Is 85% the highest efficiency we can achieve with PV technology?

[russ_watters]

Where did I mention anything about photovoltaics? I pointed to one of these advancements earlier in the thread but if you want more University of Florida has some good articles. I'm not going to spend my time listing more just so you can blindly disregard them and refer to them as an "energy hoax".
http://www.fsec.ucf.edu/en/research/hydrogen/production.htm

Your "treehugger" link said the energy to split the hydrogen came from photovoltaics.

Now that link there has a number of widely different technologies, most of which just appear to be reforming hydrocarboms (which imo isn't very useful). But regardless, they are research projects. Those technologies have not been commercialized yet, as far as I know.

Scalability becomes less of an issue when photovoltaics are integrated into buildings and roads of urban areas and thermochemical or photochemical methods are used in non-rural areas.

No, it doesn't. Making smaller and more distributed generation with poor availability makes scaleability worse, not better. Instead of providing back-up power at the grid level, with distributed production of photovoltaics, you need full conventional redundancy. And that's in addition to the main meaning of "scaleability": economies of scale. Large installations are cheaper than small ones.

And no, were not. [charging at night]

?? When are you going to charge your car after driving home if not at night? In the winter, it is dark when I leave for work and dark when I get home.

Ok, show me the greatest "hoax" for this month?

You just posted it! But from the web, a google for "solar breakthrough" yields plenty of examples. Here's one from July: http://www.topix.com/energy/solar-energy/2009/07/portland-company-makes-breakthrough-in-solar-power

Now perhaps the word "hoax" is too strong - it is possible that some/many of these people are well-meaning inventor types. The important point, though, is that none of these breakthroughs have been successfully commercialized on a reasonable scale.

I'm sorry, your right. Obviously all the chemists that work at MIT are crackpots and all the work they do is just done to feed the minds of nutcases and treehuggers. MIT isn't even a real university anyway and only the dumbest professors on the planet work there.
http://web.mit.edu/newsoffice/2008/oxygen-0731.html

Where are you getting this stuff, Topher? Relax! I didn't say anything about MIT, much less that "all" chemist at MIT are crackpots! I questioned the one example you gave.

Topher, you made a mistake. That story (it's the same as the treehugger article) is not about a solar power breakthrough, it is about an electrolysis breakthrough. But the article (both it and the treehugger article are about the same thing) are both both so terribly written that they fooled you into thinking it was something it wasn't and led me to believe it is a crackpot claim. Might that guy have made an advancement in electrolysis? Sure. But the way he's promoting it - making a connection between it and solar power while trying out his Nobel acceptance speach - is highly questionable.

Every industrial electrolysis process out there that I know of uses a catalyst for splitting water to increase efficiency. I don't know of a single processes that does it at room temperature either. There is nothing that violates any law here, but if you want to see that for yourself you can download the paper that describes the work. And the significants of the process isn't that its just electrolysis, its that performs electrolysis at very high efficiencies at a lower cost and under ambient conditions. Something previously never accomplished before.

That's all well and good, and I'll acknowledge I'm not real up on how electrolysis is done commercially, but when a product hasn't hit the market yet and he's saying things like: "This is a major discovery with enormous implications for the future prosperity of humankind. The importance of [this] discovery cannot be overstated..." that shold make everyone's crackpot detector peg off the scale.

 

[russ_watters]

Yes, but: One, we would be trading one fuel (oil) that we don't have much of and little control over for one that we do (coal), and we end up funding maniacs abroad to get the oil.

Ok, I guess - I've just never heard someone claim that trading oil for coal was a good thing!

Two, switching to electric transportation is not a joule for joule switch in energy because of the efficiency gains (2 or 3:1)...

The efficiency gains are probably more on the order of 1.3:1. A gas car is about 30% efficient and a power plant is about 45% efficient. The electrical transportation, storage, and usage is altogether about 85% efficient. Mulitply that out and you get 30:38 or 1.3

...likewise it is not a 1:1 emissions switch either.

A coal plant is worse than a car in emissions.

