Once-through heat transport and seasonal storage for city of Bellingham

A conceptual design of a once-through district heating system utilizing industrial waste heat has been developed for the city of Bellingham, Washington. Two once-through designs are evaluated. Case 1 is based on an assumption that 67 MWt can be obtained from an aluminum plant and supplementary heat sources and does not require a seasonal thermal storage facility. Case 2 is based on the extraction of 45 MWt from the aluminum plant and requires a seasonal thermal storage facility. These once-through systems have been compared with the closed district heating system design which uses a two-pipe heat transport arrangement that returns the used water to the aluminum plant. In 1980 dollars, once-through system case 1 would provide an economic advantage of about $10.7 million over the closed system. Case 2 would incur a disadvantage of about $9.1 million in comparison with the closed system, largely because of the high cost of seasonal thermal storage tanks.