During the Mid-Autumn Festival holiday, the moon was undoubtedly the star of social media. While admiring the moon, did this curious question ever cross your mind 鈥?can moonlight generate electricity? The answer is not "no," but rather 鈥?physically yes, but from an engineering standpoint, far from sufficient. Scroll down to explore the fascinating questions that arise while moon-gazing.

Moonlight Is Essentially "Second-Hand Sunlight"

The moon does not emit light itself. It is merely a "sunlight reflector," and not a very efficient one at that. The lunar surface reflects only about 12% of the sunlight that hits it back to Earth, with the rest absorbed by lunar rock. It is precisely this process 鈥?first reflection, then discount, then a 380,000-kilometer journey 鈥?that creates an astronomical gap between moonlight and sunlight in terms of energy. Under standard ground photovoltaic testing conditions, noon solar irradiance is approximately 1,000 watts per square meter. When the full moon is overhead, moonlight irradiance is only about 0.002 watts per square meter 鈥?a difference of roughly 500,000 times. Correspondingly, the number of photons under full moon conditions is also extremely sparse. Irradiance refers to the radiant power received per unit area.

Photovoltaic Power Generation Relies on the "Photovoltaic Effect"

When photon energy exceeds the bandgap of silicon (approximately 1.12 electron volts), it can transfer energy to electrons in the photovoltaic panel. Electrons break free from their bonds and flow toward the negative electrode, while the remaining "holes" flow toward the positive electrode, generating voltage. Moonlight and sunlight share the same origin. Let us do the math: taking near-infrared light with a wavelength of 750 nanometers, according to the photon energy formula, single photon energy equals Planck's constant times the speed of light divided by wavelength, which equals 6.626脳10鈭?34 joule-seconds times 3脳10鈦?meters per second divided by 750 nanometers, approximately 1.65 electron volts, which is greater than 1.12 electron volts. One electron volt equals 1.602脳10^-19 joules. Therefore, moonlight can indeed trigger the photovoltaic effect. But "can trigger" and "can be used" are two different things. The photon energy is sufficient, but the photon density is too low. The number of photons incident on the photovoltaic panel per unit time is extremely small. There is voltage, but no current, and the output power approaches zero 鈥?it cannot even reach the threshold of an inverter.

Even If Voltage Were Generated, It Would Not Be Enough

Even if a photovoltaic panel under a full moon did somehow accumulate voltage, it would output direct current. To be fed into the grid and reach households, it must be converted by an inverter into 220-volt alternating current. Inverters have a "minimum startup voltage threshold." If the voltage does not reach the threshold, the inverter will not work. If it barely reaches the threshold, the voltage cannot sustain the operating range, causing repeated startup and failure cycles. Let us calculate using a common 450-watt, 60-cell series-connected crystalline silicon module. The calculation process can be skipped, and we can go directly to the result. It is known that the open-circuit voltage of a monocrystalline silicon cell is approximately 0.683 volts. The minimum startup voltage of a common micro-inverter is approximately 30 volts, with an operating range of approximately 33 to 58 volts. Assuming the output current at open circuit is zero, the ideality factor n is approximately 1, and the ratio of photogenerated current to dark saturation current is far greater than 1. Substituting the open-circuit voltage of 0.683 volts and thermal voltage of 0.0257 volts, according to the single-diode model of a solar cell, the open-circuit voltage per cell is approximately 0.683 + 1 脳 0.0257 脳 ln(0.002/1000), which equals approximately 0.346 volts. In other words, under full moon conditions, the open-circuit voltage of a single cell drops from approximately 0.683 volts to approximately 0.346 volts. The open-circuit voltage of a series-connected crystalline silicon module is approximately 0.346 脳 60, which equals approximately 20.8 volts, less than 30 volts 鈥?it does not even reach the inverter's threshold, let alone the operating range starting at 33 volts. The result is that the voltage cannot even "wake up" the inverter.

Is Moonlight Power Generation Truly a "Luxury"?

Traditional crystalline silicon panels are indeed essentially "indifferent" to moonlight. However, the boundaries of photovoltaic materials are being re-explored by a new material called perovskite. In Jiangsu, the feasibility of perovskite "weak-light power generation" has been verified. Perovskite's advantages, such as high photon absorption rate and high tolerance to defects, allow it to maintain relatively high open-circuit voltage and fill factor under weak light. Compared to ordinary crystalline silicon panels, which "eat more and work more, but strike when there is no food," perovskite is more like "working slowly even with little food." In February 2025, the world's first GW-level perovskite photovoltaic module production line was put into operation in Wuxi. On September 14 of this year, six departments including the Jiangsu Provincial Development and Reform Commission, the Provincial Department of Science and Technology, and the Provincial Department of Industry and Information Technology jointly issued the "Implementation Plan for Promoting Pilot Application of Perovskite Photovoltaic Cells in Jiangsu Province," providing policy support for multi-scenario applications of "perovskite photovoltaic plus." The boundaries of energy are being redefined.

The Moon Has More Than One Way to Generate Electricity

At this point, you might feel a bit discouraged: so this bright moon is good for nothing except looking pretty? Not at all. The account of moonlight contributing to photovoltaics is indeed pitifully small, but the moon has another skill 鈥?it uses gravity to "pull" seawater. Humanity has already turned this force into kilowatt-level, even hundred-thousand-kilowatt-level, electric current delivered to the grid. This is tidal power generation. The moon's gravity pulls seawater, causing periodic rises and falls in sea level. Tidal power stations use these regular fluctuations to drive water turbines, which in turn drive generators to produce electricity. This is by no means armchair theory. China's largest and the world's fourth-largest tidal power station 鈥?the Jiangxia Tidal Power Test Station 鈥?is located in Wenling, Zhejiang. With an installed capacity of 4.1 megawatts and an average tidal range of 5.08 meters in its sea area, it uses a single-reservoir bidirectional operation mode and is a textbook example of tidal power generation.

The Moon Gives Humanity Two Energy Accounts

One is the still-explored "microwatt-level" moonlight photovoltaics. The other is the already-implemented "megawatt-level" tidal power generation. The same bright moon, vastly different forms of energy. From "chasing the sun" to "not even letting moonlight go to waste," the direction of photovoltaic technology evolution has never changed. It is not about waiting for the best light, but about learning to make good use of every kind of light. Of course, to truly guarantee the lights of thousands of homes during the Mid-Autumn Festival, we still rely on mature photovoltaics, energy storage, and grid dispatch. Moonlight photovoltaics today is still just a small step at the frontier of technology.