DIFFERENT WIND

Vertical axis wind turbines: The only way is up?
Andrew Williams, March 27, 2012 (Wind Energy Update)

"…Interest in vertical axis wind turbines (VAWTs) is growing and several design concepts including DeepWind and VertiWind are undergoing development and testing. So, how do they compare with horizontal turbines - particularly in terms of performance, costs and ease of installation?

"…[O]ne advantage of VAWTs is that they have an 'omni-directional' operation and low centre of gravity - leading to good structural stability…[They could dispense] with struts, simplifying structural complexity compared with previous designs…[L]arge-scale VAWTs could be better at avoiding the 'gravity issues' that plague large horizontal-axis turbines (HAWTs), which can quickly exhaust blades…[O]ne of the disadvantages of VAWTs is that it can be difficult to access machinery, which is below the main turbine axis and often dug into the ground. However, in floating foundations, like their own WindFloat design, the hull can be hollowed to enable access…"

VertiWind's floating vertical wind turbine (artist's conception - click to enlarge)

"In terms of output capabilities, the general consensus is that VAWT efficiency is currently either the same or lower than HAWTs…[T]he VertiWind VAWT has been designed for a 2MW output, with a power curve comparable to HAWTs of the same rated power…[but] Walt Musial, Principal Engineer - National Wind Technology Center at NREL, argues that VAWT efficiency is maybe 20% less 'give or take a little' …[another expert argues] it is approximately 10% less…

"…CAPEX is 'probably higher' for VAWTs now but should 'be about equal in the long run.'…OPEX costs can go both ways - but are likely to be higher at present…because of a lack of experience…CAPEX and OPEX costs for VertiWind are comparable with a HAWT bottom-mounted solution in shallow waters - even though they operate in deeper waters…[G]rid-connection costs are 'related to distance to shore' and are therefore more difficult to compare like-for-like…[T]he VertiWind design lends itself very well to high-volume manufacturing…[and] transportation…VAWTs have a number of novel advantages…[but] a good deal of work remains…to convince the wider industry that they can compete…"