You mean the ones who keep shouting down anyone who dares question the science behind global warming, calling them mouth-breathing knuckle-draggers, even when some of those people doing the questioning are climate scientists? Yes, I agree. Reasonable voices are drowned out, on purpose.
Which Earth was used to conduct these experiments that provided the evidence?
The same Earth that was used to "conduct these experiments" which showed us that dinosaurs used to roam the Earth, that huge asteroids have hit our planet in the past, and that our planet is 4 1/2 billion years old. All fake too, I suppose?
You don't have to personally experience something to have compelling data that it exists. I didn't witness my own conception, but I'm pretty darned sure it actually happened and that I wasn't carried here by a stork or grew out of a head of cabbage. Why? Because all of the available data suggests that's how humans are born.
To go back to this case: there are many causes of climate change (all spelled out in the IPCC AR4, if you care to read it). The studies on each of them are presented, each with their own level of forcings and the confidence interval for each study. There are a wide variety of studies for each type of forcing -- for example, one paper might involve a physics model, while another might involve measurements using a satellite, another might involve a measurement using ground stations, another measurement using balloons with different instruments, and so forth. So you have multiple completely independent lines of evidence for the strength of each forcing. A consensus level of forcing and confidence interval is reached from each forcing. The consensus level shows that GHGs dominate the climate change forcings.
The other leading climate change forcings, such as land use changes, are clearly anthropogenic. But what about GHGs? There are several different approaches that study this. One is "old carbon versus new carbon"; carbon from coal, oil, etc has a different isotopic signature than carbon from decay and the like. Mind you, it's the same signature as with volcanism, but volcanism emissions are readily studied and are utterly dwarfed by manmade emissions. We catalog manmade emissions from different sources (with confidence intervals, of course), and that also shows that the overwhelming amount of carbon contributing to the relentless and steady rise is also anthropogenic and matches the rise very well in terms of magnitude over time. We look at changes in natural carbon sources and sinks and likewise quantify them. Furthermore, we not only look at totals, but where they're coming from; our latest satellites how have the resolution to see new carbon being added to the atmosphere and where it's coming from, and watch the anthropogenic plumes diffuse into the broader atmosphere. When you look at the numbers, there's no doubt where this new carbon is coming from; it's overwhelmingly anthropogenic, with nothing else even close.
Beyond all of this, we use a wide variety of physics models -- both global models and models for specific components. A model can be something as simple as a calculation of radiative heat transfer under different gas mixtures, or as complicated as something that models the sources and sinks over the entire planet and covers all of the various feedback mechanisms. Models are nearly all based on first principles in large part or entirity. Depending on the type of model, they're either validated with lab data or historic climate data.
All in all, the conclusion is the result of literally many thousands of peer-reviewed papers covering a wide variety of disciplines.
You do realize that the rate of warming at the end of the last glaciation is about two orders of magnitude than the rate of warming we're experiencing today, right?
Yes, the current rate has been experienced before -- the Paleocene-Eocene Thermal Maximum was the last analogous period. But that was 56mya. And anyway, I don't think we want to repeat it. It changed the world so much that we give the subsequent era a new name (the Eocene).
Replaced after a few years, huh? Then why are both Nissan and GM offering 8 year, 100,000 mile warranties on their non-titanate battery packs? And you don't *have* to replace them when the warranty runs out; that just means that's when they'll cover it for free.
People did the same sort of fearmongering about the Prius's battery. All unfounded.
I think the reason people always focus on battery lifespans is that they assume that all batteries behave the same way. But it's just not true. The reason that the batteries don't last long on your laptop or cell phone is that they're not engineered to last long. It's not expected that you'll have the device that long, and they know that consumers are more concerned with things like minimizing the size and weight of the battery pack. As a consequence, they use high energy density, low cycle life/longevity chemistries. They have no cooling systems (and often are put right next to heat sources). They use very high depths of discharge. They do little to no charge rebalancing between cells. And so forth.
1) Their numbers were inflated approximately 3-fold even when you account for their math error. Unless you're talking an electric Yukon or something. 2) Why would you rapid charge *at home*? The point of rapid charging is to allow for long trips. 3) That's what battery buffers are for.
To go with $150/kWh and 10,000 cycles out of a Vanadium-Redox battery buffer: that's ~67 kWh delivered per dollar of batteries, meaning a battery buffer capital cost of 1.5 cents per kWh of electricity you sell. Eminently affordable.
1. The Tesla Roadster has to go nearly 85mph to consume 30kW to maintain speed. At 50mph, it takes about 12kW. The Roadster is approximately equally efficient as the Leaf and Volt; it has a small cross section but a much higher drag coefficient.
2. A general number used to represent highway consumption for a typical efficient EV is 250Wh/mi. 200 miles range * 250Wh/mi = 50kWh. 90% of 50kWh in 5 minutes is 540kW. Aerovironment makes an 800kW charger. Now to be fair, most rapid charging systems don't exceed the lower hundreds of kilowatts, and some of the lower end ones (like Nissan is installing for the Leaf) are in the tens of kilowatts. The rough cutoff point for what is considered "rapid" charging and what is not is around 40kW.
3. Notice how dramatically different of numbers you got, despite your using 120kWh instead of 50kWh? You had a three orders of magnitude math error.
4. To go ahead and pre-empt it: No, you don't want to have everyone drawing hundreds of kilowatts straight from the grid. That would be a big grid destabilization and require massive hookups. The typical approach for such high power charging involves battery buffers, sized to ensure that you can statistically guarantee a given percent availability (99.99% or whatnot). And to pre-empt *that*: No, they're not prohibitively expensive. Neither are the chargers, although you do need (very roughly) the sort of utilization rates found at gas stations to justify their cost (a station of rapid chargers sharing a common buffer costs about the same as a gas station with a similar number of pumps). The chargers have the advantage of less maintenance, no need to take "fuel deliveries", and a dramatically cheaper "fuel". They have the disadvantage of lower throughput and the possibility of lower consumer price acceptance (since they're used to charging for so cheaply at home). You can also only support fewer stations from the same number of vehicles, since most charging is done slowly at home or at work.
5. To preempt something really stupid that gets mentioned every time: no, you don't rapid charge at home. Why would you need to be able to charge in 5 minutes at home? Can do you that with your gas car? Rapid charging is only needed for long trips.
6. Yes, 10 or 15 minute charges (a more realistic target for rapid charging of EVs, and ones that some EVs like the BYD F3DM and the Subaru Stella support) are slower than filling up a gasoline car. But not as much as you might think. The actual filling of the tank only takes about two minutes or so (depends on the pump, but there are legal limits to the maximum flow rate). But there's a lot of overhead to *every* type of fillup -- finding an offramp, slowing down, driving from the turnoff to the station, turning in, pulling up to a pump, turning the car off, unbuckling, getting out your money, getting out, taking off the gas cap, connecting the vehicle, selecting the fuel type, selecting the payment method, starting filling, stopping filling, reattaching the gas cap, hanging up the pump, paying, taking the receipt, getting back in, putting your seatbelt back on, and all of the driving/decel steps in reverse, plus a lot of little random things. I timed it for a while and found that the whole process sets me back an average of about 9 minutes. So going from a 2 minute fill to a 10 minute fill isn't a 5x increase in time; it's only a 2x increase in time. And fillup time consumes the tiniest fraction of your total trip time. If you combine fillups with your normal breaks (food, bathroom, rest, etc), which you're supposed to take every two hours or so anyway, there's no difference in distance you can travel per day with rapid charging versus gasoline.
Yes, energy density is a downside of titanate chemistries. They're really poor in this regard. Although it should be noted that there's some confusing in the above calculations the energy density of the chemistry itself and that of packaging / battery management (which is part of why large format cells tend to have better energy density).
Commercially available traditional li-ion cells now exceed 220Wh/kg. The individual cells used in the Roadster pack are 160Wh/kg, although there's pack overhead on top of the individual cell overhead.
