[Oldmanmatt]

Obviously, I don’t know the current figures.
 The power density of the first, 1970 devices was 0.025 milliwatts /cm³ (the first commercially available) that had doubled by the time Lithium took over, and Tritium cells were better again.
The latest research (according to the NS article) is putting at 20x the previous maximum, so, conservatively, a minimum of 9 mW/cm³?
Early days.
I’m tempted to swallow my pride and reach out to Alessandro, see if he’ll talk to me.

I’ve been gradually drifting away from the wall and back into Engineering. I’m consulting on systems design for a project in Dubai and I will be taking on some project management stuff after Xmas. Coarse stuff compared to the CMC time, but I always was the “bigger hammer “ end of things...

[teestub]

I've been on a bit of a journey over the last couple of years. Moving toward a more environmentally conscious way of living.

This sounds great FD, I always loved the community schemes when we were in Hackney and can only assume that there’s more and more of that sort of thing now.

[Oldmanmatt]

Very roughly, how much energy do you get out of one of these nuclear batteries (per unit mass or volume - whichever you prefer)? i.e. are we talking about a useful amount of energy, or about it being like sticking a small solar panel on the roof your your electric car and thinking you've solved the problem of how to charge it for your long daily commute?

Ok, the Thermovoltaic batteries used on the voyager missions, were 420w output, Pu units with an energy density of 0.45w/g.

NASA went on to develop it’s multimission unit, which is higher again, but I’ll take that one as the start for the 20x.
So, at a similar mass, energy density of 9 per gram (so way better than the 1970s little pacemaker batteries), the 420w unit was ~1kg.
Therefore the new units would give ~ 8.4kW/kg?
Sound right? I keep having to stop typing/thinking to deal with customers...

There’s a fair amount of mixing and matching between various tech in this, it’s lacking in coherence and I’m extrapolating between them.
To clarify, there are three different nuclear batteries included. The 1970’s Betavoltaics, the Voyager Thermovoltaics  (using ²³⁸Pu, low shielding, but Gamma emitting) and the “New” type for which the only data available is “20x the Thermovoltaic” type.

[abarro81]

Cool, cheers. Wasn't really worried about getting exact numbers, just a back-of-the-envelope gauge of whether you could get a useful amount of energy out for recharging for day-to-day commuting etc if you put it in a car. Sounds like you could, although obviously cost might be an issue! Plus if you still need to charge on long journeys you still need various other bits of electronics..

[tk421a]

Very roughly, how much energy do you get out of one of these nuclear batteries (per unit mass or volume - whichever you prefer)? i.e. are we talking about a useful amount of energy, or about it being like sticking a small solar panel on the roof your your electric car and thinking you've solved the problem of how to charge it for your long daily commute?

Ok, the Thermovoltaic batteries used on the voyager missions, were 420w output, Pu units with an energy density of 0.45w/g.

NASA went on to develop it’s multimission unit, which is higher again, but I’ll take that one as the start for the 20x.
So, at a similar mass, energy density of 9 per gram (so way better than the 1970s little pacemaker batteries), the 420w unit was ~1kg.
Therefore the new units would give ~ 8.4kW/kg?
Sound right? I keep having to stop typing/thinking to deal with customers...

There’s a fair amount of mixing and matching between various tech in this, it’s lacking in coherence and I’m extrapolating between them.
To clarify, there are three different nuclear batteries included. The 1970’s Betavoltaics, the Voyager Thermovoltaics  (using ²³⁸Pu, low shielding, but Gamma emitting) and the “New” type for which the only data available is “20x the Thermovoltaic” type.

Matt, I think you're conflating a couple of things which are incompatible.

The ~0.45w/g of Pu Radioisotope Thermoelectric Generator (RTG) (https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator#Space suggests 0.54-0.57w/g) is the thermal power of the radioactive decay. AFAIK there's no way to change radioactive decay rate of a specific isotope, that's why we know the half-life of say Pu-238. This is the theoretical maximum power density of a Pu-238 RTG. The only way to improve this is to change isotope. The link above has a good section on the selection of fuel (low shielding required, good power density, good half life). Polonium-210 has a much much higher power density, but a half gram sample of it reaches temperatures of 500C through its own decay.

