Created for expats living in Japan

How does Solar Power Work and What are the Benefits?

This article is originally posted by Hinatao Energy in Japanese, translated by Japan Living Guide.

You have probably seen large panels attached to the roof of a house in Japan. They are called 'solar panels' and serve as generators that exchange the sun's light energy into electricity. Solar power is an excellent way to generate electricity even during power cuts. It is a system that can protect your family in times of emergency as well.

In this article, you can learn how solar power works, its impact on the environment and the benefits of solar power for saving money on your electricity bill.

How Solar Power Works

Sunlight reaches the Earth from the Sun, which is located far out in space. Sunlight, which makes us feel warm in winter, falls on us as light energy. Photovoltaic power generation systems utilize this boundless light energy.

How can solar power be used to generate electricity?

Photovoltaic power generation uses 'solar cells' to convert light energy directly into electrical energy. Solar cells made from semiconductors such as silicon generate electricity in response to the intensity of sunlight.

The effect of the movement of electrons in semiconductors to generate electricity is known as the 'photovoltaic effect' or 'photoelectric effect'. Sunlight uses this photoelectric effect to generate electricity.

What are solar panels?

A solar panel is a large panel attached to the roof of a house or other structure to generate solar power.

If you look closely at a solar panel, you will see squares. Each of these cells is called a module, and one of the cells that further divides the module is called a cell (solar cell). Many solar cells are arranged in a row to form a solar panel.

This arrangement of solar cells makes it possible to generate electricity efficiently by using a large amount of sunlight at once. In recent years, there has been an increase in the number of solar power generation facilities known as 'mega-solar', where many giant solar panels are lined up side by side.

Conversely, there are also mobile batteries with small solar panels that can be used to charge smartphones and other devices in times of disaster.

How much electricity can the solar system generate?

For example, if all of the sun's light energy could be converted into electricity, it is said that about one hour of power generation could supply all of humanity's electricity needs for a year. How much electricity can a power generation system that harnesses such powerful energy from sunlight actually generate if it is installed on the roof of your home?

Residential photovoltaic systems use units of kW (kilowatts) and kWh (kilowatt-hours), where kW stands for 'instantaneous electricity' and kWh for 'the amount of electricity that flows over a certain period of time'. In other words, 1 kWh is the amount of electricity generated when 1 kW of electricity is generated for one hour.

The average annual power generation in Japan is around 1,000 kWh to 1,200 kWh per kW. The average installed capacity of solar panels used in homes is 4-6 kW, with average values of 70 kW to 250 kW of electricity generated per panel.

Benefits and Challenges of Solar Power

The solar panels required for photovoltaic power generation can generate electricity efficiently if they are installed in locations that are well exposed to sunlight. Depending on their size, there are no local or other restrictions* on where they can be installed, and solar panels have the advantage that they can be easily installed in individual households, with some solar panels being large enough to be used in detached houses.

However, there are also disadvantages, such as unstable power generation depending on the season and time of day, including days without sunlight and at night. In addition, mega-solar systems require a large area of land on which to lay out many panels, and the need for transmission lines to send the large amount of electricity generated over a long distance also adds to the construction costs.

*Limited to cases where there is no contractual agreement under building code regulations, etc.

Is Solar Energy Friendly to the Environment and Households?

Solar power is a form of renewable energy that is both environmentally and household friendly. Why is it both environmentally and household friendly? Here is why.

What is renewable energy without carbon dioxide emissions?

The electricity we use in our daily lives is produced from a variety of resources that exist on Earth. Renewable energies are energy sources such as solar, wind, geothermal, hydroelectric and biomass, which never run out and will continue to be produced in the future in the cycle of the natural world.

In contrast to renewable energies, which meet the three criteria of never running out, being ubiquitous and emitting no carbon dioxide, finite resources such as oil, coal and natural gas are known as 'fossil fuels'.

Renewable energies, including solar power, do not emit carbon dioxide, which is considered a cause of global warming, during power generation. For this reason, they are increasingly attracting attention as an energy source for the future, when environmental issues must be taken into consideration.

What is the difference between thermal and nuclear power?

Thermal power generation is a method of power generation that uses thermal energy obtained by burning fuels such as oil, coal and natural gas. It is easy to adjust the amount of electricity generated, and thermal power generation accounts for more than 80% of power generation in Japan.

However, as Japan is poor in these fuel resources, it relies on imports for approximately 97-99% of its fossil fuels. Of fossil fuels, about 88% of crude oil (part of petroleum) is imported from countries in the Middle East, where countries tend to be unstable*, and prices fluctuate greatly in the event of civil war or conflict.

Another problem with coal- and oil-fuelled thermal power generation is that it emits air pollutants such as NOx (nitrogen oxides) and SOx (sulphur oxides) during power generation.

Nuclear power, like solar power, does not emit carbon dioxide when generating electricity. Furthermore, the fuel can be reused.

Uranium, the fuel for nuclear power, is imported from abroad, but it can be generated using far fewer resources than fossil fuels. It is also used as one of the main forms of energy in Japan, as it is less expensive than thermal power, etc. However, the Great East Japan Earthquake of 2011, which caused extensive damage in the Tohoku region, highlighted a major safety risk. From this point of view, there is an urgent need to secure energy generation alternatives to thermal and nuclear power.

(*) Source: Agency for Natural Resources and Energy, "2019 - Energy problems facing Japan"

Is it true that it can be used during disasters and power cuts?

Solar power can generate its own electricity in the event of a power failure during a disaster, as long as the equipment, including the solar panels, is not damaged. Recently, it has become possible to supplement up to 1500 W of power as an emergency power source.

So what happens at night when the sun is gone? Photovoltaic power itself does not have a storage function, so in order to use electricity at night, storage batteries need to be installed alongside the solar panels. This way, the solar energy stored during the day can also be used at night. If the storage function is installed, you can use the electricity even in the event of a blackout, which is a great relief.

What are the financial benefits of solar power?

When a solar PV system is installed, the electricity generated can be used in the home and any surplus electricity can be sold (FIT) to the electricity company. The price of installing solar has fallen, lowering the hurdle to installation however, the FIT price has also fallen, so it is important to take into account the payback year and maintenance costs.

Solar Power and Life

In recent years, natural disasters have been on the increase due to the effects of global warming. Photovoltaic power generation, which can also be used as an emergency power source during power cuts and disasters, is attracting a great deal of attention as a measure to prevent global warming, as well as for building towns that are resilient to natural disasters.

If you are considering building a new house or rebuilding a house, or if you would like to review your electricity bills, HINATAO ENERGY provides their services in English. Please contact them if you would like to find out more information.

Solar Generators / Solar Chargers

You can purchase them online via Amazon. Click the image(s) to see details.