# How does the efficacy of solar cells on Mars compare with Earth?

Mars gets less than half the light that we get on Earth and there are dust storms, but the atmosphere is much thinner and there are no clouds. After all factors have been considered, how effective are solar cells on Mars (compared with those on Earth)?

Or, in other words (if you prefer a more precisely-defined question), how much harvestable solar power is available (per unit of area) on average on the respective equators of Earth and Mars?

I'm asking in order to understand possible power solutions for hypothetical future colonies. So assume expensive panels with all the bells and whistles like heat regulation, solar tracking (if that's a thing), etc.

Since cloud coverage varies around the Earth, I'd like to get best and worst case scenarios (no clouds and 100% cloudy all the time, respectively) to put the average solar power output potential of Mars into perspective.

• This is an interesting question. One problem is that on Earth, annual cloud cover ranges between almost zero to almost 100% depending on where you look. Africa, Australia, Western regions in the Americas all have large areas of very low average cloudy skies. How would you like the comparison done? Also, temperature matters - can we afford to add temperature regulation systems, or do we have to plop them down on the ground and live with whatever temperature they happen to find?
– uhoh
Feb 13 '17 at 1:27
• Yes add temperature regulation. Looking with regards to an optimized system for a long-term colony. As for the cloud coverage, we'll have to do best and worst case scenarios. The reason I'm asking is to put the estimated Mars power performance value into perspective. Thanks. Feb 13 '17 at 4:46
• OK great! Can you edit your question to make it clear there? Comments are not permanent. Any important clarification or change should be made in the question itself, where it will continue to be seen.
– uhoh
Feb 13 '17 at 5:23
• This NASA paper goes into detail of what they had to consider in terms of solar power for the rovers. Feb 13 '17 at 13:07
• Possible duplicate of Solar panels on Mars? Aug 15 '18 at 16:18

You might want to check out solar potential maps.

This gives you your "on average" potential power harvested for the Earth, by summing up the daily solar potentials - which builds in accounting for weather, night etc. According to this map, the best areas are near the equator in Chile and slightly north of the equator in Chad/Libya/Sudan, which produce around $2800 kWh/m^2$ per year - roughly $320 W/m^2$.

On Mars, the calculations are slightly more difficult. Mars' irradiance is roughly $590 W/m^2$ - half that of Earth. Mars barely has an atmosphere, however - it's around 0.5% of Earth's so we can essentially ignore atmospheric effects. Temperatures on the Martian equator vary significantly - around $25 ^oC$ at noon, and around $-60 ^oC$ at night (I have no idea how this varies with Mars' orbit, so take that as you wish). Given that the panels won't be operating at night, and Mars has an Earth-ish temperature at day, I don't think temperature is too big of a factor - Mars is colder than Earth, but Solar panels don't mind the cold. NASA is running solar powered rovers on Mars, and they seem to be doing fine, until they got caught in dust storms.

Dust storms are a big problem. According to this research paper from 1993, there is a 1 in 3 chance of a planet-wide dust storm occurring on Mars every year. These last a few weeks - a few months, on average. There are also "smaller" continent sized dust storms which last a few weeks as well. For the sake of argument, lets say that there is a 10% chance that our base is in a dust storm at any given point in time. Martian dust storms vary in intensity - lets say that, on average, 2/3 of sunlight is blocked. Accounting for the day-night cycle, we have a solar potential of $275 W/m^2$ - this seems like an estimate on the high end, and a low end estimate is probably around $200 W/m^2$.

Again, these figures are just potentials. I haven't accounted for efficiency (around 20% - feel free to calculate that if you want). I also haven't accounted for the panel lifespan - on Earth, this is 15-20 years. On Mars, I expect this to be significantly lower due to dust storms.