New Production Process Boosts Cheap Solar Cells’ Efficiency

by Cameron Scott

Photovoltaic solar cells are available in two types — crystalline silicon cells, which are more efficient but more expensive, and amorphous silicon cells, which are less efficient but cheaper and thinner and therefore more adaptable. New research from the Technical University of Delft, Netherlands, has found that using hydrogen in the production of amorphous silicon, or “thin film,” cells can increase their efficiency from the usual 7 percent to roughly 9 percent.

  

Researcher Gijs van Elzakker simply diluted the silane gas already used to produce the solar cells with hydrogen to achieve the results, meaning that the improvement is essentially free. Elzakker, who will receive his Ph.D. today (gefeliciteerd!), has already taken his findings to the German company Inventux Technologies, where he works.

World’s First Molten Salt Solar Plant Produces Power at Night

by Philip Proefrock

Sicily has just announced the opening of the world’s first concentrated solar power (CSP) facility that uses molten salt as a heat collection medium. Since molten salt is able to reach very high temperatures (over 1000 degrees Fahrenheit) and can hold more heat than the synthetic oil used in other CSP plants, the plant is able to continue to produce electricity even after the sun has gone down.

While photovoltaic solar panels work by directly producing electricity from sunlight, CSP plants use mirrors to concentrate sunlight and produce high temperatures in order to drive a turbine to generate electricity. CSP plants have been in existence for many years, but the Archimede plant is the first instance of a facility that uses molten salt as the collection medium.
Heat from the molten salt is used to boil water and drive the turbines, just like other fossil fuel plants. CSP plants use the same kind of steam turbines as typical fossil fueled power plants. This makes it possible to supplement existing power plants with CSP or even to retrofit plants to change over to clean energy producing technology. Some existing CSP plants have used molten salt storage in order to extend their operation, but the collectors have relied on oil as the heat collection medium. This has necessitated two heat transfer systems (one for oil-to-molten-salt, and the other for molten-salt-to-steam) which increases the complexity and decreases the efficiency of the system. The salts used in the system are also environmentally benign, unlike the synthetic oils used in other CSP systems.

Since molten salts solidify at around 425 degrees F, the system needs to maintain sufficient heat to keep from seizing up during periods of reduced sunlight. The receiver tubes in the Archimede facility are designed to maximize energy collection and minimize emissions with a vacuum casing that enables the system to work at very high temperatures required with molten salts. By using the higher temperatures of molten salts, instead of oil, which has been used in other CSP plants until this point, the plant is able to maintain capacity well after the sun sets, allowing it to continue generating power through the night.
The Archimede plant has a capacity of 5 megawatts with a field of 30,000 square meters of mirrors and more than 3 miles of heat collecting piping for the molten salt. The cost for this initial plant was around 60 million Euros.

Super-Efficient White OLED Lights

GE Unveils Super-Efficient White OLED Lights

High-efficiency organic light-emitting diode (OLED) lighting is closer than ever to commercialization, and recently GE scientists announced that they have devised a new way to make high-efficiency, low-cost OLED materials. While many companies in the OLED display industry use vacuum-based batch production processes, GE will use a high-speed, roll-to-roll process that is significantly more efficient. This kind of roll-to-roll processing is already used in the printing industry, and it means, according to John Strainic, global product general manager for GE Lighting, that “we’re starting to see the OLED light at the end of the tunnel.”

The ultra-efficient OLEDs aren’t ready for mass consumption quite yet — GE’s first flexible OLED lighting product will be released in 2011. No word yet on pricing.

New Type of Light Matter Interaction Could Advance Energy Efficiency

by Brit Liggett

Researchers at the University of Maryland have taken a huge step forward toward significantly enhancing energy efficiency and conversion. Using a unique hybrid nanostructure they have discovered a previously unknown type of light matter interaction and displayed the first full quantum control of qubit spin (we had trouble understanding exactly what that meant too – read on for more info) inside tiny particle nanostructures. The advancement pushes them one step closer to a real quantum computer and already has them on the road to developing super efficient photovoltaic cells.

