Page 13 - Zero Net Energy Case Study Homes-Volume 2

Furthermore, even for ZNE houses that utilize energy-efficient electric heat pumps for heating and cooling, and perhaps even domestic hot water, they often use natural gas for cooktops and consequently have a natural gas supply to the house. This carbon-based energy use is offset by the energy produced by additional on-site solar electric panels, so that the total annual energy used is still balanced by the total annual on-site renewable energy generation for the ZNE house.
So, there are several reasons why a ZNE house is probably not a zero-carbon house at the present time.
There is a movement to decarbonize the energy used in buildings because of the pressing need to mitigate the deleterious effects of climate change by reducing or eliminating carbon emissions from all sources. Transforming the building stock, particularly residential buildings, as much as possible to zero-carbon is the goal of this societal effort. (See a diagram for the possible features of a zero-carbon house on the following page.)
The first steps were taken to decarbonize the California public utility electrical grid in September 2018, when the governor signed Senate Bill 100 (SB 100)6, which established the State policy requiring that renewable energy and zero-carbon resources supply 100% of electrical retail sales to end-use customers by 2045. This effectively means that in 2045 all ZNE residential buildings that are all-electric will also be zero-carbon and that a zero-carbon future requires the electification of our homes and buildings7.
ZNE design and performance of residential buildings is clearly the first step toward complete decarbonization of the housing stock in California. Rapid progress continues to be made in this regard. In addition, the use of electric heat pumps for heating, cooling and domestic hot water supply in homes is a growing trend in the state and is responsible for the continuing progress toward decarbonization. Finally, the use of induction cooktops8, recently gaining market accep- tance, completes the recipe for the zero-carbon ZNE home.
6 https://www.energy.ca.gov/sb100
7 See: A. Mahone et al., “Residential Building Electrification in California—Consumer econom- ics, greenhouse gases and grid impacts”, (April, 2019), Energy and Environmental Econom- ics, Inc.
8 Footnote from Volume 1 about induction cooktops:
Induction cooking is a magnetically induced heating method for cooking as opposed to direct electric coils or gas burners. Of the three types, the electric coil is generally regarded as the least energy efficient, the poorest method for cooking because of its relatively slow response to controls and the least safe from casual burns. Gas burners have quick response to controls— their advantage over electric coils—but are a source of toxic chemical by-products and still have a serious burn risk. Induction cooking has all of the advantages of gas cooking, including the degree of control for cooking, is toxin- and carbon-free and the “burner” does not feel hot to the touch after a relatively short time. (Cookware must have ferrous content—stainless steel or cast iron, but not pure aluminum.)
Use of induction cooking, like the microwave oven when it first appeared, is a technological invention that must achieve a familiarity and an acceptance level among homeowners (and chefs). But it is the recommended choice for ZNE and zero-carbon homes. See the following articles for a technical comparison of cooktop alternatives:
(1) http://ovens.reviewed.com/features/induction-101-better-cooking-through-science;
(2) https://www.consumerreports.org/electric-induction-ranges/pros-and-cons-of-induction- cooktops-and-ranges/
(Above) Greenhouse gas(GHG) emission reductions in million metric tons (MMT) required to meet California 2045 targets as specified by SB100, including decarbonization of the grid and electrification of buildings. (From: Pathway 2045--Update to the Clean Power and Elec- trification Pathway, Southern California Edison, Nov., 2019)
INTRODUCTION ZERO NET ENERGY CASE STUDY HOMES
Zero Net Energy Case Study Homes: Volume 2
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