Wilson discussed some of the hardware components that intelligent lights require and the importance of power control and efficiency in a successful intelligent-lighting network:
"Lighting represents one of the world's greatest opportunities for significant energy savings, as up to 25% of home-energy usage is from lighting. We all know the energy-savings potential of LED lighting in replacing the existing base of incandescent lights. We estimate that another 30% of savings can be gathered by applying [and combining] these LED lights with intelligent lighting: Use light when you really need light. With smart controls, you can do dimming, scenes, profiles, adjustments, monitoring, [and] preventive maintenance. [In addition] intelligent lighting enables participation in utilities' demand-response programs, resulting in reduced tariffs.
"Some of the key elements of an intelligent-lighting network are the switches, sensors, controllers, and the wirelessly enabled smart lamps themselves. If you want to have access to them through smartphones, tablets, and other Internet-connected devices, then you need to have some sort of gateway. I'll talk a little about what's going on inside that wirelessly enabled smart lamp because there is a price to pay in terms of power when you're putting all this smart technology inside a light bulb.
"One of the gotchas in smart lighting is now that you have the smart power supply, it must be constantly on and drawing power. Even when the switch is in the off position, the light must be listening for controller signals. Fortunately, intelligent light bulbs, which are often centrally positioned in every room, can make ideal network routers, but they do draw continuous amounts of power even when off, so standby power can impact system power efficiency.
"Standby power can vary dramatically based on power-supply topology. For example, a low-cost linear supply can consume as much as 3W; in a 13W LED you'll negate the power savings of using an LED lamp, so that's not a really smart way of doing it. … A better choice is a buck topology with about 10 mW of standby power. State of the art for a radio transceiver for the wireless portion is about 17 mA of current. The networking stack you choose has an impact, as well. David [Ewing] mentioned 6LoWPAN. I think the key is to get the code size small and then keep the RF-transceiver- and microcontroller-power needs as low as possible. Using a ‘mostly asleep' duty-cycle design where the transceiver and microcontroller don't have to be constantly on also helps cut down on standby power.
"As an example of how real this issue is, a 10W bulb on for four hours a day uses 40 Whr a day. If the standby power for the device is 1W ... it will consume about 20 Whr a day; 33% of the power is consumed in standby. At 100 mW, it falls to 2 Whr, or just 5% of the electricity bill at 100 mW standby power; NXP demonstrated at LightFair last May its 6LoWPAN chip set operating with a duty cycle of about 10% on and listening for control signals, resulting in a standby power of about 30 mW and reducing standby power to negligible amounts.
"Dimming control becomes much simpler when designing for smart lighting networks. Currently, LED lamps must be able to dim with existing TRIAC [triode-alternating-current] phase-cut dimmers, and including this circuitry in an LED lamp costs about 50 cents. In an intelligent-lighting system, users control dimming from a tablet, a smartphone, or a wireless device. Eliminating the TRIAC-dimmable circuitry will help offset the cost of including wireless circuitry and intelligence in LED lamps.
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