As we contemplate the future of energy, and the combination of utility-level and distributed energy, and of different types – solar PV, solar thermal (heat your own hot water for showers), wind, etc., one question I have asked myself is how much energy can realistically be produced by the solar collectors on the roofs of our houses and office buildings in the U.S.?
It turns out the United States government has done some research on this! There’s a very interesting set of Department Of Energy reports, including one (PDF) on the market opportunities for grid-tied distributed solar PV. It figures out, state by state, how much roof surface is available, how attractive the incentives and infrastructure are (e.g., is there net metering?) and uses some simple algorithms to come up with an expected market penetration for solar PV on commercial and residential roofs. The resulting amount of electricity generated in this distributed fashion is amazingly high. Their best case scenario has installed MWs of rooftop solar PVs rising from about 2,000 in 2008 to almost 25,000 in 2015, more than a factor of ten increase over seven years.
The report uses conservative numbers for solar PV cost improvements – breakthoughs and innovations like the ones mentioned in Technology Review every week (like this one), will make the market penetration even faster (and higher) as they come to market.
I was pleased to see that our government has done this kind of research. Think what could be done if funding for renewable energy research and development was an order of magnitude higher!
Under the California Global Warming Solutions Act of 2006, the state must impose a limit on the amount of pollutants companies emit and expand renewable energy. These changes, along with others, would result in 100,000 new jobs, boost the state economy by $27 billion and increase personal income by $14 billion, the study said.
It’s traditional to believe that becoming green – reducing energy usage, switching to renewable energy, and curbing greenhouse gas emissions – is costly and a net drag on economies. But studies like this one, as well as many others (see the Rocky Mountain Institute website for many more examples), show again that the future is going to be both green and profitable.
“There are reasons to think that the ability to store electrical charge can be about double that of current commercially used materials. We are working to see if that prediction will be borne out in the laboratory,” said Rod Ruoff, a mechanical engineering professor and a physical chemist at the University of Texas at Austin.
Graphene is a special form of carbon in which the carbon atoms are linked into a sheet one atom thick. It’s highly conductive in the plane of the sheet. Because the sheet is only a few nanometers thick, the story has been presented as a “nanotech” breakthrough. However, as discussed in the April Technology Review report on a new, much cheaper and faster way to make graphene sheets, current means of producing graphene don’t use nanotechnology – just a highly miniaturized industrial process.
The biggest energy stories in August were about fuel cell-related breakthroughs and big solar projects. But the world of biofuels had some big news percolating as well. The beauty of biofuels, of course, is that they provide us with that extremely energy-dense liquid that we already know how to use (that is, gasoline, diesel, and ethanol), by sucking CO2 out of the atmosphere using solar energy.
In this post I highlight some of the biofuel-related items that caught my eye in the past few weeks, from algae that make diesel from atmospheric CO2 and sunlight, to harnessing bacteria and microbes as our refineries. This is just a small slice of the activity going on in biofuels, of course. Just as in solar PV, and batteries, and fuel cells, and wind, and alternative energy investing, there’s an ever-increasing flood of news every week. If I’m missing one of your favorites, please let me know in the comments!
Moore’s Law depended (and still depends) on a constant flow of breakthrough technologies, processes, scale, and designs. You can’t necessarily predict how Moore’s Law will continue to hold two years from now, or five years from now, but you can be confident that through some combination of technologies, processes, and designs, the price/performance of IT will continue to decline at an exponential rate.
The top five green energy stories of 2008 give an indication that the same types of forces are at play in the green energy world. Numbers 1, 2, and 3 each represent a potential 10x reduction in the cost of the most expensive part of a particular energy flow. For number 4, Gore used the bully pulpit of a Nobel Prize and Oscar (and, oh yeah, he was nearly president) in a most constructive way. And number 5 illustrates that green energy technologies are on a growth rate of doubling about every 18 months.
Did these stories excite you as much as they did me? Were there other green energy stories in August that you feel are more important?
