Tuesday, March 31, 2009
CFLs, mercury and coal emissions
Yes, there is mercury in CFLs (typically less than 5mg), and yes, they need to be recycled correctly to ensure that the mercury (and electronic components) stay out of landfills. The thing is, the benefits of using CFLs and the associated reduction in mercury emissions far outweigh any issues associated with the mercury in a CFL.
So why do CFLs contain mercury? All fluorescent lamps contain mercury (compact fluorescents as well as conventional straight tubes). The mercury is excited by an electrical current which causes the mercury to emit ultraviolet light. The ultraviolet light stimulates phosphor in the tube which produces visible light. Interestingly enough normal fluorescent tubes have escaped the mercury stigma even though they can contain more mercury that a CFL.
What does coal have to do with it? The burning of coal to produce energy is one of the largest sources of mercury from human activity (in South Africa 80% of our energy comes from coal). This mercury enters the atmosphere and eventually lands in our water systems. Mercury entering into aquatic systems can be transformed by microbial action into methylmecury which bioaccumulates in the food chain.
Incandescent bulbs release more mercury into the environment than CFLs. When you take mercury emissions from coal into accout it turns out that a normal incandescent bulb results in more mercury being released into the environment than a CFL, even when a CFL is disposed into a landfill rather than properly recycled. The US EPA estimates that 1.8mg of mercury enters the environment from a dumped CFL while the use of an incandescent bulb results in 5.8mg (for 8000 hours of use). See the Energy Star's mercury fact sheet for their assumptions.
What about CFL breakages in the home? Breakages need to be dealt with carefully, but do not pose a serious hazard. Ventilate and have any people or pets leave the room. Follow the recommended clean–up guidelines in the EPA mercury fact sheet. There is an old and false story about expensive clean–up procedures which came about due to a misunderstanding – snopes.com has the full history of that story, which makes for interesting reading.
What do we need to do? Switch to CFL or LED bulbs wherever and as soon as possible. This reduces both energy consumption and mercury emissions which is good for our well–being. Consider LEDs where suitable – they contain no mercury and have a longer life span than CFLs (although they only available in certain light formats, provide a different type of light, and you need to compare their efficiency to CFLs). Correctly dispose of your CFLs (and LEDs) for recycling, as this keeps the mercury out of the landfills and allows it to be reused in new lights.
Please share this, blog about it, write newspaper articles, tweet (and retweet) it, stumble it, tell your friends, and explain it to anyone who does not know that using CFLs will actually reduce your exposure to mercury. CFLs help us to reduce energy consumption and keep our environment clean – let the world know.
More resources:
[1] "Global Atmospheric Mercury Assessment: Sources, Emissions and Transport," UNEP
[2] UNEP mercury programme
Image courtesy of Energy Star.
Tuesday, March 17, 2009
Turn off the lights: Earth Hour 2009
When was the last time that you enjoyed the wonder of a night time sky? I have fond memories of family holidays to Jeffery's Bay, and one of the things that stands out clearly in my mind is the beauty of the night sky from the beach near the house we stayed in. The richness and depth of the starry night seemed to suck you into itself.When I look up from my home now all that I can see is a few of the brightest constellations while the rest is hidden by the haze of city lights. We have lost our night sky and we do not even know what the implications of that are (here are some). I was reminded of this by a photo essay on light pollution. The last line of the essay is particularly poignant: For all the benefits of artificial light, "we shouldn't pretend that nothing is lost."
On 28 March at 20h30 the WWF is asking us to turn out the lights for one hour as a vote for Earth and a vote against climate change. This global action will be presented to leaders at the Global Climate Change Conference in Copenhagen.
This is not a vote against climate change, this is an action to win back some of what we have lost. This is an opportunity to start reclaiming our night sky. This is the chance to turn off not only your lights, but your TV, computer, cellphone and any other distraction and to spend an hour with the people you love – connecting and enjoying your humanity. This is a vote for a happier, cleaner and healthier world.
Sign up on the South African or International Earth Hour websites.
Image courtesty of Steve Jurvetson, licensed under a Creative Commons license.
Tuesday, August 12, 2008
9 simple ways to design for lower energy use
There are lots of really complicated and difficult ways to design for lower energy consumption, but most of us do not have the time or budget to do them. Yet, there are many really simple ways to reduce energy consumption which only take a few moments of our time. It is largely a matter of being conscience of the decisions we are making.Here are a few ideas:
- Use larger resistors
Does that pull–up/down resistor really have to be 1k? Could it be 10k or more? There are always engineering trade–offs to be made. Increasing resistor size increases noise and can make your design more susceptible to EMI, but there are many cases where resistor values can be increased with no discernable effect. Think about this, at 3.3V a 1k resistor will burn up 11mW, change that to 10k and the power consumption drops to 1mW. Your signal line should be in the correct default state (high for a pull–up and low for a pull–down) to ensure no energy is being spuriously expended.
