Hybrid industrial utility systems with biomass and electrode boilers: a techno-economic investigation

Hybrid renewable energy systems (HYRES) are an established pathway for electricity system decarbonisation and have similarly emerged as a solution for industrial process heat utility systems. This work has analysed the potential economic benefits of implementing a HYRES with a biomass and electrode boiler (HYRES-BE) into an existing processing plant in New Zealand by modelling a biomass and electrode boiler operating simultaneously and then extends these results outwards to account for sensitivities in fuel prices. In the model, the duty of the boilers changes as a response to pricing signals received from the electricity market and further optimised to minimise infrastructure costs. After optimising for a single configuration, the optimisation is expanded to all possible boiler configurations to observe how the local optima change. For the specific case study, implementing a HYRES-BE reduced the annual operating cost when compared to single-fuel alternatives. The potential savings from operating a HYRES-BE are highly dependent on the different fuel prices, with higher fuel prices leading to more favourability towards installing a HYRES-BE. Additionally, the coincidence factor between the electricity spot price and the process demand has a large effect on the economics of the HYRES-BE, with the lowest annual cost occurring at the lowest coincidence factor. The results indicate that the perspective of decarbonisation should shift away from single-fuel systems to HYRES-BE for both economical and practical reasons, with the most benefit (for the sensitivities in this research) occurring when the biomass boiler is between 75 % and 85 % of the maximum demand, and the electrode boiler makes up the remainder of the demand.