Results and Discussion

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The solar heating and cooling system is designed to satisfy the needs of space heating, water heating, and air conditioning loads for a family in a typical Kuwaiti house. The weather data file for Kuwait is provided by Kuwait Institute for Scientific Research (2006). The weather file contains monthly average values of daily radiation on horizontal surface, clearness index, ambient temperature, and wind speed. The weather data generator subroutine included in TRNSYS package is used to generate hourly data from the available average monthly data for Kuwait

The thermal performance of a solar system is usually measured by the solar fraction (F). Solar fraction is defined as the fraction of load met by solar energy. Figure 28.3 shows the variation of the solar fraction of space heating (Fs), domestic water heating (FD), and cooling load (FAc) as well as the total solar fraction (Ft) with collector area. As seen from the figure, a significant portion of the solar fraction for space heating and domestic water heating is satisfied at areas around 38 m2. Conversely, the space cooling requires much greater areas.

The variation of total solar fraction, life cycle savings, and overall system efficiency (ratio of solar energy provided to the total incident radiation) with collector area is presented in Fig. 28.4. This typical figure shows the choice of optimum collector area which is approximately equal to 38 m2 in this case. It is clear from this figure that this optimum area neither corresponds to maximum system efficiency nor to the maximum solar fraction.

Fig. 28.3 Solar fraction variation with collector area.
Solar Radiation Variability

Fig. 28.4 Variation of system parameters with collector area.

Fig. 28.4 Variation of system parameters with collector area.

Also, the total solar fraction (Ft) for flat plate solar collector satisfies a great portions of the load about 0.76. The collector efficiency (nc) behaves the same as the system efficiency with slightly higher numerical values. Finally, the coefficient of performance (COP) of the absorption chiller is approximately 0.64 which is within the accepted practical values of the conventional lithium bromide system. The life cycle cost of the conventional and the solar system varies significantly due to the corresponding variation of the total load. The value of life cycle savings (LCS) is found to be $1900 per year for the optimum conditions. In this study, the cost of unit energy provided by solar heating and cooling system, i.e., the cost of 1 kW h provided by the proposed solar system is about $0.017/kW h which represents 68% of the value provided by the conventional fuel system ($0.025/kW h). These results prove the feasibility of the solar heating and cooling systems in Kuwait climate.

The variation of annual avoided CO2 emission with collector area is presented in Fig. 28.5. The figure again illustrates that the optimum area which maximizes the avoided CO2 emission is 38 m2. At this optimum area, the avoided CO2 emission has been found to be approximately equal to 9.7 ton/year. This corresponds to a reduction cost of $10.3/ton which is comparable to the values reported in the literature (Narula et al., 2002).

20 25 30 35 40 45 50 55 60 65 Collector Area (m2)

Fig. 28.5 Avoided CO2 emission variation with collector area (azimuth angle=0).

20 25 30 35 40 45 50 55 60 65 Collector Area (m2)

Fig. 28.5 Avoided CO2 emission variation with collector area (azimuth angle=0).

In addition, the costs due to the application of the Kyoto Protocol, which penalizes the emissions of greenhouse effect gases, fundamentally CO2, should be added to the costs of conventional energy resources. In spite of the fact that Kyoto Protocol is not currently applied in Kuwait, however, considering application of this protocol will enhance the economical and environmental aspects of solar heating and cooling systems much more. Application of Kyoto Protocol will force various productive sectors specially electrical and industrial sectors to pay for CO2 emissions making solar heating and cooling systems more feasible in Kuwait climate.

The present results should encourage governments for wide installation of solar heating and cooling systems in different applications which will reduce energy consumption of conventional fuel as proved by the results of this analysis. In addition, wide utilization of solar energy systems will help in reducing environmental pollution.

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