“The real breakthrough is that we use a new technology from materials science to ’shed light’ on light-matter interactions and related quantum science in ways that we believe will have important applications in many areas, particularly energy conversion and storage and quantum computing,” lead researcher Min Ouyang told Science Daily. He added that his team is already well on their way to using this breakthrough to apply their, “new understanding of nanoscale light-matter interactions and advancement of precise control of nanostructures to the development of a new type of photovoltaic cell that [they] expect to be significantly more efficient at converting light to electricity than are current cells.”
The team of researchers at the University of Maryland have conceived of a patent-pending process where they employ chemical thermodynamics to produce a broad range combination materials. Each material has a shell made from a mono-crystal semiconductor around a metal core that is structurally perfect. The researchers believe that these crystal-metal hybrid nanostructures were the key to their successes. Research similar to this has been achieved in the past but the nanostructures used were more complex and more expensive than the crystal-metal hybrid nanostructures that Ouyang and his team used. The relative cost effectiveness of their process has them hoping that their discovery could be easily implemented in the computing and energy industries without a huge cost drain on production.

Move Over OLEDs: Scientists Create Cheap, Fully Recyclable Lighting Material

by Brian Merchant, Brooklyn, New York

Photo via Gizmag
Swedish and American researchers have just developed a fully recyclable lighting component with what Science Daily is terms a "new super material": graphene. Graphene is both inexpensive to produce and is 100% recyclable, and could be used to create glowing wallpaper made out of plastic--much like OLEDs could. But graphene appears to improve on OLEDs in some very big ways . . .

As you know, we've been big fans of the very efficient, long-lasting Light Emitting Diodes and Organic LED technology. But as Science Daily notes, there are still problems:

Today's OLEDs have two drawbacks -- they are relatively expensive to produce, and the transparent electrode consists of the metal alloy indium tin oxide. The latter presents a problem because indium is both rare and expensive and moreover is complicated to recycle.

A graphene lattice
Researchers believe they've found a solution by creating an organic light-emitting electrochemical cell (LEC) with the transparent electrode made of the "carbon material graphene." Graphene is used instead of conventional metal electrodes--and since everything in an LEC, including the graphene, can be created from liquid solutions, they will be able to be produced through a printing process. This makes them much more efficient--and much less expensive--to create en masse than OLEDs. Researchers involved in the project say that graphene paves the way for cheap production of plastic-based lighting, perhaps for the first time.
So what does this graphene consist of? SD has the skinny:

Graphene consists of a single layer of carbon atoms and has many attractive properties as an electronic material. It has high conductivity, is virtually transparent, and can moreover be produced as a solution in the form of graphene oxide.

Of course, we'll have to wait until more tests are done to get a fuller idea of its lifecycle and range of applications, but this seems like pretty intriguing news indeed

LEDs

Bright forecast for LED lighting

by Candace Lombardi

LEDs are about to have their day in the sun.
By 2020, nearly half (46 percent) of the $4.4 billion commercial lighting business will be given over to LED lighting, according to a Pike Research report released Wednesday, "Energy Efficient Lighting for Commercial Markets."

The 6th Street Bridge in LA now basks in the light from LEDs.

(Credit: City of Los Angeles/Bureau of Street Lighting)

Because of their energy-frugal characteristics, LEDs (light-emitting diodes) have always had the potential to save commercial properties a significant amount of money on their electricity bills. However, the initial expensive of the lighting systems have made LEDs cost-prohibitive in many situations. Not so anymore, according to Pike Research.
The prices for commercial solid-state lighting systems have come down and will continue to decline enough to make them a practical and attractive option for commercial properties. There are federal and local government incentives to install LEDs in new buildings and as retrofits in existing properties. For these reasons, people can expect to see a significant increase in the use of LED lamps for commercial and industries properties, according to Pike Research.
The shift to LED installations will start outdoors.
LEDs, which have already seen an increase in installation for traffic lights and exit signs, will saturate the market for outdoor lighting within a few years, according to Clint Wheelock, managing director at Pike Research.
One doesn't have to look to hard to see anecdotal evidence of this already happening. An abundance of U.S. cities and towns have been announcing programs to install LEDs for municipal lighting. In one notable example, the Bureau of Street Lighting for the city of Los Angeles has been replacing much of LA's municipal lighting with LEDs, including all 209,000 streetlights. As a result of the change, LA has started to give off a different glow at night in addition to seeing a 40 percent reduction in its annual energy consumption for public lighting.

 Candace Lombardi, a freelance journalist based in the Boston area, focuses on the evolution of green and otherwise cutting-edge technologies, from robots to cars to scientific innovation. She is a member of the CNET Blog Network and is not a current employee of CNET.

