‘Solar’ jet fuel made out of air
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My envelope calculations show that we would need 8,334 km^2 (roughly 3% of Nevada) of plant space at 20k liters/day to roughly cover global jet fuel consumption. (I welcome sanity checks on this math.) That's actually an encouraging and apparently achievable number.
Happy to be corrected, just commenting for the sake of discussion. This is how I understand the 'efficiency' of such experimental energy to be determined.
If the entire world worth of jet fuel was obtained from Nevada, it would inject around 4 billion dollar per year into Nevada's economy, or around $1500 per capita every year. I can imagine them choosing the money over the land.
I used Nevada as an example because it's a low population density, highly undeveloped, sunlight-rich state, which makes it ideal for solar production plants. I'm sure other production facilities will spring up in the California desert and similarly situated regions around the world.
What excites me most about solar energy plants is that it's ideal for our empty desert regions - Lots of sunlight, lots of undeveloped land, low population.
Edit: The $4 billion figure seems off. If global demand is 60 billion liters, that's $45.6 billion at $0.76/liter. Am I missing something?
http://www.indexmundi.com/energy.aspx?product=jet-fuel&graph...
I think the difference comes from global vs US numbers.
However the first fusion plants, will probably dump excess production in the form of dense hydrocarbons for all the reasons listed here (lowers CO2 footprint, saves production energy for 'later', can be easily transported.)
http://www.dtic.mil/cgi-bin/GetTRDoc?doc=GetTRDoc.pdf&AD=ADA...,
http://en.wikipedia.org/wiki/Carbon-neutral_fuel#Renewable_a...
You can see why the technology would appeal to the US Navy, even if it's not quite price-competitive with other means of getting jet fuel: they're keen to untether their carrier groups from the supply chain as much as possible, which is partly why they have the convenient nuclear reactors already.
Carrier operations require operating at near flank (top) speed for takeoffs and landings. You couldn't fight and fuel at the same time. Even task-switching between modes would be at best cumbersome.
The US NRL's own research materials propose a fixed-site pilot, perhaps powered by OTEC (ocean thermal energy conversion) as a renewable energy source (this provides constant 24/7 power based on sea temperature gradients from sites such as the Hawaiian Islands with proximate shallow and deep-water zones at large temperature differential). Similarly any electrical power source, most conceivably renewable solar or wind, or nuclear, could be used for fuel synthesis. My back-of-the-envelope calculations suggest that supplying the equivalent of present-day US petroleum consumption would be plausible. It would require a few thousand km^2 of solar capacity, a roughly 10m tall by 4.5m square processing plant, and capital of roughly $8 trillion (based on USNRL's estimates) for synthesis and likely 1-2x that for the solar capacity.
In either case, you'd still have tankers and tenders transporting fuel, what you'd eliminate is the specific reliance on routes from existing petroleum extraction and refining sites.
Overall efficiency should be vastly better than the levels discussed here. Limiting point seems to be hydrogen electrolysis, which is 60% efficient (in terms of hydrogen energy potential) based on existing operational data. The Fischer-Tropsch reaction is pretty low in energy demand, or net positive. There are _vast_ volumes of seawater which would have to be processed, and pumping of that could be a significant energy cost (or perhaps tidal flows and some clever one-way-flow solid-state valves could be used to accomplish this: http://makezine.com/2012/01/05/the-tesla-valve-one-way-flow-...).
It's not clear to me what the actual efficiency of the USNRL's method would be, though it seems clear that 60% net energy recovery is a theoretical maximum. I'd suspect 20-50% might be reasonably attained -- and that's far, far higher than the 1.7% claimed by the article referenced by this HN post.
How do they compare to the space available inside and on top of the latest post-Panamax container ships? Even having a handful of ships like that (with their own nuclear reactors) trailing after the carrier to supply the requirement might be somewhat viable.
Already rising fuel costs have vastly affected the industry. US "peak aviation fuel" occurred in 1999. Peak departures was in 2005. 2012 consumption is _half_ of what was forecast in 2000, and departures 30% of the trend as of 2005 (even allowing for recession).
