar diaria para la ciudad de Bagua, región Amazonas, Perú

The solar radiation that reaches the earth is the fundamental source of renewable energy in nature, therefore, knowing the local solar radiation is essential for many applications. The objective of this study was to model the behavior of daily solar radiation in the city of Bagua, which allows us to plan and design strategies oriented towards the use of the primary source of renewable energy. For this, the Fernández-Zayas model has been used, which considers the parameters of the monthly  average of the maximum global solar radiation and the length of the solar day. The methodology is of the analytical type and consisted of three phases: The first, data collection and filtering of the meteorological station of the Toribio Rodríguez de Mendoza National University of Amazonas that is located in the study area; in the second, the model was implemented using the MATLAB / GUI interface, obtaining the simulation of solar radiation; and in the third, the model was validated by error goodness statistics and table t. The estimate of daily solar radiation was calculated and discussed. The results obtained are useful for any application of solar energy in the city of Bagua, Amazonas region, Peru.La radiación solar que llega a la tierra, es la fuente de energía renovable fundamental en la naturaleza, por ende, conocer la radiación solar local es esencial para muchas aplicaciones. El objetivo de este estudio fue modelar el comportamiento de la radiación solar diaria en la ciudad de Bagua, el cual nos permita planificar y diseñar estrategias orientadas hacia el aprovechamiento de la fuente primaria de energía renovable. Para ello, se ha empleado el modelo de Fernández-Zayas, el cual considera los parámetros del promedio mensual de la radiación solar global máxima y la longitud del día solar. La metodología es del tipo analítica y consistió en tres fases:La primera, recolección y depuración de datos de la estación meteorológica de la Universidad Nacional Toribio Rodríguez de Mendoza de Amazonas que se encuentra en el área de estudio; en la segunda, se implementó el modelo utilizando la interfaz MATLAB/GUI, obteniendo la simulación de radiación solar; y en la tercera, se validó el modelo mediante los estadísticos de bondad de error y la tabla t. La estimación de la radiación solar diaria se calculó y se discutió. Los resultados obtenidos son útiles para cualquier aplicación de la energía solar en la ciudad de Bagua, región Amazonas, Perú

Automatic extraction of urban structures based on shadow information from satellite imagery

The geometric visualisation of the buildings as the 3D solid structures can provide a comprehensive vision in terms of the assessment and simulation of solar exposed surfaces, which includes rooftops and facades. However, the main issue in the simulation a genuine data source that presents the real characteristics of buildings. This research aims to extract the 3D model as the solid boxes of urban structures automatically from Quickbird satellite image with 0.6 m GSD for assessing the solar energy potential. The results illustrate that the 3D model of building presents spatial visualisation of solar radiation for the entire building surface in a different direction

Optimal Heliomobile Field Configurations In A Variable-Geometry Test Facility For Central Receiver Solar Systems

L'apparato sperimentale per sistemi a torre a geometria variabile costruito presso il CTAER di Tabernas (Almería, Spagna) è una novità nel mondo del solare termodinamico. Attraverso un codice scritto in Matlab si è valutato ed ottimizzato il rendimento ottico di un ridotto campo solare mobile; un'analisi comparativa con un sistema concentratore fisso e la validazione dei risultati ottenuti mediante il software di ray-tracing Tonatiuh evidenziano le caratteristiche della struttura studiataope

