What's the Best Power Source?

Ultimately it has to be Solar I think.. It is the underlying source of energy here on Earth, and supplies an abundant amount...The question is how efficiently we use it...Fossil fuels are stored solar energy, we can use them, but eventually there becomes a question of Global Atmospheric balance of gases, many would say we are already at a critical point...The move to nuclear would alleviate the atmospheric imbalance, at least from the human standpoint...But eventually this too becomes unsustainable...Solar to electric direct conversion seems the ultimate goal then...Solar encompasses both light, in many wave lengths, and heat...We already have solar cell prototypes that show promise, but I think still a long way to go...Our path is a difficult one because each step must be economically feasible..and this is only possible with a mature technology...So development of these new technologies are against the grain of society, costing money rather than making it...So we zig zag our way toward a sustainable future, with all sorts of political maneuvering and social outrage..it's a real hoot...

Everyone who is able bodied and unemployed could be used to spin giant hamster like wheels to generate power. We'll feed them a soylent green like substance to maintain the calorie burn. We'll take care of unemployment, obesity, and our power needs all in one step.

What do you think the average hp output per human would be, per hour, over an 8 hr workday??

According to Marks' Standard Handbook for Mechanical Engineers 11th Edition, "A healthy well-fed laborer over the course of an 8-hour day can sustain an average output of about 75 watts."

I/10hp, I put out more than that sleeping...

Aren't you just the self proclaimed expert on everything these days

Bring it!

All we need is happy dreams.

Oops.." Their gadget, called a biofuel cell, uses glucose and oxygen at concentrations found in the body to generate electricity."

"Matrix" Human Battery Now A Reality 2011

http://www.youtube.com/watch?v=lPOASjm02as&feature=related

I agree that solar is, ultimately, the best way to supply out energy needs for the future, but there are certain problems that need to be discussed.

First of all is the sad fact that solar energy is only available during daylight hours and when there are no clouds blocking out the sun. As yet we have to truly viable method of storing excess energy, though efforts are continually going forward and someone may come up with something that actually works tomorrow.

Second is the fact that efficiency is deplorable. For every watt of sunlight which actually strikes this ball of rock, we can convert maybe 10% into usable energy. Now, before you all cry for my crucifixion, lets take a look at that.

First of all, the very best we've been able to get out of very high priced single P-N junction photo-voltaic cells is about 35%. Multi-layer cells might approach 85%, but that seems an awfully long way off and those are even costlier.

But, far more important is the simple fact that, while the solar flux at Earth orbit is around 1.366KW/m², by the time it gets to the surface, it's attenuated to about 180 watts per square. And as already mentioned, that's only when the sun is actually shining.

No, the only truly viable way to make solar work is to put our solar power systems up where the sun is always shining. Which is to say, in space. This side-steps all of the problems of Earth surface solar. It is a fairly simple matter to beam the energy down to the surface via microwave or LASER, at reasonable levels of efficiency, and the energy is then easily used via the existing infrastructure, or used to crack sea water into hydrogen to use as a fuel for long distance surface or air transport.

Of course there are those who will scream about the cost of the things, but the truth is that if we build 'em in space using space-based materials, such as moon rock and asteroids, they will become cheaper as we build more of them and we will more be buying capacity than actual powersats, thus creating whole new industries in space. And besides, a planetary surface is a lousy place for an industrial civilization.

Energy can be effectively stored by converting sunlight to hydrogen...You have probably seen the prototypes...In any case we have enough time to develop these technologies, by deploying nuclear technology that is available now, or in near term..

http://pubs.acs.org/cen/news/87/i32/8732notw.html

http://gcep.stanford.edu/research/factsheets/biohydrogen_generation.html

http://www.dailytech.com/Use+MeltdownProof+Modular+Nuclear+Reactors+Says+Top+US+Scientist/article23522.htm

Solar Energy is limited. Storage methods of day time solar energy is expensive by any route hydrogen or battery. Bio-energy has limited scope as land area required cannot be provided.I think Geo-thermal is best source and abundant for 24x365 hrs. Efforts on this direction is not as much as in Solar. Confidence on Solar is reducing, as research projections have failed to meet the target dates by years. Since Geo-thermal is not visible like sun rays, so political decision makers think of Solar only.