I first ran into this fact in January while looking into a biofuel "breakthrough" touted by Boeing (breakthrough or not it's wholly inadequate for needs): http://redd.it/1wo2hl
The departures data comes from a presentation by Steven Kopits made in February which I didn't come across until April: http://energypolicy.columbia.edu/events-calendar/global-oil-...
While passenger miles are still up, net, from 2000 levels, that's only on account of more efficient aircraft and higher load factors (that reduced legroom isn't just in your head).
So that's the problem scope.
Electricity is largely a solved problem: we can generate it with solar, wind, geothermal, hydro. Even nuclear for some bridging potential (though fuel availability even for thorium is decidedly limited as I calculate it http://redd.it/23nvqs).
Other than air travel, most transport needs are also tractable. Personal transport can be addressed via denser development, bicycles, electrified mass transit, personal electric vehicles, and other means. Rail can be electrified. Drayage (non-rail overland transport) is trickier, but might be addressed through EVs, biofuels, and even animal locomotion in a pinch.
Ocean shipping might return to use of sail or solid biofuel in the form of pelletized fuels.
But you cannot fly planes which carry appreciable cargos of people or freight useful distances reliably at speed without liquid fuels. So addressing that is of interest (an alternative would be to forgo flight or switch to lighter-than-air craft).
Personally I find the prospect of seawater-based fuel synthesis far more likely than air-based technologies: much richer carbon source, and likely far higher efficiencies.
This is like spending effort for cufflinks when it's -20 C and you aren't wearing any pants. Pants first. Cufflinks later.
Edit: I didn't type it because I thought it was obvious, but this would be producing fuel for rockets and other vehicles operating in exploration, not for bringing back to Earth to put in your car.
Of course there is also batteries (metal-air) with 10x capacity vs. current lithium-ion - in couple years they may make even the above mentioned fuel cell improvements obsolete.
http://www.esa.int/Our_Activities/Space_Science/Venus_Expres...
icy/carbonaceous Asteroids on the other hand in the same orbit would be gold.
>> negligent amounts of oxygen
Yeah, I've heard that the oxygen on Venus doesn't pay attention to anything and is generally untrustworthy. Stupid negligent atoms! ;-)
I thought there was too little h2o on Venus for plant life.
Chemical fuels have a great energy density. Problem is, they dump carbon into the air when you burn them (and also basic pollutants).
So we just need:
1) fusion or similar "lots of 'free' energy"
2) a process like this to soak up that energy + CO2 + H2O and emit nice energy dense hydrocarbons
3) decent catalytic convertor/filter tech (we're pretty good on this at the moment when we want to spend the money?)
then we've got a long-term energy future.
Exactly!
> So we just need: 1) fusion or similar "lots of 'free' energy"
Utilizing geo, hydro and solar (carpeting them in inhospitable areas) and fission is enough. Fission is particularly effective, the energy yield per kg of fuel for fusion is only 4x that of fission. Between less wasteful alternate reactor designs and extracting fuel from the ocean, if we start figuring things out now, things will be fine.
> 2) a process like this to soak up that energy + CO2 + H2O and emit nice energy dense hydrocarbons
This is well studied by the US Navy and others. It's especially cost effective when drawn from the ocean. Wikiterms: 'sabatier reaction', 'power to gas', 'carbon neutral fuel'.
> then we've got a long-term energy future.
We're still going to have to act quickly, before the energy (and resources) required to initiate this industry is more than could be had with the then current reserves. A true debt. Thus squandering the selfless sacrifice made by dinosaurs many kilomillennia ago in order that we at least could bootstrap a space faring civilization.
The USAF would love to not have to worry about the long-term availability of fuel oil, and just depend on a desert array of concentrators somewhere in the US.
Wind -> coal (1850s) -> Oil (1910s/1920s) -> Nuclear (1950s)
And now hybrid and synthetic fuels.
Much of the more interesting peak-oil / collapse literature comes from military organizations, including in the US, Germany, and UK.
We're still going to have to act quickly
That would be a true tragedy....
And it wasn't dinosaurs so much as algae and ancient plants, as well as the forebearance of the bacteria of that time to break down the material.