The 20x better is based on the notional improvement in efficiency of converting the radioactive power into electricity. Currently it goes radiation generates heat and heat is converted to electricity with a thermoelectric generator (https://en.wikipedia.org/wiki/Thermoelectric_generator), efficiencies in 3-7%. It's this process that the article refers to as a 20x increase.
The RTGs used in Galileo were 300W and  have a quoted 7% efficiency, so 20x improvement just wouldn't be possible.
The actual output power density of the RTGs is much lower than 0.45w/g. The 300W(electrical) RTG on Galileo weighed for a 5.2W/kg or 0.0052W/g. Even with perfect efficiency we'd only come back to the 0.57w/g power density of Pu-238.

Big problem with using these widespread (apart from the plutonium part) is that they are always on, we can't unplug them and stop the decay, so we have to dissipate the heat anyways. The 300W generators had a thermal power of 4.4kW.

Note: my only source was Wikipedia

[petejh]

Yeah you’re misunderstanding my point but I didn’t word it well. I realise you can’t ‘make’ or destroy energy. It was more a figure of speech for getting energy from carbon-free processes and using it for both transporting people and energy generation - by turning people travelling into the moving parts of a generator.

I don' really understand your idea about using it "for both transporting people and energy generation" - if we use a wind farm or solar farm, we're generating electrical energy... which we then use for whatever we want (light, running heat pumps, charging our EV etc.) If we then go drive our EV, we can recover some energy using regenerative breaking, but only when we're breaking... and not that much, so it makes sense just to run it back into the battery like Steve said.
When we're doing the bulk of using the energy is when we're not breaking, at which point I don't see how we can "generate" energy for the grid - you'd run your battery harder to inefficiently pump energy back into the grid you just took it out of. Perhaps I still don't quite understand what you're getting at. Is your point just about regen breaking?

Not just about regen braking. I'm just wondering out loud that there seems to be so much kinetic energy at work in a road network with millions of vehicles moving around it and most of it goes to waste.
I understand that it's pointless to work an EV (or any vehicle) harder just to put energy back into a storage grid. But what about the example of a vehicle with a magnet in it travelling down a hill over a coil buried in the road- harnessing the kinetic energy produced by force of gravity, which is independent of the kinetic energy produced by the fossil fuel or EV battery that propels the vehicle on the flat? Rather than waste that energy by braking, you could slow down by returning energy to a grid as you pass over the coils? Are there gains to be had there if you scale that up to millions of journeys? Or would that still take as much or more EV battery/diesel energy as the energy that could be returned?

[tk421a]

Yeah you’re misunderstanding my point but I didn’t word it well. I realise you can’t ‘make’ or destroy energy. It was more a figure of speech for getting energy from carbon-free processes and using it for both transporting people and energy generation - by turning people travelling into the moving parts of a generator.

I don' really understand your idea about using it "for both transporting people and energy generation" - if we use a wind farm or solar farm, we're generating electrical energy... which we then use for whatever we want (light, running heat pumps, charging our EV etc.) If we then go drive our EV, we can recover some energy using regenerative breaking, but only when we're breaking... and not that much, so it makes sense just to run it back into the battery like Steve said.
When we're doing the bulk of using the energy is when we're not breaking, at which point I don't see how we can "generate" energy for the grid - you'd run your battery harder to inefficiently pump energy back into the grid you just took it out of. Perhaps I still don't quite understand what you're getting at. Is your point just about regen breaking?

Not just about regen braking. I'm just wondering out loud that there seems to be so much kinetic energy at work in a road network with millions of vehicles moving around it and most of it goes to waste.
I understand that it's pointless to work an EV (or any vehicle) harder just to put energy back into a storage grid. But what about the example of a vehicle with a magnet in it travelling down a hill over a coil buried in the road- harnessing the kinetic energy produced by force of gravity, which is independent of the kinetic energy produced by the fossil fuel or EV battery that propels the vehicle on the flat? Rather than waste that energy by braking, you could slow down by returning energy to a grid as you pass over the coils? Are there gains to be had there if you scale that up to millions of journeys? Or would that still take as much or more EV battery/diesel energy as the energy that could be returned?

If it were already an EV, then that example would be the same as regenerative braking (just without the slowing down).

