Page 139 - Zero Net Energy Case Study Homes-Volume 2

OBSERVATIONS ZERO NET ENERGY CASE STUDY HOMES
All three single-family homes and the multifamily project in Case Study No. 11 utilize this equipment to guarantee controlled fresh-air ventilation in these homes built with air-sealing techniques.
• Induction cooktops and electric ovens.
These same four projects have kitchens with induction cooktops. The remaining two case study projects, the two multifamily affordable housing projects, selected electric cooktops to maintain the non-carbon nature of the selected equipment and appliances.
This list of advanced design features common to these case study projects indicates that these are now accepted practice in the design of ZNE homes. When the electric utility grid achieves a zero-carbon power mix in 2045, these all-electric ZNE case study homes will become zero- carbon homes as well.
Continuing Observation: Modeling and Measurement
Ordinarily, energy monitoring equipment is not usually installed for cost reasons and the owner has to rely on the monthly performance as reported by the utility net meter data. This data rep- resents the difference between the energy used and the energy generated on-site by the solar PV system for the reporting period. More useful information identifying patterns of energy use or possible equipment failure or inefficient operation is desirable, but usually not obtainable unless some kind of monitoring equipment is installed.
As discussed in the multifamily affordable housing case studies of this Volume 2, this aspect is particularly helpful with regard to controlling operating costs during the life of the building and keeping the solar PV systems at maximum efficiency through good maintenance.
Recent battery technology improvements with regard to built-in data recording and accessibility via portable computer devices have led to a convenient method of reporting energy use, energy production and storage. This is yet another advantage of including a basic battery component as part of the solar PV system.
Looking Ahead
With the official adoption of the 2020 California Building Code, the general stock of new residen- tial housing will move closer to ZNE design and performance, as the pre-permit calculation of annual electric energy used will be required to be offset by the energy generated by a solar PV system. This is still not ZNE in general, nor zero-carbon, but it is another step in that direction.
Rebates for solar PV systems are phasing out but California rebates for battery storage compo- nents are continuing until 2025. As noted in these Volume 2 case studies, energy storage in the form of batteries is becoming more prevalent in the design of ZNE homes, partly because of the incentive but also as a hedge against the anticipated power outages during “wildfire season” in California.
Design strategies for ZNE homes are likely to remain as listed above, especially as costs come down as the market matures. The impact of the growth of the number of electric vehicles, how- ever, and how their energy systems interact with home design may prove to be impactful in the future. As noted at the end of Volume 1, future case study residential projects are likely to involve issues beyond design for annual ZNE performance to include the grid harmonization of solar electric power generation and also energy storage (batteries) to optimize both grid performance and the cost of energy to the residential consumer via time-of-day rate structures.
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