A continued increase in both energy demand and greenhouse gas emissions (GHGs) call for utilising energy sources effectively. In comparison with traditional energy set-ups, micro-combined heat and power (micro-CHP) generation is viewed as an effective alternative; the aforementioned system’s definite electrical and thermal generation may be attributed to an augmented energy efficiency, decreased capacity as well as GHGs percentage. In this regard, organic Rankine cycle (ORC) has gained increasing recognition as a system, which is capable for generating electrical power from solar-based, waste heat, or thermal energy sources of a lower quality, for instance, below 120 °C. This study focuses on investigating a solar-based micro-CHP system’s performance for use in residential buildings through utilising a regenerative ORC. The analysis will focus on modelling and simulation as well as optimisation of operating condition of several working fluids (WFs) in ORC in order to use a heat source with low-temperature derived from solar thermal collectors for both heat and power generation. A parametric study has been carried out in detail for analysing the effects of different WFs at varying temperatures and flowrates from hot and cold sources on system performance. Significant changes were revealed in the study’s outcomes regarding performance including efficiency as well as power obtained from the expander and generator, taking into account the different temperatures of hot and cold sources for each WF. Work extraction carried out by the expander and electrical power had a range suitable for residential building applications; this range was 0.5–5 kWe with up to 60% electrical isentropic efficiency and up to 8% cycle efficiency for 50–120 °C temperature from a hot source. The operation of WFs will occur in the hot source temperature range, allowing the usage of either solar flat plate or evacuated tube collectors.

This paper presents a co-simulation platform which combines a building simulation tool with a Cyber-Physical Systems (CPS) approach. Residential buildings have a great potential of energy reduction by controlling home equipment based on usage information. A CPS can eliminate unnecessary energy usage on a small, local scale by autonomously optimizing equipment activity, based on sensor measurements from the home. It can also allow peak shaving from the grid if a collection of homes are connected. However, lack of verification tools limits effective development of CPS products. The present work integrates EnergyPlus, which is a widely adopted building simulation tool, into an open-source development environment for CPS released by the National Institute of Standards and Technology (NIST). The NIST environment utilizes the IEEE High Level Architecture (HLA) standard for data exchange and logical timing control to integrate a suite of simulators into a common platform. A simple CPS model, which controls local HVAC temperature set-point based on environmental conditions, was tested with the developed co-simulation platform. The proposed platform can be expanded to integrate various simulation tools and various home simulations, thereby allowing for co-simulation of more intricate building energy systems.

Residential energy consumption constitutes a significant portion of the overall energy consumption. There are significant amount of studies that target to reduce this consumption, and these studies mainly create mathematical models to represent and regenerate the energy consumption of individual houses. Most of these models assume that the residential energy consumption can be classified and then predicted based on the household size. As a result, most of the previous studies suggest that household size can be treated as an independent variable which can be used to predict energy consumption. In this work, we test this hypothesis on a large residential energy consumption dataset that also includes demographic information. Our results show that other variables like income, geographic location, house type, and personal preferences strongly impact energy consumption and decrease the importance of household size because the household size can explain only 26.55% of the electricity consumption variation across the houses.

The main purpose of this study is to investigate the feasibility of using a hybrid photovoltaic (PV), fuel cell (FC) and battery system to power different load cases, which are intended to be used at Al-Zarqa governorate in Jordan. All aspects related to the potentials of solar energy in Al-Hashemeya area were studied. The irradiation levels were carefully identified and analyzed, and found to range between 4.1–7.6 kWh/m 2 /day; these values represented an excellent opportunity for the photovoltaic solar system. Various renewable and non-renewable energy sources, energy storage methods and their applicability regarding cost and performance are discussed, in which HOMER (Hybrid Optimization for Electric Renewable) software is used as a sizing and optimization tool. Different scenarios with Photovoltaic slope, diesel price, and fuel cell cost were done. A remote residential building, school and factory having an energy consumption of 31 kWh/day with a peak of 5.3 kW, 529 kWh/day with a maximum of 123 kW and 608 kWh/day with a maximum of 67 kW respectively, were considered as the case studies’ loads. It was found that the PV-diesel generator system with battery is the most suitable solution at present for the residential building case, while the PV-FC-diesel generator-electrolyzer hybrid system with battery suites best both the school and factory cases. The load profile for each case was found to have a substantial effect on how the system’s power produced a scheme. For the residential building, PV panels contributed by about 75% of the total power production, the contribution increased for the school case study to 96% and dropped for the factory case to almost 50%.

