Elsevier

Journal of Cleaner Production

Volume 172, 20 January 2018, Pages 106-118
Journal of Cleaner Production

Energy performance and the discrepancy of multiple NetZero Energy Homes (NZEHs) in cold regions

https://doi.org/10.1016/j.jclepro.2017.10.157Get rights and content

Highlights

  • Monitoring of the energy performance of multiple NZEHs is presented.

  • The average energy balance was −1.4%, close to the zero energy balance target.

  • The energy performance of multiple NZEHs is compared and analyzed.

  • The data integrity is validated using various data sources.

  • The findings can be referred to improve operations and future design of NZEHs.

Abstract

A NetZero Energy Home (NZEH) is designed, modelled, and constructed to produce as much energy as it consumes on an annual basis, with the required energy generated from renewable resources. However, the actual performance of an NZEH may vary from the design objective, and the performance of a given NZEH may differ from other NZEHs. In order to examine the actual energy performance and identify discrepancies among multiple NZEHs, a research project has been initiated in which six NZEHs in Edmonton and Calgary, Canada, built by Landmark Group of Companies, are monitored, assessed, and compared in this research. Complete annual data has been collected for four of the NZEHs to date, and the results show the average energy balance, excluding the NZEH with a period of non-occupancy (listed for sale), reaches −1.4%, which is very near the targeted balance. The actual energy performance is analyzed and compared for the monitored NZEHs by category, including space heating, domestic hot water (DHW) heating, ventilator, and base loads (including major appliances). Overall, space heating and cooling are found to account for more than 50% of the total energy usage of the NZEHs, except for one listed for sale; all the base loads of the analyzed NZEHs are lower than the base load predicted in HOT2000 (19.5 kWh/day). The factors contributing to energy performance variations are also analyzed by category in this paper. This research thus addresses the actual energy performance and discrepancies among multiple NZEHs in cold regions; the research results can be referenced to improve building operation and future design of NZEHs.

Introduction

The building design philosophy to realize net zero energy or carbon neutral housing has emerged as a driving force to enhance the green building design strategies (Chang et al., 2011). Within this context, NetZero Energy Homes (NZEHs) become a promising solution able to alleviate the energy strain that residential buildings exert on limited natural resources, thereby reducing their detrimental impact on the environment. The Canadian Home Builders’ Association (CHBA) defined a NZEH as “one that is designed, modelled and constructed to produce as much energy as it consumes on an annual basis” (Canadian Home Builders’ Association, 2015). Similar concepts include Zero-carbon Building (ZCB) and NetZero Energy Building (NZEB). Comprehensive research has been conducted on ZCBs. Pan and Garmston (2012) examined the compliance with building energy regulations of new-build dwellings in England and Wales, and revealed that the practice of compliance was insufficient, even though new homes should be ‘zero carbon’ from 2016 in UK. Based on the status quo of ZCBs, Pan and Ning (2014) discussed the challenges in achieving zero carbon, and proposed recommendations including explicitly defined zero-carbon principles. Pan (2014) also proposed broader system boundaries to define ZCBs, including policy timeframe, building lifecycle, geographic, climatic, stakeholder, sector, density and institutional boundaries. NZEB covers both residential and non-residential zero-energy building types, and the related projects have been reviewed by Proskiw (2010) and Musall et al. (2013). Deng et al. (2014) summarized the evaluating methods with regard to the performance of NZEBs. Heiskanen et al. (2015) studied the demonstration solar buildings in Finland, including zero-energy apartment buildings for elderly care, and summarized the opportunities and challenges for the application of solar buildings in Finland. Yi et al. (2017) considered ecosystem development on a global environment scale, and used ecological indices and metrics from Howad Odum’s ecosystem theory and energy to assess the sustainability of NZEBs.

The actual energy performance of energy-efficient buildings has also gained worldwide attention. Thomas and Duffy (2013) utilized the information provided by the homeowners and utility bills to investigate the actual energy performance of NZEBs in the New England region of the United States; out of the ten NZEB cases, six achieved at least net-zero energy, and the actual performance of NZEHs was found to be more dependent on occupant behaviour than on design. Norton et al. (2013) demonstrated a comparison between the modelled and measured energy performance of NZEHs in Hawaii; in addition to the monitored performance feedback to homeowners, the research results have supported the energy efficient design in tropical climates. Rodriguez-Ubinas et al. (2014) have described an energy efficiency contest of zero-energy homes in Europe; the interior comfort, functioning, and energy performance of zero energy homes were evaluated by a jury of international experts based on the monitored data of 12 days. Ridley et al. (2014) have utilized a monitoring system designed to measure the actual performance of two passive houses, another type of energy-efficient house with passive energy savings. Carutasiua et al. (2015) have studied the performance of a house built in accordance with the Passive House Institute (PHI) standards in Romania, with the heating system controlled by a smart building controller in order to achieve the nearly zero energy building standards. The house was equipped with an energy monitoring system, and the results showed that the energy used for space heating did not exceed the value imposed by the PHI, and the total energy consumption could be mitigated by the solar photovoltaic (PV) system. Li et al. (2016) have proposed a monitoring, analysis, and modelling framework for NZEHs, with sensors utilized to monitor detailed energy consumption and generation. Kazmi et al. (2016) have studied 46 homogeneous NZEB units, utilizing smart meters to monitor the power consumed by space heating and domestic hot water (DHW), and proposed algorithms for a control system to improve energy efficiency for DHW heating. Compared with the initial consumption, the results showed that a heuristic algorithm based control system could reduce the energy consumption for DHW by 20%. Franco and Fantozzi (2016) have used a data acquisition system to monitor a sustainable house, which was equipped with a ground source heat pump and a small-size solar PV plant, for the duration of one year of operation. Their results demonstrated that the amount of energy consumed is comparable to the amount of energy produced, and recommendations are proposed with regard to heat pumps for future design.

