Solar Power Surpasses 50% of Daytime Supply for First Time
Solar power has, for the first time, surpassed half of the daytime power supply. Solar energy has emerged as a main power source, supporting air conditioning demand and industrial power, moving away from being a supplementary power source. Behind the positive functions of carbon reduction and fuel cost savings, a ‘volatile new normal’ has begun, where the power grid fluctuates according to weather and time of day.
◇ Solar Power Share Surpasses 50%, a Historic First
The daytime solar power output (28.95 GW) is equivalent to simultaneously operating 20 units of the latest 1.4 GW-class large nuclear reactors. By replacing the base load power during daytime, which previously had to be supplied by LNG (liquefied natural gas) or coal-fired power plants, solar power is simultaneously reducing greenhouse gas emissions and fuel cost burdens. In particular, if solar power absorbs the air conditioning demand during the peak summer daytime when electricity demand surges, it could also reduce the overall grid overload.
The issue is the power grid risks caused by extreme generation volatility. Immediately, every spring weekend when electricity demand plummets, a crisis arises. Factories and offices close, leading to surplus electricity, while good solar irradiation causes solar power generation to exceed demand. To balance supply and demand, power authorities first reduce LNG power plant output and absorb excess electricity by pumping water in pumped-storage power plants. If electricity still remains surplus, some solar power plants must halt operations. This is why the Korea Power Exchange’s ‘output control’—forcibly reducing solar power plant output—has become a regular occurrence.
According to data submitted by Rep. Jo Jiyeon’s office from the People Power Party to the Korea Power Exchange, solar power output control occurred a total of 56 times over two months from March to April this year. This marks an annual increase, following 2 times in the same period in 2024 and 47 times last year. Rep. Jo stated, “The problem of an unstable power system caused by the indiscriminate increase in solar power is leading to frequent output controls,” and added, “Measures are needed to ensure the efficiency and sustainability of renewable energy.”
◇ Expanding Power Grid and Storage Facilities is Key
In summer, the risk of a ‘sunset shock’ increases. While there is no surplus electricity during the day due to air conditioning demand, a supply cliff occurs in the evening as the sun sets. Solar power output plummets simultaneously with sunset, whereas urban air conditioning demand remains high for some time. If this gap is not filled within seconds by LNG power generation, pumped-storage power plants, or ESS (Energy Storage Systems), the power supply-demand balance could collapse instantly, leading directly to a large-scale blackout.
Experts say energy policies, which have focused solely on expanding renewable energy power plants, should shift toward balancing grid investments. While expanding solar power is an inevitable trend, merely increasing the number of solar power plants without adequately expanding ESS (Energy Storage Systems) to store surplus electricity will inevitably increase the risk of large-scale blackouts due to power instability. Professor Son Yang-hoon, emeritus professor at Incheon University, said, “Expanding solar power doesn’t just mean increasing the number of power plants; it signifies a shift from large-scale power plants to small-scale generation sources across the country,” adding, “Calculating where and how to send electricity becomes significantly more complex.” Professor Son emphasized, “We shouldn’t just focus on how many power plants to build but should simultaneously design grid connections and storage facility utilization.”