The current prevailing idea of tidal energy conversion is that it is presumed uneconomical to extract power from tidal flows of less than 2m/s. As a result, there are a limited number of locations where energy from tidal flows can be exploited worldwide. Increasing the operating range of tidal energy devices to enable the extraction of useful power from low-velocity tidal flows would make tidal energy conversion possible in many more places around the world and greatly increase the potential global generating capacity. This paper presents a novel approach in extracting power from low tidal flows using vertical arrays of reduced diameter turbines. This has the effect of reducing the cut-in speed, increasing the operating range of the tidal energy device as well as the advantage of a lower cost, modular design, which addresses the issue of economical extraction at low flow rates. An assessment of the tidal energy resource around Hong Kong has been conducted for the preliminary stages of an ongoing tidal energy research project. The gathered data have been used to demonstrate the effectiveness of the presented concept in the Hong Kong region and other areas of low-velocity tidal flows. It has been demonstrated that a power increase of 40% is attainable from a vertical array of reduced diameter turbines when compared to a single, large-diameter device with the same frontal area. With the additional advantages of reduced cost of fabrication, installation, and maintenance from using smaller-diameter, modular tidal turbines, the concept is highly important to the advancement of global tidal power generation. Copyright (c) 2015 John Wiley & Sons, Ltd.