Fossil fuels are currently used to generate the major part of process steam for industrial facilities. An established approach for the sustainable substitution of fossil resources is the supply from solid biomass-fuelled combined heat and power (CHP) plants. However, current designs of biomass CHP plants usually raise only a share of the total steam demand (fossil-fuelled boilers supplying the rest), due to limits in their design. A steam accumulator represents a promising device to increase the share of steam generated from biomass. Based on a simulation model developed for the specific application, this paper confirms the positive effect of a steam accumulator on the biomass coverage ratio (BCR). An increase from 82% up to 95% is demonstrated Furthermore, relevant design parameters such as the charging massflow and the operational pressure difference are identified as key design parameters for the steam accumulator.