Page 48 - Zero Net Energy Case Study Homes-Volume 2

CASE STUDY NO. 7
PERLITA PASSIVE HOUSE
Energy Performance
Energy Modeling and Post-Occupancy Measurement
Energy Use—Modeling
As with the Passive House in Case Study No. 6, the Perlita Passive House was required to submit a completed Passive House Planning Package (PHPP)4 to document that all required standards for certification were met5. The computational spreadsheet “software” (an Excel form) is accurate enough in its design, detail and climate information to “predict” closely how the house will actually perform and, as such, is often called a “modeling tool” by Passive House consul- tants. The resulting monthly energy use estimate can help in the sizing of the solar PV system that results in a ZNE-performance for the house.
It is also interesting to compare the results of the PHPP calculations with the actual measured performance over the course of a year. The results of the PHPP calculations for this case study house are shown in the chart on the opposite page; the measured performance data for one year beginning in July 2018 are shown in the chart directly below for comparison.
Energy Use—Post Occupancy Measurement
The Tesla Powerwall has the capability of generating and displaying real time reports on energy generation, energy storage and net import/export to the utility power grid. The energy used to charge the EV is metered separately, allowing the energy used for the house alone to be calcu- lated from the Tesla data. This monthly energy use for the house is shown by the chart on the opposite page.
Energy Production versus Energy Use: Zero Net Energy Performance
The charts on the following page show the solar PV system performance over the course of the year starting in July, 2018. The chart of solar energy production versus energy use includes the monthly energy use data for the EV as well. The relative impact of the EV charging patterns can be seen in comparison to the energy use of the house alone.
The cumulative net energy production is a chart that essentially shows the progression of the en- ergy performance toward ZNE by adding each month’s net energy performance to the previous month’s total—if, at the end of the 12-month period, the curve remains on the positive side of the zero axis, then the building in indeed performing better than ZNE, i.e., Net Positive.
For this case study, even when the renewable energy used to charge the EV is included with the energy used by the house, the cumulative net energy productiion over the course of one year is net positive. The conclusion is that the solar PV system is right-sized for the owners’ current use patterns for both house and EV.
4 The PHPP is a spreadsheet form of energy use calculation by category of load. See: https:// passipedia.org/planning/calculating_energy_efficiency/phpp_-_the_passive_house_planning_ package.
5 Note that the Passive House certification process requires that the project be verified by the PHPP and several other document submittals. The only onsite inspection required is the Blow- er Door test, which has to be done by a Passive House certified consultant. When the pressure test meets the standard, this consultant writes the report on the test results for certification.
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Zero Net Energy Case Study Homes: Volume 2