Questions regarding Global Warming

a reply to: TheRedneck

Where exactly in southern asia do you believe is NOT "electrified".

See the definition of hypothetical above.

So your 'hypothetical' has no known real world applications. I thought so. You are just arguing for the sake of arguing.

Would the industrial bulk users in that market be happy with the disruptions caused by the cycles of build, shutdown, rebuild that you suggest?

My suggestion would not have any appreciable shutdown time for the switchover. In addition, I would expect the switch to happen before such a market appeared.

So your suggestion is not based on any appreciable understanding of the real world engineering problems involved. I understand now.

Does the market have other more pressing needs that need to be funded before shutting down an operating electricity generator and rebuilding it?

Does that market have a stabile funding source for the duration of the staged build, shutdown, rebuild, shutdown, rebuild, you suggest?

I would not assume so, again based on the hypothetical.

So once again your suggested solution is based on no consideration for real world issues that render it invalid.

Who mentioned Korea?

I did. The point is what is the economic justification for the upgrade. Once the plant is online and operating no one is going to be interested in tearing it down and starting over. Not the user market, not the national government, not the IMF, and not the donor country that probably built it in exchange for votes at various international forums.

My suggestion would not have any appreciable shutdown time for the switchover. In addition, I would expect the switch to happen before such a market appeared.

Again you way underestimate the cost and engineering problems involved in the switch.

OK, here is the bottom line. You mentioned Myanmar above. Have you ever been to Myanmar? I have. I have also been to Timor Leste and actually seen the conditions and local solutions for myself.

These nations don't want or need large bulk power plants in order to electrify the rural areas. They have no effective national network to supply centralized base load electricity to little villages out in the middle of nowhere. And those villages couldn't afford to pay for the maintenance of the network that supplied them if it existed. Major cities in those countries are the market for such generation - and they are already fully electrified - though with varying degrees of reliability and under supply, of course. The demand for expansion of the supply is because the urban market, both domestic and industrial is demanding more and more. All governments see industrialization as the path out of poverty. To that end extending the grid to the rural countryside is just not on the radar.

So the solution for each rural village is a LOCAL, not a NATIONAL, low capacity network usually run on diesel generators though I have seen a couple of biomass generators, and of course small scale solar PV. There are even a couple of tiny hydro plants in Timor Leste. Its the diesel generators that need to go... they are expensive, dirty, and it can sometimes take several days to get spare parts. Fuel transportation costs alone exceed any revenue that could be derived from that electricity. Dirty Coal would have no economic or environmental advantage (except that the Australian government would probably pay them to take the coal from some of the Victorian mines) over diesel. Gassification may have some environmental advantage, but no economic advantage. These applications need local, small scale, economic solutions.

The thing is, your hypothetical is probably 2 decades out of relevance. The markets you hypothesize about just don't exist anymore. Yes demand is growing in the urban areas for network supplied central generation, but your hypothetical describes getting electricity to areas of no electricity; and there just aren't any except in the extreme bush, and they ain't gonna get a network anytime soon.

a reply to: TheRedneck

Sure. Where did you get your degree from again?
...
Now, think you can Google some answers to my queries? I will admit to using Google to look up some of your acronyms

I got my degree at a school where the two most important lessons were 1)it is far more practical to find out where to look for answers to questions than to try to memorize every detail on every subject, whether it was your specialty or not, and 2) think for your self and explore outside your comfort zone. If you rely only on rote memory and narrow experience, your tunnel vision will expose limitations with no way to overcome them.

So why do you seem embarrassed to admit that you used Google? Google and Wikipedia and the internet in general are fantastic tools for exploring outside your natural comfort zone. You are not alone in this, many people engaged in discussions on the internet seem to think that way. The styling "Hah, I make the assertion 'X' and you are too stupid to refute it without Googling it; therefore I win", is stupid and ignorant. Of course you have to have a properly developed BS detector to sort the wheat from the chaff, but arguing from a position of fact will trump arguing from a position of ignorance every time (and yes the political pun was intended).

