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Author Topic: Tunisian solar power for Europe  (Read 461 times)
stannn
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« on: August 11, 2017, 02:07:40 PM »

http://www.globalconstructionreview.com/news/plan-supply-europe-tunisian-solar-power-moves-clos/

https://cleantechnica.com/2017/08/11/desertec-sahara-solar-dream-didnt-die-baaaack/
« Last Edit: August 11, 2017, 02:16:58 PM by stannn » Logged

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« Reply #1 on: August 11, 2017, 02:18:34 PM »

Why not just use PV panels?  Ivanpah shows solar towers can work, but they're expensive, use a lot of water and still need a gas supply, plus solar PV panels keep getting cheaper...
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Stig
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« Reply #2 on: August 11, 2017, 02:25:44 PM »

Why not just use PV panels?  Ivanpah shows solar towers can work, but they're expensive, use a lot of water and still need a gas supply, plus solar PV panels keep getting cheaper...

I guess because:
Quote
.. the ability of thermal storage technology to drive the plantís steam turbines during the night as well as the day.

How the economics compare with PV and battery storage would then be the question.
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dhaslam
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« Reply #3 on: August 11, 2017, 04:16:01 PM »

It is probably easier to make the mirrors and towers locally which would keep costs down.   It is of indirect benefit to Europe to have more stable economies in North Africa and solar energy is likely to be on  very large scale eventually.
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« Reply #4 on: August 11, 2017, 04:40:04 PM »

I've been pondering Desertec recently after reading about Australia selling sunlight to Japan. The plan being to generate leccy from solar in Australia, then produce hydrogen, change it into ammonia, then tanker it to Japan, where they need the leccy, but don't have the space/resources of Australia.

How Australia can use hydrogen to export its solar power around the world

This got me to thinking. I appreciate that the P2G2P model has greater losses, but it avoids the capital outlay of the HVDC, and perhaps more importantly the political problems of N. Africa - let me explain, if someone (government or rebels) disrupts the live generation / HVDC then the UK is in trouble instantly. But if the energy is tankered to us, and we have some storage, then use hydrogen fuel cells for the leccy, then we have a time buffer and can't (easily) be blackmailed at any point in time.

Perhaps I'm over thinking this, and perhaps the economics wouldn't stack up, but perhaps a fleet of ammonia ships bringing sunshine to the UK, would be better than LNG and fracking for UK leccy generation.

I've got a suspicion that my idea is total ball locks?
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dan_b
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« Reply #5 on: August 11, 2017, 05:01:30 PM »

Fleets of ammonia tankers sounds just as environmentally damaging as fleets of oil tankers, never mind the energy inefficiency in the round trip with all the chemical conversions, chilling and compression, fuel for transport, food and drink for the employees, chemical spillages etc.   But I suppose it keeps the current petrochemicals industry of moving liquid around the globe in business!

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« Reply #6 on: August 11, 2017, 05:34:59 PM »

Mart you make a good point about the risk of disruption by rebels, but as D Haslam says it would greatly benefit the people of North Africa and more, if they were able to earn a decent living from supplying the world with power they wouldn't be rebels. That's is of course provided we don't go marching in there to nick their sunlight and leave them with nothing.........


Desp
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« Reply #7 on: August 12, 2017, 07:57:40 AM »

Mart you make a good point about the risk of disruption by rebels, but as D Haslam says it would greatly benefit the people of North Africa and more, if they were able to earn a decent living from supplying the world with power they wouldn't be rebels. That's is of course provided we don't go marching in there to nick their sunlight and leave them with nothing.........

Desp

It might be a totally stupid idea, but I was thinking the same countries producing the PV or CSP leccy, but instead of say a 2GW cable, we might have say 5GW of hydrogen fuel cell generation, that just runs of stored hydrogen as and when we want it, even during the African night (though CSP may resolve that). So if a cable or generation plants were shutdown for political or 'naughty' reasons, there would be no instantaneous halt to UK leccy.

