Since accelerating the mass of the batteries raises the cost even further, batteries are even less efficient for urban transportation when you accelerate and decelerate a lot. We would need to bring back trolleys or another way not to have to transport the energy source for our cars to have something efficient.
Um, what?
Top of the line Lithium Ion batteries (they'll soon trickle down to automotive) are at about 240 Wh/kg, or 0.864 MJ/kg. Now, here's the cool thing about electric cars, you can get ~70%+ efficiency from battery to tire patch (aka, 70% of the power is used to move the car), and 80%+ fairly easily. Gasoline engines top out at around 25-35% efficient (Carnot efficiencies). Assuming a gasoline efficiency of 35% and electric car efficiency of 70%, you need half as much energy per kg storage capacity for electric cars.
The second cool thing about electric cars, regenerative breaking. You can recover around 70% of the energy from stopping as electricity and put it back into your battery. It is easily more efficient to use batteries/electric drive trains than gasoline in urban transportation. Why do you think hybrids get such great city mileage? This further reduces the storage density needed. Hybrid buses are awesome at city transportation, serial hybrids at any type of transportation are just epic. Electric drive train to maximize drive train efficiency, gasoline or other generator for range running at most efficient gearing.
I definitely agree with you there. Should simply be a meter that monitors and records power usage with remote viewing. No remote disconnect or any such.
There are undoubtedly a number of products you can install to do the same thing.
Touche. I think a small device that monitors your power usage and that the owner can connect to is a great idea. I don't know if smart meters in their current form are a good way to go about it.
Why do you feel they are an exceedingly dumb idea?
Who would've imagined that knowing you'd get a huge bonus anyway would make you work less/not as hard? The rest of us in the real world already know this.
You touch on another of the ideas that people are working on alongside efforts to make a high efficiency cell. While concentrator systems up cell efficiencies, the convertible spectrum is still limited by the cell. Some researchers, such as those at MIT as published last year, are working with dyes and other materials to re-emit the sunlight at a more cell friendly frequency, although this method too has major losses.
A second method not often mentioned here is called thermophotovoltaics. The idea is that you use concentrated light to heat up an element that then emits light at a different spectrum. To me, the cool idea about this is that if you can emit at the right range and get really high efficiency cells, somewhere down the line you might be able to replace the steam part of current power plants. Although that goes outside my realm of knowledge.
The issue with most cells' spectrum is that you need to shift the light up in frequency, not down, which is harder/more expensive. However, it could be useful if you could target the frequency at which the cell is most efficient.
I don't know exactly what the absorption and conversion rates are with the 40% efficient cells, but its safe to say it's very high. One of the biggest hurdles with solar cells is simply getting the charge out, getting the electrons and holes that are knocked out out of the semiconductor. It plays a very large part as to why current efficiencies are so low.
To hit 25+% efficient cells, in essence 3 cells were combined to create a multijunction cell that has 3 layers in series. To get to 30+%, refined deposition methods and clever semiconductor tricks were used. To get to 40+%, you need concentrated light and, in some cells, more layers of different materials.
The journal paper describes a simulated cell with a 14.5% efficiency and that it will compete with crystalline silicon cells - the middle of the pack for silicon efficiency and cost. The big advantage here is that the amount of semiconductor used is very low, which could make these cells very cheap. Another thing to keep in mind is that this method can potentially be applied to other, more efficient technologies, although there will be a few more hurdles should they go that route.
I very much like the idea of cheap solar cells, but it needs to be clear that this is not an efficiency breakthrough. But let me tell you, as a solar car alum, the idea of even a 40+% efficient non-concentrator cell gets me excited, even though this is not that.
There are many different factors that go into making a high efficiency solar cell. You need a front material that has very high transmittance/low reflectance at incident angles, a high absorption semiconductor, a high photon to carrier generation rate, high/easy carrier collection from the semiconductor, and broad spectrum conversion. These silicon-wire arrays appear to have high absorption and high carrier generation, but thats only part of the story. The other issue is that silicon misses out on a fair chunk of the solar spectrum. Anything after 1100nm is not converted, its simply below the bandgap.
The title of this post and the article is incredibly misleading and very annoying/frustrating to someone who's been working on solar technologies for a while. Don't get me wrong, I think this is a very cool thing, sounds like they have to potential to make very cheap cells, but approach, let alone surpass, current multijunction cells (30-40% eff.) they will not.
Disclaimer: University of Michigan Solar Car Team alum
So solar cells take a lot of energy to make, no argument there. But why is it always assumed that you're not making your cells with energy from other solar cells? No, the first cells weren't made using renewable energy, but who says we can't do that now? Imagine that, a renewable loop. Oh, and don't forget that you can recycle the solar cells at the end of their lifetime to make new ones.
