Combining biomass and hydrogen for reliable green energy
Despite offering cleaner energy, renewable energy sources such as wind and solar are intermittent in nature, and can’t yet offer a complete alternative to fossil fuels. Balancing the supply of electricity with demand requires energy storage and generators that can quickly come online – with generators run on natural gas typically filling this role. “Gas turbines play an important role in providing reliable electricity and heat, but as Europe moves towards cleaner energy sources, these turbines must adapt to new fuels such as renewable gases and hydrogen,” says Susanne Paulrud, coordinator of the Bio-FlexGen(opens in new window) project. To meet this need, Bio-FlexGen focused on advances to renewable combined heat and power (CHP) plants, which burn solid biomass to produce heat and electricity. The project developed core components for Biomass Top Cycle(opens in new window) (BTC) technology, a more advanced and efficient system where biomass is first heated under pressure to produce syngas – a mixture of hydrogen, carbon monoxide and other gases. This is burned to drive a gas turbine (the ‘top cycle’), and the hot exhaust is then used to drive a steam turbine (the bottom cycle). Operators can adjust the plant settings to maximise heat, electricity or hydrogen production, depending on their need. “Our solution balances both short- and long-term energy supply, responding to daily or seasonal changes in demand,” adds Paulrud, a senior researcher at the RISE Research Institutes of Sweden(opens in new window).
Novel approaches to green energy
Key to success of the project was Bio-FlexGen’s flexible gasifier design, complemented by a multi-fuel turbine combustor. A hybrid fluidised bed(opens in new window) (HFB) helped break down biomass particles and increase chemical reaction efficiency, reducing by-products such as tar. A specially designed gas turbine combustor safely and efficiently switches between burning syngas and hydrogen. Pilot-scale testing confirmed the HFB’s stable and reliable operation. "With conventional steam-cycle biomass CHPs focused mostly on heat generation, electricity output typically accounts for only 25-30 % of the power output per unit of biomass. Our design not only increases this to over 50 %, which lowers costs and emissions, but the plant can also flexibly respond to changing energy demands,” explains Paulrud. In winter, with heating demand high and wind/solar energy less available, the BTC plant can provide reliable power and heat from biomass. During off-peak summer periods, it turns surplus energy into hydrogen. Integrated gas turbines can also ramp up power quickly, offering a cleaner alternative to traditional fossil fuel backups.
Fit for real energy systems
Energy system modelling was conducted to ascertain the solution’s economic viability, with the BTC concept applied to two use cases: a Swedish district heating system and two Spanish industrial sites (chemical and cement). “In Sweden, while our technology would increase renewable electricity production and make the energy system more flexible, investment costs are a barrier under current market conditions. Whereas in Spain, the BTC improved profitability and reduced carbon dioxide emissions in every scenario. Industrial users with steady heat demand appear especially well suited to the technology,” notes Paulrud.
Decarbonisation and bioeconomy growth
Replacing fossil fuels with renewable biomass and hydrogen will help Europe meet its climate goals. “The technical benefits translate into cleaner air for citizens, and more stable, and potentially more affordable, heat and electricity, while also creating new green jobs, particularly in rural and industrial regions,” says Paulrud. The team is currently focused on moving the concepts closer to large-scale applications within the EU’s growing bioenergy market.