If these solar plants just fed the electricity into a well built power grid, the coal plants could be turned off and a huge amount of CO2 would be left unemitted.
Coal is unbeatable as a carbon storage method, and what's best, it's free as it already is in the ground, we just have to leave it there!
I'm sorry to say, but most of these energy schemes just make many people who understand anything about power generation cry.
It's like to an IT guy, some client suggested you ran their enterprise databases on an Arduino over Bluetooth, because they heard it's a cool new thing.
The scientists and engineers have no illusions that this method will be used for general energy generation. This is for a niche application. And the 'sequester carbon from the air' part? All they care about is that its carbon neutral.
And honestly, it's pretty smart. Pretty much a guarantee way to get defense funding all around the world.
Probably a more practical way to store energy, and in my mind the most likely way to power vehicles, is compressed air at 300-700 atmospheres, which is within the same order of magnitude energy/mass density as batteries, depending on the storage tank:
https://en.wikipedia.org/wiki/Energy_density
A solar plant can be built on top of an empty natural gas well and store energy in compressed air underground. Another possibility is compressed air in large bags at the bottom of the ocean, that would displace less water than a dam since the height difference can be several thousand feet (pumping water uphill is not very effective due to the elevation required). We’ll also never have enough batteries or supercapacitors to store that much energy.
I wish I had money to invest in fiberglass or carbon fiber wrapped storage tanks and micro turbines/pistons that convert the energy in compressed air to rotational energy. I think we’ll be using them instead of something more exotic like magnetic bearing flywheels, and future electric cars will have a small natural gas/hydrogen turbine that tops off an air tank that will take the car 10 or 20 miles without having to tap into batteries. Also, refilling air tanks at a fueling station can happen almost instantly, at least as fast as filling up with gasoline.
Still, I think making hydrocarbons is an exciting development for distributed generation, where people are only making a few liters of fuel a day from water basically. I imagine that it might be more efficient to make propane also, and this is a little off topic but propane engines are much easier to build/more efficient because they don’t have carburetors or fuel injection. I’m honestly surprised the world went with gasoline and diesel, although it was probably for safety reasons.
http://m.youtube.com/watch?v=z0_nuvPKIi8
http://youtube.com/watch?v=z0_nuvPKIi8
Focal point gets to > 3500 celcius.
Consider heating a teaspoon of water vs heating a pot of water.
For what it's worth they melt steel within a few seconds of putting it in the focal point and melt rock similarly fast.
Tantalum hafnium carbide melts at 4215°C.
It'll start reacting with things depending on what it's surrounded by at much lower temperatures then that.
If it is, there would be a public incentive to fund development and plants of such a nature vs funding carbon neutral or carbon positive energy ventures.
http://en.wikipedia.org/wiki/Carbon-neutral_fuel#Demonstrati...
To be honest this sort of technology would be better used for recycling agriculture fertilisers.
The broad outlines of a potentially sustainable high-energy-yield future are well known. Solar is the clear standout winner, hydro, wind, geothermal, and possibly some biomass may contribute. Liquid hydrocarbon fuels synthesis via Fischer-Tropsch, Sabatier process, or similar processes looks potentially viable, and water as a feedstock for both hydrogen and carbon seems tractable.
It's not easy or cheap, but it's possible.
As for the billions -- I suspect that a future stable wealthy population level will indeed be some billions fewer than live on Earth today.
Billions is not an incredible amount of money. Fusion research has been horribly underfunded and has and is making great strides.
http://focusfusion.org/index.php/site/reframe/wasteful
So 27B USD (inflation adjusted) in funding over the history of fusion. Pennies.
http://nationalpriorities.org/cost-of/
Estimates for the total cost of the wars is around 4T USD with the current dollar cost of 1.5T USD. In Seattle we are building a 2 mile long tunnel for 4.25B. Our tunnel is 7% of the lifetime fusion budget.
We don't need solar and fusion to solve our fuel problem. We need solar and fusion to pull carbon back out of the atmosphere and the oceans.
Population has absolutely nothing to do with carbon output levels. North America and Europe account for the majority of carbon output and 20% of the worlds population.
edit: fixed number
Billions with nothing to show for is.
