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# Adjustment factors for the ASHRAE clear-sky model based on solar-radiation measurements in Riyadh

Department of Mechanical Engineering, College of Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia; Energy Research Institute, King Abdulaziz City for Science and Technology, P.O. Box 6086, Riyadh 11442, Saudi Arabia

Applied Energy 10/2004; DOI: 10.1016/j.apenergy.2003.11.005 - [Show abstract] [Hide abstract]

**ABSTRACT:**Hottel’s transmittance model for beam radiation was experimentally validated for Makurdi, Nigeria. Hourly, daily, weekly and monthly average beam radiation were determined from measured total/global radiation using a daystar sun-meter over a period July and November when the sun was at the northern hemisphere. These were correlated and compared with the average predicted by Hottel’s model using analysis of variation (ANOVA) at 5% and 1% levels of significance, mean bias difference (MBD) and Root mean square difference (RMSD). The results indicated high significant differences at all levels tested with a variation of 2.9029 of the MBD and 3.1237 of RMSD and correlation coefficients of -0.8202 with measured normal radiation and -0.6397 with measured total radiation. This indicates a slim suitability of Hottel’s model in Makurdi location. Climatic factors such as humidity, seasonal variation and weather may have caused the variation because they were not directly taken into consideration in the development of the model. The model could however be used by applying appropriate correction factors that can be obtained and employed which may make up for the limitation(s) for Makurdi and other locations. A model for Makurdi location like Hottel’s is now of interestJournal of Engineering Research 01/2013; Volume-02(08):51-57. - [Show abstract] [Hide abstract]

**ABSTRACT:**In Tunisia, the energy consumption in the building sector is rapidly increasing. Recently, very high electric energy consumption, used for air-conditioning loads, is reached during summer days. Insulation of building walls is recently applied with an insulation layer thickness typically ranging between 4 cm and 5 cm, regardless of the climatic conditions, type and cost of insulation material and other economic parameters. In the present study, an optimum insulation thickness is determined under steady periodic conditions. An analytical method, based on Complex Finite Fourier Transform (CFFT), is extended to rigorously estimate the yearly cooling transmission loads for two types of insulation materials and two typical wall structures. Estimated loads are used as inputs to a life-cycle cost analysis in order to determine the optimum thickness of the insulation layer. Results show that, the most profitable case is the stone/ brick sandwich wall and expanded polystyrene for insulation, with an optimum thickness of 5.7 cm. In this case, energy savings up to 58% are achieved with a payback period of 3.11 years. The thermal performance of the walls under optimal conditions is also investigated. Then, comparison of the present study with the degree-days method is performed for different values of indoor design temperature.Applied Thermal Engineering 03/2010; 30:319-326. · 2.13 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**Thermal insulation is one of the most effective energy-conservation measures in buildings. Despite the widespread use of insulation materials in recent years, little is known regarding their optimum thickness under dynamic thermal conditions. Insulated concrete blocks are among the units most commonly used in the construction of building walls in Saudi Arabia. Typically, the insulation layer thickness is fixed at a value in the range 2.5–7.5 cm, regardless of the climatic conditions, type and cost of insulation material, and other economic parameters. In the present study, a numerical model based on a finite-volume, time-dependent implicit procedure, which has been previously validated, is used to compute the yearly cooling and heating transmission loads under steady periodic conditions through a typical building wall, for different insulation thicknesses. The transmission loads, calculated by using the climatic conditions of Riyadh for a west-facing wall, are fed into an economic model in order to determine the optimum thickness of insulation (Lopt). The latter corresponds to the minimum total cost, which includes the cost of insulation material and its installation plus the present value of energy consumption cost over the lifetime of the building. The optimum insulation thickness depends on the electricity tariff as well as the cost of insulation material, lifetime of the building, inflation and discount rates, and coefficient of performance of the air-conditioning equipment. In the present study, the effect of electricity tariff on the computed optimum insulation thickness is investigated. Different average electricity tariffs are considered; namely, 0.05, 0.1, 0.2, 0.3 and 0.4 SR/kWh (designated as Cases 1–5, respectively; 1 US$ = 3.75 Saudi Riyals). Results using moulded polystyrene as an insulating material show that the values of Lopt are: 4.8, 7.2, 10.9, 13.7 and 16.0 cm for Cases 1–5. Under the conditions of optimal insulation thickness for each electricity tariff, Case 1 gives the lowest total cost of 17.4 SR/m2, while Case 5 gives the highest total cost of 53.1 SR/m2. Corresponding thermal performance characteristics in terms of yearly total and peak transmission loads, R-value, time lag and decrement factor are presented.Applied Energy 12/2005; · 5.26 Impact Factor

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