Mohd Yusof Othman

The availability of daylight from tropical skies-a case study of Malaysia

In Malaysia, no long-term daylight data are measured. It was only recently that the need to measure the availability of daylight became urgent when the importance of daylighting in buildings was rediscovered. The hourly daylight availability has been simulated for the Malaysian sky using daylight modelling techniques based on empirical and measured solar irradiation and cloud cover data. This paper presents the techniques involved in producing exterior illuminance data. These data were then compared with measured illuminance at Shah Alam and Bangi, Malaysia. The global illuminance levels are generally high, with values exceeding 80,000 lux at noon during the months when solar irradiation is highest. Even during the months when the ground receives less solar irradiation, the peak illuminance can reach 60,000 lux. Applications and uses of such data are in daylighting design, both for visual and thermal comfort, task illuminance and energy-conscious design of buildings. Recommendations are made at the end of the paper on the various climatic data that are required to be measured for overall daylighting design applications.

Daylighting as a passive solar design strategy in tropical buildings: A case study of Malaysia

The use of daylighting in buildings and architecture is not new. Natural lighting became out of vogue due to the availability of cheap electricity, the predictability and the ability to control illumination levels due to artificial lighting. However, the alarm over rapid depletion of energy resources and the environmental effects of their applications have led designers to reuse daylighting strategies in buildings in order to minimise energy use for lighting and air conditioning as a result of heat gains from the daylight sources and the electrical fixtures. This paper describes a study on the savings achieved by using daylight in passive solar design of buildings and, in this case, the size of windows. Simulated exterior illuminance levels based on long term measured solar irradiation and cloud cover data were used to estimate interior illumination on normal working planes using simple building configurations. Illumination on these planes decreases the need for artificial lighting, thus energy can be saved. A simple algorithm was then used to calculate the overall cooling load to ascertain that the daylighting strategies used do not invoke an increase in thermal gains through walls and glazings. The findings from this study show that at least 10% savings can be produced from simple daylighting strategies.

Thermal performance of the double-pass solar collector with and without porous media

This paper presents the thermal performance of a double-pass solar collector with and without porous media in the second or lower channel of the collector. The experimental setup has been designed to study the thermal performance over a range of design and operating conditions. Several important relationships between the design and operating conditions have been obtained. These relationships effect the thermal performance of the double-pass solar collector. The relationships include the effect of changes in upper and lower channel depth on the thermal efficiency with and without porous media. Moreover, the effects of mass flow rate, solar radiation, and temperature rises on the thermal efficiency of the double-pass solar collector have been studied. The study concluded that the presence of porous media in the second channel increases the outlet temperature, therefore increases the thermal efficiency of the systems.

Estimates of monthly average daily global solar radiation in Malaysia

Estimates of the monthly average daily global radiation for eight locations in Malaysia has been made using hours of bright sunshine. The data from Bandar Baru Bangi was obtained from the Solar Energy Research Laboratory at the Department of Physics, Universiti Kebangsaan Malaysia while others were obtained from the Meteorological Department. The least square linear regression analysis was used for the eight cities to obtain the relationship between the monthly average daily global radiation and sunshine duration data. The Angstroms correlation obtained for the eight cities can be used for any solar energy application in Malaysia.

Drying of Malaysian Capsicum annuum L. (Red Chili) Dried by Open and Solar Drying

This study evaluated the performance of solar drying in the Malaysian red chili (Capsicum annuum L.). Red chilies were dried down from approximately 80% (wb) to 10% (wb) moisture content within 33 h. The drying process was conducted during the day, and it was compared with 65 h of open sun drying. Solar drying yielded a 49% saving in drying time compared with open sun drying. At the average solar radiation of 420 W/m2 and air flow rate of 0.07 kg/s, the collector, drying system, and pickup demonstrated efficiency rates of approximately 28%, 13%, and 45%, respectively. Evaporative capacity ranged from 0.13 to 2.36 kg/h, with an average of 0.97 kg/h. The specific moisture extraction rate (SMER) of 0.19 kg/kWh was obtained. Moreover, the drying kinetics of C. annuum L. were investigated. A nonlinear regression procedure was used to fit three drying models. These models were compared with experimental data on red chilies dried by open sun drying and those dried by solar drying. The fit quality of the models was evaluated using their coefficient of determination (), mean bias error, and root-mean-square error values. The Page model resulted in the highest and the lowest mean bias and root-mean-square errors.