Solar thermal can be up to 90% efficient? Have you heard of the laws of thermodynamics and Carnot efficiency? The average power plant peaks at about 60-65% efficient.
Sure, right now photovoltaics are only 15-30% for system efficiency, thats system, not just the cells. But PV is not restrained by the Carnot efficiency because it is not a heat engine. More demand = more research = better cells. Just look at the space grade cells and PV concentrator cells. World record right now is about 43% efficient.
Har har. Batteries aren't there just for when it gets sunny, they're a system backup. If something goes wrong with the solar panels, there's still a battery to supply power. The battery is also there to act as a buffer. Chances are at some point you will draw more power than the solar array can put out at a given time, so you need somewhere to store that power.
I realize now that you likely really are agreeing with me. If so, thank you for not being one of those oh-so-clever "what if its cloudy" people.
Since the ISS only has 120-130 Kilowatts of Solar Panels, running a 200 Kilowatt motor would be difficult.
I am sorry to go on a rant about this, but as someone who works on solar power on a daily basis, I am sick of people assuming that since something uses solar power to generate the electricity, that it will only work when the sun is shining. Ever heard of batteries? Do you honestly think that the ISS is up there, without batteries, which allow a system to draw more instantaneous power than the solar panels can supply, but can be recharged later when the system isn't drawing so much power?
I worked on the solar array for the University of Michigan Solar Car Team and people always thought that they were so clever when they said that it can only run when the sun is shining. God forbid a solar car or anything else solar powered have a battery!
Spectrolab has the solar cell world record with their triple junction GaAs cells at 40.7% at about 400x or 500x. Amonix Corporation has the silicon world record at 27.6% at approximately the same concentration level.
Current silicon cells are about 15-20% average efficiency, NOT 10-12%. They peak at just over 25% efficient as demonstrated by the research lab at the University of New South Wales in Australia.
SunPower A300 silicon cells average about 20% per bin.
The Dust to Dust report was based off standard Hummers.
While that 100 Miles per Gallon promise really sounds like BS the concept is interesting. What I'd like to know is how much further would the range be if the gasoline tank, ICE and generator were replaced with more battery packs to make it an EV instead of a hybrid.
Right, I don't know how accurate the 100MPG really is, but the concept, which was also done (don't remember if it was hybrid or pure EV) to an F150, with 4 in-hub electric motors.
I understand complaints about pure EV not having enough range (but come on, how often do you drive that far in one sitting?), which is why I support serial hybrids, or "range-extended hybrids". A parallel hybrid just makes no sense.
I think it was established as a well known fact that driving a Hummer is many times more environmentally friendly than a little Prius. If Obama was truly interested in saving the planet he would mandate that every commuter drives a Hummer and we scrap these pointless high MPG cars.
</sarcasm>
Depends on what Hummer you're driving. See below: "Hybrid Hummer Promises 100 Miles per Gallon"
Personally, I think parallel hybrids are incredibly stupid, ex. Prius. Series hybrids, where the combustion engine runs at its most efficient and charges the main drive battery, just make sense. A vehicle's MPG can be greatly increased simply by leveraging efficiencies. Electric motors are almost always more efficient than comparable ICEs, so why not run the ICE at its most efficient? There's nothing saying you can't have a smaller battery pack and run the ICE more, just run the ICE at its most efficient.
I'm not asking for a revolution, just intelligent engineering.
Instead of sending it back to earth, why not just keep it out there, but collect it all to one central location? We paid once already to launch it out there, and we know we want increase our space presence, so why not have a junkyard where you can go get stuff to recycle? Or, crash it into the moon and build your moon base near it, then you can keep adding to and utilizing it.
Computer labs are essential to any good engineering program. The smartest and easiest way to provide access to and support for an array of engineering software is through University run computer labs.
At the University of Michigan, where I attend, there is a huge amount of software that engineering students have access to on any of the CAEN (computer aided engineering network) computers. All my complaints aside, the engineering network is one of the most useful resources. I have a fair amount of University storage space, access to all my files on any CAEN computer, and generally a lot more computing power available than on most student's laptops.
Students will routinely run simulations and analyses on the computers, letting them run overnight, or even days. Above all, without an engineering computer network, student teams, such as Solar Car, FSAE, Baja, etc. would not be able to design, build, and compete on the same level.
A properly run computer network can be a great way to provide access to a huge resource with an array of software otherwise unavailable or too costly for students.
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Since accelerating the mass of the batteries raises the cost even further, batteries are even less efficient for urban transportation when you accelerate and decelerate a lot. We would need to bring back trolleys or another way not to have to transport the energy source for our cars to have something efficient.
Um, what?
