Network Planning and Assessment System for Multi-Source Waste Heat Exchange Based on Urban Symbiosis: A Case of Tokyo Metropolitan Area

To achieve the long-term target of climate change mitigation, low-carbon sustainable urban development is of increasing importance. The emerging Urban Symbiosis, as an extension of Industrial Symbiosis, supports a systemic... [ view full abstract ]

To achieve the long-term target of climate change mitigation, low-carbon sustainable urban development is of increasing importance. The emerging Urban Symbiosis, as an extension of Industrial Symbiosis, supports a systemic method for energy saving and resource conservation through waste recycling and heat exchange between industrial sector and urban area. To maximize waste heat utilization, it requires to design a wide heat exchange network which connects to multi-sources and users for cascading heat use. Several pilot studies in Eco-Industrial Parks have proved its technical feasibility, but when extending such practice to Eco-City scope, geographic proximity would become crucial because of the decay of temperature and pressure of steam or hot water. Regional planning considering real geographic location of facilities is necessary for Urban Symbiosis, while technical assessment is also required to carry out policy implication on urban planning.

Choosing Tokyo Metropolitan Area as a case, this study develops an integrated planning and assessment model to evaluate the potential impacts of creating regional heat exchange network through Urban Symbiosis considering local planning characteristics. Thermal power plants, large industries, and incineration facilities are selected as waste heat sources, while recovered heat is proposed to supply to surrounding industries and district heating networks. Firstly, based on network analysis supported by Geographic Information System (GIS), distance along road network between each source and user is estimated and recorded into Origin-Destination Matrix. Then, according to hydraulic calculation on temperature and pressure decay, possible cost-benefit and environmental impact is evaluated where only physically feasible and economically beneficial routes are selected. Finally, a market mechanism under complete information is proposed for matching heat supply with demand, where agreement will be made only if both supply and demand side are the first choice to realize the shortest pay-back period.

Tentative result reveals that annually steam supply from thermal power plants to industries could reach 70000 TJ, followed by 28500 TJ steam supply from incinerators to industries and 4600 TJ hot water supply from incinerators to district heating networks. However, it requires a large investment of infrastructure system corresponding to the target of CO₂ emission reduction. The result also identifies a conflict between cost-efficiency and implementation difficulty, as well as the main barriers for popularization caused by geographic separation in land use planning. Learning from several scenarios, this study provides several policy implications to help in decision making for integrated land use and energy planning joint with waste management for promoting urban symbiosis.