Renewable and Sustainable Air Conditioning

The simultaneous control of air temperature and humidity are the main functions of an air conditioner in order to provide human thermal comfort conditions. The conventional vapor compression air conditioning system cools the air below its dew point temperature to remove the moisture from the air. In hot and humid regions, considerable amount of energy is used for moisture removal using these systems. Because of the high energy cost of conventional systems and poor control of latent load, need arises for some alternative cooling devices. In this chapter alternative and renewable based air conditioning systems are described to overcome the increasing use of primary energy by conventional air conditional systems. Desiccant cooling is found to be a suitable alternative to these cooling systems. The configurations of desiccant cooling systems to achieve better performance are described. Furthermore, a comparative analysis of desiccant cooling system operating on ventilation and recirculation cycle has been presented. The results showed the system operating under the ventilation cycle has a better coefficient of performance as compared to the recirculation cycle because of the less input/regeneration heat required. The desiccant cooling technology is both cost-effective and environmental friendly as no refrigerant is used in these systems

Artificial neural network estimation of global solar radiation using air temperature and relative humidity

Measured air temperature and relative humidity values between 1998 and 2002 for Abha city in Saudi Arabia were used for the estimation of global solar radiation (GSR) in future time domain using artificial neural network method. The estimations of GSR were made using three combinations of data sets namely; (i) day of the year and daily maximum air temperature as inputs and GSR as output, (ii) day of the year and daily mean air temperature as inputs and GSR as output and (iii) time day of the year, daily mean air temperature and relative humidity as inputs and GSR as output. The measured data between 1998 and 2001 were used for training the neural networks while the remaining 240 days' data from 2002 as testing data. The testing data were not used in training the neural networks. Obtained results show that neural networks are well capable of estimating GSR from temperature and relative humidity. This can be used for estimating GSR for locations where only temperature and humidity data are available

Wind shear coefficient, turbulence intensity and wind power potential assessment for Dhulom, Saudi Arabia

The study presents the local values of wind shear coefficient (WSC) estimated using wind speed measurements made at 20, 30 and 40 m above ground level (AGL) during November 01, 1998 and October 12, 2002. The study also includes the local values of air density calculated using temperature and pressure measurement made at 2 m AGL during the same period. The mean wind speed above 4 m/s and the standard deviation values were used to obtain the turbulence intensities (TI) at different heights. These local values of WSC were used to estimate the wind speed at hub-height of the wind turbines used in this study. Energy yield was calculated for a hypothetical wind form of 60 MW installed capacity assumed to be consisting of 100, 60 and 30 wind turbines of 600, 1000 and 2000 kW from DeWind, respectively. The study recommends a value of WSC of 0.255 for the estimation of wind at different heights AGL and local air density of 1.06 kg/m3 The WSC values were found to be higher during nighttime and smaller during daytime while no evident seasonal trend could be identified. In case of air density, no diurnal change was evident but a seasonal trend, with higher values in winter and lower in summer months, was evident. The annual energy yield obtained using wind speed at different hub-heights calculated with WSC = 0.255 was found to be 10-20% higher than the yield obtained with wind speeds calculated with WSC = 0.143 corresponding to hub-heights of 60 and 100m, respectively. Similarly, higher plant capacity factors (PCFs) were obtained for energy yield estimated using WSC = 0.255 compared to that with WSC = 0.143. Higher values of TI were obtained during day time and lower during nighttime. Furthermore, lower values were obtained during November to March and higher during rest of the year. Finally, a decreasing pattern was observed in the values of TIs with increasing height

Application of Discrete and Continuous Wavelets for Saudi Arabian Meteorological Data Analysis

