Is it practical to generate all US power by solar PV?

[IllyaKuryakin]

All the money in the world (evil laugh here) would not buy enough battery storage to power a US powered only by PV

Yes, but batteries aren't the only way to store power. Power can be stored by electrolysis and regenerated with a fuel cell for instance, or it can be stored by pumping water up a hill and regenerated with hydroelectric generators as it runs back downhill. In either case, theoretical efficiency is capped out at about 25%. Once again, it's technically possible, but it's just not practical.

 

[mheslep]

Yes, but batteries aren't the only way to store power. Power can be stored by electrolysis and regenerated with a fuel cell for instance, or it can be stored by pumping water up a hill and regenerated with hydroelectric generators as it runs back downhill. In either case, theoretical efficiency is capped out at about 25%. Once again, it's technically possible, but it's just not practical.

I suppose, though in the US what you describe implies enough hydro or gas-fired plant or fuel cell capacity to run the entire load for days. That is, the required capacity is the same size that the US already has in place of ~1 TW, with a big switch on the side to flip it all off for a few hours (why?) while the solar science project collects sunlight. As you say, technically possible, like traveling east round the world to get to the house next door to the west.

 

[anorlunda]

Yes, but batteries aren't the only way to store power. Power can be stored by electrolysis and regenerated with a fuel cell for instance, or it can be stored by pumping water up a hill and regenerated with hydroelectric generators as it runs back downhill. In either case, theoretical efficiency is capped out at about 25%. Once again, it's technically possible, but it's just not practical.

Pumped hydro is 75% efficient, not 25%. For example, https://en.m.wikipedia.org/wiki/Blenheim-Gilboa_Hydroelectric_Power_Station
Where did you get 25%?

But pumped hydro is not scalable much beyond what exists because of the rarity of suitable sites.

 

[sophiecentaur]

consider a piezoelectric roadway surface. The bigger the vehicle, the more juice you get.

Every Joule that your PZ generators would produce would have to come from a Joule of motive Energy supplied to the vehicle. The system cannot produce more energy than you put into it.
Such systems could 'pinch' energy from passing cars on a small scale - perhaps as a toll for using certain roads- but it is not a solution to national energy resources, I'm afraid.

 

[sophiecentaur]

I looked through this thread and (as usual) I can't find anyone suggesting that one good answer to the problem is just to use less Energy. Not a popular idea for any but the brown rice and sandals brigade (and me) but it could be enormously good value.
The latest 'Terraforming Venus" thread has just passed by and, again, no one introduced the idea of efficient use of any resources. They want it to be just like Earth and look where that is getting us all.

 

[anorlunda]

I can't find anyone suggesting that one good answer to the problem is just to use less Energy.

I agree with that 110% Sophie. But we wanted a thread more narrowly focused than, https://www.physicsforums.com/threads/you-fix-the-us-energy-crisis.42564/
To discuss energy in general, that tread is still open and it is the place to do it.

But since you mentioned less energy, I cut my own electric consumption to 0.6 kwh/day for 2 people (that's gross consumption, not net). A 200 watt PV panel supplies 100% of our needs except about 25 days per year when it has been too cloudy too long. And we don't live frugally, we live a luxury life on our boat. It can be done.

 

[IllyaKuryakin]

Pumped hydro is 75% efficient, not 25%. For example, https://en.m.wikipedia.org/wiki/Blenheim-Gilboa_Hydroelectric_Power_Station
Where did you get 25%?

But pumped hydro is not scalable much beyond what exists because of the rarity of suitable sites.

Yes! You are quite correct. Pumped hydroelectric storage cycle efficiency is 75% or better. Thanks for the correction. As you noted, suitable sites with the water and elevation are the constraining factors.

 

[sophiecentaur]

suitable sites with the water and elevation are the constraining factors

That's very true. I talked to a guy in the Sierra Nevada (Spain) and asked why there were not many more hydroelectric schemes. He replied that the mountainous terrain just didn't have enough useful valleys that could be economically dammed. I had never thought of that - I just saw all the mountains and the water rushing down the sides. I guess that small scale projects could have a part to play here, though. How does the size affect the efficiency? Much less than in thermal power stations, I imagine.