Conventional residential building energy auditing needed to identify opportunities for energy savings is expensive and time consuming. On-site energy audits require quantification of envelope R-values, air and duct leakage, and heating and cooling system efficiencies. There is a need to advance lower cost automated approaches, which could include aerial and drive-by thermal imaging at-scale in an effort to measure the building R-value. However, single-point in time thermal images are generally qualitative, subject to errors stemming from building dynamics, background radiation, wind speed variation, night sky thermal radiation, and error in extracting temperature estimates from thermal images from surfaces with generally unknown emissivity. This work proposes two alternative approaches for estimating roof R-values from thermal imaging, one a physics based approach and the other a data-mining based approach. Both approaches employ aerial visual imagery to estimate the roof emissivity based on the color and type of roofing material, from which the temperature of the envelope can be estimated. The physics-based approach employs a dynamic energy model of the envelope with unknown R-value and thermal capacitance. These are tuned in order to predict the measured surface temperature at the time of the imaging, given the transient weather conditions prior to the imaging. The data-mining approach integrates the inferred temperature measurement, historical utility data, and easily accessible or potentially easily accessible housing data. A data mining regression model, trained from this data using residences with known R-values, is used to predict the roof R-value in the unknown houses. The data mining approach was shown to be a far superior approach, demonstrating an ability to estimate attic/roof R-value with an r-squared value of greater than 0.88 using as few as nine training houses. The implication of this research is significant, offering the possibility of auditing residences remotely at-scale via aerial and drive-by thermal imaging coupled with utility analysis.

In order to reduce CO 2 emissions in the residential sector, the installation of photovoltaics (PV) has been increasing extensively. However, such large-scale PV installations cause problems in the low-voltage distribution grid of the residential sector, such as PV related voltage surges. In this study, the utilization of suppressed PV output through energy storage devices was proposed. Using demand side energy storage devices reduces voltage surge, transmission loss, and CO 2 emissions from the residential buildings. The objective of this study was to add voltage constraints of the low-voltage distribution grid to an operational planning problem that we developed for the residential energy systems, and to quantitatively evaluate the potential of heat pump water heater (HP) to utilize the PV surplus electricity, while considering the electrical grid constraints based on the minimization of CO 2 emissions. We found that when a 4.5 kW HP with 370 L storage, which utilizes PV output, was added to the system, the reduction in CO 2 emissions was more than twice compared with that in the case of adding 4 kWh battery (BT) to a PV and gas fired water heater configuration. Further, the effect of utilizing the suppressed PV electricity by HP was almost equivalent to that by the BT. Therefore, the potential of HP in utilizing PV surplus electricity is higher than that of the BT in terms of CO 2 emissions reduction in the residential sector.

In this paper, passive cooling strategies have been investigated to evaluate their effectiveness in reducing cooling thermal loads and air conditioning energy consumption for residential buildings in Kingdom of Saudi Arabia (KSA). Specifically, three passive cooling techniques have been evaluated including: natural ventilation, downdraft evaporative cooling, and earth tube cooling. These passive cooling systems are applied to a prototypical KSA residential villa model with an improved building envelope. The analysis has been carried using detailed simulation tool for several cities representing different climate conditions throughout KSA. It is found that both natural ventilation and evaporative cooling provide a significant reduction in cooling energy for the prototypical villa located in Riyadh. Natural ventilation alone has reduced the cooling energy end-use by 22% and the total villa energy consumption by 10%, while the evaporative cooling system has resulted in 64% savings in cooling energy end-use and 32% in the total villa energy consumption. When applying both passive cooling systems together to the villa, the cooling energy end-use is significantly reduced by about 84.2% and the total villa energy savings by 62.3% relative to the un-insulated basecase residential building model. Moreover, natural ventilation is found to have a high potential in all KSA climates, while evaporative cooling can be suitable only in hot and dry climates such as Riyadh and Tabuk.

The design, construction, and operation of highly efficient residential buildings in hot and humid climates represent a unique challenge for architects, contractors, and building owners. In this paper, a case study on the performance of a residential building located in hot and humid location is presented. The building is a single-family house, which is modeled as a multi-zone building. The transient systems simulation program (TRNSYS) is used to simulate the building under Abu Dhabi’s typical meteorological year conditions. The results are presented in terms of the annual energy consumption and the indoor thermal comfort. The Predicted Mean Vote (PMV) is used to model the thermal comfort. In addition, the results of applying local building codes, Estidama, and international building codes, ASHRAE 90.2 and LEED, on the building’s performance are compared. The results will help in finding the effectiveness of these building standards in reducing the energy consumption of residential building in hot and humid regions.