Top of the line Lithium Ion batteries (they'll soon trickle down to automotive) are at about 240 Wh/kg, or 0.864 MJ/kg. Now, here's the cool thing about electric cars, you can get ~70%+ efficiency from battery to tire patch (aka, 70% of the power is used to move the car), and 80%+ fairly easily. Gasoline engines top out at around 25-35% efficient (Carnot efficiencies). Assuming a gasoline efficiency of 35% and electric car efficiency of 70%, you need half as much energy per kg storage capacity for electric cars.
The second cool thing about electric cars, regenerative breaking. You can recover around 70% of the energy from stopping as electricity and put it back into your battery. It is easily more efficient to use batteries/electric drive trains than gasoline in urban transportation. Why do you think hybrids get such great city mileage? This further reduces the storage density needed. Hybrid buses are awesome at city transportation, serial hybrids at any type of transportation are just epic. Electric drive train to maximize drive train efficiency, gasoline or other generator for range running at most efficient gearing.
I definitely agree with you there. Should simply be a meter that monitors and records power usage with remote viewing. No remote disconnect or any such.
There are undoubtedly a number of products you can install to do the same thing.
Touche. I think a small device that monitors your power usage and that the owner can connect to is a great idea. I don't know if smart meters in their current form are a good way to go about it. Why do you feel they are an exceedingly dumb idea?
I really don't know what to say to this other than wow. Seriously? Wow.
That's got to be the first time Australia got something first or at least before the States. Lucky bastard :)
What do you think we're stockpiling all our nuclear waste for? Refueling the Sun, of course!
Who would've imagined that knowing you'd get a huge bonus anyway would make you work less/not as hard? The rest of us in the real world already know this.
You touch on another of the ideas that people are working on alongside efforts to make a high efficiency cell. While concentrator systems up cell efficiencies, the convertible spectrum is still limited by the cell. Some researchers, such as those at MIT as published last year, are working with dyes and other materials to re-emit the sunlight at a more cell friendly frequency, although this method too has major losses.
A second method not often mentioned here is called thermophotovoltaics. The idea is that you use concentrated light to heat up an element that then emits light at a different spectrum. To me, the cool idea about this is that if you can emit at the right range and get really high efficiency cells, somewhere down the line you might be able to replace the steam part of current power plants. Although that goes outside my realm of knowledge.
The issue with most cells' spectrum is that you need to shift the light up in frequency, not down, which is harder/more expensive. However, it could be useful if you could target the frequency at which the cell is most efficient.
I don't know exactly what the absorption and conversion rates are with the 40% efficient cells, but its safe to say it's very high. One of the biggest hurdles with solar cells is simply getting the charge out, getting the electrons and holes that are knocked out out of the semiconductor. It plays a very large part as to why current efficiencies are so low.
To hit 25+% efficient cells, in essence 3 cells were combined to create a multijunction cell that has 3 layers in series. To get to 30+%, refined deposition methods and clever semiconductor tricks were used. To get to 40+%, you need concentrated light and, in some cells, more layers of different materials.
The journal paper describes a simulated cell with a 14.5% efficiency and that it will compete with crystalline silicon cells - the middle of the pack for silicon efficiency and cost. The big advantage here is that the amount of semiconductor used is very low, which could make these cells very cheap. Another thing to keep in mind is that this method can potentially be applied to other, more efficient technologies, although there will be a few more hurdles should they go that route.
I very much like the idea of cheap solar cells, but it needs to be clear that this is not an efficiency breakthrough. But let me tell you, as a solar car alum, the idea of even a 40+% efficient non-concentrator cell gets me excited, even though this is not that.
There are many different factors that go into making a high efficiency solar cell. You need a front material that has very high transmittance/low reflectance at incident angles, a high absorption semiconductor, a high photon to carrier generation rate, high/easy carrier collection from the semiconductor, and broad spectrum conversion. These silicon-wire arrays appear to have high absorption and high carrier generation, but thats only part of the story. The other issue is that silicon misses out on a fair chunk of the solar spectrum. Anything after 1100nm is not converted, its simply below the bandgap.
The title of this post and the article is incredibly misleading and very annoying/frustrating to someone who's been working on solar technologies for a while. Don't get me wrong, I think this is a very cool thing, sounds like they have to potential to make very cheap cells, but approach, let alone surpass, current multijunction cells (30-40% eff.) they will not.
Disclaimer: University of Michigan Solar Car Team alum
So solar cells take a lot of energy to make, no argument there. But why is it always assumed that you're not making your cells with energy from other solar cells? No, the first cells weren't made using renewable energy, but who says we can't do that now? Imagine that, a renewable loop. Oh, and don't forget that you can recycle the solar cells at the end of their lifetime to make new ones.
Solar thermal can be up to 90% efficient? Have you heard of the laws of thermodynamics and Carnot efficiency? The average power plant peaks at about 60-65% efficient.
