Performance - Wind Energy: Renewable Energy and the Environment - page 165

FIGURE 8.16 Atlantic Orient (50 kW) wind turbines at Kotzebue wind farm.
KEA will save money in reduced costs of storage and pollution control requirements associated
with diesel fuel.
In the year 2000, the ten wind turbines produced 1.1 MWh of electricity, which saved 265,000 L
of diesel fuel. The wind turbines were shut down during part of the summer due to construction on
the distribution system, so availability was only 85% during that period. KEA added two more AOC
turbines in the spring of 2002. Because of the cold-weather, high-density air, they had to change the
control system to reduced peak power output. A Northern Power wind turbine (100 kW), three more
50 kW units and one remanufactured V17, 65 kW, were installed, so by 2007 there was a total of
seventeen wind turbines at the site. In 2007 they generated 667,580 kWh of energy, which resulted
in a savings of 172,240 L of diesel fuel. Installing foundations in permafrost and operating in cold
climates present problems not found at lower latitudes. With the price for diesel fuel escalating to
$1.25/L in 2008, wind-diesel becomes more economical.
A number of prototype and demonstration hybrid systems (wind, PV) have been installed;
however, performance for most projects has been poor. In the past, hybrid systems [25] have had
a high failure rate, with failures due to faulty components, poor maintenance, and inadequate
support by systems suppliers after installation. Hybrid systems will be covered in more detail in
Chapter 10 .
8.9 BLADE PERFORMANCE
A smart rotor blade [26] would have active control of the aerodynamics with spanwise distributed
devices: trailing edge devices and camber control, micro tabs, boundary layer control (suction,
blowing, synthetic jets, vortex generators), and structural integration. Besides lift and drag data
for airfoils, including some data for changing attack angles, blade performance has been evaluated
through research and field experiments. These include effects of surface roughness, boundary layer
control, flow visualization, pressure taps, and vortex generators.
Data from pressure taps on a blade were used to obtain lift, drag, and pitching momentum coef-
ficients during normal operation and dynamic stall [27]. The blade was the new S809 thin airfoil,
constant chord, no twist, on a three-bladed, downwind rotor (10 m diameter), constant rpm, and
variable pitch. Dynamic stall occurred at 30° yaw angle and during high angles of attack.
8.9.1 S URFACE R OUGHNESS
Performance will be reduced by the airfoil sensitivity to blade roughness. Just as for wings on air-
planes, ice reduces performance drastically ( Figure 8.17 ), to the point where the rotor will not turn.
Also, falling chunks of ice from large blades present a safety hazard. If icing is a major problem,
then it might be economic to have heated blades. Black blades have been used on some wind tur-
bines to assist thawing when the sun comes out.