Being proud of arguing from ignorance is downright masochistic.

the one about cancer threw me

I apologize for the typographical error. Thank you for correcting it for the rest of the readers (assuming there are any )

a reply to: rnaa

So your 'hypothetical' has no known real world applications. I thought so. You are just arguing for the sake of arguing.

That's what a hypothetical is.

And I didn't start the argument; you did. The OP posed a hypothetical question and I answered it. If you really want to discuss the best practical way to provide power to South Korea, then we can get into a discussion of Korean cultural aspects that might influence public opinion, Korean regulations on power plants, proximity to China (which would skew costs drastically), Korean geography, Korean power demands and anticipated growth, present infrastructure, and so on. But in the end, that would be a waste of time unless you are in a real-world position to accomplish any suggestions. I am not.

So your suggestion is not based on any appreciable understanding of the real world engineering problems involved. I understand now.

Correct. Engineers have no knowledge of the real world engineering problems.

...we desperately need sarcasm tags...

Have you ever been to Myanmar?

No, my information is here say based on reports I have seen from others. From that understanding, it is an undeveloped country with little to no infrastructure, and little to no technology, torn by regular wars between rival groups. Your description sounds a lot like what I envisioned. However, even if it did not, I would not presume to argue with you on that point.

I got my degree at a school where the two most important lessons were 1)it is far more practical to find out where to look for answers to questions than to try to memorize every detail on every subject, whether it was your specialty or not, and 2) think for your self and explore outside your comfort zone. If you rely only on rote memory and narrow experience, your tunnel vision will expose limitations with no way to overcome them.

In other words, no degree.

And I do not memorize; I comprehend. I comprehend the way steam turbines operate, the way electric generators produce power, the reason power is produced at the voltages and frequencies used, how the regulation systems work, the methods used in inverter technology, the manner in which photons produce electric power in a uniformly-doped silicon wafer, and power loss during transmission.

Comprehension is not a bad thing. You should try it sometime.

So why do you seem embarrassed to admit that you used Google?

I'm not. I just don't have to on certain subjects, especially when talking in generic terms.

If you ask me what the cell potential difference between NiCad and lead acid cells is, I can tell you off the top of my head that lead acid is a good bit higher, I believe 2.1 to 1.2 volts. If I am designing a project that uses such cells, I use Google... or better yet, just grab a reference book. But Google has limits. If I want to know the latest research into solar cell efficiency, Google will usually give outdated data. Instead, I look in IEEE, or maybe go talk to one of my professors who is active in solar cell research. But if I just need to know what a solar cell is made of, it's N-doped silicon. I don't need help for that.

Point being, Google is not the end-all, be-all of information you seem to think it is. My point was not that Google is a bad thing, but that there is more information out there. And also, it seems a bit presumptuous to explain engineering to an engineer...

But forgive me; I forget that you know more than engineers about engineering.

TheRedneck

a reply to: TheRedneck

The OP posed a hypothetical question and I answered it.

The OP question was:

The cheapest way to produce electricity in poor countries are coal industries i believe.

The discussion between you and I is whether or not your solution is appropriate. It is not. You make bad assumptions about what the needs of the electricity market in 'poor countries' actually are. A coal fired plant needs to be 'large' to be practical and to approach economic feasibility. This is only applicable where there is an effective network for transmission and demand to absorb the generated electricity. If these conditions are not met, then the plant is worthless, and not cheap at all.

If you really want to discuss the best practical way to provide power to South Korea,

I didn't say anything about supplying power to South Korea. South Korea already has a very mature electricity market - they are just fine determining their own way forward.

What I implied was that South Korea would likely provide the technology and construction expertise to any hypothetical plant you might specify to satisfy your hypothetical solution. They are among the world leaders in research, development, and manufacture of PV systems by the way. And they can build top of the line modern coal plants from off-the-shelf ready made plans too.

In other words, no degree.

False deduction.

From that understanding, it is an undeveloped country with little to no infrastructure, and little to no technology, torn by regular wars between rival groups. Your description sounds a lot like what I envisioned.

Correct interpretation.

With that in mind how does a large centralized base load coal fired generation plant provide a solution to the given hypothetical? Exactly where does the generated electricity go? How does it get to all those isolated villages? How do the villages grow to depend on that centralized generator when they are constantly under attack from rivals in the next village, or insurgents, or their own governments? The power lines are going to be the first thing cut.

