Page 30 - Zero Net Energy Case Study Buildings-Volume 2

CASE STUDY NO. 7
DPR CONSTRUCTION OFFICE BUILDING
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Domestic Hot Water
A solar thermal system for domestic hot water (DHW) was specified and installed. The system consists of two 4’X8’ panels and a 120-gallon storage tank with electric backup. There is, there- fore, no natural gas fuel used in this building. The non-renewable energy displaced by the solar thermal system is calculated to be 3,400 kWh/year or roughly 0.6 EUI, with a payback (ROI) at 5 years.
Plug Loads
A plug load study was performed to identify equipment and large energy consuming systems in addition to standard building operation systems. This study satisfied the obvious need to under- stand this electric load in order to properly size the on-site solar PV system. New DPR equipment purchasing decisions were also informed by this study.
Control of the plug loads is an essential component of low-energy and ZNE building perfor- mance. The DPR Office includes a number of these measures including occupancy sensors at the overhead light fixtures, “smart” plug strips using plug load management software6, measuring all plug load circuits and reporting to a centrally-visible energy dashboard and, finally, a building plug load “kill-switch”.
The kill-switch, a large red button located adjacent to the main entrance door, is by mutual agree- ment operated by the last person leaving the building. This essentially eliminates all “parasitic” loads, including various equipment “always-on” operation. The overall control system for the building manages the shutdown to ensure the integrity and easy startup of all systems on the following day. The computer network is operated on a separate system so that normal system updates can be installed overnight. Each workstation has a color-coded outlet indicating the computer system circuit, though most staff take their laptop computers home at night.
Building Control Systems
At the time of the design and construction of this project (2013-2014), an awareness had devel- oped of the potential problem issue of the coordinated design of the different control systems for the various energy systems in zero net energy buildings. (See Volume 1, Zero Net Energy Case Study Buildings, for a discussion of the particular problems with control systems in the earlier buildings of case studies No. 1 through No. 6. See also the discussion of this issue in the Intro- duction to this Volume 2.) Partly driven by this awareness and understanding that control system problems could cause delays with the greatly accelerated schedule, the client partnered with the building management system vendor, Honeywell, to engage a master system integrator early in the design-build process.
There are eleven different control systems integrated into the overall master control system. (See the diagram on the facing page.) Because of the pace of the project, the different sub- system vendors had already been selected. The integrator therefore was required to work with the separate communication protocols that were already established for the project. As noted in the Introduction, there are three principal communication protocols in use in the U.S. at this time, two of which are utilized by sub-systems in this building (BACnet and Modbus). Each one was slightly changed by the sub-system manufacturers to suit their purposes, however, so the integrator was required to work with a technician from each manufacturer in order to coordinate the system communications properly.
6 See, for example, https://www.enmetric.com/platform
Zero Net Energy Case Study Buildings: Volume 2