***Dr Mohammed Muniruzzaman travels through geothermal research institutes in Japan***

***In conventional thermal power generation, the steam needed to rotate the turbine to generate electricity is obtained by the combustion of oil, gas, coal etc. In geothermal power generation the steam is directly obtained from the earth. The temperature gradient near the earth’s surface is about 30° C per km. Generally a depth of 30 to 50 km would produce a temperature of 1000° C and this can be regarded as a large thermal reservoir. Current technology however, is unable to utilise this heat because of the great depth.***

***Research in geothermal energy technology include exploration methods of fracturetype geothermal reservoir, measurement while drilling (MWD) in a geothermal well and using the technology for exploration of geothermal energy source, binary cycle plant and hot dry-rock power generation system. However, of particular interest to

Bangladesh would be results from survey of deep-seated geothermal reservoir for the promotion and exploitation of deep geothermal energy.***

DR Tohru Mogi of the De-partment of Mining Engineering Kyushu University. was waiting for us when we arrived to meet him. Although 9.30 In the morning Is not too early for an appointment, however, both Dr Tadashi Nakatsuka and I were a little apprehensive as we arrived at Fukuoka the night before — quite late and very exhausted. Our itinerary which was finalised before we left Tsukuba included visits to the Geothermal Power Plant at Hatchobaru. the Geothermal Research Institute at Beppu and other similar installations and Institutions. Dr Mogi a renowned expert In geothermal fields Introduced us to his work through a small presentation and then talked about the geothermal power Installation at Hatchobaru that we were about to visit. Hatchobaru located at Kakone-cho In the Oita Prefecture Is about 90km east of Fukuoka. There are three geothermal power stations in the area. Hatchobaru. Otake, and Takigami. However. Hatchobaru Is the largest of Lhe sixteen geothermal power plants in Japan and the surrounding Kuju area where the three power plants arc located is one of the most beautiful regions in Kyushu. Volcanoes in the area are renowned for their beauty and shape, as are the many well-known hot spas like Sujiya. Makinoto and Cho-jabaru for their therapeutic values. 1 sat down beside Dr Mogi who was driving the car with Nakatsuka-san and a researcher bringing up the rear. We drove from Fukuoka en route to the Yamanami Highway — which cuts through the Handa and Kuju Plateaus. I listened to Mogi-san informing me that Kyushu has historically been the conduit of influences from abroad in ancient limes mainly from China and Korea. Warsnips of the Mongols attempting to invade Kyushu in the 13th century were blown back by fierce winds that the Japanese called Kamikaze meaning divine winds. The self-imposed isolation of Japan from the 17th to 19th century’ was broken by letting foreign traders to Nagasaki that became the window to the outside world. Renowned for its beautiful coastline numerous natural hot spring and sand spa. Kyushu is also the location of Mount Aso and Mount Sakura-jima two of Japan's most active volcanoes. As we drove through the Handa Plateau — a raised platform of mostly extrusive igneous rock, the pristine beauty of the region was breathtaking. Dr Mogi an enthusiastic narrator of events and places, on the slightest inquiry poured out details that is both interesting and compelling. I came to learn later that he was a local lad and hence the intimate knowledge of the area. ATer auout an hour’s drive we left the flatlands and entered the winding roads of the mountains. What struck most in this region was not the planned and systematic afforestation of the hill and hillocks, but the gigantic scale on which these were being carried out. — miles after miles of hills covered with trees and plantations of all shapes, sizes and origin at various stages of growth. Dr Mogi again came to rescue and informed that this work has been going on for tens of years. Once the timber in a region natures it is felled and new saplings are planted in their place, keeping an eye of course to the natural bio-diver-sity of the region. I reflected on the relentless efforts, the perseverance. endeavours and commitments to excellence of such people that have transformed Japan into what it is today — an economic powerhouse. As a research student in UK. 1 had the opportunity to work as a member of the Anglo-Italian seismic research team in Sicily, Italy. 1 had on various occasions visited Mount Etna (northern Sicily) — the largest active volcano in Europe. Mount Stromboli. famous for its Strombolian eruptions and other erupting and non-erupting volcanoes In the Aeolian Island arc. In sharp contrast to the Japanese looking after nature to borrow a phrase from Mogi-san the Italians let nature look after Itself. Putting It in a different way. the Italians interfered very little with the natural growth of plants and trees. As we were some kilometers away frotn our destination Dr Mogi made a detour. drove into Oguni a small town and parked In front of a nice-looking restaurant. He Invited us to a lunch of local delicacy. Alter a leisurely and thoroughly enjoyable lunch (we had some time to kill prior to our appointment) we headed for Hatchobaru.

