I felt a great disturbance in the Force, as if millions of voices suddenly cried out in terror and were suddenly silenced. I fear something terrible has happened.
Um, yeah. I had one of those, and elegant is not a word that was used to describe them, even when new.
Elegant depends upon context, and I would argue that those computers were elegant in the context of their era. Difficult to use, sure. Yet compare that to the technology that preceded it. If you needed to type something out, typewriters sure were simple. Needed to make changes, then you needed to use a correction tape. Except that wasn't always appropriate, so you had that thing called drafts. {snip}Spreadsheets {snip} Accounting software {snip}
We're talking about a ZX Spectrum, right?
I know they had a Word-processor and probably a spreadsheet for the Speccy, but that's hardly an average use case.
Manic Miner and Jet Set Willy were elegant tho, elegant and awesome!
Hidenburg era airships didn't have plastics to make the gasbags from, modern Hydrogen airships could be safer than petrol powered road vehicles which crash and burn regularly.
The difficulty with all large, lighter than air craft is ground handling. You have a massive, bouyant structure and a small breath of air results in a huge amount of momentum which can all too easily result in the airship hitting things and damaging itself or them.
The solution is to never come below 30,000 feet, higher if the ground rises, launch once and use triplanes to get on and off.
All the clever sensing is done by the bacteria, all they've done is attach a big flag to the bacteria so that when it does what it does we can tell.
Whilst this may be very useful, it's hardly outwitting nature, or creating new forms of life, or doing anything that'd be likely to be disastrous in any way.
It's as tho putting a radio collar on a polar bear turns it into some cyborg killing machine.
Wowsers, you either use a fuck-ton of electricity or have a remarkably small roof area.
I just looked it up, in 2014 we used 25155 kWh of electric.
Is that "a lot"? I don't know... It is about 20% less overall than it was the year before, when we replaced our HVAC system with a much better one, so that helps...
Well the average uk household uses 4.6 MWh/year so yeah, you use 5 times what I'm used to having to provide. I suppose that's the price of living in desert and not acclimatising your body to the heat.
To replace 100% of the power we use, we'd need about a 18 kW system.
At $4 a watt installed (grid tie, inverters, second meter, etc.) it would cost $70,000 to install that (probably less given the size), assuming it would even fit, which it won't.
We have no city/state rebate worth talking about, but the 30% federal rebate is nice, giving me an after tax cost of $49,000.
The payback is about 18 years, give or take a few, since I pay 11 cents per kWh today. My price per kWh over 20 years? about 9 cents, so it DOES save me money, IF I stay here 20 years, and if I want to put all that cash out up front. If I finance it, the interest eats up the savings and costs a bit more.
Which is all beside the point, such a system wouldn't fit on my roof. I can get about a 6 kW system on my roof, cutting all those numbers by a third.
It would cost me about $25,000 up front ($17K after taxes) to install such a system, all to save $100 a month on my power bill.
It's worth noting that installing renewable energy generating kit on your roof will increase the value of your house. So even if you decide to leave before you've paid off the costs of the installation you should be able to recoup all your investment by increasing the sale price of the house.
But really you need to address your flagrant overuse of electricity.
Might I suggest wearing fewer clothes;P
Seriously maybe think about redesigning your dwelling to be passively/naturally cool, I recall seeing a system of vents with damp cloths hung under the house to "aircon" homes in the outback (no grid so power is a series expense out there) which worked quite well, and I suspect that the Egyptians and so forth also know a thing or two about keeping buildings cool in hot places without having to run a compressor.
Wowsers, you either use a fuck-ton of electricity or have a remarkably small roof area.
I installed PV for 10 years in.uk (a much less sunny place than.tx) and was able, in most cases, to offset people's entire annual usage with a north/south roof, east/west roofs present much more of a challenge.
It is cheaper, and more optimal electrically, to sell the power to the grid and then buy it back from another generator when you aren't generating
It is even cheaper and more optimal electrically, if your electric utility owns the solar panels and sells you the electricity from them when you need it.
