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A new passive solar water pasteurization system based on density difference flow principles has been designed, built and tested. The system contains no valves and regulates flow based on the density difference between two columns of water. The new system eliminates boiling problems encountered in previous designs. Boiling is undesirable because it may contaminate treated water. The system with a total absorber area of 0.45 m2 has achieved a peak flow rate of 19.3 kg/h of treated water. Experiments with the prototype systems presented in this paper show that density driven systems are an attractive option to existing solar water pasteurization approaches.

In 1998 two new technologies were demonstrated for the first time in a commercial building: (1) a new integrated CPC reflector evacuated solar collector (ICPC) and (2) the solar operation of a double effect absorption (2E) chiller. The 106.5 m2 ICPC collector array consisted of 336 evacuated tubes. A commercial 2E gas-fired absorption chiller was modified to operate with 150 °C hot water from the solar collector array. Daily collection efficiencies of nearly 50% and instantaneous collection efficiencies of about 60% were achieved throughout the first two years of operation. Daily chiller COPs of about 1.1 were also achieved.

Two first order nonlinear controllers are introduced: partial state setting and error modulated state setting. Both controllers smoothly combine feedforward steady state predictions with integral control. In both controllers the mixing is controlled though the use of a single gain that determines how aggressively the steady state predictions are used. Steady state error bounds are presented for each controller. For error modulated state setting control steady state errors can be eliminated if the maximum expected error in the steady state predictions is known. Both controllers are demonstrated to improve the transient response of a simulated nonlinear second order variable gain plant when compared to a well tuned proportional plus integral controller.Copyright © 2012 by ASME

Part 3: Data Mining; International audience; 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.

Short-term experimental tests of drain-back solar water heaters are compared to ratings obtained using TRNSYS to determine if computer simulations can effectively replace laboratory thermal ratings of solar domestic hot water heating systems. The effectiveness of TRNSYS in predicting changes in rating due to limited changes in collector area, collector flow rate, recirculation flow rate, storage tank volume, and storage tank design is validated to within ±10 percent. Storage tank design is varied by using a stratification manifold in place of the standard drop tube. Variations in other component sizes and operating factors are based on current industry standards.

In this paper a half-factorial, two-level experimental design is used to determine the effects of changes in collector area, storage tank volume, collector flow rate, recirculation flow rate, and storage tank design on thermal rating of a solar drain-back water heating system. Experimental ratings are determined in accordance with the Solar Rating and Certification Corporation guidelines. Storage tank design is varied by using a stratification manifold in place of the standard drop tube. Variations in other component sizes and operating factors are based on current industry standards. Statistical analyses indicate that a change in collector area accounts for nearly 90 percent of the variation in heat output. Doubling collector area from 2.78 m[sup 2] to 5.56 m[sup 2] increases delivered solar energy by 31 percent. Use of a stratification manifold increases the delivery of solar energy by six percent. Doubling collector flow rate from 0.057 to 0.114 1/s increases solar output by aproximately three percent; however, the increase in pumping energy outweighs the benefits of increasing collector flow rate. The effects of recirculation flow rate and tank volume are obscured by experimental error.

Water-borne pathogens in developing countries cause several billion cases of disease and up to 10 million deaths each year, at least half of which are children. Solar water pasteurization is a potentially cost-effective, robust and reliable solution to these problems.

A solar water pasteurization system with a total collector area of 0.45 m2 , an operating temperature of 80°C, and a holding time of 30 seconds has been constructed. The system was most recently tested in Fort Collins, Colorado during September/October of 2003. The system is capable of producing 80–90kg of treated water during a sunny day. To establish the potential effectiveness of the system, studies on the thermal resistance of waterborne pathogens that the World Health Organization has classified as having high health significance have been assembled and evaluated. It was determined that the process should be highly effective against most enteric pathogens. However, more information is needed about thermal resistance of some important virus families.Copyright © 2004 by ASME

