Monday, January 17

R & D Strategy Launch Out-86th “Society that changes with mass introduction of renewable energy”

Mr. Nobuaki Onagi Mr. Nobuaki Onagi

It has been a year and a few months since I moved from a private company to the Research and Development Strategy Center (CRDS) of the Japan Science and Technology Agency. The biggest difference from my previous job, which has been researching and developing, is that the research content and the technology to be developed can now be seen in three dimensions. Here, it is common to hear from multiple experts on a subject. I myself am not currently engaged in research activities, but I think that by coming into contact with various perspectives, I have become able to see research and development more deeply and broadly.

The job of CRDS is to investigate and think about how the world is moving and what to do if it is, and to propose “what should be done concretely”. For example, new compound semiconductor materials look promising for power conversion, so let’s strengthen this area. To do that, you need to look far into things. It is very useful for that to be able to see things three-dimensionally.

Since I was a corporate engineer, I was blessed with the way of thinking and the network of people on the corporate side. And now, with CRDS, I can get in touch with the network with the people of the university. I feel that both of these are becoming more integrated within me.

One of the areas I am in charge of is the environment and energy. In particular, I have been investigating what will happen to this electric power and what to do with materials and devices for that purpose for the past year or so. I will write some of the things that I felt were important.

The spread of renewable energy will change the flow of electricity

Renewable energy-related growth is remarkable in the amount of investment in newly introduced electric power facilities in the world (* 1). It is predicted that the power generation cost of renewable energy will be significantly reduced, and it will be possible to compete with existing thermal power generation and nuclear power generation in terms of cost (* 2). As a result, what happens when a large amount of renewable energy is introduced? One of them is the flow of electricity based on economic principles (* 3).

Normally, electricity only flows in one direction from the power plant to the user. However, when a large amount of renewable energy is introduced, this flow of electricity changes. Economic principles are brought in, and electricity flows through the routes determined by them.

Since wind power and solar power fluctuate over time, the amount of power generated by this also fluctuates greatly. On the other hand, electricity from thermal power plants is extremely stable. From the user’s point of view, it is a problem if the electric power fluctuates. Therefore, electricity that does not fluctuate has high value. Since the power generated by wind power and solar power fluctuates, it is difficult to use it as it is for the power supply of factories and the heating and cooling of homes. Therefore, its value is low. In other words, thermal power is expensive, and it is natural that wind power is treated as cheap power.

But what if you have a storage battery in your home? Even if the power fluctuates, it can be used stably once it is stored in a storage battery and electricity is taken out from it. Therefore, households with storage batteries can buy fluctuating electricity. Users who need a large amount of power will find it difficult to rely on storage batteries for everything, so buy and use stable power even if it is a little expensive. On the other hand, households with storage batteries buy and use electricity that is volatile but inexpensive. You can also use it to keep an eye on the ever-changing electricity price, and buy electricity when it is cheap to charge the storage battery. Alternatively, the electricity stored in the storage battery can be sold at a high price when the electricity available is insufficient. In this way, the flow of electricity based on economic principles can be created. This is funny. It was a scale from my eyes.

Technological innovation needed to “store” electricity

In an era of large amounts of renewable energy, many wind turbines and solar cells will be needed. At the same time, an “energy buffer”, which is a storage for electricity, must be introduced. An easy-to-understand example is the storage battery mentioned above.

In addition, a method is being attempted in which the energy of electricity obtained from solar power or wind power is converted into heat and stored, and the heat is used to generate electricity when needed. A liquid heated using the energy of electricity is stored in a thermos bottle, and when electricity is needed, the heat of the liquid creates water vapor to generate electricity (* 4). To store heat, we use a type of substance called “molten salt,” which melts and becomes liquid at high temperatures. Thermal power generation uses steam produced by the heat generated by thermal power to turn a turbine to generate electricity. In the method using molten salt, the energy of solar power and wind power is temporarily stored as heat, but after that, it is the same as thermal power generation. The time difference between power generation and the need for power does not matter with this method. You don’t have to use expensive storage batteries.

Attempts are also being made to electrolyze water with the surplus electricity, convert energy into the form of hydrogen as fuel, and store it. It is an attempt to save energy as a chemical substance. In addition, although sunlight is still used, there are also attempts at artificial photosynthesis for the purpose of making organic substances from carbon dioxide and water, making hydrogen gas, etc. by imitating the function of plants instead of generating electricity with it. (*Five).