 

Scientists Find Way to Turn LED Lights Into Wireless Internet Source

Photo: Velo Steve via Flickr
LEDs are already known for being a super energy efficient way to light up a room, but did you know that they might also be a way for you to connect to the internet? That’s right, a group of scientists from Germany’s Fraunhofer Institute have devised a way to encode a visible-frequency wireless signal in light from our plain old desk lamps and other light fixtures. Just think – in the near future, jumping on the interwebs might be as simple as flipping on your light switch!

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Set Your Own Mood Lighting With An LED Light Wand Ceiling

by Bridgette Meinhold

If you had a ceiling like this one, which is completely covered in LEDs, you could, on a whim, change the lighting in your room. Draw The Lights, by Seo Dong-Hun, is a concept for a customizable LED ceiling composed of a network of energy efficient LED lights, a few sensors and a light wand. Need brighter light right above you to read? Use the light wand to turn on more lights. Want to create a special pattern for a party? You can paint the ceiling with lights to fit your mood.

In most houses, you would need a complete remodel in order to reposition lights if you want to move your furniture around. Dong-Hun’s concept for a customizable ceiling would give you the flexibility to light for different settings, parties or work. Composed of a ceiling web of circular LED units, patterns and moods can be drawn into the ceiling via the light wand, which communicates with the sensor inside the LED unit.
Users can set the light type as well as the color for each unit across the whole ceiling. And since all of the lights are LEDs, the lighting system is energy efficient and could have the potential to save energy, since you can create the ambiance that fits your needs. And it’s pretty unlikely that you would ever need the entire ceiling of lights on at once.

Smart Lighting? Software-Controlled Networked LED Lights Save Tons of Power

by Michael Graham Richard, Ottawa, Canada

Design & Architecture (lighting) 

Photo: Digital Lumens
A Bright Idea for the Lighting Industry
According to the US Department of Energy, lighting represents about 12% of energy consumption for residential buildings and 25% for commercial ones (presumably because commercial buildings are kept much brighter than residential homes on average). That's a lot of energy, and despite recent improvements thanks to CFLs (check out the safer ArmorLite CFLs) and LED lights, a lot more can still be done. That's the mission of a two years old startup called Digital Lumens.

Photo: Digital Lumens
Digital Lumens makes networked LED light fixtures that, it claims, can save up to 90% compared to regular HID lights typically used in warehouses and commercial buildings. It does that with sensors and software that control precisely how and when the lights are used.

• Intelligent Light Engines™ - Intended as one-for-one replacements of 400W HID, HPS and T5 or T8 fluorescent fixtures, Digital Lumens Intelligent Light Engines (ILEs) are white-light LED-based luminaires that provide desired light levels on the target surface, while minimizing kWh consumption. Easy to install, each ILE has a built-in Digital Light Agent™ - an on-board computer - as well as sensors and wireless mesh networking capabilities that share key information across the system.
• Smart Light Grid - Digital Lumens Intelligent Light Engines form a Smart Light Grid - a lighting network - that enables all fixtures in the system to communicate with each other, respond to a neighboring fixture's state and/or system-wide programming, and provide usage and occupancy data to the Light Rules management system.
• LightRules™ - Digital Lumens' intuitive control and energy management software gives facility managers the tools to effectively manage their lighting resources and energy use. They are able to specify system behavior, receive up-to-the-minute kWh consumption details by fixture/zone/day/shift and control the entire system for maximum energy efficiency. LightRules also provides the ability to respond to demand response calls and integrate with warehouse management, energy carbon accounting or other third-party systems.

So if more daylight is available, less artificial light will be used. The system can be programmed to know when certain zones need more light during the day, or to sense when people enter a room and adjust lighting accordingly.
Another way to extract further savings from LED lights is described by Technology Review. A company called Redwood Systems uses centralized power supplies for their LED lights, removing the need for redundant AC/DC converters at each fixture (LEDs use low voltage DC current, while what comes out of the wall is AC).
"The new system converts alternating current to low-voltage direct current at a central location, rather than at each light. This more efficient method cuts energy consumption by 10 to 20 percent, according to Jeremy Stieglitz, vice president of marketing for Redwood Systems, which will start selling its systems this summer."
So in the future, expect to see smart LED lights that are networked and running on low-voltage DC.

