Solution for the future smart energy system: A polygeneration plant based on reversible solid oxide cells and biomass gasification producing either electrofuel or power

The Danish energy system will continue to evolve in the years ahead as the goal is to be independent of fossil fuels by 2050. This introduces several challenges in dealing with intermittent energy sources, such as wind and solar. A novel biomass-based polygeneration system concept is proposed, which can offer certain solutions to these challenges.

The main concept is storing electricity by producing bio-SNG from syngas generated by biomass gasification and electrolytic hydrogen when electricity prices are low, and producing electricity when prices are high. The analytical framework is built on thermodynamic modeling, and techno-economic analysis is applied to determine the total revenues required and net present value, given a range of bio-SNG and electricity prices.

The marginal cost of operation is then used to estimate the average operation time in each production mode. The results demonstrate that both electricity (46%) and bio-SNG (69%) production efficiencies are high. If district heating is coproduced, the total efficiencies increase to 85% and 90%, respectively.

Furthermore, it was found that the annual operation time in each mode varies significantly depending on the future electricity price scenario and bio-SNG price. A system that can select the production or consumption of electricity depending on the market price enables constant operation all year round.

This results in a higher net present value for the system and may lead to a positive return on investment, given the appropriate market price of electricity and bio-SNG. However, the techno-economic analysis revealed that the district heating product may be important for the economic feasibility of the polygeneration plant.

This system may offer solutions in a smart energy system connecting electrofuel, heat, and power production, toward a 100% renewable system.