Jan 102012

In the current issue of Electrical Wholesaling, Jim Lucy, the chief Editor, comments on a side-by-side comparison of Fluorescent and LEDs he saw at Lowes. I’m not surprised. LEDs often have an odd color cast. LEDs are now as efficient as Fluorescents but they are still more money. LEDs do have their uses. Often they are ideal in low wattage situations like decorative lighting. I’m sure they will get better and cheap as time goes on.

But what really galled me is that the LED on display was emitting a ghoulish blue-white light that could only appeal to someone trying to duplicate the lighting in a 1950s-era Soviet interrogation room. By any measure, this display did much more harm than good to the admirable cause of LED lighting, particularly in a setting where homeowners and other potential retail customers are probably getting their first look at LEDs.

Nov 222011

Recently I fielded a call from an equipment engineer in Minneapolis regarding a HVAC modeling project. He asked about my experience working with ‘Typical Meteorological Year” (TMY) data sets. I’ve modeled a number of Heating, Cooling and Ventilation jobs were I needed the fine detail that TMY data sets provide. I told him the problem I had was using a spreadsheet. I found 8760 lines made for some unwieldy spreadsheets. Instead I put the TMY data in a database and worked my models using a hybrid of database calculations and spreadsheet calculations. He asked where to get the data. It can be found from a number of different sources online. I have been using TMY2 and now TMY3 data sets* from the National Renewable Energy Laboratory (NREL), other sources include…

  • TRY – ASHRAE’s Test Reference Year
  • WYEC – Weather Year for Energy Calculations
  • IWEC – International Weather for Energy Calculations
  • NCDC – National Climatic Data Center
  • TMY – Typical Meteorological Year

According to D.B. Crawley’s paper, “Which weather data should you use for energy simulations of commercial buildings?“, either WYEC nor TMY will work fine. These data sets are pretty good, however you need to keep in mind- they fail at the temperature extremes. The data sets are designed to weed out extreme tempertures in order to create smoother data sets. This can be problematic if you’re also using the simulation to size your equipment. Having said that, these TMY based models will be far more accurately modelling energy usage than using bin hours. They are also better when running what-if scenarios. In order to truly model a building for energy use, particularly where humidity control comes into play it is essential to model the energy use for each hour in a typical year- all 8760 data points.

Detailed hour-by-hour modeling using hourly weather data sets has become commonplace in the evaluation of design alternatives and the design of HVAC systems for larger buildings. For residential and small commercial buildings, calculating design loads based on high and low design temperature is still common practice. The economic issue is when the added cost of the more involved hour-by-hour modeling exercise can be expected to be justified by helping to guide the selection of equipment that provides significantly better part-load performance, resulting in tangible benefits of lower total annual energy cost and better comfort control in the building.-December 2010 ASHRAE Journal.

Other uses of TMY data sets are to adjust set-points based on outdoor temperature to control early morning pre-cooling. Both to take advantage of Lower temperatures and reduced peak demand rates. Building mass can also be used for energy storage. Off-peak heating and night cooling can be based on TMY modeling; shifting HVAC demands to off-peak hours and lower energy rates.

Some of this predictive control is finding its way down to the residential market with smart thermostats. I predict we’ll be seeing more of these smart thermostats… “A trial in 2000 households by Oncor Utilities in Texas resulted in heating and air-conditioning power cuts of 20% to 30% and annual savings up to $400. It also achieved complete AC turnoff at peak hours due to pre-cooling. These examples indicate that approximately 10% of energy to condition buildings can be potentially be saved by the use of control algorithms using forecaster weather conditions.”

*Note: The TMY3s are data sets of hourly values of solar radiation and meteorological elements for a 1-year period. Their intended use is for computer simulations of solar energy conversion systems and building systems to facilitate performance comparisons of different system types, configurations, and locations in the United States and its territories. Because they represent typical rather than extreme conditions, they are not suited for designing systems to meet the worst-case conditions occurring at a location. -NREL

May 102010

There is some concert that Compact Fluorescent Lamps (CFL) are not safe. In the early days there were issues with end of life and using the wrong CFL in the wrong application. Recently Underwriters Laboratories (UL) looked  at the CFL. They found, “CFLs do not pose any fire or shock hazard when used in a light fixture, controller, or switch that traditionally has been used for an incandescent source.” –May 2010 AL

The study examined CFL substitution in a variety of fixture types and found that even a CFL with the highest heat output still emits less heat than a 40W incandescent bulb. UL also looked at a lamp’s end-of-life characteristics. This is an area of particular concern for consumers, since earlier generations of CFL products have been rumored to make popping sounds or produce smoke when installed in an incandescent socket. The study also explored what happens when CFLs are used in conjunction with lighting controls such as motion detectors, wireless controls, and dimmers. No safety issues were unearthed here, but the test did indicate that there were issues such as flashing, flickering, poor light output, and reduced lamp life that might impact consumer satisfaction with performance. UL is quick to note that a CFL’s lifespan will be reduced substantially when installed in fixtures where switches are turned off and on frequently.