"The total solar energy absorbed by Earth's atmosphere, oceans and land masses is approximately 3,850,000 exajoules (EJ) per year.^[7] In 2002, this was more energy in one hour than the world used in one year.^[12][13] Photosynthesis captures approximately 3,000 EJ per year in biomass.^[9] The amount of solar energy reaching the surface of the planet is so vast that in one year it is about twice as much as will ever be obtained from all of the Earth's non-renewable resources of coal, oil, natural gas, and mined uranium combined.^[14]"

^{http://en.wikipedia.org/wiki/Solar_energy}

SolarEagle-

Your figures for energy "absorbed by Earth's atmosphere" have absolutely nothing to do with how much of that energy is actually available for use. At the earth's surface, the solar insolation is on the order of 1 W/m² (http://en.wikipedia.org/wiki/Insolation). That is the energy you have to work with. How many joules that works out to will depend on how many hours of sunlight you have available wherever you happen to live.

I believe your 1 W/m² is off by a factor of 1000 or else my cheap eBay solar panels that put out about 3 W/ft² are running in over unity mode.

I would have thought you would know CW well enough by now, to know that's a typo.

You are right- missed a zero. it should be about 10 W/m², which works out to something like 32.5 MJ/m² in one hour on average. At the equator. Your results will vary depending on location.

And another mistake! Missing the k. Boy, I need to do more proff reading before I submit a post! 10kW/m².

Mr. Warner my friend, I think your numbers might be off just a bit there. The total solar flux at Earth orbit is 1.366kw/m², so 10kw/m² solar flux at the surface has to be off by a couple of orders of magnitude. The best numbers I can find put it around 180 watts per square.

http://en.wikipedia.org/wiki/The_Geysers

Geyserville CA has about 100 KW of geyser steam generation in production now. However that production pales in comparison to that of Bonneville Dam along the Columbia river separating Oregon and Washington.

Even larger systems are the 300 MW combined solar PV systems in San Diego county, connected to the grid and installed on hundreds of home and business rooftops. While this 300 MW solar system only produces daytime power, that is when demand is the highest, and SDG&E is producing as much power as they can, importing the rest on 3 each 1,000 to 1,200 MW power lines extending from Arizona and Mexico. Another 1,500 MW is available from a power line heading north into Orange County, but normally the power is flowing North into LA and Orange counties, not south into San Diego.

Pumped Storage is used in several areas of California. The largest system that I know about is Shaver Lake and Huntington Lake project, where they can use 1,200 MW to pump water from Shaver Lake at 5,500' elevation to Huntington Lake around 6,500' elevation. During the day, up to 900 MW can be generated from that same water. Big Creek is one of SCE's largest and oldest large hydro power projects, dating back to installation of generators in 1914 with 2,000' of total head - nearly 4,000' if you include power plants #1 and #2 from Huntington Lake to the canyon 4,000 feet below.

1 The sun is shining on at least 50% of the earth for 24 hours a day. Storing energy is not the answer, building web like global distribution infrastructure is.

2 I'm not sure where you got your surface insolation data from. You are grossly wrong. There are frequent daily episodes of sunlight energy at the surface of over 1000 watts per square meter in populated areas. I can show you PV array data where we have harvested over 900 watts per square meter for over three continuous hours, including all inverter, panel and equipment and transmission derates.

3. Trying to pin your hopes for energy nirvana on any single technology is poor business. poor ethics, poor environmentalism. Many technologies, like wind, water, wave, geo, nuclear can be utilized to build solid solutions, and should be. Integrated systems are more robust and logical, requiring less capital to program.

