There Ain’t No Such Thing as a Free Energy
Here’s a fun little tweet that caught a lot of flak this week.
I had to read this post like 17 times before I understood what the controversy was. And not cause I’m stupid, neither.
It’s because I actually HAVE solar power.
Ostensibly, this tweet is humorous in part because solar panels don’t make heat, they make electricity. But a lot of homes have heaters that DO run on electricity – baseboards and electric furnaces for instance. Many natural gas, coal, and fuel oil heat systems have fans on them or vent systems to distribute heated air that are electric-powered, even though electricity is not their primary source of heat. Additionally, many Americans use space heaters to supplement inadequate central heating, particularly in subzero temperatures. Electric heat is becoming more and more popular in environmentally conscious states like California, since it’s zero emission.
So this tweet isn’t as dumb as it seems at first blush. The fact is, if America increased reliance on solar power, quite a few people would be in effect heating their homes with solar panels. Solar panels create electricity that would be stored in a battery bank and then they’d use some sort of heating device powered by that stored electricity for warmth.
The other humorous aspect of this tweet is that chilly temperatures and sunshine are two different things and people are assuming that Jim Hoft is confused about that. It can, of course, be frigid on a sunny day and vice versa.
But the thing is, while sunlight and temperatures are not directly related, they ARE strongly correlated. In a Northern climate, November through February are not only the coldest months of the year, but they’re also the hardest to get through using just solar. (really, anywhere from October through April is dicey)
As in, it’s impossible.
My husband and I are experts at this lifestyle, we’re totally dedicated to the principle, we live in a dry climate with sunny fall weather even into November most years, and it’s still impossible.
It’s not that it’s cold per se – solar panels actually work more efficiently in cold temperatures. It’s that it’s overcast or foggy much of the time, the days are shorter, and worst of all the sunlight is coming in at a different angle than it does in the summertime (short days and the sun at a lower position in the sky are why winter is cold, or so my second grader tells me.) The sun is puny and weak in the winter. He just doesn’t have the strength to charge our batteries as fast as he does in the summer. Even on the rare sunny winter day we simply cannot make enough solar to break even on our household electrical usage – lights, tv, computer, washing clothes, pumping water, incidental appliances – let alone fully charge our battery bank. And we don’t even heat, cook, make hot water, or run our refrigerator with electricity.
A person trying to heat a home using electricity-generated solar power in a Northern climate actually would have serious problems in extremely cold temps. Cold temperatures, even when accompanied by sunshine, mean that one would need to run an electric heater longer and at a higher setting and this would drain your battery bank much more quickly. And remember, it’s winter; the days are shorter, the sun is weaker, you use more lights, your batteries recharge slower than in the summertime. Even if it was cold and sunny all winter long (never happens) heating with solar alone would be challenging, if not impossible in a Northern climate like the upper Midwest just because of day length and sun angle.
So what would people do in this situation? What do we do? How do we heat our home and generate electricity on days when Jolly Mr. Sun is nowhere to be seen?? Well, we rely (as most Northern solar users do) on some things that are not terribly environmentally friendly. We heat with a wood stove, we burn propane for hot water, cooking, and refrigeration. When our batteries start to run low (approximately every 2-3 days even though we conserve religiously) we run either a gasoline or propane generator. For several hours. That’s what life on “clean and green” solar in a Northern climate actually entails…frequent supplementation by wood and/or fossil fuels. Switching the city of Chicago (not to mention Detroit and Minneapolis and Milwaukee and Buffalo) over to solar power means that 3 million people would end up burning wood or coal for heat and/or running gasoline or propane generators that are polluting, dangerous, difficult to run, and noisy. Going solar with the technology that presently exists would be worse for the environment, not better, than the system we presently have.
A lot of people who don’t know what they’re talking about like to discuss solar power as if it’s some sort of Messianic solution to climate change. The argument for renewable energy* is often presented as if there’s a sinister fossil fuel cabal preventing the nation from easily and joyfully switching to solar after which we’d all live happily ever after. But solar power has its limitations and drawbacks just like everything does. And one of the largest is that you can’t manage on solar alone for a good 6 months of the year in cold and wintry Northern climes.
