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this post was submitted on 01 Mar 2024
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So, I understand what Toyota is saying. I'm not sure I agree, but I get it.
Simply put, until we figure out a good solution to the battery problem, EVs are kind of at a dead end. They are about as good as they could be with current technology. There's a big push right now towards better energy storage tech, aka battery tech, for EVs and beyond (everything from cellular/mobile/device applications, to EVs, to "grid scale" storage).
The problem is basically twofold: first, limited energy storage. This is compounded by fairly slow charging... Second, current lithium tech used in EVs tends to be rather.... Flammable. Specifically, the most common chemistries are pyrophoric; aka, they burst into flames on contact with air. .... I'll emphasize that pyrophoric battery chemistries are commonly used in just about all consumer goods. This includes every Tesla, and every cellphone.
The only reason that your phone doesn't spontaneously combust in your hand is because the batteries are sealed so no air can get at the chemistry. The issue with Tesla's EVs is when one cell's seal fails, and it combusts, then the chances that adjacent cells will have their air seal compromised, dramatically increases. This can quickly lead to a chain reaction of failures.
Current research is ongoing into batteries. The golden battery for EVs will have, fast charging, high discharge capability (also known as the "C rate"), similar or better energy density to current cells, and longer charge/discharge cycle life. Since we're already comfortable giving pyrophoric batteries to the general public to carry around in their pockets, I don't think anyone is focused on eliminating that, but, if they can, while achieving the other goals, so much the better.
Other battery chemistries exist that are not pyrophoric, but they lack the energy density of their pyrophoric counterparts. One notable chemistry is LiFePO4, which, by sacrificing some energy density, you get much longer cycle life, and no pyrophoric materials.
Solid state batteries are being researched which should extend cycle life significantly if it can be achieved as a "commercially viable product" (which is corporate talk for something that can be mass produced). Thus far, while sold state batteries exist, they're either done in very small batches, and are very hard to produce, or, they simply don't have the same, or similar, energy density to the lithium/cobalt cells that currently dominate the market.
One alternative is hydrogen. Hydrogen fuel cell technology isn't perfect, with a loss of about 20-30% IIRC, from the energy in vs the energy out. The benefit to hydrogen is that it can be stored, highly compressed (a large volume of gas in a relatively small container), and it doesn't degrade or go bad, so it can be stored indefinitely, aka no significant loss over time. But hydrogen is a far more dangerous material than lithium/cobalt, and a tank rupture from a full tank of hydrogen in an EV, could create an explosion of significant size. It's far more dangerous than the pyrophoric batteries. For more information, see: Hindenburg.
Other alternatives exist, but generally are not being used in EVs for various reasons. Among these are RITEGs. An RITEG outputs a consistent and stable power flow indefinitely, even a relatively small unit could be used to power a vehicle, with a small buffer battery, for upwards of 40 years without needing to "refuel" so to speak. Possibly longer depending on the fuel used. The reason they're not considered is right in the name. The full name for an RITEG is "radio isotope thermal electric generator". Aka, nuclear. The unique thing about an RITEG is that the power output is dependent on the differential between the heating provided by the fuel, versus the temperature of the surrounding material (usually some sort of passive heatsink). They're very safe unless the seal is broken, in which case, you need Hazmat to clean up the mess. Their energy conversion is very very low. The power is stable, but only a small amount of wattage can be generated. It's constant, but it's a small amount. So the presence of a "buffer" battery for acceleration (and most driving) would be required, and often you can get more power from a small solar array, dependent on the weather. I like the idea of RITEGs, but more as a home generator type option, where you could bury one into the ground and dissipate the heat geothermally. No options exist for this and research into thermal electric tech has been stalled for many years. Nevertheless, I think it's awesome. The idea of having a mostly solid-state, base load generator in your back yard, seems like a really good idea, but nobody has done it, since IMO, the regulations would be a nightmare.
Anyways, the battery problem outlined here is what we're all waiting for... A commercially viable product that is on par with the current battery front runner, lithium/cobalt, for energy density, while having a much higher cycle life and a high "C rate".
