Eirik Nordhagen

Senior Engineer

(+47) 917 31 807

Ås H8

Visiting address
Høgskoleveien 8, 1433 Ås


We studied drying of wood chips by surplus heat from two hydroelectric plants in the western part of Norway. The wood was chipped and loaded into the dryer; a tractor-trailer and a container were used. The dryers had perforated floors where warm air from the plants was funnelled into the dryer, using an electric fan of 4 kW. Four separate trials were conducted in September and October 2009. The drying capacity of the trailer and the container was roughly 11.5 m3 and 29 m3 loose respectively. The effective height at which drying took place was 1.2 m and 1.9 m. The average temperatures of the air channelled into the dryers was 15–18 °C in the trailer and 24–26 °C in the container. The fan was operated for 139 hours (twice) for the trailer and 121.5 and 67.5 hour periods for the container. The fan used 556 kWh (twice), 486 kWh and 270 kWh of electricity respectively. The chips located at the bottom dried first, and chips located above dried later. The water content in the chip was measured to 66.1 to 52.1% (wet base) before and 9.6 to 6.9% (wet base) after drying. The amount of water removed from the container was approximately 28 kg per hour and 22 kg per hour from the trailer. For the container, drying cost roughly 9 Euro per MWh; the cost of the trailer was nearly twice as much. This indicates that the drying volume should be as high as possible. Drying determines net calorific value and hence market value of wood chip.