Abstract
There are thousands of rivers across the world where hydrokinetic turbines (HKTs) could be generating constant small but useful amounts of power for remote off-grid communities, but there are very few hydrokinetic turbines actually operating, and these are limited to expensive units in very large rivers. For a cost-effective hydrokinetic turbine (HKT), the power output per unit cost must be maximised. Besides the cost of materials and fabrication of the turbine itself, cost includes a mounting structure, transmission and battery or mains connection, transport to site, deployment and operation and maintenance. This paper discusses the factors that determine power output per unit cost - CP, A, V, and proposes a radically new low-cost design which is expected to make small turbines affordable to off-grid communities located on moderate sized rivers and provide a basis for developing more cost-effective large turbines for grid connection: a horizontal axis single helix HKT with a flexible blade. This concept offers several advantages over conventional HKTs: (i) it can sweep a much greater flow area in shallow water, (ii) there is no need for a large, expensive pontoon or barge, (iii) a single helical blade maximises Reynolds number while maintaining desirable low solidity and eliminating the torque ripple inherent in straight blade Darrieus turbines, (iv) its cost per unit output is low, making it far more cost-effective than conventional designs, and (v) it is light and easily transported and deployed.