Underground Parks

It’s not easy to keep growing cities green when there is such a high demand for building space. But nobody wants to live in a concrete jungle, which is why a company in the US has proposed a rather unusual solution: underground parks.

Inspired by New York City’s High Line, an abandoned elevated freight railway turned urban park, “Lowline” hopes to use pioneering solar technology to repurpose a former trolley terminal into a public space.

The one-acre former trolley terminal, which was abandoned in 1948, is located in the Lower East Side of Manhattan, an area which is considered “one of the least green areas of New York City,” according to Lowline’s website. Despite long-term neglect, the site has maintained some interesting features, such as old cobblestones and rail tracks, some of which Lowline plan to keep as a way of showcasing the history of the site.

The idea behind Lowline is to not only provide more green space, but to demonstrate how innovative solar technology can be used to transform cities. Alongside providing residents with a pleasant area to relax in and escape from the hustle and bustle of the city, the park will host a variety of cultural events, art exhibitions and youth activities.

To illuminate the underground area and feed all of those plants and trees, street-level reflective parabolas will be used to collect sunlight and direct it underground via fiber-optic cables. The light will then be dispersed through the park by aiming it towards reflective dishes. The solar collectors will be positioned in areas that receive lots of sunlight, and will be adjustable so that they can follow the sun as it moves, maximizing the amount of light that can be collected. When insufficient sunlight is available, electricity would be used to light up the park instead.

The project comes with a $60 million price tag, which will mostly come from private investors, although the government has agreed to fork out some cash, too. So far, over $1 million has been raised for research and design.

Construction is anticipated to commence in around five years’ time, but first Lowline needs to overcome some technical hurdles, such as working out the best way to channel the collected sunlight underground. 

polymer blend conductor

While plastics have become an indispensable material in modern society, they are not very useful for certain applications because of how heat doesn't disappate from them easily. However, a group of material scientists have developed a polymer blend that not only exceeds the heat dissipation of other plastics, but is about ten times more efficient than conventional materials like metal and ceramic as well. The project was led by Kevin Pipe of the University of Michigan, and the paper was published in Nature Materials. 

Plastics are synthetic polymers that are composed of repeating molecule chains. They are generally more lightweight and resilient than metals and glass, but the molecular arrangement does not allow heat to be removed easily when it is needed, like in automobiles and computers. Previous attempts to make a polymer blend that fits the bill have been adulterated with other materials, which detracts from the appearance and utility of the material.

"Researchers have paid a lot of attention to designing polymers that conduct electricity well for organic LEDs and solar cells, but engineering of thermal properties by molecular design has been largely neglected, even though there are many current and future polymer applications for which heat transfer is important," Pipe said in a press release. 

Plastic devices tend to trap heat, which is not desirable for uses like in smartphones. Heat energy needs strong and stable pathways to travel and dissipate, but the connections of most polymer chains tend to be too weak to transfer heat efficiently.

"The polymer chains in most plastics are like spaghetti," Pipe explained. "They're long and don't bind well to each other. When heat is applied to one end of the material, it causes the molecules there to vibrate, but these vibrations, which carry the heat, can't move between the chains well because the chains are so loosely bound together."

Pipe's team manipulated the hydrogen bonding patterns by blending short stands of polyacryloyl piperidine (PAP) with a series of other polymers known to conduct heat well in order to create amorphous polymers. Ultimately, PAP blended with long chains of polyacrylic acid (PAA) produced the strongest result, with hydrogen bonds between 10 to 100 times stronger than traditional plastics. These strong bonds produced a better route for heat transfer.

"We improved those connections so the heat energy can find continuous pathways through the material," co-author Jinsang Kim explained. "There's still a long way to go, but this is a very important step we made to understand how to engineer plastics in this way. Ten times better is still a lot lower heat conductivity than metals, but we've opened the door to continue improving."

It's important to point out the PAP/PAA blend by Pipe's team uses conventional MANUFACTURING techniques. The ability to easily mass-produce the material is integral to facilitating its widespread use. With further development, amorphous polymers like this one could potentially be used to replace metal components in computers, automobiles, and aircraft. This could make the devices more lightweight, and increase efficiency.