Three, electric transportation makes the primary energy source inherently flexible in the future - maybe its coal (only half even now), maybe its natural gas, nuclear, whatever.

Once again, I've never heard someone talk about coal as if it were a viable option. Right now, increased power demand is increasing coal electricity and increasing emissions. That's a fact. Adding electric transportation only makes that situation worse, unless we make a change in how we make power.

 

[xxChrisxx]

A coal plant is worse than a car in emissions. Once again, I've never heard someone talk about coal as if it were a viable option. Right now, increased power demand is increasing coal electricity and increasing emissions. That's a fact. Adding electric transportation only makes that situation worse, unless we make a change in how we make power.

The only good thing about centralising power produciton to a coal plant over a car, is that coal plants can more effectively deal with emissions (CO2 scrubbing etc).

 

[Integral]

Ok, I guess - I've just never heard someone claim that trading oil for coal was a good thing!
The efficiency gains are probably more on the order of 1.3:1. A gas car is about 30% efficient and a power plant is about 45% efficient. The electrical transportation, storage, and usage is altogether about 85% efficient. Mulitply that out and you get 30:38 or 1.3 A coal plant is worse than a car in emissions. Once again, I've never heard someone talk about coal as if it were a viable option. Right now, increased power demand is increasing coal electricity and increasing emissions. That's a fact. Adding electric transportation only makes that situation worse, unless we make a change in how we make power.

In all reality coal may be a very viable alternative. But some R&D needs to be done. We need to learn to burn coal cleanly and efficiently. The emission stream can then be used to feed algae beds. The algae then becomes the source of your liquid fuel.

While there are arguments for large centralized power plants, they also have their disadvantages. For one, damage due to either natural disaster or terrorism can create major issues. I see advantages to a more distributed power net with each region contributing what ever the local resources can provide. Perhaps the desert SW could have large photovoltaic fields, coastal ares could provide energy from wave, tide and wind, others areas could grow algae or maybe tap geothermal sources. River turbines are being tested in the Hudson and other rivers. Putting all your eggs in one basket is never a good idea, along with the current coal, nucs and hydro we will need the alternative sources.

 

[vanesch]

In all reality coal may be a very viable alternative. But some R&D needs to be done. We need to learn to burn coal cleanly and efficiently. The emission stream can then be used to feed algae beds. The algae then becomes the source of your liquid fuel.

Yes, but in the end, you DID bring that CO2 in the atmosphere (when you use the fuel), although you used it twice, and so you divided the emissions per KWhr by about two.

Perhaps the desert SW could have large photovoltaic fields, coastal ares could provide energy from wave, tide and wind, others areas could grow algae or maybe tap geothermal sources.

In fact, if you have access to large amounts of direct sunlight such as in hot deserts, CSP is much cheaper and much more efficient than PV, and this will always be so, because mirror will always be cheaper than PV. Also, they can partly solve the problem of storage and of demand-following, at least day/night, because using molten salts, you can store heat during daytime, to use it during night-time. However, you need, eh, water (or you might use huge air heat exchangers, but that's more challenging) - so you may need to be not too far from a coast line. As a by-product, you can get (just as with nuclear) fresh water if you use seawater as cooling.

In fact, CSP in deserts is IMO, the only viable large-scale alternative to nuclear on a longer term. But, beware: it is going to be HUGE.

River turbines are being tested in the Hudson and other rivers. Putting all your eggs in one basket is never a good idea, along with the current coal, nucs and hydro we will need the alternative sources.

You can easily estimate an upper limit to hydro power: take all the rivers that verse their water directly into the ocean or sea. Take the height of their highest source of the drainage bassin, and take it's end flow rate. That will give you an upper bound on the maximum hydro power you could ever hope to extract from the drainage bassin. In fact, it is an overestimation, often by a factor of 2 or more, because not all of the flow rate finds its origin in the highest source, usually you have a gradual build-up.

 

[Integral]

Yes, but in the end, you DID bring that CO2 in the atmosphere (when you use the fuel), although you used it twice, and so you divided the emissions per KWhr by about two.

