Primary energy vs final energy: why replacing fossil fuels may not be so hard • Hacker News Board

Re: Primary energy vs final energy: why replacing fossil fuels may not be so hard

#51

Post by serpix » Tue, Nov 17, 2020, 8:56 PM UTC

lake-effect wrote: post #47

“Electrical devices can sometimes offer higher than 100% efficiency,” said BNEF analyst Matthias Kimmel. That might seem odd. How can there be more energy as output than input? But that’s exactly what heat pumps and air conditioners do. They use electricity to shift heat from the outside to inside, or vice-versa, and typically provide three units of energy service for one unit of energy input, meaning an efficiency o…

well my 80m2 apartment is fully heated to about 22.5C with an air heat pump drawing about 600W with an outside temperature of 0C. So take from that what you will about efficiency.

Re: Primary energy vs final energy: why replacing fossil fuels may not be so hard

#52

Post by Nasrudith » Tue, Nov 17, 2020, 8:58 PM UTC

aardvarkr wrote: post #31

Is no one pointing out that this isn’t the part that makes replacing fossil fuels hard? This is focusing on a completely irrelevant metric. It’s a great motivator for why we need to shift but it has no impact on how hard it will be to replace oil. There’s 100 practical reason for why it’s hard, namely that clean energy sources are not under our direct control to scale up and down as we need more/less. We can’t tell t…

It is relevant to the improved battery tech problem however and makes the task less huge. Wind is also fairly reliable in that the day night cycle alone creates it since it is created by temperature differentials. Across a broad area it is impossible for there to not be wind short of being messed with by hyperadvanced aliens scenarios like ensuring all areas of the earth are being heated equally.

Re: Primary energy vs final energy: why replacing fossil fuels may not be so hard

#53

Post by alacombe » Tue, Nov 17, 2020, 9:00 PM UTC

notthemessiah wrote: post #36

aardvarkr wrote: post #31

Is no one pointing out that this isn’t the part that makes replacing fossil fuels hard? This is focusing on a completely irrelevant metric. It’s a great motivator for why we need to shift but it has no impact on how hard it will be to replace oil. There’s 100 practical reason for why it’s hard, namely that clean energy sources are not under our direct control to scale up and down as we need more/less. We can’t tell t…

This problem is way overstated, as most fossil fuel and nuclear power can't be easily or efficiently ramped down either. We also have energy storage technologies other than batteries: the most common being pumped-storage hydroelectricity (basically a reversible hydroelectric dam, where we pump water up during excess power usage and use the generators during high demand).

> as most fossil fuel and nuclear power can't be easily or efficiently ramped down either.

Ramping it down is irrelevant, you can always use the extra to process aluminium at cheaper rates, pump water back in reservoir, etc. The ramping up is critical, as you expect the light to turn on when you flick the switch, not 3h later.

Re: Primary energy vs final energy: why replacing fossil fuels may not be so hard

#54

Post by [deleted] » Tue, Nov 17, 2020, 9:00 PM UTC

lake-effect wrote: post #47

“Electrical devices can sometimes offer higher than 100% efficiency,” said BNEF analyst Matthias Kimmel. That might seem odd. How can there be more energy as output than input? But that’s exactly what heat pumps and air conditioners do. They use electricity to shift heat from the outside to inside, or vice-versa, and typically provide three units of energy service for one unit of energy input, meaning an efficiency o…

[deleted]

Re: Primary energy vs final energy: why replacing fossil fuels may not be so hard

#55

Post by epistasis » Tue, Nov 17, 2020, 9:03 PM UTC

phkahler wrote: post #37

robertlagrant wrote: post #27

The article seems incomplete. Sure we may be burning three times more coal than we'd have to if we could perfectly convert it to energy. That has literally never factored into an argument I've seen about renewables - it's always "we currently produce X GigaWatts 24x7, and renewables don't let us do that". Saying we burn coal at 30% efficiency isn't addressing anything useful. And it's one of those articles where many…

Right. When people talk about what percent of our electricity comes from where, its always gigawatts from the power plants, not BTUs of coal.

That's not been my experience. Usually when I hear people arguing the impossibility of renewables, they are taking the BTU numbers, not the kWh numbers of actual energy services.

Re: Primary energy vs final energy: why replacing fossil fuels may not be so hard

#56

Post by alacombe » Tue, Nov 17, 2020, 9:04 PM UTC

jcampbell1 wrote: post #6

dudus wrote: post #2

The article tries to explain the difference between primary, final and useful energy to justify why moving to renewables would be easier than at first glance. But I just don't feel like I got convinced in the end. If anything I'm more confused now than before. In special this part about air conditioners being 300% efficient sounds to me like maybe they don't know what they are talking about. “Electrical devices can s…

What is wrong with the concept of a heat pump? A resistor converts electricity into heat 100% efficiently, and a heat pump is often 3x as efficient at heating a house vs electric baseboards.

> a heat pump is often 3x as efficient at heating a house vs electric baseboards.

Not if you consider the whole "indoor + outdoor" referential, in that case you will always get below 100% efficiency.