Pumped hydro costs $500-$1500/kW and $50-$150/kWh. Let's look at a system that needs to be able to provide 1MW for 12 hours (soaking for the rest). It needs to store 12MWh, so the total cost is $2.2M. Let's give it a nominal lifespan of 40 years and an amortized maintenance/labor cost of 500k. So $2.7m over 40 years over which time 12000*365.24*40=175,315,200 kWh of electricity will be released to consumers. That's 1.5 cents per kilowatt hour. Now, that's an oversimplification, since there's a time value to money, and you have to take interest into account (although you also have to take into account the inflation rate for the electricity you're selling). But you get the picture.
Bulk lead-acid? That's generally about $75/kWh, right in the middle of the hydro range. Power output generally isn't an issue. But as you noted, PbA goes bad over time, and you have to replace them. While this is a "down the road" cost, reversing the "time value of money" equation, it generally means that pumped hydro is cheaper.
Vanadium redox is similar to PbA in that there's both a per-kWh and a per-kW cost. I don't have solid numbers for it, but it is generally reported as being similar to or cheaper than PbA in high storage, low power applications, but more expensive in high power, low storage applications. It has excellent lifespan characteristics.
The political efficiency of losing 90% of your generated power (probably 150% if you count the construction cost amortized over 20 years) in a way that is called "green" by journalists who don't realize that there is anything behind the power socket...
What on Earth are you talking about? Pumped hydro storage has a 70-85% round trip efficiency. Energy payback for wind and hydro is a couple years. HVDC has only a couple percent losses over long distances So what are you talking about?
Really, what's up with this article in general? What, to say "wind turbines have to be feathered during storms"? That's why they make them so that they can be feathered. That's the whole point. Are they trying to point out the "little known fact" (note the sarcasm quotes) that the amount the wind blows in a given area varies? Why not point out *actual* little known facts, such as that HVDC can haul huge amounts of power on proportionally small amounts of conductors over huge distances with losses of about 3% per 1000 miles? Or that by spreading wind out geographically, a sizeable chunk of it can be counted on to be as reliable as our current standards for baseload reliability? Or perhaps they could bust that bird-kill myth that just won't die? Or perhaps that stupid "wind turbines just mean more spinning standby, so they don't actually produce any power" myth?
Nah, it's an article all about, "OMG! You have to feather blades in a storm, and the wind doesn't blow all the time in a given place!
Local energy storage with hydrogen, 98% efficiency? HA!
Round trip, it's closer to 50% using ceramic fuel cells, and the capital costs are absurd compared to other options relative to power provided (and only moderate relative to energy stored).
The two most cost-effective storage methods at this point in time are batteries and pumped hydro. In most areas, pumped hydro is cheaper. Pumped hydro does *not* require continuous incoming water (beyond what is lost to evaporation), and the water pumped need not be freshwater (it could be a mining pond contaminated with nuclear waste for all they care). As far as batteries go, there are several techs that are all reasonable and depend on what you need -- lead acid and various flow batteries (most famously, vanadium redox) being the prime examples.
Also, not all energy storage is for *supply* buffering. Worldwide, the overwhelming majority of it is for *demand* buffering. And not all of the demand buffering is even due to power plant limitations; some is due to line limitations. For example, one of the Rattlesnake lines out in Utah has a vanadium redox buffer for voltage support out in Castle Valley. The area is sensitive, so they have trouble building new lines, and a lot of the places that need power are rather isolated, so they can't justify increasing the capacity of their existing lines. So what they did was build a big buffer in the middle of it that stores power at night and releases it during the day.
Energy storage does add a cost, but it's not prohibitive. It's generally a couple cents per kilowatt hour, give or take.
Again, if you compare high speed performance, the prius is lot slower. Top speed of 320d ED is 228kmh, and that is much more than prius. So it is bit faster off the line, and lot faster at highway speeds.
But off the line is what most people care about. You experience 0-60 often -- for many people, multiple times a day. But even on the Autobahn, the average speed is 83mph. In most people's real-world driving, they never even hit their top speed. Since 0-60 is the number that matters, that's the number I reference.
So if you are, I don't know, going to the vacation with full car, and floors it on highway, doesn't it drains the batteries ? If I remember right, the capacity of priuses battery pack was around 4-5kWh. It is not much when you are requiring full power.
No, it doesn't drain the batteries. Actually, the Prius pack capacity is a lot less than that -- 1.3kWh, of which only 0.3kWh is available. Remember that issue with low depth of discharge being required on small batteries that I mentioned? That's it right there. But it's more than enough to buffer periods of peak demand. The key is that the energy consumption difference between acceleration and cruising is huge. Cruising at low highway speeds in an efficient car may take ~12kW of engine/motor power. Kinetic energy is 1/2 mv^2. So to go from 90 km/h to 120 km/h in a 1250kg vehicle takes 303,819J. Spread out over, say, 4 seconds, takes an additional *80* kilowatts. So the performance needed for strong acceleration is *way* more than that needed for cruising. In a hybrid and plug-in hybrid, the engine needs to be able to provide the power needed for cruising, while the battery needs to be able to have enough buffer for acceleration and the motor enough power to perform the acceleration (although conventional "parallel" hybrids mix the roles of the electric and gas engines). Now, one might say, "what if the buffer runs out"? But in that four-second acceleration that brought you to 120km/h, even if your generator wasn't able to provide *any* extra power to the pack during this time frame (which, obviously, it does -- a lot), you only spent 89Wh (plus pack losses -- overall, a bit over 100 Wh). That's only a third of your pack, for a pretty hefty acceleration. Throw in that your generator is producing significant power during this time period and you can see how it's not a problem.
In conventional hybrids, they rely on that power from the generator more for the peaking loads due to the smaller buffer. In plug-in hybrids, the generator is typically made smaller (although there are reasons for larger generators at times), since it has more time to buffer.
Man, it is not EGR.
" Prius also brings many new firsts to the Toyota lineup. To help increase fuel efficiency, the 1.8-liter engine is beltless, uses an electric water pump, a new exhaust gas recirculation (EGR) system, and an exhaust heat collection system. "
I don't know if I remember it correctly, but doesn't battery pack for tesla costs around twenty thousand $$$ or even more? That is quite a lot.
The cost of a Roadster battery pack is tricky -- namely, because you can't buy one now except in a Roadster;) Tesla offers a 3 year, 36,000 mile standard warranty (and optional extended warranty) and does all the service themselves, so they have no need to sell them outright yet. Musk stated a year ago that the pack alone would at the time cost $36k -- but that's not in small part due to all of the hand assembly involved. The individual cells by now (160Wh/kg laptop-grade 18650s) are under $300/kWh. Due to their costs significantly going down, both in terms of batteries and production costs, Tesla offers a $12,000 "future battery r
Really, had the N1 development process been fully prioritized and properly funded, it could have been an excellent craft. The lack of testing made it poorly handle failures which, when you have that many engines, is almost inevitable. Each time, a single problem took down the whole craft. But the craft was very innovative -- staged combustion engines arranged in a way that formed a primitive aerospike airbreather, for example. Pre-heated fuel from the regenerative cooling was preburned to run the pumps (more common now, but rare then), and the engines were operated fuel-rich. Air, and later O2, was pumped into the hole at the center of the engine ring to burn in the fuel-rich exhaust. The engine ISP on the upper stage was much lower than that of the Saturn V because they didn't use H2, but because of the innovative design, the payload difference wasn't all that huge (130 tonnes vs. 95)
That is how manufacturers measure their fuel consumption numbers, isn't it ?
Yes. The US uses the FTP75 for city, US06 for highway, and a weighted average of the two for combined. Europe uses the NEDC. Japan uses the laughable 10-15.
There is lots of critics here about it, because it doesn't reflects the reality. The numbers are really low, and most users gets their consumption quite higher. Read something about EPA cycle being much more accurate and real.
The US's numbers *used* to be significantly off. They revised the system several years ago to what it is at present, which actually does a very good job. Individuals vary, but if you look at reported averages instead of anecdotes, with the new numbers, it's pretty reflective of average US driving habits. The NEDC is in part lower energy because of typical European driving habits, but it's also dated; Europeans use a bit more energy than it says they do on average today. The NEDC averages about 15% less energy than US combined. The Japanese 10-15 doesn't accurately describe how *anyone* drives;) It's about 15% less energy than the NEDC. That's why, when hybrids first started coming out, we heard of all of these ridiculous mpg claims for them coming over from Japan (hybrids do exceptionally well on the 10-15).