If solar was simple, if it was a magic unicorn just this side of cold fusion, we’d all already be using it. There are very real reasons why we don’t, and one of them is cold and inclement winter weather in 2/3 of the United States.
The Gateway Pundit may be an idiot, but he’s not wrong on this one.
*Wind power has even more limitations than solar. Wind turbines have to run at quite a high speed, and sustain them for some time, to produce power. An occasional gust won’t do, nor will a steady light breeze. High winds for long periods are required to make usable amounts of electricity. Wind is a massive expense for very little power generation at least on the individual household level.
Photo by LunchboxLarry 
Allow me to offer one footnote to your otherwise fine post:
We could not run a northern city solely upon the solar or wind power it could produce locally. I.E. If Chicago or Milwaukee or the Twin Cities were to attempt to install sufficient wind or solar power capacity to go ‘off grid’ for the entirety of a year, the installed capacity would be ridiculous.
Luckily, we don’t need to go ‘off grid’ for a whole city, and we can focus solar and wind generation in geographic regions where is makes sense, then send that power to other places.
That said until we have some much better industrial scale energy storage options, we will still need base load plants and dispatchable sources that can be spun up quickly (gas turbines). Some areas could probably get away with not having coal fired plants, as long as some GTGS were installed, but not the entirety of the country.
Honestly, at this point, utility scale storage is one of the biggest limitations in rolling out solar and wind power.Report
Or greater transmission scope. Besides storage, you can make a bunch of intermittent but uncorrelated sources much less intermittent if you have some excess generating capacity everywhere and adequate bulk transmission. The people at the national labs who do this kind of modeling for a living have shown repeatedly that this can be done in at least the US Western Interconnect. The West is blessed with diverse renewable resources (hydro, geothermal, wind, solar) in diverse locations. A very large majority of the demand for electricity occurs in a small number of large metro areas. There are a couple of different, simple HVDC topologies that could shuttle bulk power around to balance supply and demand. Coincidentally, both of those topologies run past places that would work well for pumped-hydro storage, which is already proven at industrial scale (eg, about 40 miles from my house is a 300MW pumped hydro power plant).
Granted, the Eastern Interconnect is a whole lot harder problem.Report
Pumped Hydro should be doing a lot more for the country than it is, especially out west. I’m not entirely certain why it isn’t. Cost? Environmental impacts?
Which plant is close to you?
But yes, the west is best suited to make use of renewables.
I also forgot to tack on the perennial comment about how utilities are still paying off capital equipment expenditures from decades ago, etc….Report
Xcel Energy’s Cabin Creek is the one I mentioned. They made the headlines about a dozen years ago when several workers were killed by a fire/explosion while doing repair work in one of the tunnels. The federal Dept of Reclamation operates two other pumped-storage plants in Colorado, one up towards Leadville (200 MW) and one near Fort Collins (100 MW).
Xcel uses Cabin Creek for peaking power occasionally, but more often as spinning reserve (due to hydro’s high ramp rate) and for ancillary services like frequency control. Dept of Reclamation is probably similar, but are not noted for sharing details.Report
Yep totally. We often wish in the summer (when we hit 100% charge at 10 am or whatever) that we had some way to store it for the wintertime. Just doesn’t exist. If they can make that happen that will be a breakthrough of epic proportions.Report
We do have ways to store it besides Lead Acid or Li-Ion batteries. I talk about such methods regularly on my Tech Tuesdays, especially when new ideas, or improvements on old ones, come around. But such methods require a capital investment that is hard to make when it’s easier to just install some GTGS.Report
I didn’t want to be the guy to say this since Oscar is our resident rocket scientist but…
Well, technically, there is such a thing as free energy…Report
Physicists are often treated to quotes by Inigo Montoya regarding words and their meanings.Report
Inconceivable!Report
The energy only seems free until you find out what Gibbs is charging for it.