Fusion energy is the first seriously pursued energy source which has never been proof-of-concepted for more than a few million dollars, and its only competition there is nuclear fission. Even there I suspect that the first criticality would have been achieved at even lower cost. I'm digging for references, though AFAIK first human-triggered criticality was at the University of Chicago in 1942 under Enrico Fermi (I'm not sure if earlier radiation workers achieved criticality). I can't find budgetary amounts for that project, but the entire Manhattan project was $26 billion in 2014 dollars, and it delivered sustained chain reaction, working reactors (at the very beginning of the project), and an actual stockpile of working weapons, two of which were used in combat.
By contrast, fusion research, while providing weapons, has not succeeded in delivering sustained net-energy-positive reactions.
And every single prior external energy source humans have utilized has been proven on a budget of at most a few dollars, if not freely in nature: agriculture, wood fire, coal, oil, gas, water, wind, solar, geothermal, wave, tide.
Another distinction which occurred to me some time back is that fusion is the first (on Earth) non-chain-reaction type material-based energy source.
That is: all other energy sources involving transformation of matter (whether by conventional molecular or nuclear chemistry) will proceed by themselves under proper conditions in which energy is sufficiently reflected or retained at the point of reaction.
In the case of solid fuels, a fire is achieved by piling fuel such that airflow is permitted (providing necessary oxygen), while the heat of burning embers is contained to allow more fuel to participate in the fire. Many sufficiently volatile fuels will burn without much or any concentration (e.g., candles, matches, twigs), though a coal or log fire generally requires _some_ assembly. Those conditions are readily and directly observable in nature.
Similarly, sustained nuclear fission is accomplished by ensuring that emitted neutrons have a sufficient likelihood of striking more atoms that the reaction is sustained. This is easy enough to achieve that nuclear industry workers have to take pains to not accidentally create critical masses of fissible materials (a task at which there have been multiple failures).
Wind, water, and solar energy demonstrations and practical application all pre-dated the Industrial Revolution.
By contrast, fusion technologies are all based on the principle of feeding more energy into the reaction chamber to continue the reaction, and absent that very active feedback (through very complex means). It's only when you, very literally, achieve stellar magnitude concentrations of mass that fusion occurs naturally at rates sufficient to provide substantial amounts of energy. And even the Sun, a third of a million times as massive as Earth, only undergoes hydrogen fusion at a rate per unit mass roughly equivalent to reptile metabolism. You, as a mammal (I presume), are releasing four times more energy per unit mass than the Sun is. The Sun just happens to be slightly more massive than you (or, of course, your mother -- or mine).
While exothermic fusion has been achieved on Earth, it's not been controlled, sustained, or utilizable for productive energy use. And I really don't see that changing.
When you contrast the billions to trillions in research that would have to be spent simply researching useful fusion technologies with the amount of actual energy infrastructure which could be constructed with an equivalent expenditure based on solar, wind, geothermal, and liquid fuels synthesis (among other known and proven technologies), there's really no argument in my mind.
Keep ticking the research along at low levels, sure, but in the near term (the next decades to century or so) we really have an exigent need that should be fulfilled first.
Finally: "Population has absolutely nothing to do with carbon output levels" is flat-out false, and misses the point. The accepted formula is in fact dependent on population, but also affluence and technology: I = P × A × T
That is: impact (including CO2 emissions) is a function of population, affluence (net resource consumption), and technology. https://en.wikipedia.org/wiki/I_%3D_PAT
The other problem is that it's not just CO2 emissions but total carrying capacity which are limited, as exemplified by "peak everything": oil, water, topsoil, phosphorus, uranium, copper, and many other inputs to both industrial and nonindistrial human existence. Estimates of what specifically a long-term sustainable carrying capacity might be vary, but a number that has been suggested (by the Ehrlichs among others) is around 2 billion. Last I checked we'd exceeded that slightly, and there might be a recruitment of volunteers in the near future.
