Is Moonlight Strong Enough to Power Solar Panels?

The moon can provide light to see by but not enough for power.

Moonlight differs from sunlight in many ways, primarily in that moonlight is actually reflected sunlight that bounces off the moon in the direction of the Earth. Changes in the power density of moonlight make it impossible to generate electricity from moonlight with current technology.

The Facts

The amount of energy received from the sun is colossal: 342 watts per square meter, on average, over the course of a year. Of this, 31 percent is reflected immediately back into space by reflective surfaces in Earth's atmosphere and on the surface, but the remaining 69 percent is absorbed by the ecosystem. By comparison, the intensity of moonlight per square meter is estimated at 1 milliwatt, approximately 1/342,000th of the amount received directly from the sun.

Significance

Solar panels are measured in terms of efficiency, or their capacity to convert solar power into electrical energy. All such conversions must lose some power due to entropy, but far more is lost due to inefficiencies of current technology. As of 2009, the most efficient solar panels achieve an efficiency of 31.25 percent; theoretically, using these panels to power a low power 1-watt device from moonlight would require 3,200 square meters of panels. This would require nearly 90 of the 11.5 meter dishes used by this system, generating an amount of power that can be replicated easily by human effort.

Time Frame

Solar power efficiency gains are a primary goal of the industry, but due to the massive discrepancy between solar and lunar light density, deployment always will be geared toward better power generation from sunlight. Moonlight is sufficient for humans to see by, but it won't be powering our devices.

Geography

The curvature and tilt of Earth's axis determines the distribution of sunlight over the course of a year (the length of Earth's orbit around the sun). This causes the sine wave pattern that appears at the solar termination lines when Earth's geography is projected on a flat surface. Moonlight distribution is determined by the position of the moon in the lunar orbit around Earth, which also causes the moon's phases.

Potential

The total sunlight received by the Earth in one year far exceeds current human energy usage, so even with efficiency discrepancies, solar power is expected to be a key part of future green energy technologies.

References

• Natural forcing of the climate system
• Does moonlight penetrate water to any depth?
• EarthDesk 5.1.1