Load and Energy Estimates Resubmission

Diane McArdle
Mechanical Option
Skye Laboratories, Inc. Building E
Fort Worth, Texas
December 10, 2002

Load and Energy Estimates Resubmission

Executive Summary

For this assignment, building load and energy estimates for a 220,559 square foot research laboratory were estimated. The calculations were preformed by hand and Carrier’s Hourly Analysis Program and Energy Analysis Software. The building is an animal testing research facility located in Fort Worth, Texas. It has different systems that supply the 6 different zones in the building. The first floor contains the animal facility, office area, cage wash, and chiller plant. The second floor is primarily the mechanical mezzanine. All zones are conditioned with one air handling unit except the animal facility which has six. The six handling units that serve the animal testing facility are 100% outside air with heat pipe energy recovery. The cage wash zone is also and constant volume system with 100% outside air. The office zone is a variable air volume system. Since the climate in Texas is very hot, the mechanical mezzanine and chiller plant are serviced by individual air handling units with return air. All air handling units are serviced with 44F chilled water from the chiller plant. Since the air in the animal holding area needs to be maintained at 66F, the air handling units contain post cooling coils that are supplied 40F water from a glycol water chiller. The values obtained for the area per ton cooling HAP, hand, and design are 124.3 ft2/ton, 155.4 ft2/ton, and 119.28 ft2/ton. Using the utility rates and total annual energy consumption estimation provided by the engineer, the annual cooling cost is $6.43/sq.ft. The design annual cooling cost is similar to the $5.33/sq.ft annual cooling cost calculated with HAP.

Design Outdoor Conditions ASHRAE Handbook of Fundamentals

ASHRAE FUNDAMENTALS OUTDOOR AIR CONDITIONS
Winter / Summer
Design / Design Dry Bulb and / Mean / Design
Dry Bulb / Wet Bulb / Daily / Wet Bulb
99% / 97.50% / 1% / 2.50% / 5% / Range / 1% / 2.50% / 5%
17 / 22 / 101/74 / 99/74 / 97/74 / 22 / 78 / 77 / 76

Design Temperatures for the cooling and reheat coils taken from the design schedules

Zone / Summer / Summer / Winter / Winter
CFM / Design Indoor / Design OA / Design Indoor / Design OA
Air Temp °F / Air Temp °F / Air Temp °F / Air Temp °F
1 / 175000 / 66 / 100 / 66 / 0
3 / 20000 / 72 / 100 / 72 / 0
4 / 35000 / 75 / 100 / 75 / 0
5 / 7000 / 80 / 100 / 65 / 0
6 / 30000 / 80 / 100 / 65 / 0

Cooling Loads

Data used in calculations were derived from the design drawings and information I received from the designer. Equipment factors were taken from the schedules. Equipment schedules are attached. The lighting loads were determined by counting fixtures on the design drawings, summing their watts in the schedules, and dividing it by the total square footage. Since there is not a definitive guide for occupancy within some of the spaces, I determined the occupancy by examining the interior drawings and relied on desks and chairs. Utility rates were provided to me by the design firm. Gas is $4.0/MMBTU and electric is $0.055/kwh.

For the hand load calculation that followed the process from AE 455 assignment 3, the office area was treated separately than the rest of the building since the other zones are 100% outdoor air or ventilation is determined by equipment emissions.

For the hand load and energy calculation that followed the process from AE 455 assignment 18, the estimate was found by inputting Bin Data for Fort Worth, Texas into a spreadsheet. Calculations for the pumps and fans are attached. For the envelope load the overall U-value was calculated by taking the sum of material area divided by the total area multiplied by the U-value. The envelope load was found by taking the overall U-value times the area times the outdoor air dry-bulb minus room temperature times the hours. All calculation worksheets are attached.

Overall U-value Calculation:

Envelope / Area / U-value / % of Envelope / U-value
Wall / 4763 / 0.064 / 0.14 / 0.008816
Roof / 20756 / 0.04 / 0.60 / 0.02401
Glass / 9060 / 0.65 / 0.26 / 0.170306
Total / 34579 / Overall U / 0.203131

To simplify HAP information entry for the laboratory zone all spaces on the perimeter of this building were entered individually and the rest of the zone was represented as a block. Since the system is 100% outdoor air ventilation rates were not affected by generalizing the HAP data. The HAP results are attached.

Comparison of design document and computed load and ventilation indices

Cooling ft2/ton, total supply air cfm/ft2, and ventilation supply cfm/ft2

Cooling / Total Supply / Ventilation
Method / ft2/ton / Air / Supply Air
cfm/ft2 / cfm/ft2
Design / 119.28 / 1.51 / 1.24
Computed / Assign. 3 / 155.4 / 1.32 / 1.16
Assign. 18 / 138.5 / - / -
HAP / 124.3 / 1.69 / 1.24

The design values were calculated from the loads, supply air cfm, and minimum outside air taken from the attached AHU schedules.

Annual cost to operate chiller plant, fans lighting system, and misc. equipment

Component / Annual Cost $ / Annual Cost $
HAP / Hand
Fans / 278255 / 264911.2
Cooling / 299912 / 481236
Pumps / 213852 / 392208
Cooling Tower / 139819 / 82212.7
Lights / 24262 / 57617
Electrical Eq. / 57400 / 66078
Total / 1,013,500 / 1,344,264

Annual cooling cost per square foot to operate building

Annual Cooling Cost per Square Foot ($/ft2)
HAP / Design
HVAC Sub Total / 4.931 / 4.5
Non-HVAC Sub Total / 0.402 / 1.93
Total / 5.333 / 6.43

Using the utility rates and total annual energy consumption estimation provided by the engineer, the annual cooling cost is $6.43/sq.ft. The design annual cooling cost is similar to the $5.33/sq.ft annual cooling cost calculated with HAP. HAP energy analysis outputs are provided at the end of the appendix.

According to the engineer, a energy analysis was not preformed because the requirements of the indoor environment to meet the requirements for the animals took precedence over the design. An energy analysis would only provide the building owner with a budget for utility costs.