Martian dunes, captured by NASA's Mars Reconnaissance OrbiterWhat started out to be a workaday chore—replacing a broken motor in an exhibit—panned out to be a voyage of discovery to the shifting sands of another world. This is an occupational hazard when working at a place like Chabot Space & Science Center….

The motor in question powers a fan in an exhibit built to demonstrate the physical processes of duning—the fluid transport and deposition of solid particulates into collections and patterns. The fan blows up a constant micro-gale within the exhibit enclosure, and visitors get to play Mother Nature by turning a handle and redirecting the wind. Meanwhile, a mass of tiny white glass beads is constantly whipped up into a fair recreation of a sand storm on planet Arakis….

After the chore of installing the new motor, I rewarded myself by enjoying the exhibit a bit. I piled up all of the sand on one side of the tank to see how the fan would redistribute it; I sent the wind from different directions, watching how the freshly blown grains were scattered across the pristine black undersurface; I placed all of the pyrite rocks, which serve as wind obstacles, in one pile. It was a lot of fun.

One thing I noticed that I hadn't paid much attention to in the past was how the dune actually moved, or migrated. Maybe I hadn't watched long enough before, or maybe it was easier to witness because I had stacked the deck by mounding the sand all in one corner, but it was fascinating to see the process.

On the windward side of the giant dune, the scouring wind picked up the sand and carried it racing to the top—slowly peeling away the front face of the dune. As soon as the sand-laden wind reached the crest and took a sudden turn downward, it was slowed a bit, becoming less able to support the sand grains, which then fell out onto the leeward side of the dune in a sandy-wind version of precipitation. The buildup of sand on the lee side eventually formed small avalanches that slid down the face in little dry floods.

In this fashion, the dune moved along, slowly being erased on its windward side and formed on the lee.

Almost coincidentally, a few days later I read a report from NASA about sand dunes on Mars. In some areas, dunes have been observed to migrate over time, while on others the patterns have remained stock-still—some of them for perhaps thousands of years, or longer.

So I had successfully created the right conditions for a migrating sand dune. What about static dunes? Well—I had noticed already that some of the pyrite rock obstacles that I placed in the sand stream formed small dunes in the wind-shadows of their leeward sides. The rocks weren't moving, and so the dunes they were nurturing and protecting remained in place.

Some of the static dune ripples observed in Meridiani Planum—where the rover Opportunity is exploring—have been explained as possibly being protected by the presence of "blueberries": tiny nodules of gray hematite that have eroded out of Martian rocks, but which themselves are erosion-resistant, and too large (1-3 millimeters) to be carried by the wind. The blueberries, as the explanation goes, embed in the sand and form a protective "armor" layer for the dune ripples, which remain safe and still in their lee.

Where else do we find dunes, other than Earth? Well, you need wind of sufficient strength and sand of sufficiently small size, for starters. We don't know about dunes on Venus; Venus has a thick enough atmosphere, but the winds may be too sluggish to whip up much of a sand storm. The only other object with a thick enough atmosphere and a solid surface is Saturn's moon Titan—and in fact we have pictures of Titanian dunes taken by Cassini.

Now I'm feeling that old itch to make another trip to my favorite place in the Solar System, Death Valley, to explore the macroscopic dunes of Stovepipe Wells . I'll send a postcard….

California's wind power. Credit: Elizabeth Pepin.

When it comes to renewable power, California has had one main message: bring on the solar power, bring on the wind turbines! California and the country are heading fast towards a clean energy future. But renewables aren't perfect. As wind, solar, and other nature-dependent technologies start to make up a bigger and bigger part of our electricity mix, power providers are thinking about how to deal with a very real problem: you can't tell nature when to produce.

The issue with these variable, intermittent sources of power is that electricity is a "just in time" commodity: you use it as soon you make it. When you flip on the light switch in your house or push start on your electric dryer, a power plant somewhere is whirring away right at that moment, creating those electrons for you to use.

In most of California, that complicated balance is coordinated by the California Independent System Operator, or ISO, a nonprofit that serves as a link between power generators and the utility, such as PG&E. Every four seconds, the ISO "takes the pulse" of the grid to make sure that the supply of electrons flowing out of the power plants matches the demand for electricity. If there's a mismatch, the ISO can tell plants to cut back or ask other ones to turn on.

That's not an instantaneous process, though. What makes the ISO's job complicated is that power plants have different levels of responsiveness. Nuclear plants, for example, are slow to turn on or off, so they usually just hum away at a relatively constant rate, providing "baseload" power – the minimum amount of electricity we always need. Other plants, including hydroelectric and natural gas, can ramp up and down quickly throughout the course of a day, as factories switch on their machinery and air conditioners rev up.

Unfortunately, renewables such as wind and solar are even less accommodating. The wind blows when it blows – often at night, when demand for electricity is low. The sun is more predictable, but passing clouds can change a solar panel's output, and just because we know when the sun will be high doesn't give us any control over it. Put too much of this kind of energy on the grid, and the system stops being reliable (though researchers disagree about how much exactly is "too much").

According to California's policies, more solar and wind is what's in store. The state has an ambitious goal of getting 33% of its electricity from renewable sources by 2020. So how can power providers make sure the right amount of juice is flowing through the grid when more of those electrons come from sources you can't "dispatch" on-demand? One answer might be energy storage. Stayed tuned for an upcoming post on that.

Since people seem to nod off a bit when I say I'm working on a story about energy efficiency, I've had to re-tool my pitch. "It's a story about how installing solar panels or a wind turbine is the last thing you should do to green your house," I say, perhaps a little over-dramatically.

I have nothing against solar panels, but they do seem to illustrate our collective love of gadgetry. Why else would we leap (or at least dream of leaping) to spend $5,000-$10,000 on solar panels when many of us could make a significant dent in our utility bills with a trip to Home Depot? Small things, like weather-stripping your doors, or making sure you have a well-insulated attic, can make a big difference in how much heat or AC your house consumes.

If you qualify as low-income (in this case, that's less than $44,000 for a family of four) you can get help with this project. If you live in California, you'll find your local participating agency here (or by calling 1-866-675-6623). Elsewhere, begin by contacting your state agency, found here. The Weatherization Assistance Program has received a 10-fold budget increase under the American Recovery and Reinvestment Act, so now's a great time to apply.

WAP won't replace your TV, but you might consider doing so yourself. Televisions tend to be the third biggest electricity user in the house (after heating/AC and refrigerators). But they don't have to be. All the new features — plasma screens, HD, widescreen — can be (and are, in some models) achieved using less electricity. The California Energy Commission is proposing new TV standards that would cut electricity use by a third.

James Sweeney, who heads the Stanford University Precourt Energy Efficiency Center, calculates that collectively – with current, affordable technologies, and without sacrificing our quality of life – Americans could cut our energy use by 30 percent.

Here's the kicker: To produce that same amount of electricity, we'd have to increase solar and wind by 60-fold. That means, for every solar panel and wind turbine in the country, we'd have to build 59 new ones, plus all the power lines and roads they'd entail. Or, to consider another non-fossil fuels alternative, that's four new nuclear power plants for every existing one.

Listen to the Let's Weatherize! radio report online, and watch our Weatherization Slideshow.