LED Lighting - An Introduction to Super Efficient Lighting

Introduction

LED lighting is the newest lighting innovation, offering lights that last for many years, use as little as one-tenth the energy of normal light bulbs, and contain no environmentally damaging mercury.  Because the technology is both new and different, many questions remain about how to best to use LEDs, what factors to consider when choosing an LED lamp, and what the fundamental product choices are.

Below are two illustrative LEDs.  The one on the left is and example of a bulb design, an HP-Globe 15, a 15 watt LED that produces as much light as an 85 watt incandescent.  The lamp on the right is and HP-10 Flood, which uses only 10 watts to put out as much light as a 50 watt incandescent lamp.

  

LED lighting refers to light-emitting diodes, a technology  originally developed by a British researcher in 1907 (1).  LEDs are semiconductors that emit light when a current is passed through them.  The challenge over the years has been two-fold:  first, the amount of light that LEDs emit has historically been very low, in fact, until recently, the light levels were too low for LEDs to be considered a replacement for standard lighting sources.  Secondly, the color emitted by the LEDs in the visible spectrum has been limited to very specific colors, beginning with red in 1962 followed by yellow and blue.  It has only been in recent years were a variety of colors have been developed, enabling the generation of useful white light, for example.  These innovations in light levels and colors have enabled LEDs to be adopted for use as light sources for illumination in consumer applications. 

Characteristics of LEDs

• Efficiency - LEDs are much more efficient than both compact fluorescent light bulbs and incandescent light bulbs.  For example, in a typical high use are in your home, a standard 100 watt incandescent light bulb may cost $23.36 to operate for a year, while a comparable compact fluorescent light bulb at 23 watts would cost $5.37 to operate for a year, and a comparable LED at 13 watts would cost $3.04 to operate for a year, saving 87% of your electricity costs!

• Life - A standard incandescent bulb may operate for only 750 hours, while a compact fluorescent operates and 10,0000 hours, and a comparable LED operates for 50,000 hours.   That basically means that when you buy an LED, you might have it with you for between twenty-five and fifty years.  If you use your LED for four hours per day, every day all year, the bulb will last for at least thirty-four years!  With such a long life, LEDs can be very useful in hard to reach locations where replacement is difficult or costly.  

• Beam Angle - LED lights are directional lights, meaning that the light is directed in a certain direction.  The most basic application for illuminating LEDs is as spot lights, given the directional or focused nature of the light output.  Consequently, when purchasing LEDs, they may have fewer lumens than a normal lamp, but the same amount of light may be directed to the work surface.  An LED light is usually multiple small LEDs that project a conical shaped light pattern.  In order to have the same dispersion as an incandescent light bulb, a frosted dome is placed over the end of the LED lamp.  This constrains the light output of the LED, but provides a more generally dispersed form of light.  Beam angles can range from 20 degrees up to 180 degrees.  

• Color - When selecting light bulbs of any type or design, it is important to be aware of your choices with respect to the color characteristics of the lamp.  Light bulbs use a color scale called kelvin, named after Lord Kelvin of Great Britain who developed "an absolute thermometric scale" in 184 equivalent to the scale of degrees celsius, except with the zero point being absolute zero, where all thermal energy of matter drops to zero.   This zero point is approximately equal to 460 degrees below zero on the Fahrenheit scale.   For lighting, the color scale typically runs from 2,500 to 7,000, with color rendition improving from the lower numbers up to the higher numbers.  Compact fluorescents, for example, range from 2,700 to 3,000 kelvin, corresponding to what is referred to as warm light.  Lamps with temperature ranges up to 3,500 kelvin have greater white light and can be good for reading lights.  As the color temperature goes up between 4,000 and 6,500, the light goes from white to blue.   These higher temperature levels are sometimes referred to as "daylight" colors.  

• Types - LED lights come in several basic types, including bulb lights, flood lights, light bars, and bi-pin bulbs.  What is important to note is that LEDs do not come in dimmable versions, although there are integrated lamp configurations which successively switch off individual diodes.  These types of lamps are used in flashlights and headlamps.  The light bar or strip light types can be good for under cabinets in kitchens, and can also be integrated into light fixtures for task lights used on working surfaces such as desks.  Generally LEDs are good for spot light applications, track lighting, and accent lighting.  

• Cost -  LEDs are generally expensive, but prices are coming down rapidly, and performance is improving rapidly.  Equivalent replacements for 100 watt light bulbs, for example, can cost between $80 and $120.  These prices are coming down rapidly as performance improves and manufacturing volumes increase.  A key capability that has improved in recent years is light output.  As the lumen levels of LEDs increase, the cost performance is improving.   

• Emissions - The emissions of LEDs is extremely low compared with other light sources.  In the examples alluded to earlier, the standard 100 watt incandescent bulb, operating for four hours per day, is responsible for close to 200 pounds of CO2 emitted per year.  The corresponding 13 watt LED is responsible for 25 pounds of CO2 emitted per year, a remarkable 87% drop in CO2 emissions per year.  

