Large scale solar farms

[rivan]

This is prompted by the Dailytech post describing the possibility of cheap solar panels. As a disclaimer, I'm almost totally ignorant on the subjects I'm asking about. I'm here because I'm looking for the in-depth sort of explanations you guys tend to give.

For years, I've been hearing about a shift to solar and it's obvious improvement over fossil fuels in terms of environmental impact. There are two implementations of mega-scale solar that got me thinking about how the removal of that energy from an ecosystem would impact it.

The whole question revolves around how much of the solar energy is captured and how much is re-radiated as heat from the panels. Obviously, in small implementations, a single home or whatever, the impact is so tiny as to be inconsequential, but...

First, imagine a whole large city, say Chicago and all it's burbs, with every home and business roof being solar. What impact will the collection and conversion of sunlight have, as compared to standard rooftops? Will homes be cooler during the day? Do the panels, by virtue of their operation, insulate buildings better than standard roofing materials? Would nights in these dense cities then be cooler, as the buildings will no longer radiate the heat collected during the day?

Second, I've heard about proposed gigantic solar farms, usually in remote areas near the equator - the last I recall reading on was in the middle east, one of the countries considering it was trying to plan ahead for an eventual exhaustion of oil revenues. Sometimes they're arrays of mirrors focused on collectors that then heat water for steam... whatever, sometimes they're described just as arrays of solar panels. Either way, the effects could be similar. On a large/very large scale, tens/hundreds of acres at a time, could these possibly impact the weather or local climate? Would the change in net heat reaching the ground have any impact on winds, humidity or other weather factors?

So I guess the most basic question is this: how much of the total energy in a given amount of daylight is converted to energy by conventional panels, and is it high enough that thought should be given to the imapct of it's removal from the ecosystem?

 

[silverpig]

My guess about the city question is it wouldn't matter much. To me it seems that the dominant force in heating/cooling homes is the sun, followed closely by your heater and air conditioner. Also, paint colour, roads, and foliage will probably have a large effect than roofs covered with solar panels instead of shingles.

About the large areas, I'd hazard a guess that it'd make the areas a little cooler, but it probably wouldn't matter all that much again.

 

[f95toli]

It also depends on WHERE the energy is used. Using energy ultimately converts it into heat which means that if you use it close to the panels nothing changes, once used the energy is just radiated into space.
However, if the energy is converted into electricity and then transported to users far away you will change to local climate to some degree. But the efficienty of solar cells is only around 25% or so and even large farms only cover a relatively small area (compared to e.g. a lake) so in reality I don't think it will affect the ecosystem.

 

[dkozloski]

I read a study a while back that stated that if the American Southwest was covered with solar panels it would supply a fraction of the power currently being consumed and when the sun goes down the lights go out. Solar is a minor player at best.

 

[ChAoTiCpInOy]

What would happen if we have reflectors in space or we had the arrays in space?

 

[ch33zw1z]

Originally posted by: ChAoTiCpInOy
What would happen if we have reflectors in space or we had the arrays in space?

Finally, a way to shade the planet. We can make energy AND help the global warming issue!

 

[ChAoTiCpInOy]

Originally posted by: ch33zw1z

Originally posted by: ChAoTiCpInOy
What would happen if we have reflectors in space or we had the arrays in space?

Finally, a way to shade the planet. We can make energy AND help the global warming issue!

Is that sarcasm? A solar reflector or an array in space would be the most expensive option, but would make up for the extra money because it will allow for the collection of solar energy 24/7/365.

 

[Paperdoc]

Used on a massive scale, solar panels don't solve the real underlying problems at all. The real problem is that, every time we use energy for something, whether it is heating a building / home or powering an electrical motor, the final form of the energy "consumed" is simply low-temperature heat. That means, at long wavelengths. That plays right into the "Greenhouse Effect" that is the reason for all the angst on Global Warming.