I am not sure I fully understand your argument. Some energy storage, exploitation and transport mechanisms are as easy as falling off a log. That a continuous fission reaction occurred in 1942. Yeah using a pile of bricks. It also has been occurring naturally in Africa, http://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor what does that have to do with limitless energy that will flow from a fusion reactor? How much has been spent on the oil economy in total? That number has no bearing on my argument either.
I am not sure what
| billions to trillions in research that would have to be spent simply researching useful fusion technologies
actually means. Sounds like throwing up the dangerous boogie-man of unknown costs. The US has spent ~30B in total on fusion research. And on ITER we will be contributing only 9% of the total, the same amounts btw as South Korea and India. Yes, further fusion research will cost billions, not trillions. I don't dispute that further research, it simply isn't that much money. At this point the billions is beneficial just for the science and engineering advancements.
Back to my original point is that these billion dollar numbers are paltry, that the perceived risks and dangers posed by Iraq and Afghanistan are also inconsequential compared to total collapse of the worlds oceans, drought and farm land loss by global warming. We wasted trillions of dollars, a small part of which could have funded human race saving science.
Of course population effects carbon output. The poorest 3 billion people on the planet will pay the price of the carbon output from the top 1 billion. It is the 1% of the western countries that will survive while the rest of humanity dies in trash heap of civilization.
We don't simply have an energy problem. That could easily solved with existing renewable tech. We have massive carbon problem that most likely can only be reversed by the massive power output of fusion power.
I'd actually converted my earlier posts in this thread to a post (http://redd.it/24pnw6), in the process of which I turned up some more relevant funding details: the amount spent on fusion (about $29 billion in constant 2014 dollars) is roughly 25% of all US energy research spending (another significant chunk has been spent by way of tax benefits and incentives). Which is to say, again, a lot has been spent on this.
In terms of actual energy investment, that is, not research but capital expenditures in developing existing energy systems, the number is about $5 trillion, worldwide, spent on conventional petroleum development from 2005 - 2012, according to Steve Kopits (http://energypolicy.columbia.edu/events-calendar/global-oil-...). which is to say, we've got a baseline for what we're spending on real, present energy development.
That's also on the order of the capital expenditure which would provide, based on present-day, known, proven, and commercially deployed technologies, a sustainable energy infrastructure. Not pie-in-the-sky, 50 years out, might-work-we-think stuff, but Shit. That. Works. Now.
What's your best / most likely fusion technology? How long's it been in development? How far is it from break-even?
One of the reasons I think more people should be looking at solar-thermal rather than solar cells
My company, LightSail Energy, is developing precisely this technology.
www.lightsail.com
We're also developing the world's lowest cost pressure vessels to store the air.
I wish you had the money to invest in us too ;-)
I've seen repeated mention of this in various sources, but no explicit quantification.
This means no working pure compressed air energy storage tech is in existence today -- a couple exist which add heat via combustion, one product used to exist which used an electric heater to keep a heat store warm. Both are thermodynamically non-ideal.
Based on pure theory, however, running two stages of compression to 200 bar (14.1:1 each), running perfectly adiabatically during compression and expansion, temperatures would reach to about 600 C during compression. If one didn't recover the heat of compression, and let the temperature of the compressed air drop to ambient, the temperature upon expansion would get to about -170 C. Pure thermal efficiency would be about 34%.
The results are so extreme / bad that one would choose a whole separate set of parameters and compromises. But that should show you the power of direct contact heat exchange.
I've seen some discussion of CAES using former natural gas wells for storage. I don't know the scale of operations there, but it could be large (meaning that relatively small amounts of energy would be stored or extracted at any given point in time.
Rock also serves as a pretty good insulator (R5 as I understand, and there's a lot of it), which might preserve some of the heat of compression.
In your example, is 200 bar a typical pressure for CAES? I see that as about 2900 psi for the imperial units types.
Salt caverns melt at high enough temps (above 200 C) and injecting hot air into a methane reservoir is not terribly advisable...
The constraints you raise on natural-formation CAES do raise some interesting challenges (or Hollywood movie plots).
Can you do any maths on that concept and determine the size of the rafts which would produce usable energy consistently?