Hydrogen is NOT a viable option for consumer vehicles. Energy storage is not dense, it is barely more efficient than an ICE, and it is also very flammable because it is highly pressurized H and a large battery. They may be fine for commercial vehicles but there is not a market for them for consumers. That is why Shell is closing up its stations in CA and why Toyota is discounting the Mirai significantly while also giving lots of fuel up money and it is still not enough to do much for demand.
As for solid state batteries, they are already in some BYD vehicles and Toyota itself is claiming that their solid state battery that will offer 650 miles of range should be in cars by 2027.
As for current batteries, the limited storage is not a real issue in 99.5% of cases. Over 99% of trips are under 100 miles. There are quite a few EVs now that can get 300 miles which is more than enough for 99.9% of trips. The comparatively slow charge for fast charge stations is also not much of an issue since few people can drive that long without taking a half hour break (although several models can add 200 miles of range in 15 minutes). The current major hurdle for that charging is working stations that charge at a decent speed. And what about the 99.9% of times when you do not need fast charge? We need to make level 1 chargers significantly more available. The average American only goes a little over 30 miles per day and sits idle for 22-23 hours. If it can be charging for a large chunk of that time, even at level 1 speeds, you are looking at 70-90 miles added per day. We need to offer huge tax incentives to apartment owners to install them in parking spaces and incentives to either install smart panels or upgrade panels to 200A. Cities should also start putting slow chargers in their downtowns where people park.
The overall issues with EVs are largely not the batteries themselves, but the infrastructure surrounding them.
I would agree the charging is a large issue. Apartments especially.
One problem you didn't mention is generation and the grid. The ability to transmit enough power down the grid if everyone were to go to EVs overnight, simply isn't there. The high voltage transmission lines are simply not up to the task right now; and that ignores if we can even currently generate that much power.
I don't recall mentioning range at all, but I would agree, range isn't much of a factor, fast charging is mainly a side benefit of high C rates, the main focus for C rate is the ability to get the power out of the pack when it is needed, so it can be used for the locomotion of the vehicle. Simply put, the amps needed to lug around several tons of metal, batteries and people, is significant, that's not even factoring in any hauling or towing. The ability to deliver that current directly from the battery on a consistent level is the key here. Current lithium/cobalt cells are more than capable of both charging and discharging quickly, though you can usually extend the life of the battery by primarily using lower C rates of charging, usually 0.5C provides the most benefit, lower doesn't increase longevity by enough to be worthwhile, and you get less and less benefit as you approach, then exceed 1C. Solid state batteries shouldn't have nearly the same trouble with this, as long as it's capable of 2 or 3C, it should be plenty for the application.
I disagree on the fuel cell comment regarding efficiency. ICE engines, last I checked, could only convert 20-25% of the energy in gasoline to motion, whereas fuel cells are capable of up to 60% conversion of the energy in the hydrogen to electricity, adjusting for losses in the motors and everything, you should be able to get around 50% energy conversion to locomotion. Fuel cells are getting to a point where they are running up against the physics of the issue and can't really make it any more efficient, ICE motors have been at that point for a while. There are small gains but a large percentage of the energy is converted into light+heat which is considered to be a waste product. There's also the matter of how to create the hydrogen, which, right now, there are not many good methods. The "most green" method is by water electrolysis, separating the oxygen from the hydrogen in water (H2O), which is a very inefficient process, more energy goes in than the resulting hydrogen has. If this is factored in then yes, you're correct that hydrogen fuel cells are not significantly more efficient, since the electricity to hydrogen to electricity conversion is the most lossy part of the whole system. There may be areas where we can enhance hydrogen production and get the numbers more on par with battery EVs, but I digress. As far as I know that is not a focus of current research.
Battery EVs are upwards of 90% efficient or better in most cases, even factoring in all the losses from getting the power into the pack and out of the pack. BEVs are simply more efficient overall. There's no disputing that. ICE vehicles are usually dead last no matter how you look at it.
For charging, foregoing the grid issues, which need to be addressed regardless, every EV owning citizen should have access to a charger at their residence, or at least the option for one. Homeowners can easily buy and install (or have installed) a charger for their own personal use, condos and apartments are the main targets since the parking areas are usually managed by the property owner or condo authority, so installing a charger is a bit more of a problem. That definitely needs to be addressed.
