Rocking the AC

When it comes up in casual conversation that I do not generally heat or cool my house, people either move to another seat or look at me with some mixture of admiration and disbelief. When non-Californians then find out that I live in San Diego, they might huff or spew, which often involves some embarrassing projectile escaping their mouth. But the locals are more consistently impressed—more so by my forsaking heat than AC (San Diego has very mild summers by U.S. standards). This summer, I turned on the AC for the first time since we bought the house three years ago. All in the name of science! I was blown away. Here is what I learned.

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Views: 6157

Battery Performance Deficit Disorder

Batteries fail—as certainly as death and taxes. Rechargeable batteries at least offer the possibility of repeating the cycle, so are in this sense more like recurrent taxes than death. But alas, the story cannot repeat indefinitely. One cheerful thought after the other, yes?  But wait, there’s more… Add to their inevitable demise an overall lackluster performance in battery storage technology, and we have ourselves the makings of a blog post on the failure of batteries to live up to their promises.

To set the stage, the specific energy of gasoline—measured in kWh per kg, for instance—is about 400 times higher than that of a lead-acid battery, and about 200 times better than the Lithium-ion battery in the Chevrolet Volt. We should not expect batteries to rival the energy density delivered by our beloved fossil fuels—ever.

A recent article in APS News reported on an emerging view that batteries are failing to live up to our dreams in the electric car realm:

Despite their many potential advantages, all-electric vehicles will not replace the standard American family car in the foreseeable future. This was the perhaps reluctant consensus at a recent symposium focused on battery research.

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Views: 11735

Solar Data Treasure Trove

I have not kept it secret that I’m a fan of solar power. Leaving storage hangups aside for now, the fact that the scale of available power is comfortably gigantic, that perfectly efficient technology exists, that it’s hard-over on the reality axis (vs. fantasy: it’s producing electricity on my roof right now), and that it works well almost everywhere—what’s not to like? Did you trip over that last part? Many do. In this post, we’ll look at just how much solar yield one may expect as a function of location within the U.S.

The ancient Mayans laboriously accumulated a substantial set of observational data on solar illumination across America well ahead of the present need. Okay, it wasn’t actually the ancient Mayans. It was the National Renewable Energy Lab (NREL), who embarked on a 30-year campaign beginning in 1961, covering 239 locations across the U.S. and associated territories. Imagine this. How many people were even cognizant of solar power in 1961? Yet the forward-thinking scientists at NREL appreciated the value of a solid baseline dataset way back then. This level of foresight seems akin to the Mayans constructing a calendar going all the way to 2012. That’s all I’m saying. It’s a gift from the past.

I have often consulted and enjoyed the product of this work over the years—called the NREL Redbook, or more formally, the Solar Radiation Data Manual for Flat Plate and Concentrating Collectors. But with a snazzy blog post as motivation, I have taken it up a notch and produced a variety of graphical representations of the dataset to explore what it can tell us. Let’s begin the guided tour.

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Views: 3139

My Modest Solar Setup

I have made repeated references in past posts to the modest off-grid photovoltaic (PV) system I built to cover a large share of our—again modest—electricity usage.  By popular demand, I’ll take you on a tour of the system: it’s history, its composition, and adaptation to my house.

In 2007, I acquired a single, second-hand solar panel—intent on doing something useful with it. Confronted with a variety of options, and eager to explore multiple paths, I purchased a second panel and proceeded to set up a dual system: two stand-alone off-grid PV systems mounted side by side. It was really cool. I was able to power my television console and living room lights off of the two systems, while experimenting with different components and learning to live (part of) my life on natural power. I wrote a comprehensive article about how to size and design such a system, which may be worth reading first. Since that initial success, I have incrementally expanded my system so that I now get more than half of my electrical power from eight panels sitting in the sun. This is their story.

I have enough to say about my solar setup (and PV systems in general) that I must break this topic into multiple posts. In this, the first, I will describe the components, functions, and evolution of the system. In a future post, I will present system performance data and an assessment of efficiency of the various components. Perhaps even later I can explore the impacts of panel orientation, tracking, horizon obstructions, and geographic location.

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Views: 4046

Do the Math Turns One: Place Your Orders

One year ago today, Do the Math was born with a post on the absurdity of continued growth—in this case illustrating a Galaxy-consuming civilization in a mere 2500 years. Within a month, the site was getting thousands of pageviews per day, as I cranked out a backlog of thoughts and analysis surrounding the energy challenges we face.

In the process, adhering to a weekly schedule forced me to perform many new calculations on topics I had not previously explored very deeply. So besides being a cathartic experience, I gained new understanding, finding the exercise of constructing the alternative energy matrix to be particularly clarifying. One of the major lessons for me has been that while the physical scale of any alternative energy resource is important—and sometimes a showstopper—more often it’s the practical limitations that form the biggest barriers.

Finding the time and (mental) energy to keep the blog rolling has been challenging, but it’s you folks who inspired me to keep trucking. Knowing that each post would be read by thousands, and knowing that I could look forward to some excellent and thought-provoking (although sometimes just provoking) comments made the enterprise worthwhile.

