(2) Combination of combined-cycle engines with district air-conditioning system
Since it is the principle of the thermodynamics to change the heat to the power from the temperature as high as possible, the heat engine as the topping of the cogeneration should not be satisfied with the "lowtemperature type" heat engine like the boiler-steam turbine as described above, and only the "high-temperature type" heat engines like the internal combustion engines are also insufficient. It is desirable to improve the efficiency using the combined cycle heat engine in which the high-temperature type is combined with the low-temperature type.
In the Capital Berlin in the unified Germany, the redevelopment of the central part has been promoted, and the latest combined cycle power generation plant comprising two sets of ABB-GT13E2 type gas turbine of 140 MWe (suffix "e" means the electric output) and one set of back pressure steam turbine of 100 MWe, totaling 380 MWe in capacity was introduced in the area including the governmental office district close to Brandenburg Gate on the ex-East Germany side and the new buildings close to Potsdam Platz by abolishing the natural gas and petroleum combustion plants operated since 1963, and the Berlin-Mitte Plant to provide the district air-conditioning of 340 MWth (the suffix "th" means the thermal output) was completed in 1996. The Berlin Power Company (Bewag) to operate this Plant is a power company of the longest history in Germany which was established in 1884, and this company has supplied the heat primarily and the electric power secondarily to the whole area of Berlin having the population of 2.20 million. Berlin has 13 power stations controlled by the company, and 12 power stations thereof are cogeneration-oriented, and one power station has the plant only for the power generation. The total capacity of their whole facilities is 3,117 MWe in power generation, 6,558 MWth in heat, together with 452 MWth in heat supply from 8 plants exclusive for the heat supply, and this company is the largest in Europe as the heat supply company. The total piping length exceeds 1,000 km, and the total floor area of the buildings to which the heat is supplied exceeds 47 million m2, including the heat supply to general households totaling 505,000. Since the redeveloped commercial area invested by Benz and Sony is included in the heat supply area, the district cooling service not popular in Europe is also provided.
Regarding the district heat supply in Japan, the first case employing the combined cycle power generation was born in Hokkaido by Mycal Otaru Energy Supply on March 11, 1999. The plant comprises two sets of gas turbine of 6 MWe and one set of steam turbine of 4.7 MWe in a combined manner with each other, and its capacity is one half that of the above-described Berlin Plant. In the plan, the district air-conditioning service will be given to the composite commercial facilities of about 340,000 m2 in total floor area comprising 5 buildings including a supermarket, a hotel, a restaurant, a cinema, a hot-bathing facility, a play land, and an entertainment theme part, which is the largest in size in Japan. Dwellings including apartment houses will be constructed in future. The fuel is LPG, and this system was established under the duty of the power supply by a purely private company as the specified point of the electricity enterprise approved by the amendment of the Electric Utility Law in December, 1995. Their success will be expected.