Inhabitat

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Philips Lumiblade Reflections OLED Mirrorwall Now Available

by Lea Bogdan

When we saw the debut of the Philips Lumiblade Mirrorwall prototype last year in a special exhibition during the Milan Furniture Fair, we fell head over heels for this sophisticated use of lighting technology. The series of linked OLED modules act as a mirror in the off state, and as an interactive lit curtain wall when powered. Well, it's been almost a year since the prototype debut, and Philips has announced that a version of the mirrorwall, called Lumiblade Reflections, will be available for sale in limited quantities. The technology is cutting edge, extremely energy efficient, and perfect for the eco-enthusiast looking to splurge on one of these limited edition museum-worthy products.P.S. Thanks to reader mertero for tipping us off!

Lumiblade tiles use OLED technology, which allows for a very homogenous surface light. Unlike LEDs, this light will never have those pesky hot spots. OLEDs work by passing low levels of electricity through thin layers of organic semiconductor materials. In other words, the tiles are a stack-up of films that can be electrically charged, causing them to become “excited” and emit light. Right now, the tile sizes are limited in size, but they can be linked together into endless configurations.
OLEDs are superior to LEDs in their even output, their flat form, and their minimal circuitry required for powering. OLED is extremely energy efficient with ratings for white modules providing up to 15 lumens per watt. Efficiencies depend highly on the colors, with white being the most efficient. Similar to LED technology blue emitters still have room for improvement, while green is also highly efficient. Certification bodies, such as Energy Star, typically rate lighting efficiency by efficacy, which is a ratio of lumens per watt. The white Lumiblade tiles provide approximately 15 lm/W. This is a great rating considering that these tiny tiles output 1000 candelas for up to 10,000 hours. As a comparison, the efficacy of a Philips 100 watt incandescent bulb is about 14 lm/watt, but only gives off 120 candelas for a lifespace of about 750-1000 hours.

In an off state, it is possible for the OLED tiles to be transparent, since the materials on the layers of sandwiched films appear to be clear. A mirror-like appearance, like that of the Lumiblade Reflections, can also be achieved by using specialty layers in the stack-up. The added feature that makes Lumiblade Reflections so outstanding is that it is interactive. The tiles have infrared sensors behind the illuminated panels that detect an object or presence, so when an object passes in front of the tiles, the OLED face dims to a mirrored surface. If one were to stand in front of the mirror, the tiles around their silhouette would stay illuminated, allowing for a very functional mirror and light in one!
In a Philips newsletter, it states that the special edition Lumiblade Reflections would cost approximately 5000€ ($6,798USD), which may not be practical for a household mirror for grooming your locks, but it sure would be a wonderful art piece. We have to consider that this is only the beginning for explorations in OLED technology and responsive lighting. Even though these first editions may not be in financial reach for all, the fact that they are commercially available suggests that we will see this technology translated to bathroom products, furniture, mirrors, and other household good in the near future.

Inhabitat

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Toshiba Kills Incandescent Bulb Production

by Sarah Parsons

Yesterday, Toshiba ended its manufacture of mass-market incandescent light bulbs–bulbs that use a ton of energy, burn out quickly and pale in comparison in terms of energy efficiency to CFLs and LEDs. The move ends the company’s 120-year history of incandescent bulb production. The decision signals that the lighting industry is poised to become significantly greener.

Toshiba initially planned to halt production of incandescents next year, but decided to push the date up. The company now aims to focus on creating LED lights, which are significantly more energy efficient than incandescents. Incandescents have drawn criticism from environmentalists in recent years because most of the power they consume is released as heat, so they need to use a ton of energy to produce light. Plus, the bulbs burn out quickly when compared to CFLs and LEDs.
The death of incandescents is proof that consumer choices and sound legislation can quickly and effectively improve the state of the environment. Australia started regulating the sale of incandescent bulbs last year, and countries like the EU and US are poised to implement regulations over the next few years. Now if only the world could adopt legislation to limit carbon emissions…
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All-

In the near future I believe that you will be able to do some phenomenal new things with LED lighting. Just a few of the current LED and LED solar applications available are:

LED panel light source used in an experiment on plant growth. The findings of such experiments may be used to grow food in space on long duration missions.

The LED destination display on a bus. Note how the camera has had difficulty catching all the LEDs.

Old calculator LED display.

Flashlights and lanterns that utilize white LEDs are becoming increasingly popular due to their durability and longer battery life.