The ownership of the panels barely affects their electrical function, I suppose there might be some efficiencies of scale if the utility own all the panels on all the roofs in the street and can wire them all up to one big inverter. But as big inverters tend to be made up of lots of small inverters I'm not even sure if this is true.
There does tend to be an ownership issue with roofspace tho, there are some companies who rent roofspace from individuals install PV and then profit from being the middleman, but that tends to be less financially rewarding for the roof owner and as the capital investment for a small (~4kW peak) system is relatively low (~$8k I'd guess) it's not a model that's often used. The utility very infrequently owns power stations, even the big ones, they tend to be owned by private enterprise and then trade electricity to the utility, or at least that's how it is here in.uk
I agree completely but few people are working on storage as it is not sexy. They are content with pointing the finger at conventional plants and saying they will handle it. Sorry but the cost of power from conventional plants will rise if they only produce at night.
I cannot help that much of the world is deluded. That is not an Engineering problem. I also discourage engineers who seek to work on sexy projects.
PV has fallen more sharply than the price of lead acid batteries
Lead acid batteries have long been known to be a poor solution to store large amounts of electricity. They take up lots of room, produce dangerous hydrogen gas and need to be maintained.
Oh indeed, but if we're talking about domestic scale storage then lead-acid is the solution most people go for. Although someone here was on about Iron-Nickel. Regardless, I agree chemo-electric storage is useful for it's portability, but it's energy density, in-out efficiency and leakage rates mean it's not really suited for Grid scale storage, with the possible exception of Vanadium flow, http://www.triplepundit.com/2014/12/vanadium-flow-batteries-gaining-commercial-clean-tech-traction/
the energy market needs to be restructured so as to make storing energy profitable,
The cost of storage will always be high.
But the costs to mankind of not sorting the energy issue is likely higher, but far more difficult to express in monetary value.
Today there are very few large scale storage systems like pumped hydro and compressed air storage. Both of these technologies need very specific conditions and can only be used in very few places.Sorry but battery storage is not a large scale solution as it is extremely expensive.
There's a few more active players Pumped Heat, Hot Salt, Tidal Lagoons, Steam Accumulators, Raising a Weight, the technologies exist, it's just noone wants to invest in them because there is no market for storing energy.
Having said that, the cost of a storage system used to double the cost of a 3-4 kW (peak) PV system about 5 years ago. I expect since then the prices of PV has fallen more sharply than the price of lead acid batteries, meaning it may well now triple, but still it's hardly "very expensive".
It is cheaper, and more optimal electrically, to sell the power to the grid and then buy it back from another generator when you aren't generating. Of course that doesn't work if everyone is using the same kind of generators and there's no storage, which is why we need storage. As many storage technologies suffer from efficiencies of scale it probably makes more sense to at least partially centralise the storage.
What probably needs to happen (it certainly needs to happen in.uk) is the energy market needs to be restructured so as to make storing energy profitable, then companies will set up to do it.
See there's a not often remembered problem with horses and population density.
Shit. Yes, that's the problem, not just me being rude.
Before the invention of the horseless carriage London was suffering greatly from a horse-shit re-distribution issue, the plan always was to load the shit onto barges and ship it downstream to Kent (that Kent is know as "The Garden of England" is a not unrelated fact), but there were serious issues with the collection of all the turds and their loading onto the barges.
So whilst there's many great benefits from using beasts of burden (you can always eat your ride if it breaks down) they are not a universal panacea.
Surely, if we want to define a Proper English, it should be English English[0], all 287 dialects of it http://sounds.bl.uk/accents-and-dialects/survey-of-english-dialects
English has always been a bastardised language, an amalgam of tribal languages specifically chosen to baffle the foreigner (read French courts of the middle ages) and then augmented with every interesting word in every language spoken in every port the Navy got to.
It's flexibility and adaptability is the foundation of it's strength, expecting it to remain static is just crazy.
Pumped Hydro has the advantage that there very little leakage loss from the store, and in fact if you put the top lake in a place where it rains a lot the store gets topped up for free.
I don't know of another storage technology that has this advantage.
Having said that maybe 80% in-out is good enough, and a mix of storage technologies is probably a good idea at this time, so, to be clear, it's not that I'm against batteries in houses, just that I don't think that will answer all of the issues required to be solved to produce the renewables + storage solution I'm looking for, and other, more centralised stores will be required.
