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Solar Power vs. Coal

He forgot that was the power and energy required to manufacture the cells. Now they need to be installed for another half that amount.
Why don't we just say that Solar PV panels are 10,000% efficient and it makes it so much easier?
"Mauried" wrote in message

On Wed, 17 May 2006 05:55:34 GMT, "JoeSP" wrote:
The Solar Resource
Could solar energy power the United States? To answer this question, let's compute how much land area would realistically be required to produce that much energy from Solar.
Then, for comparison, lets compare that to the land area we would need to mine coal to supply just our electricity (about 1/3 of our total energy usage - the rest being from oil and natural gas) over a period of fifty years (fifty years being roughly the time needed to make a complete transition to renewable energy sources).
The simple calculations done here are done explicitly, so that everyone may see the details and reproduce the results themselves.
Let BTU represent British Thermal Units, m2 represent square meters, kw represent kilowatts, hr represent hours, d represent days, yr represent years. Therefore, for example, the quantity "1 kilowatt hour per day per square meter" would be written as 1 kw-hr/d-m2. It is also handy to know that "kilo" means 1000 or 103 in exponential notation, one million is 106 , and one billion is 109.
Fact: The total energy usage of the US, including electricity, oil, natural gas, nuclear, and renewables, is currently approximately 1017 BTUs/year.
Let's assume that the efficiency of the solar collectors is 30% (nowadays a very realistic figure - recent photovoltaic cells are achieving 34% for example), and that we receive eight hours of sunlight per day at about 1 kilo-watt per square meter. Thus we can capture .3 kilowatts per square meter for eight hours, which means we can collect 8 hours x .3 kilowatts = 2.4 kw-hr/d-m2.
(Incidentally, an energy efficient home uses about 10 kw-hr/d or less of electricity. This implies that we would need 4 square meters or less of 30% efficient photovoltaic panels. This is much much less than the roof area of a home, so simply from this one can see that solar should be sufficient. But lets continue on anyways) Over the whole year we capture 365 d/yr x 2.4 kw-hr/d-m2 = 876 kw-hr/yr-m2.
Now, one square kilometer is equal to one million (106) square meters. By multiplying the figure above by one million and adjusting the exponents correctly, we find that over one square kilometer we capture 876 million kw-hr/yr-km2. If we know how to related BTUs and kilowatt-hours, then we can finish our calculation. One BTU (British Thermal Unit) is equal to 1055 Joules. A Joule is the amount of energy delivered by a 1 watt over one second. The term kilowatt-hour means the energy delivered by 1 kilowatt over 3600 seconds, or 3600 kilo-Joules. Dividing this by the factor 1055 Joules/BTU, we find that one kilowatt-hour is about 3.41 kilo-BTUs.
So, the yearly energy usage of the US, in kilo-watt hours, is 1017 BTUs divided by 3.41 kilo-BTUs, or 2.93 x 1013 kw-hr/yr.
Dividing this by 876 million kw-hr/yr-km2, we find that we need 3.34 x 104 km2. This is an area of 334 by 100 kilometers.
One square mile is equal to 2.58 square kilometers, so:
We find that we would need an area of 1.29 x 104 square miles, which is an area 100 miles by 129 miles, to completely power the US.
How does this compare to coal?
Facts: The average thickness of a coal seam is about 1 meter, the density of coal is about 1.1 gram per cubic centimeter, and the energy contained in one gram of coal is about 30 kilo-Joules/gram.
The average thickness of 1 meter means that we have about 1 cubic meter of coal per square meter of land area. One cubic meter is one million cubic centimeters. Therefore, the density of 1.1 gram per cubic centimeters implies that we have about 1.1 106 grams of coal per square meter of land area. Multiplying this by the energy density of 30 kilo-Joules/gram then implies that we obtain about 33 billion Joules per square meter of land area from coal.
Because a kilo-watt hour is 3600 kilo-Joules, dividing this into the previous figure means that coal yields about 9100 kilo-watt hours per square meter, or about 9100 million kilo-watt hours per square kilometer.
Dividing this into 1/3 of the US usage of 2.93 x 1013 kw-hr/yr (the 1/3 coming from the fact that we just consider electricity here), we find that we need to mine 1066 square kilometers per year. Dividing this by 2.58, we find that we must mine 413 square miles per year.
This in turn implies that over 50 years we must mine 20,670 square miles.
In conclusion, we find that over a fifty year time period, to produce just our electricity from coal, we must mine over twice the land area needed to completely power the US with solar alone!
Stolen from: NMSEA is a chapter of the American Solar Energy Society NM Solar Energy Association 1999

Unless Im missing something , if you are going to completely power the US from solar , then where does the power come from at night and when the sun isnt shining?

