Who hasn’t enjoyed heat from the sun? Doing so represents a direct energetic transfer—via radiation—from the sun’s hot surface to your skin. One square meter can catch about 1000 W, which is comparable to the output of a portable space heater. A dark surface can capture the energy at nearly 100% efficiency, beating (heating?) the pants off of solar photovoltaic (PV) capture efficiency, for instance. We have already seen that solar PV qualifies as a super-abundant resource, requiring panels covering only about 0.5% of land to meet our entire energy demand (still huge, granted). So direct thermal energy from the sun, gathered more efficiently than what PV can do, is automatically in the abundant club. Let’s evaluate some of the practical issues surrounding solar thermal: either for home heating or for the production of electricity.
The Earth started its existence as a red-hot rock, and has been cooling ever since. It’s still quite toasty in the core, and will remain so for billions of years, yet. Cooling implies a flow of heat, and where heat flows, the possibility exists of capturing useful energy. Geysers and volcanoes are obvious manifestations of geothermal energy, but what role can it play toward satisfying our current global demand? Following the recent theme of Do the Math, we will put geothermal in one of three boxes labeled abundant, potent, or niche (puny). Have any guesses?
A recent thrust on Do the Math has been to sort our renewable energy options into “abundant,” “potent,” and “niche” boxes. This is a reflection of my own mathy introduction to the energy scene, the result of which convinced me that we face giant—and ultimately insurmountable—hurdles in our quest to continue a growth trajectory. It is not obvious that we will even manage to maintain today’s energy standards. We have many more sources/topics to cover before moving on to the “now what” phase of Do the Math. Meanwhile, requests for me to address the nuclear story are mounting. So before readers become mutinous, I should interrupt the renewable thread to present my nuclear reaction. It’s a rich topic, and in this post I will only give a tutorial introduction and my big-picture take. A single post can’t possibly address all the nuances, so my main goal here is to demystify what nuclear is all about, build a vocabulary, and set a foundation for further discussion in later posts.
I try to run a tight ship on comments, keeping discussion focused on the post topic, and in accordance with the discussion policy. But I sympathize with those who want to go off-road, since the overall topic is vast and has many threads—and I have not discussed some major components of the story yet. So as a holiday gift to Do the Math readers, I open here a discussion forum open to all topics involving growth, energy, fossil fuels, renewables, nuclear, demand and behaviors, societal hurdles, political facets, visions of the future, etc. This is your chance to express the big-picture points that may not fit within the narrow confines of ordinary on-topic discussions.
I will reject only comments that I deem to be uncivil, too far from Do the Math concerns, or so lengthy that I don’t have time to screen them (and long screeds also discourage readers and are therefore less likely to be read). If you’re tempted to write a long essay, I highly recommend starting a blog of your own (it’s not really that hard). Then you can summarize a thesis in a few sentences and point to the larger content elsewhere. So there you have it—now go nuts!
Having now sorted solar, wind, and tidal power into three “boxes,” let’s keep going and investigate another source of non-fossil energy and put it in a box. Today we’ll look at hydroelectricity. As one of the earliest renewable energy resources to be exploited, hydroelectricity is the low-hanging fruit of the renewable world. It’s steady, self-storing, highly efficient, cost-effective, low-carbon, low-tech, and offers a serious boon to water skiers. I’m sold! Let’s have more of that! How much might we expect to get from hydro, and how important will its role be compared to other renewable resources?
Last week, as soon as I put tidal power into a box labeled “waste of time,” I received some deserved howls of protest. I saw it coming, and had built in words to soften the “waste of time” label. But it was a poor choice from the start. A better set of labels is “abundant,” “potent,” and “niche.” The last could also be thought of as “boutique,” in that it is cute, perhaps decorative, may serve some function, but will never be a heavy lifter. The “potent” label—formerly “useful”— is meant to indicate a source that could supply a healthy fraction (say over a quarter) of our global demand if fully exploited. We will never fully exploit any resource, so the numbers at least need to support ¼-scale before we can believe that it may play a major role.