I've heard of a Canadian housing development that uses solar thermal (water in black pipes on the roof) to heat up a big underground gravel store to keep the heat until winter when it's used to provide a district heating system, which probably isn't that efficient but it's effective enough and reasonably cheap, and very maintainable.
All this is irrelevant. Uranium, is limited in supply, even if it's a large supply. This limit means we will eventually have to stop using it and use something else. So why bother starting?
Really? You're saying that because there's only a couple thousand years of our current energy needs sitting there, we shouldn't use it at all because it's only a couple thousand years? It's better to continue burning chunks of mountain and turning them into clouds of shit that kills people because we don't have a permanent lasts-longer-than-civilization-has-been-here energy source?
No, I'm saying we have 2 options, both of which seem viable. One is develop a renewables + storage energy solution which will potentially last until the sun expires and the other involves adding nuclear to the mix. The nuclear portion will only be usable, for at best 0.0001% of the time we'll be using the other option and will cost significant resources and effort to implement and safely decommission, that would, in the big scheme of things seem to be a waste of those resources.
Of course if you have a more short term view then you may draw different conclusions. I admit that it probably counts as hopeless optimism that we'll live long enough for these things to matter, but planning for ones own demise seems needlessly depressive.
I do not now and will never advocate coal. I agree nuclear is better than coal, but neither stacks up against renewables + storage well.
The difference between optimal and common alignments is pretty minimal.
Here's a graph of solar loss due to incorrect orientation for the UK. http://solsticeenergy.co.uk/common/img/roof_chart_500.gif
It shows that a flat panel (ie pointing straight up) loses 10%, and a vertical one loses 20%
Slewing 45 degrees from optimal (ie SE or SW) incurs a 4% loss and there's less than a 1% loss involved in moving between 30deg pitch and 40deg pitch.
These numbers (both the optimal pitch and the losses) will vary with latitude, but it's safe to say that minor mis-alignments do not affect the performance of PV significantly.
The advantage to using building as mounts for PV is that you don't need to pay (energy or $s) to construct the mount, and the people in the building feel included and often then go on to do other green things, like not use as much power, which is good. I'm pretty sure these benefits easily offset the loss of power generation due to not being optimally aligned.
Having said that centralised power stations can also use technologies that require more maintenance, such as concentrating solar, so there's benefits to both.
What is the functional life expectancy of a solar panel? The source may be permanent, but the power generator is not even close to it.
Current PV degrades at approx 1% of output per year. Thus people claim it has a 20year lifetime, as after 20 years it only produces 80% of the peak output it did when it was new. I have no idea why this 20year/80% figure is chosen as the point at which it stops being useful, but that's the figure people quote.
Having said that all sorts of power stations have parts that need replacing, it's called maintenance.
From http://www.withouthotair.com/c25/page_178.shtml
So the correct statement about power from the Sahara is that today’s consumption could be provided by a 1000 km by 1000 km square in the desert, completely filled with concentrating solar power.
That's about 1/10th of the area of the Sahara, and there's not many trees there.
Of course it would be insane to generate all the power there, and there are other renewable sources which are more viable in areas far from sunny places, and we're horrible wastrels of power because it's cheap.
Having said all that, I agree, the storage solution needs to be 90%+ in-out efficiency.
I had not heard of nickel-iron batteries before this[0], but they don't look promising:
"Due to its low specific energy, poor charge retention, and high cost of manufacture, other types of rechargeable batteries have displaced the nickel–iron battery in most applications" The poor charge retention seems to suggest that the in-out efficiency will be low as well.
There are other chemical batteries that would be better, http://en.wikipedia.org/wiki/Vanadium_redox_battery springs to mind, and the sodium sulfur, you mention also has potential, but none of these seem to be as good as pumped hydro or pumped heat, tho maybe being a Mechanical thermodynamic/fluids guy biases me unfairly against the chemical storage.
