We know that humanity can live without burning fossil fuels or nuclear fuels. (So what? well it means that we could just give up on fossil fuels over night if we had to. It would destroy all of civilisation, but given a choice between than a total anhiliation, perhaps we would choose that.)
There are plenty of gasses with GWP less than 1. N2 for example. The gas with a GWP of 21000 is probably SF6, a popular gas for high voltage insulation.
CO2 levels have been much much higher in the past, and apparently with similar transition times as currently. Life prevailed. Big animals may not have:)
Ok, you haven't addressed my remark that heating is more important than electricity, but let me give you some things to think about regarding decentralised electricity, for example.
PVs are probably a red herring. They are all made by oil companies, so even were they viable, the oil companies will keep them at a price to maintain the oil demand. I have never advocated PVs in this discussion.
Batteries are also a red herring. If our demand were just lights and electronic devices we could supply everyone in the US using wind and hydro alone. The problem is mainly heating. Our house doesn't need any heating (due to our comfortable climate) and our power bill is about 2.5kWh per day. And I work from home. That works out to an average of about 100W continuous, so the US and canada would need, at that power level, about 24GW of generation capacity. "Hydro-Québec is the world's largest hydroelectric generating company, with a total installed capacity (2005) of 31,512 MW"
So hydro alone could provide all the real electricity needs of houses in the US and canada. Why isn't this enough in practice? Because despite the fact that 100% solar heating of houses as far north as alaska is practical, maybe 0.1% of domestic heating is provided by solar. Similarly, americans throw away 84% of Al drink cans, requiring 20 times more electrical energy than to recycle them (including the fuel to pick up the cans etc).
So forget about electricity. Lets talk about heat. lets say you live in gloomsville, with no sun (perhaps due to being built in a canyon). How could you heat your house more efficiently? Using a cogeneration system would produce 1J of electricity and 4J of heat for every 5J of fuel used. Compare this to people using resistance heating in their houses, which produce 1J of heat for every 3J of nuclear fuel. If you generate electricity in a nuclear plant you will rarely get more than about 35% of the energy released usable as electricity, and you lose more carrying that energy to the house.
So, yes, a larger generator may have a higher carnot efficiency (you missed some issues, incidently, the MPT efficiency of a large heat exchanger is higher than a small one, and losses due to surface area are much higher in smaller engines). But a local generator produces heat where it is used, rather than very inefficiently moving it around the countryside.
Some other advantages of decentralised power including redundancy and availability (which you touched on), demand scaling, more rapid efficiency improvements due to smaller devices (there is a reason why prius car batteries are made using NiMH C cells - the huge consumer demand means the techonology is a lot more refined), ability to use small scale power (wood fired diesel engine perhaps?) and reduction in transmission losses.
Centralised electrical power is very 19th century, and perhaps should go the same way as centralised computing, centralised networking, centralised transport etc. There is so much stuff we can do, but the people who have the keys to the power stations and oil pumps don't want us to think about them.
Our house uses 5 evacuated tube collectors with an aluminium reflector behind them for a collection area of about 1m^2 for two people who have 10 minutes showers every day.
No idea, but my 2000 powerbook battery still works fine. The hybrid vehicles have a 10 year warranty on the battery and they expect the batteries to last 15 years or 240000km. Telcos measure battery lives in decades.
But for the majority of energy demand we don't need storage. We don't need electricity, we don't need storage. So why are those two technologies the major stumbling block in your eyes? It seems to me that we should be thinking about how to offset the big demands (process heat, hot water, building heat) first. And these are easy/solved problems.
We also never before had the advanced information infrastructure, nor the ability to make machines with COP measured in the billions. We know vastly more now than we did inthe 19th century. I'm full of hope as a result.
People have demonstrated being able to live self-sufficiently on say 1000m^2 of land. There is enough land like this for everyone to have some, yep, all 6.5billion of us. 1*10^14 m^2 of land means we have 23 times this amount world wide. As people become more affluent the breeding rate drops.
