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Considerations for the prediction of trends in luminous efficacy of LED products

Panel: 9. Products, appliances, ICT

Authors:
Gillian Isoardi, Light Naturally, Australia
Steve Coyne, Light Naturally, Australia

Abstract

The transition to Light Emitting Diode (LED) based lighting products from traditional technologies is achieving significant energy savings. However with the rapid improvement in the efficacy of LED products, we observe a marked spread in the performance of LED products. To maintain the drive for the development and adoption of energy efficient products, a combination of push (mandatory MEPS) and pull (voluntary HEPS in the form of labels, subsidy schemes, government procurement) strategies and programs can be employed.

The International Energy Agency, Energy Efficient End-use Equipment, Solid State Lighting (IEA 4E SSL) Annex has developed quality and performance requirements with three different performance levels to address the needs of various programs and priorities for a country or region.

The 3 performance levels are designed to provide an indication of:

1) a Minimum Acceptable Performance level, above which most (70-80%) products perform,

2) a High Performance level, useful to demonstrate the level of performance required by established quality programs, where the top 20-30% of products are performing, and

3) a Current Highest Commercially Available level, achieved by the top ~5% of products.

Determining suitable luminous efficacy levels for adoption in future years requires extrapolation (i.e. trend prediction) based on historical product performance data. There are several types of product performance data available for this type of analysis. Ideally the most useful data would be representative of the entire market, capturing the true range in product quality within and across different regions. For the best accuracy, product data should correctly record product age and the claimed performance attribute (efficacy) would ideally be verified through testing.

For inclusion in this analysis, a product must have sufficiently descriptive product information to allow it to be classified into the appropriate category. It is desirable to have as much product data as possible, but this desire for high volume must be balanced by the need to ensure that analysed products are carefully and consistently classified according to their product category scopes.

In addition to these data priorities, it is important to consider the restrictions or requirements placed on products for inclusion in some data sources. For example, energy efficient product registers provide some of the highest volumes of LED product data available; however, such data tend to show truncated luminous efficacy range across their listed products, skewing overall efficacy data and making them less useful for establishing minimum acceptable performance trends.

These factors were taken into consideration in data selection, with 17,200 LED products drawn from the US Lighting Facts Database from 2010 to 2018 to form 7 cohesive, "like" groups of products for efficacy modelling: non-directional lamps (n=1,380), directional lamps (4,560), double-capped linear lamps (5,330), downlights (1,480), linear/troffer luminaires (2,820), high/low bay luminaires (750), roadway & outdoor luminaires (900). These data were analysed for best fit efficacy projections up to 2023 for each of the 3 performance levels of interest.

In order to demonstrate that this approach was consistent with more recent (up to 2020) data from other sources, more than 75,000 products from a range of other international data sources (focusing on verified test data) were used to validate the modelling across all product categories. This validation process showed that there were ample products achieving efficacies consistent with the projected performance levels, suggesting that they represented realistic product performance changes over time.

Finally, a case study highlights the impact of a voluntary incentive scheme where the periodic review of high-performance luminous efficacy requirements is shown to propel the performance of the scheme-registered LED products to exceed typical retail market levels.

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