For much of the last two decades the key to getting better wind power efficiency was larger and larger turbines. Garrad Hassan writes of the trend in greater turbine size

Figure 3.10 Growth in size of commercial wind turbine designs, Source Garrad Hassan

Source: Garrad Hassan

The past exponential growth of turbine size was driven by a number of factors.  The early small sizes, around 20-60 kW, were very clearly not optimum for system economics.  Small wind turbines remain much more expensive per kW installed than large ones, especially if the prime function is to produce grid quality electricity.  This is partly because towers need to be higher in proportion to diameter to clear obstacles to wind flow and escape the worst conditions of turbulence and wind shear near the surface of the earth.  But it is primarily because controls, electrical connection to grid and maintenance are a much higher proportion of the capital value of the system.

A new technology called AeroLeaf from NewWind could turn this conventional thinking on its head. AeroLeaf is “A proprietary technology based on microelectricity and a multiplicity of turbines. Its ingenious approach consists of accumulating watts to make up kilowatts.” A number of small turbines are used to harvest even the slightest wind. This technology won’t be replacing massive power plants any time soon, but its distributed, local focus could certainly make any power grid more robust.