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Sustainable Energy without the Hot Air (Revised, Community Edition)

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Re: Sustainable Energy without the Hot Air (Revised, Community Edition)

#101

Post by acidburnNSA »

sdenton4 wrote: post #55
lucb1e wrote: post #20

Earlier quoted context omitted.

I wonder if this is correct. Setting the nuclear slider to max single-handedly reduces emissions by 30%, decreases energy costs rather than increases, does not require land use change, improves air quality, and also reduces electricity demand by using the waste heat for district heating. Now add: (1.) electrification of freight transport, (2.) tackling the (relatively) quick wins in industry electrification, and (3.)…

See also, peak uranium : https://en.m.wikipedia.org/wiki/Peak_uranium 2017 known supply is enough for 130 years at current usage (supplying about 10% of global energy). Each doubling of production halves the peak timeline. Basically no one expects discovery to outpace usage. So, at best, nuclear is a stop gap and part of a different long term solution. Which could be fine! But the extremely low LCOE and fast build ti…

There's more to it than that. The long-term plan for nuclear fission always has been and remains to use breeder reactors after we have ~1000 GW-scale non-breeder reactors in place. Because they can utilize the majority isotope of uranium (U-238) and Thorium rather than just the small natural amount of fissile U-235, breeders enable us to make 100% of the world's primary energy for about 4 billion years (e.g. roughly until the sun burns out) [1].

[1] https://whatisnuclear.com/blog/2020-10-28-nuclear-energy-is-...

The same point was made in the Hot Air book as well [2]

[2] https://www.withouthotair.com/c24/page_162.shtml

Since this is roughly the remaining lifetime of the Sun, there's a very strong argument to consider nuclear fission breeder reactors just as renewable as the solar-derived energies (wind, solar, hydro, biofuel)

Re: Sustainable Energy without the Hot Air (Revised, Community Edition)

#102

Post by acidburnNSA »

bbojan wrote: post #79
sdenton4 wrote: post #55

Earlier quoted context omitted.

See also, peak uranium : https://en.m.wikipedia.org/wiki/Peak_uranium 2017 known supply is enough for 130 years at current usage (supplying about 10% of global energy). Each doubling of production halves the peak timeline. Basically no one expects discovery to outpace usage. So, at best, nuclear is a stop gap and part of a different long term solution. Which could be fine! But the extremely low LCOE and fast build ti…

Current reactors (light and heavy water reactors) all use solid fuel, which is very inefficient due to use of once-through fuel cycle. Because xenon is the most common fission product, and it's a gas, the reaction must be stopped before all fuel is used, as otherwise the solid fuel pellets would crack. If you assume 3% enriched uranium (U-235) and 97% depleted uranium (U-238) (a typical fuel load), the fuel pellets a…

Switching to solid fuel uranium breeders + fluid fuel thorium breeders gets you to around 4 billion years.

Re: Sustainable Energy without the Hot Air (Revised, Community Edition)

#103

Post by gnramires »

ben_w wrote: post #48
cbmuser wrote: post #19

Earlier quoted context omitted.

Physics won’t change in a thousand years and it’s very unlikely we’ll find anything more powerful and energy-dense beyond nuclear fission and fusion.

On that timescale I expect us to engineer antimatter-based energy storage. Or do something literally incomprehensible — a thousand years ago we didn’t have the language to describe the language to describe relativity.

It doesn't quite work like that. 1000 years ago Europeans (you may say) only traveled routinely within 1 continent. Today, they travel routinely to all 7 continents. You can't say in another 1000 years anyone will travel to 14 continents -- there's only so much Earth to discover :)

We can know Earth in better detail, but it's inherently limited. In the same vein, there's no guarantee we will continue to discover revolutionary engineering strategies, and certainly no guarantee of discovering (or not discovering) new physics. In fact, physics has seen a slower pace of discoveries since mid-20th century. This kind of (not necessarily justifiable) optimism is in fact quite a risk when evaluating some technologies on sustainability.

Re: Sustainable Energy without the Hot Air (Revised, Community Edition)

#104

Post by gnramires »

olau wrote: post #78

There was indeed a lot of hot air in sustainability thoughts in 2008, and probably still is, but Mackay's treatment is sometimes bordering the absurd. For instance, the chapter on wind power starts by comparing a back of the envelope calculation on wind power with energy usage by a fossil car. While there are occasional good points, I would not recommend reading this book unless you actually know something about the…

Mackay's point is that you could get through the confusion relatively quickly, and showing in principle how to evaluate and fight the problem. I don't think it was meant as a final solution -- just to show that it was feasible, and approachable as a problem. Without getting into politics or ideology.

I got a quite good intuitive sense of the scales involved, and at least for me Solar clearly reveals itself as an outstanding source of energy (at say 150W/m2).

Re: Sustainable Energy without the Hot Air (Revised, Community Edition)

#105

Post by KennyBlanken »

mattlondon wrote: post #63
mcot2 wrote: post #36

It sounds like this should have a date attached to it as the numbers are quite outdated for todays world. This did have some good data for back when it was written of course. * An efficient EV will do less than 12kWh/100km these days. * Utility scale solar pv cost declines have been dramatic. It is now the cheapest form of new energy to deploy. * Developments in deep water off-shore wind have led to much larger turbi…

It didn't seem to mention hybrids much either. It mentioned a polo bluemotion as the lowest co2 emitting vehicle at 99g/km, but even my 10+ year old hybrid clunker (Toyota auris) officially gets 82g/km - modern hybrids must be way better by now, and they are super common now rather than just Toyota's selling point. A recent report I read on the BBC suggests that public bus transportation is 90g/km/passenger so my anc…

Is that "official" figure from Toyota, or from an independent testing group? A huge number of manufacturers have been caught or admitted to, cheating on their emissions figures - including CO2 levels. Claimed figures are basically worthless.