And yes, I know that it is just a mixture of carbohydrates with very different characteristics.
I assume this is a language issue: hydrocarbons, not carbohydrates.:) Carbohydrates are what you consume when you eat bread, potatoes, pasta, etc.
Citroen C3 1.4HDi diesel versus 1.4i petrol. 2001 models
CO2 g/100km: 110 (diesel), 148 (petrol) (34.5% better for diesel) 0-100km/s: 15.4 (diesel), 14.2 (petrol) (8.5% better for petrol)
Scaling the CO2 to account for engine output differences: 26%
That's a pretty exceptional case; normally there's not that much of a difference (the diesel has a turbo and the gasoline doesn't, by the way). For an exceptional case in the other direction:
0-60s from The Car Connection, mpg from fueleconomy.gov. So in this case, the disel is no better than the gasoline *before* adjusting for fuel density, and is worse after. But in general, diesels *are* more efficient. Just not as efficient as your example.
I was using the numbers of standard 320d, not 320dED. ED is lot less powerful (aprox 20hp) and 10kg lighter
I assumed you'd want to compare their most efficient model (*shrug*). All of my comparison figures were for it.
I'm not sure what do you think. Yes engine is smaller, but car is also lot slower.
Not "a lot" slower (at least compared to the model I was doing comparisons with, which is the only one that my above numbers are thus valid for). The thing is, with electric and hybrids, any extra power you add from the electric side, it costs you nothing in terms of efficiency. It can actually improve efficiency. For example, the Tesla Roadster gained about a dozen miles range when it went from Powertrain 1.0 to Powertrain 1.5, a higher power one. It's a totally different paradigm. The gasoline engine needs to only, at a minimum, be able to provide for "average" consumption in "typical" peak operating conditions.
And I forgot another think. Prius don't have gearbox, just clever differential like planet gearing. And I assume this "gearbox" is much lighter then standard transmission.
Another advantage of hybrid tech, yes.
Yes 0-100 numbers are not that different. But in lower speeds the electric engine helps a lot. Once you a
Or the time when the Soyuz crew asphyxiated before reentry. Things can always go wrong in orbit. But what do these things have to do with controlled versus uncontrolled landings?
Not at all. All but the first couple post-WWII Soviet rockets were *very* different from the V2. The R1 was basically a V2 replica, but the R7 was based on Korolyov's pre-war designs.
We always seem to be looking for ways to downplay the Soviet achievements in space in the 1950s and early 1960s. Why is that? Is it too much to accept that there were some *really damned good Soviet rocket scientists* over there? Had they not been majorly underfunded compared to the US in the moon race, and had they not made a couple of key design blunders with the N1, they likely would have beaten us in that, too. The loss of Korolyov in the middle of the project didn't help, either.
The reality is that it was the *US* that was heavily reliant on German rocket scientists and German technology, to a much greater extent than the Soviets. We shipped over three hundred freaking train loads of V2 parts back to bootstrap our space program. We took almost all of their top scientists (most Germans were scared of the Soviets, and the US offered big incentives).
You're thinking about all wrong. Yes, the nitrogen is basically an ablative, but you missed a key aspect of reentry: radiative heat loss. Surfaces radiate heat proportional to their temperature to the fourth power. The hotter you can run them without them melting, the faster they radiate. The key point of a coolant isn't to keep the surface *cool*, but to keep it *cool enough* that it can radiate in peace without failing. You can't omit the radiative heat loss.
Indeed -- look at the history of capsules -- the sinking of Mercury 4, the Voskhod 2 crew's night surrounded by wolves, Soyuz 18a's high-G roll that nearly sent it tumbling off a 500' cliff, etc.
I think the best example is Soyuz 23: a mistargetted landing led to the capsule landing on a frozen lake and crashing through the ice. No problem as it was designed to float, right? Well, the parachute got wet and, weighed down, dragged the capsule upside down. The vent tube -- open, as per standard practice -- now began to fill the craft with ice-cold water. The cosmonauts luckily stopped it up before it sent the craft to the bottom. So there they waited, half submerged, upside down in a frozen lake, with no air, in -22C weather. They had to cut way their space suits and get into clothes so as not to freeze; it took an hour and a half. They relied on regenerated air, and did everything possible to conserve power -- they'd leave the system off until they nearly blacked out from the CO2, then turned it on just long enough to clear up. Nonetheless, they still ran out of power. Helicopters couldn't land in the blowing mist, and rescue attempts failed until they ultimately got a hook on the parachute and dragged the craft half a dozen kilometers across the frozen landscape before they could be rescued.
Being able to control where you land is a very good thing.;)
That's not entirely true; it's more of a US excuse during the space race. The US was very successful with Operation Paperclip, which was an attempt to make sure that the US, not the USSR, got most of the German rocket scientists (as well as several whole V2 rockets). The Soviets got a few German rocket scientists (most notably, Helmut Gröttrup, Wernher von Braun's assistant), but not many. Most of the people they got were low level people, mainly on the assembly lines. They were primarily interrogated for information and little used beyond that point. After 1951, not even Gröttrup was allowed to assist in their rocket program any more, and he was returned to Germany in 1953 -- back when von Braun was just starting to become a big rocketry name in the US, and well before his tenure as NASA's first director (1960-1970).
So how do you think normal driving for truck looks like ? In europe it is highway driving at constant speed, more or less constant load for hundreds miles.
To avoid each person having a different metric, we use standardized drivecycles. The drivecycle that the EU uses to model how people typically drive for vehicle mpg ratings is called the NEDC -- the New European Drive Cycle. It is a combination of urban and highway driving that approximates typical european driving patterns (which, by the way, are lower energy than typical US driving patterns -- hence the US uses FTP75 (city) and US06 (hwy), which are higher energy, and correspondingly leads to lower MPG figures for the same car in the US). You can see the NEDC here.
If you want to talk about pure highway driving, even that is not constant speed. Speed on the highway varies based on traffic density, random factors (passing, being passed, etc), current weather conditions, stops (gas, rest, etc), start and end accel/decel, exits (to surface streets or other highways), and driver randomness. Beyond speed, energy consumption varies based on weather and especially altitude changes. For an example, here are actual measurements taken from a vehicle in the US. Here's a test drive that starts with city and progresses to intra-urban freeway. Your mileage may vary.
(I have my own drive data recordings, but I am not at liberty to disclose them, so I'm linking to publicly available ones)
Highway driving runs an engine much more efficiently than city driving. You're closer to the peak efficiency (although not at it), you brake less, idling is basically eliminated, etc. Now, there's obviously a big downside -- your aero drag is *way* higher, and your rolling drag slightly higher (yes). In non-hybrid vehicles, the upsides outweigh the downsides (sometimes significantly). In hybrid vehicles, the downsides usually outweigh the upsides.
No this is not from wiki. It is from book called "Automobile fuels" (translated)
Right. Which is why I said, "If you had cited... you would have..." instead of "You cited... you did." Understand? I'm pointing out that different sources give different numbers because there is no single correct number because they're not a single chemical mixture. You've picked one source to latch onto, when there *is no single answer*. Check other sources; you'll see what I mean. Mixtures vary from location to location and even day to day (for example, summer versus winter blends). They even change from year to year, as standards and refineries are always changing. Their energy densities vary, too. But overall, the *current global average* is about 15% denser for diesel than gasoline.
I don't know how many times I need to stress this, but let me do so once more: There Is No Single Fuel Called Gasoline Or A Single Fuel Called Diesel. How about this -- how about I cite a bunch of random sources?
Wrong. Please pay attention to the wording that I highlighted: normal driving. See the highlighting? You're comparing *peak efficiency* to *normal driving*. Check out the graph on the page that you linked. See how much efficiency varies? Beyond that, there's energy thrown away by braking and energy lost to idling. This (very roughly) halves the efficiency in non-hybrids from the peak.
