The more I dig into desert solar power issues, the more I get asked certain kinds of questions. I figured it was time to try to answer a few of them here so that I could just point people at a page to save time.
I’ll add more supporting links over the next days, as well as potential additional Questions, but I wanted to get this out.
Aren’t you just a bunch of NIMBYs?
Many of us who oppose giant, remote industrial solar development are advocating, as an alternative, distributed generation from many sources including rooftop photovoltaic (PV) panels on businesses and homes. That pretty much makes us the exact opposite of NIMBYs. We want the stuff in our backyards.
Are you saying climate change isn’t a problem?
There are a couple of people working against desert solar who have been swayed by the overwhelming climate change denialism campaign. Most of the people I’ve met in the cause, though, are worried about climate change. In fact, as an environmental journalist since 1989 or so, I’ve been studying and getting the word out about climate change since before most people heard of it. Chances are I’m scareder of it than you are. It’s much of the reason I don’t have kids.
It’s just that destroying the planet’s habitats in order to save them makes little sense. Besides, the current mass extinction, set in motion primarily by loss of habitat, arguably dwarfs climate change as an issue (though they’re certainly interrelated). Why make one problem worse to try to lessen the other? Lastly, the thing about these big industrial desert projects is that they probably won’t do all that much to slow down the rate at which the climate changes.
Isn’t it all renewable energy?
No. Here’s a long but hopefully fascinating article that explains why not.
What do you mean when you say the big projects won’t help climate change much?
They may help, but they’re definitely being oversold and the issues oversimplified.
First off, solar plants are routinely described as having projected output many times higher than the likely actual figure. Take for example the Ivanpah Solar Energy Generating System, billed as a 392 megawatt (MW) generating plant. That figure is accurate, in a sense: the plant probably will generate 392 megawatts of power around noon on a cloudless day in mid-summer, when the sun is as close to directly overhead as possible. When the sunshine striking the plant is less energetic, for instance during winter, on cloudy days, during night, early morning and late afternoon hours, the plant’s output will be significantly less. During high winds, which happen frequently in the Ivanpah Valley, the mirrors will need to be secured, rendering the plant inoperative. The plant will likely need frequent maintenance, which reduces output during times when the plant’s offline. Utility experts refer to this kind of adjustment as a plant’s capacity factor. Coal and nuke plants commonly have capacity factors in the 60-90% range: they can run non-stop near peak output for weeks on end. Solar plants’ capacity factor run closer to about 25-30% at best.
Incidentally, for this very reason the figures you sometimes see in news articles referring to solar plants’ output with the phrase “enough to supply 400,000 homes” are almost always misleading if not completely incorrect. To determine how much generating capacity you need to power a certain number of homes the important unit isn’t megawatts, but megawatt-hours. A 100 MW solar plant with a capacity factor of 30% will produce only a third the megawatt-hours output by a 100 MW coal plant with a 90% capacity factor. To make it even more confusing, most homes don’t only use electricity when the sun shines. To say a large solar plant powers a certain number of homes is to use meaningless statistics. (Conversely, since rooftop PV systems are often used in conjunction with batteries to store energy, you can say each rooftop produces enough electricity to power a home.)
Secondly, building of remote solar and wind and other industrial “renewable” projects involves a large “greenhouse cost” that must then be amortized over the productive life of the project to get a true accounting of the project’s actual benefit to the climate. Construction involves intense energy use and greenhouse gas release, in everything from concrete to steel and other metals to the power needed for construction tools and equipment to transportation of materials and labor. With the distances encountered out in the desert, that transportation adds up. One significant addition to the greenhouse burden of these projects is sulfur hexafluoride (SF6), used widely in high-energy electrical engineering projects as an insulating fluid. SF6 is the most hazardous greenhouse gas the IPCC has studied. It’s 23,900 times as powerful a greenhouse gas as carbon dioxide: one pound of SF6 is the greenhouse equivalent of just under 12 tons of CO2. A typical modern circuit breaker used in power plants will hold a bit under 100 pounds of SF6. The bulk of SF6 releases happen during construction and repair of facilities.
