Issues associated with renewable energy utilization

2022/11/04 2023/01/03

lenemas

The expantion of renewable energy utilization is now a common theme globally. However, just keeping to increase installation of renewable energy facilites woud not achive the sustainable circulation of enregy in our society. There are several issues to be fixed, for instance,

The gap between locations where we can extract the renewable energy and where we need energy
The gap between timings when we can extract the renewable energy and when we need energy
The renewable energy is often extracted as a form of electric power, which needs to be converted to other forms of energy in some occasions.

We first need to understand the issues themselves. This post addresses the first one listed above, the gap in locations for electric power generation and usage.

Where we use energy?

The figure below is obtained a picture of the Earth at night, provided by NASA.^[1]

The shining area are the locations in which light is used at night, and therefore we live. You see regions of Europe, Ameria, India, Australia, East asia bright in the piture. These bright area are location needing energy.

Where the renewable energy are available?

Next we see where we can generate electric power using the renewable energy.

Ministry of the Environment summarizes such data in Japan. The figure^[2] below illustrates where in Japan are potentially righ in renewable energy.

* Sorry that the figure is in Japanese, but will be translated into English.
太陽光：sunlight
水力：hydroelectric
洋上風力：off-shore wind
陸上風力：on-shore wind

Sunlights are available across whole Japan, but more intense in Hokkaido and Kyu-shu areas. Hydroelectric and off-shore wind are rich in the side of the sea of Japan, and the on-shore wind is more available in Northern area of Hokkaido.

Comparing these two figures highlights the gap between the locations where we can generate electric power using the renewable energy, and where we need energy. You could efficiently generate electric power in one location, which however is physically far from the location where we need it.

You may consider the transmittion of electric power using the stablished electric power distribution network in Japan, but it is not practically easy because of the gap in voltage, frequency, aforementioned timinig, and losses by the transmittion.

The most likely option would be to convert the generated electric power into something else. into what..? it would be chemical that can store energy in chemical bonds. Such chemicals are called "energy carrier", and most representative ones are hydrogen, ammonia, methyl-cycrohexane, methane. The high energy density characterizes these chemicals, meaning that, by using energy carrier, we can carry "energy" in small volume or weight. It is considered a key to the imprementation of renewable energy on a large scale how effectively we utilize the energy carrier.