The grid issues are not really that significant. You are correct that we would not be able to do it if things changed immediately. We would need another 800-1000 GW of power generation (an extra 15-20%). But it is not going to happen overnight. Cars last a pretty damn long time. Even if we hit 100% of new cars being B/PH EV in 2035, only about 13% of cars on the road will be EV at that point. It would take another couple of decades for those to be phased out. So this is more problem over the span of three to four decades to increase our grid capacity by 15-20% which is absolutely doable. It can actually result in a more stable grid if vehicle to grid becomes anything close to the norm.
I brought up range and charging speeds because that is what most people worry about. That is almost certainly due to their current mindset from using ICE vehicles where they go to a station to charge. But yes, that was more generalized info and not geared towards your points.
ICE vehicles are about 25-30% energy efficient. FCEV vehicles are a little under 40% while BEVs are about 80% efficient. . So FCEVs are slightly more energy efficient than ICE but a far cry from a BEV.
I did forget one other issue with BEVs that needs to be fixed: they are insanely heavy. That can take quite a toll on roads. This can be solved a couple of ways. The easiest way would be by not buying fucking massive SUVs and trucks that are not needed for the vast majority of trips. A commuter car used to be a thing. Speaking of commute, that brings us to number two. A commuter car does not need 300 miles of range. Small cars with 100-150 mile range are absolutely fine for 99% of trips. The last way would be to use solid state batteries since they can be much lighter for the same range.
But switching to EV will not get us even close to where we need to be for emissions because whole they may produce 80% fewer emissions over the vehicle's lifespan, consumer vehicles only make up less than a third of emissions. Public transportation and biking infrastructure could be massively improved and help a hell of a lot more. Then we need to work on trucking, flight, and energy production.
You're forgetting that we also need to work on global shipping. It's a massive contributor to global emissions.
This is bluntly the place where I think we need fuel cells. Yes, they're less efficient, but they can produce a significant amount of power for a significant amount of time given how much space is usually allocated on shipping vessels for the engine and fuel reserves.
I'm not talking about your mom and dad's little motor boat, I'm talking about freight liners. They run basically 24/7 while on the water and consume more fuel daily than your average coal rolling F350 owner would in a year.
Since it would be done in a more controlled commercial context, safeguards can be put in place that other vehicles wouldn't be able to have. Regular inspections of the safety equipment and testing of the storage and energy systems would be almost trivial to implement.
Honestly, I understand why this isn't in the news, but why isn't anyone else talking about this?
Global shipping is probably not talked about much because it is extremely tough to push any standards. It took forever to get an agreement to stop using the horribly toxic sludge they used to use in international waters. You are right though. It is 100% something that needs to be focused on and fuel cells would help a fuckton in that area. Sure they are not as energy efficient as BEVs but they are a ton better than the garbage fuel cargo ships currently use.
You don't recall correctly: The efficiency of Hydrogen, from solar cell to the wheels is 26%. Electrolysis is highly inefficient and compression and chilling of hydrogen is very energy intensive. Meanwhile, EVs are at 70%.
You are right that batteries kinda suck due to their energy density. However with EVs you can buy today you can still commute every day without noticing any major difference to an ICE car. You can also do long road trips, even in a small car, albeit slower. (Source: did both)
I see I get to have this conversation several times.
I looked it up, hydrogen fuel cells can attain about 60% efficiency from the energy potential in hydrogen, when converting to electricity. So I'm not wrong, we're talking about different numbers.
You're referring to the efficiency of the whole system from generation (via solar panels) to conversion to hydrogen (I assume by electrolysis?) to conversion back to electricity by fuel cell (~50-60% efficiency), then any losses getting the electricity to the wheels. That's a very different number than what I was saying.
AFAIK, no real progress has gone into electrolysis for decades. But we can usually also do natural gas reclamation, which is the process of removing the carbon from CH4, and producing pure hydrogen, which, I believe is a much more energy efficient process.