Hundreds of municipalities, and some states, have proudly said they’ll go 100% renewable. Only five or so of those claim they’ve done it (Huffington Post article, and those usually have a huge dam nearby.
Aspen Colorado, pop 7200, gets about half its electricity from hydroelectric and much of the rest from wind power, both of which it imports from other states and regions by signing contracts. The power grid operators probably thought “Yeah, whatever makes you happy. Sign here.” And don’t ask about the natural gas that heats the place.
Rockport Missouri , pop 1300, is right next to a major wind farm, and the average output of the wind turbines slightly exceeds their average electricity consumption.
Greensburg Kansas, pop 778, uses a massive wind installation, along with some solar and biogas. They were rebuilding in a big way after being wiped out by a tornado.
Kodiak Island Alaska, pop 6300, has three 11 MW hydroelectric generators, plus about 9 MW in wind turbines, plus diesel backup.
Burlington Vermont, pop 42,000, uses most hydroelectric, but also renewable energy from logging anything within a 60 miles radius. How did loggers go from destroying the planet to saving it when they’re using the same chainsaws on the same forests?
So that’s 58,000 people living in towns that can make some claim to being 100% renewable, ignoring the fact that except for Kodiak, they’re all counting on the grid to keep electricity up 100% of the time.
And the simple truth is that wind and solar, without storage, can’t keep a grid up because calm nights do occur, and quite frequently, and storage is a very big, expensive problem. Hydroelectric, a great base-load generator, simply doesn’t have enough water and height in this country to product significantly more power than it already does, at least not without driving environmentalists apoplectic at the loss of free-running streams.
And even if we shut down every single US fossil fuel plant, and then shot each other in the head in the world’s largest mass suicide, the staggering CO2 emissions increases from China, India, and Africa would make our sacrifice futile and pointless. Even if you regard CO2 as pollution, solutions that don’t impact the major overseas sources of that pollution are just virtue signalling – with working people’s money, because working people do have to pay their electric bills.
The cost effective solutions don’t need advocates because they attract investors and are self-sustaining. The plans that requires lots of advocacy usually require it because they don’t make financial sense to customers and investors. And as always, read the fine print on any installation plan to avoid getting flim-flammed. Cheap energy sells itself. Getting rooked into buying more expensive, less-reliable energy takes a sales-pitch by fast-talking man in a plaid suit and fancy hat.Report
I grew up in Michigan and, lemme tell ya, we said goodbye to the sun somewhere around Halloween and those dang lake effects just covered the sun like it was being eaten by wolves in the old religions and we didn’t see it again until around Easter.
I’m down with using solar… but if you’re going to rely on it, you’d best be using it for AC rather than for heat.Report
Because of Physics, and counter intuitively, it’s MUCH more energy intensive to heat things than it is to cool things down.
Typical for-entire-home air conditioning is like 3500 Watts, that’s two space heaters.
And yes, agreed with you and Kristin that the North is a problem.
Locally on December 21st, there are 9 hours of daylight and 15 of night.
Yearly we average 64 sunny days, 96 partly sunny days, for a total of 160 (less than half). Most of those days with sun are in the summer.
The low (according to my car) driving to work was -19 F last week, the windchill was much lower. Batteries don’t work well in the cold and using them to heat is brutally expensive energy-wise.Report
I think that the main breakthrough that we need to happen is on the battery level.
It’s one thing to use energy within a few moments of generating it. It’s quite another to use it days or weeks or months later. If we could figure out ways to generate heat in February from solar energy collected in July, we’d have something.Report
Because of Physics, and counter intuitively, it’s MUCH more energy intensive to heat things than it is to cool things down.
That can’t possibly be true. The only way we have to cool things down is to move existing heat from one place to another, which means that, if we’ve cooled somewhere down X degrees, we’ve heated somewhere else up X degrees….and we’ve spent energy doing that, too, which generated waste heat.
All cooling process that we can do are literally zero-sum processes, which means that, by definition, we could have spent the same amount of energy running the thing in reverse and gotten the same (Technically slightly more due to waste) heat.