I should also point out that all along, my approach is to pretend that our goal is to keep up our current energy standards in a post-fossil-fuel world. In the process, we will see just how hard that will be to do. It is by no means impossible, but it’s much more difficult and compromised than most people realize. In the end, it is not clear that we will maintain our current global rate of energy usage: the future is unwritten. On the plus side, some of the approaches I cast into the “niche” box may become “potent” in a scaled-down world. Firewood was once abundant, then moved to potent, and is now a niche. But a reversal of fortunes could change all that.
Now is the time on Do the Math when we scan the energy landscape for viable alternatives to fossil fuels. In this post, we’ll look at tidal power, which is virtually inexhaustible on relevant timescales, is less intermittent than solar/wind (although still variable), and uses old-hat technology to make electricity. For this exercise, we mainly care about the scale at which the alternatives can contribute, leaving practical and economic considerations sitting in the cold for a bit (spoiler alert: most are hard and expensive). Last week, we looked at solar and wind, finding that solar can satisfy our current demand without batting an eyelash, and that wind can be a serious contributor, although apparently incapable of carrying the load on its own. Thus we put solar in the “abundant” box and wind in the “useful” box. There’s an empty box labeled “waste of time.” Any guesses where I’m going to put tidal power? Don’t get upset yet.
For me, the most delightful turn of events in the ultimate nerd-song “Particle Man” by They Might Be Giants, is that after introducing (in order of complexity) particle-man, triangle-man, universe-man, and person-man—and learning that triangle-man naturally beats particle-man in a match up—we pit person-man against triangle-man to discover that triangle wins—again. In this post, we’ll pit solar against wind and see who wins.
I will take my usual approach and estimate what I can—as opposed to researching the results of detailed studies. It’s part of the process of personal mastery of the big-picture issues, while also providing a sanity-check. In exploring useful reactions to the looming peak oil crisis (or pick your favorite rationale for weaning ourselves from fossil fuels), an appropriate strategy is to assess ballpark capacities of the various options. Some will prove to be orders-of-magnitude more prodigious than we need, others will be marginal, and many will show themselves to be woefully inadequate to match the required scale. So the goal is to perform this crude sorting process into abundant, useful, and waste of time.
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On Do the Math, three previous posts have focused on transportation efficiency of gasoline cars, electric cars, and on the practicalities of solar-powered cars. What about personal-powered transport—namely, walking and biking? After stuffing myself over Thanksgiving, I am curious to know how potent human fuel can be. How many miles per gallon do we get as our own engines of transportation?
Okay, the “miles” part is straightforward. And we can handle the “per.” But what’s up with the gallon? A gallon of what? Here we have all kinds of options, as humans are flex-fuel machines. But food energy is not much different from fossil fuel energy in terms of energy density.
If you like the sun, and you like cars, then I’m guessing you’d love to have a solar-powered car, right? This trick works well for chocolate and peanut butter, but not so well for garlic bread and strawberries. So how compatible are cars with solar energy? Do we relish the combination or spit it out? Let’s throw the two together, mix with math, and see what happens.
What Are Our Options?
Short of some solar-to-liquid-fuel breakthrough—which I dearly hope can be realized, and described near the end of a recent post—we’re talking electric cars here. This is great, since electric drive trains can be marvelously efficient (ballpark 85–90%), and immediately permit the clever scheme of regenerative braking.
If we adopt solar and wind as major components of our energy infrastructure as we are weaned from fossil fuels, we have to solve the energy storage problem in a big way. An earlier post demonstrated that we do not likely possess enough materials in the world to simply build giant lead-acid (or nickel-based or lithium-based) batteries to do the job. Comments frequently pointed to pumped hydro storage as a far more sensible answer. Indeed, pumped storage is currently the dominant—and nearly only—grid-scale storage solution out there. Here, we will take a peek at pumped hydro and evaluate what it can do for us.