[Oldmanmatt]

Very roughly, how much energy do you get out of one of these nuclear batteries (per unit mass or volume - whichever you prefer)? i.e. are we talking about a useful amount of energy, or about it being like sticking a small solar panel on the roof your your electric car and thinking you've solved the problem of how to charge it for your long daily commute?

Ok, the Thermovoltaic batteries used on the voyager missions, were 420w output, Pu units with an energy density of 0.45w/g.

NASA went on to develop it’s multimission unit, which is higher again, but I’ll take that one as the start for the 20x.
So, at a similar mass, energy density of 9 per gram (so way better than the 1970s little pacemaker batteries), the 420w unit was ~1kg.
Therefore the new units would give ~ 8.4kW/kg?
Sound right? I keep having to stop typing/thinking to deal with customers...

There’s a fair amount of mixing and matching between various tech in this, it’s lacking in coherence and I’m extrapolating between them.
To clarify, there are three different nuclear batteries included. The 1970’s Betavoltaics, the Voyager Thermovoltaics  (using ²³⁸Pu, low shielding, but Gamma emitting) and the “New” type for which the only data available is “20x the Thermovoltaic” type.

Matt, I think you're conflating a couple of things which are incompatible.

The ~0.45w/g of Pu Radioisotope Thermoelectric Generator (RTG) (https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator#Space suggests 0.54-0.57w/g) is the thermal power of the radioactive decay. AFAIK there's no way to change radioactive decay rate of a specific isotope, that's why we know the half-life of say Pu-238. This is the theoretical maximum power density of a Pu-238 RTG. The only way to improve this is to change isotope. The link above has a good section on the selection of fuel (low shielding required, good power density, good half life). Polonium-210 has a much much higher power density, but a half gram sample of it reaches temperatures of 500C through its own decay.

The 20x better is based on the notional improvement in efficiency of converting the radioactive power into electricity. Currently it goes radiation generates heat and heat is converted to electricity with a thermoelectric generator (https://en.wikipedia.org/wiki/Thermoelectric_generator), efficiencies in 3-7%. It's this process that the article refers to as a 20x increase.
The RTGs used in Galileo were 300W and  have a quoted 7% efficiency, so 20x improvement just wouldn't be possible.
The actual output power density of the RTGs is much lower than 0.45w/g. The 300W(electrical) RTG on Galileo weighed for a 5.2W/kg or 0.0052W/g. Even with perfect efficiency we'd only come back to the 0.57w/g power density of Pu-238.

Big problem with using these widespread (apart from the plutonium part) is that they are always on, we can't unplug them and stop the decay, so we have to dissipate the heat anyways. The 300W generators had a thermal power of 4.4kW.

Note: my only source was Wikipedia

Yeah, this is the problem with doing things whilst multitasking...

Not had a chance to go back over the figures and facts, whilst trying to pull it together in my head.
You are correct of course about the energy density, which makes my weight calc wrong.
However, the article definitely states (up to) 20x power, not efficiency. So, like for like masses, should yield as I stated. Without knowing the aggregate mass of the voyager batteries (including shielding) I cannot actually postulate the new version’s mass.
But, it’s reasonable to assume the voyager battery was quite light.

Still, that’s the high energy, Gamma gubbins, which I would envision in mass transport/larger vehicles. I’m still postulating something Betavoltaic for trickle charging a more conventional battery, or Graphene capacitor/battery for domestic use. I’m thinking of the “focusing” of the nano tubes, as that seems the critical improvement.
Though, the ²³⁸Pu type would seem feasible at a regional/community level. Should be managable temperatures and it looks like thin layers would be the way to go, giving high dissipation area etc...

Anyway, this is a thinking aloud thing on my part.

[Oldmanmatt]

Yeah you’re misunderstanding my point but I didn’t word it well. I realise you can’t ‘make’ or destroy energy. It was more a figure of speech for getting energy from carbon-free processes and using it for both transporting people and energy generation - by turning people travelling into the moving parts of a generator.