This study determines the effects of cool roofs on a home’s energy use, specifically on heating and cooling energy end-uses. Representative cities were chosen for several ASHRAE US climate zones. A series of parametric simulations in EnergyPlus was carried out to assess the performance of cool roofs for selected prototypical residential building models using detailed simulation analysis. The simulation results are then correlated for each climate zone type to give an approximation of the best roof color per climate. The results are given based on total energy used as well as energy cost based on national average electricity and natural gas residential rates. This method allows builders and homeowners the choice between the most cost effective roofing type, and the most energy efficient in the case that they are not the same. Overall, it was found that in hot climates, it is more efficient to have a white roof, while a black roof benefits cooler climates. In mild and mixed climates, the effect of roof color was found rather are different for energy use and energy cost. Therefore the choice is determined by the owner’s requirements. In the cooler and milder climate zones, the analysis shows that the cost excess or savings is fairly small; usually under $10 difference per year. Hotter climates also have a relatively small effect, but more so than the cooler climates, with Phoenix especially showing a savings of $48.60 per year when a white roof is used over a black roof. Energy changes as low as only 4% in the as-built construction style, or as high as nearly 100% change in upgraded envelope cases were found. The study further finds that both the lack of an attic, and high efficiency envelopes increases the magnitude of the percent change in energy requirements.

A unique autonomous control system was developed to manage the HVAC components of a residence built specifically for an ultra-efficient home competition. Some of the home’s HVAC components that contribute to its ultra-efficiency (and necessitate such an autonomous controller) include multiple ductless mini-split heat pumps, multiple hydronic heated floor loops, multiple circulating ceiling fans, and a closed-loop solar thermal collection and storage system that not only provides hot water to the hydronic heated floors, but also supplies the home with domestic hot water. The autonomous controller integrates all this equipment with a mixture of technology that includes power-line communications, both wired and wireless TCP/IP network signals, low-voltage wiring, and infrared signals. By utilizing these many different methods to communicate with equipment around the home, the controller is able to simultaneously regulate components and systems that are often considered “stand alone” or impractical to implement in residential buildings due to their need for constant manual operation. The result is an HVAC system that consumes very little energy while still providing an expected level of comfort.

Heat pumps are commonly used for space-heating and cooling requirements. The combination of solar thermal and heat pump systems as a single solar-assisted heat pump (SAHP) system is a promising technology for offsetting domestic hot water, space-heating and cooling loads more efficiently. Task 44 of the Solar Heating and Cooling Programme of the International Energy Agency is currently investigating ways to optimize SAHP systems for residential use. This paper presents a review of past and current work conducted on SAHP systems. Specifically, the key performance data from many studies are highlighted and different system configurations are compared in order to establish insight towards which system configurations are suitable for the Canadian residential sector. It was found that the most suitable configuration for Canadian residential buildings depend on a combination of factors which may include occupant behavior, building characteristics, operation parameters, system components, the performance criteria of interest and climate. A large variety of configurations and parameters exist for SAHP systems and this made analyzing a specific system, comparing differing systems and establishing an optimal design fairly difficult. It was found that different authors used various different performance criterions and this inconsistency also added to the difficulty of comparing the studies of different systems. Overall, a standard performance criterion needs to be established for SAHP systems in order to meaningfully compare different configurations and determine optimal configurations for certain requirements.

The present work provides a feasibility analysis of a hybrid distributed generation system to meet the energy needs for residential communities in four locations in Mexico. Tuxtla Gutierrez (Oaxaca), Puerto Escondido (Oaxaca), Guaymas (Sonora) and Mexicali (Baja California Norte) were the four locations selected to assess the potential available energy resources in meeting cost-effectively and sustainably the electricity and thermal loads of small communities in Mexico. Electricity and thermal loads are obtained for the four locations by using calibrated building energy models for residential buildings in Mexico. Based on the feasibility analysis, it is found that while hybrid systems can reduce significantly CO 2 emissions, they are not cost-effective to implement in all locations due to the relatively cheap electricity costs from the only federal utility company in Mexico.

