In this blog post, we will examine why renewable energy is gaining attention amid fossil fuel depletion and environmental issues, and explore its potential.
The two oil crises of 1974 and 1978 confirmed the global influence of oil-producing countries and made people realize how dependent we are on fossil fuels. The non-oil-producing countries that suffered huge economic losses as a result of these crises became interested in developing renewable energy technologies to reduce their dependence on oil imports. In addition, global warming was first officially pointed out in the 1972 Club of Rome report, and carbon dioxide was later identified as the main cause of global warming, increasing the need for renewable energy as an environmentally friendly energy source.
With only about 40 years of remaining fossil fuel reserves and the safety of nuclear energy, which had been touted as an alternative energy source, called into question by several nuclear power plant accidents, the infinite supply and stability of renewable energy were seen as major advantages over existing energy sources. In addition, since the Kyoto Protocol came into effect in 1997, about 32 countries around the world have implemented a carbon emissions trading system in which they can buy and sell carbon emission credits. In May 2012, a bill on a carbon emissions trading system was passed by the National Assembly of Korea, and it is expected that the development of renewable energy will be promoted as a project that will bring economic benefits beyond the scope of environmental protection and alternative energy development.
In Korea, renewable energy is defined in Article 2 of the Act on the Promotion of the Development and Use of New and Renewable Energy as “energy that is converted from existing fossil fuels or from renewable resources such as sunlight, water, geothermal energy, precipitation, living organisms, and organic matter, including solar, bio, wind, small hydro, fuel cells, coal liquefaction, gasification, heavy residue gasification, marine, waste, geothermal, and hydrogen.” Renewable energy is also referred to as new energy, renewable energy, green energy, and alternative energy depending on the country, and the classification system also varies slightly. For example, Korea separates bioenergy and waste energy, but the United States combines them and refers to them as biomass.
According to a survey by the Korea Energy Agency, waste energy accounted for 67.5% of renewable energy in Korea, followed by small hydro energy (12.73%) and bioenergy (12.7%). In the United States, biomass (including waste energy) accounted for 53%, followed by small hydro energy (31%) and wind energy (11%). Globally, bioenergy (or waste energy) and small hydro energy are the most widely used renewable energy sources, and the types of energy used vary depending on the location and geographical characteristics of each country. Renewable energy is classified according to the type of energy source used directly, and this article will look at the definitions, energy use methods, and advantages and disadvantages of each type of energy according to the classification of renewable energy in Korea.
Solar energy is divided into solar thermal energy and solar photovoltaic energy. Solar thermal energy is used to generate power by using collected solar heat to produce solar water heaters or steam. Solar energy uses the photovoltaic effect of solar cells to generate electrical energy. Solar energy has the disadvantage of being available only for a limited time each day and being affected by weather and seasons, but it has the advantages of being pollution-free, infinite, and reaching the earth’s surface in quantities 100,000 times greater than the total energy used on earth.
Ocean energy refers to electricity or heat produced by converting ocean tides, waves, currents, temperature differences, etc. Tidal energy is a method of submerging underwater wind turbine turbines in tidal currents and using the force of the tides to turn the turbines. Wave energy uses a piston connected to a buoy to generate electricity by reciprocating motion caused by the up and down movement of waves. However, since power must be generated directly in the marine environment, it is difficult to avoid environmental pollution.
Geothermal energy refers to the heat energy that comes out of the ground through the surface, which contains high-temperature water and rocks. Currently, geothermal energy is mainly used directly, but research is also being conducted on a method of drawing high-temperature water from the ground and evaporating it into a low-boiling-point fluid to turn turbines. Geothermal energy has unlimited potential for power generation, as approximately 47% of solar energy is stored in the ground in the form of geothermal energy and is reproduced through the radioactive isotope decay process underground.
Wind energy is a method of converting the kinetic energy of air flow into mechanical energy by rotating windmills, which is then converted into electrical energy. The disadvantages are that wind is unpredictable and wind turbines can spoil the natural environment, but large-scale complexes have relatively low power generation costs, making them commercially viable. Korea has extensive mountainous and coastal areas, so there is a lot of interest in wind energy research.
Small hydroelectric power generation is similar in principle to large hydroelectric power generation, but it is smaller in scale and technically simpler, harmonizing with local conditions. The potential energy of water is converted into kinetic energy, which is used to turn a turbine and generate electricity. However, disadvantages include environmental destruction caused by dam construction, high initial construction costs, and fluctuations in power generation depending on rainfall.
Next is the case of obtaining energy mainly in the form of fuel by decomposing or synthesizing organic or inorganic materials. Energy produced in the form of fuel is easy to store and transport, making it highly valuable.
Bioenergy refers to liquid, gas, solid fuels, or electrical and thermal energy obtained by decomposing biomass. Bioenergy has the advantages of being easy to store and transport, but the biomass used as raw material must be grown and harvested, and there is a possibility that food prices will skyrocket as food is consumed as fuel. As alternatives, research on enzymes that decompose organic matter such as cellulose and research using algae are considered important.
Waste energy refers to liquid or gas fuels produced by decomposing waste, or waste heat obtained by burning waste. Waste energy can solve waste disposal problems, but the environmental pollutants generated during the incineration process are a disadvantage.
Coal energy is energy generated by converting low-grade raw materials into synthetic gas using coal gasification technology and driving turbines. The coal gasification process and gas purification process are key.
Hydrogen energy is obtained by decomposing water or organic matter and has the advantage of emitting almost no environmental pollutants during combustion. If technology for storing hydrogen is developed, it can be easily transported as gas or liquid, making it as convenient as existing fossil fuels.
Fuel cells are energy conversion devices that convert the chemical energy of fuel into electrical energy through electrochemical reactions. Fuel cells have the advantage of not producing exhaust gas because they do not undergo combustion, but they lack the durability and economic feasibility required for commercialization.
In summary, each type of renewable energy has its own advantages and disadvantages, but their common goal is to use sustainable energy and minimize carbon emissions to reduce environmental pollution. Currently, renewable energy accounts for about 12% of global electricity production, and the UK and Germany have set a target of producing about 30% of their total energy from renewable energy sources by 2030. Korea has also set a target of generating approximately 20% of its total energy from renewable energy sources by 2030. With these global efforts, the research field and industrial market for renewable energy are expected to grow and become more important over time.