The density of petrol varies around 750kg/m3 diesel around 820kg/m3. So yes, there is a difference, but it is around 10%
If you had cited Wikipedia, you would have said that they're 18% different, giving a figure of 720kg/m^3 for gasoline and 850kg/m^3 for diesel. But the reality is that neither are right. There is no single density for gasoline or diesel because there is no single fuel called "gasoline" or "diesel". There are all different kinds of blends. They average about 15% difference.
And where the hell the 15% efficiency difference came from ? I'm quoting your post, using your numbers.
Experience. To be less vague, when you've taken enough gasoline and diesel vehicles of the same model and same acceleration and compared their CO2 outputs and their density-adjusted fuel consumptions, you'll arrive at the same number (give or take ~5%).
For all of the below, I will use this and this for the BMW's stats. I will use this for the 2010 Prius's stats.
And yes, drag areas differs. Prius is smaller. It has also better aerodynamics (0.26 vs 0.27)
I guess I have to explain this one as well. Drag area *includes* the drag coefficient (Cd) (what you refer to as "better aerodynamics"). Drag area is the cross sectional area times the drag coefficient.
Drag areas are what matter, but they're rarely released (automakers prefer to release only the Cd, if that) -- although some release them, and other sites compute them. The BMW 320d EfficientDynamics actually has an official drag area -- 0.59m^2. The Prius does not. So we'll compare dimensions (ignoring length, as length is often a *good* thing).
If we treat them each as a square, minus the ground clearance, that's 3655 square inches for the Prius and 3,596 square inches for the BMW. So, not taking shape into account, but just dimensions, the BMW actually has a slightly lower cross section. It has a slightly higher drag coefficient. Overall, the drag areas should be approximately equal.
it has low RR eco tires
The Prius comes equipped with Yokohama AVID S33D tires. The BMW uses Michelin EnergySaver tires. Now, rolling drag coefficients are even harder to get than drag areas (and, FYI, are a grossly inaccurate measure anyway). But it's worth mentioning that the EnergySavers are the most efficient tire Michelin makes.
it is front wheel drive so there are (few %) less drive-train losses
True, but the effect is small, as you note.
it is almost 200 kg lighter than bmw (more than 10%)
Prius: 3042 lbs BMW: 3296 lbs
200 pounds, perhaps, but not kg. Also note that part of the weight of the BMW is due to how heavy diesel engines are compared to gasoline, so this is, at least in part, something that should be credited as an advantage of hybrid tech over diesels, rather than a difference in the comparison vehicles themselves. Batteries are famously heavy, but the Prius pack is very small. Note that aero drag is well dominant in highway cycles over rolling.
Man, what the hell ? That is exactly what I'm talking about. About EXISTING cars and plants. About average of what we have NOW.
Yes, you're talking about average consumption. I'm talking about marginal. Because marginal is what's relevant. It's like when people say, "Well, very little corn in the US is irrigated, so when doing calculations on corn ethanol, we should assume un-irrigated corn." Well, yeah, but the land that you'd have to farm to make up for the new corn demand is the marginal, irrigation-requiring lands. The same sort of thing applies to energy consumption. It's the marginal power that matters, not average power. And since these are vehicles that will last for decades, it's the marginal, decades-averaged consumption that matters.
No, super efficient cars will not magically pop-up, but nor your turbines will. Or should I argue with some turbocharged turbo-compound diesel trucks with almost 50% efficiency ? No. Few trucks doesn't matter, and we are talking about average 20-25% for cars.
They're already being built. Diesels which average 50% in normal driving don't even exist in the lab.
btw have you heard about bmw 320d ? 180 horses and 4.7l / 100km in combined cycle? Bit more interesting numbers (form me) than 135 hp 3.9l / 100 km from prius.
You're pushing a common misconception -- that all fuels are equivalent. Yes, diesel engines are more efficient than gasoline engines, but only by about ~15%. The rest of the efficiency gain is that the fuel is denser -- there's more "oil" in that liter. Hence, the BMW 320d EfficientDynamics gets 109g/100km CO2, while the new Prius gets 89g/100km. Furthermore, not all cars are created equal; weight and drag areas being the big differing parameters.
Can you please explain it to me with your peer reviewed literature? Because diesel (25% eff) should be quite less effective than petrol hybrid cars (30-35%).
Another common misconception. 30-35% is *peak* efficiency, not *average*. Gasoline cars idle, they brake, they run in torque/rpm combinations that are far from optimal, etc. They average about 20% in normal driving.
And sorry man, I didn't know that only expert in problematics are allowed to discuss here.
People who know what they're talking about are welcome. People who rely on assumptions and ignorance aren't.
I know a bit about the cars so I tough I can join the discussion
Because I know a bit about genetic engineering, I should start telling genetic engineers what they can and can't do, right?
And no, I'm not going to pay 30$ for some study just to discuss it with you.
Got a university around you? Heck, a lot of the papers on the topic are free. For example, the DOE/PNL's work.
We have numbers about car efficiency from 2007, so we have to talk about power plant (average) efficiency in 2007. Today, one super effective gas turbine doesn't matter. Thousands of old plants does.
So you're just going to A) magic all of these cars into existence in an instant, and B) run them *solely* on our existing generation infrastructure? How do you propose we do either of those? And, FYI, even if you build a car today -- the average car on the road is nearly 10 years old, implying an average lifespan of nearly 20 years. You think the grid is going to look the same decades from now as today?
The simple fact is that oil is getting dirtier as the cleaner, easier to get to supplies are exhausted (increasing reliance on bitumen, deepwater, liquefaction, etc), while electricity is getting cleaner (increasing reliance on high-efficiency NG, combined cycle, wind, etc). But even from where we are today, electrics are much cleaner and more efficient, according to peer-reviewed research. Have you seen the DOE/PNL paper on PHEVs?
And as car manufacturers are under huge pressure to limit CO2 emissions (fuel consumption), the efficiency of cars may go up even faster than efficiency of plants.
Automakers have had the incentive to increase engine efficiency for a long time. For ICEs, CAFE basically imposes a limitation on the combination of efficiency times horsepower. Greater efficiency means you can make more powerful vehicles and still comply. Not to mention that MPG is a selling point in and of itself (although it's highly dependent on the current gas prices).
The way power plants are getting more efficient are two ways, neither of which can apply to automobiles. The first is super-high temperature combustion, which increases your maximum carnot efficiency. This works in the large scale, but not the small scale. The second is the addition of additional thermodynamic cycles, such as a boiling water cycle to capture more waste heat. This, too, is not applicable to things on the scale of cars.
Now, that's not to say that ICEs are, or will remain static. For example, HCCI could increase gasoline efficiency up to diesel efficiency if they can get it to work reliably, durably, and affordably. But it's just not of the same scale that power plants can improve, or even close to it.
Lots of new cars use some form of brake energy recovery, they are automatically turn off engine when you stop, they have low rolling resistant tires, improved aerodynamics, more efficient transmission, special cooling and waste heat management and more.
You mean things that EVs have automatically?
In 5 years, all new cars will have this technologies. But it is included in the study you mentioned ? I'm not sure.
Perhaps you should read it before you debate it?
The answer is, yes, hybrids are discussed. And they're not as good as EVs even with current average grid generation efficiencies.
To be honest, I know nothing about tank-to-something studies.
Then why, exactly, are you in a debate on the subject? Don't you think you should *learn* about something before you *debate* it?
But as you have to produce petrol or diesel in refinery, you also have to "produce" gas and coal (I suppose it have to be cleaned, refined, transformed, milled)
Yes, you do. The energy to do it, however, is a fraction as much as for oil. And the energy to produce oil keeps increasing as we switch to less optional sources. This is all discussed in the peer-reviewed literature.
Slashdot Mirror
Furthermore:
Yes, about 3% of active, publishing climatologists disagree (Doran, 2009; EOS, Transactions, American Geophysical Union)
Which Earth was used to conduct these experiments that provided the evidence?
The same Earth that was used to "conduct these experiments" which showed us that dinosaurs used to roam the Earth, that huge asteroids have hit our planet in the past, and that our planet is 4 1/2 billion years old. All fake too, I suppose?