Due to extreme summers in the Desert Southwest region of the U.S., there are substantial peaks in electricity demand. Through a grant from the U.S. Department of Energy, a consortium has been formed between the University of Nevada Las Vegas, Pulte Homes, and NV Energy (formerly known as Nevada Power) to address this issue. The team has been developing a series of approximately 200 homes in Las Vegas to study substation level peak electric load reduction strategies. The targeted goal of the project is a peak reduction of more than 65%, between 1:00 PM and 7:00 PM, compared to code standard housing developments. Energy performances of the homes have been monitored and the results were stored for further analysis. A computer model has been developed for one of the homes in the new development using building energy simulation code, ENERGY 10. Influence of different peak reduction strategies on the electricity demand from the home has been analyzed using the developed model. The simulations predict that the annual electrical energy demand from the energy efficient home compared to a code standard home of the same size decreases by 38%. The simulations have also shown that the energy efficient measures reduce the electricity demand from the home during the peak periods. Simulations on the photovoltaic (PV) orientation show that a south oriented PV system is best suited for a home enrolled to flat electricity pricing schedule and a 220°(40° west of due south) orientation is economically optimal for homes enrolled in the time-of-use pricing. The energy efficiency methods in the building coupled with a 220° oriented PV and two degrees thermostat setback for three hours (from 3:00–6:00 PM) can reduce the peak demand by 62% compared to a code standard building of the same size.

Exergy is destroyed when work is degraded by friction and turbulence and when heat is transferred through finite temperature differences. Typical HVAC systems use a combination of high quality energy from combustion and electricity to overcome relatively small temperature differences between the building and the environment. It is possible to achieve the heating/cooling necessary to maintain comfort in a building without these high quality energy sources and their high potential-energy destruction. A low-exergy heating and cooling system seeks to better match the quality of energy to the loads of the building and thus to minimize exergy destruction and increase the exergetic efficiency of the building’s heating and cooling system. The method described here for low exergy building system design begins by minimizing overall heating and cooling loads using a tight, highly-insulated envelope and passive solar design strategies. Next a low-exergy heating and cooling system is designed that uses hydronic radiant heating and cooling in floors, along with high thermal mass. The large surface area of the floors enable low fluid flow rates and relatively small temperature differences to achieve heat transfer rates that would traditionally be driven by high temperature differentials and flows. The building uses a solar wall to passively drive ventilation requirements and earth tubes to condition the ventilation air. High thermal mass in the floor reduces peak loads and eliminates the need for solar thermal storage tanks. Thus, this paper begins to explore the practical limits of low-exergy design.

The present study investigates the feasibility, efficiency, and system design of a hybrid solar system generating electric power for stationary applications such as residential buildings. The system is fed by methanol and combines methanol steam reforming and Proton Exchange Membrane (PEM) fuel cells with solar collectors to generate the required heat for the steam reforming. The synergies of these technologies lead to a highly efficient system with significantly larger power densities compared to conventional systems and generate tremendous advantages in terms of installation and operation costs. The present investigation describes the entire proposed system and its components and presents first analytical, numerical, and experimental results of a larger project to prove the feasibility of such a system by analyzing first a bench test demonstrator generating around 10 W of electric power and finally a prototype for an entire single family household. It is shown that the methanol-to-electricity efficiency of the entire system is above 50%.

Heating Degree Days (HDDs), calculated from hourly weather data, are often used to estimate energy savings for a variety of energy efficiency measures (EEMs) to be applied to conditioned spaces in buildings. More specifically, application of HDDs is useful for estimating savings from weather-dependent EEMs. For first order estimation, it is often problematic to calculate HDDs for a given base temperature, when temperature setbacks are used in the conditioned spaces. This paper provides a set of correlations to characterize HDDs for selected ASHRAE Climate Zones as functions of three key parameters including the base temperature, setback temperature level (delta-T), and setback duration. In addition to the well-documented pattern of decreasing HDDs for decreasing base temperature, it was also shown that HDDs are inversely proportional to both setback duration and temperature setback differential levels. In the analysis presented in this paper, corrections to estimate HDDs when temperature setbacks are used for typical residential space heating schedules during unoccupied periods which occurred from 8 am to 5 pm Monday through Friday. In particular, regression correlations using two- and three-parameter models have been developed to estimate HDDs for multiple US locations that account for the impact of temperature setbacks on the heating requirements of residential buildings. For the two-parameter model, the input variables for the regression correlations are setback hours and delta T; for the three-parameter model, the input variables for the correlations include setback hours, delta T, and base temperature. The prediction accuracy for the energy savings, due to a set of EEMs, obtained from the HDD method —using the developed correlations— is tested against whole-building detailed energy simulation analysis for two single family homes. Detailed energy audits including utility data analysis have been carried out for both homes to calibrate the detailed simulation model and evaluate the effectiveness of the EEMs in reducing building energy use. The results from the detailed simulation analysis are then compared to those obtained from the HDD with temperature setbacks.