The short answer is: while 100% is probably unrealistic, it’s not unreasonable to expect to be able to get pretty close to that number (say, in the 50-90% range) in that timeframe, and it is very likely that it makes a LOT of sense economically.
As you’ll notice Jerome has made somewhat different assumptions from mine, particular in regard to the total electricity demand. As I mentioned, I plan to drill down more into my analysis and take it from the “zero-order” to “first-order”. I’ll also revisit my assumptions to make sure we’re comparing apples to apples.
The UN Environment Programme (UNEP) reports that investments in renewable energy in 2007, at $148 billion, were 60 percent above 2006, with 2008 growth continuing. Achim Steiner, head of UNEP, said:
“The clean energy industry is maturing and its backers remain bullish. These findings should empower governments both North and South to reach a deep and meaningful new agreement by the crucial climate convention meeting in Copenhagen in late 2009. It is increasingly obvious to the public and investors alike that the transition to a low-carbon society is both a global imperative and an inevitability. This is attracting an enormous inflow of capital, talent and technology. But it is only inevitable if creative market mechanisms and public policy continue to evolve to liberate rather than frustrate this clean energy dawn. What is unfolding is nothing less than a fundamental transformation of the world’s energy infrastructure.”
Thanks to blow-hard winds, the United States has just become the world’s largest generator of wind energy.
Germany previously held this distinction, though since the United States has about 26 times more land than Germany, the milestone isn’t a huge surprise. Nonetheless, we weren’t expected to reach this point until late 2009. [Emphasis added – npd]
The key point is that we’re ahead of schedule on renewables, because the schedule was based on linear growth projections. The big question that remains is not whether the growth is exponential, but what’s the time period for doubling? Is it two years? Three years? One year? What do you think?
In his galvanizing speech a few weeks ago Academy Award and Nobel Prize-winner Al Gore exhorted the United States to “produce all electricity from “carbon-free sources” by 2018.” This is a pretty abstract goal, in those terms – Gore (appropriately) didn’t go into great detail about how this should be done or even what it means in specific practical steps. Depending on your point of view and background knowledge about energy, the goal may seem easy or incredibly difficult, or even impossible, especially without further analysis.
So I thought it would be interesting to run some numbers on the goal. The idea is not to define how it should be done, but to look at some very simple scenarios for how it could be done to get a sense of the scale involved. The calculation is based on the Topaz Solar Farm project, which California’s PG&E utility just contracted for – a 550 megawatt solar generating station.
My initial calculations makes some gigantic simplifying assumptions, so it’s not “correct” – but it should be the right order of magnitude. For details of the calculation, see the analysis below. The conclusion is as follows:
As a very rough estimate, we would need about 800 Topaz-sized plants, total cost about $1 trillion, to meet the U.S. electricity demand. And it would require about 8,000 square miles of sunny land.
1 gigawatt: Generating capacity for a “large” coal-fired generating plant
50 GW: California’s typical peak energy demand
24%: portion of PG&E’s currently contracted generating capacity that is renewable
For the purposes of this analysis, I’m making a few simplifying assumptions. These make the analysis “invalid” from a technical sense, but allow us to quickly see the big picture:
Electricity demand will stay constant: This may or may not happen – in California energy intensity (the energy used per person) is going down, and this summer absolute energy use went down. Amory Lovins of the Rocky Mountain Institute believes we can cut energy intensity by 50% via efficiency, which would definitely cut energy use. On the other hand, most scenarios dealing with energy use assume it will continue to grow.
Disregard base load issues: The sun don’t shine at night, but people still use electricity then. This is called “base load.” You often hear that “solar can’t provide base load,” which may or may not be true in the future, depending on storage technologies that might be developed. In any case, I’m not considering it in this analysis – I’m assuming “a megawatt is a megawatt.”
Disregard transmission issues: We’ll assume that if the energy is generated somewhere in the U.S., it can be used anywhere else it’s needed.