Water is a huge factor. Though an increasing number of solar projects are “air cooled,” mirrors and industrial PV panels need to be cleaned regularly. That means water use. A huge amount of energy goes to moving water uphill in the arid West, and the specifics of some projects make the energy use even greater. The Calico project includes drilling for water in Cadiz, 40 miles away, and then shipping it to the site by rail. At Ivanpah, last I checked, they planned to use diesel trucks rumbling through the facility every so often to spray the water. If water use is curtailed, dust coats the mirrors and PV and cuts the output of the plant.
There’s the habitat displaced to consider. Some studies indicate that desert habitat may sequester 100 grams of CO2 per square meter per year, a figure about half that of a typical lush southern pine forest. Other reputable desert scientists think that figure is too high. Whatever the actual figure is, it’s clear that cryptobiotic crusts and other desert photosynthesizers do take carbon out of the atmosphere after which it could conceivably be dissolved by rain and stored as stable subsoil carbonates, removing it from the atmosphere. If you scrape the photosynthesizers away, you lose that ecological service.
Lastly, there’s the issue of transmission losses. When you transmit electricity over long distances you lose some of it: it takes energy to move the electricity. This is a function of the electrical resistance of the conductor. Unfortunately for the desert projects, this resistance increases dramatically when the temperature increases. Electrical engineer Bill Powers estimates that about 10% of the generating capacity of desert industrial energy facilities will be lost in transmission. (With distributed generation such as rooftop PV, transmission losses are minimized.)
Developers of the defeated Green Path North transmission line once admitted publicly that after taking into account the greenhouse burden of construction, maintenance, and habitat displacement, the project would never amortize out to be a benefit to the climate no matter how much carbon-free electricity it might carry over the years. Many proposed solar projects are likely saddled with the same inevitable burden.
All that may be true, but we still desperately need to replace coal-fired power plants, correct?
Yes. But because of its limited capacity factor, desert solar doesn’t replace coal. Desert solar provides what the utilities call “peaking power,” power that comes around when we need it most: when it’s hot and sunny and people are at work and using gigantic air conditioning units. Coal provides baseline power, which is the 24-7 stuff. What desert solar actually replaces is natural gas fired plants, which are generally used to provide peaking power because they’re relatively easy to start up and shut down according to demand. Rooftop PV can replace coal, or at least displace some of it, due to the possibility of battery storage.
You keep mentioning rooftop PV as a feasible alternative to industrial scale generating plants. Isn’t that a bit naive? The things are unreliable, inefficient, expensive, etc. Besides, the desert has more sun than I do in my town.
The difference in sun intensity in the desert and urban areas, at least those along the California coast (which is where most of the desert electricity would be consumed), is small enough that avoided transmission losses make up for it. In desert cities such as Las Vegas, Phoenix, and Palm Springs, of course, the insolation is the same as in the desert next door.
Costs of rooftop PV have come way down, and efficiency continues to climb — though what’s really important is the power output per dollar of investment, which drops as the price does. If rooftop PV wasn’t feasible or cost-effective, it’s unlikely that investor-owned utilities would make major investments in it. But some are.
In California, the two main obstacles to greater PV installation are legal, not technical. One is an artificial market structure that restricts the amount of power a homeowner or other small producer can sell to the grid operator. If every net kilowatt hour provided was bought at fair market rates, which admittedly sometimes might be zero, investment in PV would pay off a lot quicker. The other is the fact that rooftop solar generally doesn’t count toward the percentage of California’s electricity that state law requires come from renewables. Instead, they’re counted as “demand reduction.” If the Renewable Portfolio Standard regs were changed to include rooftop PV, utilities would have incentive to follow SCE’s lead in installing 20MW and larger projects on rooftops, over parking lots, on brownfields and incorporated into the design of new commercial buildings.