Having said all that, my initial point was one of economies/effciencies of scale and I do not think your suggestions deny that, the best storage technology has yet to be developed, but storage technology is where it's at regardless of what power source you wish to use, even Nuclear could do with buffers to smooth out the lumps in the demand curve.
[0] My chemistry is good enough to know that you can make a battery out of any two dissimilar metals and an electrolyte, I'd just not specifically heard of Ni-Fe ones.
Lead Acid batteries are tricky to maintain and if not maintained well then their in-out efficiency falls ~50% pretty quickly.
Li-ion is better on both fronts, but Lithium is scarce.
There are other storage technologies, Pumped Hydro http://www.fhc.co.uk/dinorwig.htm being the most tried and tested one, but Pumped Heat http://www.isentropic.co.uk is being developed now, and there's Tidal lagoons, and hot salt, however none of these are domestic in scale.
I think in general economies of scale and effciencies of scale mean the storage will be done on the grid and not in the house, much like Gasometers http://upload.wikimedia.org/wikipedia/commons/1/14/London-Bristol-gasometer-2.jpg for the gas grid.
All this is irrelevant. Uranium, is limited in supply, even if it's a large supply. This limit means we will eventually have to stop using it and use something else. So why bother starting?
The sun will one day burn out and not provide solar energy, eventually we will have to stop using it and use something else. So why bother starting?
Because when the sun burns out we need to find a new home anyway. It's also 4 orders of magnitude further away than the best projections for fissile fuel on earth.
There's also the argument that as we have the sun here and now, we can save the other energy resources for when we don't have the sun, because we can't do that the other way round.
Slashdot Mirror
I felt a great disturbance in the Force, as if millions of voices suddenly cried out in terror and were suddenly silenced. I fear something terrible has happened.
Um, yeah. I had one of those, and elegant is not a word that was used to describe them, even when new.
Elegant depends upon context, and I would argue that those computers were elegant in the context of their era. Difficult to use, sure. Yet compare that to the technology that preceded it. If you needed to type something out, typewriters sure were simple. Needed to make changes, then you needed to use a correction tape. Except that wasn't always appropriate, so you had that thing called drafts. {snip}Spreadsheets {snip} Accounting software {snip}
We're talking about a ZX Spectrum, right?
I know they had a Word-processor and probably a spreadsheet for the Speccy, but that's hardly an average use case.
Manic Miner and Jet Set Willy were elegant tho, elegant and awesome!
Hydrogen is less explosive than petrol.
Hidenburg era airships didn't have plastics to make the gasbags from, modern Hydrogen airships could be safer than petrol powered road vehicles which crash and burn regularly.
The difficulty with all large, lighter than air craft is ground handling. You have a massive, bouyant structure and a small breath of air results in a huge amount of momentum which can all too easily result in the airship hitting things and damaging itself or them.
The solution is to never come below 30,000 feet, higher if the ground rises, launch once and use triplanes to get on and off.
Relevant picture
All the clever sensing is done by the bacteria, all they've done is attach a big flag to the bacteria so that when it does what it does we can tell.
Whilst this may be very useful, it's hardly outwitting nature, or creating new forms of life, or doing anything that'd be likely to be disastrous in any way.
It's as tho putting a radio collar on a polar bear turns it into some cyborg killing machine.
Corporation tax is typically 20% https://www.gov.uk/corporation-tax-rates/rates and so yes it is more than they would have had to pay.
and yes, this is a semi-futile move on behalf of the HMRC, because the bean counters have already worked out how to avoid it, but c'est la vie.
Wowsers, you either use a fuck-ton of electricity or have a remarkably small roof area.
I just looked it up, in 2014 we used 25155 kWh of electric.
Is that "a lot"? I don't know... It is about 20% less overall than it was the year before, when we replaced our HVAC system with a much better one, so that helps...
Well the average uk household uses 4.6 MWh/year so yeah, you use 5 times what I'm used to having to provide. I suppose that's the price of living in desert and not acclimatising your body to the heat.
To replace 100% of the power we use, we'd need about a 18 kW system.
At $4 a watt installed (grid tie, inverters, second meter, etc.) it would cost $70,000 to install that (probably less given the size), assuming it would even fit, which it won't.