Geothermal Power Generation

In conventional thermal power generation, the steam needed to rotate the turbine to fgenerate electricity Is obtained >y the combustion of oil. gas, coal etc. In geothermal power generation the steam is directly obtained from the earth. The temperature gradient near the earth's surface is about 30° C per km. Generally a depth of 30 to 50 km would produce a temperature of 1000' C and this can be regarded as a large thermal reservoir. Current technology however, is unable to utilise this heat because of the great depth. It happens, however. In geothermal zones, volcanoes, natural fumaroles, spas, the molten rock or magma of about 1000° C is located at a depth of few km or less. Water infiltrating into the underground get heated by the magma, is trapped and forms the geothermal fluid reservoir. The utilization of the underground heat as a direct energy source is called geothermal power generation. The advantages of such power generation are obvious — effective use is made of indigenous energy source, no fuel is required and perhaps most importantly. clean and uninterrupted supply of energy is en-silred.

Italy holds the distinction of being the first country in the world to generate 0.75 horsepower utilizing the natural steam at Larderello in 1904. However, its upgradation to the world s first geothermal power station was completed in 1913 and the same year it went into commercial production generating 250 kw. Italy now ranks fourth amongst all the country producing electricity utilizing geothermal power. It currently produces close to 650 MW of power. Japan succeeded in drilling its first steam well in Beppu (1913) in the Oita Prefecture. However, it was not until 1925 that 1.25 kw of power was generated from the steam well — this was Japan’s first geothermal power plant. Over the years Japan has developed a large number of plants to meet Its growing energy needs. Because of favourable geological conditions half ol all geothermal plants are located in Kyushu. Japan with a total output of about 425 MW is the fifth largest geothermal power producer. Ambitious plans are however, under way to explore new fields, expand old ones, test new ideas of hot-dry rock generating system to attain a target of 3000 MW The USA although a late entrant into the geothermal pbwer production leads the world by producing a healthy 3000 MW. It went into production in 1960 by extracting steam from the geysers in California. Hatchobaru Geothermal Power Plant

In Hatchobaru district volcanic activities by the magma began about 200.000 years ago. The heat source has formed the present geothermal reservoir, water infiltrating deep into the underground is transformed into superheated steam at 230’ C to 280° C and form the geothermal fluid reservoir. The first of the two powerhouse at Hatchobaru was commissioned In 1977 and the second tn 1990.

The power station has a combined capacity of 110 MW and is the largest geothermal power station in Japan. Hatchobaru has developed a unique doubleflash system that utilises both high and low-pressure steam that drives turbine and generator. The mechanism in brief is steam and hot water from production wells Is led in a mixed form to a steam separator. The mixed fluid is separated here Into primary (high-pressure) steam and hot water and the hot water is then expanded under reduced pressure in a flasher to generate secondary (low-pressure) steam. The primary and secondary steams are both utilised to drive the tur-bine/generator. The hot water from the flasher is returned to deep underground through the re-injection well. Double-flash system increases the geothermal power by as much as 20 per cent and attains more effective heat utilization than the single flash system using only steam from the production well Most geothermal power stations are characterized by steam emanating from cooling tower in the Slants. The reason was not dff-cult to gather. Generally, a geothermal power station is located in a mountainous surrounding. This makes it difficult to gel a large volume of water for cooling the condenser — located besides the turbine. Hot waler after passing through the condenser is cooled down at the cooling tower and re-circulated.

As we moved from one section of the power complex to the next 1 mused on the paucity of personnel at the station. We inquired about it to the lady who was our guide and in charge of the complex then. She bowed profusely and regretted almost apologetically for having missed the point of informing us that Hatchobaru being a remote. inaccessible mountainous area is an unattended geothermal power station. All operations including the difficult ones of generator outputs, turbine revolutions ?tc. are supervised and controlled by a tele-control system by operators stationed in Otake about 2 km away. It was indeed our turn to be surprised and bow in admiration.

Future Outlook

The geothermal power does not require fuel and is a clean energy source not polluting the air. It is thus an environment friendly power source. Geothermal power currently occupies a small share in Japan's energy mix. Nonetheless. utilizing important indigenous energy resource and sharing a part of energy diversification programme, it greatly contributes to the nation's stable power source with-

out any anxiety of energy storage or supply. Research in geothermal energy technolog)’ include exploration methods of fracture-type geothermal reservoir. measurement while drilling (MWD) in a geothermal well and using the technology for exploration of geothermal energy source, binary cycle plant and hot dry-rock power generation system. However, of particular interest to Bangladesh would be results from survey of deep-seated geothermal reservoir for the promotion and exploitation of deep geothermal energy.

The author is Professor of Physics at the Jahangirnagar University.