by Marcin Wichary on Flickr

Many people have heard some version of “Moore’s Law” – that the number of transistors on a chip approximately doubles every two years. This study reveals a related trend in energy consumption per computation.

There are some details to consider, of course. For starters, it helps to know that everything a computer does is broken down into individual arithmetic operations. When talking about how buff a supercomputer is, for example, we talk about the number of floating point operations it can do per second (today they run upwards of one million billion operations – what we call Peta-flops). This study doesn’t take modern supercomputers into account, but the researchers note that today’s supercomputers are made up of clusters of individual processors, some of which they did measure.

Now, your computer isn’t always working to it’s full potential. When it does, it typically doesn’t respond well to user interaction (like when you start all of your apps in the morning). So to perform the measurements, the researchers had to keep the processors busy for the period during which they measured energy consumption. They also disabled the displays on the laptops that they measured to put them on equal footing with the other computers.

In addition to these modern measurements, the researchers incorporated historical power consumption data from some of the original vacuum tube supercomputers and other earlier computer models that aren’t available today. The methods used in these prior studies varied, but the graph resulting from this aggregate study shows a remarkably clear trend:

J. Koomey et al., "Assessing Trends in the Electrical Efficiency of Computation over Time", Submitted to IEEE Annals of the History of Computing: August 5, 2009, http://www.greenercomputing.com, Dec 12, 2009

The vertical axis here is logarithmic and labeled in scientific notation. For those unfamiliar, the number after the + sign corresponds to the power of ten, so 1.E+01 means 10, 1.E+03 means 1000, and so on. Each horizontal line represents a ten-fold increase over the line below.

Note that the early vacuum tube computers operated at less than a Mega-flop per kilowatt hour. These machines could perform ten thousand calculations using the same amount of energy as a 100 Watt lightbulb left on for an hour. You can see a jump in efficiency as transistors and integrated circuits replaced vacuum tubes around 1960. And as we have packed more and more computational power into the same amount of space on a microchip, the distance that electrons have had to travel without doing useful computation has steadily been reduced, roughly doubling the number of calculations that could be done with the same amount of energy every 18 months (very similar to the trend in speed that we’re familiar with). So, although your laptop can’t do a Peta-flop in a second, it can do it using only about 1KWh of electricity – a billion times more efficiently than those vacuum tube supercomputers (although we should note that manufacturing cost is not factored in). This is the power of exponential growth.

And according to a recent interview with Lorie Wigle of Intel, while this trend continues into the future, manufacturers will be looking at additional ways to improve the efficiency of information technology, from power supply design to power management via the operating system. Hopefully this will be combined with higher rates of e-Waste recycling, leading to more sustainable computing practices.

Currently, biking to work is more difficult. However, last year I heard about Bike to Work Day, which occurs during Bike to Work Week in the middle of May (you guessed it, Bike to Work Month). I knew that I was not quite in shape for it then, but made it a goal to take on the challenge of biking to work this year during Bike to Work Week.

Don't worry mom, I've already stopped

As spring came around this year, I was back in the morning workout groove. I had lost a few pounds, but more importantly, I was feeling more fit – feeling up to the challenge. The time had come to do some research. I looked at bike routes in the area, and did a weekend trial run on the shortest commute using Indy Parks bike routes that I could come up with.

Unfortunately, I have a hybrid-style bike (not a road bike), which limits my speed, and I’m not comfortable riding on the street. The quality of the shoulder varied from good to poor to non-existent. Fortunately, I have a hybrid, but this was not really the experience I was hoping for. So, I reworked my route to use higher quality, well-used paths, extending the length of the commute to about nine and a half miles but improving my safety.

Gooselings out for a morning swim

During Bike to Work Week, I decided to ride on the day with the best weather forecast. It was a little cold when I started, but the skies were blue and it wasn’t long before I was enjoying the cool breeze. As I came to the canal that eventually runs by the museum, I rode past ducks sleeping along the water in the morning sun. Further along I rode past geese, and I can only assume that both parties were wary of any sudden movements. The toughest section is the climb up to the museum from the bridge… I’m glad I have plenty of gears.

While the morning commute has a serene quality to it, I enjoy the ride back even more. My drive back home can be fraught with decisions about which route will have less traffic, and I see examples of poor driving behavior just about every time. Although there’s just as much need to pay attention whether driving or biking, I feel that it’s easier to attain a peaceful awareness when cruising on two wheels.