People are choosing to downshift their liftstyle already, without significant economic, environmental or political pressure. And you haven't demonstrated that a reduction in energy use is equivalent to a 'reduction in lifestyle' (heck, you haven't even defined what you mean by a 'reduction in lifestyle').
Is riding to work on a bicycle rather than going to the gym a reduction in lifestyle? Is eating a shared meal with your neighbours rather than eating in some fast food joint halfway across town a reduction in lifestyle? Is picking fruit from your own tree rather than buying from a supermarket a reductionin lifestyle?
I know you only wrote that as a throwaway line, but perhaps you could spend some time thinking about why you said it in the first place.
No. Even if every human on this planet used as much as an average american, and we used existing technology to produce all the energy from the sun, the effect on the environment would be only a few percent. Take those numbers posted: 10^5 TW hits the earth, average demand by humans is 13TW or one thousandth the energy that hits the earth. And even if we had perfect solar collectors (with an efficiency of 95%), the waste heat would still mostly hang around. We already affect the microclimate using vast expanses of bitumen, yet this has no measurable effect on the global picture.
Firstly, a TW is a unit of power, not energy. Secondly, electricity is a very small part of our total energy demand, even domestic heating is a larger piece of the energy pie. And domestic heating with the sun is easy.
We can fix some technical problems. We haven't solved the technical problems with fusion, despite 50 years of enthusiatic and well funded research. (and many would argue we haven't solved the technical problems with fission either)
Electric cars certainly produce less particulates against ICE cars. coal power stations go to a lot of trouble to remove particulates.
As for CO2, a coal powerstation is about 35% efficient at converting C to electricity, a LiIon battery is about 80% efficient round trip, and electric transmissions are about 90% efficient. The overall efficiency is thus about 25% C to miles.
ICE engines are on average about 15% efficient at converting C into miles.
Thanks for the interesting post. I was referring to convection as a heat transfer mechanism to protective clothing, where it is fairly minor compared to the radiation. What you are referring to is actually 'stratification', where different temperature fluid separates out.
The exapnsion depends on the pressure and temperature (PV = nRT). At the higher temperatures in a fire the water might expand 20000 times.
I think you are right, the problem in a fire is the radiant energy (hence the silver suits. Conduction (negligable) and convection (minor) can be handled by suitably foamly materials, but radiation will melt your mask in no time flat.
I guess you might be able to partially mirror the outside of the mask to help this.
You might be a firefighter, but you're not a rocket scientist, or a materials engineer. Perhaps they've actually tested this material? You might be surprised at how much energy evaporating water can take away. 2.2MJ/kg
The bullcrap was about lightning prevention (sorry, I should have made that clear) and that the conductor isn't rated to survive a lightning hit. Parallel path seems very unlikely considering the available conductor density. If there were a parallel discharge one would expect melting or charring around conductors, either of which I've not seen.
The resistance of the lightning rod might be 1000th the resistance of the whole strike (from cloud to ground), so although a lightning bolt has a high power, most of that power is being dissipated elsewhere. Lets work it out:
An average bolt of negative lightning carries a current of 30 kiloamperes, transfers a charge of 5 coulombs, has a potential difference of about 100 megavolts and dissipates 500 megajoules (enough to light a 100 watt lightbulb for 2 months).
You have: 100MV/30kA You want: ohm
* 3333.3333
so a lightning discharge has a total resistance of 3K3 over say a distance of 3.3km, for a plasma resistance of 1ohm/m, nearly ten thousand times greater than that of the lightning rod, so it is unlikely that the lightning would choose to make its own path, and if it did, we would expect only 1/10000th the current to flow (a measly 3A).
I promise I will never start a post with 'bullcrap' again, it's unhelpful to the discussion.
Slashdot Mirror
We know that humanity can live without burning fossil fuels or nuclear fuels. (So what? well it means that we could just give up on fossil fuels over night if we had to. It would destroy all of civilisation, but given a choice between than a total anhiliation, perhaps we would choose that.)
:)
There are plenty of gasses with GWP less than 1. N2 for example. The gas with a GWP of 21000 is probably SF6, a popular gas for high voltage insulation.