At this point, I have dropped the cadence to bi-weekly, and my list of future topic ideas is slowly being whittled down. Many comments in the past have requested that I write a post about issue or another. I invite you to submit requests (even if repeated) in the comment forum below. Note that I might not have the background, interest, or time to invest if serious analysis is required. But there is some chance I’ll take the bait—and the idea may already even be on my list! Please refer to the Guide to Posts for a refresher of what’s been covered already.

Also, I think it fitting on this first anniversary to extend a note of gratitude to Asher Miller of the Post Carbon Institute for inspiring me to start writing, and for putting me in touch with the fine folks at the Energy Bulletin. The EB editors: Bart Anderson, Kristin Sponsler, and Simone Osborn offered early guidance and good advice (plus instant readership) that was vital to getting Do the Math off the ground. So a hearty thanks to these folks! 1.5 million pageviews later, their contributions have clearly had an impact.

And thanks to you, the readers, for your role in making this a successful and rewarding endeavor.

Views: 1351

TED-Stravaganza

My wife calls it spying. I call it data. To-may-to, To-mah-to. It’s true that I know what she’s been up to (electrically) while I’m away. And it’s true that I can access this information anywhere in the world that has an internet connection. But domestic surveillance is not my aim (cameras and microphones would be far more informative in that regard). I just care about the energy angle.

In this post, I will present example results from monitoring and recording my home electricity use, demonstrating the marvelous secret world it reveals. My interest lies in putting numbers on my own behaviors, and in characterizing the appliances in my house. Some of this rubs off on my wife, and some of it rubs her the wrong way. But as I explained in an earlier post, I kept a note she once wrote that said: “Okay, TED’s pretty cool.”

Who is TED? TED is The Energy Detective. That same earlier post told the story of TED’s tortured journey to our home—a tale of excitement, rejection, and ultimate acceptance.

This post is not meant to convey anything deep and meaningful about the energy challenges we face, except for the fact that those challenges provided a background motivation for me to explore and monitor energy data in my home (it should be obvious by now that I’m a data-holic). Rather, I will simply showcase a number of data captures from TED so you can see for yourself the interesting hidden behaviors of appliances, and develop some intuition about how much of a toll various devices take.

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Ruthless Extrapolation

We humans owe much of our success to our ability to recognize patterns and extrapolate trends to anticipate a future state. My cats, on the other hand, will watch a tossed toy mouse travel toward them across the room—getting ever-bigger—all the way until it smacks them between the eyes (no, they’re not strapped down—I’m not that sort of scientist). But far beyond an ability to avoid projectiles, our ancestors were able to perceive and react to changes in local food and water supplies, herd movements, seasonal cues, etc. Yet this fine tool can be over-used, and I see a lot of what I call ruthless extrapolation. In almost every case, extrapolation works until it doesn’t.  When the fundamental rules of the game change, watch out!

As with many aspects of human behavior, some of the finest commentary on the matter is served up by The Simpsons. In one episode, Lisa Simpson is taken to the orthodontist to evaluate whether or not she needs braces. The “doctor” runs a simulation based on current growth rates, producing an alarming graphic of teeth gone wild.

Image obtained from saucesome.net

Marge shrieks and is ready to do whatever it takes to protect her daughter against this cruel fate. Extrapolation can, of course, be used to argue both for impending doom or future prosperity—sometimes based on the same data. I started this blog with an extrapolative foil to demonstrate the insanity of continued physical growth, in fact. A tangential follow-up illustrated the hopelessness of differentiating a steady-state energy future from an energy crash using current data (although a continued exponential rise is already a poor fit).

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Heat Pumps Work Miracles

[An updated treatment of some of this material appears in Chapter 6 of the Energy and Human Ambitions on a Finite Planet (free) textbook.]

Part of the argument that we cannot expect growth to continue indefinitely is that efficiency gains are capped. Many of our energy applications are within a factor of two of theoretical efficiency limits, so we can’t squeeze too much more out of this orange. After all, nothing can be more than 100% efficient, can it? Well, it turns out there is one domain in which we can gleefully break these bonds and achieve far better than 100% efficiency: heat pumps (includes refrigerators). Even though it sounds like magic, we still must operate within physical limits, naturally. In this post, I explain how this is possible, and develop the thermodynamic limit to heat engines and heat pumps. It’s a story of entropy.

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Views: 14235

Burning Desire for Efficiency

Ever wonder how efficient it is to heat water? Of course you have! Ever measured it? Whoa, mister, now you’ve gone too far!

I recently devised a laser-phototransistor gauge to monitor my natural gas meter dial—like ya do. As a side benefit, I acquired good data on how much energy goes into various domestic uses of natural gas. Using this, I was able to figure out how much energy it takes to heat water on the stove, cook something in the oven, or heat water for a shower. Together with the knowledge of the heat capacity of water, I can compute heating efficiency from my measurements. What could be more fun? I’ll share the results here, some of which surprised me.

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Views: 19273

Chris Martenson Podcast

I’ll cheat on my bi-weekly posting plan and slip in this podcast conversation between Chris Martenson and myself, covering many of the topics I have written about in the last year.

If you don’t have 45 minutes, and are a faster reader than I am, a transcript is also available—mercifully leaving out many utterances of “um” and “you know” (which is all I seem to hear when I listen to a recording of myself).  The original source and surrounding intro/write-up can be found on the Chris Martenson website.

Views: 1661