AN ANALYSIS OF LIDAR MEASUREMENTS OF BUOYANT PLUME RISE AND DISPERSION AT 5 POWER-STATIONS

Measurements of wind speed, plume rise and dispersion have recently been made with a rapid-scanning, high-resolution Lidar (RASCAL) at four power stations: Fawley, Didcot, Drax and Littlebrook. This has allowed a more accurate determination of the Briggs plume rise coefficient than was previously possible and has also provided accurate coefficients for the rates of lateral and vertical spread arising from the buoyant plume rise. There appears to be a modest, but statistically significant, difference in the plume rise from power stations with and without cooling towers: for direct-cooled coastal stations we find C1 = 1.35, while for indirect-cooled inland stations C1 = 1.64. The former value is consistent with previous Measurements at Northfleet. The Drax measurements consisted of 76 plume trajectories each sampled every 8 s over about 30 min; this is a very substantial archive of plume behaviour and has permitted partial testing of the classical 2/3 power law equation for plume rise. Linear regression of the logarithm of plume rise against travel time verified the inverse relation between plume rise and wind speed to within a few per cent.