In the early years of the modern era of the wind turbine, experimental development of vertical axis wind turbines (VAWTs) was underpinned by an incremental improvement of aerodynamic performance prediction methods; the most advanced being the double actuator disk, multiple streamtube theory devised, quite independently, by David Sharpe in the UK and Ion Paraschivoiu in Canada. Commercially, VAWTs were not successful as the 3-bladed, pitch control horizontal axis turbine became the de facto configuration for the industry, and consequently progress in VAWT development stagnated. However, renewed interest in VAWTS has emerged, prompted by the development of small turbines for use in urban environments, e.g. the helical VAWT from quietrevolution. The objective of this paper will be to review recent third party findings and present the author’s own trade studies of the helical VAWT using the double actuator disk, multiple streamtube theory. Furthermore, initial investigations will be presented of a proprietary CFD software tool, which uses a mesh-less approach to fluid dynamics modelling that makes it an attractive option for dynamic/transient flows, moving bodies, and complex body surfaces. The author concludes that the challenges for predicting the aerodynamic performance remain the same but CFD offers substantial new insights into turbine behaviour