Where does the electricity used at home come from? Let us organize how power generation works and the types of energy resources.
Basic Knowledge
Main power generation methods:
① Thermal power generation: Fossil fuels (coal, petroleum, and natural gas) are burned to boil water, and steam turns a turbine. About 70% of Japan's electricity.
② Hydroelectric power generation: The potential energy of water falling from a high place (a dam) turns a turbine. About 9% of electricity.
③ Nuclear power generation: Heat produced by the nuclear fission of uranium is used. About 5〜7% of electricity (about 30% before the Great East Japan Earthquake).
④ Solar power generation: Solar cells directly convert light into electricity. About 9% of electricity.
⑤ Wind power generation: Wind turns a turbine. About 1%.
⑥ Geothermal power generation: Underground heat produces steam, which turns a turbine.
⑦ Biomass power generation: Plants and organic matter are burned.
Classification of energy resources:
・Fossil fuels: Coal, petroleum, and natural gas (finite・CO2 emissions)
・Renewable energy: Sunlight, wind, water, geothermal heat, and biomass (not depleted・low CO2 emissions)
Thermal power generation (Burn fossil fuels to turn a turbine. High CO2 emissions)
Hydroelectric power generation (Turn a turbine using the potential energy of water. Clean)
Nuclear power generation (Heat is generated by nuclear fission. Low CO2 emissions, but waste and accident risks)
Renewable energy (Solar, wind, hydroelectric, geothermal, and biomass energy)
Fossil fuels (Coal, petroleum, and natural gas. CO2 emissions and limited resources are issues)
Energy mix (A strategy that combines several power generation methods)
In Depth (Background・Significance)
Each power generation method has advantages and disadvantages:
Thermal: Stable・easy to adjust / CO2 emissions・fuel costs・limited resources
Hydroelectric: Clean・stable / Construction costs・environmental destruction・limited suitable sites
Nuclear: High output・low CO2 emissions / Waste・accident risks・fuel management
Solar: Clean・distributed / Weather-dependent・zero at night・requires land area
Wind: Clean / Dependent on wind speed・noise・effects on birds
Geothermal: Stable・domestic / Limited suitable sites・competition with hot spring areas
After the 2011 Fukushima nuclear accident, Japan experienced a major change in energy policy. Japan now aims for carbon neutrality by 2050 and is promoting the expansion of renewable energy.
Worldwide, China・the United States・and Germany are leading renewable-energy countries, and Denmark has achieved a wind-power share of more than 50%.
The development of energy storage technology (lithium-ion batteries・hydrogen・pumped-storage power generation) is the key to making highly variable renewable energy practical.
- Japan's electricity: thermal about 70%, hydroelectric and solar about 9% each, nuclear 5〜7%
- Thermal: stable but produces much CO2
- Nuclear: low CO2 emissions but waste and accident risks
- Renewable E: solar, wind, hydroelectric, geothermal, and biomass
- Carbon neutrality by 2050 is the goal
- Energy mix: a strategy combining several methods
- Advances in energy storage technology are key to expanding renewable energy
Points to Note (Easily Confused)
① Renewable energy is not depleted, whereas fossil fuels are finite and produce CO2. ② The principles of thermal, nuclear, and geothermal power generation are the same in that they use steam to turn a turbine (only the heat source differs). ③ Hydroelectric and wind power use kinetic energy to turn turbines directly. ④ Solar power generation directly produces electricity using a semiconductor (the photovoltaic effect) and is the only major power generation method that does not use a turbine.
Practice
- Which power generation method produces the most electricity in Japan?
- Give two examples of renewable energy.
- Give one essential difference between solar power generation and other power generation methods.