We have no city/state rebate worth talking about, but the 30% federal rebate is nice, giving me an after tax cost of $49,000.
The payback is about 18 years, give or take a few, since I pay 11 cents per kWh today. My price per kWh over 20 years? about 9 cents, so it DOES save me money, IF I stay here 20 years, and if I want to put all that cash out up front. If I finance it, the interest eats up the savings and costs a bit more.
Which is all beside the point, such a system wouldn't fit on my roof. I can get about a 6 kW system on my roof, cutting all those numbers by a third.
It would cost me about $25,000 up front ($17K after taxes) to install such a system, all to save $100 a month on my power bill.
It's worth noting that installing renewable energy generating kit on your roof will increase the value of your house. So even if you decide to leave before you've paid off the costs of the installation you should be able to recoup all your investment by increasing the sale price of the house.
But really you need to address your flagrant overuse of electricity.
Might I suggest wearing fewer clothes ;P
Seriously maybe think about redesigning your dwelling to be passively/naturally cool, I recall seeing a system of vents with damp cloths hung under the house to "aircon" homes in the outback (no grid so power is a series expense out there) which worked quite well, and I suspect that the Egyptians and so forth also know a thing or two about keeping buildings cool in hot places without having to run a compressor.
Wowsers, you either use a fuck-ton of electricity or have a remarkably small roof area.
I installed PV for 10 years in .uk (a much less sunny place than .tx) and was able, in most cases, to offset people's entire annual usage with a north/south roof, east/west roofs present much more of a challenge.
It is cheaper, and more optimal electrically, to sell the power to the grid and then buy it back from another generator when you aren't generating
It is even cheaper and more optimal electrically, if your electric utility owns the solar panels and sells you the electricity from them when you need it.
The ownership of the panels barely affects their electrical function, I suppose there might be some efficiencies of scale if the utility own all the panels on all the roofs in the street and can wire them all up to one big inverter. But as big inverters tend to be made up of lots of small inverters I'm not even sure if this is true.
There does tend to be an ownership issue with roofspace tho, there are some companies who rent roofspace from individuals install PV and then profit from being the middleman, but that tends to be less financially rewarding for the roof owner and as the capital investment for a small (~4kW peak) system is relatively low (~$8k I'd guess) it's not a model that's often used. The utility very infrequently owns power stations, even the big ones, they tend to be owned by private enterprise and then trade electricity to the utility, or at least that's how it is here in .uk
http://www.tomshardware.com/reviews/mechanical-switch-keyboard,2955-18.html
Storage is today's big issue in the energy world.
I agree completely but few people are working on storage as it is not sexy. They are content with pointing the finger at conventional plants and saying they will handle it. Sorry but the cost of power from conventional plants will rise if they only produce at night.
I cannot help that much of the world is deluded. That is not an Engineering problem. I also discourage engineers who seek to work on sexy projects.
PV has fallen more sharply than the price of lead acid batteries
Lead acid batteries have long been known to be a poor solution to store large amounts of electricity. They take up lots of room, produce dangerous hydrogen gas and need to be maintained.
Oh indeed, but if we're talking about domestic scale storage then lead-acid is the solution most people go for. Although someone here was on about Iron-Nickel. Regardless, I agree chemo-electric storage is useful for it's portability, but it's energy density, in-out efficiency and leakage rates mean it's not really suited for Grid scale storage, with the possible exception of Vanadium flow, http://www.triplepundit.com/2014/12/vanadium-flow-batteries-gaining-commercial-clean-tech-traction/
the energy market needs to be restructured so as to make storing energy profitable,
The cost of storage will always be high.
But the costs to mankind of not sorting the energy issue is likely higher, but far more difficult to express in monetary value.
Today there are very few large scale storage systems like pumped hydro and compressed air storage. Both of these technologies need very specific conditions and can only be used in very few places.Sorry but battery storage is not a large scale solution as it is extremely expensive.
There's a few more active players Pumped Heat, Hot Salt, Tidal Lagoons, Steam Accumulators, Raising a Weight, the technologies exist, it's just noone wants to invest in them because there is no market for storing energy.
Storage is today's big issue in the energy world.
