Concentrated solar power looks on the surface to be an excellent source of grid power. It's sustainable, has no obvious waste products to deal with either during construction or operation, and with thermal storage it can generate power at night or on a cloudy day. It seems to address every problem with fossil fuel, nuclear, PV, or wind generation. Is there some disadvantage to this that I'm not seeing? Shouldn't we be building these plants as fast as possible?
There are no silver bullets when it comes to decarbonising the grid. That's good news: it means you can stop looking for one, and accept that every form of generation has its pros and cons.
Concentrated solar power [CSP] relies on direct sunlight. Not just ambient daylight, but lots and lots of direct sunlight all year round. Whereas ordinary photovoltaics [PV] will work pretty much anywhere in the world, from the tropics to the poles.
CSP doesn't work at all scales. Prototypes are still determining what's the most economical. PV works at pretty much any scale, from watts to gigawatts.
CSP is still in its infancy. There are maybe a couple of thousand grid-scale prototypes in the world, ~ 4-5 GW total capacity, and the ones with in-built storage for 24/7 operation are even rarer, because the economics stink. We've little idea on lifetime performance, optimal design, optimal maintenance regimes, and so on. Whereas PV is a commodity item manufactured in vast quantities - we're nearing a billion PV panels in the world now, with about 200GW capacity - fifty times as much capacity, and five or six orders of magnitude more repeatable units.
CSP is complex and time-consuming to design, install and commission. PV is very fast and very easy to design, install and commission.
Storage is, in most of the world, not a high-value commodity. So having in-built storage isn't - in and of itself - an inherently valuable thing.
We don't know what its lifetime cost per unit of electricity supplied will be. We've only a few young prototypes to go on. That kind of uncertainty is a disincentive to investors.
Everything we do as humans has consequences of some sort. Although not a huge downside (in my opinion), critics have often cited the plant's supposed adverse effects on wildlife:
It has been noted that insects can be attracted to the bright light caused by concentrated solar technology, and as a result birds that hunt them can be killed (burned) if the birds fly near the point where light is being focused onto. This can also affect raptors who hunt the birds. Federal wildlife officials have begun calling these 'eco-friendly' power towers "mega traps" for wildlife.
Unfortunately, about two hours into the test, engineers and biologists on site started noticing "streamers" - trails of smoke and steam caused by birds flying directly into the field of solar radiation. What moisture was on them instantly vaporized, and some instantly burst into flames - at least, until they began to frantically flap away. An estimated 130 birds were injured or killed during the test.
The veracity of these claims is in question however (from the Wikipedia article):
However, the story about the Ivanpah Solar Power Facility was exaggerated, numbering the deaths in many tens of thousands, spreading alarm about concentrated solar power (CSP) plants, which was not grounded in facts, but on one opponent's speculation. According to rigorous reporting, in over six months, actually only 133 singed birds were counted. And not only are the number of bird deaths far lower than the hundreds of millions to billions that die annually from collisions with windows, vehicles, and power lines., but, by focusing no more than 4 mirrors on any one place in the air during standby, at Crescent Dunes Solar Energy Project, in 3 months, the death rate dropped to zero fatalities.
In the UK, the sun does not shine every day. We also need the most power in winter when the sun shines the least.
Therefore every solar power station must be backed up by anther power station that can work when the sun is not shining. Concentrated solar power allows short term storage of the steam, so at least copes with 5 minutes of cloud cover, it does not help much with the “winter problem”.
However in an area when the peak power need is on hot sunny days due to AC solar power become a much better option.
We then need to ask if Concentrated Solar Power (CSP) is worth the effort compared to photovoltaics (PV). PV is a commodity and is getting cheaper every year, so all CSP can offer over PV is the short term storage of power.
If there was great investment in CSP in the correct areas of the world, with many designer being build and perfected, it may then prove to be very good. However I expect that we will never know, as the case is hard to make for the investment, given the PV is well understood and AC can be turned off for a few minutes if a cloud stops the PV working. (Storing “coldness” in a building is a method of effective energy storage.)
Concentrated solar power plants are best located in isolated areas that receive a lot of sunshine all year round, which basically means arid or semi-arid regions. Most of these regions don't have large populations so long power transmission lines will be needed.
To increase performance and efficiency, each CSP plant will need to be uniquely designed and constructed for the path and elevation of the sun at each location where a CSP plant will be established; particularly for the sun tracking system that will be needed to continuously focus the light from a moving sun onto one location. The path of the sun varies throughout the day and from day to day - low elevations in winter, high elevations in summer.
Power output will be optimal when the sun is at it's highest point in the sky and functioning well 2 to 3 hours either side of that. During early mornings and late afternoons the CSP will not receive much usable sunlight.
Some of these answers already touched on the environmental impact of CSP, I would like to add this article as a source. It reiterates on the points made by others who answered the OP's question and pointed out the issues with biodiversity (specifically bird species) being affected.
However, nobody pointed out the water use required for the cooling system which is also important. As time goes on we are going to need to be more careful with our water use, as we are already in need of a "Blue Revolution".
I think that CSP is an awesome supplement to PV systems and other types of alternative energy. It does make solar capable of achieving a more stable grid on industrial-scale installations. However we have to be careful of how we build it and how much we build it to minimize environmental costs.
The advantages outweigh the disadvantages, so the we need to consolidate the political will to make the necessary investments. The ideal locations in sunny arid areas would be next to the seas for powering desalination plants. The CSPs can be used together with PV for these applications.
By desalinating and electrolyzing sea water, we get hydrogen in addition to fresh water in addition to electric power. Through the electrolysis we can also obtain hydroxides to remove the carbon dioxide from the exhaust from hydrocarbon burning facilities. The hydroxides, primarily sodium hydroxide, would react with the carbon dioxide to form carbonates which are solid precipitates. The carbonate can be cashed in for carbon credits on the carbon sequestration market. We also get chlorine from the electrolysis of seawater which is also very useful product especially in the third world where it can be used to sterilize drinking water.
I would like to point out some "additional" information. I think that these CSP might also be used to create Hydrogen from electrolysis. Thus increasing the offer which might be important for development of the hydrogen fuel technology in cars. Because, only recently, I read that these cars provide much greater range than electric cars but the density of "hydrogen stations" is much to low for this technology to evolve. Thus, the CSP might have additional benefits for which they weren't even intended. It would have another positive effect, people don't have to think about how to store the "electric energy" because it was converted to usable "chemical energy" (although storing hydrogen isn't too easy by itself).