Exergy analysis and parametric study of concentrating type solar collectors

SUMMARY

This communication presents the comparative experimental study based on energy and exergy analyses of a typical solar air heater collector with and without temporary heat energy storage (THES) material, viz. paraffin wax and hytherm oil. Based on the experimental observations, the first law and the second law efficiencies have been calculated with respect to the available solar radiation for three different arrangements, viz. one arrangement without heat storage material and two arrangements with THES, viz. hytherm oil and paraffin wax, respectively. It is found that both the efficiencies in case of heat storage material/fluid are significantly higher than that of without THES, besides both the efficiencies in case of paraffin wax are slightly higher than that of hytherm oil case. Copyright © 2011 John Wiley & Sons, Ltd.

Comparative study based on exergy analysis of solar air heater collector using thermal energy storage

In this paper we derive a general model and reliable identification procedures that can be applied autonomously for on-line forecasting of wall, zone, and whole building transient thermal responses. Several important aspects of building HVAC operation-fault detection, curtailment, verification, model-based control, and commissioning-are enabled or facilitated by use of accurate building-specific models. The methods of thermal response model identification developed in this work require little or no user intervention. Test cases for the model and identification procedures include a laboratory test room and a 60-unit apartment building in Ryazan, Russia.

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Control with building mass-Part I: Thermal response model

Analytical model, sensitivity analysis, and algorithm for temperature swings in direct gain rooms

Time Series Modelling of Solar Radiation

The optimal flat plate collector fluid flow rate is determined for several combinations of objective functions and system models. The method of implementing the control strategy for one of the problems considered, that which maximizes the integral of the difference between the collected solar power and fluid moving power, is described. The performance of the solar energy collection system in Solar House II at Colorado State University using this optimal controller is discussed and compared with the same system using bang-bang control. In addition, the dependence of the collector efficiency factor on flow rate is considered and its effect on the optimal control is determined.

Optimal Control of Mass Flow Rates in Flat Plate Solar Collectors

The effective temperature, a linear combination of a building's enclosure temperature, mean radiant temperature, and the ambient temperature, is a measure of the thermal comfort inside a building. Results from an analytical study of the relationship between the effective temperature, glazing areas, and thermal energy storage in passive solar buildings are presented in this paper. Spectral analysis is used to find the effective temperature response of a mixed-direct and indirect-gain passive solar building to Typical Meteorological Year (TMY) weather data. The response is given by the complex product of the building transfer functions and the weather inputs. Results are presented for the sensitivities of the maximum, minimum, and average daily effective temperature to changes in the direct and indirect gain glazing area and thermal energy storage.

Spectral Analysis of the Effective Temperature in Passive Solar Buildings

This paper addresses the problem of determining the optimal mix of energy conservation, passive solar, and zone heating systems in residential buildings. Analytic solutions to constrained and global optimization problems are presented. This work draws upon the Lagrangian multiplier technique used in related studies of energy conservation and passive solar design. Graphs are presented showing the optimal cost fractions for energy conservation, passive solar, and a zone heater as a function of the initial cost constraint, for a reference building in Dodge City, Kansas. The use of a zone heater is shown to reduce the annual energy requirements for space heating, and increase the life cycle savings. Also presented are design curves for the required zone heater capacity as a function of the thermal time constant for a given zone, heater response time, and interzonal heat transfer. Finally, design curves for the zone mean radiant temperature as a function of zone size, zone heater temperature, zone heater area, and interzonal heat transfer are presented.

Optimization and Design of Zone Heating Systems, Energy Conservation, and Passive Solar

An analytical method for determining the effects of temperature differentials on cycling rates for a bang-bang controller in a solar collector loop is presented. The method is an extension of previously published numerical results. The collector thermal capacitance is included in the analysis.

The effects of temperature settings on cycling rates for bang-bang controllers

The design tools that are presently available for use by designers of passive solar heating or cooling systems include detailed simulation codes, correlations derived from the detailed codes, and simulations that may be used for short-term analyses using programmable handheld calculators or desktop computers. An alternative method is based on classical frequency response techniques and yields results that are in close agreement with those that are obtained from detailed computer simulations. The method may be used to quickly determine the average temperature and the magnitude of the diurnal temperature variation in a passive solar building. The effects of parameter changes may also be quickly and easily determined by this method. The method is described in the paper and results are presented for a salb-on-grade building having a thermal storage wall and a thermal storage floor incorporating off-peak load management.

C. B. Winn

Papers

Optimal Control of Mass Flow Rates in Flat Plate Solar Collectors

Spectral Analysis of the Effective Temperature in Passive Solar Buildings

Optimization and Design of Zone Heating Systems, Energy Conservation, and Passive Solar

The effects of temperature settings on cycling rates for bang-bang controllers

A Simple Tool for the Design of Passive Solar Buildings