You don't have to personally experience something to have compelling data that it exists. I didn't witness my own conception, but I'm pretty darned sure it actually happened and that I wasn't carried here by a stork or grew out of a head of cabbage. Why? Because all of the available data suggests that's how humans are born.
To go back to this case: there are many causes of climate change (all spelled out in the IPCC AR4, if you care to read it). The studies on each of them are presented, each with their own level of forcings and the confidence interval for each study. There are a wide variety of studies for each type of forcing -- for example, one paper might involve a physics model, while another might involve measurements using a satellite, another might involve a measurement using ground stations, another measurement using balloons with different instruments, and so forth. So you have multiple completely independent lines of evidence for the strength of each forcing. A consensus level of forcing and confidence interval is reached from each forcing. The consensus level shows that GHGs dominate the climate change forcings.
The other leading climate change forcings, such as land use changes, are clearly anthropogenic. But what about GHGs? There are several different approaches that study this. One is "old carbon versus new carbon"; carbon from coal, oil, etc has a different isotopic signature than carbon from decay and the like. Mind you, it's the same signature as with volcanism, but volcanism emissions are readily studied and are utterly dwarfed by manmade emissions. We catalog manmade emissions from different sources (with confidence intervals, of course), and that also shows that the overwhelming amount of carbon contributing to the relentless and steady rise is also anthropogenic and matches the rise very well in terms of magnitude over time. We look at changes in natural carbon sources and sinks and likewise quantify them. Furthermore, we not only look at totals, but where they're coming from; our latest satellites how have the resolution to see new carbon being added to the atmosphere and where it's coming from, and watch the anthropogenic plumes diffuse into the broader atmosphere. When you look at the numbers, there's no doubt where this new carbon is coming from; it's overwhelmingly anthropogenic, with nothing else even close.
Beyond all of this, we use a wide variety of physics models -- both global models and models for specific components. A model can be something as simple as a calculation of radiative heat transfer under different gas mixtures, or as complicated as something that models the sources and sinks over the entire planet and covers all of the various feedback mechanisms. Models are nearly all based on first principles in large part or entirity. Depending on the type of model, they're either validated with lab data or historic climate data.
All in all, the conclusion is the result of literally many thousands of peer-reviewed papers covering a wide variety of disciplines.
You do realize that the rate of warming at the end of the last glaciation is about two orders of magnitude than the rate of warming we're experiencing today, right?
Yes, the current rate has been experienced before -- the Paleocene-Eocene Thermal Maximum was the last analogous period. But that was 56mya. And anyway, I don't think we want to repeat it. It changed the world so much that we give the subsequent era a new name (the Eocene).
Replaced after a few years, huh? Then why are both Nissan and GM offering 8 year, 100,000 mile warranties on their non-titanate battery packs? And you don't *have* to replace them when the warranty runs out; that just means that's when they'll cover it for free.
People did the same sort of fearmongering about the Prius's battery. All unfounded.
I think the reason people always focus on battery lifespans is that they assume that all batteries behave the same way. But it's just not true. The reason that the batteries don't last long on your laptop or cell phone is that they're not engineered to last long. It's not expected that you'll have the device that long, and they know that consumers are more concerned with things like minimizing the size and weight of the battery pack. As a consequence, they use high energy density, low cycle life/longevity chemistries. They have no cooling systems (and often are put right next to heat sources). They use very high depths of discharge. They do little to no charge rebalancing between cells. And so forth.
1) Their numbers were inflated approximately 3-fold even when you account for their math error. Unless you're talking an electric Yukon or something.
2) Why would you rapid charge *at home*? The point of rapid charging is to allow for long trips.
3) That's what battery buffers are for.
To go with $150/kWh and 10,000 cycles out of a Vanadium-Redox battery buffer: that's ~67 kWh delivered per dollar of batteries, meaning a battery buffer capital cost of 1.5 cents per kWh of electricity you sell. Eminently affordable.
1. The Tesla Roadster has to go nearly 85mph to consume 30kW to maintain speed. At 50mph, it takes about 12kW. The Roadster is approximately equally efficient as the Leaf and Volt; it has a small cross section but a much higher drag coefficient.
2. A general number used to represent highway consumption for a typical efficient EV is 250Wh/mi. 200 miles range * 250Wh/mi = 50kWh. 90% of 50kWh in 5 minutes is 540kW. Aerovironment makes an 800kW charger. Now to be fair, most rapid charging systems don't exceed the lower hundreds of kilowatts, and some of the lower end ones (like Nissan is installing for the Leaf) are in the tens of kilowatts. The rough cutoff point for what is considered "rapid" charging and what is not is around 40kW.
3. Notice how dramatically different of numbers you got, despite your using 120kWh instead of 50kWh? You had a three orders of magnitude math error.
4. To go ahead and pre-empt it: No, you don't want to have everyone drawing hundreds of kilowatts straight from the grid. That would be a big grid destabilization and require massive hookups. The typical approach for such high power charging involves battery buffers, sized to ensure that you can statistically guarantee a given percent availability (99.99% or whatnot). And to pre-empt *that*: No, they're not prohibitively expensive. Neither are the chargers, although you do need (very roughly) the sort of utilization rates found at gas stations to justify their cost (a station of rapid chargers sharing a common buffer costs about the same as a gas station with a similar number of pumps). The chargers have the advantage of less maintenance, no need to take "fuel deliveries", and a dramatically cheaper "fuel". They have the disadvantage of lower throughput and the possibility of lower consumer price acceptance (since they're used to charging for so cheaply at home). You can also only support fewer stations from the same number of vehicles, since most charging is done slowly at home or at work.
5. To preempt something really stupid that gets mentioned every time: no, you don't rapid charge at home. Why would you need to be able to charge in 5 minutes at home? Can do you that with your gas car? Rapid charging is only needed for long trips.
6. Yes, 10 or 15 minute charges (a more realistic target for rapid charging of EVs, and ones that some EVs like the BYD F3DM and the Subaru Stella support) are slower than filling up a gasoline car. But not as much as you might think. The actual filling of the tank only takes about two minutes or so (depends on the pump, but there are legal limits to the maximum flow rate). But there's a lot of overhead to *every* type of fillup -- finding an offramp, slowing down, driving from the turnoff to the station, turning in, pulling up to a pump, turning the car off, unbuckling, getting out your money, getting out, taking off the gas cap, connecting the vehicle, selecting the fuel type, selecting the payment method, starting filling, stopping filling, reattaching the gas cap, hanging up the pump, paying, taking the receipt, getting back in, putting your seatbelt back on, and all of the driving/decel steps in reverse, plus a lot of little random things. I timed it for a while and found that the whole process sets me back an average of about 9 minutes. So going from a 2 minute fill to a 10 minute fill isn't a 5x increase in time; it's only a 2x increase in time. And fillup time consumes the tiniest fraction of your total trip time. If you combine fillups with your normal breaks (food, bathroom, rest, etc), which you're supposed to take every two hours or so anyway, there's no difference in distance you can travel per day with rapid charging versus gasoline.
6,000 cycles, not 600 (1.2 million miles).
Yes, energy density is a downside of titanate chemistries. They're really poor in this regard. Although it should be noted that there's some confusing in the above calculations the energy density of the chemistry itself and that of packaging / battery management (which is part of why large format cells tend to have better energy density).
Commercially available traditional li-ion cells now exceed 220Wh/kg. The individual cells used in the Roadster pack are 160Wh/kg, although there's pack overhead on top of the individual cell overhead.
Pumped hydro costs $500-$1500/kW and $50-$150/kWh. Let's look at a system that needs to be able to provide 1MW for 12 hours (soaking for the rest). It needs to store 12MWh, so the total cost is $2.2M. Let's give it a nominal lifespan of 40 years and an amortized maintenance/labor cost of 500k. So $2.7m over 40 years over which time 12000*365.24*40=175,315,200 kWh of electricity will be released to consumers. That's 1.5 cents per kilowatt hour. Now, that's an oversimplification, since there's a time value to money, and you have to take interest into account (although you also have to take into account the inflation rate for the electricity you're selling). But you get the picture.
