An investigation of the technoeconomic feasibility of solar domestic hot water heating for the Canadian housing stock

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.

Performance Evaluation of an Advanced Roof Integrated Solar Hot Water Heating System and Roof-Mounted Solar Photovoltaic Power System in New Home Construction

Solar heating systems are widely used in several European countries for domestic hot water heating, and in the past decade, an increasing number of solar combined space and hot water heating systems (typically referred to as “combisystems”) have begun to take precedence. In Canada, however, the majority of all residential solar thermal installations are for heating domestic hot water. To date, various combisystem configurations have been investigated under the auspices of the International Energy Agency, Task 26 and Task 32. Within these tasks, various system configurations were modelled and test procedures developed to allow standard performance evaluations to be conducted. This work, although extensive, has limited application within the North American context. At present, little research has been conducted on the applicability of these systems for residential housing. In particular, due to Canada’s more severe winters, larger solar collector arrays would be required to significantly contribute to the space heating load. This has drawbacks, as much of the solar capacity would not be utilized during the summer, leading to poor economic performance and possible overheating that could accelerate degradation or scald occupants. Therefore, there is a need to optimize the configuration of solar combisystems to avoid over-sizing while maximizing the utilization of solar energy in a safe and economic manner. This paper presents a review of the current literature on solar combined space and domestic hot water heating systems, with a particular emphasis on the work which has been conducted by the International Energy Agency. In addition, a review of combined space and domestic hot water systems currently installed in Canada are also discussed.

Plume entrainment effects in solar domestic hot water systems employing variable-flow-rate control strategies

Water conservation in solar domestic hot water systems

Data from an indoor solar simulator experimental performance test is used to develop a systematic calibration procedure for a computer model of a thermosyphoning, solar domestic hot water heating system with a tank-in-tank heat exchanger. Calibration is performed using an indoor test with a simulated solar collector to adjust heat transfer in the heat exchanger and heat transfer between adjacent layers of water in the storage tank. An outdoor test is used to calibrate the calculation of the friction drop in the closed collector loop. Additional indoor data with forced flow in the annulus of the heat exchanger leads to improved heat transfer correlations for the inside and outside regions of the tank-in-tank heat exchanger. The calibrated simulation model is compared to several additional outdoor tests both with and without auxiliary heating. Integrated draw energies are predicted with greater accuracy and draw temperature profiles match experimental results to a better degree. Auxiliary energy input predictions improve significantly. 63 figs., 29 tabs.

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.

Solar domestic hot water heating is currently desired and widespread way of using clean energy sources in the Slovak Republic. Control of solar domestic hot water heating systems is often solved trivially and does not address the safety and efficiency. System with drain-back tank and solar collectors with evacuated tubes is an advanced solution meeting the requirement of autonomous safety, environmental friendliness and efficiency of operation. It addresses possible emergencies occurring in other types of solar systems and allows system regeneration to the operating state without operator's intervention. At the same time this system brings its own set of issues with control and its quality requirements.

In this article, the research object is the solar domestic hot water (SDHW) heating system that has been in operation since 2015 and is located on the campus of the Bialystok University of Technology (Poland). The thermal performance of solar collectors are thoroughly investigated so far. Therefore, special attention was paid to the issue of the heat loss from pipes. The measurements showed that the heat transfer in circulation pipes is quite complex due to continuous fluctuations in water temperature at the supply of this loop. As it turned out, the application of the classical method of energy balancing and the readings from heat meters gave inaccurate results in this case. The main aim of this study was to develop a different approach to solving the problem of determination of heat losses. The method presented in this article is based on computational fluid dynamics (CFD) and measurement results as the input data. The practical result of this study was the development of two relationships for calculating the heat loss from pipes. A separate issue, that is discussed in this paper, concerns the impact of the time intervals used in numerical simulations on the accuracy of calculation results.

System design optimization for large building integrated solar heating systems for domestic hot water

This report describes work performed in FY 1984 at the Solar Energy Research Institute as part of the continuing effort to lower the delivered energy cost of solar domestic hot water and space heating systems. In this work, a cost and performance comparison of drainback and integral collector storage (ICS) systems was conducted. Cost data for installed system costs were developed for both systems. Performance for the systems was generated using either accepted design tools (FCHART for drainback systems) or new methodologies (for the ICS systems). The cost and performance data were used to calculate discounted payback as a means for comparing the two systems and for assessing their market potential. The results of this economic analysis show that ICS systems have lower discounted paybacks than commercially available drainback systems. Low-cost drainback systems using new, low-cost components have about the same discounted payback as ICS systems.

Computer simulation of a two phase thermosyphon solar domestic hot water heating system

The active solar Domestic Hot Water (DHW) and space heating system at the Eisenhower Museum was designed and constructed as part of the Solar in Federal Buildings Program (SFBP). This retrofitted system is one of eight of the systems in the SFBP slected for quality monitoring. The purpose of this monitoring effort is to document the performance of quality state-of-the-art solar systems in large federal building applications. These systems are unique prototypes. Design errors and system faults discovered during the monitoring period could not always be corrected. Therefore, the aggregate, overall performance is often considerably below what might be expected had similar systems been constructed consecutively with each repetition incorporating corrections and improvements. The solar system is a retrofit, designed to supply part of the space heating (and reheating for humidity control) load at the museum, located at President Eisenhower's boyhood home in Abilene, Kansas. The small DHW load is also served by the solar system. The museum and adjacent library entertain approximately 200,000 visitors per year, and require controlled temperature and humidity for preservation of artifacts. The summer reheating load for humidity control is comparable to the space heating load in winter. The solar system has 110 US Solar flat plate collectors with a gross area of 4201 square feet, using ethylene glycol as the collector fluid. The energy from the collector loop is transferred to two 1980 gallon storage tanks via an external heat exchanger. Solar energy is used for DHW preheating and for space heating. Highlights of the performance monitoring at the Eisenhower Museum during the period March 1985 through September 1985 are summarized in this report.

Net energy analysis of a solar combi system with Seasonal Thermal Energy Store

The operating efficiency of evacuated tubes themselves under varying environmental conditions and installation scenarios, independent of water and space heating auxiliary equipment, are not readily available values. Further, Manitoba specific data has not been established. The purpose of this research program was to measure the efficiency of evacuated tube solar collectors under various operating conditions including: the angle of inclination towards the incident solar radiation, heat transfer fluid flow rate, glazing installation, and number of evacuated tubes. The operating conditions and configurations were chosen to represent realistic or probable installation scenarios and environmental conditions. Furthermore, the research aimed to identify the suitability of evacuated tube solar collectors to each of the scenarios. These design values are of use for appropriate sizing of water or space heating systems, system configuration and optimization, and calculation of return on investment. The scope of the research project was limited to the efficiency of various configurations of a 32-tube panel, not the entire solar domestic hot water or space heating system. Thus, factors such as heat loss in the tubing, solar storage tank, and heat exchanger efficiency were not investigated. The findings indicated that efficiency varied by approximately 5% between the different collector configurations, as observed from the overlay graph of results. When the efficiency of a collector is considered within a system it is proposed that effectiveness may be a better measure of overall performance.