ASHRAE Journal - September 2012 - 74

2012 Award Case Studies 2012 Technology ASHRAE Technology Award Case Studies
From Desuperheater To Desuperheater 2 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Solar Hot Water Circulating Pump Desuperheater Hot Water Circulating Pump Hot Water Storage Tank Pre-Heat Hot Water Storage Tank Hot Water Circulating Pump Chilled Water Pump Expansion Tank Absorption Chiller Heating Water Return Header Heating Water Supply Header Solar Hot Water Supply Header Solar Hot Water Return Header

From Solar Panels 1 11 12 4 4 4 4

To Solar Panels

5 9 10 6 3 3 3 CW Supply

CD Water To Cooling Tower

CD Water From Cooling Tower

Figure 1: Hydronic water system.

The building’s total floor area is 40,589 ft2 (3771 m2), and it has 17,897 ft2 (1663 m2) of air-conditioned office space. The building recently received Gold certification under LEED for Existing Buildings: Operations and Maintenance, 2009. The existing AC system is served by three 15 ton (53 kW) packaged selfcontained, air-cooled, air-conditioning units that are manifolded together to provide conditioned air throughout the office areas. The older system operated as a large constant volume system that staged each 15 ton (53 kW) AC unit to match the loading in each space, which ranges between 20 and 40 tons (70 and 141 kW) throughout the year. The existing 15 ton (53 kW) units have an EER of less than 9.5, and because the system operated as a large single-zone, constant-volume system, thermal comfort within the building was not satisfactory to many occupants. To exacerbate the problem, the roof was not insulated, and heat often radiated down
74 ASHRAE Journal

into the occupied area, causing uncomfortable temperature gradients. As a result, SSFM decided improve its airconditioning system to provide better comfort, and increase energy savings, which also helped it to achieve its LEED certification goals. Due to the large roof area, SSFM evaluated photovoltaic panels and solar thermal air conditioning. Based on the upfront capital cost, including available state and federal tax credits, the solar thermal air conditioning provided the most “bang for the buck.” Therefore, it was determined that a solar thermal AC system would be the most appropriate system to demonstrate renewable technology, yet still use its existing packaged air-conditioning system. The retrofit’s concept incorporates a solar thermal chilled water AC system, which operates parallel to the existing direct expansion (DX) packaged system. With the completion of this project in March 2010, the solar thermal system
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operates as the primary system and the DX system is the backup for cooling the building on cloudy days. The solar thermal air-conditioning system unloads the existing DX system to save electricity. The solar AC system consists of an absorption chiller driven by 180°F (82°C) water generated by standard domestic

Building at a Glance SSFM International
Location: Honolulu Owner: SSFM International, Inc. Principal Use: Office and parking Gross Square Footage: 40,589 Conditioned Space: 17,897 ft2

September 2012

ASHRAE Journal - September 2012

Table of Contents for the Digital Edition of ASHRAE Journal - September 2012