Wind potential and wind pump water discharge for drip irrigation; a case of lake victoria shore-Kenya

Abstract

Wind Pump drip irrigation is a system that is not documented but developed to link the theory of wind regime, Wind machine and drip irrigation to deliver low but frequent applications of water to plant roots for clean energy and to exploit advantages of drip efficiencies. This was by synchronizing wind speed, wind pump discharge, and evapo transpiration. At Lake Victoria Shore (5700 Krnz) Kenya, the challenge was lack of adequate wind speed data obtained only at Ahero, Kadenge, Kibos, Muhuru Bay, Rusinga tlm height) and Kisumu at 2m and 10m heights for the large area. Rusinga had 2m height data and a pre-installed wind pump while Ng’ura site lacked wind speed data but a wind pump was installed. The objective of this study was to detennine wind potential and estimate water discharge from variable wind speeds for use of a wind pump drip irrigation system at the Lake Shore. This comprised design and installation of the system at Ng’ura, collection of actual wind speed and discharge data from Rusinga Island. A survey map was used in positioning the pipeline, dug well, water tank and the sedimentation tank at Ng’ura. Field performance of the horizontal axis wind pump coupled to a drip-irrigation system was done at Rusinga Island. A total of 39 test runs was done in a period of 20 days. The actual data from Kisumu and Rusinga were respectively used for the development of percent wind speeds availability and to select the best of the existing instantaneous discharge equations. A fitting statistical distribution (Weibull) model for use with power law index (u) parameter for increase of the wind speeds with height was identified from the Lake Shore (LS) data. It was established that the wind speeds (Zm) within the Lake Shore were consistent, fitted the three parameter Weibull distribution and the predicted 10m Kisumu wind speeds from 2m compared well to the actual 10m with an average R2 of 0.83. The power law index (u) was 0.4 for the Lake Shore, 2 times the actual (0.8) for Kisumu, negatively related to power law index (ot) and location. The winds speeds at the Lake Shore showed greater potential nearest to the shoreline with less frequent change of direction. Height of placement of the wind turbine needed to be increased with reference to distance inland and shore line. A Weibull model parameter scale factor (c) for each station was determined and found useful for estimating wind speeds at l0m from 2m using a Weibull model and power law index (0.). Particularly, hourly wind speeds for one year for every month was adequate for estimating the wind speeds at a location. The wind speed range percent (WSRP) availability table and the conceptualized model (Q = K (Z V[Ri) discharge equation (which compared well to the existing instantaneous wind pump discharge equations) developed is for predicting wind pump discharge and wind strength time limits for irrigation duration. The accuracy of the predicted discharge improves with the length of the hourly wind speed, the startup pump rotation speed and the measuring equipment. Additionally, the wind speeds at 2m height at Ngu’ra were greater than 2m/sec and reasonable for installation of the wind pump. Installation required knowledge of locality/topographical map and Lake Victoria water levels which lost 0.5 m depth at Ngu‘ra, estimated to be over 40 m in horizontal distance for data of over 40 years. The Ng’ura reference evapotranspiration (ETo) averaged 4.1 mm based on the LocClime Estimator and compared well with that calculated for Kisumu, Kibos and Kadenge. The wind pump drip irrigation system development and installation approach for Ngu’ra therefore can be used elsewhere along the shore as a guide. It was also established that a..*§.=*ect coupled wind pump to a drip-irrigation system with pressure compensating emitters ‘as technically feasible due to the drip irrigation emission uniformity efficiencies achieved. They were acceptable within standards as they ranged between 93% in the morning to 94% in the afternoon for the 39 test-runs made. Wind regime, wind pump performance characteristics and of emitter discharge were noted as the critical parameters for the system design. The I-ind pump drip irrigation as an agricultural production frame work put forward in this study a basis for exploitation of wind as the green energy. However there is need to enhance data capture in form and format for precision in use of the method as a technology