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Net-zero Nation: HVAC and PV Systems for Residential Net-Zero Energy Buildings across the United States

Published

Author(s)

Wei Wu, Harrison M. Skye

Abstract

This study compared the energy performance and initial cost of photovoltaic (PV) and heating, ventilating, and air-conditioning (HVAC) equipment for a residential net-zero energy building (NZEB), in different climate zones across the United States. We used an experimentally validated building simulation to evaluate various all-electrically-driven and commercially- available HVAC technologies. The HVAC accounted for 23.8 % to 72.9 % of the total building energy depending on the HVAC option and climate zone. Each HVAC configuration was paired with a PV system sized to exactly reach the net-zero energy target, so the economy was compared based on the initial PV + HVAC cost. Mechanical ventilation was considered with and without heat recovery; the heat recovery ventilator (HRV) saved a significant amount of energy in cold winter months and hot summer months, and the energy recovery ventilator (ERV) provided additional benefit for humid zones. The HRV was cost-effective in the cold northern latitudes of Chicago, Minneapolis, Helena, and Duluth, where energy savings reached 17.3 % to 19.7 %. In other climates, ventilation without recovery was more cost effective, by 1 % to 9 %, and sometimes even more energy efficient. The ERV was never the lowest cost option. A ground- source heat pump (GSHP) and an air-source heat pump (ASHP) were compared, where the GSHP provided significant energy savings, 24.3 % to 39.2 %, in heating-dominated climates (Chicago through Duluth). In warmer climates, the GSHP saved little energy or used more energy than the ASHP. The PV + HVAC cost was lower everywhere with the ASHP, though it is possible for colder climates that a carefully sized GSHP and ground loop could be cost-competitive. The energy and cost data as well as the required PV capacity could guide the HVAC and PV designs for residential NZEBs in different climate zones.
Citation
Applied Energy
Volume
177

Keywords

Net-zero energy building, climate zone, HVAC, heat recovery, ground source heat pump, initial cost
Created December 1, 2018, Updated April 1, 2019