Building Simulation Programs Research Articles

Environmental benefits of sustainable chiller system under climate change

Chiller systems are commonly used to provide cooling energy in commercial buildings but with considerable electricity and water consumption. This paper discusses the environmental benefits of a sustainable chiller system with full variable speed control under climate change. Hourly weather data of climate change scenarios in 2020, 2050 and 2080 were predicted by using the program CCWorldWeatherGen, based on a typical meteorological year weather file for Hong Kong. The building simulation program EnergyPlus was used to model a full variable speed chiller system and a conventional system operating for a reference office building. Simulation results show that the environmental performance of the sustainable system is superior to the conventional ones with annual electricity saving of 25.7–31.5%, water saving of 1.8–2.2% and carbon emissions reduction of 25.6–30.3% under the three climate change scenarios. The sustainable system would bring an improvement in the annual average coefficient of performance even ...

Simulation of energy saving potential of a centralized HVAC system in an academic building using adaptive cooling technique

Application of adaptive comfort temperature as room temperature set points potentially reduce energy usage of the HVAC system during a cooling and heating period. The savings are mainly due to higher indoor temperature set point during hot period and lower indoor temperature set point during cold period than the recommended value. Numerous works have been carried out to show how much energy can be saved during cooling and heating period by applying adaptive comfort temperature. The previous work, however, focused on a continuous cooling load as found in many office and residential buildings. Therefore, this paper aims to simulate the energy saving potential for an academic glazed building in tropical Malaysian climate by developing adaptive cooling technique. A building simulation program (TRNSYS) was used to model the building and simulate the cooling load characteristic using current and proposed technique. Two experimental measurements were conducted and the results were used to validate the model. Finally, cooling load characteristic of the academic building using current and proposed technique were compared and the results showed that annual energy saving potential as much as 305,150kWh can be achieved.

Evaluation of electrochromic windows impact in the energy performance of buildings in Mediterranean climates

Old buildings refurbishment is essential for the global improvement of building energy indicators. Within this context, the paper focuses on the energy savings that may occur when using electrochromic (EC) windows, an interesting emerging technology alternative to shading devices to control solar gain in buildings located in Mediterranean climates. The EC windows technology is briefly presented and the optical properties adjustments of the glasses are discussed according to the operated range. The EC window dynamic behavior and the different control strategies are modeled and implemented in the ESP-r building simulation program. The EC window impact in the energy needs for heating and cooling is studied, considering different ambient parameters (exterior dry bulb temperature, interior dry bulb temperature and incident radiation) and set points for the EC control. A comparison of several windows solutions (single, double-glazing and EC windows), the type of building, internal gains from occupancy, lighting and equipment and the orientation of windows are considered for discussion through the analysis of the energy needs for heating and cooling. It is concluded that for this climate the best positive results are obtained when the EC are used in the west façade. For the south façade the results show no significant advantages in using EC windows.

건물의 일사에너지 예측을 위한 경사면 일사량 측정과 예측모델과의 비교분석 연구

In all building`s energy simulation applications, solar radiation must be calculated on inclined surfaces. Various solar radiation models based on measured data of specific region were used in building simulation programs. Therefore, we should choose the appropriate solar radiation model for Seoul. The purpose of this study is to compare four solar radiation models on inclined surfaces that are widely used in building energy simulations. In this case, it can be said the appropriate model in Seoul is the Isotropic model.

Comparing vertical ground heat exchanger models

The main objective of this article is to establish a set of test cases for analytical verification and inter-model comparison of vertical ground heat exchanger (GHX) models used in building simulation programs. Several test cases are suggested. They range from steady-state heat rejection in a single borehole to varying hourly loads with relatively large yearly thermal imbalance in multiple borehole configurations. The usefulness of the proposed test cases is illustrated with different GHX models. This comparison exercise has shown that analytical one-dimensional (1D) models compare favourably well with three-dimensional (3D) models for relatively short-simulation periods, where axial effects are not significant. Cyclic heat rejection/collection tests proved to be useful to characterize the accuracy and the computational performance of different load aggregation algorithms. Finally, different spatial superposition methods have been compared for various bore field sizes and configurations and various loads.