There is a lot of power in waves, but one thing to keep in mind is that the amount of extractable energy is proportional to the head (height difference):
https://en.wikipedia.org/wiki/Hydroelectricity
http://www.reuk.co.uk/Calculation-of-Hydro-Power.htm
https://en.wikipedia.org/wiki/Low_head_hydro_power
https://en.wikipedia.org/wiki/Tides#Example_calculation
http://www.infoplease.com/encyclopedia/science/tide-the-magn...
So a dam uses a high head/low flow rate, and tidal or wave power uses a low head/high flow rate.
I’ve seen a few dams built around coves that work like a lock, filling up at high tide and draining during low tide, running a turbine to generate electricity. But if there is only a 1 or 2 meter head, it takes a huge water current to make more than a few MW.
I’ve also seen these snake-like creations that are big floating drums with hydraulics between them, that bend with the waves. So the head is about the same, but the period is a few seconds instead of a day, so a lower current is needed. However, the amount of current they capture is so small compared to a dam that they only generate on the order of a few kW.
The idea of using a large float is certainly compelling. Off the top of my head, maybe it could work similarly to having a bag at the bottom of the ocean with a pipe connected to an artificial floating island on the surface. It would pull on the bag as the tide rises to inhale air into the bag, and then let it exhale as the tide falls. A turbine in the tube would generate electricity in both directions. Water weighs 1000 kg per cubic meter (62.5 pounds per cubic foot), so if we use the dam formula for 1 cubic meter and +/- 1 meter of tide, the float would travel 1 m up, 1 m back down, then 1 m down and 1 m back up, for a total distance of 4 meters every 24 hours. So I think we can use the dam formula:
power P = phrgk
density p = 1000
height h = 4
flow rate = volume/time = r = 1/(60 * 60 * 24) = 1.16e-5
gravity g = 9.8
efficiency k = .6
so:
P = 1000 * 4 * 1.16e-5 * 9.8 * .6 = 0.27 W/m3
As a sanity check, the amount of energy required to raise 1000 kg of water 4 meters is:
E = mgh = 1000 * 9.8 * 4 = 39200 J
So power is energy over time, so:
P = E/t = 39200/(60 * 60 * 24) = 0.45 W/m3
So at 60% efficiency, power = 0.27 W/m3
This is one of the reasons why the head is so important, because it takes remarkably little energy to raise a ton of water, literally.
So if we want a 1 MW plant, we’d need a float about 3.7 million cubic meters, which would be a sphere with a radius of about 100 meters by V = (4 * pi * r^3)/3, or about 600 feet across. It would also need a bag of similar volume anchored to the bottom of the ocean.
Since the pressure is reversed for the bottom balloon, it would take on the shape of a tetrahedron, so would need strong anchors holding 3 corners to the ocean floor, with one of the corners connected to the float by a tube. The 3 edges touching the floor would need to be sealed against water leaking in. A bit of an engineering feat..
To make it worth our while, we’d probably want a float 1000 times bigger, or 6000 feet across to generate 1 GW. I have a little trouble picturing a mile wide float, its surface area would be:
Area = 4 * pi * r^2 = 4 * pi * 1000^2 = 12.6 million square meters
Although this doesn’t seem that bad, even at a cost of $10 per square meter.
Now that I write this, maybe a better alternative to the bottom bag would be a steel cable connected by a pulley to the ocean floor, that comes up on land and moves a meter or two forward and back each day. It could either be connected to a hydraulic system with a thin (high flow rate) tube, or perhaps a high gear reduction transmission that converts the motion to say, 60 Hz or something.
Unfortunately we’re talking 4 trillion kg of tension (4 billion m3 * 1000 kg per m) for a 1 GW plant, and a steel cable to carry that tension is infeasible, at 7500 kg per square cm (75 million kg per square m) of cross sectional area, which I calculated from the 11.5 mm cable which works out to a 1 cm2 cross section at 16540 lb (7500 kg):
http://www.engineeringtoolbox.com/wire-rope-strength-d_1518....
So when it’s all said and done, it’s possible to build the float but I don’t know how the power could be extracted practically.
Why?
Because the energy is derived from the tidal rise, not the amount of water you're displacing. The relevant volume is the area x the tidal displacement, which gives you the amount of water and how far it's been lifted (average: 1/2 the total displacement).
