Comprehensive Guide to Concentrating Solar Thermal Power Technology

hi everyone and today it this is a presentation on a kind of

solar power that some people may have heard of that most people really haven't how many have heard of concentrating

solar thermal powers okay great it's a

best suited to desert areas so it's not likely will see too much around here although there have been some

experiments with a company here in Raleigh that I'll talk about a little later first I have about a 10-minute

film that was done by the Guardian and in England and it's a pretty good overview

of the area and then we'll go through a bunch of slides on various types of concentrating solar thermal and

the way that some of the plants are organized and some of the advantages disadvantages and cost factors and

things like that so how many of you knew that solar could be so cheap

ultimately actually most of the cost is in the equipment and paying back the loans

the the interest on the loans for setting up these solar plants is a very very large portion of what you pay for

electricity once they're paid off as you saw it's very inexpensive there's just the Sun is the fuel and all you have to

do is to operate and maintain the plant I talked to one of the engineers who maintained the

original concentrating solar thermal plant out in California we'll talk about in a bit and

he said that the reliability had gotten so high now that they couldn't even measure it because they just weren't

have any breakdowns at all on that planet so they're very well proven technology

how many of you have used a magnifying glass to burn something or okay so you have the concept right there you can use

either a lens or a mirror that simply focuses the Rays of the Sun and the

mirror could either be a parabolic circular shape or like a dis shape or it could be a long trough that

kind of thing in addition you can have many many mirrors that all reflect intersect the

the angle the Rays of the Sun and then reflect them on to a single point as the tower systems you saw there so there

there are three fundamental kinds of its two shows for here really there are three fundamental kinds there there are

the long trough systems and those are the pair the the parabolic troughs up here which

have been in use the longest those are the ones that are really proven their the linear for now and these are will

there will be some other pictures of these these instead of having a single big trough that gets moved to track the

Sun you have several straight lines of mirrors that have a focus they all focus on a single point and they're a little

cheaper than the troughs less efficient then you have the central receiver plants like you saw on this film and

they're actually the most efficient and they're the ones that are really undergoing the most development now the

the trough systems because they were the first the investors are more comfortable with those investors are very very

conservative yes you can get much higher temperatures the the amount of concentration that you

can get with a trough is less than what you can get with the tower you just keep adding mirrors and you can get extremely

extremely high temperatures and where the higher temperatures you get more efficiency

so the focus of development now is on the towers but the troughs still the investors seem to like to see something

in use for 10 years and commercial operation reliably for 10 years before they want

to put up their money which is kind of ironic you have to prove it out commercially before you can get the

money for it so it's kind of a chicken egg kind of thing but that's one of the functions of the government subsidies

and funding is to get these things started so then they can be proven commercially once they are if there are

the most efficient technology then the funding will come and the last kind is the the dish systems and these are a

little different from the others usually they usually don't use the steam turbine technology they usually use

the Stirling engine technology and there's also another thing which they can do

because you can get extremely high temperature is a few if you have a small enough focal point for dishes and we'll

see a big dish later so they also have possible use in actual direct chemical reactions direct chemical reactions to

hydrogen for example these are the areas that are most suitable for

concentrating solar thermal plants the darker orange are the most suitable areas as you see the United States is

one of the best places for concentrating solar thermal the reason that you need to use this in a desert

type area is that the collectors rely on all the rays coming in and parallel if you have haze

or clouds they disperse the Rays and they tend to come from all different places and so you don't get the optical

focus and you would you would need in addition these areas generally have a lot more hours of sunlight during the

year so the deserts are really the optimum places to put them and another thing about the deserts is they're

generally not that greatly populated and although their ecology is is often rather delicate

they don't tend to be built up either so the other places that are very good as you can see on here the Sahara

Australia has extremely good resources and then their other desert scattered around as well as you can see so with

most places in the world you could have a concentrating solar thermal plant within a couple thousand miles of most

of the major cities and this is a statement from one of the manufacturers of the

the transmission technology that can actually get the power long distances because like we wouldn't be near the

deserts here but we actually have a kind of transmission electric transmission technology called high-voltage DC that

could actually transmit the power thousands of miles with relatively low losses relatively great efficiency