4 I agree that trumping any one of these is efficiency and conservation. Efficiency happens when you pay for energy and it's resultant contribution to environmental degradation. Right now, there is no political will to enforce clean energy regulations. Conservation happens when it's cheaper to conserve than to pay for properly priced energy.

I'm sorry if I was misleading. My response #2 refers to insolation, not production.I was incorrect about harvest, currently a typical harvest rate is about 16% of insolation, which, as has been suggested, is easy to represent as "inefficient". We have documented many periods of insolation that are in excess of 1000 Watts per square meter, and in some areas, over 1250 watts per square meter. As solar eagle has pointed out, the ability to produce massive amounts of power is, even today, easily accomplished with current efficiencies. Is it worth it to achieve gains in w.s.m. for PV module architecture? Certainly, but to deny the prospect of substantial power production is not advisable either. Again, I apologize for the error.

Nearly all of your figures are way off, or don't have dynamic trend change provided for...Therefore your conclusions are dismissible...

SolarEagle-

The only numbers that are mine are the numbers for the real estate required, which were derived from local (i.e., Panama) actual experience- yes, these numbers would be different for other regions of the world. However, the rest of the data has been developed and published elsewhere- follow the links. If you have better substantiated numbers, I would like to see them.

Furthermore, the only conclusions I have offered is that continued growth in power demand is not sustainable, and that the most viable approach is to revise the way we use what energy we have available. If these conclusions are dismissible, I assume you have figures to support another approach?

No offense was meant, but you are taking data out of context and presenting only one side of the argument....This then leads to an absurd conclusion...What about improvement of efficiencies, you say nothing, even though we are making great strides...You haven't accounted for the improvement of efficiency in using energy as a limiting factor in increasing power production...Nor the improving efficiency curve in production of energy...Your using yesterdays statistics to predict tomorrows reality, it doesn't work...and what about overcapacity, you say nothing of the overcapacity that exists today...I could go on and on, you need to do more balanced research...but thank you for your interest and contribution...

I am encouraged by the performance of the world's first commercially available Low Energy Nuclear Reactor (LENR), available now from Rossi's Leonardo Corporation in Italy.

The first buyer of 13 Megawatts of this product is in the USA, and delivery is 4 months.

At this time, they are thermal units producing steam. A steam turbine would be needed to produce electricity. These power plants produce no toxic residue, and the Nickel and hydrogen fuel is cheap. They are advertising reactor swap out every six months.

These units could be set up in towns, or neighbor hoods in larger cities, and distributed through out to homes. They could be tied to the grid to furnish power when an excess is available. Eventually, maybe no grid would be needed at all! (of course, the large power plants will continue to be used for the next hundred years or so).

Those units are not yet proven. As such, they are spin.

The limitations of non-hydro "renewables" for baseload generation are clear, but seldom acknowledged by the zealots who push for their deployment. Wind is mostly available at night, when power is cheap. Solar might eventually be as big a player as wind is now, but that will take a long time. Both wind and solar are intermittent and connecting them to the grid is difficult.

Hydro is maxed out, and geothermal sites are scarce too.

Nuclear, after Fukushima, has a political problem. The $10B reactor designs prohibitively expensive, and the wet cooling of nuclear is a big water waste that will not be tolerated as fresh water supplies dry up. Hot fusion continues to disappoint despite the huge amount being spent on it. Cold fusion ...

The shale gas boom looks to be a bubble: Producing gas at $8 and selling for $3 is not going to last.

So that leaves coal. The technology for cleaning up coal needs to be developed, but instead the money is being spent on "clean coal" propaganda as if it already exists. Ash ponds, mercury, SOx, CO2, fly ash, and water waste from wet cooling are problems that coal has ignored for many years, and now the public has reached the limit of its toleration. But since baseload generation depends on coal, it won't be replaced anytime soon. I've heard the arguments that wide enough deployment of wind and solar will substitute reliably for coal, but I'm not convinced. And how do we get to that wide deployment when nobody wants expensive and intermittent power and the transmission lines don't exist?

