Analysis of Pflugerville Justice Center, Austin, TX

 

Sustainable Design Paper (Group)

Energy Simulation by Openstudio 1.14 with Sketch-up (EnergyPlus)

Spring 2017, Course: Energy Modeling and Design Process

Professor Dason Whitsett, The University of Texas at Austin

Alan Zapalac, Donghwan Kim, and Ke Chen

 

 

1.    building Overview

Our group decided to use the Pflugerville Justice Center as our project one energy model.  Being that this was the largest building available from the Pflugerville selection, it required much analysis to understand its normal day-to-day functions.

First off the facility has a municipal court room, a small jail, city administration offices, Pflugerville Police Department, a gym, shooting range, and a small vehicle impound garage.  All of this within the 35,000 sq. ft. floor plan.  With so many different people in these departments the building envelope has many particular schedules.  Ultimately the facility is open 8-5, and rarely on weekends.  There are about 40 officers, a dispatch crew, and numerous local government employees.  Much of the building consists of long hallways and high ceilings.  Since it was constructed in the early 2000’s we operated under the ASHRAE 2007 conditions, and labeled the building as a secondary school.  Also since the building is massive, we broke it into two parts as you will see in the baseline envelope.   After meeting with Pflugerville Police Chief Robledo, we were not authorized to look at the building plans, but we were given a thorough tour.  From there it was easy to simply map out the building into general areas of operation so we could input the proper constructions.  For scheduling we just asked the officer giving us the tour, who gave us detailed day-to-day functions of different areas of the building.  Many of the smaller rooms and more private areas are generalized.  For example, the front administrative offices and the police headquarters in the back of the building are broken into relatively accurate sized portions and labeled as small office spaces.  However, since we are working under the conditions of a secondary school, the shooting range and courtroom are labeled as a gym due to their large size. 

          The initial model had many problems before we achieved an accurate baseline.  Many of the shading devices and porch areas presented errors in the code.  We also tinkered with the HVAC settings and arrangements to have a less sporadic energy demand.  As mentioned earlier we were not granted access to those plans, so we assumed what areas were tied together in the same HVAC.  At first we had irregular heating in the winter months, but with a few adjustments our baseline seemed to be at a realistic demand for a building this size.  These issues and others are discussed further as we go into detail about our model and its results.

 

2.    General Modeling

 

code Baseline

Pflugerville Justice Center is mainly used as a Pflugerville police headquarter and municipal courts. General modeling is formatted as a secondary school. We make a zoning following functions such as corridors, court (gym), offices, conference, and restrooms. The general 3d modeling is applied to ASHRAE 90.1 2007 standard.

baseline envelope

Baseline modeling is separated by two parts, south and north side. The sketch-up 3d models necessarily include shading devices, roof ceilings, doors, windows, and exterior walls. The shading devices play a major role in controlling natural lighting. The roof space is adjusted by mechanical room in openstudio.

 

 Figure 1. Surface type in Openstudio.

Figure 1. Surface type in Openstudio.

 

schedules

We have set the schedules basically depending on the usage of rooms. Every room is adjusted at ASHRAE 90.1 2007 standard. Additionally, we changed occupants’ schedule by every room, for example, office occupants’ schedule was adapted by working hours.

 Figure 2. Schedule Sets

Figure 2. Schedule Sets

 

Construction

Exterior materials are basically concrete and stone. We adjusted the exterior walls to ASHRAE 90.1. 2007 Exterior wall mass climate zone 2. Furthermore, we set interior surface constructions number at interior walls which are between two zones. Especially, we made exterior wall including 1-inch stucco, 8-inch concrete, mass wall insulation, and half inch gypsum board.

 

daylighting

We drew shading devices at the windows, and we could recognize that the devices played a major role in reducing electricity loads. Additionally, we put the daylighting controls facing windows and opposite walls in every room. With making illuminant map in specific zone, we could get the daylighting data in openstudio.

HAVC system

We have added ‘packaged rooftop heat pump’ as HVAC systems to our baseline modeling. Especially, we used separated systems for 2 zones, dividing office zones and other rooms for HVAC efficiency.