I’d like to add, that it is bad idea to a regular CFL on a dimmer. It may not explode but it will probably fail instantly. If you have a dimmer on the circuit and you want to use Compact Fluorescent Lamps, either removed the dimmer or use a dimming CFL. TCP has some nice dimming CFLs.

Many people are concerned by the mercury that CFLs contain. But what they fail to realize is the leading source of mercury emissions in the United States is from coal-fired power plants. And where CFLs can be recycled, the mercury from coal is going right into the atmosphere. I invite you to read all “25 Truths About Green” in the Fortune April 2010 Fortune magazine issue.

Considering that CFLs consume up to 75% less electricity than traditional light bulbs, using them decreases the mercury in the atmosphere. According to Energy Star, a 60-watt incandescent bulb adds 5.8 milligrams of mercury into the environment over its lifetime, vs. 1.8 milligrams for a comparable CFL.
Fortune April 2010

Aside: if you want to see dangerous Fluorescents check out the photo by Craig Cutler. Hot wires running to bare lamp sockets on a paper backdrop.

Jan 102010

Since I started selling lighting systems in 1991, I’ve been interested in light: quantity, quality, and efficiency. Of these three quality is the hardest to quantitize. We have been stuck with the Color Rendering Index (CRI) since 1964 when the Commission Internationale de l’Eclairage (CIE) came up with the idea of comparing each lamp to an ideal source. What many didn’t realize is this idealized source isn’t the same for every lamp. This makes CRI readings of limited use. Jeff Robins writing for Architectural Lighting (January 2010) reports on a new standard being developed by the National Institute of Standards and Technology (NIST). The NIST is trying to overcome the limitation of 14 pigment samples and the way the human sees light- it varies with the illumination level and color temperature.

Since 2006, the National Institute of Standards and Technology (NIST) has been developing a new metric, the color quality scale (CQS), that determines color performance using a method different from the CRI. When completed, the NIST will propose it as the new international standard. A different color space is used, and a new set of 15 reflective color samples, highly saturated and taken from the Munsell color system, replaces the 14 CRI samples and defines the difference between the test lamp and its reference. The NIST claims this should overcome hue and saturation shifts left out of the CRI calculation. This penalizes lamps of extreme CCTs, which frequently exhibit poor color quality. In the end, what will be familiar to users of the CRI is the CQS span, which will range from zero to 100. – (The Color Rendering Debate)

Side note:
This article also talks about the history of lighting as it relates to the CIE and the development of the CRI standard.

The CIE did not, however, solve the problem of color rendering. At the time, the issue was a small one. Remember, this was 1931; the lighting industry was dominated by the incandescent lamp, and color rendering had not yet been identified as an issue. The first lamp source other than incandescent, the mercury vapor lamp, was not available commercially until 1933. Fluorescent (1) and sodium discharge lamps(2) wouldn’t follow until later that decade, and metal halide wouldn’t come along until the late 1950s.

From the 1930s to the early 1960s, lamp quality improved significantly, especially in products that featured fluorescents, which, because of their lumen efficiency and reduced energy needs, became the lamp of choice for most commercial interior applications. The retail market was particularly keen to use the most energy-efficient means to light its products in an attractive manner.

  1. Albert W. Hull of GE’s Schenectady Research Laboratory filed for a patent on this invention in 1927, which was issued in 1931.Sales of “fluorescent lumiline lamps” commenced in 1938. By 1951 more light was produced in the United States by fluorescent lamps than by incandescent lamps. -excerpts from Wikipedia
  2. General Electric’s History of Light: Timeline

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Nov 302009

Jim Benya Looks At Basic LED Circuits in the Fall 2009 LED edition of Architectural Lighting. Benya points out LEDs are fussy about power and heat. LEDs operate on low voltage DC power and require a Transformer, Voltage Regulator, and Driver in order to function in our 120/277 volt world. The Transformer converts line power to 24 volt DC current. The Voltage Regulator keeps the Voltage constant and the Driver keeps the current constant. Any changes in the current or voltage can cause the LEDs to fail.

