Ongoing health and wellness research supports the use of advanced LED lighting systems with networked sensors and controls employing circadian lighting with dynamic spectral and illumination levels. These systems potentially provide several benefits to owners and occupants: better sleep patterns, increased productivity, and feeling significantly more vital, energetic and alert. An ancillary benefit, and a likely motivating force for electric utility programs, is the potential for added demand response (DR) in conventional terms of load curtailment, plus local grid stability capabilities associated with these optimized systems.
With grid modernization and rapid renewables adoption, grid variability is increasingly an issue. Grid operators are bearing the expense of keeping generators on standby to handle these highly variable generation assets. LED lighting DR is a great grid resource for dealing with this high variability. Voltage and frequency regulation, changing every second, can be addressed by shimmy: lighting can change its energy consumption second-by-second.
Emboldening this premise is LED lighting systems’ inherent capability to be readily controlled without sacrificing performance.
Utilities possessing a stock of DR-enabled buildings with responsive loads are able to deal with grid variability locally, rather than employing power plants hundreds of miles away. Buildings can adjust their lighting systems up or down to deal with different grid needs. As we can see in the “waterfall” diagrams below, DR-enabled lighting systems can provide significant value depending upon the occupancy type and local utility rate structure.
As an example, look at a hypothetical PG&E medium retail case, the last bar of the waterfall indicates about -$27,000 in net costs (i.e., $27,000 in net value to the customer) as compared to about $450 in net cost for the same case in SCE’s service territory. The difference is mainly due to different electricity rates.
In the figure below, the waterfall graphics present an economic valuation (energy-based) for the owner, including initial costs, financing, operating costs, energy cost savings, and potential ISO market revenues. Net costs are also shown in the rightmost bar: negative costs are positive value to the customer shown as a green bar.
Flexible lighting consumption in a portfolio of buildings can deal with voltage irregularities on the electricity grid. Increasing and decreasing illumination are likely to be unnoticeable; occupants can’t feel changes in light levels due to adaptive eye compensation. Based on empirical studies performed by PG&E’s Pacific Energy Center in the 1990s, building owners can generally lower light levels 40 percent and occupants may not notice, depending on time period.
A barrier to investing in advanced lighting control systems is the perception of high initial costs versus savings, having to do with LED’s low energy consumption. Many people contend that the LED’s reduced wattage makes these systems inappropriate for either additional dimming or to act as DR resources; the efficiency improvement means there simply is not enough wattage left to shed or shimmy.
However, what many designers recognize is that out-of-the-box, these LED systems typically provide too much lighting. These installations use institutional tuning to dim illumination to appropriate levels (high‑end trim). In other words, most new lighting systems are initially operating at about 50% of full output to avoid overlighting.
We are hypothesizing that there could be important synergies between circadian lighting systems that can provide a grid benefit. First, peak demand has shifted to 5-9 pm, which poses serious issues for residential customers. So a circadian-friendly drop in lighting levels in the evening would synergistically help utilities meet that peak demand.
Additionally, circadian lighting could prove to be a valuable resource in commercial buildings due to midday overabundance of solar PV production; a problem in California. The California Independent System Operator (CAISO) deals with power flows on the electricity grid and with highly dynamic power prices. The current net effect in adopting more renewable production means that solar generators are actually paying consumers (negative pricing) to absorb power from the grid nearly every afternoon, due to overproduction relative to grid loads.
A midday circadian bump in light levels may benefit occupants’ health and take pressure off the electricity grid; though more research here is definitely needed.
These two aspects – optimizing occupants’ circadian health while providing simultaneous grid services – could fundamentally change how lighting is specified and controlled. The lighting industry is starting to recognize that controls remain important, not just in terms of on and off, up and down, but also that spectral quality should be designed to match human needs. Utilities are in the position to push circadian priorities in the marketplace as a co‑benefit used to help drive investment in controls, even as LED lighting reaches peak efficacy. The potential grid benefits to adding dynamic lighting open up new revenue streams for advanced lighting controls.