Can green hydrogen and waste heat utilization improve energy conservation and emission reduction of coal-based cogeneration processes?

Power-to-gas offers a new path for carbon emission reduction by integrating renewable energy hydrogen with traditional chemical process. However, its application is limited by the product fluctuation and high cost of green hydrogen. To further improve the level of energy conservation and emission reduction, this research explored the novel integration process of large-scale green hydrogen system and coal-based cogeneration process. The green hydrogen with a low fluctuation was obtained from the wind-solar coupled power equipped with conservative energy storage system. The results showed that the carbon emission was significantly reduced by 9.2%, while the total operating cost was increased by 18.7%. To alleviate the high operating cost caused by green hydrogen, various waste heat utilization systems were introduced to decrease the utilities consumption. It was found that the total site waste heat utilization was capable of further reducing carbon emission by 13.3%, and the increase in total operating cost can be controlled within 15.3%. Economic analysis proved that the expensive cost could be saved by lower hydrogen usage or hydrogen cost. By incorporating waste heat utilization, the cost increase could be as low as 6.0% and 4.8% under 50% green hydrogen flowrate or 40% energy storage system. With the progress of renewable energy hydrogen production and waste heat utilization technology, the proposed inte-gration process will be more environmentally friendly and economically feasible in the future.