I how many have heard this term super grids

it's relatively new and it doesn't have a really precise definition it's not really the same as smart grid

what it is this more like you would have say a gas pipeline or an oil pipeline it's a point-to-point a transmission

line that's meant to get very very large amounts of energy from one place to another place fairly far away

and the high-voltage direct current technology used for these can move an extreme amount of energy the five

billion watts per per transmission line and it can go several thousand km or

kilometers or two thousand miles or so the losses are about three percent per

per thousand km which comes to about five percent per thousand miles and the conversion losses on each end I believe

are either two or three percent and basically that means you have to generate some more power at the source

and this these this can transmit either concentrating solar or regular solar PV or when these kinds of transfer lies or

hydro they're used for hydropower now and like with solar the solar resources in

the desert southwest are so good that I read one study that found that if you transmitted the power from our desert

southwest from the CSP plants all the way to New York that it would actually be more you'd actually get more

efficiency than you would if you put up solar panels in New York so there are these considerations and the cost is not

really that great it comes out generally to be around one Center less per kilowatt hour

it's so these because these transmission lines move so much and last so long they're not really a very expensive

thing to put up the obstacles to them or more than not in my backyard kind of syndrome nobody wants a transmission

line near them one of the advantages of the high-voltage DC is it has less effect on the environment than the

alternating current which is a usual kind that you see yet it doesn't

one of the thing there's there's speculate their studies that are kind of a lot of studies are kind of inclusive

about the health effects of being your transmission lines but it is known that the AC transmission

lines the alternating current wants tend to attract a lot of particulates and they think that maybe one of the things

that's happening with the DC transmission lines they don't do that to anywhere near as great an extent so from

that standpoint they may be safer these are it is just a chart showing some projections on on how many

transmission lines or the I think this is in Europe just the growth of putting up these

lines so you get the electricity out this came from the desert tech project you heard the guy that was in Desert

tech in that film this has a couple interesting things on it first of all you can see this whole

grid that includes the power sources which are the concentrating solar you see these things

here those are the concentrating solar and then the wind power

these and then there are all these high voltage transmission lines the red ones that are transmitting it into Europe

also this down and and these plants up here can actually desalinate water as well which is great in these very dry

countries they can both reduce electricity and desalinate water at the same time with the same heat

the this is the amount of area in the desert that it would take to produce all the electricity that the world now uses

here the square here this is the European Union this is a Middle East and North Africa and

I'm sure what this one is but this this is kind of a startling thing

to see that that's all it would take to reduce all the world's electricity that much area in the desert I first found

out about concentrating solar listening to Radio Australia's

educational cultural network over the Internet and I heard an interview with a scientist who gave the figure that

75 square 75 miles on a side and the outback of Australia using these kinds of plants could produce as much energy

as Australia's using from all sources not just electricity but all the fossil fuel sources and transportation stuff as

well and that immediately Q mian boy if we have one technology that can do all this what if we just used all of them so

we've got the capability and this technology uses standard construction materials concrete steel

aluminum glass and the power plant is exactly the same as you'd find in a coal plant or other steam type plant

so here again are the types here's a parabolic trough you can see the the direct radiation comes in from the Sun

and is focused on that a tube it's actually tube that runs the whole length of these troughs that has a special high

temperature oil it's specifically made to be able to withstand those temperatures yes

yeah this is for now instead of having just a single curved mirror there are all these almost

flat mirrors that all rotate independently like hear what you have this this rotates the the troughs are

running north-south and as the Sun crosses over the sky the Sun goes over well actually worth deterrence and the

Sun moves the the trough actually tracks that the entire trough is on this motorized and gear type thing that all

these troughs are tracking the Sun like that that's a very they're very large they're expensive and the framework and

the drives to rotate them or are big and have to be very powerful with the for Nell you have all these smaller mirrors

and they independently track I take their they're much smaller to build less expensive to build and the drive

mechanisms to rotate them or less expensive to they basically the same thing that all these single mirrors then

are also just focusing on that tube the the Freneau is generally a little less expensive or a little less

efficient than the parabolic troughs and the parabolic troughs are less efficient the power the