Correct. Engineers have no knowledge of the real world engineering problems.

Sure it sounds sarcastic. But the saying goes if you don't want to sound ridiculous don't make ridiculous statements. You claim that you won't need to shut down the plant to change its input fuel configuration. Is that right?

Do you know the specifications of the concrete slab for the two different pieces of plant? Strength? Tiedown configuration? Plumbing? Enclosure? How do you get the first plant out of the way so the replacement can go in without shutting it down? How does the waste handling choreography change and how do they stay out of each others way? How does system testing go? How do you switch back and forth while the second system glitches are being ironed out? What is the cut over time frame? How long can the end user be expected to be patient while the new system is being brought online, then having to be shut down for 'tweaking', etc?

Clearly, as an engineer, you have never been involved in systems engineering or the design of a large scale manufacturing plant. Or even spent any time what-so-ever thinking about what your 'design it in a modular fashion and you can just swap them out like magic' assertions actually mean in the real world.

But if I just need to know what a solar cell is made of, it's N-doped silicon.

Except, of course, for the P-doped silicon cells. But lets not nitpick, modern cells use BOTH N-doped and P-Doped regions.

a reply to: rnaa

The discussion between you and I is whether or not your solution is appropriate.

Actually, the initial disagreement was an assertion that solar power is less expensive to construct than a traditional coal-fired plant. This is blatantly false, due to the larger necessity for area, the cost of the solar panels themselves, the cost of the inverter technology to convert low-voltage DC to high-voltage AC, UV-insensitive protection for the panels, the needed battery backups (these are actually so impractical most solar plants use a conventional type plant as back-up), and the power proration needed to compensate for weather. Operating cost is indeed one of the lowest; sunlight itself is free, and no moving parts mean less maintenance.

If one takes into account the cost of environmental regulations on fossil fuel plants, and the Federal subsidies on solar power in the US, then yes, the cost gap closes drastically. But that is not a technical concern; it is a political one. Without regulation or subsidies, coal is one of the cheapest plants to construct and solar photovoltaic one of the most expensive.

I didn't say anything about supplying power to South Korea. South Korea already has a very mature electricity market - they are just fine determining their own way forward.

Based on the amount of technology now coming out of South Korea, I don't doubt that. But my point was you were taking a hypothetical answer and attempting to dispute it based on a specific region that did not fit the premise.

With that in mind how does a large centralized base load coal fired generation plant provide a solution to the given hypothetical? Exactly where does the generated electricity go? How does it get to all those isolated villages? How do the villages grow to depend on that centralized generator when they are constantly under attack from rivals in the next village, or insurgents, or their own governments? The power lines are going to be the first thing cut.

Again, you are trying to apply a hypothetical answer to a specific region.

Myanmar would not be a realistic place to even attempt industrialization, due to the reasons you list. My responses were based on a country like Myanmar, in terms if industrialization, that is socially stable enough to become industrialized.

Sure it sounds sarcastic. But the saying goes if you don't want to sound ridiculous don't make ridiculous statements. You claim that you won't need to shut down the plant to change its input fuel configuration. Is that right?

I am saying that the turbines don't care what is producing the steam that turns them. Most power plants are built as multiple 'units' already. I fail to see where it becomes necessary for two units to be identical.

Step 1: quickly construct a small coal-fired power plant with a medium sized generator. Provide for multiple inputs to the steam lines, using a series of check and ball valves. At the same time, infrastructure will have to be constructed to deliver power to the heavier populated areas where initial demand is to be expected. Fastest construction and lowest initial cost.

Step 2: once that unit is online, construct a second, more modern and higher capacity unit for a less polluting fuel. Connect it to the main steam line. More expensive, but cleaner and can be performed while power is being generated.

Step 3: bring unit 2 online and take unit 1 offline. If coordinated properly, the switchover would be transparent to the turbines... if problems develop, any outages can be corrected in minutes by switching back to unit 1. Plant is now modern with increased capacity. Unit 1 can be used for backup or replaced as conditions dictate.

