RTF analysts developed estimates of per unit technical potential for demand response in new, efficient non-residential lighting systems. The “units” considered here are building lighting load at a given time, and the potential is described as a percentage of this. Therefore, the demand response technical potential varies over time with the lighting load. The type of demand response considered for this analysis, by request of Council staff, was a one hour event.
Technical potential for this technology is constrained by occupant satisfaction and safety, and is reduced as efforts to minimize non-event lighting loads (e.g, proper sizing, trimming, and occupancy and daylighting controls) are increased.
Potential was estimated based on a literature review and interviews with subject matter experts. The intent of these exercises was to (1) identify what space-use types are amenable to lighting demand response and (2) what levels of lighting output and lighting power reductions could be implemented in these spaces.
RTF Presentation Commercial Lighting Controls DR Workbook DR Subcommittee Presentation DR Subcommittee Notes
Findings
The RTF analysts did not identify any large evaluations of DR lighting programs, but did identify numerous case studies and laboratory studies on the topic. The studies primarily addressed lighting in office and retail spaces. One study examined a variety of college campus buildings. In large buildings, office and retail spaces are most promising for demand response because they tend to be relatively large amounts of homogenous lighting load that can be dimmed to some extent without concerns over compromise to safety or productivity.
Limitations
One challenge with applying the findings of the studies to a potential estimate is that most of the studies found were conducted ten or more years ago, which suggests significant differences between the lighting systems studied and those of interest for this demand response potential estimate. The studies were conducted before solid state lighting (including high-end trim capabilities) was the predominant efficient lighting technology and when daylighting and occupancy controls were less common. Some of these studies were applied to lighting systems with some of these features, other studies were on fixtures without these features, or on fixtures with unspecified characteristics.
Across the studies, lighting reductions in office spaces were typically in the range of 15% to 50%, and in retail spaces from 25% to 50%. It is unclear from these studies whether greater reductions could have been achieved.
The RTF analysts did not find studies on newer lighting systems. They assumed that the findings from the older studies, on a percentage basis, would be applicable to newer lighting systems, but that the new lighting systems would draw significantly less power – and provide less demand response potential - in absolute terms.
Takeaways
Based on these findings, the RTF analysts proposed estimates of 25% for office space types and 35% for retail space types.
The 2014 Commercial Building Stock Assessment (CBSA) lighting inventory was used to determine the distribution of space types within each building type. Each space type was categorized as similar to an office space, similar to a retail space, or neither. Demand response potentials of 25%, 35%, and 0%, respectively, were applied to these spaces, and a floor-space weighted average of the potentials was calculated. This average is considered the building-level lighting load reduction percentage for each building type in the CBSA.
Expert Opinions
To support the research, RTF analysts discussed this DR mechanism with DR program implementers, lighting engineers, the author of a statewide lighting DR potential study, and the RTF Demand Response Subcommittee. These discussions validated the focus on office and retail spaces but also revealed program skepticism of the practical DR potential for commercial lighting.
DR program implementers did not see much participation from lighting loads currently or interest in them going forward. Typically, HVAC is a larger opportunity in a building, is simpler to control, and temporary HVAC reductions are noticed less than lighting reductions. As lighting systems become more efficient, and regularly dimmed to low levels in daylit and unoccupied times, the opportunity for demand response is reduced.
RTF Decision
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