[Music] dish systems can be really really efficient but they also

aren't really suited to this industrial scale like a utility scale power plant the dish systems typically

say with a Stirling engine will generate maybe 25 kilowatts of electricity per dish and they can be made larger but

it's very expensive to make a gigantic dish actually there is a project to decrease that expense which will see on

here any other questions on that yes [Music] oh

[Music] you mean on tubes are ya it I have some pictures of those

tubes actually that's going to be very soon yeah like this yeah right here these are

what the tubes actually look like they're they're a glass or actually I think it's actually some kind of a

quartz glass or something and they're evacuated and then you have inside you have this

metal tube that has a coating on it that's specifically made to absorb light as much light as possible and that heats

up the oil inside evidently these do not really degrade much over time maybe a few percent over 20 years or

something like that it's very low I've seen those figures and they're almost nothing but the other thing is that

these actually can be replaced they they have these joints in between because they're so long they have to have and

they rotate they have to have some way of joining them and some flexibility in them so they actually can be replaced

but yeah the efficiency of these does not seem to go down even though they are at

that very high temperature I think they said it was like five or six hundred degrees C with these which is pretty

high but it's these materials they're just made actually the people who do these kinds of things

are actually often rocket scientists the people putting up these tower plants and designing the collectors for those are

actually like rocca dine is one of the companies that's doing that it's the same kind of very very high temperature

physics and material science that they use for these things so this is that I answer that okay okay

great this is the first plant which is built in California it's actually a series of plants a solar electric

generation system I think it's what seg stands for and it's about 350 for megawatts capacity it's been operating

for over 20 years now this is older slide tell you a quick story if you have tendency to procrastinate

maybe my lesson is it's good for you I was updating some slides today around almost noon time and we had a

thunderstorm come through and there's some distant Thunder I thought nothing at all son was bang it was like you must

have been like within a few hundred yards of our house and my internet went out so

if my lesson is of any value to you I know it's hard to replicate these things and hard to set up control experiments

about them but it's probably good not to procrastinate so some of my slides are a little little

dated but they they're still pretty accurate in terms of the numbers so this is over 20 it's been operating for over

20 years commercially it initially went bankrupt after the subsidies ran out a long time ago but it was bought by

another company and it's been operated profitably since then and as I said this is a plant where the electricity was

three cents per kilowatt hour the cheapest electricity can buy pretty much and this is

Nevada solar one which is this was the first plant built in the US after that sex plant that you saw and

this just open just in 2007 it went into operation I think I don't think another one's been commissioned since then but

there are some that i think are about to be and they're a bunch of tower plants being built in the united states now to

the the funding environment and the subsidies and all it made a big difference the permitting has been very

difficult spin harder to permit these solar plants than to permit an area of the desert for running recreational

vehicles or for mining it's just been ridiculous they just haven't had the right rules in place and that's been a

real financial hardship for getting some of these new plants built that's getting worked out the government's trying to

work that out now in order to bring the cost of these plants down more have to be built they have to be more mass

produced another factor that's impinging on building the concentrating solar thermal plants as you've probably heard

the the cost of photovoltaic solar Zyzz just continually dropping and there are some advantages to CSP which will go

into soon but there is a competition between them in many areas this shows a little bit about we saw

this before on the top you can see there are these frames and that the parabolic trough mirrors go in those

frames and the designs is he says in this slide this is actually done by the guy who I heard on the radio australia

this is a picture of the one we saw one of these in the film they actually built two of them one was a

10 megawatt and the second one is a 20 megawatt ps2 and PS 20 very impressive looking thanks

this is the first yeah this is this a PS 10 there's a

first one that went out to operation you can see some of the figures there see the

good idea the temperature Sivas say there where the temperature is now I guess not saying the temperature

is I think they gave it on there is something like 600 see that they're using then get up to that 2000 see

they're using directly converting water into steam and the receiver on this one there are several ways to do it you can

convert water to steam you can use a heat transfer fluids such as oil that's usually not very well suited to the

concentrating or to the tower systems because they can get so hot they often use as a heat transfer fluid the same

molten salt mixture that they use to store heat for use when the Sun isn't shining and we'll go into that a little

bit too this is an interesting tower system East solar these are much smaller you can

probably see you don't have really point of reference but the mirrors are much smaller and they made these so they

could be in a shipping crate their manufacturing in China there in a sizing and put in a shipping crate they can

just bring them over they assemble very quickly and they just plop them down and the central computer

actually figures out exactly how to align them all and then focus them on the tower so they it doesn't require

much labor most of the other tower systems it's there's more precision and mounting the mirrors these

can also be made smaller these solar systems and the tower there instead of being like several hundred feet high and

a really big massive tower these are these can be just like wind turbines hours

and they have these plants have somewhat less output this is a prototype for 46 megawatt so that's

still quite a bit let's know quite a bit of electricity and this was just they did this to show off their central

computer system they spelled out e solar by aligning the mirrors so its bailout their company name

so this this is a diagram of a molten solar receiver and

the advantage of these molten salts and let's see I think we have well we'll get into that later what the mixture is it's

