How Will The Clean Energy Revolution Change City-Building?

Nate Lewis

Solar paint, self-charging roadways, and carbon-absorbing carpeting may seem far off, but these innovations may already be on their way to a city near you. How quickly these transformative technologies are developed and deployed remains to be seen. At the CityAge gathering of thought leaders, Caltech professor of chemistry Nate Lewis discussed the myriad clean technologies emerging to solve challenges facing the built environment, especially in its interconnection with the transportation sector. As new technologies and applications of data continue to demonstrate new implications for city-building, Lewis explores the cutting-edge innovations that will help build and run our cities in the near future. VX News presents an except of the presentation.

Nate Lewis: We all know the existing state of play with respect to solar panels, wind turbines, and gas. But the clean energy revolution will change city-building. It will influence transportation, the built environment, and—through IT—efficiency at the holistic, metropolis level. To plan city infrastructure that might well have to last 40 or 50 years, we can’t plan with just the existing toolkits that we have now. So many new options will become available to us in just the next 10 or 20 years; we don’t want to lock in existing approaches and not able to take advantage of what’s coming down the pipeline.

I’d like to talk about what is here today, what is likely soon to be here—at the pre-commercial level—and what is going to be here tomorrow, with the understanding that energy systems are a very dynamic, fluid environment. Today, in the city of Los Angeles, regulations say that if you sell a home, you have to first bring it up to the state of the art in water conservation. For instance, you have to have low-flow toilets installed. That’s a wonderful regulation to have. And I cannot figure out why, but we don’t have it for the energy system in that very same house.

It would be very simple to require that, when a house is sold or a long-term lease on a commercial building is reinitiated, it be brought up to at least some standard of energy efficiency in terms of lighting and HVAC. It could go into the mortgage on the house. There could be banks that would do that under green loans. Everybody could save money, and it would get our infrastructure rejuvenated more quickly.

There are other things that we can and should do in terms of operations of the house. There’s no reason at all we can’t implement appliances that would, for instance, run the compressors on the refrigerators during what is now off-peak to help balance the load. Other systems, too, could be not only net-zero, but also optimized to achieve more than just zero­—to balance out the system as a whole.

Of course, architecturally, we’d like the net-zero house to look great at essentially no cost relative to existing building design. In planning suburban areas, or even commercial buildings, folding design principles into these regulations makes a lot of sense.

That brings us to what’s coming soon. Dye-sensitized solar cells are a new kind of solar cell that goes on the windows instead of the roof. They aren’t as cost-effective or efficient as the cells that we put on solar panels on roofs—at least, not if your value proposition is simply, “Make me cheap electricity.” But they have a lot of other co-benefits when it comes to planning.

This technology is very aesthetically pleasing and can be made in a wonderful array of potential colors, so the experience inside the building is enhanced. It also helps with thermal management, because it absorbs the infrared—the heat—that would otherwise come in through the windows. And it can be electrochromic, so you can automatically darken or lighten it.

A variant on this technology is already here. The pigment in these cells—titanium dioxide, which is in sunscreen—when made photoactive, give us another way to use the sun’s energy: to keep things clean. Dirt doesn’t accumulate, and the white stays white. In terms of planning, this could mean literally self-cleaning buildings, tunnels, and walls, with no maintenance involved.

This is an existing product. There’s only a relatively small company making it now, because they can’t yet compete at the utility scale. But in the hands of architects, it could be a very valuable tool.

Another thing that’s coming very soon is in wind technology. We’re familiar with big wind turbines, like the ones out in San Gorgonio Pass. The new technology is small micro-turbines, which are much more amenable to being integrated into the urban landscape. You could have them on tops of buildings and they would look like antennae, for instance. Or you could have them between buildings in such a way that you might not even necessarily see them. They could be deployed like cell phone towers. Wind doesn’t have to be only in our backyards, but can be integrated into cities in a much different way than we think about now.

As for what’s coming “tomorrow,” there’s something I work on in my laboratory that most people only dream about—but it’s coming. We have prototypes of it, and other laboratories do as well. It’s solar paint.

Wouldn’t it be great if you didn’t have to pay somebody to install big, heavy solar panels and an electrician to hook them up—if instead you could go to Home Depot, buy a bucket of paint, and essentially make any surface a solar panel?

In fact, you need a few coats of paint: the base coat; the metallic layer to conduct the electricity; the absorber layer, which could be different colors; and a transparent protective layer on top. We already have small samples of all of those that function.

It would change the whole way we think about getting energy into a building, if we could empower consumers to retrofit their own homes or commercial buildings.

In the transportation sector, the promise of self-driving cars brings many things to think about from a clean energy and city planning perspective. Of course, the cars should run on either electricity or hydrogen in order to achieve zero tailpipe emissions. But one of the key barriers to overcoming range anxiety is the fact that there’s really no such thing as a rapid-recharge on a battery in a car. We have to charge them up much slower than we discharge them. Otherwise, the heat generated would be enough to melt the car. There’s no way around that—except to swap the plates of the battery.

