COLUMBUS, OHIO—Like most building systems, lighting interacts with other systems in a variety of ways. The main lighting system interactive outputs that need to be integrated include light, heat, and energy load and power quality problems on the distribution system. But how can building and energy managers resolve the drain on resources that these interactions have? The key is in the planning. The next generation of lighting systems will achieve new levels of savings when lighting plans are designed or upgraded to minimize interactions with other building systems. The integration strategies outlined below are a start to reducing interaction-induced energy drains.

Power Side Interactions: Energy Load Management

During file past decade, lighting systems have become more efficient, decreasing the load on power distribution systems. But there is still much to be done since there are many buildings with older lighting systems that need upgrading. However, other than reducing the total lighting load through efficient equipment, lighting has played only a limited role in demand-side load management strategies. Compared with traditional load management options, controlling light output can be a preferred strategy. It is possible to gradually dim lights without attracting the attention of occupants.

Three driving forces are converging to create an opportunity for building managers to achieve significant savings from load management:

Electric utility deregulation: Utilities want to transfer the price fluctuation risk (marginal cost of production) to the customer, evidenced by an increase in time-of-use and real time pricing.

Information technologies: The application of information technologies at the meter and distributed building control level provides real-time access to energy consumption data.

Advances in controllable lighting technologies: Reliable, cost-effective, easy-to-install electronic dimming ballasts and photosensors can be easily integrated with building automation systems, allowing a wide rage of control strategies.

Controlled lighting applications, such as strategic load management and daylight harvesting, place exceptional savings within the reach of building managers. Because load management helps shift the average electricity rate downward, controllable lighting used as a load management strategy yields enhanced economic returns. It is now possible to combine the latest building information technology with controllable lighting systems to transform lighting systems into risk management tools. This combination helps commercial and industrial end users take advantage of the savings opportunities created by electric utility deregulation. This integration offers building managers the flexibility to modify energy usage in response to electricity price signals and increased demand levels and to select a more attractive electric rate. As shown in Figure 1, the building electrical profile usually peaks at midday when most employees are present and the majority of building systems equipment are operating. Lighting represents 30 percent to 40 percent of the total load. Lighting upgrades that use fixed output electronic ballasts can reduce lighting energy by about 25 percent. Controllable electronic systems can produce even greater reductions by taking advantage of control strategies, such as daylight harvesting, occupancy control, and manual dimming. Load management saves even more during peak periods when the marginal cost of electricity can reach more than 20 times the cost of off-peak electricity.

Output Side: HVAC Interactions

Lighting systems interact with HVAC systems in several ways. The heat generated by lighting is a source of excess building heat. In portions of the building where this heat is not usable, the lighting system becomes a cooling load. When lighting systems are upgraded with higher efficiency lamps and ballasts, less heat is generated and the air-conditioning load is reduced.

The reduction in air-conditioning load will decrease the electric bill for buildings using electric chillers. In some cases, this reduction can eliminate or forestall the installation of additional chiller capacity. But the analysis of this change should ensure that there is sufficient capacity in the building heating equipment. The additional fuel cost should be calculated and subtracted from the cooling system savings. This improvement can provide considerable savings for a building owner and is especially effective in downsizing chiller plants that are being replaced as part of a change from CFC refrigerants.

According to T. Kenneth Spain, of University of Alabama, Huntsville, when determining lighting related HVAC energy, it is important to answer the following questions: How much heat is generated by the lighting system? Where does the heat go? How does the heat affect the energy consumption of the HVAC system?

Not all of the lighting system heat will impact the HVAC load at the same time that the lights are on. The actual percentage that impacts the HVAC load depends on the specific type of HVAC system. The impact of the lighting system on cooling energy use depends on two factors: the percentage of yearly heat removed by the cooling equipment, and the HVAC cooling efficiency.