Here are some of the major challenges in introducing large amounts of renewable energy.

  • The biggest problem with batteries is cost. It requires an order of magnitude larger capacity than that for mobile devices. It will be very expensive. In addition, lithium-ion batteries often cause fire accidents. If a fire breaks out with a large storage battery, it will be difficult. It is necessary to make a storage battery that does not cause a fire.
  • Most of the suitable sites for windmills are on the sea. It should not be damaged by typhoons and should not be easily corroded by sea breeze. Find a cheap way to install it in the ocean. It would be too expensive to build a hard pillar from the seabed.
  • To increase the efficiency of the wind turbine, it is essential to increase the diameter (* 6). However, doing so increases the load on the bearing. The bearing that supports the blade with a diameter of 100 meters can be broken and cannot be replaced. How do you make a strong bearing? Also, what is the structure that makes it difficult for the bearing to be overloaded?
  • In order to convert the generated energy into substances such as hydrogen (* 7), it is necessary to stably continue the chemical reaction with fluctuating electric power. Issues such as efficiency and longevity.
  • Problems with semiconductor switch elements. Solar cells and storage batteries are direct current, and power systems such as power transmission are alternating current. To freely control the flow of electricity, a semiconductor device that performs AC / DC conversion with low loss is required. At present, high-efficiency semiconductors are expensive (* 8).
  • Waste problem. If a large number of solar cells, storage batteries, wind turbines, etc. are introduced, a large number of new and highly efficient devices will soon reach the end of their service life. There are problems with disposal and recycling. Think about throwing it away, disassembling it, and recycling it from the beginning so that you don’t have to worry about it later.
  • As you can see, renewable energy has many challenges for its introduction, and it is also difficult to use. However, considering reducing carbon dioxide emissions, reducing fossil fuel dependence and ensuring energy security, it seems inevitable that a large amount of carbon dioxide will be introduced. There are many challenges, but this also means that we are expected to advance science and technology, and there is much work to be done.

A new society where power generation and transmission systems are fundamentally changed

For example, an electric car. If the power to run is produced at a thermal power plant, the place where carbon dioxide is emitted will simply move from the car to the power plant. But what if you think of an electric vehicle battery as a storage battery for buying and storing renewable energy cheaply at home? That way, you may not need to use a home-use battery. By incorporating electric vehicles into the new flow of electricity, electric vehicles will play a new social role beyond just running tools. For that purpose, it is necessary to extend the number of times that charging and discharging can be repeated and extend the life of the battery. Also, if you think about going out suddenly, it is not always full, so you need to be able to charge quickly in a few minutes.

By incorporating a temporary storage tank for electricity in the power system, the peak current flowing through the power line can be reduced. It can be said that more power can be sent with the same power line as it is now. There are many suitable locations for wind and solar power in areas where there are few people and where electricity is not used. If the power generated there is directly input to the power line, the power line will be heavily loaded. However, if you install a temporary storage tank (for example, a storage battery), you can send a lot of electricity by distributing it for a long time.

I didn’t mention it this time, but iron making emits a lot of carbon dioxide. This is because coal is used to make iron that can be used from a rusty state. On the other hand, removing oxygen from rusty iron can also be done by electrolysis. If electricity derived from renewable energy that does not emit carbon dioxide becomes cheaper, it can be refined with this. In other words, there seems to be another iron making method. I think there is a big frontier here as well.

If the basics of society, energy, change, a new Japan and the world will come. What should we prepare by drawing the ideal image of the future society? If you think about it, you will find out a lot. There are huge opportunities for scientists and engineers, and it is an exciting world.

  • * 1 World Energy Outlook 2017
  • * 2 Strom 2030
  • * 3 Abe Laboratory, Department of Technology Management Strategy, Graduate School of Engineering, The University of Tokyo
  • * 4 NEDO Renewable Energy Technology White Paper, 2nd Edition, Chapter 5 , Superconducting heat generator for wind power generation
  • * 5
  • * 6 NEDO Renewable Energy Technology White Paper, 2nd Edition, Chapter 3
  • * 7 For example, hydrogen utilization technology derived from renewable energy
  • * 8 Current status and issues of the compound semiconductor industry