Disregard technology improvements – this calculation is based on the technology planned for the Topaz Solar Farm
We now have enough data to make the most simplistic conceivable analysis. How many Topaz Solar Farm equivalents (TSFs) would we need to supply total U.S. energy demand (given the assumptions above)?
Conclusion: In our simplified energy world, we’d need about 800 Topaz-sized plants, total cost about $1 trillion, to meet the U.S. electricity demand. And it would require about 8,000 square miles of sunny land.
Now, there are many ways that this analysis is “wrong” – since my assumptions simplify the world quite a bit. So it could easy be off by a factor of 50% or more. But, because the assumptions also tend to cancel each other out, it’s not off by a factor of five, say. For example, I’m not considering base load (which solar PV today can’t provide effectively), but on the other hand, solar PV is the most expensive energy source. We will probably need more than 800 plants, but a lot of them will be cheaper, per megawatt, than the Topaz Solar Farm.
In future posts I will expand this model to make it less simplistic and more realistic, and to take into account technology improvements, base load requirements, the ability of energy efficiency to change the demand line, and lots of other details that are just dropped on the floor for this analysis.
I’m very interested to hear your comments on this analysis. In particular, I hope for some constructive guidance on the next steps for making it more realistic. I want a simple model that’s easy for the layperson to understand, but which doesn’t over-simplify too much (as this model does). I’d consider this a “zero-order” approximation – the next one should be a “first-order” approximation.
The New York Times’ Dot Earth blog posted the text of Gore’s speech and allowed commenters to annotate it – interesting reading if you have a few hours to get through all the comments!
One of my pet peeves is news stories about energy that say something like “Flokistan just added 100 MWs in solar panels to its grid. This is enough to power 150 homes,” with no further numbers. I always want to know the context, like how many MWs does Flokistan use? How many homes are there in Flokistan? How does 100 MWs in solar panels compare in cost with putting in 100 MWs of coal-fired powerplants, and how long will it take to pay back?
The energy field is full of numbers – cars emit 19 tons of CO2 per year, solar panels cost $0.20/kWh, PG&E just contracted for 800 MWs of solar power in California. They are used freely, but seldom put into context. So I was very happy to discover an interesting online resource over the weekend: Richard Muller’s U.C. Berkeley class “Physics For Future Presidents.”
In one semester, my goal is to cover the physics that future world leaders need to know (and maybe present world leaders too.
Chapter one, Energy and Power (and the physics of explosions), of his textbook is online (at least temporarily) and it’s fascinating. Most interesting is the table near the beginning comparing the energy content per gram of various substances, including TNT, gasoline, hydrogen, various batteries, an asteroid traveling at 30 km/sec, and even chocolate chip cookies.
For example, a gram of gasoline has about 15 times as much energy content as a gram of TNT, and about half again as much energy content as a gram of ethanol. Hydrogen has almost three times the energy content of gasoline per gram, but even as a liquid, hydrogen is only about 1/10 as dense as gasoline, meaning that per volume, it has about 1/3 the energy content. Muller’s paper is full of useful rules of thumb, such as the following:
Remember this: Compared to gasoline, liquid hydrogen has
3 x more energy per gram (or per lb)
3 x less energy per gallon (or per liter)
He then goes on to discuss the relative merits of different forms of energy for powering cars, noting that gasoline is a particularly desirable fuel given its very high energy content and ease-of-use compared to, say hydrogen. Or batteries – which have 100x less energy density than gasoline. He also explains why having a big meteorite or asteroid hit Earth would be a bad thing.
If you’re interested in the numbers around energy, and how to compare them, I can definitely recommend a reading this chapter. The course is also available via podcast – see here for links, and covers not just energy, but terrorism, nukes, space, and global warming.
I’d be interested in hearing your comments about Muller’s information. If you have sources that you use for energy-related numbers, let me know about those too. I’m putting together a reference site for these sources, which I’ll link to on this blog as a static page when it’s ready.