It becomes an entire discussion to figure out how you're producing hydrogen for the system, which is not an easy topic to tackle in a limited written medium like this one. I decided to forego that and focus on the efficiency of the hydrogen fuel cell vs the energy potential in hydrogen directly. I was still off, I'll give you that, but not so far off to make ICE look like a good option compared to FCVs.
BEVs are great short trip vehicles, daily commuters and all around daily driver vehicles. Even with current battery technology, I'm not disputing that. The fact is that the batteries will cause the cars life to end long before anything else wears out that could potentially cause the car to get scrapped. It's cycle life which is the primary issue, but if we get super long cycle life at the cost of energy density, we generally won't switch (see LiFePO4). If the c rate is too low (significantly lower than current tech), then acceleration and charging time will suffer, and we will equally reject the technology as viable for the purpose. So it needs to beat out lithium/cobalt on cycle life, but come close to, or do the same or better than lithium/cobalt in terms of C rate and energy density.
If anyone finds something that is identical to lithium/cobalt for energy density, and C rate, and just has an improved cycle life while all other factors are the same.... Then IMO the entire industry would pivot so fast your head will spin.
Cycle life is the core of the battery problem. Other factors are nice, but the cycle life is where we need to improve before we can really get rolling on EVs. If that problem can be solved, I don't think that ICE cars will even be built anymore. It will end the consumer petrol market within a decade of such a breakthrough. Of course, there's more uses for gasoline and diesel than vehicles so there will still be gas stations, but there will be a LOT fewer of them, and many will likely be replaced by EV charging points.
If you are looking at the pure engine efficiency, we are now looking at >97% for most EV motors (class IE4). However, the point of the entire transition away from fossil fuels is preventing or delaying climate collapse. For this purpose lowering emissions and reducing energy use go hand in hand, hence the overall efficiency is critical.
Hydrogen is less strongly bound to Carbon than Oxygen, however in this process we produce more CO2 again.
There is a theoretical upper bound for the efficency of water electrolysis, depending on the temperature. While current electrolyzers can surely be improved, since we are already making electricity, we might as well use it directly. Some applications (aircraft, rockets, ...) need the higher energy density of chemical fuels. But: Working with liquid or gaseous hydrogen is terrible: Cyrogenic liquids are not easy to handle, let alone store. Hydrogen will embrittle any metal exposed to it and when inadvertenly mixed with air forms a highly explosive gas. Even the rocket people try to avoid using hydrogen unless they really need the ISP.
So far we have seen EV batteries not degrade a lot due to good BMS. For most cars the battery will last at least 10 years before performance is seriously impacted and even then the battery can be reused for storage (home or grid scale). Most EVs have >40kWh batteries, homes usually need 5-10kWh storage. So one chewed up EV battery could be reused for multiple stationary battery systems.
I do agree that current battery tech is... not great. Having less spicy cells that are easier to recycle or recondition would be a massive gain and more research needs to be a core focus. However Li-Ion and LiFePo are already good enough to work for most people most of the time. Pair this with a lot of wind and solar energy generation and you have mostly sustainable traffic. This can be done right now and it has to be done right now. I argue a lot against hydrogen because it seems like a technology that is not there yet and allows many old players in the energy market to delay a transition which is not beneficial to them.
The argument for hydrogen generally revolves around the fact that it's only waste product is literally H2O. So by using an FCV, you only really emit water as a byproduct, which in general is not of a global cooling chemical than a global warming chemical; though, I don't mean to suggest, in any way, shape, or form that FCVs have any impact at all in reversing global warming.
I would argue that efficiency isn't necessarily the most critical point in regards to "Green" technology. It's an important factor, true, especially when dealing with portable or vehicular energy, since storing a large amount of fuel/energy/power to do a task is generally considered to be a bad idea, mainly due to the size and weight of such storage. I would argue that the efficiency in a less size/weight constrained system, such as a depot or facility, is less of a problem. For example, let's say we're getting 30+ % efficiency solar panels and generating... say, 10kW from the array on average for 5 hours, a total of 50kWh. There's already losses from the solar, but we'll discount that since there's no competing technology to generate power from sunlight which has anywhere near as much efficiency.
