Stand-by of “smart lamps” can be larger than their energy use for lighting

(eceee-news, 6 Sep 2016) “Smart” lamps combine technology breakthroughs in wireless communications with light emitting diodes (LEDs) to provide many exciting consumer benefits. However, the standby energy use of “smart lamps” can be larger than the energy used for providing lighting, according to a new report from the IEA 4E Solid State Lighting Annex issued today.

Smart lamps are an exciting new family of products which provide an opportunity for the consumer to benefit from smart services, better product quality and energy savings. Combining wireless communication, intelligent controls and light emitting diodes (LEDs), these lamps offer end-users features like colour tuning, dimming, changing lighting scenes, remote control, motion sensing control, daylight control and other features. But these features require energy even when the lamps are not providing light, but are instead waiting for a wireless instruction from a smartphone or remote control unit.

Policy makers concerned over lost savings

“Policy-makers who are looking at lighting products are concerned that these ‘smart’ lamps may end up creating new, high levels of standby power consumption in households.” said Dr. Peter Bennich, chairman of the SSL Annex’s Management Committee and representative of the Swedish Energy Agency, one of the Annex’s member countries. “We are concerned that these ‘smart’ features will offset some of the energy-efficiency gains from switching to LED technology.”

In order to better understand smart lighting and provide policy guidance for governments, the IEA 4E SSL Annex has launched a study on the energy performance of smart lighting. Today’s report offers the initial findings from this body of work.

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Tests conducted on a limited number of smart wireless LED lamps reveal that these products can have substantial standby power use – which, depending on hours of use, can even be higher than the energy consumed when the light is switched on.  These test results are similar to experiences with standby consumption for other products where manufacturers initially focused on new features before turning their attention to reducing the standby power consumption. For some of the lamps, manufacturers also provide a gateway (with its own energy consumption) for wireless communication between the lamps and other devices using protocols such as Zigbee, Z-wave or 6LoWPAN.

Large variations in stand-by energy indicate potential for improvement

When the lamp is not emitting light, the power is still connected as the lamp switches to a standby mode waiting for a signal from the end-user to switch-on again or the lamps may in commercial buildings also serve as part of a local wireless network, in a more active energy consuming mode. This means that the lamps are consuming energy even when they are not emitting light. This standby power consumption varies widely, from 0.15 to 2.70 W – indicating that design improvements or shift of protocol to reduce standing losses are possible.

Domestic light sources in IEA 4E SSL Annex member countries (Australia, Denmark, France, Korea, Sweden, the United Kingdom, United States and China), as well as in many other countries, typically operate 1-2 hours per day.  The smart lamps producing 200 to 1000 lumens of light tested in this project had an average standby energy consumption representing 51 % of the total daily energy consumption when these lamps are operated one hour per day. That corresponds to an overall efficacy of 9 to 51 lumens per watt, meaning some smart lamps had the equivalent performance of incandescent lamps. If the lamps are switched on for two hours per day, standby energy represented 35 % and the efficacy is approximately 16 to 64 lumens per watt, much lower than the non-smart LED lamps already on the market today.

Figure 1. Annual energy consumption for 27 smart lamps models in operation 1 hour/day (click to enlarge)

In addition to the standby consumption in the smart lamps, many systems also use a wireless gateway to facilitate communication with smart lamps in a given space. This gateway, which adds additional energy consumption of the size 1–2W, can typically accommodate up to 50 smart lamps. In raising awareness on this important topic, the SSL Annex hopes that manufacturers will be encouraged to make design improvements that lower the standby power consumption associated with smart lighting.

Lack of interoperability and cross-platform connectivity

“We are also also concerned about the lack of interoperability between different manufacturers’ lighting products”, said Casper Kofod, the report’s main author. “This could represent a barrier for large scale use of smart lighting particularly in residential situations, the report claims. The products being developed, including smart lamps, gateways, luminaires, controls, meters and management systems (software) tend to rely on proprietary hardware and software. In the home, smart lamp communication is performed by a number of wireless protocols in case different products are used. However, even where communication uses the same protocol for different products, the user may still have to use different software applications (apps) to control each product. This lack of interoperability may result in the user being restricted to purchasing all products from a single manufacturer.”

“In the future, there might be dozens of wirelessly controlled lamps in a single home, which taken together could result in high standby power losses”, Mr Kofod adds. “Therefore, the hope is to raise attention to the standby usage, so that design improvements can be made to the circuits that will lower smart lighting standby power. Indeed, the study found some lamps already operate with only 0.17–0.25W standby power while others have up to ten times higher power use, so design improvements are certainly possible.”

The market potential of smart lighting is extensive, once the platform enabling functionality has been established. These smart lighting products can also be used in other applications such as museums, exhibition halls, shopping centres and supermarkets where the lamps could be used as WiFi or LiFi nodes to help consumers with smart phones to navigate a building or find products in a store. For example, the interaction between the smart lights and smart phones could activate visual and aural information for self-guided museum tours or detailed product information in a store. The opportunities and applications are virtually limitless; and it is for this reason the SSL Annex feels it is critically important to study standby power consumption.

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