Cheap, efficient solar

[Jim Franklin]

Nature, many are worried about the climate now...if we start to strip tens or hundreds of terrawatts of energy from the atmosphere what effect do you think this will have on weather patterns, precipitation and temperature?

Solar cells, even the best ones available are only around 40% efficient, as are wind turbines..which basically means for every watt you want, you need to take TWO from the energy budget of the planet..

Forgive me, but I think that even less intelligent than burning fossil fuels.

On a small scale these technologies have their place, but on a national/global generation level they are worse than what we have.

[Claire]

There is some truth in what Jim's saying - it's true that the energy balance for solar in the UK with currently available technology is quite marginal, but in sunnier places, or in the UK in a few years, with some of the more efficient technologies (such as the one in the original post) coming along, the balance is more in favour of solar. We discussed this in more depth during the last month or so, somewhere or other in this forum.... (edit - here) I do think solar should be treated with caution just now for the UK case though.

I don't believe there would be a problem with solar disrupting weather patterns etc. though. The amount of solar energy incident on the earth compared to what we use is huge, plus already a lot of the energy is absorbed by the ground or whatever covers it. Also the energy isn't destroyed, merely converted to another form and its "use" most often means it is mostly turned into heat anyway.... I just can't see that it could have an effect - could be wrong of course though. I guess a numerical analysis would give more of an idea of the scale of things but it's way too late at night for me to be thinking about taking that on just now I'm afraid .

[the nature scene]

Originally Posted by Jim Franklin

Nature, many are worried about the climate now...if we start to strip tens or hundreds of terrawatts of energy from the atmosphere what effect do you think this will have on weather patterns, precipitation and temperature?

Not sure I'm following you on that one, since the process isn't really one of "stripping" the atmosphere of energy.

Anyways, I already agreed that solar power is not currently efficient, and no I don't advocate it as being put into widespread use until it is efficient. But again, this is no reason to abandon the quest for solar power, just a challenge and call for human ingenuity. I'm having trouble figuring out why exactly the desire for a clean, renewable source of energy is a bad thing.

I'm not even really an advocate for solar power necessarily - but I am an advocate for clean, renewable energy, and moreover, choices of the sources of the energy. Solar power may only have a future in certain parts of the world, much like wind power. I am also a fan of nuclear power, but I'm afraid it will take a long time for humans to get over their fears of it.

[Jim Franklin]

Nature, even if we could make solar power 100% efficient..which is a physics impossibility, the best we could likely hope for is around 80%..solar power can stillonly be used for small scale and localised production, such as road signs etc

Overnight I did a little research, if we wanted to generate 25% of the power requirements of Man from renewables and split this down the middle for Wind and Solar, and we made them both 100% efficient, even at todays figures we would need to generate some 28000 Terrawatts of electricity.. (approximate figure as accurate demand figures for most none industrialised nations are inaccessible).

28K Terrrawatts is a MASSIVE figure.

However as I have said, n reality we would likely be taking about 60k Terrawatts from the atmosphere. It is a red herring to say that energy is not destroyed only changed, and that we would be converting to this that and the other, the simple truth is that this energy would be removed from the budget of the planet's weather system, and at these levels we are talking energy levels of reasonable sized hurricanes, and we know what effect that amount of energy has in the atmosphere.

Obviously this would be spread over the globe, but it would be asymetric due to the major generation areas being in the more industrialised nations, so concentrated in Europe, The US, China, Brasil and certain other places.

The other effect is that to generate 12.5% of the planet's energy from solar has another effect..the energy that would usually be absorbed by the ground would now be collected by the cells, so not only would we be removing energy from the overall global budget, but we would be cooling the ground in the area of the collectors..double wammy you might say.

[the nature scene]

Nonetheless I'd say you still have a distorted view of how solar panels work. They do not reach up and "grab" energy from the atmosphere. They collect and convert energy that would otherwise be absorbed by the ground.

I think your treatment of the atmosphere and weather system as having an energy budget is misguided. Even if energy were to be taken, as you claim (but it's not, just converted), the sun is a constant input into the atmosphere and would make up the difference more than likely.

Aside from that, the amount of solar energy that pours into our atmosphere and planet is far more than we would need or would ever be able to convert.
2 weeks worth of solar energy would be roughly equivalent to the amount of energy provided by all fossil fuels on earth.

And again, I think you're setting up a straw-man argument because no one is this post has written that solar energy should be the single, widespread, institutionalized energy source. Everyone understands that the ability of solar to be a viable energy source is location specific.

Still waiting for the reason why people shouldn't be doing research on solar energy, as there are far more remote areas, removed from the grid, in the world than those which are in a power grid. Solar only is viable in remote, sunny areas - precisely where energy and electricity are needed.

[Jim Franklin]

Nature, please don't take this comment as condescending as it is not meant to be, but I think I understand the physics of the atmosphere better than you do.