Even with those obstacles to PV and the absurd incentives for solar thermal or remote industrial PV, California – according to Bill Powers – is installing distributed solar PV generating capacity at a rate that rivals the installation of Big Renewables projects. 220 MW of distributed PV was installed in California in 2009, compared to 229 MW of the other stuff. There’s a very good reason for this: power from distributed PV is cheaper. According to an April 2010 draft report from California’s Renewable Energy Transmission Initiative (RETI), electricity from dry-cooled solar thermal is likely to cost about $30 per megawatt-hour. Distributed PV runs about $17-25 per megawatt hour. And it’s getting cheaper as the market for PV panels grows, production goes up, and unit costs come down.
The distributed PV doesn’t stop putting out juice all at once when a tiny cloud drifts past a city, so it’s more reliable than concentrating solar too.
This is all well and good, but all of us are going to have to make compromises to survive climate change. We may have to sacrifice some of your desert habitat to survive. The desert tortoise might have to take one for the team.
We all have to sacrifice? What sacrifices have you made? And did anyone notify the tortoise it was on a “team”?
Excellent. I’ll be forwarding this around.
Rooftop Solar is the best alternative at this time as it covers habitat already in the service of man. I’ve worked on several projects in Riverside and the ROI as well as the reliability is exceptional. Continued research as well expanded application of this system will yield great returns on the grid and long term benefits to the desert ecology systems.
So why do we not see more of it? Frankly it does not have the political sex appeal of a towering solar plant that constituents can see from the road. There are no grand openings, no ribbon cuttings with speeches, bands, and flags, so no TV, and no voter generation. Interestingly enough I have yet to meet a tortoise at one of these new plant dedications.
If the political folks really want to help they would enact landlord support legislation for rooftop installations. This would pave the way for private leasehold support that makes economic sense in the tenant lease. If a landlord can share incentives and returns with his tenant he can attract long term tenants who can make good use of this power. Industrial shops that use 480 3 phase are fairly efficient, but high energy consumers, who load the grid during the day when the sun is out. When you permit them to offset their grid draw with a solar contribution you will have many willing participants from a large private enterprise spectrum embracing and supporting roof top solar.
However, there will be no bands, no TV, just some happy CFO’s.
Cogent, clear, concise. Excellent to quote when commenting. Thanks
Great summary, just what we need to hear.
I’m with you on this one. Rooftop solar and deep conservation are the answers. My spouse and I live “off grid” and through drastic conservation (because we have to), we use 10 percent of the electricity that we used to use when we had the fat life on the grid.
Save the desert!
Good post, Chris.
Couple of points: Bill Powers told me that there is a way that large scale solar replaces coal. It’s true that a concentrating solar plant without storage is mainly peaking power. As you point out, gas-fired power plants can be started and stopped quickly, so they’re much better at working with CSP plants to smooth things out than a coal plant. In this way, in theory, a CSP/gas combination could be used to displace a coal plant. Bill had a technical name for this, but I can’t remember what it is. Of course, if we’re just adding the CSP/gas combination to the existing energy mix in order to power all of our new plasma TVs and iPads and cell phone chargers, then there’s no CO2 reduction, but actually an increase.
Also, some of the CSP plants are planning to use molten salt vat storage, making them more like baseline power. I think Solar Millenium is going to use this technology, and Abengoa is going to use it in their Gila Bend plant. It’s proven technology, while PV battery storage is currently prohibitively expensive. MIT is working on a fuel cell battery to work with PV that might be ready in ten years.
Don’t know why Ivanpah and others aren’t planning to use the salt vat storage, but it certainly puts them more in the peaking power category. The utilities will point out that they hit a different peak than PV: the 5 o’clock hour when everyone comes home and turns on their AC and other appliances. Maybe smart meters can encourage better-timed energy use among consumers. SDG&E just installed ours a couple of weeks ago, and soon I should be able to go on Google and see how much power we’re using at any given time. So I’ll be sitting here at my computer using power, trying to conserve power.