Case 2: University building

Heading: Educational building with 3 building sections and active beam DOAS system

Geometry: This building models has two rectangular floors with two separate L-shaped building sections with 3 stories each on top. This shows Simergy’s capability to model buildings with more than one footprint. It also includes external horizontal shading on south, west and east facades. In addition, in the two lower floors two window arrays are used.

Figure 1: 3D view of the building geometry

Internal loads: Internal loads are all set to a school building divided into the 3 building sections.

School internal loads
Internal load type Value Weekday Saturday Sunday
People 2.32 m2/person
24.97 ft2/person
Lights 12.92 W/m2
1.2 W/ft2
Electrical Equip. 10.98 W/m2
1.02 W/ft2
Office thermostat setpoints
Thermostat type Min/Avg/Max Weekday Saturday Sunday
Heating Schedule 16.0/17.2/19.0 C
60.8/62.5/66.2 F
Cooling Schedule 26.0/28.1/29.4 C
78.8/82.8/85.0 F

HVAC: The building is equipped with an active beam system that provides cooling and heating (as needed) in an efficient manner due to the reduced size of the air system.

The air loop is a DOAS system with heat recovery and DX cooling and gas heating. This case study uses non-water based heating in the air loop to reduce the need for a two different hot and chilled water loops. The active beams use lower hot and hotter cold water supply temperatures than air loop coils would. The active beams are connected to two water loops (hot and cold) as well as a condenser loop

Air loop Chilled water loop
Hot water loop Condensor loop

Figure 2: Air and water loop diagram overview (click any image to enlarge)

Control and temperatures: The air loop as a DOAS system is controlled at a supply air temperature of 15 C/ 59 F. Due to the lower hot water temperature (26.67 C/80 F) and hotter cold water temperature (10 C/ 50 F) for the active beams the two water loops run on more efficient temperatures than regular water loops. The condenser loop is controlled based on outside air temperature.

Results: compared to an ASHRAE-7 system (VAV reheat air terminals with water based cooling and heating, hot water loop with 2 boilers, chilled water loop with two chillers and a condenser loop with 2 cooling towers). The “Energy End Use Summary” report highlights the difference between the two systems at an end use breakdown. You can see that the air flow is reduced as well as the heating and cooling energy. Internal loads however are as expected the same.

Figure 3: Comparing Page 3 of Project Summary report: “Energy End Use Summary”

The air flow graphic below shows outside air flow fraction indicating that the active beam system is a 100 % outside air system (Or DOAS). The lower graph shows the Fan Electric Energy also showing the constant and lower air flow of the active beam variant.

Figure 4: Outside air flow fraction and fan electric consumption