William S. Duff

A Markov model of solar energy space and hot water heating systems

Abstract This paper presents a Markov model approach to the generalized solar energy space heating performance analysis problem. Specifically, Markov chain models are developed to represent ambient temperature, insolation, hot water load and system performance. From the Markov transition probability matrices for these variables, long-term expected performance is calculated. The theoretical development is implemented in FORTRAN IV on a Control Data 6400 Computer System. Computational experience gained, using STOLAR 3.1 (STOchastic soLAR energy systems model), indicates the stochastic approach requires approximately five per cent of the time necessary for standard dynamic simulation approaches with comparable performance results. The method also compared favorably with FCHART, a simplified design procedure.

Focal plane flux distributions produced by solar concentrating reflectors

Abstract Efficient numeric equation-based methods of computing focal plane target flux distributions are developed for four different types of solar concentrating reflectors. Reflecting surface quality and concentrator contour accuracy are taken into account. Several approximations yield computational shortcuts so that fast-running computer programs to characterize focal plane flux distributions can be written.

Intergration of evacuated tubular solar collectors with lithium bromide absorption cooling systems

Abstract By surrounding the absorber-heat exchanger component of a solar collector with a glass-enclosed evacuated space and by providing the absorber with a selective surface, solar collectors can operate at efficiencies exceeding 50 per cent under conditions of ΔT H T = 75° C m 2 /kW ( ΔT = collector fluid inlet temperature minus ambient temperature, H T = incident solar radiation on a tilted surface). The high performance of these evacuated tubular collectors thus provides the required high temperature inputs (70–88°C) of lithium bromide absorption cooling units, while maintaining high collector efficiency. This paper deals with the performance and analysis of two types of evacuated tubular solar collectors intergrated with the two distinct solar heating and cooling systems installed on CSU Solar Houses I and III.

Solar thermal electric power systems: Comparison of line-focus collectors

Abstract Three types of line-focusing collectors: parabolic though, fixed slats with movable absorber and movable slats with fixed absorber, are evaluated to find those systems that are capable of producing the lowest costs of electrical energy. Minimum costs per kW-hr are found using sequential optimization techniques that consider variations in rim angle, reflectance, aperture width, length, orientation, tracking, contour error, slat width, slat curvature, tangent slat angle, slope, installation methods, materials, fabrication methods, absorptance, emittance, cover transmittance, field shape, layout, pipe sizes, insulation thicknesses and turbine-generator-cooling lower efficiencies and designs. This approach provides a uniform treatment of both cost and performance for a solar thermal electric power system. This uniform treatment of solar thermal electric power systems for all collector types insures that valid comparisons are made.

Heuristic approaches to solve the U-shaped line balancing problem augmented by genetic algorithms

U-shaped production line can be described as a special type of cellular manufacturing used in just-in-time (JIT) and lean manufacturing. The U-line arranges machines around a U-shaped line in the order in which production operations are performed. Operators work inside the U-line. We address the Type 1 U-LBP using heuristic rules adapted from the simple LBP. Then these heuristic approaches are compared with the optimal solutions obtained from the previous published research work. Finally the heuristic rules are used as genes to find optimal or near optimal solutions using a genetic algorithm adapted from the simple LBP genetic algorithm proposed by Ponnam-balam, Aravindan, and Mogilesswar (2000). The results showed that some very simple heuristic rules produced optimal or near optimal solutions. Then with the simple implementation of a genetic algorithm it is possible to some times obtain optimal solutions in the first iteration

Parametric performance and cost models for solar concentrators

Abstract The development of parametric performance and cost models for various solar concentrators is discussed. The equations are derived in the context of an optimization scheme which can be applied to many different problems which arise when heat is generated by means of solar concentrators. Thus, while the results presented were developed for finding a minimum cost solar electric energy power plant, the method employed has been found to have general applicability. Sensitivity analysis of the subsytems is also discussed. Finally, numerous illustrative examples are presented.

Investigation into terminating ignition coil primary magnet wire without prior removal of insulation

Concerns with stripping and soldering copper magnet wire in ignition coils and other related products have led to the investigation of an alternative product and process design called microjoining. The use of microjoining with a folded over welding tab terminal design along with a parallel gap welding process is investigated as a suitable method for joining a tin plated brass terminal to the 0.65 mm magnet wire without prior removal of the polyesterimide overcoated polyamideimide insulation.

A methodology for selecting optimal components for solar thermal energy systems: Application to power generation

Abstract A methodology is presented for determining the minimum-cost design for a solar thermal energy system. This approach builds up the minimum-cost system by adding one subsystem at a time until the desired system has been synthesized. At each step in the optimization procedure the intermediate system could be applied to an appropriate end use to find the minimum-cost design for that system. For example, a minimum-cost solar furnace could be designed. This systems optimization approach has two principal advantages over approaches that have traditionally been used for solar thermal energy systems. First, a vastly greater number of designs can be considered, and second. simplification of cost and performance models is not required. Cost and performance models may be in any form including talbes or equations that must be solved implicitly. An example of the systems optimization of the concentrator and absorber-heat exchanger subsystems is included. and the application of this approach to power generation is discussed.

Intelligent Inventory Control: Is Bootstrapping Worth Implementing?

The common belief is that using Reinforcement Learning methods (RL) with bootstrapping gives better results than without. However, inclusion of bootstrapping increases the complexity of the RL implementation and requires significant effort. This study investigates whether inclusion of bootstrapping is worth the effort when applying RL to inventory problems. Specifically, we investigate bootstrapping of the temporal difference learning method by using eligibility trace. In addition, we develop a new bootstrapping extension to the Residual Gradient method to supplement our investigation. The results show questionable benefit of bootstrapping when applied to inventory problems. Significance tests could not confirm that bootstrapping had statistically significantly reduced costs of inventory controlled by a RL agent. Our empirical results are based on a variety of problem settings, including demand correlations, demand variances, and cost structures.

A Performance and Reliability Study of a Novel ICPC Solar Collector Installation

A novel integral compound parabolic concentrator evacuated solar collector (ICPC) array has been in continuous operation at a demonstration project in Sacramento California since 1998. This paper reports on recent progress in an ongoing reliability and degradation study of the changes in performance of the array over eight years of operation. The study addresses the impact of both optical and thermal factors on array performance. Recent progress in the study includes 1) development of an animated graphical ray tracing simulation tool to investigate changes to the incidence angle modifier of the ICPC and 2) the design of a device to measure the loss of reflectivity of the internal mirrored surfaces of the ICPC.