SHAM—a simulation model for designing straw fuel delivery systems. Part 1: model description

Straw is a renewable biomass that has a large potential as an energy resource in Sweden. The costs for harvest, transport and storage of this bulky fuel are, however, high, because it is produced over large areas and must be collected during a limited amount of days into intermediate storages before being ultimately transported to heating plants. This paper presents a dynamic simulation model for analysis of various delivery alternatives in order to improve and optimize system performance and to reduce the costs and energy needed in straw handling. The model, called SHAM (Straw HAndling Model), is based on submodels associated with infrastructural and geographical aspects, as well as with field drying and weather conditions. A simplified empirical field drying model has been developed, which is used to predict the straw moisture content at any time. The harvesting seasons can be simulated to compare different machinery chains, management strategies and plant locations. A large number of system performance measures can be studied, for example, utilization times of machinery, the time the straw has to wait for different resources, and the amount of straw that the machines are able to harvest per season. The validity of SHAM has been established by comparisons with existing harvesting systems.