basically sodium nitrate and potassium nitrate it's a mixture of the two that has the lowest melting point called

eutectic and so with these tower plants because the very high temperature is it made more

sense to use the molten salts and they actually transfer the heat as well store it and

you can see well we'll have a better see yeah okay so there's a hot salt storage tank and a cold salt what that is a cold

salt they can never let the salt crystallized otherwise they're in big trouble because it's in all the pipes

and all the tanks it's solid and most plants have some emergency heat system should they not have any Sun for a while

or something happens to assaults moulton but operationally they always have the molten so the hot tank is extremely high

temperature the cold tank is still pretty hot it's still molten and then from the hot tank that's where

this molten salt goes through a heat exchanger and that actually generates a steam to run the plan run the turban

like you're driven so now we're onto dish systems most of them are Stirling engines

there you can do with steam but it'd be a very small steam engine it wouldn't be very efficient one advantage of these is

you could put these in a village or someplace remote and just run it say generate 25 kilowatts per per dish and

you don't need a big plant and as long as you've got somebody who can fix the Stirling engines which always have had

reliability problems but they're getting better you just keep the thing running now this is what's called a big dish

this is being built in australia australian national university

they wanted to build a parabolic system that was could be manufactured pretty cheaply

and was pretty big so they get very high temperatures and what they're experimenting with with this I believe

is its chemical storage using ammonia i think

is dissociating ammonia into hydrogen hydrogen and nitrogen I believe

because the temperatures are so high the dish systems can do that they showed when they're first

testing this thing they kept melting their receivers Monsieur paper various kinds of metals

this is a view you can get some perspective there's a worker up there it's from the front okay

and this is one additional additional kind of collector that actually can be used

in areas like ours it's called Winston you may want to look this up at some point it's a Winston solar collector it

uses non imaging optics so actually you can have the Rays coming in from fairly wide range they don't have to be really

direct and still get concentration and that means you still get higher temperatures and more efficiency out of

these collectors turns out a friend of mine who I recently talked to was a PhD student under the guy who invented these

things under Winston and he told me that they do work fine in our area there's a company in Raleigh that actually owns

the rights of the patent to this called solar genex and they've been experimenting with it so right here in

Raleigh a lot of the concentrating solar stuff has come out of the Triangle area interestingly enough the technology and

some of the experts are still here these may not be good for like generating electricity on commercial

basis but because of the higher temperatures they're good for say air conditioning systems called abs or

absorption or adsorption it's a a DSO rpts PT Iowan right yeah or AB a B SOR p tion

these are based on a mixture of certain liquid certain ammonia and other things or some kind of what's called a

desiccant and I'm not really familiar chemistry I've read through it and I've just forgotten exactly this process is

but basically they don't have compressors in them like normal air conditioners and heat pumps do and

they don't have to even have any moving parts it can all just be a gaseous and liquid cycle it goes through it you just

put in heat and you actually can extract heat on the other side and produce cooling that's very very interesting

possibilities for the southeast particularly a

storage is a big advantage of concentrating solar thermal over photovoltaic

the reason being that it's still less offensive to store heat than it is to store electricity

battery technology is getting better it's coming down and cost but it's still less expensive to store heat and

in the current plants most the storage is done using the the molten salts

another advantage of the CSP plants is you can back them up with any kind of heat source so you can back them up with

natural gas get back them up with hydrogen produced from renewable sources as well so the Sun isn't shining you

have a source of say hydrogen that you've produced from wind power over in the Midwest even or just from excess

electricity from your solar plant you could run the plant as long as you need to as long as you have that kind of fuel

because that will just again produce steam and run the same plan so you don't need an extra you don't

need a whole extra generating system there this shows the active one to the actual

plants the first plant that has in commercial that's commercially producing electricity using storage and

see I think it's several hours of storage on this one there's one that they have been

running 24 hours I know it just depends on how much storage you have and how big your field of mirrors is you just make

your field mirrors bigger if you had a field of mirrors that could produce a say 100 megawatts if you used it all

you have a 50 watt a 50-minute ever say you have a 30 megawatt generator or alternator RDS generator it's fordyce

alternating current usually then you store the heat from the rest of the solar array and you use that when

the Sun isn't shining if you have like eight hours of very eight or ten hours a very strong son and

you can just have a very large array store the heat and run the plant when the Sun isn't shining and there's the

molten salt mixture it's the sixty percent sodium nitrate and forty percent

potassium nitrate and that particular mixture has the lowest melting point of a mixture of those two when you put

