Abstract During the last years there has been an increasing consciousness of the environmental problems, created by the use of fossil fuels in electrical power generation consumed by converting cooling systems. In addition, the use of common working fluids (refrigerants), with their ozonedepleting and global warming potential, has become a serious environmental problem. This underlines the need to implement advanced, new concepts in building air-conditioning. The most common global type of thermally driven technology to produce chilled water is absorption cooling. For air-conditioning applications, absorption systems commonly use the water/lithium bromide or ammonia/water as working pair of fluids. The objective of this study is to establish a fundamental basis for further research and development within the field of solar cooling. In this study, an overview of possible systems for solar powered refrigeration and airconditioning systems will be presented. The concept of the ‘Solar Cooling Path’ is introduced, including a discussion of the energy source to the collector. Brief information and comparisons of different absorption refrigeration cycles are also presented. A solar-driven absorption refrigeration system has been selected as a case study for a further detailed investigation. A low temperature heat source can be used to drive the absorption refrigeration cycle, making the system suitable for integration with solar thermal collector. The Transient System Simulation program (TRNSYS) and Engineering Equation Solver (EES) simulation tools are used to model and analyze the performance of a solar-driven absorption refrigeration system. Analysis of the absorption cycle system is initiated by steady-state analysis. A modeling of single effect water/lithium bromide absorption cycle was constructed to study the effect of the operating variable on the system performance and to determine the optimum operating conditions for the absorption cycle. This model was developed by Engineering Equations Solver program (EES). In practice, the ambient conditions and solar radiation are not constant. Therefore, a dynamic analysis is useful for determining the characteristics of the system during the entire year, and dimensioning the important components of the solar collector subsystem, such as storage tanks and collector area. The overall solar absorption cooling system has been simulated by the TRNSYS program with a typical meteorological year file containing the weather parameters for the capital of Libya, Tripoli. Finally, a parametric study was carried out to investigate the influence of key parameters on the overall system performance of solar absorption cooling system and hence to improve and optimize the system design. Results from the parametric optimization indicated that with an area of 130m2 of flat plate collectors with an inclination of 32° and 3.5m3 of storage tank is achieved to cover the demand of air conditioning of a 35kW absorption chiller.
إبراهيم محمد علي الطويري (2011)

Abstract Many of the concentrating solar power (CSP) systems are expected be installed in desert locations where lack of water and sand storms might be an issue. The solar reflectors are considered to be among the main effective components. The negative effects of the harsh weather conditions, including sand storms of the desert might have strong influence on the reflector properties, leading to a decrease in the thermal performance of such solar system. This thesis studies the sand storm influence on solar reflector surfaces, where two different types of Libyan sands were considered and taken from sites suitable for the installation of CSP. These sands have different shapes, sizes and chemical compositions. Sand "A" has particle sizes that vary from 0.025 to 0.355mm, while Sand "B" has particle sizes in the range of 0.124-0.479 mm. An erosion rig was designed and built at Cranfield University, UK. the tests were conducted under different simulated sand storm conditions for both sand samples. The results have shown that Sand "A" has more severe influence than Sand "B" because the smaller particles of Sand "A" help the spread out over a larger surface area of the reflector. The higher sand storm speed has more strong impact influence, while increasing the mass quantity results in less consequences. The reflectivity of the un-cleaned surface drops by 5% in case of using Sand "A" and by 7% in case of Sand "B", both at storm speed of 21m/s with specific sand mass of 18g/m3.Sand storms with the speed exceeding 6 m/s, generate sand impact on the reflector surface causing degradation to the surface, while storms with speeds less than 6 m/s, result in wakes of suspended small particles as a consequence of the transport mechanism in the atmosphere. Sealing simulation and cleaning process, using Ultrasonic Cleaner Model, show that sand "B" makes a loss of about 3% of the surface reflectivity, due to the salt-chemical composition leading to create spots and marks on the reflector surface. However, Sand "A" has recorded no chemical reaction. Sand storm history should be taken seriously, reflector surface materials should be suitable for the sites, and cleaning operations should be considered.
عصام ميلاد اندايا (2015)

This paper investigated the implementation status of Just-In-Time practices within the Libyan cement industry. The required data/information were gathered from the target factories through interviewing the most involved people in the decision making process within this business area, and through a questionnaire, developed for this survey in order to identify the actual application levels for the key-factors being considered as the most crucial for any successful and effective application. The findings showed that the cement industry suffers from many problems in managerial, manufacturing, and industrial operations. Among of them are lack of clear policies and strategic plans. Based on the findings, the paper recommended that the management body should pay more attention for providing all the requirements to qualify and train the related employees and personnel, providing the spare parts required for maintenance programs, and do not neglect the security aspect, and should focus on the safety issues within the work-place. The paper also suggested that clear policies and strategies should be well-formulated, adapting modern technologies and techniques for maximizing the efficiency and effectiveness throughout the cement industrial operations arabic 13 English 66
ٌRajab HOKOMA, Hala Mansour Amaigl(7-2018)