3 research outputs found
Water use efficiency of six rangeland grasses under varied soil moisture content levels in the arid Tana River County, Kenya
This study evaluated water use efficiency (WUE) of six range grasses, namely; Chloris roxburghiana, Eragrostis superba, Enteropogon macrostachyus, Cenchrus ciliaris, Chloris gayana, and Sorghum sudanense grown at 80, 50, 30% field capacity (FC) soil moisture contents and rainfed treatment which represented water deficit conditions. The changes in soil moisture content were measured by Gypsum Block which aided in determining the irrigation schedules. The grasses demonstrated varied levels of WUE which was evaluated by amount of biomass productivity in relation to evapotranspired water during the growing period. The three soil moisture content treatments had higher water use efficiency than rainfed conditions. There was a declining trend in WUE with grass species maturity where S. sudanense had higher WUE at 8, 10 and 12th weeks (> 15 kg DM ha-1 mm-) in all the treatments followed by C. gayana and E. macrostachyus and were significantly (p<0.05) different from E. superba, C. ciliaris and C. roxburghiana which had WUE less than 10 among the six grass species. The 30% FC soil moisture content had higher WUE at all the phenological stages for S. sudanense, C. gayana and E. macrostachyus compared to 80, 50% FC and rainfed with all having WUE greater than 20 kg DM ha-1 mm-1. These three species are recommended for irrigated pasture establishment in semi-arid lands where water supply uncertainties exist, owing to their high water use efficiency under lower soil moisture levels.Key words: Water use efficiency (WUE), water stress tolerance, range grasses, pasture irrigation, water deficit, Kenya
Combining Sustainable Land Management Technologies to Combat Land Degradation and Improve Rural Livelihoods in Semi-arid Lands in Kenya
A Review on Recent Development of Cooling Technologies for Photovoltaic Modules
When converting solar energy to electricity, a big proportion of energy is not converted for electricity but for heating PV cells, resulting in increased cell temperature and reduced electrical efficiency. Many cooling technologies have been developed and used for PV modules to lower cell temperature and boost electric energy yield. However, little crucial review work was proposed to comment cooling technologies for PV modules. Therefore, this paper has provided a thorough review of the up-to-date development of existing cooling technologies for PV modules, and given appropriate comments, comparisons and discussions. According to the ways or principles of cooling, existing cooling technologies have been classified as fluid medium cooling (air cooling, water cooling and nanofluids cooling), optimizing structural configuration cooling and phase change materials cooling. Potential influential factors and sub-methods were collected from the review work, and their contributions and impact have been discussed to guide future studies. Although most cooling technologies reviewed in this paper are matured, there are still problems need to be solved, such as the choice of cooling fluid and its usability for specific regions, the fouling accumulation and cleaning of enhanced heat exchangers with complex structures, the balance between cooling cost and net efficiency of PV modules, the cooling of circulating water in tropical areas and the freezing of circulating water in cold areas. To be advocated, due to efficient heat transfer and spectral filter characters, nanofluids can promote the effective matching of solar energy at both spectral and spatial scales to achieve orderly energy utilization