# Sunlight per square, Mars v. Earth

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Gawdzilla Sama, Jul 26, 2018.

1. ### Gawdzilla SamaValued Senior Member

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Caveat: I broke my math bone in the fifth grade and it never worked right again.

Martian year is longer than Earth year and Mars is further away, right? Can someone tell me how much sunshine a square meter of ground on each planet would get per year? (Or per day if that's quicker.) Assume the ground is on the equator with axial tilt to be factored in later. Disregard weather, dust storms, etc., I need "ideal" numbers. Counting the number of planet-wide dust storms and their duration is a separate project.

Thanks. (And I hope that all makes sense-ish.)

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5. ### mathmanValued Senior Member

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You need to define the unit of "sunshine". In any case the ratio of the amounts is based on the inverse square law (of the distances from the sun of the two planets).

7. ### Gawdzilla SamaValued Senior Member

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Really? I was thinking of total energy from the sun, and probably failed to make that even slightly clear.

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9. ### SeattleValued Senior Member

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Roughly speaking Mars gets half the amount received on Earth.

10. ### Janus58Valued Senior Member

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Watts are already in joules per second, so it doesn't make sense to talk about watts per time unit unless you are dealing with a variation over time.

11. ### DaveC426913Valued Senior Member

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No need to complicate it.

Earth is 1AU from the Sun.
Mars is about 1.5AU from the Sun.
Light drops off as the square, so Mars receives 1/(1.5^2) = 1/2.25 as much light as Earth.

12. ### Gawdzilla SamaValued Senior Member

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Good to know that.

13. ### James RJust this guy, you know?Staff Member

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At the Earth's surface it is more like 1000 Watts per square metre. And on Mars, the irradiance is a bit less than 600 Watts per square metre.

14. ### Michael 345New year. PRESENT is 69 years oldValued Senior Member

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On a slight tangent

How much energy required to build a square metre solar panel and match with a suitable battery?

And using it 10 hours of sunlight per 24 hours expected life span of the unit?

Of course cost of shipping such units to Mars increases their value and extends the break even period

15. ### Gawdzilla SamaValued Senior Member

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The tomato information was more in line with my thoughts here.

16. ### billvonValued Senior Member

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Here on Earth energy payback times range from 1 to 4 years for solar panels, depending on type of construction. (i.e. within 1 year the panel generates more energy than it took to produce.) Modern panels have a ~25 year lifetime.

17. ### Michael 345New year. PRESENT is 69 years oldValued Senior Member

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Thanks

I have a fair number of mini devices with solar panels built in

Small items like a torch or a power bank for recharging phones

Still weighing up the cost of solar panels against the benifits

As a old fart the government provides a discount for power cost

Since my use is so low, the most heavy use items I have is fridge along with washing machine, and that is used very infrequently, the discount covered all my cost = power bill \$0

Solar panels advantage might be just be to run tv if grid goes down

18. ### billvonValued Senior Member

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Most 'standard' solar systems will not do that. FYI

19. ### Michael 345New year. PRESENT is 69 years oldValued Senior Member

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Did a check on my LED TV and seems to be power equivalent between 50 and 60 watts

Then checked 12 volt storage battery and moving on to a 12 volt DC converter to 240 volt AC

Seems can do if careful not to stuff up the TV electronics with poor sine waves

I have no intention of solar panels and battery converter system for TV. More just using the concept as a rough guage for possible future usage post cyclone

20. ### Gawdzilla SamaValued Senior Member

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Passing along a "thank you" from a twelve year old who is doing a speculative piece on "Farmers' Markets On Mars." Quite a clever young lady.

21. ### Michael 345New year. PRESENT is 69 years oldValued Senior Member

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Do they get to get to go on a field trip there?

22. ### billvonValued Senior Member

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OK. For 'real' solar (i.e. solar that saves you money) you need panels and a grid tie inverter. Most will not give you power when the grid goes out. The SMA inverters are the exception there; they will give you ~2000 watts AC as long as the sun is strong enough (and you have enough panels.)

For backup solar you'll need solar PV panels, a charge controller, a battery and an off grid inverter. There are a lot of decent sine wave inverters out there now.

23. ### Gawdzilla SamaValued Senior Member

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No, but someday... The stories had to be plausible, no trips to Mars on a brown dragon. (Kudos to the one that knows that reference.)