Sure, right now photovoltaics are only 15-30% for system efficiency, thats system, not just the cells. But PV is not restrained by the Carnot efficiency because it is not a heat engine. More demand = more research = better cells. Just look at the space grade cells and PV concentrator cells. World record right now is about 43% efficient.
Har har. Batteries aren't there just for when it gets sunny, they're a system backup. If something goes wrong with the solar panels, there's still a battery to supply power. The battery is also there to act as a buffer. Chances are at some point you will draw more power than the solar array can put out at a given time, so you need somewhere to store that power.
I realize now that you likely really are agreeing with me. If so, thank you for not being one of those oh-so-clever "what if its cloudy" people.
Since the ISS only has 120-130 Kilowatts of Solar Panels, running a 200 Kilowatt motor would be difficult.
I am sorry to go on a rant about this, but as someone who works on solar power on a daily basis, I am sick of people assuming that since something uses solar power to generate the electricity, that it will only work when the sun is shining. Ever heard of batteries? Do you honestly think that the ISS is up there, without batteries, which allow a system to draw more instantaneous power than the solar panels can supply, but can be recharged later when the system isn't drawing so much power?
I worked on the solar array for the University of Michigan Solar Car Team and people always thought that they were so clever when they said that it can only run when the sun is shining. God forbid a solar car or anything else solar powered have a battery!
Preview? What's that? Never heard of it.
Spectrolab has the solar cell world record with their triple junction GaAs cells at 40.7% at about 400x or 500x. Amonix Corporation has the silicon world record at 27.6% at approximately the same concentration level.
Current silicon cells are about 15-20% average efficiency, NOT 10-12%. They peak at just over 25% efficient as demonstrated by the research lab at the University of New South Wales in Australia.
SunPower A300 silicon cells average about 20% per bin.
all these mod points come from?
The Dust to Dust report was based off standard Hummers.
While that 100 Miles per Gallon promise really sounds like BS the concept is interesting. What I'd like to know is how much further would the range be if the gasoline tank, ICE and generator were replaced with more battery packs to make it an EV instead of a hybrid.
Right, I don't know how accurate the 100MPG really is, but the concept, which was also done (don't remember if it was hybrid or pure EV) to an F150, with 4 in-hub electric motors.
I understand complaints about pure EV not having enough range (but come on, how often do you drive that far in one sitting?), which is why I support serial hybrids, or "range-extended hybrids". A parallel hybrid just makes no sense.
I think it was established as a well known fact that driving a Hummer is many times more environmentally friendly than a little Prius. If Obama was truly interested in saving the planet he would mandate that every commuter drives a Hummer and we scrap these pointless high MPG cars. </sarcasm>
Depends on what Hummer you're driving. See below: "Hybrid Hummer Promises 100 Miles per Gallon"
http://www.wired.com/autopia/2009/04/behold-americas/
Personally, I think parallel hybrids are incredibly stupid, ex. Prius. Series hybrids, where the combustion engine runs at its most efficient and charges the main drive battery, just make sense. A vehicle's MPG can be greatly increased simply by leveraging efficiencies. Electric motors are almost always more efficient than comparable ICEs, so why not run the ICE at its most efficient? There's nothing saying you can't have a smaller battery pack and run the ICE more, just run the ICE at its most efficient.
I'm not asking for a revolution, just intelligent engineering.
I don't need something that will play the game for me. What fun is that?
No, what I really need is something that will help me rack my balls quickly.
What size rack do you prefer? A, B, C, D, DD? Assorted variations therein?
I read that as "Skin your balls quickly with pool-cue robots." I quickly became concerned until my brain pointed out the pool-cue part of the title.
Instead of sending it back to earth, why not just keep it out there, but collect it all to one central location? We paid once already to launch it out there, and we know we want increase our space presence, so why not have a junkyard where you can go get stuff to recycle? Or, crash it into the moon and build your moon base near it, then you can keep adding to and utilizing it.
It's a LOAN, not a bailout. You have to pay back loans. College students get them all the time, but you don't see people complaining about them.
Computer labs are essential to any good engineering program. The smartest and easiest way to provide access to and support for an array of engineering software is through University run computer labs.
At the University of Michigan, where I attend, there is a huge amount of software that engineering students have access to on any of the CAEN (computer aided engineering network) computers. All my complaints aside, the engineering network is one of the most useful resources. I have a fair amount of University storage space, access to all my files on any CAEN computer, and generally a lot more computing power available than on most student's laptops.
Students will routinely run simulations and analyses on the computers, letting them run overnight, or even days. Above all, without an engineering computer network, student teams, such as Solar Car, FSAE, Baja, etc. would not be able to design, build, and compete on the same level.
A properly run computer network can be a great way to provide access to a huge resource with an array of software otherwise unavailable or too costly for students.