Electrical-end-use data from 23 houses sampled each minute for simulating micro-generation systems

An improved understanding of the consumption patterns, end-uses, and temporal variations of electrical loads in houses is warranted because a significant fraction of a society's total electricity consumption occurs within residential buildings. In general, there is a lack of high-temporal-resolution data describing occupant electrical consumption that are available to researchers in this field. To address this, new measurements were performed and combined with data emanating from an earlier study to provide a database of annual measurements for 23 houses at a 1-min resolution that characterizes whole-house, non-HVAC, air conditioner, and furnace fan electrical draws, as well as the draw patterns of some major appliances. All houses were located in Ottawa, Canada. The non-HVAC measurements of this 23-house sample were shown to be in agreement with published estimates for the housing stock. The furnace fan was found to be the most significant end-use. These high-temporal-resolution data of electrical demands in houses can be used by researchers to increase the fidelity of building performance simulation analyses of different micro-generation technologies in residential buildings

Techno-economic assessment of photovoltaic (PV) and building integrated photovoltaic/thermal (BIPV/T) system retrofits in the Canadian housing stock

Techno-economic impact of retrofitting houses in the Canadian housing stock with PV and BIPV/T systems is evaluated using the Canadian Hybrid End-use Energy and Emission Model. Houses with south, south-east and south-west facing roofs are considered eligible for the retrofit since solar irradiation is maximum on south facing surfaces in the northern hemisphere. The PV system is used to produce electricity and supply the electrical demand of the house, with the excess electricity sold to the grid in a net-metering arrangement. The BIPV/T system produces electricity as well as thermal energy to supply the electrical as well as the thermal demands for space and domestic hot water heating. The PV system consists of PV panels installed on the available roof surface while the BIPV/T system adds a heat pump, thermal storage tank, auxiliary heater, domestic hot water heating equipment and hydronic heat delivery system, and replaces the existing heating system in eligible houses. The study predicts the energy savings, GHG emission reductions and tolerable capital costs for regions across Canada. Results indicate that the PV system retrofit yields 3% energy savings and 5% GHG emission reduction, while the BIPV/T system yields 18% energy savings and 17% GHG emission reduction in the Canadian housing stock. While the annual electricity use slightly increases, the fossil fuel use of the eligible houses substan

Micro-cogeneration versus conventional technologies: Considering model uncertainties in assessing the energy benefits

Fuel cells with nominal outputs of approximately 1kW AC are emerging as a prime-mover of a micro-cogeneration system potentially well-suited to compete, on an energy basis, with conventional methods for satisfying occupant electrical and thermal demands in a residential application. As the energy benefits of these systems can be incremental when compared to efficient conventional methods, it is especially important to consider the uncertainties of the models on which simulation results are based. However, researchers have yet to take this aspect into account.This article makes a contribution by demonstrating how these model uncertainties may be propagated to the simulation results of a micro-cogeneration system for comparison to a reference scenario using a case study. This case study compares the energy performance of a fuel-cell based micro-cogeneration system serving only domestic hot water demands to an efficient reference scenario where the conventional methods for providing electrical and thermal demands are considered to be a central gas-fired combined-cycle plant and a condensing tankless water heater respectively. The simulation results demonstrated that if model uncertainties were ignored, it would have been possible to demonstrate that the considered micro-cogeneration system was more efficient than the reference scenario for average consumption levels of domestic hot water. However, when model uncertainties were considered, the efficiency of the considered micro-cogeneration system could not reliably exceed that of the reference scenario by serving the domestic hot water needs of a single-family home

Adaptation and validation of an existing bottom-up model for simulating temporal and inter-dwelling variations of residential appliance and lighting demands

The design and analysis of community-scale energy systems and incentives is a non-trivial task. The challenge of such undertakings is the well-documented uncertainty of building occupant behaviours. This is especially true in the residential sector, where occupants are given more freedom of activity compared to work environments. Further complicating matters is the dearth of available measured data. Building performance simulation tools are one approach to community energy analysis, however such tools often lack realistic models for occupant-driven demands, such as appliance and lighting (AL) loads. For community-scale analysis, such AL models must also be able to capture the temporal and inter-dwelling variation to achieve realistic estimates of aggregate electrical demand. This work adapts the existing Centre for Renewable Energy Systems Technology (CREST) residential energy model to simulate Canadian residential AL demands. The focus of the analysis is to determine if the daily, seasonal, and inter-dwelling variation of AL demands estimated by the CREST model is realistic. An in-sample validation is conducted on the model using 22 high-resolution measured AL demand profiles from dwellings located in Ottawa, Canada. The adapted CREST model is shown to broadly capture the variation of AL demand variations observed in the measured data, however seasonal variation in daily AL demand behaviour was found to be under-estimated by the model. The average and variance of daily load factors was found to be similar between measured and modelled. The model was found to under-predict the daily coincidence factors of aggregated demands, although the variance of coincident factors was shown to be similar between measured and modelled. A stochastic baseload input developed for

Techno-economic assessment of solar assisted heat pump system retrofit in the Canadian housing stock

