The Daylighting Option

RE Outlook 2003 – As we all debate the merits of Renewable Energy and focus on the small incremental improvements in the conversion technologies to replace the polluting fossil generation of electricity and heat, we should not lose sight of the enormous potential of using the sun directly for our daytime lighting needs through the use of daylight harvesting technologies.

RE Outlook 2003 – January 22, 2003 – As we all debate the merits of Renewable Energy and focus on the small incremental improvements in the conversion technologies to replace the polluting fossil generation of electricity and heat, we should not lose sight of the enormous potential of using the sun directly for our daytime lighting needs through the use of daylight harvesting technologies. Recent studies confirm significant benefits to students, workers and customers in buildings that provide natural lighting. At a recent California Energy Exposition a variety of companies were displaying the latest in roof skylights that include daylighting systems. A number of companies have combined the fixture and the skylight into a hybrid unit that has a number of fluorescent tubes to provide the lighting when the sun radiation levels are to low. Tests performed in the U.S. show cooling load reductions are achieved by removal of the lighting heat even though the roof penetrations have some heat gain impacts. The systems are approved under a variety of the US federal government and electric utility Energy Star programs for energy products, processes and/or technologies. The commercial and industrial lighting sector offers significant energy savings due to the many high intensity discharge (HID) fixtures being used with core and coil ballasts. These fixtures cause high harmonic distortion and contribute to the peak demand when they are on during daylight hours and especially when the sun is adding to air conditioning load. The need to harvest natural daylight and bring it into the workplace, schools and other buildings with cost effective techniques and the appropriate roofing conditions is being addressed by a variety of new technology developments. Daylighting using diffused natural light has been easy to justify on the economics of the high peak power costs and the ability to have the HID fixtures turned off most of the daytime hours. Gradual changes in radiation levels allow the HID fixtures to be restarted very infrequently and with enough time to provide the required light levels. Northern climates have significantly more rapidly changing radiation levels. Light sensors could be attempting to turn on and off the HID fixtures in less than their required re-strike time. A new Canadian electronic dimmable HID ballast technology has been developed that can provide the rapid response to changing daylighting levels in northern regions. New digital light sensors can measure lumen levels, occupancy as well as temperature if required and transmit this information to the controllers that are then able to dim only the fixtures needed and only to the level required to maintain the predetermined balance between daylight and electric light. The added benefit of sensing occupancy allows for additional savings by dimming the lights to lower levels even when the daylighting is reduced. The electronic ballasts provide significant savings when the HID lights are on during all non-daylighting periods. Although the HID fixtures do require the low level of lighting to be maintained in order to respond quickly to the changes in the daylighting levels in northern climates, the additional savings from dimming at all times when there is no one in the area and the reduction in heat from the operation of the ballasts can provide the overall economic benefits to now have daylighting part of the northern regions “green” building agenda. About the Author: David Katz leads a team of Canadian consultants providing energy efficiency and Renewable Energy expertise. As a former utility system planner and financial evaluations consultant he has evaluated the system economic benefits of a variety of Renewable Energy technologies. He is currently evaluating the economic, environmental and emission reduction benefits of Renewable Energy technologies under the northeast climate conditions. He can be reached at dkatz@sustainable.on.ca

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