 

[nikkkom]

I looked through this thread and (as usual) I can't find anyone suggesting that one good answer to the problem is just to use less Energy.

We already do that. Almost every industrial activity looks at opportunities to optimize its energy usage.

At home, LED lamps use some x8 less energy than old incandescent bulbs!
Computers go to sleep when not in use. Thanks to demands of battery-backed phones, today's CPUs can go to sleep incredibly fast - some milliseconds! - after they finished with the tasks, and then wake up again when they need to work again. Ten years ago, they just run continuously.
Modern homes are much better insulated. Many older ones have better insulation added.

 

[nikkkom]

All the money in the world (evil laugh here) would not buy enough battery storage to power a US powered only by PV

Care to support that with numbers?

 

[jim hardy]

I looked through this thread and (as usual) I can't find anyone suggesting that one good answer to the problem is just to use less Energy.

Too logical.

How does the size affect the efficiency?

Not greatly i believe. But when the fuel is rain, maybe return on investment is a better metric.
There's a 1925-ish 400 kw low head hydro plant near my home that's now a museum. It ran until 1972.
The $20 to $40 an hour revenue just doesn't make economic sense i guess. Somebody would have to tend to it , unless they spent a metric ton of money to rebuild it with modern controls so it could run unattended..
www.panoramio.com/photo/7324660
That is why i have a hard time accepting windmills and solar.
There do exist 60mw gas turbines that run unattended but were i a utility executive i'd be nervous about them. I think big machinery needs to be surrounded with loving, attentive eyes and ears. Economy of scale pays for that.
What they do with windfarms is instrument everything , telemeter it and pay a maintenance outfit to be those remote eyes and ears. Much like modern airliners.

As an "Old Guy" i don't handle change all that well. (see my signature line)

 

[The Electrician]

A current magazine article discusses an important ancillary issue associated with electricity generation: http://www.americanscientist.org/issues/feature/2016/3/energy-water-nexus-head-on-collision-or-near-miss

I've read the article and there are some facts about water usage in connection with power generation that are critical, and not well known.

 

[Baluncore]

For over 30 years now, it has been advocated that giving customers free high efficiency light globes and free insulation for their houses, is a lower cost option than building a new power station. In Australia the “Energy Efficient Homes Package” was implemented in 2009. That gave free roof insulation to uninsulated houses. Giving anything back to the people was a political anathema to the opposition of the day, resulting in a focus on the costs, with a complete failure to analyse the positive aspects of the scheme that the nation benefits from to this day.

A skylight is an efficient solar energy collector, but it does not use any form of storage. If we made skylights from laminated glass with a phosphorescent filler, then that would be solar energy stored for lighting. We would need to draw the curtains to turn of the light. It would be considered as solar power and storage, but it would not qualify as solar PV as in the title of this thread, so is off topic.

 

[OmCheeto]

I agree with that 110% Sophie. But we wanted a thread more narrowly focused than, https://www.physicsforums.com/threads/you-fix-the-us-energy-crisis.42564/
To discuss energy in general, that tread is still open and it is the place to do it.

But since you mentioned less energy, I cut my own electric consumption to 0.6 kwh/day for 2 people (that's gross consumption, not net). A 200 watt PV panel supplies 100% of our needs except about 25 days per year when it has been too cloudy too long. And we don't live frugally, we live a luxury life on our boat. It can be done.

This kind of floored me, when I saw this the other day. The average home installed PV system is 4000 watts.
Trying to figure how you did that, I compared where you and I live.
It started to make sense.

Blue: Om's electrical usage (Careful! I multiplied it by 10)
Green: Heating degree days where Om lives
Yellow: Heating degree days where Anorlunda lives​

You don't need any heat!

But I figured out the other day that I needed at least 1000 watt system, if I installed a solar thermal system.
So that had me scratching my head.
I thought that maybe you caught all your food off the side of your boat every day, and didn't need a refrigerator.
But I decided that was silly, so I researched refrigerators.
It would appear that the one I posted about the other day, isn't that extraordinary.

According to the Energystar website, my refrigerator: Oct 1988 19.0-21.4 Cubic Feet Side-by-Side
uses 2,623 kWh/year

I found a new refrigerator for $450 that uses only 382 kWh/year.
That's 7 times more efficient than mine.