From there, we lose maybe 30% from water electrolysis to generate hydrogen. We will lose an additional 40% when that is converted back to electricity for use in FCVs.
The output power will be ~21 kWh.
This is equivalent to a solar array of ~4.5 kW in the same situation, using BEV.
My argument here, against the efficiency matter is: the BEV array is approximately half as large or using panels that are half as efficient, this is going to be located at a facility or location where the hydrogen is stored, which will likely have room for a larger solar array than 10kW. So the only sacrifice made in the scenario is to allocate a larger space and some additional panels to a static location where the hydrolysis is being performed.... Big deal. It's entirely green energy with immense storage capacity (even just as a pressurized gas), and incredible energy density.
Obviously there are still risks with it being literally an explosive, though it can be argued that gasoline also carries that risk and it's literally everywhere. Albeit not as extreme of a risk, but bluntly, gasoline sticks around. Hydrogen generally screws off. Once it's released into atmosphere, yes it's incredibly dangerous and explosive in the presence of oxygen, but it will quickly rise and clear out from ground level where all the spark hazards are... While gasoline releases vapor continually and any ignition of the vaporized gasoline will likely find it's way back to the source of those vapors and ignite them. Hydrogen is a flash and it's gone. It's a trade off of risks either way.
I hear what you're saying, I just don't necessarily agree that it's as bad as it would initially seem.
In the other hand, I've seen the dumb shit people do with anything flammable or explosive and I'd rather not put something so energetic into the hands of the general public. So there's that as well.
I also want to address the matter of urgency. It's not critical that we convert all of the cars to EVs. Personally owned vehicle emissions are not the greenhouse gasses that cause the most significant problem. What most graphs show are intra-country emissions, which either lump all "transportation" emissions into one category, or categorize mostly land-based transport methods. In more global charts they generalize "transportation" as one thing, not defining what each transportation type is contributing. There's a few graphs that are out there, if you dig for them, which show that global transportation is ~75% of emissions, but break it down by purpose/type of transit, and if you really dig into the data, personally owned vehicles are something less than 10% of overall emissions. The rest goes to shipping, like boats, transport planes, trucks etc. large tank liners or cargo vessels are a huge portion of the emissions. There has been zero push to have those converted to electrical options. Whether fuel cell or battery, it's not something that's even discussed. The fact is, those boats are running basically 24/7, consuming more fuel daily than even a mid-sized town of consumer vehicles, and homes combined. And that's just one ship. There are hundreds of them on the water. So having the public convert to EVs, is a literal drop in the bucket of CO2 emissions.
So the question is, why aren't we talking about it? I think the answer is clear. Ships are the bread and butter for oil conglomerates. They need fuel, usually diesel, to get anything anywhere. The global demand for energy to simply move shit around is massive. Nobody wants you looking at it and complaining. Even if the consumer vehicles were all converted to some form of EV overnight, oil companies would still make money hand over fist.
None of this should be taken as "fuck it, let's just keep going with ICE cars". Absofuckinglutely not. Consumers still need to convert to EVs. There is no "but what about" going on here. But having perspective on the issue is essential. We all need to do our part. Right now, everyone seems happy to stay focused on consumer vehicles and the drive towards personal responsibility of carbon emissions, but that's only focusing on consumer emissions. Industrial emissions from shipping and energy production, even just getting the energy products to where they need to go, should also be something that is a part of the discussion because they are far and above more egregious in their carbon footprint than the consumers are. IMO, they've set the pubic against itself to distract from the fact that we're not the biggest problem. There's now a war of sorts happening between "tree hugging" EV advocates and "dinosaur burning" ICE enthusiasts. It's worked and we need to realise that we are all on the same side, and we need to recognize that the real problem isn't us, it's the companies who would rather ruin the planet than ruin their bottom line. Yes, that includes oil companies, but also shipping companies. Other industries are also guilty of massive ecological destruction too.
IMO, this is yet another example of the "elite" driving a narrative that benefits them. That somehow because reasons we should all feel bad about driving our cars to the places we need to go, burning mere gallons of fuel daily for everything we do, while they burn barrels of fuel hourly so they can line their pockets with our money.