Having said that, the cost of a storage system used to double the cost of a 3-4 kW (peak) PV system about 5 years ago. I expect since then the prices of PV has fallen more sharply than the price of lead acid batteries, meaning it may well now triple, but still it's hardly "very expensive".
It is cheaper, and more optimal electrically, to sell the power to the grid and then buy it back from another generator when you aren't generating. Of course that doesn't work if everyone is using the same kind of generators and there's no storage, which is why we need storage. As many storage technologies suffer from efficiencies of scale it probably makes more sense to at least partially centralise the storage.
What probably needs to happen (it certainly needs to happen in .uk) is the energy market needs to be restructured so as to make storing energy profitable, then companies will set up to do it.
Whilst what you say is true there's the refilling time to take into account.
A full tank of liquid fuel takes minutes to pour in.
A full 'tank' of electricity takes hours.
Not to mention that a full tank of liquid fuel gets you about 700 miles of travel whereas a full battery only ~350
It's called a horse.
See there's a not often remembered problem with horses and population density.
Shit. Yes, that's the problem, not just me being rude.
Before the invention of the horseless carriage London was suffering greatly from a horse-shit re-distribution issue, the plan always was to load the shit onto barges and ship it downstream to Kent (that Kent is know as "The Garden of England" is a not unrelated fact), but there were serious issues with the collection of all the turds and their loading onto the barges.
So whilst there's many great benefits from using beasts of burden (you can always eat your ride if it breaks down) they are not a universal panacea.
Surely, if we want to define a Proper English, it should be English English[0], all 287 dialects of it http://sounds.bl.uk/accents-and-dialects/survey-of-english-dialects
English has always been a bastardised language, an amalgam of tribal languages specifically chosen to baffle the foreigner (read French courts of the middle ages) and then augmented with every interesting word in every language spoken in every port the Navy got to.
It's flexibility and adaptability is the foundation of it's strength, expecting it to remain static is just crazy.
[0] Yes this is a troll for all you usian mods.
I think that documentation may be the more pressing need
But the code IS the documentation!!!!
Now there's a chance we can have Ganymedian dolphin pilots for our star cruisers!!!
Pumped Hydro has the advantage that there very little leakage loss from the store, and in fact if you put the top lake in a place where it rains a lot the store gets topped up for free.
I don't know of another storage technology that has this advantage.
Having said that maybe 80% in-out is good enough, and a mix of storage technologies is probably a good idea at this time, so, to be clear, it's not that I'm against batteries in houses, just that I don't think that will answer all of the issues required to be solved to produce the renewables + storage solution I'm looking for, and other, more centralised stores will be required.
I've heard of a Canadian housing development that uses solar thermal (water in black pipes on the roof) to heat up a big underground gravel store to keep the heat until winter when it's used to provide a district heating system, which probably isn't that efficient but it's effective enough and reasonably cheap, and very maintainable.
All this is irrelevant. Uranium, is limited in supply, even if it's a large supply. This limit means we will eventually have to stop using it and use something else. So why bother starting?
Really? You're saying that because there's only a couple thousand years of our current energy needs sitting there, we shouldn't use it at all because it's only a couple thousand years? It's better to continue burning chunks of mountain and turning them into clouds of shit that kills people because we don't have a permanent lasts-longer-than-civilization-has-been-here energy source?
No, I'm saying we have 2 options, both of which seem viable. One is develop a renewables + storage energy solution which will potentially last until the sun expires and the other involves adding nuclear to the mix. The nuclear portion will only be usable, for at best 0.0001% of the time we'll be using the other option and will cost significant resources and effort to implement and safely decommission, that would, in the big scheme of things seem to be a waste of those resources.
Of course if you have a more short term view then you may draw different conclusions. I admit that it probably counts as hopeless optimism that we'll live long enough for these things to matter, but planning for ones own demise seems needlessly depressive.
I do not now and will never advocate coal. I agree nuclear is better than coal, but neither stacks up against renewables + storage well.
The difference between optimal and common alignments is pretty minimal.
