Overcoming the volatility of renewable energy

A research team at the Korea Energy Research Institute has successfully demonstrated the effectiveness of a green hydrogen system used to supplement renewable energy variability.
^{*Green Hydrogen: Hydrogen produced by water electrolysis, in which electricity from renewable sources such as solar and wind energy is injected into water to produce hydrogen and oxygen. This production method is an environmentally friendly hydrogen production process, with no carbon dioxide emissions.}

Dr. Joungho Park and his research team at the Energy AI and Computational Science Laboratory at the Korea Energy Research Institute (KIER) concluded that green hydrogen, which facilitates the conversion and storage of excess energy, is the most effective way to overcome the problem of variability in the energy-using power grid renewable energy combining solar and wind energy.

Renewable energy is increasingly highlighted as a key means of achieving carbon neutrality and energy security. At the 28th United Nations Conference of the Parties (COP-28, December 2023), an agreement was reached to triple renewable energy capacity by 2030. In support of this global initiative, the Republic of Korea also announced the ‘Strategy to Expand Distribution and Chain Strengthening renewable energy supply” (Ministry of Trade, Industry and Energy, May 2024) to support the sustainable development of the country’s renewable energy industry.

To develop renewable energy, in addition to distribution, it is extremely important to manage variability in factors such as intermittent solar radiation and wind speed. Ensuring the safety and efficiency of electricity operation requires the ability to respond flexibly to both shortages and surpluses. Power-to-Gas (P2G) technology has been proposed as a solution, which uses surplus renewable energy to produce emission-free green hydrogen and compensates for variability through timely use.
^{*P2G (Power-to-Gas): A technology that converts electricity into a gas such as hydrogen or methane, using and storing renewable electricity from sources such as solar and wind.}

The research team developed a model enabling the determination of the optimal scale and verification of the effectiveness of the green hydrogen system needed in the renewable energy grid. The model is based on weather and electricity demand data on Jeju Island, where solar and wind power account for 20% of total energy production. Thanks to this, the model can determine the optimal scale of the green hydrogen system in line with the 2030 target of achieving a 21.6% share in renewable energy production.

After entering meteorological data, such as wind speed, solar radiation and temperature, into the developed model, hourly energy production is calculated and compared with actual power demand data. In this way, we check the adequacy of energy supply and demand, and in case of surplus or undersupply, we use a green hydrogen installation and batteries to determine the optimal Leveled Cost of Electricity (sLCOE) and Loss Probability of Power Supply (LPSP) system. Therefore, the economic feasibility and sustainability of any green hydrogen and battery system can be determined as a function of scale and the optimal scale can be predicted.
^{*sLCOE (System Levelized Cost of Electricity): This term refers to the levelized cost of electricity, which is calculated by dividing the total capital and operating costs of power generation by the total amount of electricity supplied. Unlike the traditional LCOE model, which is based on the total amount of electricity produced and does not take into account the costs of power loss such as power curtailments, sLCOE eliminates these shortcomings by taking into account the electricity supplied.
**LPSP (Loss of Power Supply Probability): This is an indicator of the stability of the power grid, calculated by dividing the supplied electricity by the required electricity. A value close to 0 means that the power supply is adequately meeting demand. If the value is greater than 0, it means that the demand is not fully met, which may lead to power outages. Therefore, an energy conversion and storage system is needed to make up for this deficiency.}

The simulation results using the model showed that when using only solar energy, batteries are the most effective solution to overcome variability, while when using only wind energy, green hydrogen is the most effective. However, with an equal mix of solar and wind energy, green hydrogen showed the highest economic efficiency and the lowest energy supply losses. This finding is consistent with policies promoting the sustainable use of solar and wind energy and can serve as baseline data for establishing a renewable energy transition strategy.

Dr. Joungho Park, first author, said: “This study is significant because it verifies the effectiveness of using green hydrogen to address power grid instability and power constraints resulting from renewable energy development.” He added: “By designing optimal configurations of energy conversion and storage systems tailored to the characteristics and situations of different regions, this study provides the government and companies with the knowledge necessary to develop green hydrogen strategies, thereby facilitating rational decision-making.”

The research results, conducted in cooperation with the team of Professor Jay H. Lee from the Mork Family Department of Chemical Engineering and Materials Science at the University of Southern California (USC), were published in the international journal “Energy Conversion and Management”. The research was carried out under the basic research program of the Korea Energy Research Institute (KIER).