Personally, I don't think we should give up on fuel cells or green hydrogen, because there's literal acres of land that can be used for solar to generate the power to produce hydrogen, and use that hydrogen to power fuel cell based electric vessels for transport. They have a virtually inexhaustible supply of water right next to where these docks exist, and plenty of land for solar which can be used for the process. It makes sense; and with a fuel cell vessel the hydrogen can be stored in large pressurized containers that are regularly tested and validated to be safe, with extended safety mechanisms in place that we basically can't do with consumer goods. Weight is also less of a concern, and they already allocate a nontrivial amount of space on the ship to storing fuel for the journey. It would make such a significant impact to overall emissions that the consumer EV thing would be little more than a footnote, rather than the headline news it is right now.
But I don't see anyone even remotely discussing it. Maybe they should.
Toyota is claiming to have a 750-mile solid-state battery that will be commercially available in 2027. https://www.reuters.com/business/autos-transportation/toyota-roll-out-solid-state-battery-evs-couple-years-india-executive-says-2024-01-11/ If this is true, then the battery "problem" will be a moot point.
If it were true, they wouldn't be pushing hydrogen so hard.
Sometimes a company's left hand doesn't know what its right hand is doing. Look at how many times Google has released products that compete with its other products, for example.
The other reason they're pushing hydrogen has to do with Japanese infrastructure, so they could very well be aiming to do both anyway. Domestic hydrogen and international EVs.
Damn really nice post.
We're really at a tough point. Batteries in general suck if we're honest. The biggest problem with EVs is that not only are they worse than ICE in some regards, they are on top of that more expensive.
If they can't compete on longevity they have to compete on price, and right now they are nowhere close to worth the cost.
My personal opinion is that plugin hybrids are the future. Best of both worlds. You use the electric batteries for day to day, but you never have to worry about getting stuck or not starting in the winter.
I'm also a fan of hybrids right now. There's fewer batteries to create problems, and the packs are cheaper than what's used in vehicles that are only EVs, reducing cost and weight.
I don't like that some manufacturers have either stopped offering, or never offered plug in hybrids, and bluntly, I don't understand why. It's literally a charge controller, a plug, and some wiring.... Looking at you Honda.
My biggest issue with hybrids and EVs is that many manufacturers use insane designs for them. It's like, no.... I want a normal fucking car, that just has a battery and some electric drive motors. Not a cross between a 3 year olds drawing of a "car" and a Fischer price toy.
Like, give me something that looks like a corolla or an accord, or literally any normal sedan, with a PHEV system under the hood at a reasonable price and I'll sell my old beater car today and buy one, but no. They have to do stupid crap like whatever the hell this is from BMW:
Or the Prius (which I'm sure we all know what they look like.... Kind of a stubby station wagon looking thing)... There's a freaking ton of examples, and the price is always a lot higher (usually double or more to the ICE counterpart).... So I'm going to pay more for this clown car? Fuck.
I'm actually unreasonably angry that so many hybrids and EVs look so stupid.
I'm in team "BMW i3 looks better than any boring Corolla". I like the unusual EV aesthetics. I want funky cars.
Personally I love that BMW design, but I'm a weirdo with a super tiny garage. They are super cheap used because they have the worst battery range I have seen in any EV and their "extender" solution is basically just slapping a gas generator into the car. It's assumed most EVs will be bought by middle class city people, so they go for more compact designs.
They're super cheap because replacing the batteries cost 16k
Yeah, no kidding. These will never be viable for personal vehicular applications because they are A) by necessity incredibly heavy, large, and expensive with the casings, shielding, heat exchangers, etc. required, and B) can't produce enough energy to meaningfully propel something the size of a car any useful distance in any realistic time frame. A 1500 kilogram unit the size of a refrigerator only generates ~35 watts. That's not enough to do anything with, from a transportation perspective. There is no "new technology" that's going to get around this, either. Isotope half lives are what they are. The decay heat is what it is. The temperature differentials that you can safely maintain in a consumer environment can only be so large. That's physics.
