Solar Domestic Water Heating Systems Research Articles

Inexpensive Performance Monitoring of Solar Domestic Water Heating Systems

Performance monitoring is essential in order to conclusively demonstrate the cost effectiveness of a solar heating system. Unfortunately, this “last step” is an aspect which has received little engineering consideration. The monitoring programs in progress typically use instrumentation which is much too expensive and complex for use by individual operators of domestic water heating systems. Hence, few systems are monitored, and the average owner knows little about the performance characteristics of his system. Even malfunctions go undetected. An inexpensive performance monitoring system is described in this paper. It could probably be mass-produced for under 15 dollars or built by the typical homeowner for under 30 dollars. The monitor indicates the instantaneous solar fraction. Overall system performance can be improved with this monitor, since it enables the user to correlate load with the availability of solar heated water. Methodology, performance parameters, and some performance data are presented.

Measured and Simulated Performance of a Solar Domestic Hot Water System

A commercially available solar domestic hot water heating system installed in a private residence in Vancouver. Canada has has been intensively monitored over a four month period. Simulation of the system was performed using a modified version of the WATSUN-3 Domestic Hot Water (DHWA) model. Model predictions are compared against actual system measurements on an hourly and daily basis. Reults show that the model is able to consistently track thermal conditions within the system and is capable of predicting system performance to within 5 percent.

Optimal sizing of a collector for a solar domestic water heating system

Optimal sizing of a collector for a solar domestic water heating system

Performance analysis of a solar air-conditioned villa in the arabian gulf

An integrated system which utilizes three types of solar energy subsystems for the purpose of air-conditioning (i.e. heating and cooling) in residential buildings has been designed, installed and tested in the KISR solar house, Kuwait. The three systems are: (a) a solar photovoltaic power system, (b) a solar air heating and rock storage system and (c) a solar water heating, cooling and domestic water heating system. This paper gives a general survey of the design and operation of the solar energy systems. The performance of the different solar energy systems is reported in terms of collector efficiency, solar energy contribution and the use of electrical energy to operate the solar equipment and of fossil fuels to back up the operation of the solar energy system. The general characteristics of the three types of systems are also compared. Information concerning installation, operation and maintenance of the systems has been discussed.

A Rating Procedure for Solar Domestic Water Heating Systems

A rating procedure for solar domestic hot water systems is described which combines the advantages of short-term system tests and correlations of long-term thermal performance. The testing procedure consists of two indoor tests which are in accordance with ASHRAE Standard 95-1981, except for one additional measurement needed only for systems employing a heat exchanger between the collector fluid and the potable water. The test results are plotted in a manner in which they can be used to estimate the long-term performance of the solar water heating system for any location where site-specific, monthly-average meterological data are available. The annual solar function obtained in this manner provides the recommended rating indicator. The validity of this rating procedure is first demonstrated by simulations. Further support is provided by experiments conducted at the National Bureau of Standards.

Comparison of actual and predicted performance of five domestic hot water systems

SYNOPSIS Performance data has been obtained on five solar domestic hot water heating (DHW) systems for a period of approximately three years In Rhode Island. Actual physical performance has been analysed using computer techniques and compared to F-CHART predictions [1] using actual loads and state-wide insolation rates for the period under study. Brief descriptions of the systems, a sample data set, the results of the analyses, and a comparison of actual performance with calculated predictions for each system are presented While F-CHART predictions are generally higher than actual performance estimates for four of the five systems under study, the results are consistent with experimental and computational uncertainties and known systematic effects in the theoretical analysis.

Speeding the diffusion of solar energy innovations

Solar energy innovations are likely to concern public and business policy makers in the decade ahead. Sooner or later, the focus of concern must move from the general to the specific, from the macro- to the micro-environment, from the national level to the regional and state levels. A diffusion of innovations framework is presented and discussed as an approach capable of explaining and increasing the market share of solar energy innovations. Solar domestic water heating systems serve as an illustrative example.

