Page 11 - Zero Net Energy Case Study Buildings-Volume 1

INTRODUCTION ZERO NET ENERGY CASE STUDY BUILDINGS, VOL. 1
Code ZNE
California’s Code Metric: “Time-Dependent Valuation (TDV)”
Many building industry experts believe that mandatory requirements pertaining to ZNE are need- ed for ZNE to succeed “at scale.” The State of California is taking steps in that direction. In its building code, California uses a hybrid energy metric known as Time-Dependent Valuation or TDV, with hourly economic multipliers applied to the site energy consumption (and production) as modeled for that building by energy simulation software used to document energy code com- pliance at the time of permitting the building. “Zeroing out” the TDV metric represents a code path to ZNE in California, the future objective for the state energy code for buildings.
Building codes exist to provide a baseline societal benefit and value consistent with public policy for life safety, health and human comfort, environmental impact and other societal objectives. The Warren-Alquist Act, California legislation first passed in 1975, explicity added building en- ergy efficiency considerations into the building code: the law established the California Energy Commission (CEC) and chartered that agency with incorporating energy efficiency into the build- ing code. Thus, the concept of enhancing societal value has been at the heart of Callifornia’s energy code from the earliest stages. Declarations in the Warren-Alquist Act include10
“Electrical energy is essential to the health, safety and welfare of the people of this state and to the state economy”, and that
“Utilities should seek to exploit all practicable and cost-effective conservation and im- provements of efficiency of energy use that offer equivalent or better system reliability.”
The energy code is designed to minimize electric infrastructure costs, land use impacts, air qual- ity impacts and carbon emissions.
California introduced the TDV metric into code in 2005: the core concept was to place increased emphasis on saving “peak” energy—the most costly energy for the grid operators to produce, procure and deliver. The TDV metric creates a structure to accommodate separate economic multipliers for energy for all 8,760 hours in a year. (Before 2005, a single source multiplier was used for all hours.) Simply put, the TDV metric places high value on peak-saving measures. See the graphical illustration of this principle on the following page.
As implemented within the code, the TDV values are applied as hour-by-hour multipliers to the site energy total comsumption as computed by one of the state-certified energy analysis pro- grams such as EnergyPro11.
Under the Warren-Alquist Act, the energy code is required to be revised approximately ev- ery three years. The CEC is targeting its upcoming revisions to the code (often referred to as “Title 24”) to support statewide goals for “all residential new construction to be ZNE by 2020” with non-residential buildings to follow by 203012,13.
10 http://www.energy.ca.gov/2012publications/CEC-140-2012-001/CEC-140-2012-001.pdf
11 Note that the TDV multiplier values are applied only within the context of the building code and code compliance software; there is no one-to-one relationship between TDV values and actual en- ergy consumption, actual utility rates or customer bills.
12 “California Energy Efficiency Strategic Plan–New Residential Zero Net Energy Action Plan: 2014- 2020”, technical report by California Public Utilities Commission (CPUC) and California Energy Com- mission (CEC), Draft 14 October 2013.
13 “California Energy Efficiency Strategic Plan–Zero Net Energy Action Plan: Commercial Building Sector 2010-2012”, technical report by California Public Utilities Commission (CPUC) and California Energy Commission (CEC), June 2011.
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