What is true is that, in the US at least, we need to heat things up _far more_ than we need to cool them down. It’s extremely rare, and only happens in certain parts of the country, where we need to cool housing down a mere, oh, 30 degrees, for example. Whereas the vast majority of the country (Probably only barring Florida) will have to be heated 30+ degrees for several months, and some places will have to regularly be heated 50+ degrees.
So we spent a lot more on heating than cooling.
But that’s not anything to do with physics, that’s just because the average temperature humans want is about 70 degrees, and only southern Florida manages that as a yearly average temperature. (Yes, not even places like Death Valley.) The continental US averages 52 degrees, so, on average, we have about 20 degrees more heating than cooling.
If humans wanted to live at, say, 30 degrees instead, we’d spend more on cooling than heating. Or, actually, we’d all be dead, or at least not spread over the planet, because we didn’t invent cooling that could do that until fairly recently.Report
DavidTC,
No, DM is correct here. That’s because moving heat — thermal energy — around is much more efficient than creating it from scratch. When I was in engineering school forty years ago the ratio was about 8.5:1 and I would be amazed if that hasn’t improved. You can probably find a much better explanation on Youtube or Wikipedia, but the basic idea is you have a working fluid — the refrigerant — in a closed loop. A pump, a high pressure condenser on the hot side, an expansion valve, then finally a low pressure evaporator on the cold side.. So that’s how air conditioning, and refrigeration in general, works. And yes, that process can be easily run the other direction to provide heat, i.e., heat pumps, but for practical reasons having to do with temperature differentials between the environment and the condenser/evaporator exchangers, they only really work well where it doesn’t get really cold unless you use a ground loop where the cold side can suck the heat out of ground water.
So most practical heating/AC systems will burn natural gas or something for heat because resistive heating takes a bunch of electricity and is expensive af.Report
but for practical reasons having to do with temperature differentials between the environment and the condenser/evaporator exchangers, they only really work well where it doesn’t get really cold unless you use a ground loop where the cold side can suck the heat out of ground water.
‘where it doesn’t get cold’ is doing a lot of work there, mostly because you didn’t mention AC don’t work where it doesn’t ‘get warm’, which, as I mention, is literally the entire US, comparatively speaking.
Just like heat pumps do not work when they need to heat across large differences, AC do not work when they need to cool across large differences. In fact, and this is somewhat obvious because they are literally the same device facing in opposite directions, the gap is exactly the same! It’s about 40 degrees, give or take.
The reason that heating costs more is _not_ that it’s ‘physics says heating is less efficient’. It’s because in summer ‘How much do we need to cool things?’ is about 10 degrees, and really doesn’t get over 30, whereas in winter ‘How much do we need to heat things?’ is at least 30 degrees and can be up to 60…or 100, apparently.
It’s literally twice the distance or more on average.
Now, because _where we want the temperature to be_ is so much higher than it often is, we use less energy efficient ways to heat, but that’s not ‘physics says it’s less efficient’…I assure you, if we were regularly cooling houses 60+ degrees, it would be _aburdly_ inefficient. Epicly inefficient.
It’s just…we don’t want to do that. That’s nothing to do with physics…it’s just biology.Report
The SR-71’s air conditioner had produce air at -40 F to keep the cockpit air at 60 F and the cockpit interior surface at 80 F. The boundary layer air around the cockpit was 632 F, while the outer titanium skin was at 450 F. The outer surface of the 3/8″ thick cockpit windows was at 420 F and the inner surface was about 250 F.
The system’s heat exchanger accomplished this by dumping the heat into the fuel prior to injection into the engines.Report
George & Road are correct. It is always more efficient to move heat than to generate it. And it’s very important to keep in mind where heat is moving from and to.
I had three whole upper level engineering courses about this.
If you want us to crack out the math, we can.Report
I remember reading some years back that we had reached the practical limit on aerodynamics for cars that used an internal combustion engine and friction brakes. Making any more improvements meant reducing air flow below the level required to dump all the waste heat.Report
Wow, you guys just…wow. People keep thinking I’m saying something about ‘moving heat vs making it’.
