1997 Volume 22 Issue 67 Pages 1-11
In the previous paper, the authors estimated the amount of energy which can be recovered as a heat source and heat sink of heat pumps from river water, sea water and treated sewage water in the Osaka city area. This result showed that the total amount of usable heat is abundant, however, the actual usable amount of heat would be restricted to only 0〜30% of the total since spatial discrepancy between heat sources and heat demand is large. In this paper, the transportation networks of these water is proposed as a measure for positive utilization. In the network, a DHC system is assumed in each mesh (250m square) and heat source water is supplied to the DHC plants from the heat source in order of the energy saving potential. The energy saving characteristics of the transportation networks is evaluated by numerical simulation. The actual amount of energy saved is calculated by considering the energy consumption for the transportation of heat source water. The results are summarized as follows: (1) The actual amount of heat is increased dramatically by the transportation networks. The networks can cover 40% of total heat demand in Osaka city area and the primary energy saving potential is estimated at 3581TJ/a. (2) By unifying pipeline for several DHC plants commonly, the energy saving potential is increased by 30%. (3) Spatial relationship between heat source and heat demand is also important in the case of using transport networks. By this reason, energy saving potential of sea water and treated sewage water in the Osaka city area is not improved well as river water. (4) Transportation networks also has a large heat island prevention effect. (5) The embodied CO_2 emission in pipelines and pumps is equal to 1.3 times of the amount of CO_2 emission decreased by energy saving during a year. (6) As the COP of heat pump is increased as shown in Fig.11, the energy saving potential is increased by 40%.