None of this is even difficult. Steam lines already contain such valves to isolate problems and perform maintenance.

I do not know the specifics you ask for off the top of my head. I do know all those specifications are well within the bounds of reality, since power plants already exist using them. If you want to award a contract for construction of this hypothetical plant, I'll be happy to look them up. Otherwise, I don't care as they have no bearing on hypothetical project viability.

Clearly, as an engineer, you have never been involved in systems engineering or the design of a large scale manufacturing plant.

Six years working construction/startup/testing at a 1 GW PWR nuclear plant. Does that count?

12 years doing structural design for industrial buildings. Does that count?

10 years operating my own design service (a C-Corp). Does that count?

Except, of course, for the P-doped silicon cells. But lets not nitpick, modern cells use BOTH N-doped and P-Doped regions.

There is much research going into solar cells right now. I wasn't aware anyone had overcome the transition speed issue associated with positive carriers, but that doesn't mean they haven't. I'll look into that sometime. I do know all the solar cells I have for experimentation are N-doped.

If they have, I hope the technology extends to P-channel MOSFETs. It would make transition speed matching in H-bridges much easier to design and more efficient, not to mention speed up logic circuit operation.

TheRedneck

a reply to: TheRedneck

Again, you are trying to apply a hypothetical answer to a specific region. Myanmar would not be a realistic place to even attempt industrialization, due to the reasons you list.

You named Myanmar as your hypothetical target market not me. You set the parameters for the hypothetical, not me.

I just demonstrated that your solution to your hypothetical case was not actually viable.

a reply to: TheRedneck

There is much research going into solar cells right now. I wasn't aware anyone had overcome the transition speed issue associated with positive carriers, but that doesn't mean they haven't. I'll look into that sometime. I do know all the solar cells I have for experimentation are N-doped.

Right. Perhaps you should refresh your professional development reading list:
pv Magazine, June 2012 article: Switch from p to n

In 2011, around 84 percent of PV module production was based on p-type crystalline silicon (Si) technology. N-type monocrystalline Si had a market share of around four percent. The remaining 12 percent was occupied by thin film PV (CdTe, a-Si, etc.). The p-type versus n-type Si technology scenario has historical reasons. The very first solar cell – fabricated in 1954 in the Bell-Labs – was made of a monocrystalline n-type Si wafer.

Until the 1980s, the main industrial application of PV was for space applications in the form of satellites and so on. P-type Si proved to be less sensitive to degradation caused by exposure to cosmic rays (high-energy particles such as protons and electrons). Thus for decades, all industrial PV cell development was based on p-type silicon.

Current developments seem to be moving more and more to n-doped, and good efficiency results are being obtained. However, your blanket assertion is incorrect.

a reply to: rnaa

I do not know the specifics you ask for off the top of my head. I do know all those specifications are well within the bounds of reality, since power plants already exist using them. If you want to award a contract for construction of this hypothetical plant, I'll be happy to look them up. Otherwise, I don't care as they have no bearing on hypothetical project viability.

Of course it has a bearing the project viability. If your solution is economically infeasible then you haven't provided a solution. The goal of the hypothetical is 'cheap and fast'. Your solution is neither, on any count or from any distance.

PV and onshore wind plants being built in 2016 are already faster and less expensive to build and operate than the equivalent coal fired plants being built in 2016. This is verifiable fact, not wishful thinking. There are no commercially operating 'clean coal' plants in existence. There are currently no operating development plants either, all previous research projects have shown quite clearly that the concepts involved are economically unfeasible (at least at present). Australia for one is getting ready to throw more money at the problem but for now 'Clean Coal' is a pipe dream. A myth.

No, I am not going to commission such a project. People with a lot more money than me and more business sense have already concluded that it is infeasible.

The Hazelwood plant in Australia is the largest in Australia and supplies about 5% of the Australian generating capacity. It has 8 operating units and a coal mine at its door step - literally. The current owner, Engie (formerly GDF Suez) the largest independent energy company in the world, is shutting Hazelwood down at an initial estimate 785 billion dollars. By the time it is finished, Engie will have invested well over 5 billion dollars in Hazelwood and they are just going to walk away from that.