Solar Power vs. Coal

Perhaps we could build all our industries at the top of hills and our homes at the bottoms in the valleys.
This way we could use the solar power to drive ourselves to work and after the sun goes down ramp back home, recharging the batteries to power our homes from at nights.
"Boss. I can't come into work today as there is a big black cloud over my house"
"Anthony Matonak" wrote in message

Mauried wrote: ... How would you power high energy users like Aluminium Smelters that typically use hundreds of megawatts on a daily basis.
Perhaps smelters could be located in the desert and the miles of solar panels could be just outside of town. Then again, you could have massive solar power generators in the middle of the desert and miles of high voltage transmission wires leading into town where all the high energy industries reside.
Anthony

Solar Power vs. Coal

People didn't die because of a direct result of Chernobyl. People died because of stupidity and lies to control the mishap.
"Pooh Bear" wrote in message


JoeSP wrote:
"Anthony Matonak" wrote in message
One way to make nuclear safe is to put the reactor very far away. As far away as the Sun seems good to me. Why build another nuclear reactor when one is already available to you?
Anthony
That's a bit paranoid, considering that no one has ever died as a direct result of nuclear power generation.
Not heard of Chernobyl ?
Or in the USA http://www.google.com/search?hs=bGm&hl=en&lr=&client=opera&rls=en&q=sl1+nuclear+accident&btnG=Search
Graham

Solar Power vs. Coal

Solar Flare wrote:

People didn't die because of a direct result of Chernobyl

You mean if the accident hadn't happened Chernobyl would have been ok ?

. People died because of stupidity and lies to control the mishap.

Normal human behaviour.
Graham

Solar Power vs. Coal

Do I?
"Pooh Bear" wrote in message


Solar Flare wrote:
People didn't die because of a direct result of Chernobyl
You mean if the accident hadn't happened Chernobyl would have been ok ?
. People died because of stupidity and lies to control the mishap.
Normal human behaviour.
Graham

Solar Power vs. Coal

Solar Flare wrote:

Do I?

Do you what ? Top-post. Yes, it's poor etiquette.
Graham

Solar Power vs. Coal

"Pooh Bear" wrote in message


Solar Flare wrote:
People didn't die because of a direct result of Chernobyl
You mean if the accident hadn't happened Chernobyl would have been ok ?
. People died because of stupidity and lies to control the mishap.
Normal human behaviour.
Graham

And Hitler wouldn't have invaded Poland if someone hadn't invented the airplane and the tank. Get serious. Nuclear power is only dangerous when lots and lots of negligence is involved. Much less risky than driving a car or skiing down a hill.

Solar Power vs. Coal

wrote in message

Pooh Bear wrote: dezakin@usa.net wrote:
Gerald L R Stubbs wrote: The message <_n%ag.6086$Fi6.849@trndny03 from Nog contains these words:
Radiation bullshit. It's overrated.
Yup, that is why there are large areas of farming land in England, Scotland and Wales that are not allowed to produce for the market, as they are contaminated by Caesium isotopes that were released in the Ukraine.
Can't help that people that legislate against invisible demons.
Caesium may indeed be invisible ( in small amounts ) but it's very bad for you.

It may be dangerous at the proper dose, but certainly not at the levels found there. Because the public doesn't understand that a poison is defined by the dose, not by the name, those places are banned from food production for political reasons, not scientific.

Solar Power vs. Coal

JoeSP wrote:

"Pooh Bear" wrote in message
Solar Flare wrote:
People didn't die because of a direct result of Chernobyl
You mean if the accident hadn't happened Chernobyl would have been ok ?
. People died because of stupidity and lies to control the mishap.
Normal human behaviour.
Graham
And Hitler wouldn't have invaded Poland if someone hadn't invented the airplane and the tank. Get serious. Nuclear power is only dangerous when lots and lots of negligence is involved. Much less risky than driving a car or skiing down a hill.