Cooling in residential buildings becomes more important due to the rising insulation requirements and the increasing human comfort. Therefore, systems that provide heating as well as cooling with a low primary energy consumption will be in future more preferred than conventional single-unit systems. Solar thermal installations can here provide in addition to the domestic hot water and heating demand a significant contribution to the cooling requirement in residential buildings. In this study, low-energy residential buildings with different solar heating and cooling systems are analyzed concerning their primary energy consumption. To cover a large range of different weather conditions, two locations (Madrid and Wu¨rzburg) with different solar energy supply are considered. Further, a conventional solar heating supply system including one or more typical room air-conditioners is as reference system selected. The different systems are modeled by the system simulation platform TRNSYS. In a first step, the question is addressed of whether a solar thermal system with standard dimensioning, taking the domestic hot water and heating demand into account, is sufficient to meet the cooling requirements. To cover the cooling demands, a small-scale thermally driven absorption chiller has been selected. In a next step, the studied systems are compared in terms of primary energy saving as a function of the solar cooling fraction. The simulation results have shown that regions with a high solar energy supply do not take advantage of solar thermal cooling, due to the higher cooling demand. On average, 70% of the cooling demands can be covered by a standard dimensioned solar thermal system. At the same time, a primary energy saving up to 90%, compared to currently installed room air-conditioning units can be achieved.

This paper summarizes the findings from a feasibility study of using renewable energy sources in combination with conventional power systems to meet the electrical requirements for an isolated island of Masirah in Oman. The study has been conducted to determine the best hybrid system to generate electrical energy needed for a small community of 500 residential buildings. A series of a simulation analyses have been carried out to evaluate and optimize different distribution technologies including photovolatics, wind and diesel for electrical generation in combination with storage batteries. It was found that the cost of energy could be reduced by as much as 48% compared to the cost for the baseline generation system currently used in the Masirah Island (i.e. diesel-driven generators). In particular, it was found that wind turbines in combination with storage batteries have a great impact in reducing the cost of generating electrical energy for the residential community. Moreover, solar PV panels were found unattractive under the current diesel price rates but could potentially become viable if the diesel prices increase. The paper outlines an optimal design for generating electricity for the community at lowest cost while minimizing carbon emissions.

A method is presented to determine energy performance of residential buildings. The method is based on an extended application of the degree-days basis to determine building thermal performance. The overall heat transfer coefficient and radiation shading factors are extracted from nightime and daytime readings of indoor and outdoor temperatures, solar radiation, and total energy usage of the building. It is shown that the overall heat transfer coefficient (thermal response) UA of the building is linear. Radiation shading factors can be represented as nonlinear functions of time. Application of the method to estimate real-time energy performance and carbon offsets of high performance buildings is discussed. The performance of the building is compared with an equivalent building with standard physical and thermal characteristics.

This paper summarizes the results of a detailed energy analysis carried out for a typical Colorado residence using three different HVAC systems for 10 distinct locations in Colorado. The HVAC systems considered in the analysis include: • 78% efficient furnace with a 13 SEER air conditioner; • Vertical well ground source heat pump with a heating COP of 3.5 and a cooling EER of 17.1; • Slinky ground source heat pump with a heating COP of 3.5 and a cooling EER of 17.1. The results of the analysis indicate that relative to the conventional systems, ground source heat pumps (GSHPs) offer several benefits including lower annual energy costs, electrical peak demand, and carbon emissions. However, GSHPs use more electrical energy use. Specifically, it was found that relative to a 78 AFUE furnace / 13 SEER AC system, in all locations both GSHPs, vertical well and slinky, show on average a 41.2% increase in electricity use, a 10% decrease in energy cost, a 4.5% decrease in CO 2 emissions, and a 16.8% average decrease in peak summer electric demand.