A single high-intensity LED with a glass lens creates a bright carrier beam that can stream DVD-quality video over considerable distances. The device, RONJA, can be built very simply by enthusiasts.

LED lights on an Audi S6

LED sign advertisement.

Partial list of LED applications

Some of these applications are further elaborated upon in the following text.

Devices, medical applications, clothing, toys:

• Remote controls, such as for TVs and VCRs, often use infrared LEDs.
• Glowlights, as a more expensive but longer lasting and reusable alternative to Glowsticks.
• Movement sensors, for example in optical computer mice
• The Nintendo Wii's sensor bar uses infrared LEDs.
• In optical fiber and Free Space Optics communications.
• Toys and recreational sporting goods, such as the Flashflight
• Lumalive, a photonic textile
• In pulse oximeters for measuring oxygen saturation
• LED phototherapy for acne using blue or red LEDs has been proven to significantly reduce acne over a three-month period.^{[citation needed]}
• Some flatbed scanners use an array of red, green, and blue LEDs rather than the typical cold-cathode fluorescent lamp as the light source. Having independent control of three illuminated colors allows the scanner to calibrate itself for more accurate color balance, and there is no need for warm-up.
• Computers, for hard drive activity and power on. Some custom computers feature LED accent lighting to draw attention to a given component. Many computer manufacturers use LEDs to tell the user its current state. One example would be the Mac, which tells its user when it is asleep by fading the LED activity lights in and out, in and out.
• Sterilization of water and other substances using UV light.^[4]

Lighting

• Grow lights composed of LEDs are more efficient, both because LEDs produce more lumens per watt than other alternatives, and also because they can be tuned to the specific wavelengths plants can make the most use of.^{[citation needed]}
• Light bulbs
• Lanterns
• Streetlights
• Large scale video displays
• Architectural lighting
• Light source for machine vision systems, requiring bright, focused, homogeneous and possibly strobed illumination.
• Motorcycle and Bicycle lights
• Flashlights, including some mechanically powered models.
• Emergency vehicle lighting
• Backlighting for LCD televisions and displays. The availability of LEDs in specific colors (RGB) enables a full-spectrum light source which expands the color gamut by as much as 45%.
• Stage lights using banks of LED's as replacement for incandescent bulbs. LED's produce less heat so LED stage lighting is cheaper to operate and reduces the risk of fire considerably.
• LED-based Christmas lights have been available since 2002, but are only now beginning to gain in popularity and acceptance due to their higher initial purchase cost when compared to similar incandescent-based Christmas lights. For example, as of 2006, a set of 50 incandescent lights might cost US$2, while a similar set of 50 LED lights might cost US$10. The purchase cost can be even higher for single-color sets of LED lights with rare or recently-introduced colors, such as purple, pink or white. Regardless of the higher initial purchase price, the total cost of ownership for LED Christmas lights would eventually be lower than the TCO for similar incandescent Christmas lights^{[citation needed]} since the LED requires much less power to output the same amount of light as a similar incandescent bulb. More to the point, LEDs have practically unlimited life and are hard-wired rather than using unreliable sockets as do replaceable bulbs. So a set of LED lights can be expected to outlive many incandescent sets, and without any maintenance.

 Indicators and signs

• Status indicators on a variety of equipment
• Traffic lights and signals
• Exit signs
• Railroad crossing signals
• Continuity indicators
• Elevator push-button Lighting
• Thin, lightweight message displays at airports and railway stations, and as destination displays for trains, buses, trams, and ferries.
• Red or yellow LEDs are used in indicator and alphanumeric displays in environments where night vision must be retained: aircraft cockpits, submarine and ship bridges, astronomy observatories, and in the field, e.g. night time animal watching and military field use.
• Red, yellow, green, and blue LEDs can be used for model railroading applications
• In dot matrix arrangements for displaying messages.
• Because of their long life and fast switching times, LEDs have been used for automotive high-mounted brake lights and truck and bus brake lights and turn signals for some time, but many high-end vehicles are now starting to use LEDs for their entire rear light clusters.

Adding solar garden lights to your landscaping can add visual interest and increase visibility long after the daylight hours are gone. Use them to make outdoor areas more inviting, highlight an area, and add an element of safety outside. Solar garden lights come in weather-resistant finishes that withstand the outdoor elements. Depending on the type of solar garden light you choose, they may last anywhere from 8 to 18 hours at night. Choose solar garden lights that can effectively collect solar power even during overcast weather. You will be able to choose from a variety of styles from dramatic cracked-glass spherical lights to more traditional die-cast aluminum lights.