Technocracy versus reality: Perceptions in solar policy

The task of identifying Federal solar policy and research priorities has been delegated consulting firms, university researchers and technical laboratories. Solar commercialization policies for the residential sector have been a major focus of these entities' efforts; yet their research methodologies have generally ignored the advice and experience of homeowners who have installed solar domestic water and space heating systems. The absence of such input raises the question of how accurately the research community has evaluated the impact of specific barriers and incentive policies to residential solar use. Three surveys compared the planning community's assessments of the barriers and incentives to those of homeowners who had personally experienced the entire solar purchase, installation and operation sequence. Despite the potential for error, no major dichotomy was found to exist between the planning community's perceptions and those barriers and incentives actually extant.

Solar energy for domestic water heating in Ireland

SYNOPSIS This paper deals with the approach taken, the equipment and controls used, the problems encountered and the performance to-date of the solar domestic water-heating systems at present being monitored by the Electricity supply Board in Ireland. It will be seen how the problem of an unsuitable roof orientation was overcome and why it is necessary to ensure that the control equipment is of a high quality. The performance of some of the systems has been disappointing while others have proved themselves extremely well. The initial costs of purchasing and installing a solar water-heating system and the estimated payback period are both given. Finally, there is a review of the experience gained so far, and the future work which will be undertaken is set out.

Analysis of solar domestic hot water heaters

The performance of several generic types of solar domestic water heating systems is compared using a simulation approach. Types of systems studied included those using single and double tanks and those using direct and indirect methods of transferring solar heat to potable water. In addition, the effects of collector area, tank size, tank insulation, tempering valves and load distribution are studied. A modification to the f-chart design method is developed. This modification allows variation in tank insulation to be considered in the design method. Simulation results are compared, on a quantitative basis, with performance predictions generated by the f-chart design method modified in this manner. In addition, experimental results from the U.S. National Bureau of Standards are compared, on a qualitative basis, with simulation results, and, on a quantitative basis, with f-chart performance predictions.

The solar bath-tap

A conventional solar domestic water heating system can be retro-fitted with a third, solar tap over the bath. When a bath is being mixed, if water from the solar tap is now included in the mix instead of cold water, then draw-off of hot tap water is reduced. Total usage of solar water is simultaneously increased, lowering the solar store's average temperature. This results, at the collector, in increased operating time and efficiency, lowering the long term usage of auxiliary energy. The energy saving is analysed and significant parameters are derived. The effect of storage capacity on this saving is discussed. An example of retrospectively adding a solar bath tap is worked out, based on a U.K. home with four occupants. The marginal rate of return on the cost of the modification is in this case shown to be about double the rate of return on the cost of the basic solar system. In the case of an initially fitted solar bath tap, advantage is shown to arise from a small associated increase in storage capacity.

Optimal sizing of solar collectors by the method of relative areas

A method is presented for calculating directly, without iteration, the approximate collector area which minimizes the total life-cycle cost of an active solar space and/or domestic hot water heating system. The method is based on an empirical relationship between annual solar load fraction and relative collector area. This relationship was determined by correlating data that were generated by the Klein, Beckman and Duffie F-Chart program, which in turn is based on a correlation of digital computer simulation results. The calculations may be performed in a few minutes using a hand-held calculator. Required data are tabulated for 170 locations, and a solved example is included. Compared to results from the F-chart program, deviations of total life-cycle costs from the minima are typically less than 3 per cent. Uncertainty of future energy prices is regarded as the limiting factor in the accuracy of the optimization calculations. A detailed economic analysis is included.

A computer study of solar water heating

A computer model of a domestic solar water heating system was used to investigate the effect of changes in design parameters on the performance of the system. The theor y underlying each component of the model is described and the approximations made are discussed. The model showed that annual heat output was highly dependent on the total collector area of the system but that other changes, in collector slope, orientation, storage tank volume etc, had relatively small effect. The daily pattern of demand for hot water was also shown to influence performance.