So that's where we are. Where we are going is probably small modular fast reactors and a lot more waste heat power harvesting. Also hybrid power systems to deploy wind and solar to clean up coal emissions.

Bloom Box has been missed out in the debate. Another important power source which is clean and has potential to reuse all the spent Nuclear fuel is Thorium breeding molten salt reactor. Fast breeder reactors too are a good source of power. Solar energy may be the future but for the next 20 years it will be sustained on government grants and subsidies.

no idea why you think $12 per watt could be considered best?

http://www.wired.com/epicenter/2011/01/bloom-box-cost/

if the fuel source is methane a regular ol turbine is hard to beat

What everyone is completely ignoring here is that while surface based energy technologies are sharply limited, space based technologies are not.

Think about it people! Solar energy is streaming by at a rate of 1.366Kw/m², 50% conversion efficiency is completely reasonable, and microwave transmission efficiency has a theoretical limit of 90%, so I think that 75% is a reasonable target. Now lets run those numbers, shall we?

A square kilometer powersat would intercept 1.366 gigawatts of solar energy. At 50% conversion efficiency that gives us 683 megawatts. At 75% microwave transmission efficiency, this gives us a bit more than 512 megawatts delivered to the electrical grid, per square click of powersat.

The total installed capacity in the US, according to EIA.gov, is on the very near order a terawatt. So, for powersats to completely take up the load, we would need 2000 square kilometers of collection area, which works out to round powersat a little over 50 kilometers in diameter, or a square one about 45 kilometers on a side.

Now, there is also the matter of the rectennae. The latest information I can find suggests that a rectenna of only a few square kilometers would be more than enough for any city in the world. We could certainly put rectennae in the middle of otherwise useless land, such as the worlds deserts. And, since they don't significantly interrupt the sunlight, unlike surface based solar arrays, we could conceivably put them over anything from roads to farm lands.

Now obviously, the first ones we build would be fantasticly expensive but, assuming space based manufacturing and space based raw materials, each follow-on satellite would be less costly as we increase our orbital capacity. This would have the added benefit of creating whole new industries and technologies, would have incalculable economic impact.

We hear all the time that we have strictly limited resources, but in space our resources of both energy and raw materials are virtually unlimited. The sole limiting factor seems to be our will to go get them.

Wouldn't that burn up the ozone?? Wouldn't that cook airplanes that flew into the transmission beam, and, gulp, birds??

If we were pumping say 10Gw into a beam a couple of kilometers across, the power density wouldn't be all that severe. Not at all like flying in front of a radar. I might add that in 13 years of sea duty as a signalman on the bridge, I never once saw a seagull get cooked. I suppose rectenna sites might have to be listed on aeronautical charts as navigation hazards, but I have to wonder... Anybody got a calculation on the power density of such a beam?

Okay, I just ran the calculation. 10Gw into a beam 10Km across works out to a bit less than 127w/m², which is less than the solar flux at Earth surface. Seems unlikely that'd be enough to cook anything.

At such a low power per m2, you might as well use a simple solar panel on the surface...

A project along those lines

http://www.msnbc.msn.com/id/30198977/ns/technology_and_science-space/t/pge-makes-deal-space-solar-power/#.Tu1vKs3T0lg

was shelved, not long ago

just because a thing can be done, doesn't make it a good idea or economically feasible today

As I said previously, the first ones would be fantasticly expensive, yes. And, if we assume that we are going to build 'em here on the surface and then send them up on rockets, they will stay fantasticly expensive.

But! If we build them from space based materials, using space based energy, then each and every following one becomes less expensive as we build capacity. Plus, in free-fall, we can build the things as big as we want without having to bow to gravity. Economy of scale!

As I have said over and over again, everything we need to do this, to make space a paying proposition, is off-the-shelf technology. What seems to be lacking is the will.

Gee, I wonder why?

