Investigating the Viability of Variable Speed Pumping: a Case Study of Selected Companies in Kenya.

Abstract

Pumps are being used in almost all industries where moving of fluids from low to high level is required. Energy consumption accounts for up to 90% of the cost of operating a pump. This high consumption is due to some factors such as operating the motors at full speed while in some cases this is usually not required. Ideally, variable speed drives vary the speed with respect to load and this is supported by affinity laws. Since energy costs are on rise, there has been progressive research to investigate the cost benefits of variable speed pumping. Many companies especially water utilities are struggling to pay high energy bills. Hence, variable speed pumping can be one of the means to reduce these energy costs. The main objective of this research was to investigate the viability of variable speed pumping. To achieve this, specific objectives of determining cost benefit analysis, establishing the degree of uptake, and determining factors which promote, or hinder uptake of variable speed pumping were taken into consideration. The study adopted simulation of data in a software to determine the impact of change of speed on the energy consumption of the same rated motor. A comparison was done between the constant speed pump running with soft starter and the data compared to when variable speed pumping was applied. A field study was done at Somerset Westview Hotel to determine power consumption of variable speed pumps and pump test bed to determine equivalent power consumption of constant speed pump. Survey was also conducted targeting companies in the water sector to understand the degree of uptake of variable speed pumping as well as factors which promote of hinder the uptake of variable speed pumping. It has been deduced from this study that we could save up to 21% of energy cost by using variable speed systems. A payback period of up to 11 Months was able to be achieved. This is notwithstanding various other benefits of VSDs like improved process control as well as low maintenance costs. The study also established the degree of uptake of variable speed pumping as 32.5% which is quite low and established factors which promote or hinder uptake of variable speed pumping. Henceforth, several measures can be taken to up scale the uptake of VSDs in pumping. These include enforcement of energy audit, energy efficiency projects and public-private partnerships, digitalization and remote monitoring and capacity building by professional bodies.