ABSTRACT A detailed study has been conducted to compare the overall boiler operating cost of coal versus natural gas firing. For this purpose, an analysis of the parasitic losses and costs of a current boiler operation is given. The results of this study show that it is important to consider both the apparent and hidden costs of boiler operation, and to look beyond fuel cost when making decisions of whether to fire coal or natural gas.

This paper compares the results from the daylighting simulation of a classroom at Northern Guilford Middle School in Greensboro, North Carolina, with the actual measured illuminance levels from the school. The daylight modeling program DAYSIM was used in conjunction with an EPW weather file to perform annual daylighting simulations. Actual illuminance measurements were taken inside the classrooms over a year using photometric sensors and data-loggers. The simulated average daily illuminance is compared with the corresponding measured value for a sunny and cloudy day for all the months except February, August and December. The average daily variation for sunny and cloudy days is 18 fc and 9 fc respectively. The simulation correctly models the decaying illuminance levels with increasing distance from the daylighting glazing. This paper also proposes that in modeling a day-lit space using EnergyPlus weather files and DAYSIM, the modeler must focus on accurately modeling only average daily or monthly illuminances and not illuminances at a specific time of the day during the year.