You are right once the fossil carbon is released the damage is done.

In fact, if you have access to large amounts of direct sunlight such as in hot deserts, CSP is much cheaper and much more efficient than PV, and this will always be so, because mirror will always be cheaper than PV. Also, they can partly solve the problem of storage and of demand-following, at least day/night, because using molten salts, you can store heat during daytime, to use it during night-time. However, you need, eh, water (or you might use huge air heat exchangers, but that's more challenging) - so you may need to be not too far from a coast line. As a by-product, you can get (just as with nuclear) fresh water if you use seawater as cooling.

In fact, CSP in deserts is IMO, the only viable large-scale alternative to nuclear on a longer term. But, beware: it is going to be HUGE.

I guess that is what I meant by R&D in my first sentence.

You can easily estimate an upper limit to hydro power: take all the rivers that verse their water directly into the ocean or sea. Take the height of their highest source of the drainage bassin, and take it's end flow rate. That will give you an upper bound on the maximum hydro power you could ever hope to extract from the drainage bassin. In fact, it is an overestimation, often by a factor of 2 or more, because not all of the flow rate finds its origin in the highest source, usually you have a gradual build-up.

What's your point? Are you implying that hydroelectric is a not meaningful power source?
Maybe you should do the calculation. A large percentage of the power generated in the Western US is hydroelectric. According to this http://hubpages.com/hub/facts-about-hydroelectric-energy" about 20% of the worlds power is hydroelectric.

 

[vanesch]

What's your point? Are you implying that hydroelectric is a not meaningful power source?
Maybe you should do the calculation. A large percentage of the power generated in the Western US is hydroelectric. According to this http://hubpages.com/hub/facts-about-hydroelectric-energy" about 20% of the worlds power is hydroelectric.

Some 20% of world's electric power now is hydro-electric. But if we are talking about electrical replacements of all our fossil-fuel usage, it is smaller. It is one of the finest ways of generating power (very flexible, clean, economical, and all that), but I wanted to say that it is a limited resource, and we used it already to a good extend. It is not much more stretchable (except maybe in countries like China and so) I think.

 

[Integral]

Guess you have not read or understood anything I have said. Never have I claimed anything was a "replacement" for anything. My point is we need to use what is available and not rely solely on the huge centralized power generation. Just for the record, I am not a big fan of large hydroelectric dams they are not nearly as eco friendly as commonly believed.

NYC is currently generating power with a http://www.verdantpower.com/what-initiative/" Many coastal cities may be able to benefit from similar systems.

 

[vanesch]

Guess you have not read or understood anything I have said. Never have I claimed anything was a "replacement" for anything.

Well, the point *is* that we'll need to get off eventually of oil, and we'll need off dirty coal. So we'll need a replacement for that, no ? I thought that was what the thread was about... In how much there is really something like "clean coal", I doubt it. There's maybe "less dirty" coal.

My point is we need to use what is available and not rely solely on the huge centralized power generation.

Of course, in as much as that is realistically and economically available, sure.

 

[vanesch]

NYC is currently generating power with a http://www.verdantpower.com/what-initiative/" Many coastal cities may be able to benefit from similar systems.

Over this two-year period, Verdant Power operated six full-scale turbines in array at the RITE Project, successfully demonstrating the Free Flow System as an efficient source of renewable energy with the following outcomes:
[ ... ]
80 megawatt hours of energy delivered to two end users;
[ ... ]

80 MWhr in 2 years, means 40 MWhr in 1 year means average power 40 MWhr / 8760 hrs = 4.6 KW.

Did I do that right ? We're talking about 4.6 KW average ?

 

[Integral]

80 MWhr in 2 years, means 40 MWhr in 1 year means average power 40 MWhr / 8760 hrs = 4.6 KW.

Did I do that right ? We're talking about 4.6 KW average ?

Ya, got to start somewhere!

 

[mheslep]

... Right now, increased power demand is increasing coal electricity and increasing emissions. That's a fact.

