Water flowing down to the sea level is of no use any longer. "There is no use over spilt milk." As illustrated in Fig.1, the "temperature difference" in the heat corresponds to the "head" in water, and the "ambient temperature" of the earth corresponds to the "sea level". The "use of the heat" means the head from the high temperature of 1500℃ or higher generated by igniting the fuel to the ambient temperature, i.e., 15℃. The heat dropped to the ambient temperature is no longer of any use. However, mysterious enough, the heat has little used successively from higher temperature like the hydroelectric power generation. Speaking of the "non-used energy", the waste heat from the subway readily becomes a topic of conversation, but the non-used energy in Japan is at most the "heat at higher-temperature region" from 1500℃ to 500℃.
When the fuel is ignited, we must think how to take out the power by operating the heat engines as pointed out by the genius Carnot. It has been a general idea of introducing a boiler when the heat or steam is requested. From now on, we must think of the introduction of the engine or the gas turbine if the heat is required. It is the first step of the reasonable use of the "heat" to change the higher-temperature heat by the heat engines, to drop the temperature, and to use the heat discharged from the heat engines for making hot water for the bath tub or space heating.
This "series" type system in which the higher-temperature heat is used for the engines to generate electric power and the exhansted lower-temperature heating is used for the heat, is referred to as the "cogeneration". In the conventional "parallel" type energy supply structure in Japan that the electricity is produced by the electric companies, and the heat is produced by the Gas and or oil companies in an independent manner from each other, the efficiency of the energy utilization as the whole nation becomes worse and worse. In order to drastically renovate this system, this system must be modified into the "series" system in which the higher-temperature heat is used for the power and further for the electric power generation by the heat engines, and the heat discharged from the heat engines is used for the process steam for industrial use and the air conditioning and the hot water supply for household use. Otherwise, the energy saving will be structurally impractical.
In such a sense, the cases of the "system energy" technology are described below, in which the highly efficient system is obtained only by combining the "established existing basic technologies" with each other to realize the energy saving.
Fig.1 Head and differential temperature
4. Examples of "System Energy" Technology
(1) Cogeneration
The certainty of the "system energy" technology is the cogeneration. The cogeneration has been long used also in the industry in Japan, in which the power is generated through the combination of the boiler with the steam turbine, and a part of the steam is extracted and used in the process in the plants. The capacity of the power generation facilities by the cogeneration is totaled up to about 20 million kW, which is about 10% of the capacity of the total power generation facilities in Japan; however, in such systems, the steam temperature is at most 500℃, demonstrating the so-called classical cogeneration. In order to take out the power immediately after the fuel is ignited, the cogeneration using the internal combustion engines such as the piston engines and the gas turbines must be diffused. Such a problem cogeneration is 1,854 in number, and 983,000 kW for household use, and 1,208 in number and 3.99 million kW for industrial use as of the end of March, 2000, and their capacity has been increased by about 400,000 kW annually.
At the First Conference of the Parties of the United Nations Framework Convention on Climate Change (COP1) held in Berlin in March, 1995, many advanced countries answered that the emission of CO2 in 2000 would be increased, while six advanced countries answered that the emission would be reduced. Denmark was the first whose answer was (-) 7.9%, and the answer of the Netherlands was (-) 3.7%. In the examination of the specific countermeasures of these two countries according to the report by the country, they promised that the reduction of the emission of CO2 would be realized by further increasing the diffusion of the cogeneration which was in the top level in the whole Europe, i.e., over 30% of the total power generation as illustrated in Fig.2.
