Think about the Excess Heat from Thermal Power

If you think about where the most energy in Japan is consumed, the first thing that comes to mind is power plants. To be accurate, we say 'consume', but more than what is consumed, the processing of the energy actually used is the real problem. The combination of thermal, hydraulic and nuclear power plants in Japan plus private power generation for a year amounts to approximately 1 trillion kwh of electricity.

<From this fact, it could be assumed that, if this energy were distributed evenly among the entire Japanese population, each person would be given 9.4 eu per day. Surprisingly, this is about as much as the energy from food for ten people.>

Electricity is good for a variety of uses including lights, machine power, and communication devices; plus, when you do use electricity, no exhaust gases or soot results. This is an incredibly convenient source of energy. In contrast to how convenient it is for the user, however, at the power plant itself, depending on the means by which the energy is produced:

• the burning of coal and oil (thermal power),
• nuclear reactions (thermal power through nuclear fission),
• and the fall of water (potential energy) to power turbine engines
  (electricity through motion);

In a thermal power plant, oil (fossil fuel) is burned and of the heat generated, some certain percent is converted into usable electricity. This percentage is referred to as 'heat efficiency' or 'thermal efficiency'. The present average is 39%. From 1951, when the newly established thermal power plants were generating 16%, the percentage continued to improve, and reached the present average as early as the 1970s when it made it to about 40%. It's been said that we have almost reached our technical limits since then, but in recent years, thanks to the combined cycle (raising the 'total heat efficiency' by integrating natural gas and steam powered turbines), and the introduction of other new technologies, it looks like Tokyo Electric Power Co., Inc. plans to raise its levels to 49% by the end of this year.

Well, you may ask yourself: 'If only 39% is actually used, where does the other 61% go?' This excess heat is expelled in the form of water vapors and steam.

<In other words, when a household uses a dryer that uses 1000 watts, since electricity can't be collected and saved, in some thermal power plant somewhere, 2500 watts of heat or more are being generated to run that dryer, and 1500 watts of excess heat results.>

600 billion of the 1 trillion kwh of energy generated in Japan in a year is thermal, and of 940 billion kwh, 400 billion eu of energy is expelled into the environment.

<This is the same as the amount of food necessary to feed the entire Japanese population of 120 million people for nine years.>
<In thermal power alone, 9 eu of heat is wasted per day per person.>

The fact of the matter is, however you look at it, excess heat is a waste. If we can't use excess heat to produce electricity, we need to learn to use it for other purposes such as heating and hot water supply. The technology necessary to make use of excess heat without waste is called cogeneration. Gases and oils are burned, the turbines are set into motion, and electricity is generated with producing excess heat. From that excess heat, steam and water vapors are created, and such things as air conditioning and hot water supply are made available to you. If electricity and the supply of heat are joined, 75-80% heat efficiency will be attained. We are simply incapable of introducing cogeneration because a power plant must be in close proximity to a heat consumption area. But regional air conditioning, large hospitals, and factories are now beginning to introduce cogeneration.

Using electricity, steam, and water ranging in temperature from lukewarm to extremely hot as descending stages in a stair-step like manner ('cascade use') to reach the goal of using each energy appropriately is all related to improved efficiency. From now, the energy we use in the environmental era, as opposed to the large-scale, intensified models to the small-scale, scattered, local models that have been used up to now, will help us to continue down the technical path to reach our expectations in cogeneration technology.

What we're trying to say is: the use of electricity may be convenient, but since it is a somewhat luxurious energy source, we want to be sure and use it carefully. If we can manage to lower the electricity consumption of such things as air conditioning, this is really the most efficient way to use energy.

• Thermal Power Technique: Publications of Tokyo Electric Power Co., Inc., the Federation of Electric Power Companies and others. According to the newspaper, LNG thermal power plant to be constructed in Kawasaki city will raise its heat efficiency level to 53%.
• Thermal power output: mainly figures from 1995 provided by the Energy Conservation Center.
• Cogeneration: "Cogeneration Technology Fundamentals" by Uichi Inoue and Shuichi Takada, published by Ohm Press, as well as publications of New Energy Foundation, Oil Industry Promotion Center and others.
• (Annotation)'in some thermal power plant somewhere...' there is certainly a percentage of electricity lost in sending it to the consumer, so the amount of electricity actually necessary is much higher.
• 'In thermal power alone, 9 eu ...' also, nuclear power gives off excess heat in the same way. Assuming that this produces about 300 billion kwh in a year, at a 35% heat efficiency ratio, the excess heat is equal to 560 billion kwh or 239.5 billion eu; one person expels 5 eu in water vapor per day. If you add this to thermal power, it's 14 eu.