Calculating the cost savings @ $0.118/kWh:

2623 kWh - 382 kWh = 2241 kWh/yr annual savings
2241 kWh * $0.118/kWh = $264 annual savings​

That fridge would pay for itself in less than two years.

And that also reduces the size of my solar system by a factor of 7.
1000 watts / 7 = 143 watts

That's starting to make my laptop look like a power hog: 44 watts.

hmmmm...
Do people still say "Jeez Louise"?

 

[dlgoff]

Trying to figure how you did that, ...

There are ways. Maybe something like this.

image compliments of http://www.tacticalsolar.com/rugged_solar_tents.php

 

[Baluncore]

I cut my own electric consumption to 0.6 kwh/day for 2 people (that's gross consumption, not net). A 200 watt PV panel supplies 100% of our needs except about 25 days per year when it has been too cloudy too long. And we don't live frugally, we live a luxury life on our boat. It can be done.

Do you have hot water?
Do you cook on the boat with electricity or fossil fuel?

 

[OmCheeto]

...
Modern homes are much better insulated. Many older ones have better insulation added.

My house was built in 1945. When I bought it, back in 1989, I discovered one of 3 reasons why it was so cheap, and had been on the market, empty, for 3 years.
It had no insulation!

I mentioned this one year, and one day ago, in the "Tesla Powerwall" thread. [ref]

...
For fun over the last few months, I've been transcribing my old electrical bills.
Between 1989 and 1995 you can see my winter energy use dropping every year.
This is because I discovered my first winter, that the house had virtually no insulation.
So each year, for 5 years, I removed the sheetrock from a single room, rewired, and insulated the exterior walls.
I also added insulation in the attic and crawlspace.

Those Powerwalls are starting to make more sense now.

 

[rbelli1]

I found a new refrigerator for $450 that uses only 382 kWh/year.
That's 7 times more efficient than mine.

Calculating the cost savings @ $0.118/kWh:
2623 kWh - 382 kWh = 2241 kWh/yr annual savings
2241 kWh * $0.118/kWh = $264 annual savings

In the US right now for some reason politically spending money to save or make money is anathema. I don't follow anything outside the US so your mileage may vary.

Many (US; other country?) politicians say you can't spend your way out of debt. Many (most?) businesses do just that. Look at any successful business venture and you will find debt as a large part of their balance sheet.

Your example does just that. Buy a more efficient appliance and you will save money in the minimal long term. Even doing that on the almost usurious rates of credit cards and you save money. This doesn't even consider externalized costs associated with electricity.

BoB

Edit: This is an off topic rant but it it the same logic that condemns solar (or other alternate energy) power. Buying a new TV on 30% interest when the old TV works perfectly well is a bad idea therefore spending on credit is always (100% no exceptions) a bad idea. Solar power will never be able to replace 100% (absolutely 100%; not candles no outdoor grilling) of our power therefore trying to replace any part (no matter how small) of our power is a bad idea.

 

[Salvador]

Well first of all I just couldn't help myself but to comment on sophie's posts here , yes surely being more efficient is a nice thing to do , also riding a bike to a place near your house at sunny times is both better for you and the environment but guess what most people have their "reasons" not to do that.that results in more energy consumption and shorter lifespan and on average more health problems which leads to more money spending and consumption etc.a circle that never ends.
Forgive my deterministic view but I think it's quite impossible to change human nature , all empires and political ideologies that tried it failed sooner or later , if it changes at all it happens in terms of centuries not decades.So the only way we can spend and consume less is to give the greedy civilization technology which gives them the same level and quantity of stuff and satisfaction. And many here already touched downed on that like more efficient fridges , house thermal insulation , more efficient lights etc etc.
Simply saying , Hey, stop using your pc so often or shower in colder water isn't going to work for the 21st century consumer.Not everybody collects his empty aluminum cat meal packs and other household trash like I do just to then take it to the metal recycling scrapyard.
This being said I think even with our more efficient appliances and housing we still won't be able to cut down our total annual energy usage simply because tech is spreading faster by the day and more people are using it also by the day and also more people are being born so I think we all can see where this is going.
Either we start killing portions of our civilization or greatly reduce birth rates like China did back in the day or we have to find some new stable ways of energy production that are also environment friendly and solar is just one rather small bit of that.as for what @rbelli1 said I don't think one can spend his way out of debt , the only way that could happen is if by spending the budget gets some boosted gain like for example being in debt but inventing something high tech which then is bought heavily and is also valuable and so gives some gain.
in modern times we face something Karl Marx wrote about back in the day , that most of labor would be replaced by technology simply because it's more reliable and cheaper and faster that way so capitalism and every sane person running a business would stick to that but this also means that the masses that we have become these days in terms of population size have nothing much left to do to earn their living so wages drop , the average person is not capable enough to be a high skilled worker or a lawyer or something like that so an economy that has advanced to this phase is somewhat in trouble.I think it's the US situation today (one of the reasons why Trump is so popular because of his bringing jobs back rant) , the spending hasn't gone down but the average income from the average person has declined , if not for some huge outside reason or huge resources that can be sold the average country is only as strong as its average citizen is in terms of his tax returns to the budget.
so if one decreases the income but keeps the spending he ultimately runs into debt and without changing the very core of this I have a hard time seeing how it can lead out of debt.