Or, if you prefer to have someone do the math for you, the City of San Francisco and EPRI did an analysis of how much total energy could be derived from tidal flows in and out of the San Francisco Bay, which I became interested in after an Internet crank suggested that the rise and fall of 30 typical ships could power all of San Francisco.
Not hardly.
http://oceanenergy.epri.com/attachments/streamenergy/reports...
The narrow passage under the Golden Gate Bridge, which connects the San Francisco bay to the Pacific Ocean is home to some of the most energetic currents in North America. In average 237MW of power is embodied in the tidal stream, of which about 35MW could be extracted without any negative impact on the environment. A plant of that scale could reach an electrical output of about 100MW at peak.
http://www.sfenvironment.org/article/hydro/tidal-energy
The study conservatively estimated that the Golden Gate site has 35.5 megawatts of total extractable average annual power, and that 15 to 17 average megawatts (MW) of this power could realistically be extracted by technologies currently in development. The cost of electricity generated, assuming incentives similar to those provided to other renewable resources, is estimated at six to nine cents per kilowatt-hour (kWh)—a cost competitive with current wind and natural gas generation, and about one-third the cost per megawatt of solar power.
As I recall, this works out to maybe 10% of the average power utilization of San Francisco proper, and a minuscule fraction of the energy used by the greater Bay Area. You'd do better to plaster the Bay with solar panels.
More: http://redd.it/1wefio
Tidal and wave energy are prodigious on a global scale, but they're simply too dispersed and too expensive to collect for present industrial-scale levels of energy use.
The minimal requirement is that the float, well, float. Other than that, more material is simply excess cost to consider.
The EPRI study I mention is based on, IIRC, turbines installed at the gate. Maximum capture would require building a barrier dam, which has been done at a few limited sites, though it would be impractical in SF due to ship traffic requirements.
https://en.wikipedia.org/wiki/File:Pulley3a.svg
A 200 m (600 ft) diameter, 4 million m3 float, generating 1 MW, would have a tension of 4 billion kg. That would need 533000 pulleys with 1 cm2 steel cable at 7500 kg tensile strength. So 266000 pulleys on each end, which is a 2D array of about 512 pulleys on a side. This doesn't actually seem that difficult to build on an industrial scale. The cable would travel about 2100 km a day, at 25 m/sec (about 55 mph). The cable would have a total volume of 2100000/10000 = 210 m3, or 6 m on side (20 ft), with the ends connected to the opposite sides of the pulley system. So that's quite a spool at the generator. It should be slightly mobile, either on wheels or a spring so that it can adjust to rogue waves. Also it should probably be made from a polymer that's resistant to seawater instead of steel.
Unfortunately we'd need 1000 of these plants to make 1 GW. Just goes to show how mindbogglingly much power humanity uses. Maybe we could at least try to conserve haha.
In 5 years, people will laugh at the idea of using compressed air instead of just storing electrons. I imagine battery energy density will have doubled by then.
The best available battery techs (generally metal-air designs which consume the anode) offer about 1/10 the energy storage density of liquid hydrocarbon fuels. The best of these, lithium-air, offers a theoretical maximum of 11140 wH/kg (40 MJ/kg), excluding oxygen weight, which is actually close to that of gasoline, diesel, or fuel-oil (~46 MJ/kg).
But at practically attainable levels for rechargeable designs, you're down to 9 MJ/kg, and on a gross energy-density basis, while sufficient for some uses, including a fair number of ground-transport uses, but with some significant operational and technical constraints imposed by the battery's own operation. You also have the further disadvantage of having to carry around the full weight of the battery even when its energy content has been exhausted (fuels by comparison are burned off).
For other uses, particularly large bulk-good transport (ground or sea), or practical heavier-than-air craft, it's simply not good enough.
And that's the best possible designs. For more viable designs -- LiON or even hypothetical graphene / carbon nanotube batteries, you're looking at vastly lower storage densities -- 0.36–0.875 MJ/kg for LiON.