Perhaps you mean historically, but electrical demand clearly declined recently, and substantially.
http://online.wsj.com/article/SB125003563550224269.html

...On Friday, the nation's largest wholesale power market serving parts of 13 states east of the Rockies is expected to report that electricity demand fell 4.4% in the first half of the year...
Wholesale electricity -- power furnished to utilities and other big energy users -- cost an average of $40 a megawatt hour in the region, down from $66.40 a year earlier. The price declines in this market, which extends from Delaware to Michigan, come on top of a 2.7% drop in energy use in 2008 over 2007.

Part of that is no doubt due to the recession, but there's also apparently been some large investments in efficiency given the spiking oil prices last year and now the threat of pending carbon taxes.

Adding electric transportation only makes that situation worse, unless we make a change in how we make power.

It could if its done with no planning, but as you probably know some 10% of US electrical generation (~100GW) is idle overnight. Edit: That's enough to charge 200 million sedans w/ a 110 mile (25kWh) capacity ( 5 hours charge @ 5 kw)

 

[mheslep]

Scalability becomes less of an issue when photovoltaics are integrated into buildings and roads of urban areas and thermochemical or photochemical methods are used in non-rural areas.

No, it doesn't. Making smaller and more distributed generation with poor availability makes scaleability worse, not better. Instead of providing back-up power at the grid level, with distributed production of photovoltaics, you need full conventional redundancy. And that's in addition to the main meaning of "scaleability": economies of scale. ...

I'd say you both have a point here, depending on use. If PV's are deployed on roof tops to provide for only peak load, say for grocery store air conditioning in the middle of a sunny day, then Topher is correct, as they lessen the demands on the grid. To the degree PV's are deployed to handle base load without their own long term storage mechanism, then Russ is correct, as then the grid has to be there to match every PV deployment in the event of a four day blizzard.

 

[Ivan Seeking]

Yes, but in the end, you DID bring that CO2 in the atmosphere (when you use the fuel), although you used it twice, and so you divided the emissions per KWhr by about two.

Then we replace the coal with algae biomass: Loop closed.

 

[mheslep]

... A coal plant is worse than a car in emissions.

http://www.epa.gov/otaq/climate/420f05001.htm": 2.095 lbs CO2 from coal/ kWh (year 2000 plants)
http://www.eia.doe.gov/cneaf/electricity/page/co2_report/co2emiss.pdf" : 19.4 lbs CO2 / gallon gasoline

CO2 per mile (28 miles):
EV (4 miles/kWh - battery to wheel): 14.7 lbs. Including charging losses, 16.3 lbs.
ICE vehicle (28mpg): 19.4 lbs

The coal CO2 figures are net over all the old coal plants in the US. I understand the new supercritical coal plants do much better.

 

[mheslep]

Ok, I guess - I've just never heard someone claim that trading oil for coal was a good thing!

Not for the long term, and not all of the oil would replaced with coal of course. Replace just half of the oil with coal, the rest is natural gas, nuke, etc.

The efficiency gains are probably more on the order of 1.3:1. A gas car is about 30% efficient and a power plant is about 45% efficient. The electrical transportation, storage, and usage is altogether about 85% efficient. Multiply that out and you get 30:38 or 1.3 A

Ok, I was talking tank-to-wheel, your figure is the more inclusive well-to-wheel which I agree is the one we want at the moment. However these advocates (Tesla) still show well-to-wheel efficiency of EV's at least 2x or 3x better than even small ICE cars.
http://www.teslamotors.com/efficiency/well_to_wheel.php
They rightly include petroleum well-to-station distribution losses, and using a natural gas 52.5% electric source.

 

[mheslep]

..In fact, if you have access to large amounts of direct sunlight such as in hot deserts, CSP is much cheaper and much more efficient than PV, and this will always be so, because mirror will always be cheaper than PV. ...