A new passive solar water pasteurization system has been designed, built and tested. The system contains no valves and regulates flow based on the density difference between two columns of water. The new system eliminates boiling problems encountered in previous designs. Boiling is undesirable because it may contaminate treated water. The system has produced over 100 liters per day of treated water with a collector area of 0.45m2 . Work is ongoing to develop a theoretical understanding of system behavior, to analytically model it and to further improve system performance.Copyright © 2003 by ASME

In 1998 two new technologies were demonstrated for the first time in a commercial building: a new ICPC solar collector and the solar operation of a double effect (2E) chiller. The demonstration project in Sacramento has now been in operation for almost five years. Daily collection efficiencies of over 50 percent, instantaneous collection efficiencies of over 60 percent and daily chiller COPs of about 1.1 have been achieved.Copyright © 2003 by ASME

A sequential optimization approach to finding minimum cost solar collector fields is presented. Minimum cost fields are found for various values of useful thermal power as measured by the fluid mass flow rate and temperatures in and out of the field. The optimum piping arrangements, field geometries, mixes of collector types, pipe diameters and insulation thicknesses are determined for each minimum cost field. Examples of the application of the optimization approach are also presented.

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.

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.

A dynamic programming methodology is presented for finding minimum cost solar thermal electric power systems ’(STEPS). The objective of the study for which this technique was developed was to identify designs of STEPS concepts that were most promising in terms of projected cost per kilowatt hour of electricity generated.

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, HT = 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.

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.

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.

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.

A novel geometry ICPC evacuated tube solar collector was developed at the University of Chicago and Colorado State University in 1993. Individual evacuated tubes of this novel geometry ICPC were experimentally fabricated and tested at Colorado State University in 1994-96 and at the University of Chicago in 1996-97. In 1998 two 14 tube modules were tested on Sandia National Laboratory's two-axis tracking (AZTRAK) platform in Albuquerque New Mexico by Sandia National Laboratory and the University of Chicago. A 336 tube 100 m2 array of this collector has been in continuous operation at a demonstration project in Sacramento California since 1998. From 1998 to the present performance of the Sacramento demonstration array and single and double effect cooling systems has been monitored and evaluated by the California State University at Sacramento and Colorado State University. Optical ray tracing modelling, thermal performance modelling and collector reliability studies have been conducted by Colorado State University during the 1998 to 2013 period. Performance approaching the theoretical predictions was achieved for the individual ICPC evacuated tubes experimentally fabricated by Colorado State University and the University of Chicago. While operating in the range of 120 to 160C, daily solar collection efficiencies of nearly 0.50 and instantaneous solar collection efficiencies of about 0.60 were achieved. Daily cooling COPs of 1.1 were achieved while operating the double effect chiller with energy supplied from the ICPC solar collectors. A ray tracing simulation incorporating ray transmittance and translation, the gap between the glass tube and fin, reflectivity of the reflective surface, absorptivity of the fin and blocking and displacement of the rays by adjacent tubes has been developed. Animation of individual rays and associated summary graphics and an optical and thermal performance model of the collector have also been developed. Performance of the novel ICPC solar collector at various specified angles along the transverse and longitudinal evacuated tube directions was experimentally measured on the Sandia National Laboratory's two-axis tracking (AZTRAK) platform. Data from the Sandia tests was used to validate the ray tracing simulation performance. Data from the initial operation of the Sacramento array were used to further validate the ray tracing simulation and thermal modelling. The primacy of the two identified collector reliability failure modes was established. Details of the various testing and research activities and results are presented. Animations of the ray tracing are also included in the oral presentation.

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 percent of the time necessary for standard dynamic simulation approaches with comparable performance results. The method also compared favorably with FCHART, a simplified design procedure.

There have been a number of research and development areas where recent activities have led to or are apparently about to lead to significant advances in the use of domestic solar heating and cooling technologies. Activities in the following areas are discussed: systematic improvements in solar energy system performance, evacuated collectors, flat plate collectors with convection suppression, microflow domestic hot water systems, desiccant cooling, and modeling. The examination of these areas leads into a discussion of future research needs.

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% under conditions of δT/HT = 75°C·m2/Kw (δT = collector fluid outlet temperature minus ambient temperature, HT = 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 integrated with the two distinct solar heating and cooling systems installed on CSU Solar Houses I and III.