Bulk lead-acid? That's generally about $75/kWh, right in the middle of the hydro range. Power output generally isn't an issue. But as you noted, PbA goes bad over time, and you have to replace them. While this is a "down the road" cost, reversing the "time value of money" equation, it generally means that pumped hydro is cheaper.
Vanadium redox is similar to PbA in that there's both a per-kWh and a per-kW cost. I don't have solid numbers for it, but it is generally reported as being similar to or cheaper than PbA in high storage, low power applications, but more expensive in high power, low storage applications. It has excellent lifespan characteristics.
What on Earth are you talking about? Pumped hydro storage has a 70-85% round trip efficiency. Energy payback for wind and hydro is a couple years. HVDC has only a couple percent losses over long distances So what are you talking about?
Really, what's up with this article in general? What, to say "wind turbines have to be feathered during storms"? That's why they make them so that they can be feathered. That's the whole point. Are they trying to point out the "little known fact" (note the sarcasm quotes) that the amount the wind blows in a given area varies? Why not point out *actual* little known facts, such as that HVDC can haul huge amounts of power on proportionally small amounts of conductors over huge distances with losses of about 3% per 1000 miles? Or that by spreading wind out geographically, a sizeable chunk of it can be counted on to be as reliable as our current standards for baseload reliability? Or perhaps they could bust that bird-kill myth that just won't die? Or perhaps that stupid "wind turbines just mean more spinning standby, so they don't actually produce any power" myth?
Nah, it's an article all about, "OMG! You have to feather blades in a storm, and the wind doesn't blow all the time in a given place!
Local energy storage with hydrogen, 98% efficiency? HA!
Round trip, it's closer to 50% using ceramic fuel cells, and the capital costs are absurd compared to other options relative to power provided (and only moderate relative to energy stored).
The two most cost-effective storage methods at this point in time are batteries and pumped hydro. In most areas, pumped hydro is cheaper. Pumped hydro does *not* require continuous incoming water (beyond what is lost to evaporation), and the water pumped need not be freshwater (it could be a mining pond contaminated with nuclear waste for all they care). As far as batteries go, there are several techs that are all reasonable and depend on what you need -- lead acid and various flow batteries (most famously, vanadium redox) being the prime examples.
Also, not all energy storage is for *supply* buffering. Worldwide, the overwhelming majority of it is for *demand* buffering. And not all of the demand buffering is even due to power plant limitations; some is due to line limitations. For example, one of the Rattlesnake lines out in Utah has a vanadium redox buffer for voltage support out in Castle Valley. The area is sensitive, so they have trouble building new lines, and a lot of the places that need power are rather isolated, so they can't justify increasing the capacity of their existing lines. So what they did was build a big buffer in the middle of it that stores power at night and releases it during the day.
Energy storage does add a cost, but it's not prohibitive. It's generally a couple cents per kilowatt hour, give or take.
My god, I have to read before I post something.
We all make silly mistakes at times. :)
But off the line is what most people care about. You experience 0-60 often -- for many people, multiple times a day. But even on the Autobahn, the average speed is 83mph. In most people's real-world driving, they never even hit their top speed. Since 0-60 is the number that matters, that's the number I reference.
So if you are, I don't know, going to the vacation with full car, and floors it on highway, doesn't it drains the batteries ? If I remember right, the capacity of priuses battery pack was around 4-5kWh. It is not much when you are requiring full power.
No, it doesn't drain the batteries. Actually, the Prius pack capacity is a lot less than that -- 1.3kWh, of which only 0.3kWh is available. Remember that issue with low depth of discharge being required on small batteries that I mentioned? That's it right there. But it's more than enough to buffer periods of peak demand. The key is that the energy consumption difference between acceleration and cruising is huge. Cruising at low highway speeds in an efficient car may take ~12kW of engine/motor power. Kinetic energy is 1/2 mv^2. So to go from 90 km/h to 120 km/h in a 1250kg vehicle takes 303,819J. Spread out over, say, 4 seconds, takes an additional *80* kilowatts. So the performance needed for strong acceleration is *way* more than that needed for cruising. In a hybrid and plug-in hybrid, the engine needs to be able to provide the power needed for cruising, while the battery needs to be able to have enough buffer for acceleration and the motor enough power to perform the acceleration (although conventional "parallel" hybrids mix the roles of the electric and gas engines). Now, one might say, "what if the buffer runs out"? But in that four-second acceleration that brought you to 120km/h, even if your generator wasn't able to provide *any* extra power to the pack during this time frame (which, obviously, it does -- a lot), you only spent 89Wh (plus pack losses -- overall, a bit over 100 Wh). That's only a third of your pack, for a pretty hefty acceleration. Throw in that your generator is producing significant power during this time period and you can see how it's not a problem.
In conventional hybrids, they rely on that power from the generator more for the peaking loads due to the smaller buffer. In plug-in hybrids, the generator is typically made smaller (although there are reasons for larger generators at times), since it has more time to buffer.
Man, it is not EGR.
"
Prius also brings many new firsts to the Toyota lineup. To help increase fuel efficiency, the 1.8-liter engine is beltless, uses an electric water pump, a new exhaust gas recirculation (EGR) system, and an exhaust heat collection system. "
I don't know if I remember it correctly, but doesn't battery pack for tesla costs around twenty thousand $$$ or even more? That is quite a lot.
The cost of a Roadster battery pack is tricky -- namely, because you can't buy one now except in a Roadster ;) Tesla offers a 3 year, 36,000 mile standard warranty (and optional extended warranty) and does all the service themselves, so they have no need to sell them outright yet. Musk stated a year ago that the pack alone would at the time cost $36k -- but that's not in small part due to all of the hand assembly involved. The individual cells by now (160Wh/kg laptop-grade 18650s) are under $300/kWh. Due to their costs significantly going down, both in terms of batteries and production costs, Tesla offers a $12,000 "future battery r
Really, had the N1 development process been fully prioritized and properly funded, it could have been an excellent craft. The lack of testing made it poorly handle failures which, when you have that many engines, is almost inevitable. Each time, a single problem took down the whole craft. But the craft was very innovative -- staged combustion engines arranged in a way that formed a primitive aerospike airbreather, for example. Pre-heated fuel from the regenerative cooling was preburned to run the pumps (more common now, but rare then), and the engines were operated fuel-rich. Air, and later O2, was pumped into the hole at the center of the engine ring to burn in the fuel-rich exhaust. The engine ISP on the upper stage was much lower than that of the Saturn V because they didn't use H2, but because of the innovative design, the payload difference wasn't all that huge (130 tonnes vs. 95)
Yes. The US uses the FTP75 for city, US06 for highway, and a weighted average of the two for combined. Europe uses the NEDC. Japan uses the laughable 10-15.
The US's numbers *used* to be significantly off. They revised the system several years ago to what it is at present, which actually does a very good job. Individuals vary, but if you look at reported averages instead of anecdotes, with the new numbers, it's pretty reflective of average US driving habits. The NEDC is in part lower energy because of typical European driving habits, but it's also dated; Europeans use a bit more energy than it says they do on average today. The NEDC averages about 15% less energy than US combined. The Japanese 10-15 doesn't accurately describe how *anyone* drives ;) It's about 15% less energy than the NEDC. That's why, when hybrids first started coming out, we heard of all of these ridiculous mpg claims for them coming over from Japan (hybrids do exceptionally well on the 10-15).
I assume this is a language issue: hydrocarbons, not carbohydrates. :) Carbohydrates are what you consume when you eat bread, potatoes, pasta, etc.
Citroen C3 1.4HDi diesel versus 1.4i petrol. 2001 models
Diesel ref, petrol ref.