This paper presents the wavelet-based analysis of meteorological parameters for nine meteorological stations in Saudi Arabia. The study utilised the daily mean values of pressure, temperature, relative humidity and wind speed data over a period of 16 years between 1990 and 2005. In case of rainfall data, daily total values were used. The time series of meteorological parameters has so much noise that their overall shape is not visible upon visual inspection. It has been observed in the present investigation that trends become more and more readable at decomposition at different scales. The wavelet tools have been used to reveal the trends of the meteorological data time series. If the signal itself includes sharp changes then successive approximation look less and less similar to the original signal. This paper deals with the meteorological data visualisation. such as pressure, temperature, relative humidity, rainfall and the wind speed time series of the Kingdom of Saudi Arabia. The present analysis is based on discrete and continuous wavelet transforms

Wind shear coefficient, turbulence intensity and wind power potential assessment for Dhulom, Saudi Arabia

The study presents the local values of wind shear coefficient (WSC) estimated using wind speed measurements made at 20, 30 and 40 m above ground level (AGL) during November 01, 1998 and October 12, 2002. The study also includes the local values of air density calculated using temperature and pressure measurement made at 2 m AGL during the same period. The mean wind speed above 4 m/s and the standard deviation values were used to obtain the turbulence intensities (TI) at different heights. These local values of WSC were used to estimate the wind speed at hub-height of the wind turbines used in this study. Energy yield was calculated for a hypothetical wind form of 60 MW installed capacity assumed to be consisting of 100, 60 and 30 wind turbines of 600, 1000 and 2000 kW from DeWind, respectively. The study recommends a value of WSC of 0.255 for the estimation of wind at different heights AGL and local air density of 1.06 kg/m3 The WSC values were found to be higher during nighttime and smaller during daytime while no evident seasonal trend could be identified. In case of air density, no diurnal change was evident but a seasonal trend, with higher values in winter and lower in summer months, was evident. The annual energy yield obtained using wind speed at different hub-heights calculated with WSC = 0.255 was found to be 10-20% higher than the yield obtained with wind speeds calculated with WSC = 0.143 corresponding to hub-heights of 60 and 100m, respectively. Similarly, higher plant capacity factors (PCFs) were obtained for energy yield estimated using WSC = 0.255 compared to that with WSC = 0.143. Higher values of TI were obtained during day time and lower during nighttime. Furthermore, lower values were obtained during November to March and higher during rest of the year. Finally, a decreasing pattern was observed in the values of TIs with increasing height

Assessment of the dietary transfer of pesticides to dairy milk and its effect on human health

The transfer of organophosphate and pyrethroid pesticides in dairy cattle’s milk when fed on agroindustrial by-product diet was assessed in this study. The transfer and accumulation of such pesticide in cattle fat tissue and milk was also assessed and the adverse effect on cattle’s and human health was also studied. For that purpose, about 80 milk and 30 diet samples were collected from various dairy farms. All samples were extracted with acids using "quick, easy, cheap, effective, rugged, and safe" (QuEChERS) method and analyzed through gas chromatography-mass spectrometry (GC-MS). The results show that about 40 and 20% of milk samples had greater content of cypermethrin+chloropyrifos and porfenofos than their maximum residue limits as suggested by World Health Organisation (WHO). Cypermethrin, chloropyrifos and profenofos were present at concentration greater than their maximum residue limits in mixed diet whereas profenofos was completely absent in sugarcane khal and was present in traces in cotton khal but remained within the maximum residue limit. Nonetheless, transfer of residue of parent cypermethrin, chloropyrifos and profenofos to milk was not consistent with diet in all dairy milk samples. This revealed the contention that some other sources such as drinking or inhaling contaminated water or dust are also contributing to pesticide contamination in milk. Cancer potency factor for cypermethrine in children and adults remained within the recommended value. Generally, although pesticides residue in milk was not high enough to cause cancer risk in human, they might cause adverse health effect and delayed toxicity due to their long term accumulation and persistence within cattle’s body. Therefore, there was an urgent need to estimate their contents in dairy cattle milk in order to provide a baseline for the health ministry to make safety regulations.Keywords: Pesticides, contamination, milk, cattle diet, risk assessmentAfrican Journal of Biotechnology, Vol. 13(3), pp. 476-485, 15 January, 201