Unless the beam energy density is much higher (1000's) of time than the sun's energy already falling on us, you might as well forgo the satellite and use simple solar panels because your receiving antennae will be huge!

Also, collecting and converting these GW of energy from your collector will require electrical conductors and power converters that are not feasible this century. Do you intend to use plasma conduits?

Anything that is space related will be too expensive for the next hundred of years.

We have to bet on a diversity of sources that have advantages of their own and apply them where they "shine"

Solar and wind are interesting for remote communities to save on diesel generators but are not for large population centers. Cities will continue to use hydro, nuclear, and coal produced electricity for a long time.

I hope that some new nuclear reactors will become functional.

I hope that geothermal will prosper.

I hope that we will insulate our house properly, stop leaving lights on all night, stop waisting energy so that the current sources will slowly be replaced by better alternatives as the technology improves.

Sorry for crashing your satellite but we need feasible dreams.

Regards,

Marco

I thought about that when I crunched the numbers, but! Rectenna farms have certain large advantages over solar plants, as I've already mentioned.

To reiterate. A rectenna does not block out the sun, so it can be situated virtually anywhere. I rectenna will be putting out power 24/7, day and night, rain or shine. As opposed to the solar panel farm which will totally block out the sun for anything underneath it and only deliver power during daylight hours and only if not overcast, snowing or raining. Thus a city could use a rectenna farm as it's sole power supply. The same could not be said for a solar panel farm.

As for collecting, converting and distributing all those gigawatts, we are already doing this with the existing electrical grid. Converting from DC at the rectenna to AC for transmission is trivial.

As to the remark that anything space related will be too expensive for the next century, I seem to recall that similar remarks were made at the end of WWII regarding men in space at all. For that matter, the same sorts of things were said about automobiles and airplanes at the turn of the last century.

I will say this again. Everything I have suggested could be done with off-the-shelf technology, circa Friday afternoon. All that is lacking is the will, and I for one am tired of hearing how "it can't be done!" People like you have been saying the same thing since the dawn of time, and then scratching your heads when people who say "Why not?" go out and do it.

You say that these "dreams' are not feasible. I say, get the hell outta the way.

You seem to forget that the earth turns on itself. If your satellite is geostationary, it will be shaded by the earth each day unless you place it extremely far. This is an enormous difficulty.

You could place it over the poles with the receivers underneath but how would then bring the power from the receiver to the consumption centers?

You wrote:

As for collecting, converting and distributing all those gigawatts, we are already doing this with the existing electrical grid. Converting from DC at the rectenna to AC for transmission is trivial.

You obviously have no idea of the challenges involved when so much power is at play. The transformation system would be as large as your collectors. There isn't enough energy and material available on earth to build this in a limited time frame. Forget about using space material. Capturing the asteroids, refining them to the required purity is not possible on this scale this century.

I still maintain that there are better places to invest money to save the planet...

First of all, when a satellite is in a geosynchronous or geostationary orbit it's path only very rarely takes it through the Earth's shadow, much as we only very rarely get a lunar or solar eclipse. Also, by definition, the above mentioned orbits are at an altitude of 35,784km msl, which is pretty far, don't you think?

As to handling the currents involved, remember that the world's electrical grid already handles some 30,000 terawatt hours per year, so plugging in the output from rectenna farms would a very simple matter. Further, a quick internet perusal of the subject of DC to AC inverters shows that this is also a very simple and well understood engineering problem. The only way that these might pose a problem is if we were using a single, gigantic rectenna farm to receive and distribute all of the output from a single, gigantic orbiting powersat, which we wouldn't do any more than we use a single, gigantic generating station to provide power to the entire planet.

Regarding the use of space based materials, I refer you to Dr. Gerard K. O'Neil's seminal work, "The High Frontier", which contains an excellent discussion of the subject. To refine space based materials, it's a very simple matter of pumping in enough concentrated solar energy to cause the raw materials to fall apart into their component elements, in pretty much the same manner as we refine raw materials here at the Earth's surface. However, in space we have the added advantages of not having to deal with atmospheric contamination, gravity and it's attendant effect, convection, and we have abundant and essentially free solar energy.