Climatic influence on the design and operation of chiller systems serving office buildings in a subtropical climate

Climate change is a hot topic which would influence the design and operation of building systems. Many simulation studies focus mainly on the impact of climate change on the overall energy consumption of buildings. This study investigates climatic influences on chiller systems commonly used to provide cooling energy in commercial buildings but with considerable electricity consumption. Climate change scenarios in 2020, 2050 and 2080 were considered to generate forecast weather data based on a typical meteorological year weather file for subtropical Hong Kong. The building simulation program EnergyPlus was used to model an office building with air-cooled and water-cooled chiller systems. Hourly simulations were carried out to examine how different climate change scenarios influence the capacity of the systems and their electricity consumption. The findings indicate that a 3.9–4.2% extension in capacity should be considered for a system to meet the increasing cooling demand over its 15-year functional life. The electricity consumption of the system could increase by 6.8–8.0% over its functional life when operating for the warmer future climate. The ways to enhance the sustainability of chiller systems are addressed.

Numerical comparison between energy and comfort performances of radiant heating and cooling systems versus air systems

A comparison between energy performance, simulated by means of the EnergyPlus building simulation program, of two air systems (all air and fan coil) and radiant heating and cooling floors/ceilings is developed in this work for various European climates (Milan, Frankfurt, London, Madrid, Athens, Helsinki, and Moscow) and carried out on a reference building selected from among U.S. Department of Energy commercial building new construction benchmarks. The comparison is focused on the analysis of energy sources and CO2 emissions at equivalent thermal comfort quality levels in the various cases. The adoption of a radiant system, and of an appropriate primary energy system, always results in a reduction of energy sources exploited, of costs for energy wares purchased, and of carbon dioxide emissions. The greatest reductions can be achieved in climates where the energy demand for cooling is greater than the energy demand for heating. The article also focuses on the discussion of the procedure to be adopted when a comparison between air systems and radiant systems is implemented.

Electrochromic dynamic windows for office buildings

Abstract The next generation of advanced fenestration products includes dynamic electrochromic (EC) windows which can modulate the solar energy entering a building by application of an applied voltage. The windows can be switched from 62% visible transmittance (Tvis), 0.47 solar heat gain coefficient (SHGC) to a fully tinted state with ⩽2% Tvis, 0.09 SHGC. EC windows save energy in buildings – the total energy use for an eight story ASHRAE 90.1 2007 commercial office building with EC windows was modeled using the eQuest building simulation program and compared with the energy use of the same building with a variety of static glazings. The simulations were carried out in three US climate zones, encompassing a broad range of environmental exposure conditions from hot and dry (Arizona) to very cold (Minnesota). For all climate zones, building energy savings with EC glass were ⩾45% when compared to single pane static glazings common in existing building stock. When EC glass was compared to ASHRAE 90.1 2007 code compliant glazings, energy savings greater than 20% were calculated for the same building configuration. Optimum EC window control and performance strategies were derived from the modeling results. The EC glass and dimmable electric lights were synergistically controlled to maximize the use of natural daylighting and minimize electricity for lighting. Since EC glass can tint to ⩽2%, shades and/or blinds are not required for glare reduction, and building occupants always have a comfortable working environment and an unobstructed view and connection to the outdoors. All static glazing systems were assumed to have manual shading devices that are pulled by building occupants when glare becomes uncomfortable. For integrated building control systems, the peak load is significantly reduced when dynamic glazings are part of the building envelope. Consequently, chiller costs are lower, and the upfront capital costs for new building construction are reduced. Another key benefit of EC glass, elucidated by the simulations is reduction of CO2 emissions. EC glass reduces peak load carbon emissions by as much as 35% in new construction and 50% in renovation projects.