I am not. I am saying one very basic fact: Heating something the same amount as cooling something always can be done for the same amount of energy, or less. According to the laws of physics. Always. Always always always. There is no possible setup where this is incorrect, because under the laws of thermodynamics, all possible ‘cooling systems’ are just heat moving systems, so if you can spend a certain amount of energy to cool something, you can turn the cooling device around and spend literally the same amount of money heating it the same amount.
Please carefully notice my use of the phrase ‘the same amount’. It is vitally important to see that phrase. If you miss that phrase you will not understand a single word I am saying. People keep responding and missing that phrase, and end up comparing the average 60-degree heating changes that us humans do in our houses to average 20-degree cooling changes that us humans do in our houses!
I am not talking about ‘What accounts for our energy bills’. I am talking about the laws of physics. Or laws of engineering.
Under the laws of physics, and under our ability to build machines, heating and cooling small amounts is identical, assuming identical methods. Heating and cooling large amounts…well, heating actually quickly becomes much _more_ efficient compared to cooling, not less! This is because heating is able to switch over to other methods as the ‘moving heat’ method become less efficient across a larger temperature difference. But cooling is not able to switch and becomes more and more inefficient.
If we _actually wanted_ to cool our house 60 degrees with regard to the outside, if we wanted our house to be at 10 degrees on a 70-degree day, we’d have to…I don’t even know. Install five times as much AC as normal? Have some multi-stage system? I’m not sure, but I’m sure it would be way more energy than an electric heat coil taking us from 10 degrees to 70.
The idea that cooling is somehow more efficient according to the laws of physics is _obviously_ wrong and it’s so obviously wrong that the people who think they ‘disagree’ with me while basically appearing to understand this is…perplexing.
The applicable ‘law of physic’ with regard to energy spending by humans is basically ‘Heating something 60 degrees is more work than cooling it 20 degrees’, which is…pretty obvious when you think about it. Of course we use less energy cooling our houses vs. heating them when we generally cool them a third as much as we heat them!
That’s not ‘efficiency’, that’s ‘doing much much less work’.Report
@DavidTC
In the abstract you’re mostly correct, although I’m pretty sure entropy enters the picture as well, but it’s been a few
yearsdecades since I studied it. (You regularly encounter the problem of waste heat; I’m not sure there’s even such a thing as “waste cool”.)The problem is at the level of engineering. air conditioners/heat pumps use a working fluid — the refrigerant — in a closed loop. Compressor >> condenser >> expansion valve >> evaporator. The condenser and evaporator are heat exchangers, like the radiator in your car. The condenser cools the high pressure (because of the compressor) gas producing the high pressure fluid. The expansion valve (like a faucet barely cracked open) expands the high pressure fluid to a low pressure gas which is accompanied by a temperature drop (Boyle’s Law). The evaporator then heats the working fluid by sucking up heat from the environment. Then back to the compressor.
The efficiency of these heat exchangers is a function, among other things, of the temperature differential between the fluids on either side of the exchange; the higher the differential the better. You also do better with liquids than gases. In an air conditioner the idea is to make the refrigerant flowing through the evaporator colder than the ambient air, BUT there’s a limit to how cold you can actually make it. Not based on the physics of the working fluid but the more prosaic issue of humidity. If the evaporator temp is lower than the dew point you get condensation; not a biggie but you do have to collect and drain that water. But if the evaporator temp is lower than the freezing point of water then you get not only condensation but freezing as well. Big problem. Ice is a pretty good insulator and it blocks the air flow as well. Not a huge problem for air conditioning; you just engineer the pressures and temps to avoid that issue. But what happens when you try to run that process in reverse to make a heat pump to suck heat out of a cold environment to put in your house? You quickly run into the condensation/sublimation issue on the evaporator side and it’s difficult to achieve any reasonable temperature differential and thus efficiency. One solution is a ground loop heat pump that buries the evaporator coil so as to suck heat out of the ground/groundwater where you can maintain a decent temp differential. Otherwise you’re really forced to have a supplemental heating coil or gas furnace attached to the thing. Bottom line is heat pumps aren’t terribly practical in colder climes but it doesn’t really have a lot to do with the amount of heating you’re trying to accomplish as it does the practical engineering of the evaporator side.