Hazelwood is shutting down because Engie has determined that it is economically unfeasible to upgrade its infrastructure to 'clean coal' or any other power source - not even in stages like you want, and of course it is 'modular', all plants are. The plant, like any large plant, was built in stages and the generating units are independent of each other - exactly as you propose.

The distortions that subsidies and supply requirements put on the system mean that Engie is making money off that plant hand over fist, yet it is STILL cheaper for the company to shut it down than it is to upgrade it or even keep it running in its current configuration.

Oh, yeah, Hazelwood is also one of the dirtiest plants in the world.

a reply to: TheRedneck

Actually, the initial disagreement was an assertion that solar power is less expensive to construct than a traditional coal-fired plant. This is blatantly false, due to the larger necessity for area, the cost of the solar panels themselves, the cost of the inverter technology to convert low-voltage DC to high-voltage AC, UV-insensitive protection for the panels, the needed battery backups

This is simply not correct. The build cost per generated watt INCLUDES all of those itemized items - it is disingenuous for you to argue otherwise. Coal plants have equivalent issues even if they may not be exactly the same.

In exactly what way is the footprint of a PV plant any more difficult or expensive than an equivalent coal plant and its associated coal mine and waste dump? Do the build figures for such a coal plant include those costs? Why should a solar plant cost be computed any differently if you want to compare apples to apples?

Battery backup? You mean sorta like the giant capacitors sitting in every substation in every neighborhood in the world? You are seriously trying to tell me that a hypothetical set of storage batteries sitting there in those substations are not conceptually similar? Okay, continue deflecting away. Batteries are getting cheaper you know, or haven't you heard of Tesla and Red Flow and LG and Bosch and...?

Anyway, PV is not the only kind of Solar power. Personally I suspect that Concentrated Solar Power (CSP) will have a bigger role in large scale base load generation because the inherent use of a heat sink of one kind or another will naturally act as a no-sun backup. Of course if they can combine a PV farm with a CSP collector then you have serendipitous symbiote. You have to cool those PV cells to keep them efficient so why not use the waste heat too?

There are already semi-serious proposals to put a CSP plant in the Hazelwood mine.

a reply to: rnaa

You named Myanmar as your hypothetical target market not me. You set the parameters for the hypothetical, not me.

I did name Myanmar, as an example of an unindustrialized society, but my intent was not inclusive of the social unrest there. You seem completely intent on complicating the issue. I am curious why you can't simply state that such a hypothetical does not exist today and let it go at that? I would agree.

Current developments seem to be moving more and more to n-doped, and good efficiency results are being obtained. However, your blanket assertion is incorrect.

An incorrect assumption on my part. I assumed from your earlier post that someone was working with P-type substrates. I actually try to avoid semiconductor design, because I do not have ready access to the equipment required to implement my designs. Thus, it is easy for me to miss developments.

As your link demonstrates, however, my initial instinct was correct: increased mobility in N-type silicon over P-type results in higher effeciency, and has become the norm for solar cell substrates. I have several different types of solar cells in my shop I use for remote power for projects, and all of them are N-type.

I suppose I should re-examine my tactics when debating you. My normal response to surprising information in an area I am not intimately familiar with is to tentatively accept the information until I can check it for myself. In this case, I was all ready to search IEEE for new developments in solar design. As it turns out, that would have been a waste of time; you conveniently missed pointing out that you were referencing historical development instead of present research, and by doing so could have had me wasting several hours of my time on a wild goose chase.

I suppose you would have gotten a good laugh out of it at least.

As it is, I see now that your purpose is not to discuss the science, but to use any tactic to 'win' an argument. Due to that realization, I will in the future simply assume intellectual dishonesty unless your assertions are backed up with links t of solid supporting data.

At one time, the bulk of transistors were constructed from germanium instead of silicon. That has changed; silicon in most applications makes smaller, more efficient semiconductors. So if I say "transistors are made of silicon," you could certainly counter that germanium had been used. It doesn't change what modern transistors are made of, however, and to try to use historical use of germanium to discredit my statement would be intellectually dishonest.