You'd literally be better off with a $200 worth of solar panels from Harbor Freight to recharge your EV. And yes, that includes taking into account that solar panels don't work at night.
That, and you'd never get any random member of the public to willingly park anything that is known to contain radioactive isotopes in their own back yard. Radiophobia would ensure that such a proposal would be completely dead on arrival. People are already deathly frightened enough of radioisotopes existing in tightly regulated, very competently run nuclear power plants.
I'd happily have a RITEG buried in my back yard to sustain my base load from my house. Using geothermal cooling for the unit seems like a good idea, and it would be underground where nobody can fuck with it.
RITEG research and use hasn't stopped, but most of the terrestrial units have been long decommissioned. The most recent example of note was the MMRTG unit used in curiosity (now on Mars), which is 45 KG and can produce 110W of output. The most notable terrestrial examples were the IEU units used by the Soviets for light houses, weighing upwards of 2-3 tones and producing less than 120W at their peak, mostly fueled by strontium 90 (the MMRTG uses plutonium 238). The only modern RTG for terrestrial use is the Sentinel units used for monitoring stations in the arctic by America, which top out under 60W and weigh more than a ton, closer to 2 ton. There are others but information is limited.
A lot of weight is due to the fuel (which is classified as a "heavy metal") and the casing, which on earth is more robust than you would need in space, since it's feasible that people would be nearby the unit for extended periods of time and any breach could be fatal.
Even with the weight, if we're effectively burying it in a yard, deep enough to take advantage of geothermal cooling, then weight isn't really a problem. Even size isn't a problem since it can be the size of a large consumer vehicle and most homeowners have more than enough land to accommodate that... With little more than an access hatch for inspections and maintenance, it would be a viable option to contribute to offsetting the base load of your home. Even a 100W unit would trim about 2.4kWh from a household electricity bill per day for something like 100 years. That's in the ballpark of 8.5 GWh over the lifetime of the unit before the fuel needs to be replaced (based on the half life of the material. Strontium 90 would need to be refueled every 40-50 years or so).
I'm not saying it's a fix to the problem by any stretch, but it could trim about 1/4 of electricity costs per home, based on an average consumption of around 10 kWh per day.
This is why I like RTGs, they're stable and long lasting, relatively safe (unless the housing/shielding fails) and solid state with basically no maintenance.
I'm a fan of the idea, but I'm not going to say it's a one stop fix, nor do I think the regulatory people will green light any implementation of such a system for home use, ever. Nor do I think that even if such a solution were to be given approval, that the general public would ever accept it being installed "in [their] back yard" either literally or figuratively.
You're right that a pair of 200W panels and a small battery system would have a similar effect (at least until the batteries needed replacing... or simply grid tie it), and as long as you can average ~2 kWh/day of generation, you'd be fine... You might need 4-5 panels to get the same daily output, but a system like that is probably still less than $1000, and will probably last ~20 years. So to make it economically viable such a system would need to cost the consumer less than ~$5000 or so before it becomes a better option.
I'm still a fan of the technology, and I find it immensely interesting, but I try to keep my expectations realistic. Due to the excessive weight of a terrestrial RTG, it's not viable for a vehicle, but wouldn't it be cool to have a car that charges itself all the time no matter where you park it or whether it's in the sun or not?
I think that would be cool.
Hear me out. If we make the cars significantly lighter and cut holes in the bottom for the feet, we could save significant amounts of energy by allowing the driver to use his own leg strength to push the vehicle along. That could even be some sort of pulley system with chains that would make it easier to force the tires to move.
Oh I got a better idea. What if we link up the cars during long distance travel and have just one really powerful high efficiency car at the front pull all the other ones behind it and then every so often it reaches destinations where the other cars detach and go their own separate way.
Of course it will have dedicated routes, and probably specific times when the big car is passing by so there will be a schedule but that can be mitigated by running with a high frequency.
Heck we can even come up with a fun name for the last car in any Car Conga that essentially calls it a butt.
Shame there is nothing like that.
Lthe answer is hamster. S thousand hamsters in a thousand hamsters wheels in every car. They'll eat their young so it'll be a self sustaining eco system.