Note to @Oscar Gordan: feel free to elaborate/correct/elucidate on this. Like I said, it’s been awhile.Report
Meh. It is another D minus trolling attempt to “own the libs” because that is all that is left for right-wingers on social media and AOC is their new hate-object that gets their underwear in a bunch.
We can’t rely on Solar or Wind for everything but it can help. There are also storage batteries for Solar power as well that can store energy. Even without solar, Michigan residents were called to save on heating because of trying to conserve natural gas and not put pressure on the system.Report
What strikes me is that in order to make Hoft’s comment anything other than idiocy, it is necessary to carefully parse it and give the best interpretation to it. It becomes necessary to take the literal tweet and reconstruct it:
“It is not possible to derive all our heating needs in all climate zones from solar panels alone.”
Which is of course an entirely reasonable statement, that its difficult to imagine anyone disagreeing with it.
Difficult because no one, least of all AOC, actually does disagree with it.
Because Hoft, in troll fashion takes the wildest strawman approach to AOC’s push for renewable energy. Even the most enthusiastic green advocate promotes a multi-pronged approach to energy where solar is merely one component.
Hoft isn’t stupid. He’s just malicious and dishonest, and is eagerly followed by malicious and dishonest people.Report
I read several dozen retweets and comments, and a significant number of people DID seem to believe in the straw man argument. They appeared to think it was totally possible to run everything on renewable energy right now, here, today, except that the evil oil companies were preventing that from happening.
.Report
no, there is no energy unicorn. Never was. But there are way better ways to generate electricity then burning fossil fuels. Its a three part problem.
1) Generation – we have too much generation capacity in too few places with the wrong tools. Create solar and wind farms where they make sense. Comingle them in some areas. And reacquaint America with the hydro power that fueled big swaths of our industrial revolution. Expand domestic roof top solar – if every new house built in every county in the country had solar panels, there would be a ton of generation capacity. Ditto commercial structures. And make it required to be azimuth tracking so the angle changes. Its not technically hard.
2) Transmission – we don’t have a smart grid; or for that matter a mediocre grid. Which means we can’t move excess energy from where it is to where its needed.Nor can we really store it anywhere along the way.
3) Storage – there are good industrial battery solutions, and good domestic ones too. but they are too few and like batteries for plug-in electrics, they are not receiving favorable support from government in the R&D space.
address these issues and you have a big jump past Hoft’s amazing trollishness.Report
Personally I’ve always thought the Midwest and northeast are well suited locations for nuclear power; they’re cold part of the year, geologically stable, suffer few severe weather effects that a nuclear plant would care about and have tons of readily available water. Even the older generation style fission plants are well suited to those locales.Report
I’ve been in favor of expanding nuclear since I was in high school and took part in a debate on the topic. It just makes sense. But not a popular opinion these days (if it ever was)Report
I just put solar on my house this summer, but it’s the kind where I have a sell-back to the utility company, and it’s meant to zero my power bill. Not the kind where I’m supposed to be off the grid. We burn natural gas for heating the house and water.
The thing is, here in CA, summer is the time of peak electrical demand, to run air conditioning. And we’ve zeroed that out, we’re even running someone else’s, or maybe a few someone else’s A/C. I think that makes a big difference. It’s not a failure because I’m not off the grid – that’s all-or-nothing thinking. That’s the sort of thinking Hoft seems to be employing. I can’t answer for his intentions, though.
You’re right. Totally off-the-grid is hard, really hard. But if we can spin up renewables and stand down coal plants or even gas plants, we should probably do that. For one thing, coal is getting relatively more expensive. I think we’re running out of rivers to dam, though.