Calibration and validation of a model for simulating thermal and electric performance of an internal combustion engine-based micro-cogeneration device

The growing worldwide demand for more efficient and less polluting forms of energy production has led to a renewed interest in the use of micro-cogeneration technologies in the residential. Among the others technologies, internal combustion engine-based micro-cogeneration devices are a market-ready technology gaining an increasing appeal thanks to their high efficiency, fuel flexibility, low emissions, low noise and vibration.In order to explore and assess the feasibility of using internal combustion engine-based cogeneration systems in the residential sector, an accurate and practical simulation model that can be used to conduct sensitivity and what-if analyses is needed. A residential cogeneration device model has been developed within IEA/ECBCS Annex 42 and implemented into a number of building simulation programs. This model is potentially able to accurately predict the thermal and electrical outputs of the residential cogeneration devices, but it relies almost entirely on empirical data because the model specification uses experimental measurements contained within a performance map to represent the device specific performance characteristics coupled with thermally massive elements to characterize the device's dynamic thermal performance.At the Built Environment Control Laboratory of Seconda Università degli studi di Napoli, an AISIN SEIKI micro-cogeneration device based on natural gas fuelled reciprocating internal combustion engine is available. This unit has been intensively tested in order to calibrate and validate the Annex 42 model. This paper shows in detail the series of experiments conducted for the calibration activity and examines the validity of this model by contrasting simulation predictions to measurements derived by operating the system in electric load following control strategy. The statistical comparison was made both for the whole database and the segregated data by system mode operation.The good agreement found in the predictions of net electric power production, useful thermal output and primary power consumption allowed to conclude that the Annex 42 model can be used to carry out a detailed performance assessment in order to examine the applicability of the AISIN SEIKI unit for supplying building electrical and thermal energy requirements according to different load profiles during annual or multi-year operation.

Impact of material surface properties on building performance across a variety of climates

Reflective coatings have been promoted for improved energy performance of buildings and are considered in some building regulations such as the California Title 24 standard. This paper provides an analysis of the energy impact of different internal and external surface coatings on heating and cooling energy performance across a variety of climates, constructions and building types. The analysis is undertaken with the ESP-r integrated whole building simulation program. The results are compared with other studies and conclusions are drawn. The effect of these properties is shown to affect the energy performance of buildings and to vary with the context.

The design reference year – a new approach to testing a building in more extreme weather using UKCP09 projections

Current practice in building design is to assess a building’s performance using average or typical weather, a test reference year (TRY), and then to see how it performs when ‘stressed’, using a design summer year (DSY). The DSY is an actual year of hourly data which has the third warmest summer in 20 years’ summers. One of the problems with the DSY method is that it does not explicitly take into account solar radiation, or humidity, nor when more extreme weather occurs – it is selected solely on the mean six monthly temperature from April to September. A DSY may actually be cloudier than the average weather of a TRY. This article proposes an alternative approach using a new type of design reference year (DRY) consisting of a year formed from individual more extreme weather months. The DRY is used in simulating the performance of a building and to identify a single critical month for over-heating, or maximum cooling load. This article compares the characteristics of the DSY and proposed DRY using future projected weather data from UKCIP. Practical applications: Building designers are increasingly required by their clients to demonstrate how a proposed building will perform under a future rather than historical climate. This article describes a method of processing the latest future climate projections (UK Climate Impacts Programme’s (UKCIP’s) CP09 data released in June 2009) and generating a design reference year (DRY) for use in building simulation programmes. The DRY is proposed as a replacement for the design summer year (DSY), which has a number of limitations.

Simulating urban heat island effects with climate change on a Manchester house

This article presents a methodology for determining the internal temperatures of a post-1919 mid-terrace house for the present-day and a future (2050) climate. The Meteorological Office, Hadley Centre regional climate model has been run with urban parameterisation and an improved land-surface scheme with urban heat island forcing and a weather generator to quantify the effect of the urban heat island. Manchester city dry-bulb air temperatures are shown to be of the order of 4 K higher than those for the present-day under a UKCP09 medium emissions scenario. Extreme summer temperature data (99% percentile) are used to produce a cooling design day for use in a building simulation program.1 Loft and wall insulation decreases internal air temperatures by up to 17% and low e glazing with louvres by up to 8%. Internal temperatures for a 2050 climate will exceed existing Chartered Institution of Building Services Engineers thresholds. Practical application: Climate change is an important subject for both the building industry and local authorities. Climate change scenarios produced by the Hadley Centre General Circulation Models (GCM) have been downscaled to the local level for use in a building simulation model.1 This article demonstrates a technique that enables data from a GCM to be used within a building simulation program1 for an urban environment. It also examines the implications of the combined effect of the urban heat island and climate change on the adaptation options available to designers and planners for existing and future buildings.

