Case Studies

Case Study 3

Thu, 24 May 2018 07:36:43 GMT

Case Study 3: Mixed-Use Building C

Description: A mixed-use building project with (2) stories of underground parking, (1) story of retail, which wraps around a (6) story office tower. Each occupancy (parking, retail, office) is modeled as a Building Section using the appropirate Loads & Conditions template for that occupancy.

HVAC Systems: Heating and cooling is provided by Variable Refrigerant Flow (VRF) systems. Air handling is de-centralized and provided by the unitary VRF terminal units in the zones

Figure 1: 3D view of the building geometry

Internal loads: The two underground stories have no internal loads or zone condition templates since this is just parking (these thermal zones are grouped into a Zone Group just for the sake of grouping). The rectangular section zones are grouped into the office group and the L-shaped retail zones are grouped into the retail group with corresponding internal loads and zone condition templates.

Office internal load
Internal load type	Value	Weekday	Saturday	Sunday
People	13.93 m2/person 149.94 ft2/person
Lights	10.76 W/m2 1.0 W/ft2
Electrical Equip.	8.61 W/m2 0.8 W/ft2
Retail internal loads
Internal load type	Value	Weekday	Saturday	Sunday
People	? m2/person 100 ft2/person
Lights	? W/m2 1.5 W/ft2
Electrical Equip.	? W/m2 0.86 W/ft2
Office thermostat setpoints
Thermostat type	Min/Avg/Max	Weekday	Saturday	Sunday
Heating Schedule	15.6/18.4/21.1 C 60.0/65.8/70.0 F
Cooling Schedule	23.9/26.3/29.4 C 75.0/79.3/85.0 F
Retail thermostat setpoints
Thermostat type	Min/Avg/Max	Weekday	Saturday	Sunday
Heating Schedule	?? C -76/2.9/69.8 F
Cooling Schedule	?? C 75.2/220/392 F

HVAC: Variable Refrigerant Flow (VRF) system

Figure 2: VRF loop diagram overview (click any image to enlarge)

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 comparison shows that the VRF system uses less energy in heating, but more for fans and cooling. Pumps and heat rejection are not explicitly reported for a VRF system. Overall the difference in site energy is relatively small (2,5%). .

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

The next graph compare the cooling and heating energy between the two design alternatives. The lower graphs shows the air temperature as well as heating and cooling setpoints of the same zone.

Figure 4: Cooling and heating energy demand over outside air temperature and Zone Air Temperature of a specific zone in context of the heating and cooling setpoint temperatures.

Case Study 2

Wed, 23 May 2018 13:46:49 GMT

Case Study 2: Mixed-Use Building B

Description: A mixed-use building project with (2) stories of underground parking, (2) stories of retail, and (4) stories of office space. Each occupancy (parking, retail, office) is modeled as a Building Sections (two sections for the separate retail blocks). Each section references the appropriate Loads & Conditions template for that occupancy

HVAC Systems: Heating and cooling is provided by Ground-Source Heat Pumps (one for each section). Air handling is de-centralized and done by these Unitary Heat Pump air delivery to the zones

Figure 1: 3D view of the building geometry

Internal loads: The lower four stories are office spaces and thus assigned office templates for zone loads and conditions, the upper two stories are hotel floors for the good view around with the respective templates.

Office internal load
Internal load type	Value	Weekday	Saturday	Sunday
People	13.93 m2/person 149.94 ft2/person
Lights	10.76 W/m2 1.0 W/ft2
Electrical Equip.	8.61 W/m2 0.8 W/ft2
Hotel internal loads
Internal load type	Value	Weekday	Saturday	Sunday
People	18.58 m2/person 200 ft2/person
Lights	10.76 W/m2 1.0 W/ft2
Electrical Equip.	13.56 W/m2 1.26 W/ft2
Office thermostat setpoints
Thermostat type	Min/Avg/Max	Weekday	Saturday	Sunday
Heating Schedule	15.6/18.4/21.1 C 60.0/65.8/70.0 F
Cooling Schedule	23.9/26.3/29.4 C 75.0/79.3/85.0 F
Hotel thermostat setpoints
Thermostat type	Min/Avg/Max	Weekday	Saturday	Sunday
Heating Schedule	?? C -76/2.9/69.8 F
Cooling Schedule	?? C 75.2/220/392 F

HVAC: Ground source water to air heat pump system.

Zone HVAC

Mixed water

Figure 2: Zone HVAC group and mixed water diagram overview (click any image to enlarge)

Control and temperatures: The mixed water temperature setpoint is following a deep ground temperature with a 0 C (32 F) setpoint difference between 10 C (50 F) and 80 C (176 F).

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 first report comparison details the end use summary in comparison between the two design alternatives. One can see that the Total Energy End Use shows a nice difference between the two systems.

Figure 3: Comparing Project Comparison Report

The next graph compares the cooling, heating and fan electricity between the two design alternatives. The upper left graph shows the heating electricity and the upper right graph show the cooling electricity in a scatter plot over outside air temperature. Both show that the GSHP does more cooling and a little bit more heating. However in the lower graph one can see that the fan electricity is significantly higher for the PSZ alternative than the GSHP alternative.

Figure 4: Cooling and heating energy monthly and Zone Air Temperature of a specific zone in context of the heating and cooling setpoint temperatures.

Case Study 1

Wed, 23 May 2018 09:23:17 GMT

Case Study 1: Mixed-Use Building

Description: A mixed-use building project with (2) stories of underground parking, (2) stories of retail with an interior courtyard, and (2 x 3) story office towers. Each occupancy (parking, retail, office) is modeled as a Building Section using the appropriate Loads & Conditions template for that occupancy.

HVAC Systems: Heating and cooling is provided by radiant active beams and fresh air is provided by Dedicated Outdoor Air Systems (DOAS).

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