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Battery-electric Road Vehicles and Energy Infrastructure
Frank Koenig:
Maybe it's time to move it down here. Or maybe it's done. Anyway. Electric vehicles (EVs) have their plusses and minuses -- like everything else. Here's a short, and by no means complete, list from my point of view, mostly obvious but maybe a few less so.
Plusses:
Higher efficiency measured from the vehicle energy input point. This is due to the relatively high efficiency of Li storage batteries, switching power electronics and electric motors. Regeneration during braking helps further. Pure EVs with large batteries are better able to take advantage of regen. Essentially zero consumption when stopped.
Excellent driving experience. No reciprocating parts makes for low vibration and noise, especially when stopped or at low speeds. Instantaneous power control (both positive and negative) allows for a high level of driving precision and smoothness. Fast acceleration occurs without drama or excessive wear (except for tires) or even much extra energy consumption. The increase from rapid starts is mostly due to the longer time spent in cruise with the resulting higher aerodynamic loss.
No warm-up required and cold shutdowns do not cause damage. Great for those of us who need to reposition vehicles now and then or make short trips.
No reduction in performance with altitude.
Lower direct operating cost in the current market. (My daily driver costs ~ $.04 / mi for electricity -- about the same per-mile cost as tires).
Lower maintenance and the potential for lower lifetime cost as batteries become cheaper. We're just about there for high-utilization operators whose mission profile fits.
Home or shop/depot charging eliminates trips to the gas station. Charging time is essentially zero for intermittently utilized vehicles that sit by a charger when not in use.
Easy and efficient integration into an electric energy-infrastructure. More below.
Minuses:
Range comes at a high cost in purchase-price and weight.
Charging is slow, which is an issue for cross county travel or other high utilization. Mitigated to some extent with larger batteries and high-power chargers. (A larger battery can absorb charge more rapidly adding more miles per minute of charge.) With current batteries the last 20% of charge is much slower so a driving schedule that allows charging to 80% saves a lot of time. Current EVs can charge from 20% to 80% in roughly 30 minutes given a powerful enough charger. Advances in this area are likely.
Many apartment dwellers, and others without private, electrified parking, must rely on inconvenient (and often expensive) public chargers.
Low ambient temperature reduces battery capacity and winter driving consumes more emery reducing range. Partially mitigated by thermal management of the battery, such as charging up to the moment of departure to warm the battery.
Extended high power operation, such as racing on a track, can exceed the battery's thermal limit. This has been mitigated in race-oriented cars through thermal management.
High weight that does not go down as fuel is burned. This compromises handling while being partially mitigated by placing the battery down low. Not too much of a concern outside of serious motorsports though there are knock-on effects such as tire and road wear.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Toward an Electric Energy Infrastructure
As we face an ever more diverse range of energy sources (some of which may not yet have been discovered or developed) we need an infrastructure that can efficiently combine and distribute their energy. Electricity has some advantages:
It is highly fungible. Thanks to power electronics, it is easy and relatively cheap to convert any format (Voltage, frequency, phase) into another. Varying sources such as solar and wind are easy to accommodate.
Electrical machines usually achieve 80% - 90% efficiency at converting in and out of mechanical energy. This is better than combustion engines or current schemes for electrolyzing water into Hydrogen.
Electricity is relatively cheap and safe to transport (PG&E's current problems not withstanding >:( ). DC transmission lines are efficient for long distances where their lower loss offsets rectifier/inverter losses.
So far there is no intercontinental transmission of electric power, but it is not out of the question. This could be quite useful for large-scale leveling of intermittent sources, such as solar.
The elephant-in-the-room minus is storage, both for utility scale load-leveling, which is especially important for intermittent sources, and for vehicles, including air vehicles, that can't be on a cord. Rail transport and the like (hyperloop) distinctly do not belong to this class. Our great hope, for now, is battery technology, which is advancing nicely. Clearly, wider use of batteries will require extracting raw materials and efficient reuse of those materials is required for this to be at all sustainable. This is where I believe we should be directing our efforts.
I've been an EV queen for quite a while. The stable consists of a 2000 Easy Go golf car (to be converted to Li when the current Pb-acids go TU), a 2015 Tesla S 85 D (6 years and going strong), and a 2020 Sur Ron Light Bee electric dirt bike (2 kWh of pure fun).
--Frank
Brian Jojade:
All great points.
Looking far into the future, the concept of an internal combustion engine is very archaic. It's a great stopgap for now, but the excessive complexity just doesn't make a lot of sense. Some people are just beholden to the idea of the engine and don't want to give that idea up. They like the idea of pressing the gas to rev the engine and make noise. Can't really do that with the electrics.
From a performance standpoint, anyone that has driven a performance electric vehicle will quickly say that it certainly can easily keep up with the gas counterparts. Even the low end electrics are quite responsive machines.
Interestingly enough, electric cars have been made since the early 1800's. Limited battery technology of the time and easy access to oil meant development went into gas engines instead, leaving electric cars all but forgotten. But, in the last 100 years, we've just about maximized efficiency that we can realistically get out of gas engines. Improvements year over year are now very small. Any increase in performance or efficiency comes at a very high increase in cost. So much so that it's not practical to make much more advancement.
The need for batteries in portable devices such as laptops and phones has massively improved upon the storage density and reliability of batteries. This naturally has been expanded now into the electric vehicles we are seeing on the market as well. This technology is still quite young and there is a lot yet to learn. 100 years from now, we will likely have alternative ways to store electricity, or even generate electricity from. Someday, we may be able to pull out an old banana peel and a half full can of beer and drop it into Mr. Fusion and be on our way.
Caleb Dueck:
Many great points, for sure.
Also agree that battery tech is a (the?) key bottleneck. For example, periodic sources of electricity, like solar, are limited by battery tech. It's sunny outside today at my house, the power just blipped off for a half second while the computer UPS kicked in. If the cost/capacity of batteries was significantly better so nearly every home had some sort of in-wall battery solution - then the question could shift to, "Why not buy some solar panels?" or some other way of generating intermittent power.
If all homes were built with whatever size in-wall batteries - even a plug-in exercise bike would make sense to own!
Tim Halligan:
The current fossil-fuelled vehicle paradigm is one that we all know very well: you pull up next to the pump, fill your tank, pay the cashier, then drive off with the capacity for however many kilometres of travel before needing to repeat the process. The whole refuelling procedure takes 5 minutes...10 tops.
Until EV's can deliver that kind of charging paradigm they will be a non-starter in many people's minds.
Hydrogen fuel cell equipped vehicles - whilst still a relatively new product - allow us to continue with the paradigm we are all familiar with, and as such may change a few minds along the way.
Cheers,
Tim
Matthias McCready:
--- Quote from: Caleb Dueck on June 03, 2021, 08:00:15 PM ---Many great points, for sure.
Also agree that battery tech is a (the?) key bottleneck. For example, periodic sources of electricity, like solar, are limited by battery tech. It's sunny outside today at my house, the power just blipped off for a half second while the computer UPS kicked in. If the cost/capacity of batteries was significantly better so nearly every home had some sort of in-wall battery solution - then the question could shift to, "Why not buy some solar panels?" or some other way of generating intermittent power.
If all homes were built with whatever size in-wall batteries - even a plug-in exercise bike would make sense to own!
--- End quote ---
Check out Pumped-storage hydroelectricity :-)
The gist is that a body of water can become a giant battery. When there is excess power (ie solar during the day) water is pumped up into the holding area. When energy is needed it flows out through generators. The whole process is somewhere around 90% efficient I believe.
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