As the subtropical high pressure system retreats southward and eastward, many parts of Shandong have welcomed comfortable autumn weather in recent days. For the power grid, the pressure of summer peak-load power supply has also gradually eased. Shandong is a major load province and a major province for new energy installations, making grid balancing pressures and challenges even greater, serving as a practical sample for observing China's summer power supply guarantees and the construction of the new-type power system.

On August 3, Shandong Grid's midday and evening peaks both hit record highs, reaching 131 million and 119 million kilowatts respectively. The "dual peaks" in load directly reflect the rigid electricity demand during the midsummer season across the province and represent an ultimate test for summer supply guarantees. However, where there are peaks, there must be valleys — after the peaks pass, the load curve inevitably declines. "Peaks" and "valleys" go hand in hand, and fluctuations of tens of millions of kilowatts within a single day pose a cascading challenge to Shandong Grid's balance. Today, let us decode the power balancing challenges across different time windows through a day's "dual-peak, dual-valley" load curve (using August 24 as an example), and see how Shandong's power sector finds the optimal solution between power supply guarantees and new energy consumption amid peak-valley fluctuations.

Pre-Dawn Hours: "Buildup" in the Deep Valley

As cities and villages sink into slumber and factory production lines gradually wind down, at 4:30 AM, Shandong Grid's load curve slides into its lowest point of the day. Yet the low point is not static — it is quietly "building up" for the day's peak. "The early morning trough is a period of relatively lower system regulation pressure, but that does not mean we can relax. We must push thermal power units down to minimum output, and even arrange unit shutdowns for standby, to accommodate the day's lowest load," said Zhang Bing, Director of the Planning Division at State Grid Shandong Electric Power Dispatch and Control Center. Under the cover of night, wind farms continue to operate, and power from external channels flows steadily according to the day-ahead plan, keeping the system stable under low-load conditions. After 5 AM, residents begin to rise, and electricity use for breakfast preparation and lighting starts to increase, causing a slight uptick in the curve — a small load bulge that comes almost entirely from the residential sector. "Although the load fluctuation during this period is small, its signal significance is strong. It marks the transition of society from nighttime dormancy to daytime production mode, and it is the first key node for us to judge the day's overall load trend," noted Zhou Lei, a fifth-level staff member at the Planning Division of State Grid Shandong Electric Power Dispatch and Control Center. After a full night's rest, the grid's first major test is about to begin.

Morning Hours: Battling the First Load Peak

At 7 AM, the city awakens — subways begin running, factory machines start up one by one, and cooling equipment in office buildings and residential areas switches on, with electricity load steadily rising in step with the pace of social life and production. When the clock approaches 11 AM, Shandong Grid's load curve reaches the highest point of the day, with factory production lines running at full capacity and growing cooling demand jointly pushing the curve upward. During the rapid load climb, photovoltaic output also begins to rise gradually but has not yet reached maximum capacity — this process mainly tests the system's upward ramping capability. Shandong Grid has taken the lead in establishing the nation's first ramping ancillary service market, precisely incentivizing regulation resources to respond to rapid load growth and rapid changes in new energy output. By coordinating provincial thermal power, external power imports, and storage resources in synergy, the system maximizes absorption of clean photovoltaic energy while firmly maintaining power supply margins, achieving "full utilization of green power with supply redundancy." "For the morning peak, our main play is coordination. Photovoltaics are on top, thermal power provides the safety net, external power supplements, and storage builds reserves — with the ancillary service market providing frequency regulation and ramping support behind the scenes. It is this combination of forces that firmly holds the peak," said Zhang Bing. The image shows the Shandong North Lubei saline-alkali tidal flat 10-million-kilowatt wind-solar-storage-transmission integration base.