A company called A Better Place tried to do that, but they found it was very difficult to expect lots of consumers to swap their batteries every night. But if we think about self-driving cars in fleets, then suddenly, it becomes very easy to envision. Before they get out of range, they go to a central depot where the swap happens. Five minutes later, they’re back on the road. Then the other battery plates are recharged, and so on. This allows a higher utilization of the vehicles.

In San Francisco, Boston, and many other urban areas, only 20 percent or so of the vehicles are actually parked in garages. The rest are on out on curbs and in other places. So even if we all had battery-powered cars, unless we were to re-plan the whole electric utility infrastructure, how would we get the power lines up to every parking spot to charge them?

If we’re really going to take advantage of this new technology, planning for central depots is a way to avoid dealing with a whole new electric utility infrastructure. This is something we would need to think about as city planners, because it means that we would no longer be planning for gas stations on every corner. In the parking structure where I parked my car today, something like 10 megawatts would be needed just to charge the thousand or so cars in that one parking structure in that one building. We need to plan for the electric needs of that city if we want to make widespread electric vehicles a reality.

That being said, hydrogen and electricity are both really in the race; they have different advantages and disadvantages. Hydrogen vehicles have much more range and much faster recharges than battery vehicles; the fuel-cell side is more expensive, although that’s coming down. If it turns out to be hydrogen vehicles that we drive in the future as opposed to electric, then we still won’t be planning for corner stations. Again, we’ll be thinking about central depots —but these would allow us to refuel with hydrogen, and could change the way we plan freeways. In urban planning, we need to think not just about our current toolkit, but also about the toolkit of the future. We need to plan for optionality—because if we don’t, we’ll cut out the options altogether.

Another point I want to touch on in the clean energy economy is the contribution of IT. At NYU, the Center for Urban Science and Planning (CUSP) is using big data to learn everything they can about the operations of the city. They’re collecting everything about everything—not just whether the subways are running on time, but also all taxi cab trips to and from anywhere in Manhattan for the last five years. They know what the water system is doing every minute of every day in every pipe. They know, just from observing infrared cameras, every time anybody turns on a heater or an air conditioner or a light bulb in every apartment in every part of every borough of that city.

Now, they can start to ask questions. For instance: Knowing the patterns of resource utilization, how can things be optimized to leave just enough time, just enough buses, and just enough gasoline to get everybody out of Yankee Stadium at a certain time? If you understand from big data the heartbeat of the city and all of its utilization dimensions, you can use that to help plan and optimize the city itself, and make a better environment for people.

So what could be different? The problem with solar and wind is: He who cannot store shall not have power after four. On top of that, there are days and weeks in the summer doldrums when the wind doesn’t blow, and at night, the sun doesn’t shine. We’ve got to find a way to deploy very large amounts of non-natural gas storage to balance the whole energy system.

One alternate way to store energy that’s up and coming is flow batteries. They’re holding tanks, and the fluids that give the charge flow through them. You could store up energy in the daytime from the sun, flow it through, and then have a discharge in the tanks at night. Then you just reverse the process.

Flow batteries, as well as other systems that exist now, could be integrated underneath homes—in the basement, basically. Think of a water heater that holds the contents of all the electricity it would take to refuel your car. Or they could be placed adjacent to solar farms, which would need to be considered in land allocations.

Solar panels are real. Batteries are real. Solar thermal systems are real. The thing that I personally work on is something I’m sure less of you are familiar with. We want our system to become real, because it gives us an option that we simply do not have in the clean energy environment now.

Plants long ago figured out that the best way to store energy was to take the sun and put its energy in chemical bonds. That’s the source of all stored energy on our planet—the chemical bonds of oil, coal, and gas. We’ve now cracked this, and developed something that is now shown to be attainable, though not yet practical: making fuel directly from the sun.

Our technology is 10 times more efficient than a plant. And unlike the stuff we put in our green waste bins, it’s a fuel you can directly use, like hydrogen or gasoline, in one step. It could drive our energy economy, and as a consumer, you would never know that it came from a renewable, sustainable source as opposed to from fossil energy. There are no environmental mis-consequences, and there’s plenty of sunlight available for all the world’s countries to generate their own energy forever.

It is essentially a high-performance fabric with nanofibers that we invented. Some of them are blue to absorb the blue parts of light; some of them are red to absorb the red part of the rainbow. There is a membrane in between to serve as a support. It vents the oxygen into the air and then wicks out the product.

You literally roll it out; it looks like artificial grass, except that it’s connected to a bunch of PVC pipes that can leech out chemical fuel that you can use to power your car or your natural-gas-fired water heater. Anything that cannot be electrified that needs fuel—vehicles, airplanes, ships—could be running 24/7 off of a sustainable source. That’s something that would really make a difference compared to the options we have now.

I hope I’ve given you some idea of what’s here today, what’s soon, and what’s tomorrow—as well as, hopefully, some new horizons to think about incorporating optionality into cities so that we can take advantage of whatever they invent in the future to make it a better place than what we would have otherwise.

"In urban planning, we need to think not just about our current toolkit, but also about the toolkit of the future. We need to plan for optionality—because if we don’t, we’ll cut out the options altogether." - Nate Lewis