Why would you think that a compact hybrid would have only slightly better CO2 performance compared to a city bus per passenger? It doesn't even make sense for the vehicle as a whole. Googling around, I came up with this:

https://www.bbc.com/future/article/20200317-climate-change-c...

...shows that your figure is 90g per km for the bus as a whole, not per km/passenger.

Every chart I've seen on co2 or fuel use per mile per person, busses, bicycles, and rail are king. Ride shares are the absolute worst because of all the wasted miles....followed by private SUV and car use.

If you do a google image search for "co2 emissions per passenger mile" you can see endless charts from different studies.

Re: Sustainable Energy without the Hot Air (Revised, Community Edition)

#106

Post by belorn »

mcot2 wrote: post #36

It sounds like this should have a date attached to it as the numbers are quite outdated for todays world. This did have some good data for back when it was written of course. * An efficient EV will do less than 12kWh/100km these days. * Utility scale solar pv cost declines have been dramatic. It is now the cheapest form of new energy to deploy. * Developments in deep water off-shore wind have led to much larger turbi…

> Large scale batteries are now viable as a storage mechanism for renewables

They are economical viable for solar for 3-4 hours every night, which is where they are being deployed. The article talks primarily about the UK with wind being the primary energy source, and so rather than a solar cycle of 24hrs you have wind fluctuations with lulls. The article calculate this to about 1200 GWh.

The articles I have seen on solar + batteries is a capacity of 80% for 4 hrs. I have not seen clear numbers but I would guess that they do get a fairly high discharge rate each day, thus providing an return of investment when the price is at its highest point each day. For wind you would need to have as much capacity as the worst lulls, and they would only really return profits during the lulls (if we do not count subsidizes). There would be some profits from slews, but most of the cost would be going to capacity that isn't needed for most part of the year.

Re: Sustainable Energy without the Hot Air (Revised, Community Edition)

#107

Post by KennyBlanken »

zbrozek wrote: post #80
bluGill wrote: post #68

Earlier quoted context omitted.

Depends on how many people are on the bus. Many buses have terrible load averages, good buses can do a lot better. IMO most bus operators do a terrible job at serving people and so it is no surprise that people don't ride.

Most of the buses I see around here (Sunnyvale through San Mateo is my typical stomping ground) are either "not in service" or very nearly empty. I haven't taken a bay area bus in fifteen years. I routinely outpace them on a bicycle. I could imagine 8-15 passenger vans with on-demand routing would see much better utilization.

Your typical location might place you on the route bus drivers use to return to a depot or to get to the start of a popular route. Or the time you're out and about might coincide with when a large number of busses are coming into, or going out of, service. For example, if you work offset hours you'd easily see the pre or post rush hour ramp up/down traffic.

Out of service busses also travel faster than in service ones; as you note, you outpace busses on your bike.

Perhaps look up research instead of relying upon personal anecdotal observations by one person in one city, subject to observational biases?

The research is likely to be highly accurate given most public bus operators have very good data about ridership numbers and fuel use per vehicle and route.

Re: Sustainable Energy without the Hot Air (Revised, Community Edition)

#108

Post by pfdietz »

Didn't this book also assume substantial biomass energy grown in the UK? If I recall correctly, it was negative on solar due to land use, but that was mostly due to this biomass (which has extremely low energy capture efficiency, requiring a lot of land.)

Re: Sustainable Energy without the Hot Air (Revised, Community Edition)

#109

Post by bluGill »

zbrozek wrote: post #80
bluGill wrote: post #68

Earlier quoted context omitted.

Depends on how many people are on the bus. Many buses have terrible load averages, good buses can do a lot better. IMO most bus operators do a terrible job at serving people and so it is no surprise that people don't ride.

Most of the buses I see around here (Sunnyvale through San Mateo is my typical stomping ground) are either "not in service" or very nearly empty. I haven't taken a bay area bus in fifteen years. I routinely outpace them on a bicycle. I could imagine 8-15 passenger vans with on-demand routing would see much better utilization.

On demand routing cannot get 10 passengers per hour. The idea sounds good, but it has been tried and found slow and inefficient https://humantransit.org/2019/08/what-is-microtransit-for.ht... make sure you read his previous series that he links.

ReaRead that, and then quit wasting everyone's time advocating a stupid idea that keeps coming bcback. Good transit advocacy should aim to get people to not drive.

Re: Sustainable Energy without the Hot Air (Revised, Community Edition)

#110

Post by bluGill »

Robotbeat wrote: post #86
zbrozek wrote: post #80

Earlier quoted context omitted.

Most of the buses I see around here (Sunnyvale through San Mateo is my typical stomping ground) are either "not in service" or very nearly empty. I haven't taken a bay area bus in fifteen years. I routinely outpace them on a bicycle. I could imagine 8-15 passenger vans with on-demand routing would see much better utilization.

Yup. They should be easier to electrify, too. Mass produced electric passenger vans should be a thing. Considering transit vans are only like $50,000 apiece for 12 seats, they should be pretty dang cheap to acquire, too, compared to the $1 million 30 seat e-buses. Charging infrastructure should be the same as regular electric cars, too, which makes it cheaper and more flexible to deploy.

The biggest cost over the lifetime is still the driver. Passenger vans only place in transit is for wheelchairs.
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