Net-zero nation: HVAC and PV systems for residential net-zero energy buildings across the United States

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 model to evaluate various electrically-powered 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 economics were 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, with the GSHP providing 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 HVAC and PV designs for residential NZEBs in different climate zones.

Analysis of the Methodology to Obtain Several Key Indicators Performance (KIP), by Energy Retrofitting of the Actual Building to the District Heating Fuelled by Biomass, Focusing on nZEB Goal: Case of Study

“…For the environmental impact assessment of the change of the DH system fueled by biomass versus the old energy system fueled by NG, Carbon emissions per year are calculated on the heating consumption at the EII building, between 2016 to 2017, for each energy system. If the energy system fueled by NG were working, its carbon emissions would be: (11) To calculate the carbon emissions of the current energy system (DH fueled by biomass + energy system fueled by NG) it is carried out in the same way:…”

“…One of the challenges for near Zero Energy Consumption Buildings (nZEB) is thermal conditioning systems, Wu et al [11] compared the energy performance of HVAC systems for a zero-grid energy residential building (nZEB) in different climate zones in the United States, where air conditioning represented 23.8% to 72.9% of the total energy of the building, depending on the air conditioning option and climate zone. In [12] whether nZEB standards applied to Italian school buildings guarantee good thermal conditions inside and which building configuration is the most favored was studied.…”

Optimization of Energy Consumption in Net-Zero Energy Buildings with Increasing Thermal Comfort of Occupants

“…Wu et al examine the energy performance and initial costs of one residential net-zero energy building (NZEB) in different weather regions, using a TRNSYS model confirmed by operational data of a whole year. They reported that energy and cost data as well as the required PV capacity can make heating, ventilation, and air conditioning (HVAC) and PV designs for design and planning residential NZEBs in different climate zones [21].…”

A Study on Energy-Saving Technologies Optimization towards Nearly Zero Energy Educational Buildings in Four Major Climatic Regions of China

“…The results showed that the building with only high-efficiency PV modules comes closest to reaching a zero energy balance. Wu et al [37] found that ground source heat pump (GSHP) used less energy than the air source heat pump (ASHP) Energies 2019, 12,4734 3 of 31 in 11 out of 15 zones across the United States, particularly in cold climate zones like Chicago through Duluth, where savings ranged from 24.3% to 39.2%.…”