I don' really understand your idea about using it "for both transporting people and energy generation" - if we use a wind farm or solar farm, we're generating electrical energy... which we then use for whatever we want (light, running heat pumps, charging our EV etc.) If we then go drive our EV, we can recover some energy using regenerative breaking, but only when we're breaking... and not that much, so it makes sense just to run it back into the battery like Steve said.
When we're doing the bulk of using the energy is when we're not breaking, at which point I don't see how we can "generate" energy for the grid - you'd run your battery harder to inefficiently pump energy back into the grid you just took it out of. Perhaps I still don't quite understand what you're getting at. Is your point just about regen breaking?

Not just about regen braking. I'm just wondering out loud that there seems to be so much kinetic energy at work in a road network with millions of vehicles moving around it and most of it goes to waste.
I understand that it's pointless to work an EV (or any vehicle) harder just to put energy back into a storage grid. But what about the example of a vehicle with a magnet in it travelling down a hill over a coil buried in the road- harnessing the kinetic energy produced by force of gravity, which is independent of the kinetic energy produced by the fossil fuel or EV battery that propels the vehicle on the flat? Rather than waste that energy by braking, you could slow down by returning energy to a grid as you pass over the coils? Are there gains to be had there if you scale that up to millions of journeys? Or would that still take as much or more EV battery/diesel energy as the energy that could be returned?

If it were already an EV, then that example would be the same as regenerative braking (just without the slowing down).

I dunno, that one has some merit.
Whether over all loss of efficiency and increased fuel consumption negates the whole thing, when hauling the extra weight back up the next hill; is another matter.

[abarro81]

Pete - pretty sure what you're describing is basically regen breaking for EVs. Much better to put it in the car than under the road

[Steve R]

Also wonder why we haven’t got solar-powered ships - large surface area and plenty of capacity for massive heavy batteries?

Was interested enough to do a quick back of envelope calc on this.  Used specs for 'Spirit of Britain' cross channel ferry.

NSFW  :

'The main engines include four MAN 7L48/60CR diesel mechanical engines, each producing 7,600kW' so power required to maintain cruise speed ~ 20,000kW seems reasonable?
crossing time = 90mins
so, energy per crossing = 20,000kW x 1.5h = 30,000kWh

deck surface area = 210m (length) x ~30m (beam) = 6,300m^2

solar panels give ~200W per sq.m in ideal cons

so if whole deck is covered in panels, power produced = 0.2kW x 6,300 = 1260kW

let's be generous and say 1000kW average in daylight hours produced
so for a channel crossing;
30,000kWh / 1000kW = 30 hours of sunbathing in port required per 90min crossing.
ie. 4 days ish?  (more with various inefficiencies not taken into account)   

 

bottom line of above calc, for a 90 min channel crossing a fully solar panelled up Spirit of Britain would have to sunbathe in port for about 4/5 days to generate sufficient energy to just make it across.  Which is actually less time than I thought it would be.  But I guess these ferries cross back and forth more or less continuously..... 
however, build a solar farm nearby (orders of magnitude bigger area than deck size of boat) + wind + tidal maybe (or build a nuclear plant), find a way to store it and zap it into ship's batteries quickly and we may have cracked it.  Or since there's market failure to do any of that, carry on using the reliable, tested and profitable solution of diesel fuel and engines. 
Have read electrification of shipping not immediately viable somewhere I think, not entirely sure why, need to research more.  Not sure what happens re. big battery and motor efficiencies/viability when you get in to realm of tens of thousands of kW?   

[tk421a]

Energy density is the big issue.
Fuel oil is about 50 times more energy dense than a li-ion battery. I did a quick Google it looks like ships are around 2% fuel fraction. So to replace everything with li-ion currently would double the displacement of a ship.
Planes around 50% fuel fraction, hence why passenger electric planes are completely a no go until we work out some new chemistry.

As a rough idea, a garage fuel pump is of the order of 10MW power when filling up a car.
For grid attached energy use switching to renewables and battery storage is possible. For non attached high power usage its much harder.

Theres a good book on the science and numbers of energy generation at
https://www.withouthotair.com/
Cambridge Physics Professor analysing the numbers. It was written a few years back but the science of it is still accurate.

[Oldmanmatt]

Yes, this is why fuel cells were the buzz.
However, the channel ferry example, is a worst case.
Most Merchant vessels, will spend very little time manoeuvring and a majority of time at a steady cruising speed. Most of the power requirements in manoeuvring is external (tugs) and the relative increase in displacement by batteries, in partially mitigated by smaller propulsion units (google a Large 2 stroke diesel, they are immense. I once changed a piston on one, the cylinder bore was almost 2 meters).
These vessels are much better suited to alternative power sources than a short ops ferry. Remember too, wind can provide direct drive, as well as charging reservoirs.

