ABSTRACT
The deployment of remote monitoring systems based on Internet of Things (IoT) presents an opportunity to curtail operational and maintenance (O&M) costs associated with stand-alone PV systems. This study evaluates the characteristics of the commonly employed IoT platforms, their capabilities and associated O&M cost savings. Analysis of avoided field visit costs based on three remotely monitored solar PV sites is conducted through clustering of system faults and filtering out major ones that would warrant actual site visits. The obtained results are verified with information gathered from four other PV installer companies based in Nairobi, Kenya. Results obtained from the study show that majority of system faults can be monitored and often corrected remotely. Annual site-specific cost savings associated with IoT platforms range from $2040 to $3096. In comparison to ordinarily locally monitored systems, annual operation and maintenance costs can be reduced by 47-95%. This implies that it is now possible to adequately maintain healthy solar PV systems located in remote locations ensuring their longevity and convenience.
ABSTRACT
Water quality assessment was conducted on the Ruiru River, a tributary of an important tropical river system in Kenya, to determine baseline river conditions for studies on the aquatic fate of N-methyl carbamate (NMC) pesticides. Measurements were taken at the end of the long rainy season in early June 2013. Concentrations of copper (0.21-1.51 ppm), nitrates (2.28-4.89 ppm) and phosphates (0.01-0.50 ppm) were detected at higher values than in uncontaminated waters, and attributed to surface runoff from agricultural activity in the surrounding area. Concentrations of dissolved oxygen (8-10 ppm), ammonia (0.02-0.22 ppm) and phenols (0.19-0.83 ppm) were found to lie within normal ranges. The Ruiru River was found to be slightly basic (pH 7.08-7.70) with a temperature of 17.8-21.2°C. The half-life values for hydrolysis of three NMC pesticides (carbofuran, carbaryl and propoxur) used in the area were measured under laboratory conditions, revealing that rates of decay were influenced by the electronic nature of the NMCs. The hydrolysis half-lives at pH 9 and 18°C decreased in the order carbofuran (57.8 h) > propoxur (38.5 h) > carbaryl (19.3 h). In general, a decrease in the electron density of the NMC aromatic ring increases the acidity of the N-bound proton removed in the rate-limiting step of the hydrolysis mechanism. Our results are consistent with this prediction, and the most electron-poor NMC (carbaryl) hydrolyzed fastest, while the most electron-rich NMC (carbofuran) hydrolyzed slowest. Results from this study should provide baseline data for future studies on NMC pesticide chemical fate in the Ruiru River and similar tropical water systems.