Here's a graph of solar loss due to incorrect orientation for the UK. http://solsticeenergy.co.uk/common/img/roof_chart_500.gif
It shows that a flat panel (ie pointing straight up) loses 10%, and a vertical one loses 20%
Slewing 45 degrees from optimal (ie SE or SW) incurs a 4% loss and there's less than a 1% loss involved in moving between 30deg pitch and 40deg pitch.
These numbers (both the optimal pitch and the losses) will vary with latitude, but it's safe to say that minor mis-alignments do not affect the performance of PV significantly.
The advantage to using building as mounts for PV is that you don't need to pay (energy or $s) to construct the mount, and the people in the building feel included and often then go on to do other green things, like not use as much power, which is good. I'm pretty sure these benefits easily offset the loss of power generation due to not being optimally aligned.
Having said that centralised power stations can also use technologies that require more maintenance, such as concentrating solar, so there's benefits to both.
But we need to ramp up both wind and solar many fold before we can even think of retiring coal.
Or use less power.
That'd work too.
What is the functional life expectancy of a solar panel? The source may be permanent, but the power generator is not even close to it.
Current PV degrades at approx 1% of output per year. Thus people claim it has a 20year lifetime, as after 20 years it only produces 80% of the peak output it did when it was new. I have no idea why this 20year/80% figure is chosen as the point at which it stops being useful, but that's the figure people quote.
Having said that all sorts of power stations have parts that need replacing, it's called maintenance.
It's not as much land as you imagine, I think.
From http://www.withouthotair.com/c25/page_178.shtml
So the correct statement about power from the Sahara is that today’s consumption could be provided by a 1000 km by 1000 km square in the desert, completely filled with concentrating solar power.
That's about 1/10th of the area of the Sahara, and there's not many trees there.
Of course it would be insane to generate all the power there, and there are other renewable sources which are more viable in areas far from sunny places, and we're horrible wastrels of power because it's cheap.
Having said all that, I agree, the storage solution needs to be 90%+ in-out efficiency.
I had not heard of nickel-iron batteries before this[0], but they don't look promising:
"Due to its low specific energy, poor charge retention, and high cost of manufacture, other types of rechargeable batteries have displaced the nickel–iron battery in most applications" The poor charge retention seems to suggest that the in-out efficiency will be low as well.
There are other chemical batteries that would be better, http://en.wikipedia.org/wiki/Vanadium_redox_battery springs to mind, and the sodium sulfur, you mention also has potential, but none of these seem to be as good as pumped hydro or pumped heat, tho maybe being a Mechanical thermodynamic/fluids guy biases me unfairly against the chemical storage.
Having said all that, my initial point was one of economies/effciencies of scale and I do not think your suggestions deny that, the best storage technology has yet to be developed, but storage technology is where it's at regardless of what power source you wish to use, even Nuclear could do with buffers to smooth out the lumps in the demand curve.
[0] My chemistry is good enough to know that you can make a battery out of any two dissimilar metals and an electrolyte, I'd just not specifically heard of Ni-Fe ones.
Lead Acid batteries are tricky to maintain and if not maintained well then their in-out efficiency falls ~50% pretty quickly.
Li-ion is better on both fronts, but Lithium is scarce.
There are other storage technologies, Pumped Hydro http://www.fhc.co.uk/dinorwig.htm being the most tried and tested one, but Pumped Heat http://www.isentropic.co.uk is being developed now, and there's Tidal lagoons, and hot salt, however none of these are domestic in scale.
I think in general economies of scale and effciencies of scale mean the storage will be done on the grid and not in the house, much like Gasometers http://upload.wikimedia.org/wikipedia/commons/1/14/London-Bristol-gasometer-2.jpg for the gas grid.
All this is irrelevant. Uranium, is limited in supply, even if it's a large supply. This limit means we will eventually have to stop using it and use something else. So why bother starting?
The sun will one day burn out and not provide solar energy, eventually we will have to stop using it and use something else. So why bother starting?
Because when the sun burns out we need to find a new home anyway. It's also 4 orders of magnitude further away than the best projections for fissile fuel on earth.
There's also the argument that as we have the sun here and now, we can save the other energy resources for when we don't have the sun, because we can't do that the other way round.