RETROFIT MEASURES TO APPROACH NET ZERO ENERGY STATUS FOR THE CANADIAN HOUSING STOCK : AIR TO WATER HEAT PUMP + PV

The aim of this paper is to present the impact of air to water heat pump (AWHP) and photovoltaic (PV) retrofit on the energy consumption and greenhouse gas (GHG) emissions of the Canadian housing stock. The study is conducted using the Canadian Hybrid Residential Enduse Energy and Emission model (CHREM). CHREM is based on the Canadian Single-Detached and Double/Row Database (CSDDRD), and utilizes the high resolution building energy simulation program ESP-r as its simulation engine. A suitable AWHP and PV system architecture for existing houses in the Canadian climate is selected. A numerical model for the selected architecture is developed using the available components in ESP-r. The model is applied to the houses eligible for AWHP and PV retrofit. The impact of AWHP and PV retrofit on electricity, oil, natural gas and wood consumption as well as the associated GHG emissions is estimated for each province. The results of this study will be used to develop strategies to convert existing Canadian houses into near/net zero energy buildings. INTRODUCTION The net zero energy building (NZEB) became a permanent part of the energy policy in many countries (Sartori et al., 2012). Since the energy saving market is not reacting rationally on the classic market forces, legislations and government incentives are likely the key parameters to promote energy efficiency in buildings (Tommerup & Svendsen, 2006). Legislation, codes and incentives regarding the energy efficiency in buildings are primarily planned at the municipal and provincial levels in Canada (Tobias & Vavaroutsos, 2012). Thus, smart strategies are required for massive conversion of existing houses in the Canadian housing stock (CHS) into NZEBs. Due to the complicated nature of the problem and the presence of several parameters including climatic and geographical conditions, energy prices, owner’s perception, greenhouse gas (GHG) emission reduction policy, technological barriers, various renewable energy supply options and grid interaction, such plans may be devised in municipal, provincial and national levels. To address energy consumption and GHG emissions of the residential sector in Canada a roadmap is required to encourage existing house owners to convert their houses into NZEB. Thus a subproject was defined under the Smart Net-zero Energy Buildings Strategic Research Network (SNEBRN) umbrella to define strategies and approaches for a net/near zero energy housing stock perspective. To achieve this goal suitable retrofits should be introduced in existing houses. The Canadian housing stock exhibits a high diversity in geometry and construction materials as well as heating, cooling and ventilation systems because of the wide range of climatic, geographical and economic conditions as well as the availability and price of fuels and energy sources in different regions. Thus the Building performance simulation is the most powerful tool to estimate the feasibility of retrofit options in existing houses across Canada. So far, a wide range of retrofit options including envelope modifications such as glazing and window shading upgrades, as well as installation of solar domestic hot water (SDHW) systems, phase change material (PCM) thermal energy storage, internal combustion engine (ICE) and Stirling engine (SE) based cogeneration systems and solar combisystem were studied (Asaee et al., 2015a; Asaee et al., 2015b; Asaee et al., 2015c; 2016b; Asaee et al., 2014; Nikoofard et al., 2013; 2014a; b; c). Energy saving and high energy efficiency technologies are essential components of any practical strategy for converting existing houses into NZEBs. An air to water heat pump (AWHP) system transfers aerothermal energy to water to deliver the required thermal energy for both space and domestic hot water heating from a single source. While the AWHP system is well established in Europe and Japan, it is relatively new to the Canadian market (CMHC-SCHL, 2015). Since the heat pump is an electricity driven system, an AWHP may reduce the energy consumption for space and DHW heating while increasing the electricity consumption of the household depending on the nature of the existing heating system. Thus, to reduce the impact of AWHP on electricity consumption, a photovoltaic (PV) solar system can be added to the retrofitted houses where practicable. A typical schematic of a house with a combined AWHP and PV system retrofit is presented in Figure 1. The PV modules are connected to a DC to AC inverter. PV generated electricity may be used to run the heat pump system including the compressor, pumps and auxiliary power for control devices as well as to provide electricity for appliances and lighting (AL). It is assumed that the houses can trade electricity with the utility at the same rate for import and export. Under these circumstances the grid becomes an infinite storage system for renewable electricity generated by the PV