CO2 g/100km: 110 (diesel), 148 (petrol) (34.5% better for diesel)
0-100km/s: 15.4 (diesel), 14.2 (petrol) (8.5% better for petrol)
Scaling the CO2 to account for engine output differences: 26%
That's a pretty exceptional case; normally there's not that much of a difference (the diesel has a turbo and the gasoline doesn't, by the way). For an exceptional case in the other direction:
2011 BMW X5 xDrive35d: 6.4 (0-60), 19 mpg (cty), 26 (hwy), 22 (cmb)
2011 BMW X5 xDrive35i: 0-60: 6.9 (0-60), 17 (cty), 25 (hwy), 20 (cmb)
0-60s from The Car Connection, mpg from fueleconomy.gov. So in this case, the disel is no better than the gasoline *before* adjusting for fuel density, and is worse after. But in general, diesels *are* more efficient. Just not as efficient as your example.
I was using the numbers of standard 320d, not 320dED. ED is lot less powerful (aprox 20hp) and 10kg lighter
I assumed you'd want to compare their most efficient model (*shrug*). All of my comparison figures were for it.
I'm not sure what do you think. Yes engine is smaller, but car is also lot slower.
Not "a lot" slower (at least compared to the model I was doing comparisons with, which is the only one that my above numbers are thus valid for). The thing is, with electric and hybrids, any extra power you add from the electric side, it costs you nothing in terms of efficiency. It can actually improve efficiency. For example, the Tesla Roadster gained about a dozen miles range when it went from Powertrain 1.0 to Powertrain 1.5, a higher power one. It's a totally different paradigm. The gasoline engine needs to only, at a minimum, be able to provide for "average" consumption in "typical" peak operating conditions.
And I forgot another think. Prius don't have gearbox, just clever differential like planet gearing. And I assume this "gearbox" is much lighter then standard transmission.
Another advantage of hybrid tech, yes.
Yes 0-100 numbers are not that different. But in lower speeds the electric engine helps a lot. Once you a
Or the time when the Soyuz crew asphyxiated before reentry. Things can always go wrong in orbit. But what do these things have to do with controlled versus uncontrolled landings?
Not at all. All but the first couple post-WWII Soviet rockets were *very* different from the V2. The R1 was basically a V2 replica, but the R7 was based on Korolyov's pre-war designs.
We always seem to be looking for ways to downplay the Soviet achievements in space in the 1950s and early 1960s. Why is that? Is it too much to accept that there were some *really damned good Soviet rocket scientists* over there? Had they not been majorly underfunded compared to the US in the moon race, and had they not made a couple of key design blunders with the N1, they likely would have beaten us in that, too. The loss of Korolyov in the middle of the project didn't help, either.
The reality is that it was the *US* that was heavily reliant on German rocket scientists and German technology, to a much greater extent than the Soviets. We shipped over three hundred freaking train loads of V2 parts back to bootstrap our space program. We took almost all of their top scientists (most Germans were scared of the Soviets, and the US offered big incentives).
You're thinking about all wrong. Yes, the nitrogen is basically an ablative, but you missed a key aspect of reentry: radiative heat loss. Surfaces radiate heat proportional to their temperature to the fourth power. The hotter you can run them without them melting, the faster they radiate. The key point of a coolant isn't to keep the surface *cool*, but to keep it *cool enough* that it can radiate in peace without failing. You can't omit the radiative heat loss.
I've thought of active cooling myself.
I think pretty much everyone who's lived in Houston in July has as well. ;)
I always wondered, if you used an active cooling system, where would you radiate the heat?
You vent the heated gas. Aka, it's a gasseous ablative.
To space or to orbit?
For "a couple thousand bucks", you're going to have to wait for non-rocket methods of launch.
Indeed -- look at the history of capsules -- the sinking of Mercury 4, the Voskhod 2 crew's night surrounded by wolves, Soyuz 18a's high-G roll that nearly sent it tumbling off a 500' cliff, etc.
I think the best example is Soyuz 23: a mistargetted landing led to the capsule landing on a frozen lake and crashing through the ice. No problem as it was designed to float, right? Well, the parachute got wet and, weighed down, dragged the capsule upside down. The vent tube -- open, as per standard practice -- now began to fill the craft with ice-cold water. The cosmonauts luckily stopped it up before it sent the craft to the bottom. So there they waited, half submerged, upside down in a frozen lake, with no air, in -22C weather. They had to cut way their space suits and get into clothes so as not to freeze; it took an hour and a half. They relied on regenerated air, and did everything possible to conserve power -- they'd leave the system off until they nearly blacked out from the CO2, then turned it on just long enough to clear up. Nonetheless, they still ran out of power. Helicopters couldn't land in the blowing mist, and rescue attempts failed until they ultimately got a hook on the parachute and dragged the craft half a dozen kilometers across the frozen landscape before they could be rescued.
Being able to control where you land is a very good thing. ;)
That's not entirely true; it's more of a US excuse during the space race. The US was very successful with Operation Paperclip, which was an attempt to make sure that the US, not the USSR, got most of the German rocket scientists (as well as several whole V2 rockets). The Soviets got a few German rocket scientists (most notably, Helmut Gröttrup, Wernher von Braun's assistant), but not many. Most of the people they got were low level people, mainly on the assembly lines. They were primarily interrogated for information and little used beyond that point. After 1951, not even Gröttrup was allowed to assist in their rocket program any more, and he was returned to Germany in 1953 -- back when von Braun was just starting to become a big rocketry name in the US, and well before his tenure as NASA's first director (1960-1970).
So how do you think normal driving for truck looks like ? In europe it is highway driving at constant speed, more or less constant load for hundreds miles.
To avoid each person having a different metric, we use standardized drivecycles. The drivecycle that the EU uses to model how people typically drive for vehicle mpg ratings is called the NEDC -- the New European Drive Cycle. It is a combination of urban and highway driving that approximates typical european driving patterns (which, by the way, are lower energy than typical US driving patterns -- hence the US uses FTP75 (city) and US06 (hwy), which are higher energy, and correspondingly leads to lower MPG figures for the same car in the US). You can see the NEDC here.
If you want to talk about pure highway driving, even that is not constant speed. Speed on the highway varies based on traffic density, random factors (passing, being passed, etc), current weather conditions, stops (gas, rest, etc), start and end accel/decel, exits (to surface streets or other highways), and driver randomness. Beyond speed, energy consumption varies based on weather and especially altitude changes. For an example, here are actual measurements taken from a vehicle in the US. Here's a test drive that starts with city and progresses to intra-urban freeway. Your mileage may vary.
(I have my own drive data recordings, but I am not at liberty to disclose them, so I'm linking to publicly available ones)
Highway driving runs an engine much more efficiently than city driving. You're closer to the peak efficiency (although not at it), you brake less, idling is basically eliminated, etc. Now, there's obviously a big downside -- your aero drag is *way* higher, and your rolling drag slightly higher (yes). In non-hybrid vehicles, the upsides outweigh the downsides (sometimes significantly). In hybrid vehicles, the downsides usually outweigh the upsides.
No this is not from wiki. It is from book called "Automobile fuels" (translated)
Right. Which is why I said, "If you had cited ... you would have..." instead of "You cited... you did." Understand? I'm pointing out that different sources give different numbers because there is no single correct number because they're not a single chemical mixture. You've picked one source to latch onto, when there *is no single answer*. Check other sources; you'll see what I mean. Mixtures vary from location to location and even day to day (for example, summer versus winter blends). They even change from year to year, as standards and refineries are always changing. Their energy densities vary, too. But overall, the *current global average* is about 15% denser for diesel than gasoline.
I don't know how many times I need to stress this, but let me do so once more: There Is No Single Fuel Called Gasoline Or A Single Fuel Called Diesel. How about this -- how about I cite a bunch of random sources?
Simetric: 820-950kg/m^3
Alan Harvey, National Institutes of Standards and Technology: 850kg/m^3 typical, but 825-890.
Engineering Toolbox: 810-960kg/m^3
MSDS: 810-880kg/m^3
Gasoline:
MSDS: 710-770 kg/m^3
Simetric: 737kg/m^3
Engineering Toolbox: 680-740kg/m^3
My bad, it is only 44.8%
http://tinyurl.com/39mgjwt
Wrong. Please pay attention to the wording that I highlighted: normal driving. See the highlighting? You're comparing *peak efficiency* to *normal driving*. Check out the graph on the page that you linked. See how much efficiency varies? Beyond that, there's energy thrown away by braking and energy lost to idling. This (very roughly) halves the efficiency in non-hybrids from the peak.