The lighting-related HVAC energy can be calculated by the following formula:

Lighting-related HVAC energy (kwh) = direct lighting energy (kwh) X percent of year HVAC system operates X percent of lighting heat impacting HVAC load X percent efficiency of HVAC system

Efficiency = energy units delivered to or removed from space ¸ energy units into system

Efficiency (cooling) = SEER (Btuh/W) ¸ 3.413 (Btuh/W)

A simplified method of calculating lighting and HVAC interactions, provided by R.A. Rundquist Associates Inc., can be found in a variety of publications, including EPRI Lighting Bulletin, LD+A by the IESNA, ASHRAE Journal, and Strategic Planning for Energy and the Environment by the Association of Energy Engineers. The method is presented for determining the effects of energy efficient lighting designs on HVAC energy and installation costs. Understanding and accounting for associated cooling savings and heating costs is complex, requiring the consideration of several HVAC interactions. Nevertheless, there are some assumptions that simplify the calculation. The calculation is based on the HVAC equipment, internal loads, and typical commercial office building construction. One simplification is the use of published tables of U.S. locations that list the percentage of the year that HVAC systems operate. For example, in Atlanta the additional air conditioning benefit is listed at 19 percent.

Output Side: Light Interactions

Lighting professionals are aware that the reflectance of surfaces in a lighted space affect the amount of light needed. This level of integration does not need much encouragement, but more needs to be done to integrate electric lighting systems with daylight from the fenestration system.

A building's fenestration system includes windows and elements such as shades or blinds. Skylights and window wells also are part of the fenestration system. In the past, windows have represented a main source of unwanted heat loss and discomfort. Selective glazings now reduce solar heat gain by reflection so interior window temperature is lower.

These changes result in improved comfort for those who work near windows. Using windows that reduce solar gain also reduces the mechanical equipment costs for the HVAC system. It is now possible to significantly reduce solar heat gain and improve comfort while providing clear views and daylight. Daylighting is the method of lighting building interiors by using diffuse light from the sky. Modern electric lighting, cheap electricity, and the interest in fully conditioned environments have all added to a situation where daylighting often has been ignored in contemporary building design. However, with recent advances in controls, high-performance glazing, and software tools, there is a renewed interest in active daylighting.

Building System Design Trends

Traditionally, each building system has been designed independently. Since many of the building system interactions could not be easily modeled, none were. Time and budget constraints worked against integration. Several trends are now converging to make it possible to integrate lighting systems with other building systems in ways that are practical, cost effective, and sustainable.

New products: New generation products, especially dimming electronic ballasts and sensors, that incorporate advances in microelectronics provide affordable dimming of fluorescent lamps down to 5 percent. The fade function is built into sensors, no longer needing a separate interface. Instead of being hard wired, sensors can be plugged directly into electronic dimming ballasts using low voltage telephone cables and connectors. High performance glazings and powered window shades are providing new options for fenestration systems that easily integrate with daylight-linked lighting controls.

Energy savings: This trend is evidenced by those building managers who ask what more they can do to save money after accomplishing the common conversion to T8 lamps and fixed-light-output electronic ballasts. Integration of lighting and daylight-linked load management controls represents the next wave.

"Green" buildings: Interest in sustainable building construction has been gaining popularity as carbon emissions continue to climb, in spite of gains in energy efficiency. Progressive architects and engineers are even realizing a profit from sustainable designs.

Design and analysis tools: Improvements in software tools that make them easier to apply are coming to help meet real design challenges. Today's separate tools will become more integrated and less compartmentalized to aid in the selection of fenestration products and assist with daylighting design.

Hybrid Lighting

Hybrid lighting combines natural and electric lighting sources into an integrated system that efficiently distributes daylight and controls the light, adapting it to the environment and the needs of the occupants. Using an integrated approach is important since electric lighting consumes over 25 percent of the nation's nonrenewable energy.

Hybrid lighting integrates several technically diverse components including electric lighting systems, adaptive lighting controls, high performance windows and skylights, and advanced light distribution systems.

