In this paper we present a dynamic three-dimensional volume element model (VEM) of a parabolic trough solar collector (PTC) comprising an outer glass cover, annular space, absorber tube, and heat transfer fluid. The spatial domain in the VEM is discretized with lumped control volumes (i.e., volume elements) in cylindrical coordinates according to the predefined collector geometry; therefore, the spatial dependency of the model is taken into account without the need to solve partial differential equations. The proposed model combines principles of thermodynamics and heat transfer, along with empirical heat transfer correlations, to simplify the modeling and expedite the computations. The resulting system of ordinary differential equations is integrated in time, yielding temperature fields which can be visualized and assessed with scientific visualization tools. In addition to the mathematical formulation, we present the model validation using the experimental data provided in the literature, and conduct two simple case studies to investigate the collector performance as a function of annulus pressure for different gases as well as its dynamic behavior throughout a sunny day. The proposed model also exhibits computational advantages over conventional PTC models-the model has been written in Fortran with parallel computing capabilities. In summary, we elaborate the unique features of the proposed model coupled with enhanced computational characteristics, and demonstrate its suitability for future simulation and optimization of parabolic trough solar collectors.

Particle-based concentrating solar power (CSP) plants have been proposed to increase operating temperature for integration with higher efficiency power cycles using supercritical carbon dioxide (sCO 2 ). The majority of research to date has focused on the development of high-efficiency and high-temperature particle solar thermal receivers. However, system realization will require the design of a particle/sCO 2 heat exchanger as well for delivering thermal energy to the power-cycle working fluid. Recent work has identified moving packed-bed heat exchangers as low-cost alternatives to fluidized-bed heat exchangers, which require additional pumps to fluidize the particles and recuperators to capture the lost heat. However, the reduced heat transfer between the particles and the walls of moving packed-bed heat exchangers, compared to fluidized beds, causes concern with adequately sizing components to meet the thermal duty. Models of moving packed-bed heat exchangers are not currently capable of exploring the design trade-offs in particle size, operating temperature, and residence time. The present work provides a predictive numerical model based on literature correlations capable of designing moving packed-bed heat exchangers as well as investigating the effects of particle size, operating temperature, and particle velocity (residence time). Furthermore, the development of a reliable design tool for moving packed-bed heat exchangers must be validated by predicting experimental results in the operating regime of interest. An experimental system is designed to provide the data necessary for model validation and/or to identify where deficiencies or new constitutive relations are needed.

This paper presents thermal performance results of an experimental and numerical simulation study of a solar domestic hot water system (SDHW) for Canadian weather conditions. The experimental test setup includes two solar panels, a solar preheat tank, and an auxiliary propane-fired storage water heater, and an air handler unit for space heating. Experiments were performed on the SDHW system during a different season of the year, over the period March through October 2011 to assess the system performance for different solar gain and water draw schedules. Sunny, partly cloudy and cloudy conditions were explored. The test results were analysed in terms of solar fraction, solar efficiency, and the effects of thermosyphoning and stratification in the solar storage tank. Modelling and simulation of the solar thermal energy system using TRNSYS software was performed. The objective was to optimise key design parameters and to suggest an effective control strategy to maximise the heat extraction from solar collectors. The developed model was based on the experimental test setup. It was first adjusted and verified with the solar gain and water draw schedule experimental data. The results of the numerical simulations were then validated with experimental results obtained with other water draw schedule and weather conditions. Acceptable agreements between the predicted and measured values were obtained at this early stage of development. Further refinements in system and model validation are in progress in order to improve the accuracy of the predictions. Ultimately, as the final product of this investigation, this model will be used to predict the performance of solar domestic hot water and space heating systems in different Canadian locations, different operating conditions and water draw schedules.

Accurate and reliable models are necessary to predict the performance and efficiencies of concentrating solar power plant components and systems such as heliostats and central receiver systems. Heliostat performance is impacted from effects such as wind and gravity, and understanding the impact of these loads on the optical performance can yield heliostat designs that are potentially cheaper, while maintaining required structural stability. Finite element models of heliostats at the National Solar Thermal Test Facility (NSTTF) at Sandia National Laboratories in Albuquerque, NM, were developed to simulate displacements under different loading scenarios. Solidworks was used to develop the three-dimensional model of the NSTTF heliostat, and Solidworks Simulation was used to perform the finite element analysis with simulated loads along different points of the heliostat. Static displacement tests were performed on the NSTTF heliostat in order to validate these FEA models. The static test results provide us with a data set in which to properly calibrate the FEA model to better represent the NSTTF heliostat for future simulations of optical performance with impacts of wind and gravity sag. In addition to a single model validation, this real world test provides a method to validate and understand the structural stability of a heliostat under static loads.

The solid particle receiver (SPR) is a direct absorption central receiver that can provide a solar interface with thermal storage for thermochemical hydrogen production processes requiring heat input at temperatures up to 1000 C. In operation, a curtain consisting of ∼690 μm ceramic particles is dropped within the receiver cavity and directly illuminated by concentrated solar energy. The heated particles exit the receiver and may either be stored or sent through a heat exchanger to provide process heat input. The performance of the receiver is dependent on the characteristics of the particle flow including velocity and opacity (optical density). In addition, because the SPR will have an open aperture there is also a possibility that the flow may be disturbed by high ambient winds. Computational models have been and are currently being used to simulate receiver performance at power levels up to several MW t . However, due to the complex two-phase nature of the solid particle flow, such models rely on experimental data both to provide physical input, such as boundary conditions, as well as to provide a point of comparison for model validation. In this paper, we present experimental results from tests performed using a small scale unheated solid particle curtain. These tests focus on the measurement of the flow characteristics of the solid particle curtain as it falls from a near-zero velocity discharge slot to a collection point three meters below. The results include measured values for the variation of velocity, solids volume fraction, curtain width, and curtain opacity along the length of the curtain.