Starting out for home

This is why I’ve done the commute four times already. The ride is still pretty exhausting, so I can’t do it every day, but I think once or twice a week is a good goal. It’s a great way to keep in shape, reduce stress, and minute though the effect may be, it reduces carbon dioxide emissions. I couldn’t help working the equations, so let’s take a look at the numbers.

My biking offsets 9.0 miles of driving. I’ve been getting about 48mpg lately, so that’s 0.38 gallons saved per commute. At $2.50 per gallon that saves me 95 cents. According to the EPA, burning 0.38 gallons of gas emits 7.4lbs of carbon dioxide. So assuming that any additional respiratory exhalation of CO2 is negligible (biochemists, is this true?), I’m eliminating an amount of carbon dioxide emissions that would weigh almost as much as a gallon of milk with each commute.

That seems significant, on a personal level, considering that annual per-capita emissions are estimated to be on the order of 16 tons (working out to about 88lbs per day). Of course, eliminating hundreds of millions of metric tons of emissions with a new emissions standard is much more significant on a national level. Someone getting the average 35mpg in 2016 would still save 8.6 cents (at $2.50 per gallon) and 0.55lbs of carbon dioxide per mile if they biked instead. Someone getting around 20mpg could save 13 cents and 0.97lbs of CO2 per mile today. Feel free to check my math… that’s what peer review is all about.

Better health, less stress, less traffic, less carbon… seems like a win-win to me. Are there any other bikers out there? What are your thoughts?

This device monitors voltage, power, and cost

In today’s post I would like to share some investigations that I have done with a couple of cool energy efficiency tools. Perhaps you’ve heard of vampire energy. I’ve suspected that some of my home appliances are vampires, and a few weeks ago I decided to start doing some investigation of my own by purchasing a consumer-grade energy meter to measure the amount of energy that various electronics around my house consume. I haven’t done much analysis yet, but I have found that during normal use over a month, my entertainment center uses 75.04kWh and costs me $10.20 in electricity. This amounts to $122.40 over the course of a year. When everything is in standby, these undead electronics suck down 36kWh in a month (I need to run this test with the DVR on another outlet). Leaving the system in standby for a year would still cost me about $60.

The software displays your savings to-date

Last week, there was a new device laying on one of our office tables that I couldn’t resist asking about. It’s called an ecobutton™, and of course I couldn’t wait to take it home for some analysis over the weekend (yes, I’m a real party animal). The Web site claims that the the button will put your computer into a deep sleep, achieving power savings beyond what your normal standby mode can offer. I don’t have a desktop machine at home, but I did test it on my laptop from the Museum. The software is simple to set up. After entering a few numbers that it uses to calculate your savings, it’s ready to go. It’s also simple to use. When you walk off to a meeting, simply pressing the button puts your machine into power saving mode. The instructions say that the computer will awaken when the button is pressed again, but on my laptop I had to press the power button.

For my experiment, I made sure to disable all of the power management settings and only enable the mode for each measurement. Ideally I would run each measurement for an equal period of time, but this was a weekend project among other errands that had to get done (in as few trips as possible, of course). My hypotheses going in were that screensaver mode wouldn’t be much better than normal mode compared to “no monitor” mode, and that normal and deep standby would both be very close to zero consumption on a laptop.

So, let’s take a look at the results (Average Wattage = Consumption * 1000 / (Time / 60)):

Indeed, running in screensaver mode saved 5W on average, while no-monitor mode saved 16W. I ran the system in normal standby overnight, because when I checked it after about two hours it read 0kWh with an instantaneous wattage of 0W that seemed to occasionally spike to 2W and I wanted to see if anything would accumulate over a longer time period. Not surprisingly, deep standby also ran at 0W.

The lesson that we learn here is that deep standby is just as good as normal standby for our laptops, so the main benefit is that standby mode is easier to explicitly trigger with the button (rather than having your machine wait until Windows power management kicks in, or selecting it from the menus). As a side note, you can also use the pulsating glow of the button to practice stress-relieving breathing exercises (maybe there’s a Mac vs. PC commercial idea in there). I want to run this analysis on a desktop machine as well, to see if the button can save more energy in standby as the company claims.

Now, actual savings ultimately depends on the power management settings configured on our computers and requires a few assumptions and more calculations to estimate. It seems to me that the ecobutton™ could be a fun way to help us save a little extra energy (hopefully enough to offset the cost of manufacturing and shipping the buttons), and keep conservation in mind. As one of the Eco crew team members at the IMA, I’m on the lookout for technologies like these that can help us in being good stewards of the environment (hopefully while saving a little money and having a little fun as well). Stay tuned for more discoveries!