 

3. analysis

Overview

The front building is 44,347 ft2. Net site energy is 1,5000,802 kBtu. EUI is 33.84 kBtu/ft2, which is higher than the expectation. The ideal is to control the EUI under or near 24 kBtu/ft2. Zones include two storages, two lobbies, two corridors, and five office rooms.

The back building is 32,185 ft2. Net site energy is 869,044 kBtu. EUI is 27.00 kBtu/ft2. Zones include two courts, one corridors, and four office rooms.

energy use proportion

The front building has 39% for Interior lighting, followed by 25% for Cooling, 18% for Fans, 16% for Interior Equipment, and 2% for Heating. It shows that the most of energy in the front building is for the interior lighting, then HVAC system.

The back building has 55% for Interior lighting, followed by 19% for Cooling, 11% for Fans, 10% for Interior Equipment, and 6% for Heating. Comparing back building to the front building, if we want to reduce the energy consumption of back building, the reduction of interior lighting is very significant.

 

Monthly Overview

Both the front building and the back building have the similar monthly energy consumption tendency. The cooling consumption increases in the summer and the heating consumption increases in the winter. The consumption peak is on June. However, the electricity peak demand is abnormal in the winter. The heating demand raises a lot and reach the peak on December and continually keeping in a high-level demand till March. That impacts the high-performance of the project seriously and need to be solved.

 

Interior Lighting Summary

In both the front building and the back building, the majority energy consumption is interior lighting. In the front building, even if decreasing the lighting power density, two storage rooms still consume a lot of lighting energy use comparing to office rooms. In the back building, mechanical room consumes the most part of energy, which can be saved by reducing or turning off the lighting system in this thermal zone.

4. passive house exploration

We input the default model into passive house standard spreadsheet. Result shows none of the front part and the back part can reach the standard of passive house. The reason focuses on the cooling system consumption and the abnormal peak demand in winter. To improve the operation, trying to achieve the passive house standard, we try to use the attached strategies and explore the possibilities of energy saving in this project.   

schedule adjustment

By increasing the cooling setting from 73°F to 76°F and reducing the heating system from 68°F to 64°F, the EUI has a minor decrease from 33.8 kBtu/ft2 to 33.1 kBtu/ft2. However, the electricity peak demand improves a lot, specially heating. The heating peak on December decreases from 220 kW to 120 kW, which is closer to the requirement of passive house in a certain degree. We input the result into passive house standard, still having a distance to reach the standard.

hvac adjustment

Turning into the HVAC setting. Frist is to divide the HVAC system into two parts so that they can operate separately when necessary. Then removing the two storage rooms from HVAC system to save energy. Typically it is not necessary to cool or heat the storage rooms. The result shows the energy consumption decreases from 1,500,802 kBtu to 1, 052,911 kBtu. EUI decreases from 33.8 kBtu/ft2 to 23.74 kBtu/ft2. The peak demand also decreases to a acceptable standard. Results shows that the current operation strategies can reach the standard of passive house.

other potential strategies

To further decrease the energy consumption of the whole building, several advanced strategies may be helpful and need to be proved in the future.

First is to add more shading devices. Shading device can reduce the demand of fans, cooling, and heating. However, that may also increase the demand of lighting, which is currently the biggest part of energy consumption in this project. Further researches and simulations are needed to prove this strategy.

Second is to modify the lighting schedule. By adjusting the lighting schedule of storage rooms and counts, the overall energy consumption still has the potential to be saved.

Finally, is to improve the performance of loading system. By updating the current HVAC system to a high-performance production, the energy consumption can also be saved. However, even if that may reduce the future operation cost, it will also increase the investment of equipment.

 

conclusion

The Pflugerville Justice Center is waiting to update. Based on our energy simulation, the building performance still has potential to improve. By taking the reasonable schedules, lighting system, HVAC system, and shading devices, the energy consumption of the building can be reduced. This report is just a general simulation for reference. A further and detailed research is needed for practically adjustment of the operation system.

 

 
 

All rights reserved by Donghwan Kim