The prospect of synthesizing hydrocarbons using electrical energy from renewable or sustainable sources strikes me as a highly probable future path, though I'm partial to the US Navy's fuel-from-seawater proposals, given the much higher (140x) concentrations of CO2 available in dissolved and bound (carbonate, bicarbonate) form. For more: http://redd.it/22k71x
For discussion of energy storage see generally Wikipedia:
https://en.wikipedia.org/wiki/Metal%E2%80%93air_electrochemi...
http://techland.time.com/2013/05/23/amprius-begins-shipping-...
This compares with 10,690 WH/l for liquid hydrocarbons (scaling a barrel of oil equivalent to liters and converting to watt hours).
That's roughly 5% the energy storage density of liquid fuels.
One issue I've found is that it can be expensive to concentrate CO2 from the air to feed into this process. For the first version, I would recommend putting it on the smokestack of a coal or natural gas plant, which is putting out majority-CO2. It's not getting us carbon neutral fuel, but it gets us double-use out of each CO2 molecule, and it makes the first version much easier to build.
So, assuming that most of the plant is low maintenance and not too expensive to manufacture it's not that bad. Certainly I don't think that turning corn into fuel is anywhere near as efficient.
One thing I want to ask right now, Will the ratio between the input carbon consumption and the carbon emission + residue remain the same in such a process?
It was festured in Daniel Suarez's Freedom, as the main fuel generator for a native self-sustaining community.
[1] https://share.sandia.gov/news/resources/releases/2007/sunshi...
sun / outer lens / pressurized gas / quartz lens from diagram / reactor
you could adjust the pressurized gas chamber pressure to match that of the reactor so that you're subjecting the quartz lens to a net zero bending moment/tension. ideally you could then make the outer lens out of something tougher than quartz and it wouldn't need as much high temperature strength since it's farther away from the reactor.
At current (retail) prices that's about 10,000GBP per day or 3.5M GBP per year. Doesn't sound like a lot to run a 1km sq. facility...
Briefly:
• It creates aviation-quality fuel (long-chain liquid hydrocarbons equivalent to kerosene or diesel fuel, longer than those in gasoline) from electricity, hydrogen electrolyzed from seawater, and CO2 present at 140x atmospheric concentrations in seawater in both dissolved (2-3%) and bound (97-98%) forms as carbonate and biocarbonate.
• It utilizes two very-well established and understood principles: electrolysis and Fischer-Tropsch process fuel synthesis.
• The novel aspect is also relatively conservative: extraction of CO2 at industrial levels from water via partial vacuum and pH changes induced largely via electrolysis.
• Efficiency looks to be reasonable and largely governed by electrolysis at 60% in terms of net recoverable energy from H2. Even if operational efficiency is only 10% of this it's still 3.5x more efficient than the method described in the article here.
• Scale of operations envisioned is significant at 100,000 gallons/day. Scaling this to national levels of present petroleum consumption strikes me as plausible, though not trivial or inexpensive. Capital costs are not incommensurate with existing and projected petroleum capex spends (trillions of dollars), and may provide greater return in terms of net energy supply.
• Plant requirements are, as fuel synthesis schemes go, profoundly modest. Rather than tens or hundreds of millions of hectares envisioned for biofuel schemes (along with freshwater and ag infrastructure requirements), a volume of roughly 10m x 4.5km x 4.5 km might provide US national liquid fuel needs. At envisioned Navy deployment levels, the plant would occupy a modest industrial site or possibly a shipboard or floating platform (though not fit within existing warship envelopes while preserving combat operations capabilities).
• Power requirements at 100kgal/day are ~240 MW (roughly an aircraft carrier's reactor output). At national scale, about 2 TW, or equivalent to a solar collector surface of roughly 6,700 km^2 (82 km on a side).
• The process should be highly amenable to utilizing surplus generating capacity on an intermittent basis to create fuel. It could be used for both electrical generation storage or for large-scale fuel synthesis.
• The technology isn't inherently large-scale. Smaller modular installations, or large centralized ones should, from an engineering perspective, be roughly equally viable, as contrasted, say, with nuclear technologies which are inherently centralized for engineering, safety, security, and operational reasons.
More: http://redd.it/22k71x