Page 10 - Zero Net Energy Case Study Buildings-Volume 3

ZERO NET ENERGY CASE STUDY BUILDINGS, VOL. 3 INTRODUCTION
Introduction
This third volume of the series of books, Zero Net Energy Case Study Buildings, is similar to Volume 1 and Volume 2 in that it contains a series of detailed case studies of well-designed, recently-constructed buildings that use an annual total of zero energy1.
The similarities go beyond the use of the same metric for ZNE. They include descriptions of the design process, the design strategies utilized for each building type, the renewable energy systems, the results of energy modeling and comparison with post-occupancy energy measure- ments, a common charting method for the data about the ZNE performance and finally post- occupancy evaluations and “lessons learned”.
On the other hand, Volume 3 departs from these previous two volumes in some significant ways:
• Some of the case study buildings are part of a larger “campus” of buildings, where the solar PV system is not necessarily associated directly with the building (i.e., its roof). The single building model does not apply. We are beginning to see the ZNE concept expanded to include multiple buildings and district-scale solutions, for which these case studies are providing some insights.
• Designed systems in a couple of the case studies include energy storage to allow peak-power reduction and thus savings in energy charges by the connected electric utility. This will grow in importance as a design consideration as the nature of the elec- trical grid and structure of the public utilities inevitably change in the future.
• Many of the case study buildings are programmatically complex and traditionally have high energy use, a particular challenge to the design teams and requiring non-conven- tional solutions. The on-site location of the renewable energy system to support the intensity of energy demand has a limit in these cases and other types of solutions are needed as ZNE in all types of buildings becomes more widely applied.
Some of the case studies of Volume 3 point toward a developing issue as the 2030 goal of all- ZNE buildings (new construction) gets closer, namely where to put all the excess power gen- erated by these buildings during the middle of the day and how to meet the new kind of peak power demand created by all these electric buildings on dark days and in the evening. This is an emerging issue that will be addressed in the next few years, partly as a result of the success of the penetration of ZNE buildings in the building industry in California.
This is the Duck Curve conundrum.
1 We’ll footnote here immediately because of the inevitable discussion that starts about the defi- nition of “zero net energy” (ZNE) in this context. For this entire series of Zero Net Energy Case Study Buildings, we use Site ZNE for this definition. That is, the amount of energy used by the building over the course of a year is equal to the amount of energy supplied in that period of time by the renewable energy system.
See the Introduction to Volume 1 for a thorough discussion of the various definitions of ZNE and why Site ZNE is chosen as the metric for these case studies over metrics mandated by the U.S. Department of Energy (Source ZNE) and the State of California Title-24 energy code (TDV-ZNE). Basically, Site ZNE is the simple net metering definition that is measurable, does not require calculations and is easily understood by the general public. (Often, it is the only type of data collected by the owners of these buildings.)
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Zero Net Energy Case Study Buildings: Volume 3