Comments on: Solar energy 'power towers' to light up California

Utility Southern California Edison signs a huge deal with solar thermal company BrightSource Energy to make over one gigawatt of electricity from the sun's heat.

[Rick Cavaretti]

845,000 homes is like what, average 3 people to household? Making it 2.5 million people. Build 4 such plants and there's 1/3 of the population of California. Done.

[SteveW928]

Yep... then build like 20 more and suddenly we don't have to do all kinds of silly (and probably harmful) things to try and save every bit of energy. Use hydrogen and possibly electric (if battery tech can advance enough to eliminate major environmental impact) sport cars..... heat your swimming pool... etc. all with little guilt. It doesn't seem like there is much of a good technical reason stopping this. The best part is that for the average person, they would have to make very little change other than maybe buying a new vehicle at some point... the rest would largely work just as it does now.

[errantboy]

Can someone explain to me how using concentrated sunlight to heat water to produce steam to spin turbines to generate electricity is more efficient than using photovoltaics to produce electricity directly from sunlight? I can understand that the startup costs might be lower for the solar steam generators but wouldn't photovoltaics be the better long term choice?

[SteveW928]

Well, I'm no expert on this... but from my understanding, photo-voltaics have a few problems.
1) They are VERY $$$ for the amount of energy they produce.... hopefully this will change some day.
2) They take quite a bit of energy to actually produce and create electronic waste and production chemicals,etc. (my guess is that some of these concentrated solar systems have less environmental impact in many ways).
3) They produce so little energy per surface area.

I like solar cells for many things... and I think for small applications, they probably are great. But, I think the idea of plants like this is to generate power on the utility scale and then just distribute it through the grid like we are no used to. I hope to see the day when we can produce so much energy through plants like this or linear fresnel systems that we can stop worrying about energy usage, and just focus on pollution. There really is no good reason we should have to worry about how much energy is being used when it would be so easy to generate as much as we need in relatively clean ways.

[marcusmaedl]

Hello errantboy,
CSP (concentrated solar power - what they are talking about here) has a lower initial capital outlay. They have system efficiencies of 14% to 20% - if you look at the AC side of things and if you allow for water cooling. This brings us to the achilles heel of CSP - the use of water. Not many locations where you have a lot of direct irradiation and an abundance of water. If you recycle cooling water you will likely pay for it with efficiency losses.

The PV solutions are currently still more expensive up front but show enormous cost reduction potential with volume (and volume is coming online big time). You are right, eventually 70% of the world's energy will be generated by PV - in a 100 years time frame.

Meanwhile, certain locations will lend themselves to utilize PV over CSP and CSP will play in the very large utility scale market due to lower cost per kWh on a Gigawatt scale.

Today PV system efficiencies range from 4% for certain thin films to 25% for CPV (concentrated PV based on multi junction cells with 40% conversion efficiency). My guess, in 10 years PV solutions will reach 35% system efficeincies and grid parity with fossil fuel based energy.

Hang in there, it's all good...

[willdryden]

PV is lucky to last 3 years in the desert. One good sand storm will score the protective glass and lower the output below 60% of their original spec. Mirrors, although they do score, can be replaced much cheaper. The other advantage is that they can outfit the tower with natural gas burners for nighttime use since they use standard steam turbines, This provides base load power instead of the intermittant power from PV panels.

[bikejuggy]

errantboy, 2 books you should look at on this subject that will explain everything...
1) Physics For Presidents (summary of the energy section: http://muller.lbl.gov/teaching/Physics10/PffP.html)
2) The Manhattan Project 2009

[SteveW928]

@ willdryden - you hit on a big point when you said intermittent with PV. That is also a problem with the type of CSP this article is talking about... though as you mentioned, there are work-arounds. Utility grade power needs to be 24x7 to really work well.

Another solution I've heard a lot about is the linear fresnel systems that heat some kind of liquid in tubes, then some kind of silicon based substance to like 800 degrees. Then this liquid can run turbines 24x7.... though I'm guessing the water usage is still going to be a problem (well, it's not exactly 'using' water.... it is more a source and supply problem.... there has been roughly the same amount of water on the planet for a long, long time.)

[contentcreator--2008]

Photovoltiacs are happy to get in the 20% efficiency range, not very impressive.
Solar towers concentrate all the energy very efficiently in one spot producing a very high temperature differential. That corresponds to a high maximum efficiency---that's one of the laws of thermodynamics. If you have all the energy in one hot spot, you can engineer the heck out of that one thing.

[mlamonica]

An important point is that concentrating solar makes most sense where there is the right irradiance, like they have in the southwest U.S.

[basraw]

Wouldn't it be easier to build a couple big magnifying glasses and route that to the steam thingy?

[marcusmaedl]

mirrors have a >95% optical efficiency. Hard to reach with optics....

[Michichael]

What Marcus said.

That and PV or Optics all have the shared flaw of the moment they're damaged, they lose their effectiveness and are expensive to replace - making multiple points of failure. For a mirror field and tower? Tower's the only expensive part, comparatively. Mirrors aren't expensive.

[theBike1945]

Preposterous claims here - 1300 megawatts is "rated capacity," not actual or typical output, which would likely run around 400 to 500 megawatts for solar thermal plants, or enough to power roughly 400,000 homes.or less. This is not much power - a single nuclear plant can easily produce reliable
power (which this is not) and produce two to three or four times as much - and last 60 years, not the 20 years this solar plant will be in operation , and can be built in 3 years, not 11. It becomes ever more obvious why California is a financial disaster area tha the highly educated and companies are avoiding like the plague. California the brainless and now the dead broke.

[SteveW928]

@ theBike1945 - well... and then you have the nuclear waste that lasts and lasts... that we don't really have a good solution for. Most of the issues you pointed out can be easily corrected... I'm not sure where you got the 11 years from... I'm sure you could build one of these plants considerably faster than a nuke plant if you wanted to. It is far safer than a nuke plant. You could build a whole bunch of these.... no reason there needs to be a 1-1 comparison of output with a nuke plant. I'm not necessarily against some nuke plants as a short-term solution... but why not do these instead since the technology is here?

[solar_thermal]

Until very recently I operated one of the very large solar plants in the Mojave. Yes they are talking about rated capacity which is very different than actual output. The actual output will probably be closer to 25% of that. The good thing is that they will be nearer the rated capacity during the peak energy use hours in California. I will disagree with how long a solar-thermal plant can operate. Really it is just a normal steam plant and can basically operate indefinitely with proper maintenance. Some of the solar plants in the Mojave are already over 20 years old and work fine. Nuke plant also require extensive and very costly maintenance periodically too. That being said I am a very big fan of Nukes.

OK I do not know anyone, in the solar industry, who feels we are anywhere near running the world with it. I feel that PV will eventually be important but I am not a fan of building large ?solar plants? with it. For now it just requires too much land and because we have no way to store the electricity on a large scale, they are just not controllable. With a PV plant one cloud can cause major load swings on the grid. With a solar thermal plant single clouds will cause the plant slowly lose power in a much more controllable manner. Solar thermal also tends to lend itself to other technologies that may lead to cost effective energy storage. Natural gas can be added to solar thermal systems so they can ride out clouds or be used at night. The present solar thermal plants use this system.