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Getting Serious About Daylighting

By: Yetsuh Frank

April 01, 2013

In the aftermath of Sandy, the New York City environmental community has been consumed with questions of resiliency and reconstruction. While these subjects are of pressing importance, it's critical that we do not focus solely on adaption to climate change impacts, or grow lackadaisical in our efforts to curb the consumption of energy. It would be even more unforgivable if we ignore an area of action and study that might benefit the goals of both adaptation and mitigation. Resiliency is mostly concerned with how to ensure our buildings remain habitable in the absence of electricity. Efficiency is mostly concerned with designing systems that use as little electricity as possible to provide the same service. Taking advantage of daylight to brighten our interiors rather than electric lighting addresses both concerns.

Turning off the lights when there is plenty of daylight available seems, to our organization, an obvious goal. To begin with, daylight is typically a lot more pleasant than electric illumination. It provides a softer atmosphere, varies from hour to hour and connects us to the circadian rhythm of each day. For a species that spent a millennia outdoors — our formative years, so to speak — daylight is a primary need, a central component of environments we like to spend time in. And then there is all that energy. If you turned off most the lighting that is running during daylight hours how much energy and money might you save?

Green Light New York, working with Adam Hinge of Sustainable Energy Partnerships, looked at exactly this question: If advanced daylighting systems were deployed throughout New York City offices how much energy could be conserved? Our report, Let There Be Daylight answers this question in four parts. First, it analyzes which systems would be most effective in controlling daylight and reducing the use of electric lighting. Second, it estimates how much office space across the city would be suitable for such a system. Third, it projects the amount of energy and money that might be saved as a result, and finally, it outlines the barriers to implementing such a scheme and how they might be surmounted.

The context and timing of this report are important. The commercial office market of New York City is huge, representing fully 10% of all office space in the United States and 76% of the office space in-state. And this massive market is on the brink of upheaval. The Greener Greater Building laws passed in 2009, will drive the renovation of 1.25 billion square feet of office lighting by 2025, while more stringent and more closely monitored energy codes will drive improvement in lighting across all building sectors. As the lighting systems in one of the world's great financial centers is replaced and retuned to meet current codes, it is critical that we do not miss a related and significant opportunity: the deployment of advanced daylighting controls across the office landscape.

Our analysis indicates that at least 114 million square feet of New York City office space can easily accommodate the inclusion of comprehensive, advanced daylighting controls and that these retrofits could result in electric peak demand reduction of as much as 160 megawatts, and 340 gigawatt hours (GWh) of electricity savings. This peak demand reduction is greater than the capacity of the gas-fired Far Rockaway Power Station, one of several power plants within the city limits. [1]

The chance to achieve routine peak demand reductions serves as a critical argument in favor of daylighting systems. The greatest availability of daylight coincides with the time of day (early afternoon) and the season (summer) when electricity demand is highest. In addition, not all electricity is created equal. Electricity is most expensive during peak periods, as noted above, and peak periods are typically when the most polluting, least efficient power plants are brought on line to feed the grid. So reductions in peak demand have irrefutable cost and environmental benefits.

We estimate that deployment of advanced daylighting systems would result in financial savings of over $70 million annually for local building owners and tenants.

However, our analysis also discovered significant challenges to broad implementation of advanced daylighting systems. The components of the most commonly successful systems — dimming ballasts, appropriate controls — remain expensive and many existing daylighting systems are not working as intended, or have been disabled, meaning that often these systems are not delivering expected savings. To address these problems, our report describes a phased "Path Forward" that begins with a program to monitor and analyze a series of advanced daylighting demonstration projects to determine the critical elements of successful installations. Armed with the set of solutions that are most likely to produce successful outcomes public agencies and energy authorities will be in a position to develop targeted incentives that will encourage adoption.

The demonstration project phase of this program is critical and understanding the technical and the human sides of performance data is key. Most of what people "know" about previously deployed daylighting systems, both positive and negative, is anecdotal. When anecdotes constitute the knowledge base for daylighting, bad things are likely to be the result — from perfectly workable solutions being discarded as bad ideas for no good reason, to unworkable solutions being constructed out of wishful thinking.

A systematic demonstration program that will measure project performance, interview the stakeholders — from designers to constructors to occupants — and develop a robust understanding of the project elements is the only way of understanding what distinguishes successful projects from those that are not effective or present continual challenges. Today we also recognize that many "successful" daylighting projects have had longer roads to their destination than originally anticipated. Building a bookshelf of case studies that document these challenges and what it took to surmount them will be an excellent resource. The solutions in these demonstration projects can form the backbone of incentives from the Department of Energy, NYSERDA or Con Edison and will pave the way for advanced daylighting controls to become a standard feature of office space in New York City.

Electricity for larger buildings is billed for two quantities: the amount of electricity consumer ("energy" used, measured in kilowatt-hours, or kWh), and the "peak" demand (expressed as kilowatts or kW) in any given billing period For most customers, "peak demand" is the highest amount of kW used during any 30 minute period in a given month, and for a large number of New York City office customers, the highest demand set in any month is current as the per kW charge for the full year. This "ratchet" mechanism gives customers strong incentive to keep their electric load relatively flat and consistently low throughout the year. As such,"peak demand" is perhaps the single most important determinant of a building's electricity charges. Energy providers charge for "peak demand" levels because they are required by regulation to be able to supply that amount any time a customer may need it; as a result peak capacity is is major cost driver of current utility rates.

Yetsuh Frank is an architect, writer and educator with over 15 years experience in green building and sustainability. Previously a Director at YRG sustainability consultants, Yetsuh currently leads the Program and Communications efforts of Green Light New York, a non-profit advocating for energy and lighting efficiency within the NYC real estate community. He is Adjunct Associate Professor at New York University and serves a limited number of private clients as Director of Quinault Consulting.
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