Annual Building Research Articles

Building energy use in China: Ceiling and scenario

With increasing levels of urbanization and a growing economy, total building energy use in China is rapidly increasing. However, energy use must be controlled due to limited energy supply and the goal of lowering carbon emissions. This study tried to define a reasonable limit for total energy use in China, and, more specifically, a target for building energy use. Domestic energy production, energy imports, and the need to reduce CO2 emissions and fossil fuel combustion were considered when analyzing the available energy for China. The current status and future trends of energy use by industry, building, and transportation sectors were analyzed to determine how much energy the building sector can use considering economic growth and improving living conditions. Within the framework of “Ecological civilization,” this study suggests that annual building energy use in China has to be limited to no more than 1 billion tce.

Comparing Whole Building Energy Implications of Sidelighting Systems with Alternate Manual Blind Control Algorithms

Currently, there is no manual blind control guideline used consistently throughout the energy modeling community. This paper identifies and compares five manual blind control algorithms with unique control patterns and reports blind occlusion, rate of change data, and annual building energy consumption. The blind control schemes detailed here represent five reasonable candidates for use in lighting and energy simulation based on difference driving factors. This study was performed on a medium-sized office building using EnergyPlus with the internal daylight harvesting engine. Results show that applying manual blind control algorithms affects the total annual consumption of the building by as much as 12.5% and 11.5% for interior and exterior blinds respectively, compared to the Always Retracted blinds algorithm. Peak demand was also compared showing blind algorithms affected zone load sizing by as much as 9.8%. The alternate algorithms were tested for their impact on American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) Guideline 14 calibration metrics and all models were found to differ from the original calibrated baseline by more than the recommended ±15% for coefficient of variance of the mean square error (CVRMSE) and ±5% for normalized mean bias error (NMBE). The paper recommends that energy modelers use one or more manual blind control algorithms during design stages when making decisions about energy efficiency and other design alternatives.

Multi-linear Regression Models to Predict the Annual Energy Consumption of an Office Building with Different Shapes

The present study describes the development of a multi-linear regression model to predict the effect of building shape on total energy consumption in two different climate regions (i.e. cold-dry and warm-marine). Seven building shapes including H-shape, T-shape, rectangle, etc. were considered in this study. The simplified model can be used to conduct a parametric study in order to investigate the effect of building parameters on total heating and cooling load. Building simulation software programs, including eQUEST and DOE-2 were used to build and simulate individual building configuration that were generated using Monte Carlo simulation techniques. Ten thousand simulations for seven building shapes were performed to create a comprehensive dataset covering the full ranges of design parameters. Statistical analysis was performed using R statistical analysis program to develop a set of linear regression equations predicting energy consumption of each design scenario. In addition, the influence of several design parameters on building energy consumption was further investigated using the sensitivity analysis procedure. The difference between regression-predicted and DOE-2 simulated annual building energy consumption were largely within 5%. It is envisioned that the developed regression models can be used to estimate the total energy consumption in the early stages of the design when different building schemes and design concepts are being considered.

Development of Inverter Centrifugal Refrigerator Model with extrapolability for Purpose of Annual Building Energy Simulation

Development of Inverter Centrifugal Refrigerator Model with extrapolability for Purpose of Annual Building Energy Simulation

KivaTM: a numerical framework for improving foundation heat transfer calculations

KivaTM was developed to evaluate the energy performance of building foundation designs. This free, open-source tool can be integrated into existing annual building energy simulation software tools. This article describes the verification of Kiva's six numerical solution methods against the International Energy Agency Building Energy Simulation Test and Diagnostic Method test cases for slab-on-grade heat conduction. Comparisons of accuracy, computation time and stability between the numerical solution methods revealed their advantages and disadvantages. While each solution method satisfactorily approximates slab heat loss, many methods exhibited stability issues or required substantially longer computation time. The method least affected by these two challenges was the alternating-direction implicit (ADI) method. Kiva features four approaches of initializing the soil temperatures for an annual simulation. A new accelerated initialization approach is shown to reduce the required years of pre-simulation. The combination of the ADI method and accelerated initialization reduces the total computation time by 95% relative to the traditional implicit solutions.