I guess it all comes down to comparative costs, and possible scale. For instance I assume that N. Africa has no (effective) limit on potential sunshine to sell, so we could be running say 10GW of fuel cells if the price was cheap enough. There would be a balance of payments issue, but that's happening anyway with Hinkley and foreign LNG.

I did think that 'shipping sunlight' was just an idea, but as Australia and Japan have agreed rules and regs for transporting hydrogen, maybe there is something to it.

In the US they are looking at $30/MWh PV generation already, I assume N. Africa can match or beat that, so would all of the additional costs, and there look to be a lot, still be cheaper than gas generation with a suitable carbon tax? No idea, over to AZPS and PDF me thinks!
« Last Edit: August 12, 2017, 08:00:07 AM by M » Logged

Just call me Mart.     Cardiff: 5.58kWp PV - (3.58kWp SE3500 + 2kWp SE2200 WNW)
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« Reply #8 on: August 12, 2017, 08:32:40 AM »

Fleets of ammonia tankers sounds just as environmentally damaging as fleets of oil tankers, never mind the energy inefficiency in the round trip with all the chemical conversions, chilling and compression, fuel for transport, food and drink for the employees, chemical spillages etc.   But I suppose it keeps the current petrochemicals industry of moving liquid around the globe in business!
Ammonia is required in vast quantities for fertilizer - and is currently made from natural gas. It would seem far more logical to use the ammonia directly for fertilizer, and send the natural gas thus saved to Japan as fuel.
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« Reply #9 on: August 12, 2017, 09:14:50 AM »

It might be a totally stupid idea, but I was thinking the same countries producing the PV or CSP leccy, but instead of say a 2GW cable, we might have say 5GW of hydrogen fuel cell generation, that just runs of stored hydrogen as and when we want it, even during the African night (though CSP may resolve that). So if a cable or generation plants were shutdown for political or 'naughty' reasons, there would be no instantaneous halt to UK leccy.

I guess it all comes down to comparative costs, and possible scale. For instance I assume that N. Africa has no (effective) limit on potential sunshine to sell, so we could be running say 10GW of fuel cells if the price was cheap enough. There would be a balance of payments issue, but that's happening anyway with Hinkley and foreign LNG.

I did think that 'shipping sunlight' was just an idea, but as Australia and Japan have agreed rules and regs for transporting hydrogen, maybe there is something to it.

In the US they are looking at $30/MWh PV generation already, I assume N. Africa can match or beat that, so would all of the additional costs, and there look to be a lot, still be cheaper than gas generation with a suitable carbon tax? No idea, over to AZPS and PDF me thinks!
This isn't a straightforward thing to answer. Essentially, as a fuel electricity is both very cheap to ship and in the most valuable state it can be (round trip efficiency if you convert it to a liquid for shipping is about 30%, and you probably want it as electricity in the end state). That means where possible you want to keep electricity in it's original state for as long as possible, and if possible use it in it's original form.
So far so straightforward - build a gigantic HVDC connection across the Med (several in parallel, actually), and keep the lights on in Europe during the day. However, this is when the Dismal Science kicks in - daytime electricity prices are already dropping, and this would make them drop further. Worse, in Northern Europe at least there is a severe seasonal swing in energy demand. One of my favourite graphs shows exactly the problem:


Compare that to the PVGIS prediction for a random location in central Tunisia:


You can decarbonise electricity all you like, but that's only a small fraction of the problem - most of our energy comes from liquid and gaseous fuels, and what is worse these are predominantly used in winter. That means some form of time-shifting is inevitable, not even particularly overnight (with the rapid spread of electric cars and batteries I suspect this is a problem that some clever software will solve for us) but interseasonally. To do something about this means storable fuels, which realistically means hydrocarbons given all the infrastructure we have in place already, most probably methane.
As to where you create this e-Gas, my suspicion is that it will be embedded in the grid relatively close to where it is produced. Because the Med is relatively small (certainly compared to the Japan-Australia route) then HVDC transmission is economically viable, and you benefit at least some of the year from selling electricity directly and not being hit by the transmission losses. Therefore what I'd envisage is a series of e-Gas plants embedded in the grid across Europe, taking in electricity whenever the price is low and exporting methane to the gas grid. This is then used in winter, either in CCGT power stations or directly for heat - although I'd expect the most common use to be in conjunction with compressed/liquid air energy storage and a gas turbine*.
The real problem with turning the electricity into a fuel on site is that the value of the fuel is really low when fossil sources are allowed to compete. UK wholesale electricity prices are in the region of £50/MWh (from memory - haven't checked in ages), whereas wholesale gas prices are about £10/MWh. That means if you convert to gas on site in Tunisia, allowing for conversion losses you can sell your power at about £8 ($10)/MWh - around a third of the cost of producing it (the solar resource in North Africa is about the same as in the US, maybe a little worse - the southern US is one hell of a long way south!). What having the option of conversion does is ensure that the value of the electricity you produce will never drop below £8/MWh, because at that point the e-Gas plants can make money so will start up and buy it in essentially unlimited quantities.

So far as PV versus solar thermal goes, I suspect that the cost of the interconnector is actually a big part of this: the cost will scale pretty much linearly with capacity, so if you've got a way to time-shift generation during the day then you can run the interconnector much harder, shoving more energy through it in a 24 hour period. That means the value of storage is much higher than usual - rather than being the normal value, it's the normal value plus the infrastructure saving on the interconnector - which will be very large indeed for an undersea cable that long. Since solar thermal is more or less competitive with PV on a big scale but the storage is much cheaper (big tank versus batteries), then I suspect that this is why they're talking about thermal rather than photovoltaic generation.

Sorry if this is all a little disjointed - the younger minion is teething and my wife is just getting used to being back at work after 3 years off with the kids so I'm not sleeping much.


* Essentially the idea is that something like 60% of the power output of the turbine section on a gas turbine is used to drive the compressor. Since power demand is very peaky in winter (dropping a lot at night), it makes sense to drive this compressor electrically when demand is low (e.g. a windy night) and then use this compressed air to feed the burners when demand rises some hours later. That lets you do some nice things with the efficiency of the overall system if you're designing it from scratch to do this - and because peak electrical and heat demand is closely matched you should be able to use these in CHP/district heating systems quite easily.
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« Reply #10 on: August 12, 2017, 09:30:27 AM »

Thanks pdf, I think I understand that.

And I hadn't thought of the option of converting leccy to e-gas at this end, which could build in the necessary protection (storage) for any localised political instability in N. Africa.

If nothing else, it's nice to know there are more options available, belt and braces, going forward.
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dan_b
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« Reply #11 on: August 16, 2017, 11:26:31 AM »

The other thing that makes me feel a bit uneasy about this is I see no mention of whether Tunisia gets any domestic electricity generation benefit out of this project, or is it all sucked away to be consumed by the EU? Is it a two-way interconnector, so might Tunisia get low-carbon electricity back from the EU when it's cold dark and windy? 
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Mk1 ImmerSUN DHW diverter
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« Reply #12 on: August 16, 2017, 12:34:13 PM »

The other thing that makes me feel a bit uneasy about this is I see no mention of whether Tunisia gets any domestic electricity generation benefit out of this project, or is it all sucked away to be consumed by the EU? Is it a two-way interconnector, so might Tunisia get low-carbon electricity back from the EU when it's cold dark and windy?
The way they work is that virtually all of the cost is in the cable, not the conversion equipment at either end - and shifting that to do two-way conversion is very straightforward. It would be nutty to build a segregated system (using the Tunisian grid gets you free access to their infrastructure, and helps them get cheap electricity - given the conversion losses, it will always be cheapest to consume it closest to source), so we can essentially assume it works both ways. What it will do is link Tunisian and EU wholesale prices - what I don't know is how they compare at the moment, but I wouldn't be totally shocked if it turned out EU prices were cheaper.
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