CO2 levels have been much much higher in the past, and apparently with similar transition times as currently. Life prevailed. Big animals may not have
Ok, you haven't addressed my remark that heating is more important than electricity, but let me give you some things to think about regarding decentralised electricity, for example.
PVs are probably a red herring. They are all made by oil companies, so even were they viable, the oil companies will keep them at a price to maintain the oil demand. I have never advocated PVs in this discussion.
Batteries are also a red herring. If our demand were just lights and electronic devices we could supply everyone in the US using wind and hydro alone. The problem is mainly heating. Our house doesn't need any heating (due to our comfortable climate) and our power bill is about 2.5kWh per day. And I work from home. That works out to an average of about 100W continuous, so the US and canada would need, at that power level, about 24GW of generation capacity. "Hydro-Québec is the world's largest hydroelectric generating company, with a total installed capacity (2005) of 31,512 MW"
So hydro alone could provide all the real electricity needs of houses in the US and canada. Why isn't this enough in practice? Because despite the fact that 100% solar heating of houses as far north as alaska is practical, maybe 0.1% of domestic heating is provided by solar. Similarly, americans throw away 84% of Al drink cans, requiring 20 times more electrical energy than to recycle them (including the fuel to pick up the cans etc).
So forget about electricity. Lets talk about heat. lets say you live in gloomsville, with no sun (perhaps due to being built in a canyon). How could you heat your house more efficiently? Using a cogeneration system would produce 1J of electricity and 4J of heat for every 5J of fuel used. Compare this to people using resistance heating in their houses, which produce 1J of heat for every 3J of nuclear fuel. If you generate electricity in a nuclear plant you will rarely get more than about 35% of the energy released usable as electricity, and you lose more carrying that energy to the house.
So, yes, a larger generator may have a higher carnot efficiency (you missed some issues, incidently, the MPT efficiency of a large heat exchanger is higher than a small one, and losses due to surface area are much higher in smaller engines). But a local generator produces heat where it is used, rather than very inefficiently moving it around the countryside.
Some other advantages of decentralised power including redundancy and availability (which you touched on), demand scaling, more rapid efficiency improvements due to smaller devices (there is a reason why prius car batteries are made using NiMH C cells - the huge consumer demand means the techonology is a lot more refined), ability to use small scale power (wood fired diesel engine perhaps?) and reduction in transmission losses.
Centralised electrical power is very 19th century, and perhaps should go the same way as centralised computing, centralised networking, centralised transport etc. There is so much stuff we can do, but the people who have the keys to the power stations and oil pumps don't want us to think about them.
Oh well, if it is practical, it will happen sooner or later. I suspect humanity needs fusion if we are to graduate to 'space faring'.
So are you saying that if fusion were only funded 10 times as much, we'd have fusion power now?
I'm happy to discuss this via email, slashdot is a poor way to have a discussion. email me at sustainability@njhurst.com
Our house uses 5 evacuated tube collectors with an aluminium reflector behind them for a collection area of about 1m^2 for two people who have 10 minutes showers every day.
No idea, but my 2000 powerbook battery still works fine. The hybrid vehicles have a 10 year warranty on the battery and they expect the batteries to last 15 years or 240000km. Telcos measure battery lives in decades.
Nope, but then you haven't given any real data either :-)
But for the majority of energy demand we don't need storage. We don't need electricity, we don't need storage. So why are those two technologies the major stumbling block in your eyes? It seems to me that we should be thinking about how to offset the big demands (process heat, hot water, building heat) first. And these are easy/solved problems.
We also never before had the advanced information infrastructure, nor the ability to make machines with COP measured in the billions. We know vastly more now than we did inthe 19th century. I'm full of hope as a result.
People have demonstrated being able to live self-sufficiently on say 1000m^2 of land. There is enough land like this for everyone to have some, yep, all 6.5billion of us. 1*10^14 m^2 of land means we have 23 times this amount world wide. As people become more affluent the breeding rate drops.
What are you doing about it?
Why do you want centralised power generation?