TheRedneck

a reply to: TheRedneck

If one takes into account the cost of environmental regulations on fossil fuel plants, and the Federal subsidies on solar power in the US, then yes, the cost gap closes drastically. But that is not a technical concern; it is a political one. Without regulation or subsidies, coal is one of the cheapest plants to construct and solar photovoltaic one of the most expensive.

Wrong again. Your assertion is ludicrous.

Fossil fuels of all kinds get enormous subsidies, dwarfing the subsidies for renewable sources of any kind.

I would be happy to take away ALL subsidies, period. Coal and petroleum sourced energy would be squeezed out of the market so fast your head would swim.

Warning: here come some of those pesky facts again:

Global Subsidies Initiative: Fossil-fuel subsidies

In 2013, the International Energy Agency (IEA) estimates that consumer subsidies for fossil fuels amounted to US$548 billion, while subsidies for renewable energy amounted to US$121 billion. However, a simple comparison of subsidy expenditure does not reveal the extent to which renewable energy is disadvantaged. To understand the exact impact of this distorted playing field, it is necessary to explore how different kinds of subsidy can affect investment decisions in different ways in specific energy sectors.

World Energy Outlook

The IEA, within the framework of the World Energy Outlook, has been measuring fossil-fuel subsidies in a systematic and regular fashion for more than a decade. Its analysis is aimed at demonstrating the impact of fossil-fuel subsidy removal for energy markets, climate change and government budgets. The IEA’s latest estimates indicate that fossil-fuel consumption subsidies worldwide amounted to $493 billion in 2014, $39 billion down on the previous year, in part due to the drop in international energy prices, with subsidies to oil products representing over half of the total. Those subsidies were over four-times the value of subsidies to renewable energy.

I just had a look at the IEA database (it is available as an EXCEL spreadsheet from the above line). It doesn't show coal getting much subsidies at all, but then it doesn't include the USA, or Australia, or Europe at all. I'm guessing that is due to the refusal of the USA and Australia (and presumably Europe) to sign the Paris Agreement on subsidy reduction, so the IEA doesn't track them.

In any event, Australia's subsidies to fossil fuel industries is in the $4billion range ( Australian news report from 2014) in direct spending and tax breaks alone (there is more to subsidies than that). The Minerals Council of Australia (which demonstrably underestimates the fossil fuel subsidies and probably overestimates the renewables - that is their reason for existence after all) claims that subsidies to renewables run at about $2.8 billion (Lobbyist Policy Paper from 2015).

I'll take the (probably high) MCA figure for renewables (2.8 billion) and compare it to the audited report from the ODI/OCI ($4 billion)and note that fossil fuels got more in Australia.

Despite the discrepancy in subsidies between the two, Solar PV and Onshore Wind are already TODAY cost competitive with coal, the cheapest fossil fuel.

a reply to: TheRedneck

An incorrect assumption on my part. I assumed from your earlier post that someone was working with P-type substrates. I actually try to avoid semiconductor design, because I do not have ready access to the equipment required to implement my designs. Thus, it is easy for me to miss developments.

Ok, I cannot fathom what you think you are demonstrating here, other than your own disengenuousness.

You made a blanket statement that solar cells were made of n-doped silicon. I replied that your statement was true except for all the p-type solar cells that are out there.

It is simply untrue that all solar cells are n-type - I don't know what the heck you are arguing about? Are you claiming that research on p-type cells has ceased (how can you possibly know that) or that they are no longer manufactured (because they are certainly manufactured and marketed along side the more expensive n-type).

Practical n-type cells only came onto the market in the last few years, probably since 2012. p-Type cells still have a major place in the market.

I am not saying that n-type solar cells don't exist, I'm saying both types exist. And since, even though n-type is more efficient it is also more expensive. My suspicion is that p-type panels are more likely to be still 'the norm', and that probably will be the case for a while longer.

This report from 2015 ( N-type silicon solar cell technology: ready for take off? ) says that p-type was 90% of the market in 2015, and would still be over 60% of the market in 2024. I read that as p-Type being 'the norm' for quite a while.

Sheesh.