Impacts of climate change on energy consumption and peak demand in buildings: A detailed regional approach

This paper presents the results of numerous commercial and residential building simulations, with the purpose of examining the impact of climate change on peak and annual building energy consumption over the portion of the EIC (Eastern Interconnection) located in the United States. The climate change scenario considered includes changes in mean climate characteristics as well as changes in the frequency and duration of intense weather events. Simulations were performed using the BEND (Building ENergy Demand) model which is a detailed building analysis platform utilizing EnergyPlus™ as the simulation engine. Over 26,000 building configurations of different types, sizes, vintages, and characteristics representing the population of buildings within the EIC, are modeled across the three EIC time zones using the future climate from 100 target region locations, resulting in nearly 180,000 spatially relevant simulated demand profiles for three years selected to be representative of the general climate trend over the century. This approach provides a heretofore unprecedented level of specificity across multiple spectrums including spatial, temporal, and building characteristics. This capability enables the ability to perform detailed hourly impact studies of building adaptation and mitigation strategies on energy use and electricity peak demand within the context of the entire grid and economy.

Foundation heat transfer analysis for buildings with thermal piles

Thermal piles or thermo-active foundations utilize heat exchangers embedded within foundation footings to heat and/or cool buildings. In this paper, the impact of thermal piles on building foundation heat transfer is investigated. In particular, a simplified analysis method is developed to estimate the annual ground-coupled foundation heat transfer when buildings are equipped with thermal piles. First, a numerical analysis of the thermal performance of thermo-active building foundations is developed and used to assess the interactions between thermal piles and slab-on-grade building foundations. The impact of various design parameters and operating conditions is evaluated including foundation pile depth, building slab width, foundation insulation configuration, and soil thermal properties. Based on the results of a series of parametric analyses, a simplified analysis method is presented to assess the impact of the thermal piles on the annual heat fluxes toward or from the building foundations. A comparative evaluation of the predictions of the simplified analysis method and those obtained from the detailed numerical analysis indicated good agreement with prediction accuracy lower than 5%. Moreover, it is found that thermal piles can affect annual building foundation heat loss/gain by up to 30% depending on foundation size and insulation level.

Study on Operation Strategies of a Hybrid Ground-Source Heat Pump System with Surface Water Heat Exchangers for an Exhibition Building

In this study, a hybrid ground-source heat pump (GSHP) system with surface water heat exchangers is employed in an exhibition building in Shanghai to provide with high-efficiency energy for space cooling and heating and also solve the problem of thermal imbalance of the soil because of a significant imbalance between the annual heat rejection to the ground and the annual heat extraction from the ground. The operation strategies were put forward based on the annual building hourly load to make the hybrid GSHP system in a high-efficiency status during the long-term operation. The results show that the hybrid GSHP system can effectively solve the heat accumulation problem and decrease in system performance for the ten-year long run.

Building thermal energy modeling with loss minimization

The thermal losses in buildings are significant energy sinks. The Energy Semantic Network (ESN) is a new method for finding these losses at the design stage, as well as for the existing structures. The research purpose of ESN is to take into consideration the governing factors of building thermal performance (i.e. the insulation materials, the dimensions, the loads, and the schedules of people interactions), associate these factors with any building of choice, and to subject the model to range of dynamical changes, that will help to make the decisions for improving the building thermal performance. The current work is only an early stage on ESN, the end goal of ESN is to evaluate the thermal energy conservation technologies with respect to the dynamical thermal changes, and track the dominant sinks resulting from these changes. Currently, the energy conservation technologies present an opportunity for reducing the utility use, and, thereby, the savings in capital for long term performance. The thermal energy conservation problems are unique to every building, due to the storage and the supply of the energy in response to the seasonal demands, structure, and the nature of the building utilization (the involvement of people). With the current simulation software, such as Energy Plus, there exists a convenient way of simulating the annual building performance, without the tediousness of monitoring the physical building. However, in that case, any particular spontaneous effects may not be completely accounted. The ESN structure is intended to make up for the spontaneous effects, and be accountable for possible spikes in the energy use that may occur throughout the year. Such spikes in energy consumption do not have to be singular, because it is possible to assign an array of situations where energy losses occur and track them to the specific location. The use of ESN for tracking the energy losses can lead to a solution for preventing similar spikes in the future by isolating the most significant sink. The enclosed research on the ESN method includes the foundations of ESN, the case study of a hypothetical hotel located in Ontario, and a detailed Simulink representation of ESN.

