The Transition to LED Lighting  

The Energy Collective has a post on the transition to energy efficient LED lighting - The Transition to LED Lighting.

In a new paper (subs req'd) published as the cover article in the March edition of the Proceedings of the IEEE, the authors take a comprehensive look at technology, costs and policies influencing the adoption of light emitting diode, or LED, lighting. The 30-page (!) journal paper, authored by colleagues Inês L. Azevedo (A Sustainable Research contributor), M. Granger Morgan and Fritz Morgan is titled, The Transition to Solid State Lighting.

90% of U.S. residential lighting is provided by incandescent bulbs, which is bad news and good news. The bad news, the authors tell us, is that incandescent bulbs only convert between 0.2-2.6% of the electricity consumed into useful life. This inefficiency should be no surprise, as an incandescent is essentially a little fire enclosed in a bulb. The good news is that they are cheap and generally last less than a year before the bulb burns out. This means that unlike cars or buildings, replacing our "fleet" of residential light bulbs has a relatively short time-scale. But what do we replace with? This spring the NY Times discussed the promise of LEDs, but this week is reporting that the death of incandescents has been greatly exaggerated. The authors of this paper discuss the comparative advantages of solid-state lighting, or LEDs.

When talking about lighting, we need to get the terms right. System Efficacy is a measure of how much light is perceived by the human eye (lumens) vs. how much power you need to produce it (Watts). You want the most light you can get for the least amount of power. This is outlet-to-eye efficiency, so to speak, so it considers losses starting at the lighting ballast (the part at the base of CFL, for example), losses in the bulb itself, and then losses in whatever cover we put over it (e.g., the glass). The authors report a system efficacy in lumens per watt for the following bulbs: Incandescent (2-16 lm/W), Halogen (6-30 lm/W), Fluorescent Tube (16-90 lm/W), CFL (9-68 lm/W), HID (4-120 lm/W), and finally a white LED (18-170 lm/W). Translation: LEDs good, could get better.

The paper also presents method to evaluate costs from different lighting technologies, and in the middle of a technical paper they present a refreshing review of discounted utility models and economic theory, and give some insight into how we make (sometimes really bad) decisions about what technologies we buy. For instance, the paper reviews studies that estimate residential consumers apply implicit discount rates to energy efficient appliance purchases of up to 300%! This means they aren't willing to pay a little more up front for a more efficient appliance that will clearly save them money over time, unless that money saved is large enough to be seen from space. [N.B. My proposed solution to this, is a tax credit for credit card companies to offer a energy star credit card, with a fixed rate of 5%, that can only be used to purchase energy star products, but I digress.]

The paper continues through scenarios about U.S. lighting demand, and energy savings through LED adoption. They report: "A solid-state lighting adoption of 5%, 50%, and 99% in terms of lumen demand would provide cumulative savings between 2007 and 2015 from 20 to 50 TWh, from 125 to 340 TWh, and from 385 to 1030 TWh for the residential sector; and from 25 to 30 TWh, from 90 to 110 TWh, and from 430 to 525 TWh for the commercial sector, depending on the assumptions made about future lighting demand."

They go on to estimate that LEDs will be among the lowest cost options for of carbon mitigation (that's $/ton avoided): "According to our simulations, the cost-effectiveness of mature lighting technologies ranges from 4 to 28 $/ton CO2. Assuming a 10% discount rate, solid-state lighting cost-effectiveness for a utility ranges from 34 to 134 $/ton CO2 in 2008 and from 4 to 14 $/ton CO2 in 2015, making it among the more attractive investments available for large CO2 abatement by the electricity sector."