LG Neon 2 Black (monocrystaline n-type)

LG Mono X Plus (monocrystaline p-type)

a reply to: rnaa

You know, I have been desperately trying to have a conversation with you, maa, but it just don't seem to be working. So...

You win. You're right. You are the smartest person on the planet. Please write a paper sometime so others can share in your knowledge. Good night.

TheRedneck

a reply to: TheRedneck

Afterword:

I have been doing a continuing bit of research on the 'efficiency' question. In particular I was interested in comparing the efficiency of coal burning versus photovoltaic.

Redneck, your support for 'clean coal' begs the question, 'just how efficient is a coal fired plant and will 'clean coal' make a difference'? Of course every plant is different, and every coal source is different, but global averages CAN be computed and referenced (just as average global temperatures can be computed and referenced).

So, according to the World Coal Association: high efficiency, low emission (HELE) coal-fired power plants:

What can be achieved?
Moving the current average global efficiency rate of coal-fired power plants from 33% to 40% by deploying more advanced off-the-shelf technology could cut two gigatonnes of CO2 emissions now, while allowing affordable energy for economic development and poverty reduction.

Which is great. I absolutely support that, anything better and better is a good thing. Note that average means some are better, some are worse. How much better can they get?

Since the overwhelming majority of electricity in the world is produced by steam turbines, we can look at the Rankin Cycle to give us a theoretical upper bound. Turns out that upper bound is 47% for a reheat cycle plant and up to 60% in a combined cycle plant.

I still have big questions about how much it costs (in energy and byproduct) to produce this cleaner replacement for burning coal directly (because that is what we are talking about here; coal gasification has got to cost something and has got to produce byproducts) - TANSTAAFL.

Now for solar cells. After digging around some old text books and some online researchs, I think I have a reasonable handle on what I want to say here. For the purposes of this post, I found that once again, Wikipedia has an excellent summary (follow this link). Much of the following is a paraphrased summary of that article (so a summary of a summary isn't very detailed).

On the other hand, asking 'what is the efficiency of a PV cell' does not yield a straightforward answer, because there are several different kinds of efficiency that can be discussed. In thermodynamic terms, which would be the roughly equivalent measurement to the Rankin cycle computation above, is 68.7% (86% if solar radiation is whole sky, but it isn't of course).

There are a couple of other efficiency measures applied to PV cells. "Ultimate Efficiency" refers to the 'inertia', if you will (that is my choice of words) of the actual material the PV cell is made of. What I mean by 'inertia' here is that whatever material the cell is made of, a photon must have just the right amount of energy to generate an electron-hole pair. Too low and all the photons energy is converted to heat; too high and the excess energy is converted to heat. Traditional single junction PV cells have an ultimate efficiency of around 33%. Modern cells often have multiple junction materials and achieve much higher ultimate efficiencies.

Finally, "Quantum Efficiency" refers to the percentage of photons (of the right energy level) that are actually converted to electricity. This number is specifically dependent on the wavelength of the incident light and the construction of the cell itself. For example up to 10% efficiency can be lost due to reflection off the cell surface, so techniques can be used to minimize this effect.

There are other measures relevant to PV cell performance, maximum power point and fill factor, but I don't think I need them for this discussion.

Scientists have achieved 46% efficiency in the lab (Fraunholger ICE / Soltec), while commercial panels are still in the 20% range (I think I'm being generous). Notice however that the price per megawatt greatly favors the easier to manufacture less efficient cells over the super efficient cells.

The nut of the difference between your answer, Redneck and mine about 'what is the greatest problem with improving effeciency in PV cells today' is that as pointed out abobe, there are laboratory cells and there are commercially available cells. Your answer related to challenge in the lab (and was perfectly reasonable), while mine referred to installed commercial panels where no matter what the technology is, keeping them at a constant temperature is the key to maximizing their efficiency.

I content that my answer was also perfectly reasonable in that context. however, perhaps an even better one would have been "to lower the costs of the super efficient PV cells in the lab to make them commercially viable".

If PV cells at 20% efficiency are cost competitive with coal generations now (and it is) imagine what a 40% (or even 30%) efficient cell at the same cost as the current commercial stuff would do.