(1)  http://en.wikipedia.org/wiki/LED

Creating a Sustainable Transportation Future

Overview

The current transportation system in the United States is not sustainable from an energy, economic,  environmental or global equity perspective.  A wide range of alternatives are being pursued by governments, manufacturers, and consumers to develop meaningful alternatives from plug-hybrids, to ethanol, natural gas and hydrogen.  The use of liquid petroleum dominates the transportation sector due to its astoundingly favorable characteristics - high energy density, easy to transport and use, and reasonably cost effective relative to its utility.  Around the world, the issue of dependance on fossil fuels for transportation is compounded, with high market adoption rates with very little market penetration to date.  

Fundamentally, the position we are in today, with respect to demand frequently outpacing supply, increasingly distorted economic concentration in producing countries, increasing emissions, and increasing prices, will continue to represent the broad trend.  If we think that there is sufficient justification to develop alternative pathways today, the urgency will only increase.  

Energy Use for Transportation

In 2007, 68.3% of our petroleum use in the United States was used for transportation, amounting to 14.12 million barrels per day (mbpd) out of 20.68 mbpd total petroleum consumption in the United States.  Light vehicle consumption, basically the cars and trucks that we all drive, accounts for about 65.2% of the transportation energy consumed, or approximately 9.2 mbpd.  

In the United States, our transportation energy consumption is driven by our choices regarding modes of transportation, the fundamental efficiency of our vehicles, the miles we drive and how we drive with respect to efficiency.  Early in the previous century, the die was cast to facilitate the broad use of automobiles as the dominant mode of transportation in the United States.  Consequently, low oil prices are a cornerstone of the transportation infrastructure that we have developed in the United States.  

When compared to other countries in the world, the United States has some of the lowest oil prices, even considering the recent run up in prices.  Other countries apply high tax rates to  petroleum sales, effectively increasing retail rates significantly.  Based on data from March, 2008, we can see on the following chart that gasoline prices in the United States $3.44 per gallon are still less than half of the gasoline prices when compared to countries in the European Union. 

   

One of key questions for transportation energy is developing an understanding of switching behavior under conditions of high prices.  One of the facts that people may not remember is the significant reduction of approximately 25% in our national oil consumption over the period from 1978 through 1982.  This significant reduction resulted in a curtailment of national and international demand for oil, reducing oil prices for a prolonged period.  This demand reduction in the late seventies was due to consumers, governments and businesses and utilities instituting new policies and changing buying behaviors and driving habits to reduce oil consumption.     

This year, in 2008, as a result of high oil prices, consumers have been making changes in their purchases and behaviors geared to reducing oil demand, which is having an impact on both aggregate petroleum demand for the United States as well as impacting major United States automobile manufacturers.   In the chart below, from EIA data, we can see that petroleum use for the transportation sector is down year over year, averaging to a 1.4% reduction over the first five months of the year, with May representing a 2.3% reduction on a  year over year basis. 

The short term drop in petroleum consumption in the transportation sector can be attributed to a corresponding drop in vehicle miles driven, as calculated by U.S. Department of Transportation, and presented below.  Based on the first three months of the year, it appears that vehicle miles travelled were reduced by approximately 3.3% on a year of year basis.  

There has also been a marked shift in the types of vehicles that people are purchasing, shifting from trucks and SUVs to small efficient vehicles.

Emission Associated with Transportation

In 2003, transportation accounted for approximately 27% of greenhouse gas emissions in the United States.  As seen in the chart below, transportation is the fastest growing source of emissions in the country.

Each car in the United States, on average, emits about 1 pound of CO2 for each mile driven.  Consequently, if the average person drives 12,000 miles per year, that is equivalent to 12,000 pounds per year, or 6 tons per year.  Multiply this number times 220 million cars in the United States, resulting in approximately 1.3 billion tons per year of CO2 emissions from our cars. 

For the world, we can make some assumptions about the average efficiency (28 mpg) and miles driven (8,000 miles per car) and the number of non-US cars (38 million) which results in 1.2 billion tons of CO2 emissions per year, and a total due to light vehicles in the world of 2.5 trillion tons per year.  The expectation is that the number of vehicles in the world will double in the next 30 years, which would result in emissions of 5 trillion tons o CO2 per year.  If it is assumed that efficiency will improve by 50%,  our global transportation emissions associated with light vehicles will be 3.2 trillion tons per year, a significant increase.   

Transportation is a vexing problem with regards to oil demand and emissions, as the utility of petroleum-based individual transportation is extremely high.  As economies around the world develop, such as China and India, the global demand for vehicles will continue to grow, as will the fundamental demand for petroleum.  

Solutions

The solutions for addressing the economic and emissions issues associated with petroleum-based transportation are many and varied.  There are three fundamental directions - (1)  Improve efficiency of gasoline and diesel-based vehicles; (2) Develop alternative fuel vehicles; and (3) Develop alternative transportation options.  These solutions will be explored in future blogs.