Dynamic coupling of the transient system simulation and fire dynamics simulation programs

Multi-zone building heat load prediction models are a useful tool for designing heating, ventilation and air conditioning (HVAC) systems and for assessing annual HVAC energy consumption. However, zone models are not able to account for detailed local flow-field effects. When these local flow-field effects are important, it is desirable to use computational fluid dynamics (CFD). Unfortunately, computation at the fine temporal and spatial scales used in CFD simulations is extremely time consuming, both in terms of the user input and the computational solving process, and so is often unsuitable for transient whole-of-building thermal simulations. The ideal tool would combine the benefits of both of these modelling techniques to simulate macro-scale outcomes which are influenced by complex building design features. In this study, an easy to implement and relatively efficient modelling technique is proposed which combines (i) the multi-zone and HVAC system simulation software TRNSYS with (ii) the CFD building simulation program FDS. Implementation of this technique requires the creation of a dynamic coupling procedure between the CFD and the multi-zone simulation components. Three test cases are used to check the validity of the coupling procedure. An example simulation is also provided to demonstrate the usefulness of the new technique for modelling the performance of a desiccant cooling HVAC system, with feedback control, in a shop with an open entrance. The coupling component source code and TRNSYS library files are available for download upon request.

Implementation and validation of simplified heat pump model in IDA-ICE energy simulation environment

Heating and cooling of buildings are responsible for a large percentage of world energy consumption. Today, ground source heat pumps offer one of the most energy efficient technologies to provide heating and cooling by using the renewable heat source of the building's surrounding ground volume. Primarily in Northern Europe these systems are becoming a common heating/cooling technology. Some currently available building simulation programs like TRNSYS or EnergyPlus have the ability to model them. In this paper a parameter estimation study of a water-to-water heat pump model, implemented in IDA-ICE simulation environment, is presented and validated using experimental data. The model is based on performance maps: user-supplied data files containing catalogue data for the delivered energy and power absorbed are based on the entering load and source temperatures. The simulation results show that, if the input parameters (e.g. heat pump typology and control operation) are known, the simulated heat-pump model corresponds closely with the experimental operation. The maximum absolute mean deviation in the predicted values is equal to 5.09, 0.94, and 5.06%, respectively, for COP, condenser water temperature, and power delivered by the heat pump in heating operation.

Developing future hourly weather files for studying the impact of climate change on building energy performance in Hong Kong

The concern on climate change leads to growing demand for minimization of energy use. As building is one of the largest energy consuming sectors, it is essential to study the impact of climate change on building energy performance. In this regard, building energy simulation software is a useful tool. A set of appropriate typical weather files is one of the key factors towards successful building energy simulation. This paper reports the work of developing a set of weather data files for subtropical Hong Kong, taking into the effect of future climate change. Projected monthly mean climate changes from a selected General Circulation Model for three future periods under two emission scenarios were integrated into an existing typical meteorological year weather file by a morphing method. Through this work, six sets of future weather files for subtropical Hong Kong were produced. A typical office building and a residential flat were modeled using building simulation program EnergyPlus. Hourly building energy simulations were carried out. The simulated results indicate that there will be substantial increase in A/C energy consumption under the impact of future climate change, ranging from 2.6% to 14.3% and from 3.7% to 24% for office building and residential flat, respectively.

Constructing a future weather file for use in building simulation using UKCP09 projections

In the future with climate change, building designers may need to demonstrate to clients that their buildings will continue to provide a comfortable environment under future weather conditions. Building simulation modelling can be used to this end provided that suitable weather files can be constructed. This article describes the use of the latest climate projections from UKCIP (UKCP09 data) and a method of constructing an hourly weather file for the following parameters: dry-bulb temperature, relative humidity, cloud cover, solar irradiation (direct and diffuse), wind speed and wind direction. For a given future scenario, the approach used first selects appropriate months from 3000 years of UKCP09 data to construct a Test Reference Year (TRY). Unfortunately, the UKCP09 hourly data has no wind or cloud data, and the solar irradiance is uncorrected at low sun angles. This article describes algorithms for calculating wind speed and cloud cover from the UKCP09 data. From this data, a TRY can be constructed and formatted to be suitable for use with commonly used simulation packages. Practical applications: Building professionals increasingly seek reassurance on how a proposed building will perform under a future rather than historical climate. This article describes a method of processing the latest future climate projections (UKCP09 data released in June 2009) and generating a Test Reference Year (TRY) with the full complement of weather parameters suitable for use by commonly used building simulation programmes.