- Turn off unnecessary LEDs
We (I) often use LEDs for debugging purposes, such as internally on an enclosed board. It helps us get some visual information about the system while debugging. Did you remember to turn those off in your release version? LEDs can consume a significant amount of power (1.5V @ 10mA = 15mW) which adds up for each LED that is needlessly left on.
- Dim or blink required LEDs
LEDs that provide visual information to the user can be dimmed or blinked to reduce power consumption. Try to determine whether those LEDs are really necessary in the first place – are there other indicators which are providing the same information? A laptop typically has a power LED and a screen which both provide feedback that it is on, while cellphones have no power indicator other than the screen. Does the laptop really need the power LED to be on all the time? What if it was only on when the screen was turned off, or flashing while in sleep mode? What if the battery indicator flashed when the laptop was off and the battery was full instead of being permanently on? How else can you convey the same information?
- Put microprocessors to sleep
Microprocessors are often waiting for an event such as a timer or communications interrupt. It is normally a simple task to put a device to sleep while it is idle. Some simple code can reduce the power consumption (and extend the battery life) of your device.
- Turn off unnecessary peripherals
Microprocessors usually have a number of peripherals which are either not used, or not used all the time. If unused peripherals are clocked that means that energy is being banished to heat just to clock something that is idle. Not all devices support this, but more and more are coming out with these features (such as the Luminary Micro range).
- Use low power components
Duh! That may seem obvious, but take some time to look at the quiescent current of the components you choose when designing. Faster components (like high speed op–amps) typically require more power when idle, while slower components require less. Consider using a slower op amp or lower power transceiver.
- Use a higher bus voltage
When you are running long wires (e.g. power bus around a warehouse) use the highest voltage that is practical. This will help reduce power loss due to copper losses. It also means you can use thinner cable, or run more units from a single cable (if cable current is a limiting factor).
- Use a lower bus voltage
Have you considered using a lower system voltage (e.g. 1.8V instead of 3.3V)? The limiting factor is often peripherals which require certain voltages, but you can consider other peripherals or use level translators. There are a lot of trade–offs to consider here, so use your engineering wisdom to come up with the best solution.
- Consider latching relays
Normal relays require a continuous current flow to keep them in the on position, while latching relays only require a short pulse to switch from one position to the next. You will have to consider cost and a small amount of extra circuitry, but these are particularly valuable where there are power supply limitations.
Photo courtesy of Windell H. Oskay, www.evilmadscientist.com
Tuesday, June 10, 2008
Leaving the lights on
I am an advocate of making sure that every device consumes as little power as possible at all times. Indicator lights should be off, processors should be sleeping as much as possible, and generally the device should just be optimised to use as little power as possible.I may have to rethink that....at least a little bit.
Dan Lockton has a brilliant blog, Architectures of Control, where he discusses how things are designed to result in a certain action (or lack of action) – or as he calls it, design with intent.
There are two devices in my home which have helped me to reconsider turning off all the lights, my DVD player and my laptop. Each has its own subtle "architecture of control" whether intentional or not.
Our DVD player has (to me) the most irritating standby light that I have ever seen on any device. When on, the light is constantly illuminated, but when in standby the light flashes continuously (at a slow rate). This drives me mad, but results in an interesting action – it causes me to turn it off at the plug when I am not using it (which is most of the time). Suddenly one little flashing light has resulted in more energy saving than having no light.
My laptop has a similar "feature." When it is powered down the battery indicator remains on (green if full, flashing yellow if charging). This used to bother me, and I thought, "Why not just leave the light off when the battery is charged?" My wife's laptop is like that, the battery indicator only flashes if it is charging, once charged it turns off.That is all good, except my laptop communicates to me that it is plugged in and consuming standby power when it is not in use. When I unplug it from the wall socket, then the battery indicator goes off – I save the standby power of both the power brick and the laptop.
There is one problem with this, it only works on people who care. If I did not care about saving energy, then I would just leave the laptop plugged in and the DVD player on. That means that you have to consider how your users will handle this kind of subtle feedback and determine whether turning the light off, or encouraging unplugging results in more energy savings.
Sometimes the most obvious design decisions may not be the ones which result in the greatest energy saving. Keep designing for low energy consumption and also keep your mind open to new possibilities.
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About this blog
I'm Duncan Drennan and this blog is about spreading ideas regarding engineering, our environment and creating a better world. You can also follow me on Google Reader.
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