Lightweight, affordable, low power solar groundwater piston pump for rural remote regions.

Azeem Uddin, Azeem Islam

Abstract

Solar photovoltaic powered groundwater pumping systems (SPWPS) are popular way of fetching water from boreholes in semi-arid areas in rural remote regions of most developing countries, where commercial water and electricity supply is out of reach. As the climate changes and the water table drops in such marginal regions, borehole depth is ever increasing into hundreds of metres below the ground surface. In a SPWPS, the required energy to fulfil water demand at a certain head is termed as the required hydraulic energy which is maintained by the pump unit of SPWPS. However, this acts ultimately as a load on the PV generator. The pump unit typically requires more power in order to maintain this hydraulic energy. For high head systems, groundwater piston pumps perform better than centrifugal pumps. A detailed literature review established that the current piston pumps have design limitations that act as load on the pump driver, which uses extra external and internal mechanical components. These include long piston drive rods, connecting rod, meshing gears, crossheads and crossways. This study put forth a new concept design of a groundwater piston pump optimised for power consumption using a scotch-yoke mechanism that excludes unnecessary components in the pump in order to conserve power usage. A mathematical model was built to support the claim of low power consumption by the new pump design. The widely-used computer aided design and finite element analysis (CAD/FEA) technique was used to ensure the structural viability of the concept design for high head application, which is based on material selection process. The study also compares the concept pump power consumption among existing photovoltaic (PV) operated pumps including piston rod and non-piston rod pumps. The developed mathematical model for power consumption finds significant power savings when compared with benchmarked low-power long-piston rod pumps. For example, with a 200 m head and 10.2 lpm flow demand, the proposed pump uses up to 22.4% and 7% less power than a pump that uses either a steel or glass fibre reinforced composite (GFRC - e.g. polyester) rod, respectively. Hydraulic efficiency calculations show an increase of up to 76.7% compared to 59.5% and 71.4% using steel and GFRC piston rods, respectively. Additionally, significant energy savings of 1505.7 Wh/day and 383.7 Wh/day are also found for daily pump operation compared to commercial steel and GFRC piston rods pumps, which consequently reduces the associated costs of PV panels. Design safety factors of the conceived pump for high head loads such as 200 m are evaluated using structural FEA. Material selection process based on performance indices is also carried out using the Cambridge Engineering Selector (CES Selector) program. The design of the proposed pump components was also optimised for mass, based on the fatigue life constraint of selected materials using a FE parametric approach coupled with material variation. The optimisation model developed in this study reduces the mass with optimum fatigue safety factors contrary to yield strength criteria, incorporating performance factors such as material cost and energy consumption. Stainless steel 'BioDur 108' was found overall to be the best contender, with optimised dimensions saving up to 29.39% of mass and material cost, along with 29.25% reduction in power consumption. In conclusion, the developed design for a groundwater piston pump in this study is optimised for low power consumption, along with structural suitability for SPWPS with high head requirements in rural remote areas. The pump design's structural adequacy is checked by FEA, material selection and design optimisation. The pump is also suitable for other locations depending on its structural ability to withstand loads with suitable materials.

Citation

AZEEM UDDIN, A.I. 2020. Lightweight, affordable, low power solar groundwater piston pump for rural remote regions. Robert Gordon University, PhD thesis. Hosted on OpenAIR [online]. Available from: https://doi.org/10.48526/rgu-wt-1254576

• Thesis Type: Thesis
• Deposit Date: Mar 8, 2021
• DOI: https://doi.org/10.48526/rgu-wt-1254576
• Keywords: Groundwater supply; Groundwater pumps; Pump design; Photovoltaic energy applications; Finite element analysis (FEA)
• Public URL: https://rgu-repository.worktribe.com/output/1254576
• Award Date: Jul 31, 2020