those two together and those are the temperatures cold is 292 degrees C which is not very cold but that's what they

call it this is a diagram of a plant showing the various elements

the field of mirrors is out here that could be various different kinds of mirrors

that we've seen the main components here would be the suit is hard to see here

yeah this writing was a little funny on here too well here's a steam turbine over to the

right here and the heat there's a heat exchanger here

steam generator yeah generator here and there can be various other components that say preheat the steam or

you can have various stages where you heat the steam because the steam has to be an extremely high temperature before

it goes in the turban and some plants have energy have storage some plants do not some plants only run

when the sun is shining they have say natural gas back up that's what the sex plant in California does and you can

have an extra boiler here that would be what they would use so you could use either the Sun or the

gas boiler one thing you've done to make these plants even more efficient is to

use waste heat in this case this this plant is using waste heat from a gas turbine

to preheat the steam and then the solar field is using

to heat the steam even higher you can also have a hybrid where you have both concentrating solar and

photovoltaic and the same power plant that's being done more now that's being with that more that way you

get the advantage of both the less expense of the increasingly inexpensive photovoltaic

as well as there's lower maintenance on the photovoltaic and you also get the storage capacity of the

concentrating solar thermal plant another thing is that if the if a cloud goes over and you have a photovoltaic

array your energy drops like that your output logic outfit just drops like a stone the rest of the grid doesn't have

the capability rack that fast right now to any great amounts of energy going into it that can fluctuate that rapidly

with a concentrating solar thermal plant even if you don't have storage there's enough storage just in that oil it goes

through the hole those tubes and all that it's drop-off is much slower it's over a period of ten or twenty minutes

even if you get a cloud over the Sun and and that gives plenty of time to bring up the auxiliary like gas fired power

plants that that fill in when that happens that's and so these concentrating solar thrown plants look

to the grid just like a coal plant or nuclear plant which the whole electrical industry is very used to handling they

know how to analyse things so from that standpoint they like them these are some costs you can see the

capital cost of solar term list photovoltaic a little this is a few years ago I think this is 2009 the costs

have dropped considerably and capital cost is so a photovoltaic are now lower the

one of the more telling numbers is the operation and maintenance you can see that with solar thermal it is higher you

still have that all those moving parts out there and you have the steam power plant steam generator and that does

require more maintenance with the solar photovoltaic you're converting directly into electricity even if you have

trackers out there you still have less maintenance with both of them you have to clean them off you have to wash them

off with water or I guess they could have some kind of error type thing that could clean them off as well but you do

have to clean the mirror ray and with photovoltaic if you have it out in the desert you're going to get dust on there

too so you have to clean them off so there's some some maintenance involved in any case

this what I was talking about the desalination you can have the electric power plant

receiving the steam and running the turban but you'll still have a lot of heat left over when you've extracted the

power out of that steam you'll still hold a lot of heat and that's adequate to desalinate water and also to run air

conditioning the adsorption absorption air conditioning this is much a much more efficient thing to do

generally the concentrating solar plants are not near to populated areas so it doesn't really make a lot of sense to

use it for eating buildings because you have to make that heat go so far that would make sense if you were if you had

a coal plant or a gas-fired plant to reuse the heat and that that would make it much more efficient

these are there are a number of different methods and I haven't really studied these you probably all know

about distillation that's one way can be done but that's really not the most efficient way to desalinate water

anymore there's urbis osmosis and and other other means of doing it now so I won't go into these

because I'm not really all that familiar with them but just to give you an idea there are different different ways of

doing it and the ones that require lower energy that you can do with the temperature that you have are the ones

you'd want to use for efficiencies thing just to touch very briefly this is not solar thermal there's a whole

set of there's a whole area of photovoltaics concentrating photovoltaic scald cpb

where you you focus on a line of cells that are specifically made to operate at higher temperatures and this is actually

a company in the Triangle area and I don't know where this test one is but it's Piedmont electric and so they're

actually using concentrating collectors in our area so they can work they're just not as efficient as I would

be in the desert but this is a very very promising area because the area of cells that you have to use is

much much smaller and you can have the cells that absorb those more expensive cells absorb more of the spectrum and

much more efficient and the materials that reflect light are relatively much less expensive than the solar cells it's

just they can just be some kind of metal with a good reflective surface or some metallized kind of surface in this

company particularly is aiming at extremely inexpensive reflectors and tracking mechanisms and

apparently it's successful I haven't heard the exact numbers on it so that's that's basically it

[Applause] are there any your thought