Simulation Analysis on Sun-Shading Design Case of Buildings in Cold Regions

The sun-shading design was carried out based on a comprehensive building in a cold region. The reasonable building sun-shading design method in combination with the regional and facade characteristics in the cold regions is discussed, meanwhile, the unit-area refrigeration power consumption of the room and the annual building energy consumption before and after sun-shading setting are analyzed with simulation software. It is proposed that in the cold regions, designing sun-shading reasonably can reduce air conditioners energy consumption in summer, improve the indoor thermal environment and increase the indoor comfort level. This research can provides a technical reference to promote the sun-shading and building integration design and application in the cold regions.

Gas Stirling engine μCHP boiler experimental data driven model for building energy simulation

A dynamic model for the simulation of gas micro combined heat and power devices (μCHP boilers) has been developed in order to assess their energy performances. From a literature review and experimental investigations, the new model is designed with the aim of limiting the number of parameters which need to be easily accessible in order to be suitable with annual building energy simulations. At first, this paper focuses on the description of the μCHP boiler which has been tested, on the development of the test bench and on the experimental results. Then, it focuses on the model description, on its parameterization and on its validation. The modelling approach is based on an energy balance on the device and on empirical expressions for the main inputs and outputs. The model characterizes the μCHP boiler behaviour for different inlet water flow rates and temperatures. The dynamic phases with the start-up and cooling phases are taken into account. Finally, the models for the Stirling engine and the additional boiler are limited respectively to 28 and 24. Further experimental investigations led to simplify the μCHP model from 28 to 17 parameters without reducing the accuracy.

Study on energy saving possibility of digital variable multiple air conditioning system in three office buildings in Shanghai

The objective of this paper was to study energy saving possibility of DVM air conditioning system compared to all-air system with constant air volume and primary air fan-coil system. Three office buildings are selected to study the impact of outdoor air temperature and air-conditioning load on energy consumption of the above three systems. eQUEST was used to simulate the annual building performance. The simulation results indicate that energy saving potentiality of DVM air conditioning system is significant under part load condition because of its indoor unit independently controlled characteristic and good regulating characteristics; for office building with boundary condition in standard GB 50189-2005, energy saving potentiality of DVM air conditioning system is significant when building area is less than 20,000 m2, or primary air fan-coil system with two sets of water source screw chiller is more available.

Coupling simulation system of annual building energy and microclimate

We have developed a simulation system for a year-round assessment of environmental comfort, energy conservation, and CO2 emissions in buildings and street blocks where active utilization of sunshine, vegetation and solar energy resources is fully considered. An analysis model has been constructed for handling interactions between highly complex street-block wide solar radiation patterns and building air-conditioning load. As a demonstration case of the present system, coupled solar radiation-thermal load analysis for an eleven-story office building has been performed. By comparing the result of a building located in a city block with a reference case of a self-standing building, the proper arrangement of buildings and spaces such as solar reflectance of building surface may be proposed.