A review on photovoltaic thermal collectors

The content of this review consists of the types and the parameters influencing the performance (electrical and thermal) and also covers the numerical, analytical, and experimental models of photovoltaic thermal (PVT) collectors. The PVT systems using air and water as heat extraction agents were discussed. The parameters affecting the PVT performance such as the glazing, mass flow rate, and influence of absorber and design types were discussed in details. From the exergy analysis, it was found that the unglazed collector gives better total (electrical+thermal) exergy, whereas the energy analysis favors the glazed collectors. From the literature review, it is obvious that the PVT systems are very useful in the future. There are no substantial initiatives taken in order to reduce the cost and to make PVT collectors favorable. Increasing the competitiveness of PVT collectors will enhance the utilization of renewable energy devices. This communication was done to ease future studies to be conducted by researc...

Diurnal pattern of global solar radiation in the Tropics : a case study in Malaysia

Global solar radiation patterns in Bangi (2°56′7.3″N, 105°47′0.2″E), Malaysia are discussed. The frequency of occurrence of the various solar radiation patterns observed over a 5-year period is derived. These observations will provide useful information for the design of solar energy systems and equipment for installation in tropical countries having a similar global solar radiation pattern.

The bioclimatic design approach to low-energy buildings in the Klang Valley, Malaysia

Formulating passive energy design strategies require an understanding of the climatic influence on buildings and the thermal comfort of their occupants. This paper presents the bioclimatic approach in building design as well as the techniques which are applied to formulate various strategies in order to achieve indoor comfort conditions. The paper deals with the Bioclimatic Chart, the Building Psychrometric Chart, Mahoney Tables and the Control Potential Zones which utilise the thermal neutrality concept. Regional climatic data from the Klang Valley area in Malaysia were utilised in formulating the design strategies. The most appropriate design strategies for hot, humid regions were then deduced. The most preferred strategies found were the use of ventilation, dehumidification and shading. Consequently, a full recommendation for the integral use of these three passive methods are suggested to be used in all buildings in Malaysia.

Design of an experimental solar assisted dryer for palm oil fronds

This paper presents the design of an experimental solar assisted dryer for palm oil fronds. The system consists of collector, a dryer, an auxiliary burner and a fan. The collector is of the double-pass configuration with porous media in the lower channel. The dryer is of the batch type where hot air introduced from the bottom. The size of the collector is 120 cm width and 240 cm in length. The upper and lower channels are adjustable for optimal operations. The size of the dryer is 100 cm width, 100 cm long and 80 cm in height. The project is funded by the Malaysian government and will be carried out at the Solar Energy Research Park University Kebangsaan Malaysia, Bangi.

Fabrication and Irradiance Mapping of a Low Cost Solar Simulator for Indoor Testing of Solar Collector

The fabrication and testing of a solar simulator for indoor testing of solar collector are described. Consisting of Philips 500 W halogen lamps with built-in reflector, which are arranged at 30 cm apart, the system covers a test area suitable for a solar collector of size 120 cm by 53 cm. The height of the lamps above the solar collector under test is set to 160 cm. Measurement of the uniformity of the irradiance over the test area has been made. Four sets of irradiance mapping were performed at 466, 580, 686, and 804 W/m2 , yielding at each point the irradiance uniformity percentage of 8.9, 7.6, 6.9, and 7.8%, respectively. The infrared radiation produced by the lamps was filtered by air flowing over the test area.