Our earth receives from the sun a huge input of radiation energy at all wavelengths. There are gamma rays, x-rays, ultraviolet, visible light, infrared (heat) rays over a large range, etc, etc. Much of it penetrates through the atmosphere all the way to the surface where we live, and then a lot of it is re-radiated back up again. Now, the raditation at shorter wavelengths (higher energy) will manage to penetrate the atmosphere again (for the most part) and escape back into space. In fact, that is what happens to most of it. But a small amount gets absorbed by things on the surface. Plants absorb visible and ultraviolet light nergy, use it to convert chemicals into other chemicals, and store the energy as plant biomass. The ones that did this millions of years ago are now our petroleum reserves. The ones doing it this year may become corn-based ethanol for your car. Buildings absorb infrared heat rays. As surface bodies and structures warm up, they emit infrared rays themselves, but at much lower energy levels and longer wavelengths. These rays cannot penetrate the atmosphere back out into space - they are trapped in the atmosphere and on the surface.

The balance between radiation input from the sun and re-radiation back into space has been going on for billions of years, changing ever so slowly. But in very recent times - like, maye 1,000 years or much less - we people have taken to trapping more heat from the sun or using up old energy storehouses - think oil! - and releasing low-grade heat really quickly. It still can't escape, so our surface is heating up.

If we use massive solar panels to convert high-energy radiation from the sun into heat we can use, or into electricity we can send to another user, eventually all of that newly-trapped energy ends up as low-grade heat trapped in our atmosphere. Sure, it may reduce the generation of low-grade heat from burning oil, but it's still low-grade heat. And if we use this technology to supplement our rapidly-increasing use of fossil fuels so that we get to benefit from even greater total energy use, we generate even greater low-grade heat release at the surface!

What may save us from this consequence is that the pace of development of solar energy systems is slow enough that we may flood ourselves (sorry about the pun!) with the results of over-use of energy long before solar systems became a big enough player to matter.

 

[L00PY]

Originally posted by: dkozloski
I read a study a while back that stated that if the American Southwest was covered with solar panels it would supply a fraction of the power currently being consumed and when the sun goes down the lights go out. Solar is a minor player at best.

Care to actually find that study and reference it?

According to a scientist at the U.S. National Renewable Energy Laboratory, if you had 10,000^2 miles of cells with 10% efficiency. in 6 hours you'd generate all the electricity the US uses in 24 hours. That'd cover roughly 9% of Nevada -- a sizeable area but hardly the entire American Southwest.

 

[msparish]

Originally posted by: dkozloski
I read a study a while back that stated that if the American Southwest was covered with solar panels it would supply a fraction of the power currently being consumed and when the sun goes down the lights go out. Solar is a minor player at best.

Text

 

[BrownTown]

The problem with those maps is that you can't in real life just produce some huge solar installation that covers that land area 100%, so in reality the area covered would be much bigger. Also, since the sun only shines during the day you would need absurdly large amount of energy storage to get you through the nights. Also remember that the winter energy peaks would come at the same time solar was least effective so you would need even more capacity so that you could make it through winter.

Even the size of installation aside what REALLY makes solar unfeasible is its incredible cost. 10 times at least as much as conventional production techniques even disregarding the need to storage. Also, it should be pointed out that the ability to produce the number of solar panels even to meet up with growing demand does not exist by a long shot. Until someone finds an economic way to make solar panels they can never be anything more than a novelty item as they are today.

 

[dkozloski]

The source I was refering to was in the Scientific American Magazine several years ago. They were discussing the erection of practical arrays that could be assembled on suitable terrain and connected to the power grid. It didn't sound practical then and it doesn't now.

 

[ForumMaster]

Originally posted by: ch33zw1z

Originally posted by: ChAoTiCpInOy
What would happen if we have reflectors in space or we had the arrays in space?

Finally, a way to shade the planet. We can make energy AND help the global warming issue!

oh yeah, and have this happen?

Originally posted by: f95toli
It also depends on WHERE the energy is used. Using energy ultimately converts it into heat which means that if you use it close to the panels nothing changes, once used the energy is just radiated into space.
However, if the energy is converted into electricity and then transported to users far away you will change to local climate to some degree. But the efficienty of solar cells is only around 25% or so and even large farms only cover a relatively small area (compared to e.g. a lake) so in reality I don't think it will affect the ecosystem.

not true anymore. while i admit it will be several years before this technology is used, 25% efficency is not the max.