Once converted to low-voltage DC, power then passes through the LED to generate light. But as with a fluorescent lamp, there must first be a circuit that regulates the amount of energy—or the lamp will blow up. For a fluorescent lamp this circuit is called a ballast; for solid-state lighting it is called a driver. The typical contemporary white LED is designed to operate at either 0.35A, 0.70A, or 1A depending on watts, brand, and model. It is the driver’s job to regulate the DC power for the specific LED. An added complication is that seldom in lighting is one LED enough, and it is common to have several LEDs mounted and wired together. For example, a basic downlight might employ 20 or more 0.25W or 0.5W LEDs.

Drivers vary from simple resistors to integrated circuits that precisely control the diode itself. Add Dimming to fixture and the circuit becomes even more complex. Voltage can not be cut to the LED so the circuit has to vary the ratio of on/off cycles per second to achieve the effect of dimming. If you wish to control the color of your LED lighting system you add either RGB (Red, Green, Blue) LEDs to your dimming driver or RGBA (Red, Green, Blue, Amber) LEDs to your dimming driver and balance the color by varying the dimming to each LED.

Benya points out, the industry has no standards for Drivers, “We need standards in solid-state lighting that go well beyond the lumen measurement, efficacy, and life testing that have dominated solid-state lighting discussions to date. For instance, due to their poor 70 percent efficiency, drivers are often avoided when the energy efficiency of solid-state lighting is discussed.. As it is, LEDs have already developed a reputation for failing to meet rated performance and life.”

The good news is the industry went through similar troubles with the introduction of T8 fluorescent lamps and electronic ballasts. It is just a question of time before the issues of LEDs get sorted out.

Contant-Current Circuit

120v AC --> 24V DC Transformer --> Driver --> LED - LED - LED -->

Constant-Voltage Circuit

120v AC --> 24V DC Transformer --> Voltage Regulator --> Driver --> LED
                                                     --> Driver --> LED
                                                     --> Driver --> LED
Oct 092009

In the August 2009 issue of IEEE Spectrum, Richard Stevenson writes about a problem specific to LEDs known as droop.

Blue LEDs are those used to produce white light. Once the diode’s power level reaches an output sufficient for general lighting applications, the efficiency of the LED declines significantly- requiring more power to maintain a usable light level. Until the scientists and engineers understand this problem it may be difficult to overcome- at least in the near term.

The LED’s Dark Secret has a detailed explanation on LED Droop. I found the graphs helpful and the article also helps explain how LEDs work.

Sep 302009

We have been getting some interest in LED Lighting recently. LED is a new technology that is finding its way into more lighting products. LED lighting has many good features, but for now efficiency is not one of them. For example TCP has just released a LED lamp. This TCP bulb is one of the best LED I’ve seen, but it only puts out 35 Lumens per Watt. Whereas a Compact Fluorescent will put out 55 lpw, a Standard T8 lamp will pump out 75 lpw, and a high performance T8 lamp almost 100 Lumens per Watt!

LEDs do have many advantages.

  1. Although 35 lpw is not much compared to a fluorescent it is an improvement over incandescent bulbs. A 2.6 watt LED replaces a 15 watt incandescent.
  2. The LED bulb last a long time (25,000 hours) so it is a good application where maintenance is difficult like a chandelier
  3. The LEDs are directional, this makes for a good spot lighting, but a poor area lighting.
  4. The LED is vibration resistant. They work well in ceiling fans. Our TCP brand LED lamps are outdoor rated and work well in cold locations.
  5. The TCP LEDs are dimmable and look pretty good with a CRI of 80. They look much better than some LEDs, which have weird color casts.

If you’re interested in what technologies are currently hot check out “Lighting’s Workhorses” by Jim Benya in Architectural Lighting. Pay special attention to the graph. It shows which lamp technologies are efficient and which are not. Effective Concepts has a good selection of all the lighting listed in the article: Tungsten, Halogen, Metal Halide, Ceramic Metal Halide, Fluorescent (Cold Cathode, PLs, Biax, Induction, T8, T5s, etc), and even LED lamps.

Aug 042009

The House of Representatives voted on the American Clean Energy & Security Act of 2009. I haven’t read the bill, and I doubt our congressmen have either, but it the idea that you can just pass a bill and magically our county’s energy problems are solved is very naive. Furthermore the efficiency targets of the bill are unrealistic even if they are a good idea. What really makes me mad is- efficiency is its own reward. If these ASHRAE 90.1 reductions were so easy to obtain everyone would be doing it for the cost savings. The fact that few are speaks volumes. The few that are, are using government sponsored utility rebates or mandated government regulations. It is never a good idea for the government to interfere with the market, especially when the outcome is so questionable. I am happy to see I’m not the only one who things so. In the August edition of Engineered Systems Magazine (page 8), they polled readers on the bill and the outcome wasn’t good. These are professionals who love energy efficient solutions, so you better believe they have more insight than congressmen who voted on this bill, or the green lobbyists who probably wrote.

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