NASA Patents in the Public Domain
As part of its mission to share technological advances with the general public, NASA has released 56 patented technologies into the public domain, allowing industry to use these innovations in their designs without having to pay royalties. Today I'll look at a few that could significantly impact the renewable energy industry. I've embedded links to the patents, in case you'd like to see the gory details. If you've never read a patent application, you're in for an interesting experience; it's like an academic paper on steroids. I swear, there must be an employee at the patent office whose job is to reject all applications that aren't sufficiently obfuscated. With that said, I'll do my best to translate the lawyer-speak into English for you.
Carbon nanotubes represent a technology that can solve a wide variety of engineering problems, if only they weren't so expensive to manufacture. NASA developed an inexpensive method of producing carbon nanotubes by inducing an electric current through a carbon anode and cathode. The process could make carbon nanotubes an affordable alternative in new designs.
Mechanically, carbon nanotubes' high strength-to-weight ratio will allow vehicles to shed unnecessary weight, improving range (electric vehicles) and fuel economy (internal combustion vehicles). Lighter and stronger materials will enhance the wind industry, making turbines less expensive and more efficient.
On the electrical side, carbon nanotubes possess excellent conductive properties, and can even serve as high-speed semiconductors in the next generation of computers. Engineers have developed Li-ion batteries with carbon nanotube electrodes, which dramatically increase the number of recharge cycles and decrease the batteries' internal resistance. Researchers at MIT have experimented with carbon nanotubes as heat absorbers in thermophotovoltaic cells, allowing the cells to use a wider portion of the solar spectrum, increasing their efficiency and giving the potential to generate electricity at night. It's also possible that someday we'll have highly efficient and inexpensive photovoltaic cells made entirely of carbon nanotubes instead of silicon.
When the blades of a wind turbine (or the rotors of a helicopter) rotate, small, yet powerful, vortices - pockets of swirling air - are formed at the blade tips. These vortices cause turbulence and drag, resulting in a loss of energy and an increase in noise. NASA developed a vortex control system that consists of a movable flap at the tip of the blade and a sophisticated control algorithm that causes the blade tips to move in such a way as to disturb the vortices. In effect, the system detects the formation of a vortex and precisely adjusts the flap so that the vortex is stifled, preventing its turbulence from interfering with the next blade.
Vortex reduction on wind turbines improves their efficiency, decreases the noise that they produce, and reduces the wear and tear on the blades, which helps to lengthen their productive lifetimes.
Photovoltaic Array with Integrated Bypass Battery
A solar cell acts as a light-dependent current source; as the light reaching the cell increases, the cell produces more current. In a solar panel, individual cells are connected in series in order to increase the total voltage. But elements in series also experience the same current, so if one cell in a panel is shaded, the total current of the panel is limited to the current output of the shaded cell, resulting in a decrease in power, as shown here:
Image: Tom Lombardo
The traditional method of dealing with this is to connect a bypass diode across a cell (or a group of cells). When a cell experiences low light, the bypass diode effectively takes it out of the circuit, allowing the higher current from the unshaded cells to flow freely. There's a negative side-effect of this: the overall voltage out of the panel decreases. Not only are we losing the voltage of the shaded cell itself, but the bypass diode drops a certain amount of voltage as well. If enough cells are shaded, it could prevent the array from delivering a high enough voltage to meet the inverter's startup voltage requirement. A bypass diode is the lesser of two evils, but it leaves something to be desired.
NASA's engineers have developed a PV panel that integrates thin-film energy storage along with thin-film photovoltaics. The energy storage device is a tiny Li-ion battery that's used in place of the bypass diode. When a cell receives light, a small amount of energy charges the battery. When the cell is shaded, the battery substitutes for the cell, delivering voltage and current during the shading period.
This technology was originally developed for PV devices that power orbiting spacecraft, which only experience brief moments of partial shading from parts of the spacecraft such as an antenna. It does not address the 45 minutes of shading that the craft experiences when it's eclipsed by the Earth. As such, the integrated batteries have very low capacities - we're talking about 30 mAh or so. (To put that into perspective, a rechargeable AA battery provides about 2000 mAh.) Nonetheless, the patented design does allow for batteries of larger capacities, which could lead to integrated power sources that feature PV cells, batteries, and control electronics. It probably won't lead to batteries integrated into rooftop PV panels, however.
I'm sure I've only scratched the surface of the potential applications that could grow from these patents. Please comment below with your ideas.
Images (except where noted) courtesy of NASA
Follow Dr. Tom Lombardo on Twitter, LinkedIn, Google+, and Facebook.