Re: Primary energy vs final energy: why replacing fossil fuels may not be so hard

#57

Post by roenxi » Tue, Nov 17, 2020, 9:05 PM UTC

toomuchtodo wrote: post #40

aardvarkr wrote: post #31

Is no one pointing out that this isn’t the part that makes replacing fossil fuels hard? This is focusing on a completely irrelevant metric. It’s a great motivator for why we need to shift but it has no impact on how hard it will be to replace oil. There’s 100 practical reason for why it’s hard, namely that clean energy sources are not under our direct control to scale up and down as we need more/less. We can’t tell t…

South Australia already has days when solar alone is providing most of it's power [1] [2]. It's not that hard. You scale up renewables, and build curtailing (throwing away excess clean energy) into your cost model (until storage gets cheaper, which it will; Tesla is shipping almost 800 MW of utility scale battery storage per quarter). Australia's entirely grid will be clean by 2030 at their current rate of renewables…

South Australia was famous recently [0] for having not only the most expensive electricity in Australia, but competing for the most expensive energy in the world. I would encourage the world to be cautious about copying whatever it is they are doing.

And if the South Australia Big Battery is an example of utility scale storage, store's about 1-2 hours worth of energy from a small plant. It isn't capable or expected to help power on through a night or anything, it smooths the grid when there is instability. Ie, it doesn't mitigate the main problem with renewables (intermittent generation). It mitigates secondary problems with renewables (short term grid instability). Or it mitigates whatever problems the South Australians have with their grid, I don't know. Point is, if they were relying 100% on renewables they'd have developed a culture of early bed times.

[0] https://www.news.com.au/finance/business/south-australia-has...

Re: Primary energy vs final energy: why replacing fossil fuels may not be so hard

#58

Post by eulers_secret » Tue, Nov 17, 2020, 9:07 PM UTC

lake-effect wrote: post #47

“Electrical devices can sometimes offer higher than 100% efficiency,” said BNEF analyst Matthias Kimmel. That might seem odd. How can there be more energy as output than input? But that’s exactly what heat pumps and air conditioners do. They use electricity to shift heat from the outside to inside, or vice-versa, and typically provide three units of energy service for one unit of energy input, meaning an efficiency o…

Moving heat does take energy, true.

A restive electric heater (AKA joule heating) is by definition 100% efficient: All energy consumed by the device is turned into heat (if you're mega-pedantic, you could argue some is lost as light and sound).

A heat pump just moves heat from outside to inside. Sure, it's 42*F out, but that's still heat energy that can be moved. This process is more efficient than converting electricity into heat because you get more heat energy in the room than the electric energy you put into the device.

https://en.wikipedia.org/wiki/Joule_heating#Heating_efficien... explains it even better than I did.

Re: Primary energy vs final energy: why replacing fossil fuels may not be so hard

#59

Post by konjin » Tue, Nov 17, 2020, 9:07 PM UTC

roenxi wrote: post #57

toomuchtodo wrote: post #40

Earlier quoted context omitted.

South Australia already has days when solar alone is providing most of it's power [1] [2]. It's not that hard. You scale up renewables, and build curtailing (throwing away excess clean energy) into your cost model (until storage gets cheaper, which it will; Tesla is shipping almost 800 MW of utility scale battery storage per quarter). Australia's entirely grid will be clean by 2030 at their current rate of renewables…

South Australia was famous recently [0] for having not only the most expensive electricity in Australia, but competing for the most expensive energy in the world. I would encourage the world to be cautious about copying whatever it is they are doing. And if the South Australia Big Battery is an example of utility scale storage, store's about 1-2 hours worth of energy from a small plant. It isn't capable or expected t…

Not to mention that it has destabilized the national Australian grid to the point where a 35C day means that you get rolling blackouts across multiple states.

Currently the only way you can be sure you have power on a hot summer day in Australia is to share a substation with a hospital designated to provide life support to patients.

Re: Primary energy vs final energy: why replacing fossil fuels may not be so hard

#60

Post by epistasis » Tue, Nov 17, 2020, 9:09 PM UTC

kortilla wrote: post #41

ip26 wrote: post #34

Earlier quoted context omitted.

FWIW long distance transmission lines work too. Solar peaks a few hours earlier than demand. So ship that power east two timezones.

And which solar panels power California?

Batteries and hopefully offshore wind. And people will time shift energy consumption when incentivized. If we were able to charge cars at work, for example, that would shift massive amounts of load to peak solar hours, when electricity will be essentially free on the generation side, and transmission/congestion costs will be the major factor.

We are well on our way to making enough batteries to replace our car fleet. If we do that, we will have already built the industrial manufacturing capacity to store several days worth of energy.

I forget the numbers, but a huge proportion of wind and solar installs are planning foe good chunks of battery right now. The contracts I've seen indicate a storage cost of $80-$110/MWh, which is cheaper than new nuclear, and pretty much in coal territory.

The future is one of super abundant renewable energy, with the huge fractions of it thrown away, unless somebody can figure out used for it or ways to transmit/store it.