Midday Hours: A "Relative Trough" in High-Level Operation

After the midday load peak, the province-wide electricity load naturally declines in line with industrial lunch breaks and social rhythm, with the curve hitting the day's second trough around 1 PM. However, at this time, steel, chemical, and manufacturing industries continue to operate at high load, and the industrial electricity base creates a "high-level low" characteristic. This trough is more than 30 million kilowatts higher than the pre-dawn trough — exceeding the peak load of many provinces — making it a "relative trough" within the day's high-level operation. Meanwhile, noon is also the period of strongest sunlight, with photovoltaic output surging to its daily peak. On clear days, Shandong's PV output consistently exceeds 50 million kilowatts, equivalent to the full-capacity output of 50 million-kilowatt-class thermal power units. On one hand, electricity demand is declining; on the other, massive amounts of green power are flooding into the grid — the pressure of new energy consumption becomes prominent. This "one decline, one rise" is also a test of the system's regulation capability. To carve out more consumption space for new energy, Shandong Grid is pushing full coverage of flexibility retrofits for directly dispatched utility coal-fired units, with thermal units reduced to minimum technical output during the midday trough, and some even performing intraday start-stop peaking. At the same time, the market's "invisible hand" is also at work. On one hand, low spot prices guide storage stations to fully charge and pumped-storage stations to fully pump. On the other hand, Shandong was the first to implement a five-tier tariff structure — sharp peak, peak, flat, trough, and deep trough — guiding some production loads to adjust proactively, reducing user electricity costs while also easing system regulation pressure.

Evening Hours: The "Peak-Battling Campaign"

As night falls, residents return home, appliances such as air conditioners and televisions switch on, and large shopping malls light up brightly — household and tertiary-sector electricity use forms an "evening relay." Around 7:30 PM, the load curve climbs again to reach the day's second peak. During the evening peak, PV output has dropped to nearly zero, and at this point, a multi-force "peak-battling campaign" begins on Shandong Grid. The first surge of force comes from energy storage. Power charged during the daytime when new energy was abundant is now discharged into the grid. In special situations where grid balancing is tight, the grid can also centrally dispatch storage. On August 3, the day Shandong Grid's load hit a record high, the province's 172 new-type storage stations were centrally called upon to discharge — 73 independent storage stations and 99 new-energy co-located storage stations participated, with a maximum discharge power of 11.98 million kilowatts. The image shows State Grid Laiwu Power Supply Company staff providing on-site service for orderly dispatch of the Ze'an Mengjia independent storage station.

Pan Ye, a specialist at the Planning Division of State Grid Shandong Electric Power Dispatch and Control Center, explained: "At midday when new energy is abundant, spot market prices are low; during the evening peak, spot prices are higher. Storage discharge supports the province's evening peak while also earning corresponding price spread profits for storage enterprises." It is worth noting that independent storage stations not only profit from the spot market through "low-charge, high-discharge" strategies and provide supply support, but can also participate in grid frequency regulation as independent entities to earn ancillary service revenue. Meanwhile, thermal units rapidly ramp up to peak output, external power arrives via UHV channels as reinforcement, and multiple power sources work in concert to seamlessly fill the supply-demand gap left by the retreat of photovoltaics. The image shows an EV owner discharging to the grid via a V2G charger at night.

On the load side, virtual power plants capture price signals to precisely adjust electricity usage, and electric vehicles can also reverse-discharge power to the grid — these dispersed adjustable resources accumulate grain by grain to form a combined force for supply guarantees. A multi-dimensional resource pool works in coordination to firmly support the day's second load peak. The load curve is the "electrocardiogram" of economic and social operation. Behind Shandong's "dual peaks and dual valleys" lies the resilience and vitality of the province's industrial economy, as well as the new challenges facing dispatch operations in the construction of the new-type power system. The shift from traditional "source-follows-load" to "source-grid-load-storage interaction" balancing models, the continuous evolution of load and power supply forms, and the constant fluctuations of load and output curves all point to one constant: the day-in, day-out balancing test and the year-after-year commitment to supply security. Ensuring uninterrupted industrial production and keeping the lights on for people's livelihoods, State Grid Shandong Electric Power has written a contemporary answer for new-type power system construction through practice at the intersection of power supply guarantees and energy transition.

Source: State Grid Shandong Electric Power Company