People are choosing to downshift their liftstyle already, without significant economic, environmental or political pressure. And you haven't demonstrated that a reduction in energy use is equivalent to a 'reduction in lifestyle' (heck, you haven't even defined what you mean by a 'reduction in lifestyle').
Is riding to work on a bicycle rather than going to the gym a reduction in lifestyle? Is eating a shared meal with your neighbours rather than eating in some fast food joint halfway across town a reduction in lifestyle? Is picking fruit from your own tree rather than buying from a supermarket a reductionin lifestyle?
I know you only wrote that as a throwaway line, but perhaps you could spend some time thinking about why you said it in the first place.
No. Even if every human on this planet used as much as an average american, and we used existing technology to produce all the energy from the sun, the effect on the environment would be only a few percent. Take those numbers posted: 10^5 TW hits the earth, average demand by humans is 13TW or one thousandth the energy that hits the earth. And even if we had perfect solar collectors (with an efficiency of 95%), the waste heat would still mostly hang around. We already affect the microclimate using vast expanses of bitumen, yet this has no measurable effect on the global picture.
I don't understand your question?
:-) I had one of those cars, gave it to the wreckers in the end.
Firstly, a TW is a unit of power, not energy. Secondly, electricity is a very small part of our total energy demand, even domestic heating is a larger piece of the energy pie. And domestic heating with the sun is easy.
"may still be our only hope, because changing the lifestyles of billions of people isn't possible."
We done it many times before. Or do you believe that humans have always driven cars to work?
We can fix some technical problems. We haven't solved the technical problems with fusion, despite 50 years of enthusiatic and well funded research. (and many would argue we haven't solved the technical problems with fission either)
Electric cars certainly produce less particulates against ICE cars. coal power stations go to a lot of trouble to remove particulates.
As for CO2, a coal powerstation is about 35% efficient at converting C to electricity, a LiIon battery is about 80% efficient round trip, and electric transmissions are about 90% efficient. The overall efficiency is thus about 25% C to miles.
ICE engines are on average about 15% efficient at converting C into miles.
Plug in hybrids probably make more sense.
Thanks for the interesting post. I was referring to convection as a heat transfer mechanism to protective clothing, where it is fairly minor compared to the radiation. What you are referring to is actually 'stratification', where different temperature fluid separates out.
The exapnsion depends on the pressure and temperature (PV = nRT). At the higher temperatures in a fire the water might expand 20000 times.
I think you are right, the problem in a fire is the radiant energy (hence the silver suits. Conduction (negligable) and convection (minor) can be handled by suitably foamly materials, but radiation will melt your mask in no time flat.
I guess you might be able to partially mirror the outside of the mask to help this.
You might be a firefighter, but you're not a rocket scientist, or a materials engineer. Perhaps they've actually tested this material? You might be surprised at how much energy evaporating water can take away. 2.2MJ/kg
How would you test your hypothesis?
I did too. I never considered that you could deduce the resistance of a lightning breakdown until your post.
The bullcrap was about lightning prevention (sorry, I should have made that clear) and that the conductor isn't rated to survive a lightning hit. Parallel path seems very unlikely considering the available conductor density. If there were a parallel discharge one would expect melting or charring around conductors, either of which I've not seen.
The resistance of the lightning rod might be 1000th the resistance of the whole strike (from cloud to ground), so although a lightning bolt has a high power, most of that power is being dissipated elsewhere. Lets work it out:
An average bolt of negative lightning carries a current of 30 kiloamperes, transfers a charge of 5 coulombs, has a potential difference of about 100 megavolts and dissipates 500 megajoules (enough to light a 100 watt lightbulb for 2 months).
You have: 100MV/30kA
You want: ohm
* 3333.3333
so a lightning discharge has a total resistance of 3K3 over say a distance of 3.3km, for a plasma resistance of 1ohm/m, nearly ten thousand times greater than that of the lightning rod, so it is unlikely that the lightning would choose to make its own path, and if it did, we would expect only 1/10000th the current to flow (a measly 3A).
I promise I will never start a post with 'bullcrap' again, it's unhelpful to the discussion.