Our fuel use, is also speed related, we could do more with less, as it were, if we slowed down. Airships, pure sailing ships (only powered when manoeuvring) etc etc.
We lack the patience, of course and there’s a “single vessel capacity” issue; we’d have to accept more, smaller, consignments etc.
I started out building the diesel electric propulsion for the the type 23 frigates, which were revolutionary, in as much as the motor rotor was the shaft. By the time I was at CMC, we were building motors that absorbed 50% less power for a given output.
(Actually, it’s (unsurprisingly) more complicated than that. Power absorbstion is highest when accelerating a motor, massively so. Starting currents on some equipments can be eye watering. Sometimes, finding ways to avoid accelerating or changing the motor speed, is key, rather than redesigning the motor. Combine  both and you can really make inroads. Another hint, sometimes, with motors, faster is better...).

[Oldmanmatt]

I have yet to go through these, but saved them for later perusal. So, shared without comment:

https://www.sciencedirect.com/science/article/pii/S0360319917339435

https://energypost.eu/u-s-nuclear-plants-to-produce-carbon-free-hydrogen/

[Johnny Brown]

https://www.theguardian.com/business/2019/oct/15/bank-of-england-boss-warns-global-finance-it-is-funding-climate-crisis

[gme]

https://www.theguardian.com/business/2019/oct/15/bank-of-england-boss-warns-global-finance-it-is-funding-climate-crisis

This relates back to my earlier point where i feel that to get things moving faster re development of alternatives it has to be possible for the big financiers to make money from it. I know this doesnt sit well with the capitalism haters but its fact. Chouinard says similar in his 1st book, something along the lines of wall street wont listen unless its able to profit from it.

[lagerstarfish]

just need to persuade the developed world's pension funds that avoiding climate change is profitable and we'll be fine

[tomtom]

just need to persuade the developed world's pension funds that avoiding climate change is profitable and we'll be fine

I’ve been working on my pension fund divesting in Shell and investing in Sharpe enterprises insect protein balls.

[lagerstarfish]

just need to persuade the developed world's pension funds that avoiding climate change is profitable and we'll be fine

they might also want reduce their liabilities by investing in tobacco, alcohol and developing new vices for the over 60s

[tomtom]

just need to persuade the developed world's pension funds that avoiding climate change is profitable and we'll be fine

they might also want reduce their liabilities by investing in tobacco, alcohol and developing new vices for the over 60s

Like boxes of Anasazi whites.... (is shark 60 yet? )

[petejh]

I enjoyed listening to this podcast which makes the case for optimism. (thanks to Steve R for linking in the podcast thread).

https://www.preposterousuniverse.com/podcast/2019/09/16/64-ramez-naam-on-renewable-energy-and-an-optimistic-future/


On another note, by disrupting commuters trying to use electrified public transport are XR shooting themselves in the foot and making more enemies than friends?

[Nutty]

On another note, by disrupting commuters trying to use electrified public transport are XR shooting themselves in the foot and making more enemies than friends?

Definitely, and probably not making friends within XR - according to the Guardian an internal poll of XR members showed 72% opposed action on London Underground.

[crzylgs]

On another note, by disrupting commuters trying to use electrified public transport are XR shooting themselves in the foot and making more enemies than friends?

Definitely, and probably not making friends within XR - according to the Guardian an internal poll of XR members showed 72% opposed action on London Underground.

Can't they just stick to making fools of themselves with fire engine powered water hoses?

Organising mass disruption of the London Underground sounds like an excellent way to not make friends for your cause... Also rather dangerous from a crowd control point of view? :/

[Oldmanmatt]

Yep.

I confess to a facepalm this am.
Way to set the cause back years and confirm Daily Fail stereotypes, ya muppets!

[Oldmanmatt]

Five minute read (unless you follow the citations and links):

https://thoughtscapism.com/2019/10/16/the-risks-of-failed-risk-assessments-on-natural-vs-unfamiliar-sources-of-energy/