In the case of Chernobyl you might say the reactor design was negligent.
In any case negligence is yet another example of normal human behaviour. It's to be expected to some degree sometimes. A reactor needs to have some tolerance for unanticipated events.
And if things go badly wrong with a reactor they tend to go really badly wrong.
Anyway, my point was that reactors *have* killed ppl, something that 'Solar Falre' appeared not to recognise.
Graham

Solar Power vs. Coal

Pooh Bear wrote: ....

And if things go badly wrong with a reactor they tend to go really badly wrong.

When things go wrong with solar PV panels they, well, they just sit there. Though, with a 25 year warranty there isn't much that can go wrong. I wonder if nuclear reactors come with a warranty.

Anyway, my point was that reactors *have* killed ppl, something that 'Solar Falre' appeared not to recognise.

One could argue that guns don't kill people, bullets do. With that kind of reasoning, it wasn't the nuclear power plant that killed people but rather mishandling of nuclear material. Even then it would have been OK if people had simply resisted the urge to breath, eat, drink or engage in any outside activities within the fallout plume.
Anthony

Solar Power vs. Coal

Anthony Matonak wrote:

When things go wrong with solar PV panels they, well, they just sit there. Though, with a 25 year warranty there isn't much that can go wrong.

Warranty periods have little to do with expected life. They are used by some as a way to imply long life. By putting such a lifetime it implies they might work for long enough to recover their cost.
Companies know that the vast majority will be scraped or or before the expiry of their warranty.

I wonder if nuclear reactors come with a warranty.

With regular maintainance, they do appear to last >25 years. -- Dave K MCSE.
MCSE = Minefield Consultant and Solitaire Expert.
Please note my email address changes periodically to avoid spam. It is always of the form: month-year@domain. Hitting reply will work for a couple of months only. Later set it manually.

Solar Power vs. Coal

On Fri, 19 May 2006 13:01:14 +0100, "Dave (from the UK)" wrote:

When things go wrong with solar PV panels they, well, they just sit there. Though, with a 25 year warranty there isn't much that can go wrong.
Warranty periods have little to do with expected life. They are used by some as a way to imply long life. By putting such a lifetime it implies they might work for long enough to recover their cost.
Companies know that the vast majority will be scraped or or before the expiry of their warranty.

Why would anyone scrap an old but fully functional solar panel ? Even 20 year old panels sell for good money here.

Solar Power vs. Coal

On Wed, 17 May 2006 11:37:59 -0400, "R.H. Allen" wrote:

JoeSP wrote: Let's assume that the efficiency of the solar collectors is 30% (nowadays a very realistic figure - recent photovoltaic cells are achieving 34% for example), and that we receive eight hours of sunlight per day at about 1 kilo-watt per square meter. Thus we can capture .3 kilowatts per square meter for eight hours, which means we can collect 8 hours x .3 kilowatts = 2.4 kw-hr/d-m2.
Those are some pretty liberal assumptions. For starters, the solar cells with efficiencies higher than 30% are tiny laboratory devices that cost an arm and a leg and haven't been made in quantities large enough to fill a jelly jar, let alone supply meaningful amounts of electricity. And I'm pretty sure that no location in the United States sees 8000 kWh/day insolation, at least not without two-axis tracking.

A while back..I ran into this presentation for renewable and PV.. ref http://cohesion.rice.edu/CentersAndInst/CNST/emplibrary/Hartley%2004May03%20NanoTechConf.ppt see slide 24.. Using the following premises.. 3,800 Billion kWh (US power usage in 2000) 6kWh/m^2/day in desert SW.. (flat plate tilted at latitude) http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/colorpdfs/208.PDF 25% in additional conversion(*) and transmission loses. (5000km HVDC), PV Panel efficiency 13% National HVDC grid. Larger conductors, no skin effect, reduced corona. and fewer synchronization problems.
Results.. 18,000 sq km.. solar array size.