As well as being a sparky, I have a HNC in Electrical Engineering, a first class honours in Astonomy and have been readin text books on Nuclear/Geo and Astro physics since I was about 12 years old.

You forget that the energy absorbed during the day does not go away, about 30% is reradiated back into the atmosphere during daylight hours, and another 25% during darkness, which is why the globe doesn't freeze at night. This is true for the ocean to the ocean occurs during the night.

Now when that energy is absorbed by solar panels, it is converted for our use, yes a small proportion is reradiated back as thermal energy (Infra-Red), but the bulk of that absorbed is used up as losses in the system and as electricity for our use, and that means that the energy that would have been given to the planet, either by heating the ground or the atmosphere is lost, therefore the heating does not occur.

On a small scale this is negligable, but on the massive scale some speak of it will have an impact as the energy the atmosphere uses to drive the weather systems will be diminished.

It is too early in the morning for a long post on the energy budget of the planet, but I will do one tomorrow with accurate figures if I can locate them in time from my notes and reference material.

[the nature scene]

Sure, I'll concede your educational background in the science of the atmosphere is greater than mine. My degree is in economics. I view everything as a series of trade-offs and competing opportunities.

That was a pretty good explanation to allow me to understand your concerns in laymen's terms. Thanks. So that energy may not be returned to the atmosphere, but it is converted into a form that we derive utility from correct? On one level, I would say we could look at it as a trade-off. We get electricty and the price we pay is more erratic weather, or at at least different weather. Electricity certainly has its benefits, does it not?

Correct me if I am wrong, but it seemed before that you were trying to prove, on a scientific basis, that solar power is not only less efficient than fossil fuels but is actually a foolish and dangerous choice because of potential impacts on weather patterns.

Even though I have a non-scientific background, I appreciate the insights that scientific work can give us. It would be great if you could offer some publications that provide a scientific basis for your claims about solar power's potential effect on weather patterns.

But even then, we are still left with choices and trade-offs. And it seems that all of our options include some degree of uncertainty about their consequences. Right now, the reason solar power does not hold a larger market share is because its relative costs are too high when compared to alternatives (possibly due to subsidies for fossil fuels) - purely an economic reason. Your concerns bring up a whole new issue about the environmental consequences of solar power.

Climate change has become the ultimate weapon of the precautionary principle it seems. People are calling for the end of fossil fuel production and consumption because of the potential effects of emissions on climate change. Potential negative consequences are the fears, but any credible report on climate change also talks about the possible benefits of climate change for certain parts of the world. The major issue we face is uncertainty over the future. That uncertainty seems to be the underlying reason why some people desire an end to fossil fuels.

Now again, you're the science guy so tell me if I am wrong, but I would imagine that, at best, we are uncertain about the effects of solar power on weather patterns and the like. You are wanting one consequence, a negative one, of solar power use to be the basis for not using it.

But how do we weigh this possible negative against the possible positives of solar energy? How about the savings from fuel transportation costs associated with solar power? Solar power is seemingly economically viable in developing parts of the world that are characterized by remote areas. Lack of infrastructure means that fuel transportation costs for traditional fuels are high in these regions, and solar power provides a possible solution to this issue. Foolish?

A third of the world lives without electricity. Solar power seemingly provides a relatively cheap energy source for many developing regions because the costs associated with building the required infrastructure for traditional energy sources are prohibiting. The demand for electricity is going to continue to increase in coming years, and solar power offers an economically viable option to the remote regions of the world.

Not only should we weigh the costs and benefits of solar power in particular, we must also compare solar to its alternatives. In developed parts of the world, fossil fuels are cheaper and therefore in widespread use. But they are dirty compared to solar power. Your concern over solar power's effect on the atmosphere would need to be compared against the effect of fossil fuel use on the atmosphere in order to carry some weight.

Uncertainties exist with all possible energy sources. There are always negatives and positives associated with alternatives. Fossil fuels give us abundant electricity at low financial costs - but their use results in emissions which can pollute the air and contribute to the greenhouse effect. Solar energy can address emissions problems caused by traditional fuels, can save costs in transportation and possibly maintenance. But overall it is more expensive at the moment, and you say solar power use also comes with the potential to disrupt weather patterns. Nuclear power is cheap and clean, but its use comes with tremendous uncertainty over potential meltdowns and waste disposal.

Point being, in order to make policy judgments you have to look at a comprehensive picture that includes scientific analysis as well as economic and social aspects. No decision is so easy that a narrow scientific analysis can be the basis of a comprehensive policy.

So if you could link to some studies or provide some sources about the possible negative impacts of solar power, everyone will be better off. But keep in mind that potential impact on weather is just one of many issues that must be addressed when seriously discussing the viability of solar power.