Integrating probabilistic methods for describing occupant presence with building energy simulation models

This paper presents a method for developing a probabilistic-based occupancy model that focuses on occupants’ long vacancy activities (greater than 1 week) and other potential building underutilization that is further integrated with a building energy simulation model. The combined model is then applied toward an existing Leadership in Energy and Environmental Design (LEED) certified military dormitory and later compared with corresponding values from the energy model's original prediction as well as actual building energy data. The occupancy model simulates annual building occupancy rates comprised of weekly values based on the frequency, duration, and seasonality of occupants’ long vacancy activities. The energy model uses the simulated occupancy rates to yield the building's predicted range of energy performance. Applying the combined model to the existing LEED building resulted in an improved, predicted Energy Use Intensity (EUI) mean value of 612MJ/m2 as compared to the original model and actual EUI values of 691 and 590, respectively. While the model also demonstrated its utility in describing the change in predicted performance over a range of probabilities associated with certain long vacancy activities, efforts to incorporate other occupant behavior-related aspects such occupant schedules and thermal set points could further improve modeling efforts.

Electric storage in California’s commercial buildings

Most recent improvements in battery and electric vehicle (EV) technologies, combined with some favorable off-peak charging rates and an enormous PV potential, make California a prime market for electric vehicle as well as stationary storage adoption. However, EVs or plug-in hybrids, which can be seen as a mobile energy storage, connected to different buildings throughout the day, constitute distributed energy resources (DER) markets and can compete with stationary storage, onsite energy production (e.g. fuel cells, PV) at different building sites. Sometimes mobile storage is seen linked to renewable energy generation (e.g. PV) or as resource for the wider macro-grid by providing ancillary services for grid-stabilization. In contrast, this work takes a fundamentally different approach and considers buildings as the main hub for EVs/plug-in hybrids and considers them as additional resources for a building energy management system (EMS) to enable demand response or any other building strategy (e.g. carbon dioxide reduction). To examine the effect of, especially, electric storage technologies on building energy costs and carbon dioxide (CO2) emissions, a distributed-energy resources adoption problem is formulated as a mixed-integer linear program with minimization of annual building energy costs or CO2 emissions. The mixed-integer linear program is applied to a set of 139 different commercial building types in California, and the aggregated economic and environmental benefits are reported. To show the robustness of the results, different scenarios for battery performance parameters are analyzed. The results show that the number of EVs connected to the California commercial buildings depend mostly on the optimization strategy (cost versus CO2) of the building EMS and not on the battery performance parameters. The complexity of the DER interactions at buildings also show that a reduction in stationary battery costs increases the local PV adoption, but can also increase the fossil based onsite electricity generation, making an holistic optimization approach necessary for this kind of analyses.

Commercial building energy use in six cities in Southern China

With China’s continuing economic growth, the percentage of government offices and large commercial buildings has increased tremendously; thus, the impact of their energy usage has grown drastically. In this survey, a database with more than 400 buildings was created and analyzed. We researched energy consumption by region, building type, building size and vintage, and we determined the total energy use and performed end use breakdowns of typical buildings in six cities in southern China. The statistical analysis shows that, on average, the annual building electricity use ranged from 50 to 100kWh/m2 for office buildings, 120 to 250kWh/m2 for shopping malls and hotels, and below 40kWh/m2 for education facilities. Building size has no direct correlation with building energy intensity. Although modern commercial buildings built in the 1990s and 2000s did not use more energy on average than buildings built previously, the highest electricity intensive modern buildings used much more energy than those built prior to 1990. Commercial buildings in China used less energy than buildings in equivalent weather locations in the US and about the same amount of energy as buildings in India. However, commercial buildings in China provide comparatively less thermal comfort than buildings in comparable US climates.

Study on the Ventilation and Dehumidification System Integration Framework for City Buildings in Hot Summer and Cold Winter Zone

Building ventilation has typical regional characteristics, due to its annual high wet climate characteristics in hot summer and cold winter area, the choice of ventilation type is especially important. The present building energy consumption simulation and thermal comfort evaluation of is inadequate to air humidity effects, and easily to ignore ventilation energy saving potential with building thermal environment control. In this paper based on the region annual building humidity environment characteristic, author put forward a kind of building ventilation and dehumidification integrated solutions, from a methodological point of view to explore a ventilation and dehumidification integrated technique with air conditioning and heating period , try to deal with the indoor thermal environment quality problems with lower energy consumption.

