Flexible power generation from solid biofuels

Abstract

Flexible and demand-based production of electricity and heat (combined heat and power – CHP) from solid biomass is an extremely interesting concept for a renewable energy system as the used fuel shows excellent storability. However, conversion and power generation technology limit flexibility for several reasons.Combined heat and power plants for the production of solid biomass are today designed for base load operation. The most common systems are steam cycles, organic Rankine cycles (ORC) and combinations of gasification and gas engines. Other available technologies include Stirling engines, fuel cells and thermoelectric generators (TEGs). Some technologies are already able to provide flexibility in power production. Extracting turbines, for example, are able to change the power-to-heat ratio of the system. It is possible to increase flexibility by using additional or upgraded units such as heat or gas storages, new steam turbines or new control systems. Potential solutions for increasing flexibility in combined heat and power production from solid biomass are expected to include micro-CHP systems and gasification units with high flexibility and high power-to-heat ratio. Larger plants may show less flexibility due to their thermal inertness (which sometimes has been part of the design, e.g. to stabilize combustion of fuels with low heating values).