====== Improvements ==========
Here are some updates, and improvements.. Better PV + trackers...
Commercial Sanyo HIT modules convert solar energy @ 17%. eff.. Dual axis tracker located in desert SW increases output upwards of 50%, annual average now 9 kWh/m^2...
refs: http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/colorpdfs/169.PDF "Annual average..dual axis tracking flat plate.. " http://www.sanyo.com/industrial/solar/index.cfm?productID=1232 "Sanyo.. HIP-200BA3"
Which reduces the surface area PV panels down to 9,176 sq. km..
Additionally, The trackers located in desert SW produce significantly more power in the summer time which does a fair job of matching increasing A/C loads..
refs.. . average daily solar radiation for June, July, Aug, Sept, Oct. http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/colorpdfs/162.PDF http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/colorpdfs/163.PDF http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/colorpdfs/164.PDF
http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/colorpdfs/165.PDF http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/colorpdfs/166.PDF
The apparent disadvantage of trackers is that they need to be spaced apart so they won't cast shadows each other. Assuming tracker space in a 1 to 6 ratio. This would expand the overall land use to (55,000 sq km).. However, spacing them out would have certain advantages.
1. Reduced impact on habitat allows multiple dual uses . Agriculture, homes, roads, etc.. 2. Elevated trackers (height @ central mounting point 7 to 10 meters) allows 99% of ground underneath them to be exposed to direct rainfall and remain as useful habitat. (Trackers would assume a near vertical position and rotate during storm.) 3. Trackers can orient themselves(on edge) in order to protect themselves from high winds, hail , and sand storms. (thus extending their lifespan. 4. Temperature reduction(extra shade) which improves habitat.. Photosynthesis peaks at 93 degrees F and ceases at 104 F.. Keeping the ground temps below 100F improves plant habitat.. 5. Easier maintenance.. Able to move vehicles in between tracked arrays.

===== Conservation and load displacement =====
US's Existing HVAC transmission system has an average ~12% energy loss rate. Loss is higher during summertime peaks ~25%, and is some what lower at nighttime %9 and in the winter 5%.. (I^2R applies)
(Extending HVDC lines closer into the users, and skipping 500/230 KVAC transmission lines, and delivering HVDC directly to 1st set of HV step down substations would eliminate much of HVAC transmission and initial transformer losses... recovering as much as ~50% of current losses).
------
25 to 35% of our electricity consumption is needlessly wasted.
A little bit of conservation goes a long way. Upwards of 2% can be conserved by building Cable and Sat (200 mil) decoders with a simple circuit so they power down when not in use.. (And wake up on a schedule in order to fetch program guide and record tv programs).
Similar always on problem applies to most electronic devices.. Many are small, but significant 24x7 energy wasters.. Large wall warts is one clue.. Equipment cases warm to the touch is another..
Retire existing CRT, Plasma, and Projection units using hi intensity light sources. And replace them with direct view LCD and/or Projection units using high intensity LED back lights.. (7 to 10% national energy savings.).
More CFL & LED usage (10 to 20% savings.) More efficient A/C, and heat pumps. More efficient refrigerator/freezers.. Computers designed for low energy consumption. More eff power supplies. better processors & video cards. Front loading washers... (1/3 hot water consumption, longer lasting clothes.) Roof or side yard mounted solar hot water heaters. Promote Solar heating Subsidized insulation improvements.
In order to retire some of the old energy hog appliances, the poor and those living in subsidized housing would get them swapped out for free.
-----
15 to 20% of electricity is consumed by the OTHER ENERGY industries.. Oil, NG, Coal... Gas stations, tanker trucks, refineries, pipelines, pumping stations, wells casings, drilling rigs, super tankers, 400 ton trucks, drag lines, shovels, coal trains, railroad tracks, construction of power plants, etc..
A lot of this overhead, pollution, and load goes away, when these industries shrink to less than 1/10th of their current size.
-----
Replacing 80 to 90% of ICE oil and gasoline infrastructure.
Modern EV's using Li-ion tech are roughly 15x more efficient than current conventional autos in combination with the energy losses in the current oil and gasoline infrastructure. (Efficiency of Oil & Gas infrastruction is decreasing with each passing year.. More and more energy is being consumed to recover ever smaller quantities of Oil and NG).
Diverting 15% of our (2000) electricity generation would propel 150 Million EV's for a distance of 19,000 miles..
(Uses 200 wh/mile as a baseline...current Li-ion designs ~100wh/mile).
Household renewable energy production, paired with a EV, would have significant advantages.
======= Lifestyle changes =======
Modern lifestyles are energy intensive.. The more people living a modern lifestyle... The more difficult the problem is to solve.
Abandon the every expanding growth mentality.. GW is visible side effect of ever expanding population/lifestyle and non-renewable energy usage. Either solve the GW/pop problem, or GW will solve it for us with a massive ELE.
Limit free trade in all aspects. That system works against countries who sacrificed resources, and lowest cost in the name of protecting society andor the commons. ref: "Tragedy of the Commons Restated" http://dieoff.org/page109.htm
Increase tele-commuting.. Reduce or stop importing workers. Secure the boarders.. deport the un-invited..
Limit population growth to sustainable levels.. (This already occurred in native pop..)

