Anay Waghale, Pacific Northwest National Laboratory: Hello, everyone. My name is Anay Waghale, and this presentation is about the response of LED streetlights to 0-10V control signals.
0-10V control method was initially developed for fluorescent sources, and is still the most commonly used control method for LEDs. This is mainly because of its simplicity and low cost of implementation. However, there are multiple shortcomings, like its inability to reliably set light output to a known level, and unpredictable performance which results in failure to realize any potential energy or cost savings. In addition to all of this, there are multiple standards that define the same control method and all of these definitions are vague, and of course, vary from each other.
This research exposes the performance variation across commercially available streetlights, and the impact of a new ANSI C137.1 voluntary standard in reducing this variation. To answer these research questions, 21 LED streetlights were tested using a simple test setup as shown here.
Because of the extended definitions there are multiple implementations across manufacturers, which leads to performance variation across products, and in this case, across different make/model LED streetlights. It was noticed that most of these streetlights did not utilize the whole 0-10V control range and showed a deadband above 8V and below 1V. Also, not all of them dimmed down to the same power level, exceeded their rated power, as well as reached their maximum power at different control voltages.
To reduce this performance variation across products, ANSI C137.1 was recently published, which specifies targets for high control voltage as 8 or 9V and for low control voltage as 1V. This means that the standard requires a driver to reach its maximum power at 8 or 9V, and minimum power at 1V. However, the standard does not specify these maximum and minimum values and is left up to the manufacturer to decide. This results in product with different minimum powers as seen previously.
When the response of these 21 LED streetlights was compared to the standard requirements, nine out of 21 drivers were found to be non-compliant. There were three different requirements that these nine drivers failed to comply with. This shows that the manufacturers will have to change their product to comply with this ANSI C137.1 voluntary standard.
To quantify the impact of this new standard, if we look at the average power variation across all luminaires, it was around 31%, which is significantly high. This variation drops to 24% across the compliant products, showing the impact of the standard in reducing output radiation. 24% is still high and there is still scope to reduce this radiation further. If we divide the compliant group based on the high control voltage target, the variation across the 8V group drops to 16%, and the same across the 9V group drops to 12%.
The reason for this difference is mainly because the 8V group contains luminaires with minimum power level of 10% as well 30%, whereas the 9V group only contains luminaires with the minimum power level of 10%. This shows, if the standard specifies only one high control voltage target and also specifies the minimum power level, the variation can be reduced significantly.
So it appears that the new ANSI C137.1 standard will indeed have an impact on market available products, and will reduce some of the performance variation they have exhibited up until now. However, the new standard will not necessarily result in uniform or predictable performance due to its vague definitions. So end users might continue to be surprised that the light output from the different luminaires in the system is different at a given control signal, and will keep losing on any potential energy or cost savings.
I hope you liked this presentation. And if you have any questions, email us and we will be more than happy to answer them. Thank you so much for your time and have a great rest of your day.