 

[sophiecentaur]

Edit: This is an off topic rant but it it the same logic that condemns solar (or other alternate energy) power. Buying a new TV on 30% interest when the old TV works perfectly well is a bad idea therefore spending on credit is always (100% no exceptions) a bad idea. Solar power will never be able to replace 100% (absolutely 100%; not candles no outdoor grilling) of our power therefore trying to replace any part (no matter how small) of our power is a bad idea.

The energy used in manufacturing can be much greater than the energy used by an appliance (including a Motor Car!). Can you think of anything more loopy than buying a brand new car on the basis that it will do another 10mpg? The whole automobile industry is selling cars (new ones) as a way of making itself money and not saving you money.
But to do anything about that would require a completely different slant to the economies of rich and developing nations. Economies rely on growth and expanding customer numbers. That is the real reason for our energy problems and it's a very hard nut to crack. Reducing consumption would, as it stands, result in people being put out of work.

 

[jim hardy]

Economies rely on growth and expanding customer numbers.

There's the rub. Unlimited growth is the philosophy of the cancer cell.
At some point an economy needs to switch from a growth mindset to a maintenance mindset. Nature does that with her organisms, by age twenty we are physically as big as we'll ever get and we spend the rest of our life hopefully maintaining the body and growing the mind.

If we built cars to last forty years instead of ten everybody could have two or three of them. We'd employ more people maintaining them and fewer building them. Same for TV sets and refrigerators. We might even learn to understand and do routine work on them ourselves. This being the age of technology, why isn't more practical stuff like toaster repair in the primary curriculum ?

Law of supply and demand applies to labor just like any other commodity. As Asia mechanized and entered the labor force manufacturing moved there. We Americans tried shifting our economic base to approving one another's mortgage applications , that went bust in 2008. Now we've shifted it to paying one another's doctor bills and that's going to crash too.The Law of Diminishing returns is as much a natural law as are Newton's three.
Carbon fuel and steam let the human race mechanize. Carnot tells us what are the practical limits of those heat engines, putting a number on just how far we can take them .
Renewables are less power intense than coal. But not less labor intense.
Might it be that Mother Nature's grand plan for us is to become a species of thoughtful tinkerers tending to the machinery that provides us a comfortable existence from the daily contribution of the sun ?
After all, when Mother Nature gets a design perfected she quits tinkering with it, to wit the shark and the VW Beetle.

A paradigm shift from a gadfly throwaway society to a reverent one that cherishes and takes good care of what it has would be a maintenance man's utopia.
Anorlunda appears to be already there waiting on the rest of us.

But I'm just a burnt out old maintenance man.

disclaimer - My electric consumption runs from ~400 to ~900 kwh/month, mostly hot water and in the summertime, airconditioning.

old jim

 

[jim hardy]

Spend your way out of debt? Only if you spend it on something productive.

 

[Dale]

Closed for moderation

Edit: we will have to leave it closed. There is a lot of political discussion mixed into the technical discussion, and no clean way to split them. I gave up after tagging 50 posts for deletion.