permaculture

[Douglas Woodard <dwoodard@becon.org>]

A fundamental problem with the Darrieus rotor is that the forces on a 
blade reverse with each rotation, thus this design is especially 
vulnerable to materials fatigue.

Reliable startup requires a special provision such as a powered start or 
an attached Savonius rotor.

Aerodynamic braking (essential for safety) is extremely difficult with a 
Darrieus rotor.

Weak winds contain little energy. Power in the wind varies as the cube 
of the windspeed. The Darrieus design is difficult to mount high where 
the wind is strong. It fundamentally requires more materials for the 
power yield than a horizontal-axis design. There is no point in mounting 
a wind turbine low; it is not economical. It still has to be strong 
enough to survive storms.  There is no point in a low-yield wind turbine 
which retains its fundamental problems of moving parts, rotation and 
vibration, and relatively high maintenance requirements. A photovoltaic 
system becomes preferable.

Darrieus wind turbines were tried on a fairly large scale in the early 
days of commercial wind turbines in California in the 1980s, but proved 
unable to compete economically with horizontal-axis deigns.

Doug Woodard
St. Catharines, Ontario, Canada



Lawrence F. London, Jr. wrote:

> I have always been interested in possibilities with the Darrieus rotor.
>
> "The wind energy system uses a Darrieus-type vertical axis wind turbine. It can operate normally even when the wind is 
> not very strong."
>
> Technology and materials available these days ought to b able to produce a 
> small high efficiency
> Darrieus turbine for home electric power generation. Thses systems do not 
> have to be on a high tower,
> can be light and mounted easilt alomst anywhere, i.e. safe and easy to 
> construct and install.