===== Energy storage & load leveling =====
Use the EV batteries as Grid storage.
This section is dependant on Toshiba's recent claim of a new Li-ION bat tech operating for 50K C/D cycles.
High capacity @home/work charging systems for EV's would also have a intelligent inverter function. They would capable of providing energy back into grid when directed to do so. Note: Not everybody will need the EV's 300 Mile range each every day, participating EV customers would get free energy in exchange.. .
US grid could operate off of EV bats for upwards of two days without an external energy source. This feature would be handy after a hurricane swings on through and disrupts the local grid.
++ Undo some daytime peak demand reduction efforts.
You want the load to be present when PV/widn is at max production. Intelligent thermostats under radio control could receive signals from central energy ops. and alter heating/cooling schedule to match avail power.
Typical 50 gal HW heater stores 10 to 15 kWh of Heat.. (Use mixing values, extra insulation, smart controllers to help manage those loads) Solar HW is much better than electric HW.. Heat pump HW heaters for warmer climates with solar access.
++
Install PV trackers over widest possible areas.. Florida, Texas, Desert SW, Islands off of California.. Maximize PV production over the widest possible time frame.
++
Collapse mainland time zones from 4 to 2 in order to shift Commercial energy usage to be in sync with PV energy production. East cost would wake up later, West coast would wake up earlier.


NREL has more realistic discussions at http://www.nrel.gov/ncpv/land_faq.html and http://www.nrel.gov/docs/fy04osti/35097.pdf.
That said, the conclusion reached by this particular type of calculation is fairly robust to changes in the assumptions, so the end result -- even with the crazy starting assumptions -- is actually not too far off the mark.
Then again, as others have pointed out, using nothing but PV to meet our electrical needs is impractical. For that matter, using nothing but


We wouldn't, Hydro (8%) and pumped storage (2%)would still be around..
We would still need a major expansion of wind power.. until it matches PV capabilities..
We would hang onto the combined cycle NG plants and adjust turbines to use various mixtures of CH4 and H2,.. (H2 andor Ch4would be manufactured by during periods of surplus renewable power generation and stored in depleted NG wells.) ..
Operate a limited number of N-plants until we deploy enough renewable and load leveling capacity.

coal, wind, nuclear, or any other single source would be impractical too. It would be technologically feasible, but not practical.

Note: At some point we will need to undo the effects of our past CO2 emissions before the ice caps melt. (Sooner rather than later). This will require using surplus renewable energy in order to improve the efficiency of atmospheric CO2 removal..

Solar Power vs. Coal

Jens Kr. KirkebÝ wrote:

On Fri, 19 May 2006 13:01:14 +0100, "Dave (from the UK)" see-my-signature@southminster-branch-line.org.uk> wrote:
When things go wrong with solar PV panels they, well, they just sit there. Though, with a 25 year warranty there isn't much that can go wrong. Warranty periods have little to do with expected life. They are used by some as a way to imply long life. By putting such a lifetime it implies they might work for long enough to recover their cost.
Companies know that the vast majority will be scraped or or before the expiry of their warranty.
Why would anyone scrap an old but fully functional solar panel ? Even 20 year old panels sell for good money here.

Indeed, one of the major obstacles to the development of PV module recycling technology has been finding discarded PV modules to recycle....

Solar Power vs. Coal

"Pooh Bear" wrote in message

JoeSP wrote:
"Pooh Bear" wrote in message
Solar Flare wrote:
People didn't die because of a direct result of Chernobyl
You mean if the accident hadn't happened Chernobyl would have been ok ?
. People died because of stupidity and lies to control the mishap.
Normal human behaviour.
Graham
And Hitler wouldn't have invaded Poland if someone hadn't invented the airplane and the tank. Get serious. Nuclear power is only dangerous when lots and lots of negligence is involved. Much less risky than driving a car or skiing down a hill.
In the case of Chernobyl you might say the reactor design was negligent.

The design was fine, but the people operating it ignored a large number of rules. In Soviet society at the time, there were so many rules and regulations for everything, that people were conditioned to ignore them most of the time in order to survive.


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