Changing the Future of Tokyo

Yuppy: Local energy generation and consumption of energy… You mean I can generate energy to move in my house? That's exciting!

Chamiko: It sounds interesting to charge Yuppy by recyclable energy! Here, Tokyo, can't we generate energy ourselves?

Yuppy: Yes! Oops, you know, the energy self-supporting rate of Tokyo is 0.49% (2014), the last place in 47 prefectures, isn't it? We have taken it for granted that we can get stable energy, but actually Japan have depended on other countries and areas for most of the energy.

Chamiko: We have to prevent serious situations such as environmental destruction in our daily life, and it's too late to know the current situation after serious accidents happen. The population of Tokyo is about 13 million. It's one of the largest cities. Are there any ideas that we can realize "Local production for local consumption of energy" in Tokyo?

Yuppy: The object of Japanese government is to make energy self-supporting rate to 25% until 2030… The goal is very difficult for Tokyo to reach.

Chamiko: Don't be depressed, Yuppy. What had we studied?

Yuppy: What we had studied…? Oh, making use of areas' characteristics…!

Chamiko: There must be some characteristics in Tokyo. Let's think of it!

1.Using Sunlight

・Power Generation by Solar Battery

Yuppy: I found the first one! There are a lot of buildings in Tokyo!

Chamiko: Some roofs of buildings or schools aren't open, but can't we use them more?

Yuppy: It is said that solar power generation is the easiest recyclable energy to introduce. In Tokyo, there are efforts to fix solar batteries on the roofs of seaside parks and reservoirs' parking areas. But solar battery has some problems.

Chamiko: Oh, really!? Well… I got it! It depends on the weather. We can't use it at night, or on cloudy days.

Yuppy: Right! Besides, the amount of power generation is not so much. But it is very effective as an alternative power. For example, it is often set in hospitals as the emergency generator for disasters! And what is more, the conversion efficiency of solar battery is only 10 to 15%, even if it is actually used.

Chamiko: A large part would be a waste… Why don't we use sunlight?

・Power Generation by Solar Heat

Yuppy: Let's see, there are ways which don't depend on solar battery.For example, light condensing: to collect sunlight with reflex mirror, boil steam and change into electricity. And, solar chimney: to build high chimney and generate electricity by gap of temperature between the ground and the highest place…

Chamiko: There are many other ideas of making use of solar power! But it needs wide spaces to set the facilities… The roofs of buildings will not be enough to set them... It does not seem to be suitable in Tokyo.

・Using as It is

Chamiko: Oh, collected sunlight is converted into electricity and we use it as light, right?

　　 　　Don't you think it waste: sunlight→electricity→light?

Yuppy: That's true! Sunlight comes from windows; it is efficient to use it rather than to turn the light. Blip… If we cut lighting time of 100W by 6 hours every day, electric bill will be lower by more than 5000 yen a year. We can also cut carbon dioxide emissions.

Chamiko: The skylights will play an active part! In high-rise apartment buildings, it will be comfortable for the residents if they have big windows on the south side. It's the time to use heating and cooling system will be cut as New Zealand does, isn't it?

Yuppy: There are some ideas: the solar water heater, which makes hot water by solar heat, and skylight tube, which change sunlight into light. Now they play active parts in China and Germany. It is wasteful to change all of the energy to electricity. Let's search for wiser ways to use energy!

2.Using Waste; Biomass

・From Leftover

Chamiko: Tokyo has a large population, so the people there are likely to produce more waste. Especially leftover is wasteful, so I want to reduce.

Yuppy: Why do you guys need to eat unlike me?

Chamiko: We can't do so. Yuppy, the present situation of disposal of leftover is…?

Yuppy: Blip…About 56% becomes waste. Recycle rate is about 39%.（『自然エネルギーの可能性と限界』、2010年） Food loss rate is highest in the food retail industry, and it is difficult to use a large amount of money to large-scale recycle.

Chamiko: The food retail industry refers to small stores where we usually get food, such as supermarkets? Waste is a lot... Can't we use it more as biomass instead of oil or coal?

Yuppy: We often hear the idea of making compost, right?

Chamiko: Cooked food contains salt, so it would be difficult to make compost.

Yuppy: Oh! What do you think about making ethanol from food waste and mixing with gasoline to make cars' fuel?

Chamiko: There seems not to be any problem to make ethanol, and using small power plants will help the food retail industry to recycle!

・from Sewage Disposal to Biomass Energy

Chamiko: Come to think of it, I have visited a sewage plant in Tokyo before.

Yuppy: Sewage plant is a facility which clean wastewater of sewerage and discharge it to river or sea…, right?

Chamiko: Yeah. I heard that the sludge which produced in the course is discarded there. The population of Tokyo is large, so it may be a large quantity.

Yuppy: Ok, you mean that we can use it as energy source? Let me see, Blip… I found it! The energy which produced in the course of sewage disposal is used at the sewage plant in Morigasaki, Tokyo. The electricity there is covered by biomass power generation from methane gas which is produced in the course of sewage disposal. Excess heat of power generation is also used.

Chamiko: Renewable energy is going to cover the electricity there! I found that there are a lot of efforts in many places. I want to spread such ideas.

Summary

Yuppy: It seems difficult to generate electricity in large scale, while it may be true that Tokyo is good at small-scale generation! In addition, it will raise public awareness of energy!

Chamiko: There must be some characteristics in Tokyo, as I said!

Yuppy: You brag! But… Yes, you are right. I somehow gain confidence!

Chamiko: Then, it is also important to save energy demand itself. We all have to make the most of natural resources. It is a good way to be supported by other areas of our country, but we have to find our own way to contribute to the solution!

Yuppy: We should generate and consume energy in each area, making use of areas' characters and each effort. If such places increase, the earth will be a clean one without any energy problems.