PURPOSE:To realize an effective utilization of magma energy by a method wherein a cylindrical structure having a large diameter is settled on the surface of a sand layer by the surface of a water bottom part (sea or lake) or the like and a heat exchanger is settled at the water bottom part within a scraped cylinder where hot water is discharged so as to collect heat. CONSTITUTION:A cylindrical structure 2 having a large diameter to be used in scraping a water bottom 1 (sea or lake) prevents decay of sand around it during a scraping of the water bottom part where hot water is discharged. After construction, the cylinder is extended up to the water surface so as to support the structure and to keep a temperature within the cylinder and increase an inner temperature of it with a heat shielding member 8, resulting in that an entire heat exchanger is effectively increased. This becomes a tank to prevent dispersion of a underground polluted substances within the cylinder, hot water is supplied to a root part after recovery of the polluted substances and then a development of the industry and elimination of decreasing population are promoted. That is, the cylindrical structure having a large diameter is settled at the hot water discharging location 27 at an old volcano port of the water bottom (sea or lake), a decay of the sand during the inner scraping operation is prevented and the structure is communicated with the upper part of the heat exchanger 4 (the same as S/G of an ultra large sized device) after inner scraping operation.
展开▼