As for going to get such materials, it takes less energy to scrape materials off the surface of the moon, which has usable fractions of lots of valuable materials, such as oxygen, iron, aluminum and titanium to name but a very few, or to go out and collect asteroids and bring them back to our industrial stations in near-Earth space, than it takes to dig them out of the ground and use them down here, or worse, hoist them up to space. Remember, in space, we don't have to bow to gravity, so it's often just a matter of giving an asteroid a precisely calculated little nudge and then waiting for it to show up at the appropriate orbit.

As for saving the planet, consider this. If we, as a species, were to transfer the lion's share of our industrial activities and population off-planet, the planet would heal itself fairly rapidly. Leave a small, care-taker population on the surface to manage things and the effects of our industrial civilization would be swallowed up and disappear quite automatically over the course of a couple of centuries. No doubt you would be one of those who would prefer to remain behind.

What about its effect on birds. In India sparrows have virtually disappeared from cities after the intruduction of Microwave towers for beaming Cell phone signals.

That is a coincidence in that location.

I have had to deal with the influx of ravenous cockatoos with the proliferation of cell towers.

The choice should be based on initial cost,reliability,pollution,danger to mankind etc. Nuclear is unsafe but if located far away from townships with adequate safety measures it should be considered. Next is wind and solar with compressed air as standby which could be used to drive air-motors.

The smartest and cheapest way to address growing demand is to demand less.

There are many discretionary, energy hungry human activities that yield so little benefit. Omitting these from our lives would measurably reduce the demand for energy.

One activity that always comes to mind for me is clothes ironing.

What a phenomenally mindless, pointless waste of both electrical energy and human output.

At 1000W minimum per appliance in nearly every electrified household on the planet for who knows how many hours per day it adds up.

Lets save the planet one crease at a time.

Tell that to the guy who's boss demands that he show up for work in neatly pressed clothing.

That would be an unethical demand.

Hardly. It's called "Dress Code" and virtually every business has one. We certainly had one in the Navy, and believe me, it included neatly pressed uniforms.

I have no doubt that these demands exist.

The practical or beneficial purpose of ironing clothes is beyond my understanding.

Is there any real reason why the need for ironing couldn't be omitted from a dress code? What would happen if it was omitted?

Oh possibly the approximately 4.7% of people on the planet that consume around 25% of the energy, would use less.

^{_{Though it does seem they are still far away from considering the outcomes of hogging it all.}}

It's a hold over, from before permanent press

dry cleaning isn't exactly environmentally friendly either...

the notion of dress code is about conformity to certain expectations, is there really any reason to wear a 3 piece suit, when it's the middle of summer?

what about ties? what possible purpose does a tie serve?

Yeah, that'll work...lol

Perfect!!!

Give it an hour and it will look the same as a pressed shirt after an hour of wear.

What can I say? "It's a look".

Not much thought about large scale energy, only best save it first?

However, I did think of trying a Stirling engine over water (e.g. sea)
with large sun reflectors for the heating. Units would be very low maintenance
and, spread around the globe, produce power 24 hours a day, from somewhere.

Even large inland ponds / waterways should work? Which started the idea.

What do the members think of my idea please? The idea is to produce power/
(electricity) from many low cost units powered by natural resources, or would
just a normal windmill be a "better buy"?

I have other ideas, but the wife doesn't want to play anymore....

jt.

Just got the tree and decorations down from the loft and I found a present that
I forgot to give the kids last year. I was pretty gutted really because I know they
would have loved a kitten! Courtesy of www.mycall.mobi.

If you are so serious about the best power source mention your MWatts range & contact www.sustechinitiatives.com

I think you have to let markets decide which energy source will come out on top.