Always is a very long time. I think both CSP and PV will win out in combination. You're right of course about the cost of mirrors, but consider:
1. PV's are http://thefraserdomain.typepad.com/energy/solarconcentrating_pv/" , making the use of high efficiency PV's affordable
2. Other work's being done to essentially 'waveguide' bandshifted http://www.technologyreview.com/energy/21066/"
3. Projects like the space based solar power plan for mirrors focused on PVs.
4. The upper limit on PV efficiency is apparently http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V51-3VTFJVJ-16&_user=3938616&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=980826264&_rerunOrigin=google&_acct=C000061828&_version=1&_urlVersion=0&_userid=3938616&md5=2a2c22990ac5eae6adc6c2c8a4a98501", far beyond what any thermal heat cycle can do.

The advantage you mention of overnight heat storage in thermal CSP will hold off PV for awhile, but not forever I suspect.

 

[gloo]

Your point in the OP is absolutely correct and it is what I've said in other places in this thread: cars are going to be powered primarily by gas for the forseeable future, whether people like it or not. Efficiency legislation and stop-gap technologies like plug-in hybrids will help, but they don't change that reality. While we should promote reseach, we should put the bulk of our efforts into solving now the problems that can be solved now. And that means... That hypothetical world is not a pipe dream, it is a reality in France today, a nuclear fueled country. Nuclear does satisfy their needs cheaply and cleanly and can satisfy ours if we choose to do it. Sadly, this is only going to happen when the economics overcome the politics for nuclear power here.

Wait Russ, so you are saying that part of the equation to get off of gas for cars will be the use of Nuclear to create electricity for cars? Did you mean to create electric power to feed into cars at plug in stations? I am pretty sure you don't mean making hydrogen off some kind of electrolysis (not efficient). You think nuclear is abundant enough to significantly replace coal and nat gas? Not challenging you (you are way more of an expert) - just trying to clarify.

 

[Ivan Seeking]

Your point in the OP is absolutely correct and it is what I've said in other places in this thread: cars are going to be powered primarily by gas for the forseeable future, whether people like it or not. Efficiency legislation and stop-gap technologies like plug-in hybrids will help, but they don't change that reality. While we should promote reseach, we should put the bulk of our efforts into solving now the problems that can be solved now. And that means... That hypothetical world is not a pipe dream, it is a reality in France today, a nuclear fueled country. Nuclear does satisfy their needs cheaply and cleanly and can satisfy ours if we choose to do it. Sadly, this is only going to happen when the economics overcome the politics for nuclear power here.

But we'll have better options before that happens.

 

[Ivan Seeking]

I wasn't sure if this was linked or not.
http://www.exxonmobil.com/corporate/files/news_pub_algae_factsheet.pdf

What is described as an exhaustive two-year review of all alternative fuel options landed Exxon on Algae, which I have been pushing for three years now, btw.

 

[mheslep]

Your point in the OP is absolutely correct and it is what I've said in other places in this thread: cars are going to be powered primarily by gas for the forseeable future, whether people like it or not. Efficiency legislation and stop-gap technologies like plug-in hybrids will help, but they don't change that reality. While we should promote reseach, we should put the bulk of our efforts into solving now the problems that can be solved now. And that means... That hypothetical world is not a pipe dream, it is a reality in France today, a nuclear fueled country. Nuclear does satisfy their needs cheaply and cleanly and can satisfy ours if we choose to do it. Sadly, this is only going to happen when the economics overcome the politics for nuclear power here.

Going to all nuclear electrical power in the US would do little by itself to remedy the oil dependency and import problem. Oil primarily goes to transportation in the US.

 

[mheslep]

Following up on CO2 emissions from EVs vs conventional vehicles in https://www.physicsforums.com/showpost.php?p=2309271&postcount=75", page 8.

 

[mheslep]

...
4. The upper limit on PV efficiency is apparently 85%, far beyond what any thermal heat cycle can do...

Working link:
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V51-3VTFJVJ-16&_user=3938616&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1046943350&_rerunOrigin=google&_acct=C000061828&_version=1&_urlVersion=0&_userid=3938616&md5=a8c43418a43c3d5ccadc277290468c9e