Terry Peterson
Solar's Next Sunrise
Special Issue
Volume A Number 1
Terry Peterson, Ph.D., is a principal at Solar Power Consulting, San Carlos, Calif. He is an independent solar power consultant with 35 years of experience in PV and solar thermal electric technologies, including research program management for over 17 years on the staff of the Electric Power Research Institute.
We are going to talk about solar power. The printed program mentions a 50-year promise and I thought I'd put that into a little bit of perspective. About 50 years ago, the commercial solar cell was invented at Bell Telephone Labs. Very few of you are old enough to remember the ads they were running in magazines those days, showing a family standing around the, presumably, family solar cell out in the backyard, generating power for who knows what. But it did highlight their innovativeness at that time.
That spawned a power supply for the United States' satellites in the 1960s and —€˜70s and then it moved into terrestrial applications of distributed solar power, mainly on rooftops. We're seeing that more and more these days as we look around; it's pretty much on schedule. Fifty years as a gestation for moving into a new energy infrastructure is very common. It's certainly not late.
That's distributed solar, and since that's seldom connected to the grid, if at all, it doesn't really play into the issues of transmission. It's very fitting that this session will focus mainly on central station solar power—€”a couple of different varieties. These gained momentum for the first time in the wake of the first oil embargo, so they aren't quite 50 years old in terms of implementation, but they are emerging and on the verge of being very significant commercially.
Solar power actually does work today, although you have no doubt heard that it's too expensive. It's approximately a hundred to four hundred percent above market without any subsidies, but it's coming down.
Solar technologies, because of this high cost, do require evolutionary technology advancement to reach a mainstream state as in the energy industry. I say evolutionary because I want to distinguish between ongoing evolutionary changes in the technology and breakthroughs, which can't be foreseen. We don't need breakthrough innovation in solar technologies to actually reach a commercial status. It's a matter of learning by doing and incremental technology advancement. We believe that this will happen for several varieties of current technology in the time frame of 2020, some of them a little sooner than that.
We'll also be talking about myths and realities, as well as challenges, to commercialization, and synergies with other power sources. And we'll get out our crystal balls to talk about 10 years from now.
But first I wanted to make sure everybody is on the same page about what we mean by Concentrating Solar Power, or CSP. Basically all CSP technologies have the same overall technology shape. It starts with an optical apparatus that concentrates sunlight and ends with wires that connect to the transmission line, not to your rooftop. In between, the details vary by technology, but in general there's a fluid that gets hot, and that fluid may be stored in some tanks, and the heat is then used to make steam. If there are tanks to store the heat, then the steam can be made many hours, or even days, after the heat has been collected.
At the end of this process, for most CSP technologies, there is a steam turbine and this is important because steam turbine technology has been around for a long time. It's well known, tried and tested. And perhaps even more to the point, it is well understood and liked by the utility community.
The hot fluid can be stored; that gives you a solar plant with dispatch ability. Dispatch ability is important for several reasons. It, obviously, decouples the generation moment from the heat collection moment, and that has the effect of actually lowering the cost of electricity, even though it increases the specific cost of the plant because it allows you to use the storage instead of buying a bigger turbine. And it allows you to use the turbine more often. That is, you have a higher capacity factor from the turbine and that means that the money that you invested in that turbine is more efficiently used.
Finally, the generation of kilowatt hours, when you want them rather than when they happen to occur because the sun is shining, means that your production has a higher value.
The other sort of central solar power doesn't have a steam turbine, but it does have the same shape. There's an optical apparatus that concentrates that sunlight, and there are also our transmission lines connected to the utility grid. The main difference here is that in between those two points is primarily solid-state electronics. And we've all learned about Moore's Law and how solid-state electronics has a tendency to become less and less expensive as we get smarter and smarter about making solid-state devices. The same is true for the components of this sort of CSP, which is also called Concentrated Photovoltaics, or CPV.
One of the myths that I have encountered in my 35 years in solar power is, "gosh, doesn't it take a lot of land to generate any significant amount of solar power?" And, indeed, it does take a fair amount of land, but fortunately this planet is blessed with quite a lot of land.
But if you look at a map of the seven Southwest states, you might say, —€˜Well, I see some cities there, Phoenix, Las Vegas. I see some places where there are lakes and certainly there are lands that would not be useful for any sort of use other than what they're already being used for. So, is that really available?" Well, a couple years ago, NREL and Sandia, working together, applied some screens to a resource map to answer that question of "What happens when you start taking out the areas that you can't actually use for solar generation?" So they applied a filter, first of all, of direct normal sunlight. It had to be over 6.75 kilowatt hours per square meter, per day. They didn't allow any inclusion of environmentally sensitive land, or land that was already in urban areas or had some other dedicated use, such as a military areas.
Furthermore, for this particular exercise, they limited it to a land slope of no more than one percent, since one of the CSP technologies requires fairly level land in order to avoid excessive cost from land preparation. And they also required that any contiguous area be at least ten square kilometers so that you don't have a patchwork of unmanageable small areas.
After all of these deductions and compensation for solar capacity factors there remains about four times the current U.S. annual energy generation capability. So the seven Southwestern states, have a larger potential capacity in the cream of the solar-resource area than the entire United States would require for generation to satisfy today's needs—€”a very significant resource indeed.
The prognosis of CSP and CPV is, in general, a very good fit to the historic utility business. In particular, CSP plants depend on steam turbines, which the utilities depend on every day. They're all central-station technologies, which fit into the way utilities conduct business. They generally are O&M (Operation and Maintenance) central value-changed. That is, a utility company can, by owning and operating a CSP plant, contribute to the value of the output of that plant over its 30 to 40-year lifetime, unlike distributed solar plants, where most of the added value has gone in by the time the last screw attaching modules to the roof has been turned.
There are also barriers to non-utility market entry for these technologies, which is perhaps an incentive for utilities to be interested in this business. They're very capital intensive, as are many other utility endeavors. There are large-scaling economies. You don't want to build tiny CSP plants. And, the new deployment drivers of RPSs (Renewable Portfolio Standard), a requirement that some portion of electric generation comes from renewable energy sources, in all of those Southwestern states and the extension of the 30 percent federal investment tax credit, plus allowing utilities to enjoy the credit, is now a reality.
I believe that despite the current financial meltdown, we are looking in the next few years at very significant deployments of several of these technologies. And within perhaps a dozen years, we'll be looking at a situation where building a CSP plant doesn't really require policy measures to make it attractive to investors.
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