I think we could put either a solar plant or a greensward on top of every building in an urban area. That would have a big impact in several dimensions, not just reducing greenhouse gasses, but reducing urban temperatures a bit, too.
It does amuse me to see people calling positions that poll with majority support “extremist” or “socialist”, though. Seventy percent of Americans think climate change is a problem of some magnitude.Report
Not only is insisting on going off-grid “all or nothing” thinking – it’s directly antithetical to the ostensible goal of environmentalism.
Why invest in chemically intensive battery systems, when you can leave the few hundred meters of copper wire right where they are?Report
I think we’re running out of rivers to dam, though.
In the US Western Interconnect states, about half of the potential conventional hydro power has been developed. Much less than half if British Columbia and Alberta, which are part of the same grid, are included. The Eastern Interconnect states have much less remaining, but again, there’s rather a lot in Canada if the Canadians decide they want to be in that business. Non-dammed run-of-river power is harder to estimate.
Through November of last year, the US Western Interconnect states generated about 46% of their electricity from renewable sources. Conventional hydro was about 28% and wind about 8%. The Eastern Interconnect got about 11% of their power from renewables. Wind was about 5% and conventional hydro about 4%. Texas got about 18% of their power from renewables, almost all from wind.
There are a number of projects going on in the West that should make it reasonable to boost that 46%. I predict the big hurdle will be whether the federal government is willing to go along.Report
DoD thinks climate change is problem of great enough magnitude to require planning and impact assessments for coastal bases.
But the military is so notoriously extremist and socialist… /sReport
So a group of military planners decided there needs to be more military planning?Report
I think that most people who are serious about renewable energies (except geothermal where feasible) view it, not as a substitute, but a supplement. By operating a widely dispersed renewable energy system, one can significantly reduce the load on more traditional, less environmentally friendly power sources.
It is also important to note that the traditional sources have had one or two centuries of widespread adoption to optimize their efficiency. Imagine where solar and wind will be say 80 years from now. We have seen improvement in the efficiency of hardware, the construction constraints, the storage systems, and the deployment.Report
Top end modern commercial solar cells are about 20-22% efficient. The theoretical efficiency of a perfect PN junction cell is about 33%. If you pull out all the stops and used a nearly infinite number of layers, you might hit 85%, and the top multi-junction cell is currently about 44% efficient.
The market will eventually decide whether it makes more sense to build a 44% efficient cell or just built a 22% efficient cell that’s twice as big, because it comes down to dollars per installed watt, including the land area. But there’s not room for a tremendous breakthrough because there’s only some many Watts in a square meter of sunlight, so the diffuse source problem will remain.
However, there’s also a ridiculous amount of land area. US peak electricity demand flat lined at about 1 teraWatt, or 3 kW per person, so in the far future (all of humanity living at American consumption rates) global demand probably wouldn’t much differ from that. With a projected 11 billion people in 2100, that would mean we need 33 teraWatts of installed capacity. At a global average of about 250 W/m^2 of sunlight (over 24 hours), that demand would require 260,000 square kilometers (100,000 sq miles) of installed cells at 50% efficiency. That’s the size of Colorado or Oregon, or the Western Sahara (the country).
Spread around the globe, that’s quite doable, as it comes to 24 square meters per person (16 feet by 16 feet). At the current commercial top end of 20% efficiency, the area would be 25 feet by 25 feet per person. Currently solar is running about $3/Watt installed, so if installed today the global system would cost $100 trillion dollars, which is slightly more than the gross world product (world GDP) of $78 trillion, which is $9,000 per person. However, those costs do not include a power grid, whether backed up locally or massively interconnected between different regions, so that the night side of the planet is drawing power from the sunlit side.Report
Thank you for the crunchy numbers.
I agree that the biggest hurdle today is a serious infrastructure program that moves the load from concentrated to distributed sources. Being able to get power from the places the sun is shining or the wind is blowing NOW is critical. It also has the advantage that it forces many nations to integrate their success with that of their neighbors as energy production becomes truly global.Report