The application of advanced technology also contributes to improve the performance of building systems. Esen (2000) studied the thermal performance of a solar-aided heat pump system for space heating based on experiments and simulation. Esen and Esen (2005) investigated the influence of different refrigerants on the thermal performance of a two-phase thermosyphon solar collector under different conditions of environment and water load. Esen et al. (2007) compared from a techno-economic perspective a ground-coupled heat pump (GCHP) system with an air-coupled heat pump (ACHP) system for space cooling; they found the average cooling performance coefficients of the GCHP system for horizontal ground heat exchanger to be higher than that of the ACHP system, while the GCHP system was found to be more economical for space cooling. Esen et al. (2017) conducted modelling and experimental performance analysis of solar-assisted ground source heat pump system, with artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) used as modelling methods. The results showed ANFIS to be more successful than ANN in forecasting the performance of a solar ground source heat pump system.

The use of renewable energy and energy management are also crucial for NZEHs, and comprehensive research has been conducted within this domain. Amini et al. (2013) proposed a self-decision making method for reducing the peak load of a smart distribution network feeder in consideration of the upstream grid, distributed generation, and demand response resources. Amini et al. (2015) proposed and evaluated a system minimizing the cost of residential electricity in individual homes by adjusting electricity demand over a daily forecast price cycle. Boroojeni et al. (2016) presented a bi-level control framework for a highly reliable and large-scale smart distribution network with distributed renewable resources (DRR). At the first level, distributed community-level controllers utilizing the local storage units and DRRs were designed based on the stochastic model of demand and generation. At the second level, a global flow controller incorporating bulk generation units was used to enhance the reliability and to meet the residential demand with high probability. In order to reduce power losses, voltage fluctuations, charging and supply costs, and electric vehicle (EV) battery cost, Mozafar et al. (2017) proposed a hybrid Genetic Algorithm-Particle Swarm Optimization (GA-PSO) algorithm to optimize the allocation of renewable energy sources and electric vehicle charging stations simultaneously.

With technological advances and the introduction of policy incentives, NZEHs have seen considerable growth worldwide, including in the studied region. However, the actual performance of an NZEH may vary from the design objective, and the performance of a given NZEH may differ from other NZEHs. This research thus aims to examine the actual energy performance and identify the discrepancies in performance among multiple NZEHs. The research objectives include: (1) analyzing the actual energy performance of multiple NZEHs; (2) comparing the energy performance among multiple NZEHs by category; (3) identifying the variations and the reasons causing these differences with regard to the energy performance of multiple NZEHs; and (4) validating and comparing the monitored results with other systems and with the simulation results. Based on the analysis and comparison, the energy performance discrepancy of multiple NZEHs can be identified, which can be referenced to improve NZEH operation, and to conduct energy calibration for NZEH design. This research is conducted based on the actual NZEH projects in Calgary and Edmonton, Alberta, Canada, which were developed by Landmark Group of Companies. In these projects, grid-connected solar PV systems are employed for energy generation. This paper structure is organized as follows: section 2 presents the research methodology applied; section 3 introduces the design information of the case NZEHs; section 4 comprehensively reveals the actual energy performance of the monitored NZEHs and the results of analysis comparison; and section 5 summarizes this study and the future work. Based on the monitored data, this research presents the energy performance discrepancy among multiple NZEHs.

Section snippets

Methodology

The actual energy performance of multiple NZEHs is analyzed from various perspectives, based on the collected data using the monitoring system proposed by Li et al. (2016); the actual performance is also compared with that of simulated and the data from other monitoring systems, which serves as data validation. The proposed methodology is illustrated in Fig. 1: (1) The actual energy performance is analyzed in detail for each monitored NZEH; (2) the energy performance is compared among the

NZEH cases

Six NZEHs in Edmonton and Calgary, Alberta, Canada, are monitored and analyzed in this research, including three single family homes and one middle unit and two end units of a townhome. Among the six monitored NZEHs, four NZEHs yield complete annual data, and these are analyzed thoroughly in this paper and illustrated in Fig. 2-a and Fig. 2-b. The design summary of these NZEHs is displayed in Table 2: (1) electrical baseboard heaters are utilized for space heating in all the analyzed townhome

Overall energy performance analysis

The overall energy performance of NZEHs can be assessed by category of energy consumption, generation, and balance. The actual energy performance of the four monitored NZEHs with complete annual data is listed in Table 3, from which it can be observed that: (1) two NZEHs have energy deficit, and the other two encounter energy surplus; (2) the average annual energy consumption is 12,498 kWh; (3) the two townhome end units (labelled as “Edmonton 1” and “Edmonton 2”) yield nearly the same amount

Conclusion

In order to examine the actual energy performance and to identify discrepancies among multiple NZEHs, the energy performance of multiple NZEHs in a cold region is monitored using validated energy monitoring systems in this research. Complete annual data has been collected for four NZEHs to date, and the results show the average energy balance, excluding the NZEH with a period of non-occupancy (listed for sale), reaches −1.4%, which is near the net-zero target. The energy performance is analyzed

Acknowledgements

The authors are thankful to the Natural Sciences and Engineering Research Council of Canada (NSERC) and Landmark Group of Companies for their support of this research (Grant no. CRDPJ 444868-12).

References (29)

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