The techno-economic feasibility of retrofitting existing Canadian houses with solar assisted heat pump (SAHP) is investigated. The SAHP architecture is adopted from previous studies conducted for the Canadian climate. The system utilizes two thermal storage tanks to store excess solar energy for use later in the day. The control strategy is defined in order to prioritise the use of solar energy for space and domestic hot water heating purposes. Due to economic and technical constraints a series of eligibility criteria are introduced for a house to qualify for the retrofit. A model was built in ESP-r and the retrofit was introduced into all eligible houses in the Canadian Hybrid Residential End-Use Energy and GHG Emissions model. Simulations were conducted for an entire year to estimate the annual energy savings, and GHG emission reductions. Results show that the SAHP system performance is strongly affected by climatic conditions, auxiliary energy sources and fuel mixture for electricity generation. Energy consumption and GHG emission of the Canadian housing stock can be reduced by about 20% if all eligible houses receive the SAHP system retrofit. Economic analysis indicates that the incentive measures will likely be necessary to promote the SAHP system in the Canadian residential market

Techno-economic feasibility evaluation of air to water heat pump retrofit in the Canadian housing stock

This study was conducted to assess the techno-economic feasibility of converting the Canadian housing stock (CHS) into net/near zero energy buildings by introducing and integrating high efficient and renewable/alternative energy technologies in new construction and existing houses. Performance assessment of energy retrofit and renewable/alternative energy technologies in existing houses in regional and national scale is necessary to devise feasible strategies and incentive measures. The Canadian Hybrid Residential End-Use Energy and GHG Emissions model (CHREM) that utilizes a bottom-up modeling approach is used to investigate the techno-economic feasibility of air to water heat pump retrofit in the Canadian housing stock. The proposed energy retrofit includes an air to water heat pump, auxiliary boiler, thermal storage tank, hydronic heat delivery and domestic hot water (DHW) heating. Energy savings, GHG emission changes and economic feasibility of the air source heat pump retrofit are considered in this study. Results show that there is a potential to reduce 36% of energy consumption and 23% of GHG emissions of the CHS if all eligible houses undertake the retrofit. Economic analysis indicates that the feasibility of air to water heat pump systems is strongly affected by the current status of primary energy use for electricity generation and space and DHW heating as well as energy prices and economic conditions. Legislation, economic incentives and education for homeowners are necessary to enhance the penetration level of air to water heat pump retrofits in the CHS

On predicting the magnitude and temporal variation of cooling loads in detached residential buildings

The rapid growth in residential air conditioning (cooling) in many parts of the world is resulting in increased energy consumption, significantly affecting central electricity systems, and having adverse environmental consequences. Alternatives to conventional electrically powered vapour-compression air conditioning are emerging. Building performance simulation can be used to assess their feasibility and guide their development, but only if it can accurately characterize the magnitude and temporal variation of cooling loads, including the impact of architectural and site variables (e.g. annual weather changes) as well as the impact of occupant behaviour and interventions (e.g. setpoint temperatures, window shading, window openings). This paper demonstrates how building performance simulation can be employed to study the impact of these factors upon seasonal as well as peak daily cooling loads

Learning the fundamentals of building performance simulation through an experiential teaching approach

It is relatively easy to train architects and engineers to operate BPS tools and to produce results, but there is considerable evidence to show that it is quite difficult to produce accurate results, even for experienced users. I believe that BPS suffers from a credibility gap and that its full potential will only be realized once we adequately prepare users to effectively apply tools with full knowledge of their applicability, modelling limitations, and default methods and data, and provide them the skill set to scrutinize their results. An experiential approach for teaching the fundamentals of BPS through a learning spiral composed of four modes of learning has been devised. The approach and the learning outcomes that have been achieved through each of the learning modes are demonstrated in this article through examples extracted from the teaching of a semester-long post-graduate course

Algorithm for calculating convection coefficients for internal building surfaces for the case of mixed flow in rooms

The treatment of convective heat transfer at internal building surfaces has a significant impact on the simulation of heat and air flow. Accurate approaches for the range of flow regimes experienced within buildings (buoyant flow adjacent to walls, buoyant plumes rising from radiators, fan-driven flows, etc.) are required, as is the ability to select an appropriate method for the case at hand and to adapt modelling to changes in the flow. A new approach - drawing upon previously published methods - has been developed for modelling mixed convection within mechanically ventilated rooms. It is applicable for rooms ventilated with ceiling mounted diffusers and is appropriate for both heating and cooling. ESP-r simulations performed with the mixed flow model indicate that the prediction of heating and cooling loads is highly sensitive to the treatment of surface convection and that significant errors can result if an inappropriate model is employed. The results also reveal that the choice of convection algorithm can influence design decisions drawn from a simulation-based analysis

The empirical validation of a model for simulating the thermal and electrical performance of fuel cell micro-cogeneration devices

Fuel cell micro-cogeneration is a nascent technology that can potentially reduce the energy consumption and environmental impact associated with serving building electrical and thermal demands. Accurately assessing these potential benefits and optimizing the integration of micro-cogeneration within buildings requires simulation methods that enable the integrated modelling of fuel cell micro-cogeneration devices with the thermal and electrical performance of the host building and other plant components. Such a model has recently been developed and implemented into a number of building simulation programs as part of an International Energy Agency research project. To date, the model has been calibrated (tuned) for one particular prototype 2.8 kWAC solid-oxide fuel cell (SOFC) micro-cogeneration device. The current paper examines the validity of this model by contrasting simulation predictions to measurements from the 2.8 kWAC prototype device. Good agreement was found in the predictions of DC power production, the rate of fuel consumption, and energy conversion efficiencies. Although there was greater deviation between simulation predictions and measurements in the predictions of useful thermal output, acceptable agreement was found within the uncertainty of the model and the measurements. It is concluded that the form of the mathematical model can accurately represents the performance of SOFC micro-cogeneration devices and that detailed performance assessments can now be performed with the calibrated model to examine the applicability of the 2.8 kWAC prototype device for supplying building electrical and thermal energy requirements