Apparent wind that measures wind speed in knots and wind direction in degrees relative to the heading of the boat. Modern instrumentation can calculate the true wind velocity when the apparent wind and boat speed and direction are input. In sailboat racing, and especially in speed sailing, apparent wind is a vital factor, when determining the points of sail a sailboat can effectively travel in. A vessel traveling at increasing speed relative to the "prevailing wind" will encounter the wind driving the sail at a decreasing angle and increasing velocity. Eventually, the increased drag and diminished degree of efficiency of a sail
Wind power in the United Kingdom and wind regimes, are smoothed, rather than intermittent. As the distance between sites increases, the correlation between wind speeds measured at those sites, decreases. The combined output of multiple wind turbines widely distributed across the UK gives a normal distribution of power, with a standard deviation which is about 0.76 of the average power. A Scottish government spokesman has said electricity generated by renewables accounted for 27% of Scotland's electricity use. On the night of 5–6 April 2011, the wind in Scotland was high, it was raining heavily, which also created more hydroelectricity than normal. The grid became overloaded preventing