Photovoltaic potential in building façades

Tese de doutoramento, Sistemas Sustentáveis de Energia, Universidade de Lisboa, Faculdade de Ciências, 2018Consistent reductions in the costs of photovoltaic (PV) systems have prompted interest in applications with less-than-optimum inclinations and orientations. That is the case of building façades, with plenty of free area for the deployment of solar systems. Lower sun heights benefit vertical façades, whereas rooftops are favoured when the sun is near the zenith, therefore the PV potential in urban environments can increase twofold when the contribution from building façades is added to that of the rooftops. This complementarity between façades and rooftops is helpful for a better match between electricity demand and supply. This thesis focuses on: i) the modelling of façade PV potential; ii) the optimization of façade PV yields; and iii) underlining the overall role that building façades will play in future solar cities. Digital surface and solar radiation modelling methodologies were reviewed. Special focus is given to the 3D LiDAR-based model SOL and the CAD/plugin models DIVA and LadyBug. Model SOL was validated against measurements from the BIPV system in the façade of the Solar XXI building (Lisbon), and used to evaluate façade PV potential in different urban sites in Lisbon and Geneva. The plugins DIVA and LadyBug helped assessing the potential for PV glare from façade integrated photovoltaics in distinct urban blocks. Technologies for PV integration in façades were also reviewed. Alternative façade designs, including louvers, geometric forms and balconies, were explored and optimized for the maximization of annual solar irradiation using DIVA. Partial shading impacts on rooftops and façades were addressed through SOL simulations and the interconnections between PV modules were optimized using a custom Multi-Objective Genetic Algorithm. The contribution of PV façades to the solar potential of two dissimilar neighbourhoods in Lisbon was quantified using SOL, considering local electricity consumption. Cost-efficient rooftop/façade PV mixes are proposed based on combined payback times. Impacts of larger scale PV deployment on the spare capacity of power distribution transformers were studied through LadyBug and SolarAnalyst simulations. A new empirical solar factor was proposed to account for PV potential in future upgrade interventions. The combined effect of aggregating building demand, photovoltaic generation and storage on the self-consumption of PV and net load variance was analysed using irradiation results from DIVA, metered distribution transformer loads and custom optimization algorithms. SOL is shown to be an accurate LiDAR-based model (nMBE ranging from around 7% to 51%, nMAE from 20% to 58% and nRMSE from 29% to 81%), being the isotropic diffuse radiation algorithm its current main limitation. In addition, building surface material properties should be regarded when handling façades, for both irradiance simulation and PV glare evaluation. The latter appears to be negligible in comparison to glare from typical glaze/mirror skins used in high-rises. Irradiation levels in the more sunlit façades reach about 50-60% of the rooftop levels. Latitude biases the potential towards the vertical surfaces, which can be enhanced when the proportion of diffuse radiation is high. Façade PV potential can be increased in about 30% if horizontal folded louvers becomes a more common design and in another 6 to 24% if the interconnection of PV modules are optimized. In 2030, a mix of PV systems featuring around 40% façade and 60% rooftop occupation is shown to comprehend a combined financial payback time of 10 years, if conventional module efficiencies reach 20%. This will trigger large-scale PV deployment that might overwhelm current grid assets and lead to electricity grid instability. This challenge can be resolved if the placement of PV modules is optimized to increase self-sufficiency while keeping low net load variance. Aggregated storage within solar communities might help resolving the conflicting interests between prosumers and grid, although the former can achieve self-sufficiency levels above 50% with storage capacities as small as 0.25kWh/kWpv. Business models ought to adapt in order to create conditions for both parts to share the added value of peak power reduction due to optimized solar façades.Fundação para a Ciência e a Tecnologia (FCT), SFRH/BD/52363/201

An improved algorithm for photovoltaic module temperature prediction and its techno- economic impact on energy yield

Photovoltaic (PV) system comprising PV modules and related control system is the sole means through which the solar energy is converted directly into electricity. The PV module is generally rated according to its maximum DC power output (Wp) which is obtained under Standard Test Condition. However, this condition is seldom encountered, especially in the high temperature and variable irradiance climate like Malaysia. On the other hand, in the actual operating conditions, the energy generated from PV module is sturdily influenced by surrounding climate; hence, a performance evaluation model for PV system is necessary. This research proposes a mathematical algorithm to calculate the hourly, monthly and annually expected PV system energy output, considering the actual PV module temperature (Tm) increase effect. The new algorithm was developed due to the limitation in the existing methodologies particularly the one used in Malaysia by Malaysian Green Technology Corporation (MGTC). The developed Tm prediction model is based on the pre-processed hourly data measured for 9 months at the 92 kWp Building Integrated Photovoltaic (BIPV) GreenTech Malaysia, Bangi, Selangor which includes Tm, ambient temperature (Ta), solar irradiance (G), wind speed (Ws) and Relative Humidity (RH). The developed algorithm was compared to the model used by MGTC and validated with actual measurements. In addition, 5 years of hourly data for Ta, G, and Ws measured at 6 different locations in Malaysia obtained from Malaysia Meteorological Department were used for development of a solar radiation and energy output estimation models. The proposed energy model gives good result since it is closer to measured data compared to the PVWatts simulation tool. Results on the techno-economic analysis are also presented. The proposed energy output estimation model is expected to be useful for the PV system installer in the pre-installation phase in terms of feasibility and performance analysis of the PV system