Optimal Planning and Operation of Smart Grids with Electric Vehicle Interconnection

Connection of electric storage technologies to smartgrids will have substantial implications for building energy systems. Local storage will enable demand response. When connected to buildings, mobile storage devices such as electric vehicles (EVs) are in competition with conventional stationary sources at the building. EVs can change the financial as well as environmental attractiveness of on-site generation (e.g. PV or fuel cells). In order to examine the impact of EVs on building energy costs and CO2 emissions, a distributed-energy-resources adoption problem is formulated as a mixed-integer linear program with minimization of annual building energy costs or CO2 emissions and solved for 2020 technology assumptions. The mixedinteger linear program is applied to a set of 139 different commercial buildings in California and example results as well as the aggregated economic and environmental benefits are reported. Special constraints for the available PV, solar thermal, and EV parking lots at the commercial buildings are considered. The research shows that EV batteries can be used to reduce utility-related energy costs at the smart grid or commercial building due to arbitrage of energy between buildings with different tariffs. However, putting more emphasis on CO2 emissions makes stationary storage more attractive and stationary storage capacities increase while the attractiveness of EVs decreases. The limited availability of EVs at the commercial building decreases the attractiveness of EVs and if PV is chosen by the optimization, then it is mostly used to charge the stationary storage at the commercial building and not the EVs connected to the building.

Evaluation of weather datasets for building energy simulation

In recent years, calibrated energy modeling of residential and commercial buildings has gained importance in a retrofit-dominated market. Accurate weather data play an important role in this calibration process and projected energy savings. It would be ideal to measure weather data at the building location to capture relevant microclimate variation but this is generally considered cost-prohibitive. There are data sources publicly available with high temporal sampling rates but at relatively poor geospatial sampling locations. To overcome this limitation, there are a growing number of service providers that claim to provide real time and historical weather data necessary for building modeling at 15–40km2 grid across the globe; common variables such as temperature and precipitation have been constructed on ∼1km2 grids [1]. Unfortunately, there is limited documentation from 3rd-party sources attesting to the accuracy of this data. This paper compares provided weather characteristics with data collected from a weather station inaccessible to the service providers. Monthly average dry bulb temperature; relative humidity; direct normal, diffuse and global solar radiation; wind speed and wind direction are statistically compared. Moreover, we ascertain the relative contribution of each weather variable and its impact on building loads. Annual simulations are performed for three different building types, including a closely monitored and automated energy efficient research building. The comparison shows that the difference for an individual variable can be as high as 90%. In addition, annual building energy consumption can vary by ±7% while monthly building loads can vary by ±40% as a function of the provided location's weather data.

Dynamic thermal circuit modelling with distribution of internal solar radiation on varying façade orientations

This paper aims at introducing an improved methodology for the dynamic modelling of buildings by the thermal networks method. This methodology employs, as a tool, the commonly used ASHRAE clear sky model to allow for the calculation of the external façade radiation and the distribution of the penetrating solar flux on the internal surface-nodes of the zone. The zone considered has an entirely glazed façade with a varying type of glazing and its enclosure is a rectangle parallelipipedic. The incident solar radiation is determined for building surface azimuths ranging from east to west in 45° step increments. The mathematical formulation of this solar-angle dependent lumped capacitance thermal model is based on the nodal approach and is updated in 15min time increments. The proposed methodology provides more insight to help understand the impact of opaque and glazed façade orientations and layer-formation on energy consumption. Results from annual energy performance calculations vs glazed-façade orientation, for various glazing systems, are given for a building zone location in the Mediterranean region. Depending on the building façade orientation and climatic conditions, proper selection of the type of glazing can reduce the annual building energy consumption.