LED Light for City Night

Nighttime commuters may notice a bluish glow coming from the ten pairs of street lights lighting their way. Mounted 40 feet above the traffic, similar to those found in stoplights and laser pointers, the lights are not bulbs but rows of LEDs.

“This is the first interstate highway to be lit with LED lighting,” said Kevin Orth, director of sales for Wisconsin-based Beta LED, which makes the lights. LEDs are coming to the streets of Eden Prairie, where officials are replacing the city’s old street lights, and already illuminate the parking lot of a Cub Foods store in St. Paul’s Phalen neighborhood, which last month became the second certified energy-efficient supermarket in the country.

For large projects like these, the long-run savings in energy and maintenance, as well as the environmental concerns, generally outweigh the short-run costs.

This growing use of LEDs by government and industry marks a move away from traditional incandescent bulbs and, more recently, the more-efficient fluorescent lights that have come on the market. Although LEDs cost more to manufacture than other lighting options, they consume a small fraction of the energy of even fluorescent bulbs and last 25 to 30 years.

Lighting still accounts for as much as 20 percent of electricity used around the world, so improving lighting technology by even a little bit can lead to great savings in energy and reductions in greenhouse gases.

How to Make an Old House into a Modern

This artical shows you how to push a 1920s house into a modern, low-carbon age. The last few touches – appliances and rare light bulbs.

After spending the past year reducing the home’s heating bills by adding stacks of insulation, the owner has now turned her attention to slashing her electricity needs. She buy electricity from Good Energy which is a 100% renewable electricity supplier, but she would like to reduce our dependence on it, as all electricity is expensive – green or not. She monitor her energy usage with weekly measurements taken directly from both the gas and electricity utility and currently the house consumes 8kWh of electricity every day.

As part of her drive to save eneergy, She has reviewed the efficiency of all of her electrical appliances. Fridge freezers are significant consumers of electricity in the average house because they are switched on 365 days a year. As she was old, she recently replaced it with an A-rated one to minimise energy usage. Their television is an old-fashioned boxy cathrode ray tube, which is quite energy-hungry, consuming 300 watts per hour when on. The plan – when she has the money – is to change it over to a LCD type. They’ll plan their purchase with a great site called Sust-It which you can use to determine the energy cost per year of new tellies and other products.

What else? Well, she changed most of our conventional light bulbs to energy-savers several years ago. That was easy with standard bulbs, so now she is replacing the more obscure ones.

The garage security floodlight was rated at an energy-guzzling 500 watts – the equivalent of around 50 standard energy-saving bulbs. Although it produced an instant bright light , it was repeatedly set off by animals wandering into the garden at night. So she found a low-energy bulb from B&Q which, although less than half as bright, consumes just 18 watts and reaches full brightness within a few seconds. B&Q now sells a better version using an incandescent bulb for instant bright white light, but after a few seconds the more efficient but slower compact fluorescent bulb takes over.

Continuing outside, our garden lights used to consume only 6 watts each, but having eight of them she was determined to replace them with a more efficient option. Compact fluorescent bulbs don’t exist for such a small wattage so an LED light was the obvious choice. She has now replaced each of them with a very bright 1 watt LED version which nicely lights up the path to the house. A timer ensures the overall energy consumption is minimised.

She has used LED technology inside too. Earlier in the year she bought several Deltech LED bulbs from ebulbshop.com and was very impressed with its brightness and warm-white colour. It matches the incandescent GU10 bulbs (one of the most common spotlight-style fittings) very well and most importantly it has the same physical size, so it fits in her bathroom ceiling’s recessed bulb-holders. These GU10 LED bulbs consume just 5 watts each but come close to the light output from their 50 watt incandescent equivalents. They won’t pay for themselves for more than 10 years because they’re so expensive up-front, so I justify the LEDs on the grounds that their carbon payback is immediate.

Salmon DNA LED Bulbs

It is reported that the latest LED breakthrough comes from the University of Connecticut, and it uses salmon DNA to create very long-lasting white LEDs (though they can be tuned to other colors). By now a lot of cool LED technology still needs to make its way from the lab to the store, it’s exciting to see that engineers are still finding new ways to squeeze more performance out of those semiconductor diodes.

Fluorescent dyes (two different ones, spaced between 2 and 10 nanometers from each other) are added to the DNA molecules, which are then spun into nanofibers. These are very durable because DNA is a particularly strong polymer (it has to be!) (they should last 50 times longer than acrylic, for example).

A LED emitting ultra-violet light is then coated with the DNA nanofibers: “When UV light is shined on the material, one dye absorbs the energy and produces blue light. If the other dye molecule is at the right distance, it will absorb part of that blue-light energy and emit orange light.” Using DNA has the benefit of orienting the dyes “in an optimum way for efficient [fluorescence energy transfer] to occur,” according to David Walt, a chemistry professor at Tufts University.

To tune the light quality, all you need to do is vary the ratios of dye. The light can be tuned from cool white to warm white, for example.

Unfortunately, numbers on how many lumens per watt these LEDs produce haven’t been released yet (though that might just be because they’re still improving them), so it’s not clear if the main benefit from these will be the longer life, or if the extra fine tuning will also mean better light quality than other white LED (like those that use quantum dots, for example), or if energy efficiency will also be superior. But it’s a new trick that will no doubt be useful. Maybe someday we’ll have a bit of DNA in our lights.