Some of the benefits of hybrid lighting include energy reduction, reduced life cycle costs, reduced environmental emissions, improved lighting quality, and enhanced workplace productivity. The Hybrid Lighting Partnership, sponsored by the Department of Energy's (DOE's) Oak Ridge National Laboratory, has a goal to make fully integrated hybrid lighting systems available that translate into a $1 billion market and savings of 10 billion kilowatt hours by 2004. Other goals include reducing lighting energy consumption 25 percent by 2010, and cutting U.S. lighting-related greenhouse gas emissions in half by 2020.

Recent Test Results

In 1995 a partnership of the GSA, Pacific Gas & Electric Co. (PG&E), and the DOE's Lawrence Berkeley National Laboratory was established to implement a large scale test of different lighting control systems at the Philip Burton Federal Building in San Francisco. One floor was designed with no automatic controls. Second generation control strategies were implemented on the other floors, including daylight harvesting automatically dimming the lights in response to available daylight.

The purpose of the lighting controls testbed was to demonstrate whether existing second generation lighting controls are an energy- and cost-effective means of meeting federal efficiency directives. While maintaining occupant comfort and satisfaction, and to demonstrate the additional energy savings benefits, operational advantages, and improved occupant response resulting from the application of more intelligent, third generation, controls.

Third generation lighting controls, which are becoming more available, offer a potential solution to the commissioning problems of earlier lighting controls, and provide many additional benefits, such as lighting energy monitoring capabilities; more accessible dimming; and the ability to respond to real-time utility pricing methods.

The study to date shows that daylight-linked controls should be considered as an energy savings strategy for reducing lighting energy consumption in commercial buildings. Currently available daylight-linked control systems can bring about significant and sustainable reductions in electrical energy in a typical high rise office building. In particular, annual energy savings from these controls was 30 percent to 41 percent for the outer most row of lights, and 16 percent to 22 percent for the second row of lights from the window wall. The lighting energy costs are 31¢, 41¢, 36¢, and 44¢ per square foot per year for the first row south, second row south, first row north, and second row north, respectively. These relatively modest savings translate into very long payback times (nine to 24 years) if the incremental installed cost of the lighting controls is $2 per square foot. If the cost of the lighting controls equipment is $1 per square foot, which is thought to be achievable using currently available equipment, the pay-backs are 4.7 and 6.4 years for the first row south and north, respectively.

The data show that the reduction in electric lighting demand from these daylight-linked systems was coincident with the utility's peak load profile. Thus, this system saved the most lighting power at the time of day the more expensive on-peak energy prices were in effect. The coincidence of the reduction in lighting power with the utility peak load profile is one of the most compelling reasons for considering daylight-linked controls in commercial building applications. Although only six months of performance data has been analyzed, this daylight-linked system has performed satisfactorily, without occupant complaint, since July 1996.

Barriers to Integration: Looking Forward

A serious barrier to integration is "discipline segmentation.'' Architects design a building and its fenestration system; mechanical engineers design the HVAC system; electrical engineers design the power distribution, and sometimes the lighting, system; and perhaps a lighting designer designs the lighting system. Teams of people from each discipline design each system sequentially, and little integration usually occurs.

Controls are still difficult to engineer, install, and commission. Also, compatibility and standardization remain as issues. For example, there is no standard for the control voltage range of electronic dimming ballasts, and some control ranges do not match the output range of photosensors. Costs of controls have decreased some, but the cost needs to get to the $1 per square foot level to make controls more widely used.

Obsolete building codes that require low-voltage wiring to be placed in conduit need to be updated.

Real "teams" using an integrated design approach, thinking outside traditional disciplines, will be necessary to achieve the level of integration required to obtain intended benefits. Architects need to learn, or reacquaint themselves with, daylighting techniques and application of new glazing options. Easy to use design computer tools could speed the integrated design. Affordable, reliable controls that do not take an engineer to install are needed. Commissioning by one person is required. Sensor placement must be easily pre-engineered during the integrated design phase. Integrated lighting will become seamless with the entire building design and, some day, lighting may not be perceived as a separate system.