I appreciate your consideration of the economic viability of solar power on a regional scale and your concerns about average output, but your point is moot to the parties who actually make the decisions about whether or not to use solar power. Individuals and organizations do not face these average costs; rather, they must consider a variety of factors that are specific to the time, location, and scale of a project.

Considering only averages, we would conclude that solar power is not a good choice. But there exist numerous instances of solar power being used to generate heat and electricity, as well as for the desalination of water. Why? Are these people making irrational decisions and throwing resources away? On the contrary, they have made informed decisions based on the costs and benefits that they face directly. I predict that solar power will continue to be developed and put into use around the world. To what degree? I cannot say. It seems likely that fossil fuels will continue to dominate in the more developed parts of the world...

...of course alternatives like solar, wind, geothermal, and nuclear, etc. could benefit from the removal of subsidies for fossil fuels.

[Claire]

Originally Posted by Jim Franklin

As well as being a sparky, I have a HNC in Electrical Engineering, a first class honours in Astonomy and have been readin text books on Nuclear/Geo and Astro physics since I was about 12 years old.

So does my 1st class honours (Mechanical Engineering), MA (Industrial Engineering) and errr half a PhD trump that then or not?

Seriously though, I don't think anyone should rush off believing this as gospel. I'm not an expert and haven't had need to apply my never-that-hot knowledge of things electrical and energetic for a while, but a lot of what Jim posted seems dubious to me. He also still has not responded to the issue of what percentage of the energy incident on the earth would be absorbed even if we were powering all our needs by solar PV. I believe that's quite small.

Re: efficiency of solar - I'm not too sure exactly how this works - is it % of total sunlight energy incident on the panel, or % of the bandwidth the panel can actually use? And what happens to the rest of it anyway? And how does this narrow bandwidth of use affect the argument of heating the atmosphere (i.e. do solar panels "use" mostly light in the IR band which I suspect is what has most effect in providing energy that powers weather systems? or how does that work if I'm wrong, cos that's a bit of a shot in the dark?)

One thing I do know is that energy "lost" to inefficiency is most often lost as heat (e.g. due to friction) and noise, the same with what we "use" to do work for us. It doesn't just disappear or something - "energy cannot be created or destroyed", you just convert it to another form. Quite how this affects weather systems though I'm not too sure. Don't these things get a bit messy near the earth's surface anyway?

OK, I have to do some work today so I'm stopping here... I'll be interested to see Jim's further post but wanted to step in with a note of caution, just in case....

[Richard]

Originally Posted by Claire

So does my 1st class honours (Mechanical Engineering), MA (Industrial Engineering) and errr half a PhD trump that then or not?

I have a Scout's badge in knot-tying. Clearly that beats you all.

[Richard]

Originally Posted by Jim Franklin

You forget that the energy absorbed during the day does not go away, about 30% is reradiated back into the atmosphere during daylight hours, and another 25% during darkness, which is why the globe doesn't freeze at night. This is true for the ocean to the ocean occurs during the night.

Now when that energy is absorbed by solar panels, it is converted for our use, yes a small proportion is reradiated back as thermal energy (Infra-Red), but the bulk of that absorbed is used up as losses in the system and as electricity for our use, and that means that the energy that would have been given to the planet, either by heating the ground or the atmosphere is lost, therefore the heating does not occur.

On a small scale this is negligable, but on the massive scale some speak of it will have an impact as the energy the atmosphere uses to drive the weather systems will be diminished.

It is too early in the morning for a long post on the energy budget of the planet, but I will do one tomorrow with accurate figures if I can locate them in time from my notes and reference material.

Even if the effect you're talking about exists (I don't think it does but for the sake of argument, let's assume it does) then I don't think it would have a major effect on the world's climate and any effect would be swamped by other factors.

Consider: the Earth's surface is currently about 3% urbanised, with 5/8's of the Earth's surface covered in water. So this gives about 1.1% of the total surface of the Earth as urbanised. As an extreme case, lets assume that all roofs in the world are covered completely with solar panels and that 50% of all urban areas are roofs (vast overestimation, but let's just assume). This gives an area of the world's surface covered by solar panels of 0.56% (i.e. a fraction of 1%).

Now compare this to the fact that (depending on which report you believe) about 50% of the Earths surface has been altered by mankind i.e. due to agriculture, cities, roads, forest clearance, hydro schemes etc. This means that about 19% of the total surface of the Earth has been altered in some way from its natural state. These alterations also have an impact on the way incoming solar energy interacts with the Earth's surface e.g. the way a car park absorbs and emits sunlight will be vastly different to the way, say, the forest that was there before the car park will absorb and emit light.

So on a comparison of altered surface area, existing land changes would be some 34 times as significant as covering all available roof space with PV panels.

So if you want to be worry about anything, I'd worry about the effect that we've had by altering the natural landscape and not about what further effect we would have if we implemented wide-scale use of solar panels.