The density of petrol varies around 750kg/m3 diesel around 820kg/m3.
So yes, there is a difference, but it is around 10%
If you had cited Wikipedia, you would have said that they're 18% different, giving a figure of 720kg/m^3 for gasoline and 850kg/m^3 for diesel. But the reality is that neither are right. There is no single density for gasoline or diesel because there is no single fuel called "gasoline" or "diesel". There are all different kinds of blends. They average about 15% difference.
And where the hell the 15% efficiency difference came from ?
I'm quoting your post, using your numbers.
Experience. To be less vague, when you've taken enough gasoline and diesel vehicles of the same model and same acceleration and compared their CO2 outputs and their density-adjusted fuel consumptions, you'll arrive at the same number (give or take ~5%).
For all of the below, I will use this and this for the BMW's stats. I will use this for the 2010 Prius's stats.
And yes, drag areas differs. Prius is smaller. It has also better aerodynamics (0.26 vs 0.27)
I guess I have to explain this one as well. Drag area *includes* the drag coefficient (Cd) (what you refer to as "better aerodynamics"). Drag area is the cross sectional area times the drag coefficient.
Drag areas are what matter, but they're rarely released (automakers prefer to release only the Cd, if that) -- although some release them, and other sites compute them. The BMW 320d EfficientDynamics actually has an official drag area -- 0.59m^2. The Prius does not. So we'll compare dimensions (ignoring length, as length is often a *good* thing).
Width: 68.7"(Prius), 71.5" (BMW)
Height: 58.7" (Prius), 55.4" (BMW)
Ground clearance: 5.5" (Prius), 5.1" (BMW)
If we treat them each as a square, minus the ground clearance, that's 3655 square inches for the Prius and 3,596 square inches for the BMW. So, not taking shape into account, but just dimensions, the BMW actually has a slightly lower cross section. It has a slightly higher drag coefficient. Overall, the drag areas should be approximately equal.
it has low RR eco tires
The Prius comes equipped with Yokohama AVID S33D tires. The BMW uses Michelin EnergySaver tires. Now, rolling drag coefficients are even harder to get than drag areas (and, FYI, are a grossly inaccurate measure anyway). But it's worth mentioning that the EnergySavers are the most efficient tire Michelin makes.
it is front wheel drive so there are (few %) less drive-train losses
True, but the effect is small, as you note.
it is almost 200 kg lighter than bmw (more than 10%)
Prius: 3042 lbs
BMW: 3296 lbs
200 pounds, perhaps, but not kg. Also note that part of the weight of the BMW is due to how heavy diesel engines are compared to gasoline, so this is, at least in part, something that should be credited as an advantage of hybrid tech over diesels, rather than a difference in the comparison vehicles themselves. Batteries are famously heavy, but the Prius pack is very small. Note that aero drag is well dominant in highway cycles over rolling.
it has brake energy
Man, what the hell ?
That is exactly what I'm talking about. About EXISTING cars and plants. About average of what we have NOW.
Yes, you're talking about average consumption. I'm talking about marginal. Because marginal is what's relevant. It's like when people say, "Well, very little corn in the US is irrigated, so when doing calculations on corn ethanol, we should assume un-irrigated corn." Well, yeah, but the land that you'd have to farm to make up for the new corn demand is the marginal, irrigation-requiring lands. The same sort of thing applies to energy consumption. It's the marginal power that matters, not average power. And since these are vehicles that will last for decades, it's the marginal, decades-averaged consumption that matters.
No, super efficient cars will not magically pop-up, but nor your turbines will. Or should I argue with some turbocharged turbo-compound diesel trucks with almost 50% efficiency ? No. Few trucks doesn't matter, and we are talking about average 20-25% for cars.
They're already being built. Diesels which average 50% in normal driving don't even exist in the lab.
btw have you heard about bmw 320d ? 180 horses and 4.7l / 100km in combined cycle? Bit more interesting numbers (form me) than 135 hp 3.9l / 100 km from prius.
You're pushing a common misconception -- that all fuels are equivalent. Yes, diesel engines are more efficient than gasoline engines, but only by about ~15%. The rest of the efficiency gain is that the fuel is denser -- there's more "oil" in that liter. Hence, the BMW 320d EfficientDynamics gets 109g/100km CO2, while the new Prius gets 89g/100km. Furthermore, not all cars are created equal; weight and drag areas being the big differing parameters.
Can you please explain it to me with your peer reviewed literature? Because diesel (25% eff) should be quite less effective than petrol hybrid cars (30-35%).
Another common misconception. 30-35% is *peak* efficiency, not *average*. Gasoline cars idle, they brake, they run in torque/rpm combinations that are far from optimal, etc. They average about 20% in normal driving.
And sorry man, I didn't know that only expert in problematics are allowed to discuss here.
People who know what they're talking about are welcome. People who rely on assumptions and ignorance aren't.
I know a bit about the cars so I tough I can join the discussion
Because I know a bit about genetic engineering, I should start telling genetic engineers what they can and can't do, right?
And no, I'm not going to pay 30$ for some study just to discuss it with you.
Got a university around you? Heck, a lot of the papers on the topic are free. For example, the DOE/PNL's work.
The GPP was taking your reservoir to be the storage body of water
"The" storage body of water? Pumped hydro requires two bodies of water.
We have numbers about car efficiency from 2007, so we have to talk about power plant (average) efficiency in 2007. Today, one super effective gas turbine doesn't matter. Thousands of old plants does.
So you're just going to A) magic all of these cars into existence in an instant, and B) run them *solely* on our existing generation infrastructure? How do you propose we do either of those? And, FYI, even if you build a car today -- the average car on the road is nearly 10 years old, implying an average lifespan of nearly 20 years. You think the grid is going to look the same decades from now as today?
The simple fact is that oil is getting dirtier as the cleaner, easier to get to supplies are exhausted (increasing reliance on bitumen, deepwater, liquefaction, etc), while electricity is getting cleaner (increasing reliance on high-efficiency NG, combined cycle, wind, etc). But even from where we are today, electrics are much cleaner and more efficient, according to peer-reviewed research. Have you seen the DOE/PNL paper on PHEVs?
And as car manufacturers are under huge pressure to limit CO2 emissions (fuel consumption), the efficiency of cars may go up even faster than efficiency of plants.
Automakers have had the incentive to increase engine efficiency for a long time. For ICEs, CAFE basically imposes a limitation on the combination of efficiency times horsepower. Greater efficiency means you can make more powerful vehicles and still comply. Not to mention that MPG is a selling point in and of itself (although it's highly dependent on the current gas prices).
The way power plants are getting more efficient are two ways, neither of which can apply to automobiles. The first is super-high temperature combustion, which increases your maximum carnot efficiency. This works in the large scale, but not the small scale. The second is the addition of additional thermodynamic cycles, such as a boiling water cycle to capture more waste heat. This, too, is not applicable to things on the scale of cars.
Now, that's not to say that ICEs are, or will remain static. For example, HCCI could increase gasoline efficiency up to diesel efficiency if they can get it to work reliably, durably, and affordably. But it's just not of the same scale that power plants can improve, or even close to it.
Lots of new cars use some form of brake energy recovery, they are automatically turn off engine when you stop, they have low rolling resistant tires, improved aerodynamics, more efficient transmission, special cooling and waste heat management and more.
You mean things that EVs have automatically?
In 5 years, all new cars will have this technologies. But it is included in the study you mentioned ? I'm not sure.
Perhaps you should read it before you debate it?
The answer is, yes, hybrids are discussed. And they're not as good as EVs even with current average grid generation efficiencies.
To be honest, I know nothing about tank-to-something studies.
Then why, exactly, are you in a debate on the subject? Don't you think you should *learn* about something before you *debate* it?
But as you have to produce petrol or diesel in refinery, you also have to "produce" gas and coal (I suppose it have to be cleaned, refined, transformed, milled)
Yes, you do. The energy to do it, however, is a fraction as much as for oil. And the energy to produce oil keeps increasing as we switch to less optional sources. This is all discussed in the peer-reviewed literature.