Solar control: A general method for modelling of solar gains through complex facades in building simulation programs

This paper describes a new general method for building simulation programs which is intended to be used for the modelling of complex facades. The term ‘complex facades’ is used to designate facades with venetian blinds, prismatic layers, light re-directing surfaces, etc. In all these cases, the facade properties have a complex angular dependence. In addition to this, such facades very often have non-airtight layers and/or imperfect components (e.g. non-ideal sharp edges, non-flat surfaces, …). Therefore building planners often had to neglect some of the innovative features and to use ‘work-arounds’ in order to approximate the properties of complex facades in building simulation programs. A well-defined methodology for these cases was missing. This paper presents such a general methodology. The main advantage of the new method is that it only uses measureable quantities of the transparent or translucent part of the facade as a whole. This is the main difference in comparison with state of the art modelling based on the characteristics of the individual subcomponents, which is often impossible due to non-existing heat- and/or light-transfer models within the complex facade. It is shown that the new method can significantly increase the accuracy of heating/cooling loads and room temperatures.

Assessing the total energy impact of manual and optimized blind control in combination with different lighting schedules in a building simulation environment

In this work, we investigated the interplay and the influence of lighting and blind control models on the heating, cooling, and lighting energy loads of an office room. By including different stochastic models for occupancy and appliances, we built a complete simulation environment based on the building simulation program IDA ICE. For control models, we implemented different strategies, including a simple on/off scheme, a realistic model of occupants, and an optimized control. In literature, the results are often compared with simple on/off schemes, which are not hard to beat in terms of performance. With an optimal control, the real saving potential is assessed, which can be used as benchmark case for comparison with other control models. Results based on annual simulations show that active occupants can reduce energy consumption by up to 50% from a worst-case scenario, whereas advanced controllers can further reduce the consumption by another 60%.

Code compliance of fully glazed tall office buildings in hot climate

In this research, the effect of glazing type and other energy conservation measures on the peak power demand of air-conditioning (AC) systems is investigated for tall and fully glazed government and private office buildings. The EnergyPlus building simulation program is used in the analysis assuming climate conditions similar to that experienced in hot countries of the Arabian Gulf, such as Kuwait. The main objective of the investigation is to meet the limits stipulated in the mandatory Kuwaiti code of practice for energy conservation, with respect to peak AC demand, for both air-cooled and water-cooled AC systems. It is found that for government office buildings with air-cooled AC system, the code limit of 70 W/m 2 for the AC peak power is met when tint low-e glazing is used with either heat recovery units or with AC systems with higher coefficient of performance (COP); whereas for private office buildings, the limit can be met when using a number of conservation measures. Overall, the water-cooled AC system showed better performance even though the code limit is 50 W/m 2 which is mainly due to the higher COP values achievable with such AC systems.

Transient heat conduction in multi-layer walls: An efficient strategy for Laplace's method

Enhancing load calculation tools into building simulation programs requires an in-depth revision and fine tuning of the load calculation assumptions prior to the addition of the HVAC system modelling routines. It is of special interest the analysis of transient heat conduction through multi-layer walls where, in order to improve the coupling between the passive elements of the building and the HVAC systems, an improvement of the time resolution in the calculation becomes critical. Several methods have been historically used, although recently Laplace's method has been displaced by the State Space method. This paper proposes a new strategy for fine time resolution on the calculation of the response factors through Laplace's method considering a comparison with the performance of the State Space method when used to calculate conduction transfer functions. Our analysis shows that in order to achieve similar accuracy with both approaches, the State Space method requires significant additional computational time.