Solar lighting does several things for your outdoor space: It increases visibility, creates visual interest, highlights landscaped areas, and adds a measure of safety in the outdoors. This is how solar lighting works:

• First, solar light fixtures collect solar energy via solar cells.
• Then the energy gets stored within the batteries of the solar lighting.
• The amount of sunlight that a fixture receives as well as the sunlight conditions will affect the amount of time that a light will run at night.
• Shade from landscaping features and built structures will also affect the performance of a solar lighting fixture. In order to find out how long you can expect the fixture to run, check with the manufacturers specifications.

DuPont’s New Ink Can Quickly Print Cheap OLED Displays

by Ariel Schwartz

Want an ultra energy-efficient OLED television? You’ll have to pay — LG’s 15-inch display, for example, will cost a scathing $2,725 when it is released later this year. But OLED displays may not always be so pricey. DuPont has developed a new manufacturing process that can reportedly print a 50-inch TV screen that lasts 15 years in under two minutes. The development could eventually bring down OLED prices drastically.

DuPont teamed up with Japanese manufacturer Dainippon Screen to develop a garden hose-like printer that spews out a stream of ink, moving over a surface at rates of four to five meters per second all while patterning an OLED display. Today’s OLED printers use shadow-mask evaporation — a technique that patterns the organic molecules that make up the pixels in OLED displays. But shadow-mask evaporation only works at a small scale, unlike DuPont’s new printer.
We might not have to wait long to get our hands on DuPont’s cheap new displays. The company is already working to license its manufacturing process, which could bring OLEDs down to the cost of LED displays.

LED Technology

Energy Generating, Self-Heating Solar Roadway Unveiled

by Brit Liggett

The makers of the Solar Roadway just got a little closer to their dream of making every road in the United States a high-tech thruway that carries more than just cars. They’ve completed their first prototype and unveiled the photographs of the revolutionary energy-generating road surface. If installed on a real thoroughfare the Solar Roadway would carry vehicles, generate electricity for messages to drivers, self-heat to melt snow and ice, and deliver high speed phone and internet cables to the front steps of every home.


The makers of the Solar Roadway have high hopes for their product. In addition to creating a revolution in transportation infrastructure, they envision the installation of the Solar Roadway as a quick path to economic recovery. With some quick calculations they’ve estimated that installing the Solar Roadway on every road in the US will employ 2.5 million people full time for 10 years. That’s not to mention the manufacturing jobs that will be created to make the components in the road panels. It will take just over 5 billion panels to cover all the US roads and each panel requires 6192 LED lights, a special glass covering and a circuit board. That’s a lot of manufacturing.
The Solar Roadway promises to do a lot more than rebuild our economy through job creation. It will heat roadways to melt ice and snow, illuminate roads at night, carry cables for phone and internet service to homes, provide smart grid access for electric vehicles and deliver important messages to drivers through LED’s.
There seems to be one thing missing though — funding. The Solar Roadway website details the disarray that our current road system is in and notes that part of the reason we got to where we are is lack of funding. No doubt the Solar Roadway will be more expensive than the current inexpensive oil derived asphalt. So although it seems like a bright idea, it’s going to take a lot of cash money to bring this high-tech system to life.

Inhabitat

Barcelona Introduces LED Streetlights That Cut Energy Costs by 1/3

by Cameron Scott

If it weren’t already the case that no other city can hold a candle to Barcelona, it is now: the European city has begun using wireless LED street lamps — made by Spanish energy giant Endesa — that run on timers and motion detectors. LEDs aren’t cheap, but a new study from the University of Pittsburgh found that they offer the best green alternative for cities in a lifecycle analysis. Barcelona expects to see its municipal power bill decline by a third just from the timed LED lights.

Streetlights are low-hanging fruit, environmentally speaking. Their design tends to be clunky and they account for a massive chunk of city power bills, even though much of the time their light falls on empty streets. Design improvements and energy savers like motion detectors will also reduce the amount of light that beams skyward, which biologists increasingly say disrupts nocturnal wildlife. Like other fixtures designed to reduce light pollution, the Barcelona street lamps aim their light downward.