The problem is not which is the best source of electrical power, but, situationally, which source is the best alternative in a geographic location.

In countries such as Sweden, the power is mainly hydroelectric, in Greenland, much power is from thermal storage due to the shallow magma layer of hot earth fluids.

Likewise, a windy area would have a better use of consistent winds versus a sunny area using solar power.

We also need to review life cycle costing so we do not expend more energy in the collection system than can be recovered by the new "producer" of electricity.

A human powered electrical production would require the "fuel" to that human that demands inputs from multiple sources of energy and all this needs to be reviewed in balance.

We also need to reconsider our abuse of the energy we have and conservation and protection of energy is required. This includes transmission of power, transforming power losess and inefficient delivery of end energy equivalents.

This type of forum should not, however be a joke. We have a population explosion on this planet that needs a careful balance of ALL sources of power played against international policies that also balance quality of life, safety and environmental impacts. There is no silver bullet that will solve all requirements, there is however, a better mindset of individuals and our leaders that can set the framework for a reasonable approach to power "recovery" redirection and distribution.

Keep warm this winter and happy holidays.

I think that bigger Nat gas lines need to be installed and would put allot of people to work right now. We do have the supplies, and along with solar steam power and conservation, we can make it work. Use what we have, and start putting people to work. Nat gas can be burned very efficiently for now.

Other Best Power Source can be Ocen Energy......Ocean can produce two types of energy: thermal energy from the sun's heat, and mechanical energy from the tides and waves. The fact that the marine renewable sector is less well developed than other energy industries presents companies with both opportunities and challenges.

"Best" can depend on what part of the country you are located in.

Cheapest is also location dependent. In New York, they are getting much of their electrical power from hydroelectric systems located in Canada. Other areas are using low cost coal generated electrical power. Natural gas is sure to rise in cost as more production increases the rate it is burned, and imports are required to keep up with that demand. Oil seems to be the least liked generation source, even though in the 70's it was very popular, now it has become much more expensive.

Solar PV systems are increasingly becoming a low cost alternative to grid power. Very popular in the southern states, where the sun seems to shine much of the time. Concentrated PV systems are also being installed at a faster pace than ever before. If located in the right areas, higher altitudes, cooler climates, and dust free areas, they can produce what we need.

Large hydro projects also produce power without to much pollution. However loss of life in human terms is small, significant if you are a fish going through a turbine, their mortality is pretty significant, and fish populations are receding in alarming rates. There is always a small amount of pollution, such as a couple of gallons of lubricating oil leaking into the millions of cubic feet of water passing through the dam weekly. Human life loss can or could be significant during a dam failure, yet that is not to common in the United States. When it happens, more than 100 lives are lost at the same time.

My vote is for a homeowner, small PV system on the roof and a solar water heater will produce the best energy to power a home. Solar water heaters are a code requirement to construct a new home in Israel, and should be a requirement all around the world, at least south of the 45th parallel, where the sunshine is abundant.

If you consider power requirements for a Wal Mart or typical 350,000 square foot mall, you need to have more electrical power than a few solar panels can produce. Covering the mall roofs is actually happening in southern California, where $0.16 per KW power is reality now, and installing $1 per rated watt solar panels is also happening at a very fast pace today. The 350,000 square foot mall roof is not large enough to produce the 10,000 amps at 480 volts used by a typical air conditioned mall with seemingly millions of watts of lights to show off the merchandise.

Changing to LED display lights not only saves lighting energy costs, but also reduces heating loads, and significantly increases the brightness of the building.

A few large wind turbines can offset the power requirements for a place like Wal Mart, and that is exactly what is happening in Mexico. Wal Mart is installing some 1.5 MW wind turbines in the southern states and off-setting the energy used in the Wal Marts across the country. One school recently installed a 10 KW wind generator on it's football field to offset nearly all it's daily needs for lighting the classrooms. Installing sun tubes also reduced the need for artificial lights in places like the bathrooms, and classrooms.