Circulation Solar Water Heating System Research Articles

00/02718 Long-term performance prediction of forced circulation solar domestic water heating systems using artificial neural networks

Photocarrier generation rate and cell reflectance models including multiple diffused reflection at the rear surface of solar cells for numerical simulation have been described. Multiple diffused reflection has been formulated using a two-directional angle distribution of light intensity. Every time the light is reflected at the rear surface, the same distribution on independent two angles is added, so that the light diffusion expands more. The conversion efficiency of sample silicon solar cells has been computed, using the two-dimensional device simulator with these models. The cell thickness dependence of conversion efficiency for the rear surface with various roughnesses has been investigated and compared with that for the planer surface.

Long-term performance prediction of forced circulation solar domestic water heating systems using artificial neural networks

The objective of this work is to use Artificial Neural Networks (ANNs) for the long-term performance prediction of forced circulation type solar domestic water heating (SDWH) systems. ANNs have been used in diverse applications and they have been shown to be particularly useful in system modelling and for system identification. Three SDWH systems have been tested and modelled according to the procedures outlined in the standard ISO 9459-2 at three locations in Greece. Two ANNs have been trained using the monthly data produced by the modelling program supplied with the standard. Different networks were used due to the different natures of the output required in each case. The first network was trained to estimate the solar energy output of the system for a draw-off quantity equal to the storage tank capacity and the second network was trained to estimate the solar energy output of the system and the average quantity of hot water per month, at demand temperatures of 35 and 40°C. The data presented as input to both networks are similar to the data used in the program supplied with the standard. The statistical coefficient of multiple determination ( R 2 -value) obtained for the training data set was equal to 0.9972 for the first network and equal to 0.9878 and 0.9973 for the second network for the two output parameters, solar energy output and hot water quantity, respectively. Other data, unknown to the network, were subsequently used to evaluate the accuracy of the prediction. Predictions with R 2 -values equal to 0.9945 for the first network and 0.9825 and 0.9910 for the second were obtained. The maximum percentage differences were 1.9 and 5.5% for the two networks respectively. These results indicate that the proposed method can successfully be used for the prediction of the long-term performance of forced circulation water heating solar systems. The advantages of this approach compared to the conventional algorithmic methods are speed, simplicity, and the capacity of the network to learn from examples. This is done by embedding experiential knowledge in the network.

Transient analysis of closed loop solar water heating system (effect of heat exchangers)

This paper presents a general and more realistic model of the transient behaviour of a forced circulation solar water heating system with and without heat exchangers in the collector loop and storage tank. The analysis has been presented for a constant flow mode. The effects of heat exchanger length and various water heating system parameters on its performance have been studied. Numerical calculations have been made for a typical cold day (26 January 1980) at Delhi.

Modelling and analysis of the dynamic behavior of a forced circulation solar water heating system with storage tanks in series

A generalized model for a forced circulation solar water heating system with storage tanks in series is presented in which the loss of heat through an insulation lagging is considered, and the periodic time variation of the intensity of solar radiation, as well as both the ambient air temperature and the temperature of cold water entering the first main tank, is taken into account. Using the Laplace transformation, an exact solution is presented which, under certain conditions, reduces to an approximate solution. The conditions for convergence to the approximate solution are discussed, and figures are presented comparing it with the exact solution for several different sets of conditions. In this communication, the effect of the number of storage tanks on the outlet temperature of the hot water and the effect of various water heating system parameters on its performance have been analytically investigated. Numerical calculations have been made for a typical cold day.

Performance and testing of a natural circulation solar water heating system

SYNOPSIS A natural circulation solar water heating system of 750 litres capacity has been designed, developed and tested. The solar collector is based on the thermosyphon principle and can provide hot water at a temperature of 80–85°C by the late afternoon. If this is stored until the following morning its temperature is still 70–75°C. The overall efficiency of the solar collector is 43%. The simple payback period for the system is between 7 months and 27 months, depending on the cost of alternative fuels.

Transient analysis of parallel plate forced circulation solar water heating system

In this paper, a transient analysis of a forced circulation solar water heating system with and without heat exchangers in the collector loop and storage tank has been presented for a parallel flat plate collector. The effect of various water heating system parameters on its performance have been studied. Numerical calculations have been made for a typical cold day viz. 26 January 1980 in Delhi.

Transient analysis of forced circulation solar water heating system with collectors in series

This communication presents an analysis of the thermal performance of a hot water system consisting of N collectors in series with a storage tank; forced circulation and withdrawal of hot water by displacement with cold water are built into the thermal model. Two modes of withdrawal of hot water, viz. (i) constant flow rate and, (ii) constant hot water temperature (during the day), have been considered. For a quantitative appreciation of the results, numerical calculations have been made for the two modes of hot water withdrawal corresponding to a typical cold day (26 January, 1980) in Delhi.

Performance ofn forced circulation water heating systems in series

This paper presents an analytical investigation of the thermal performance of a forced circulation solar water heating system in which n water heating systems are connected in series. Numerical calculations have been made for a typical cold day (26 January 1980) in Delhi, India, and some interesting conclusions have been presented.

Transient analysis of forced circulation solar water heating system

This paper presents a transient analysis of a solar water heating system with forced circulation. Two modes of hot water retrieval have been taken into account viz direct from the tank and through a heat exchanger placed in the tank. Analysis has been presented both for constant flow and constant collection temperature modes. Effects of heat exchanger length and time of starting hot water retrieval on the system performance have also been studied. Numerical calculations have been made for a typical cold day (26 January, 1980) at Delhi.

Analysis of natural circulation solar water heating systems

This paper presents an analysis of the performance of a solar water heating system with natural thermosyphon circulation between the collector and the storage tank. The analysis is based on the formulation by Ong except that provision for withdrawal of hot water from the tank (for domestic/ industrial use) has been made in the energy balance equation; further in contrast to the use of the finite difference method by Ong, explicit expressions have been obtained. The results of the present analysis (in the absence of withdrawal of hot water from the tank) are seen to be in better agreement with experiments than the corresponding results of Ong, obtained by use of the finite difference method. Numerical results, corresponding to hot water retrieved from the storage tank, have been presented for two modes of hot water withdrawal viz. the constant flow rate and constant mean storage tank water temperature.