A Model for Evaluation of Life-Cycle Energy Savings of Occupancy Sensors for Control of Lighting and Ventilation in Office Buildings

Lighting and ventilation represent the majority of the air conditioning loads in office buildings in hot humid climates. Use of motion sensors is one way to minimize the energy used for these loads. This paper describes the methods used for simulation a case study building with motion sensors installed and the monitoring of system on-off statistics related to occupant patterns. It also describes the development of the Monte Carlo model used to predict the on-off status of sensors. The building using the motion sensors is compared to a building that controls the lights and ventilators by a conventional pre-programmed schedule. The conventional methods of simulation were shown to generate misleading information regarding electric demand charges and life-cycle costs of the building. When comparing to actual use patterns, the Monte Carlo process was shown to represent an adequate way to represent the on-off patterns. Computer simulations further demonstrate the potential life cycle cost savings from the use of the motion sensors

Estimated Savings from Turning Off Unnecessary Lights at the Langford Architecture Center During the 1996 Christmas Holidays

During the 1996 Christmas holidays the College of Architecture initiated a trial program to turn off unnecessary lights during unoccupied periods. This effort targeted the unnecessary lights in all studios, classrooms, labs and offices. Had those lights been left on, the building would have consumed 100 kW more electricity every hour. The total electricity savings was about 31,200 kWh over 13 days, which is equivalent to a total cost saving of $936.00. If the College continues to turn off unnecessary lights during unoccupied periods, the estimated annual cost savings would be$13,711, which is 40% of the target savings estimated in the test we performed earlier in 1996. Labor costs to accomplish a manual shutdown are approximately $96.00 per week. If this is deducted from the annual cost savings, the lighting turn-off program still saves about$8,632 per year

The Framework of an Optimization Model for the Thermal Design of Building Envelopes

Careful long term decisions in the design and operation of buildings can significantly improve the thermal performance and thus reduce the consumption of energy. The availability and ease of use of today's computers can be a sigruficant benefit to the decision making process of building design. In dealing with the building as a thermal system, the proper selection of its components and their relationships can be organized using a systems approach. This can be achieved by coupling an optimization technique into the thermal performance of buildings early in the design process. This requires formulating the building as a well-defined thermal system in a framework suitable for the application of systematic approaches. The aim of this paper is to describe the basic framework of a building thermal design optimization model by defining building design variables, a criterion of optimality, constraints, and a suitable thermal simulation model that can be integrated into the proper optimization technique

Evaluation of Lightshelf Daylighting Systems for Office Buildings in Hot Climates

This paper presents part of an on-going research project in the College of Architecture at Texas A&M University. This research investigates how lightshelf daylighting delivery systems can manipulate sunlight and daylight both in terms of their light and heat by shading view apertures below the shelf to reduce solar heat gain and glare and by reflecting light deep into the space through the daylight aperture above the shelf. It also investigates how to provide view with good interior lighting in terms of light levels, distribution, and glare. Evaluation of these systems are based on two different experiments. The first uses scale-models for daylighting evaluation. Methodology of the research is presented as well as results and evaluation for part of the first experiment. The second experiment will use computer program simulations for energy evaluation that include reducing lighting and cooling loads and shaving peak loads, especially, when used with selective low-e glazing for office buildings in hot climates

Effectiveness of External Window Attachments Based on Daylight Utilization and Cooling Load Reduction for Small Office Buildings in Hot Humid Climates

This study explored the effectiveness of selected external shading devices and glazing treatments used to minimize the total annual energy consumption in small office buildings in hot humid climates. The external shading devices included a permanent horizontal overhang and a light shelf. The selected types of glazing included clear, reflective, tinted, low-emissivity coating, and heat-mirror glass. One concern about using external window attachments is that while reducing the solar heat gains, they also reduce the amount of the daylight needed to supplement interior lighting. Therefore the objective of this study was to explore which strategy would give a balance between solar heat gain reduction and daylight utilization and result in the most energy savings in the building. Computer simulations using an hourly energy calculation model were conducted to predict the building's total energy consumption using each strategy. The economics of each strategy were analyzed with lifecycle costing techniques using the present value technique. Results show that properly designed overhangs that shade clear glazing are slightly more cost-effective than specialized low-e glazing systems. These results are unique for hot humid climates where winter heating is not an issue. On the contrary, when used in cold climates, external shading devices tend to increase the building's energy consumption

A Calibration Methodology for Retrofit Projects Using Short-Term Monitoring and Disaggregated Energy Use Data

This paper presents an improved methodology to calibrate energy simulation models to better represent the actual energy use breakdowns in existing buildings. The goal of this methodology is to help architects and engineers accurately determine the current energy use and identify any energy-related problems in the building before proposing the retrofit design solutions, without conducting long-term monitoring. The methodology includes procedures to conduct systematic data collection, "on-off' tests to determine the power densities of the electrical loads, up to four weeks of building energy monitoring to derive the energy use profiles and temperature settings, and disaggregation of the measured energy use data. The procedures also utilize the monthly utility billing records and site weather data. The calibration to the measured data is done on both hourly and monthly basis. The procedures are built into a computer program and integrated with previously developed simulation software. The user interface of the program includes guidelines to help the user decide which simulation input variable has to be altered in order to match the measured data. It also produces graphical outputs to help in visualizing the results, and several guidelines to help study different retrofit strategies after the model has been calibrated

Daylighting Analysis through Scale Model, Full Scale Measurements and Computer Analysis for a Texas A&M University Campus Building

In the first part of this study, daylighting levles in an actualy classroom are compared to scale model measurements and to computer program predictions. Secondly, the daylighting effects in the building atrium are examined through the studies of an actual building and of a scale model. Results are reported about how these data compare to each other

Estimated Savings from Turning Off Unnecessary Lights at the Langford Architecture Center During the 1996 Christmas Holidays

During the 1996 Christmas holidays the College of Architecture initiated a trial program to turn off unnecessary lights during unoccupied periods. This effort targeted the unnecessary lights in all studios, classrooms, labs and offices. Had those lights been left on, the building would have consumed 100 kW more electricity every hour. The total electricity savings was about 31,200 kWh over 13 days, which is equivalent to a total cost saving of $936.00. If the College continues to turn off unnecessary lights during unoccupied periods, the estimated annual cost savings would be$13,711, which is 40% of the target savings estimated in the test we performed earlier in 1996. Labor costs to accomplish a manual shutdown are approximately $96.00 per week. If this is deducted from the annual cost savings, the lighting turn-off program still saves about$8,632 per year

Enhanced Software for Displaying Orthographic, Stereographic, Gnomic and Cylindrical Projections of the Sunpath Diagram and Shading Mask Protractor

The well-known versions of the sun-path diagrams and shading mask protractors that appear in the AIA's Architectural Graphics Standards (Ramsey and Sleeper 1994) are based on the equidistant projections and use a shading mask protractor developed by Olgyay and Olgyay at Princeton University in the 1950s. In the previous papers by McWatters and Haberl(1994a; 1994b;1995) and Oh and Haberl(1996;1997) the development of a computerized display of the equidistant projection of the sunpath diagram and shading mask protractor was presented. This paper describes enhancements to the display of the sunpath diagram and shading mask protractor that include orthographic, stereographic, gnomic and cylindrical projections. Descriptions of the new algorithms and examples of the different displays are also provided