Other Building Energy Analysis Software

As already described in section 2.2.1, the BLAST [65] and DOE-2 [51] packages have been superseded by EnergyPlus. These packages contained a subset of the features available in EnergyPlus and were both focussed on the simulation of the thermal properties of a building and HVAC systems rather than the overall energy usage of a building. Similarly to EnergyPlus, both of these packages accepted input and produced output in text file format with a number of third parties producing graphical user interfaces.

ESP-r [66-67] is a complete building energy analysis tool which has been under development for over thirty years at the University of Strathclyde. The capabilities of ESP-r very closely match those of EnergyPlus in that it is capable of modelling heat transfer between building zones and surfaces, HVAC systems, mass flow of air and water, sunlight and shading and electrical power flow. In addition to the 1D heat conduction model that EnergyPlus employs for surface heat transfer, ESP-r offers optional 2D and 3D conduction models for more accurate simulations. An optional computational fluid dynamics (CFD) numerical approach [68] can also be used within zones in contrast to the standard uniform air temperature model to gain a greater understanding of the temperature gradients across each zone. ESP-r uses similar solvers to EnergyPlus for the mass flow of air and water throughout a building whereby a node-based representation is used to generate a model of the system [69].

Electrical power flow within a model is solved using a frequency-domain power flow solver [70] to obtain the steady-state power for each time-step within the simulation. The concept of “hybrid components” is used to enable components which convert electricity to heat and vice versa to be represented. These components interact separately with both the thermal and electrical solvers within the package. Definition of models within ESP-r can be carried out using a basic graphical user interface and also through the import of building geometry from CAD packages. A number of third party components are used to visually present simulation results. Numerous studies have been carried out by the program’s development team in order to validate the results produced by the package [71]. These studies include analytical comparisons to ensure that the package produces the expected results according to the theory that it is based on, empirical studies to compare the performance of the simulations

to real-world data, and comparative studies to compare the performance of ESP-r to other packages. In these validation studies, the package has been found to be in agreement with other similar packages.

BSim [72] is a suite of programs which is developed by the Danish Building Research Institute for undertaking building energy simulations. Standard features of the package include the ability to simulate heat transfer between building zones, zone temperatures and humidity conditions. The effects of sunlight on a building’s climatic conditions and internal light levels, including the effects of shading by surrounding buildings can also be simulated. BSim does not provide any comprehensive coverage of electricity use within the modelled buildings.

Add-ons for the package allow for more advanced simulation of moisture conditions within buildings [73-74] and for simulation of the approximate yield of photovoltaic panels installed on the building [75]. One of the programs within the suite is a graphical user interface [76]

which allows for the definition of building models using a 3D view or 2D plan view. Another program within the suite offers the capability to import building models from CAD packages [77]. While the package has not been explicitly validated, the algorithms which make up the main part of its functionality have been validated in a previous version of the simulation engine.

The UK Building Research Establishment develops a simulation tool called SBEM (Simplified Building Energy Model) with graphical user interface in the form of a Microsoft Access database with macros called iSBEM [78-79]. Rather than being a complete building energy analysis tool, SBEM is designed to test the compliance of buildings with EU and UK building and energy efficiency regulations. This compliance is tested using a simplified set of calculations known as the National Calculation Method (NCM). Two versions of the calculation method are defined: one for Scotland [80] and another for England and Wales [81]. As the tool is primarily a compliance and energy efficiency, its outputs are whole-building energy metrics rather than detailed calculation of room and surface temperatures and electricity usage. The developers of the tool therefore indicate that it should not be used in design simulations and that other tools should be used for this purpose.

Energy-10 [82] is a proprietary software package which is aimed at assessing the effect of installing different energy efficiency measures during the design of small residential or commercial buildings. The focus of this package is on rapidly modelling buildings and running hourly simulations to assess the benefit (both environmental and economic) of installing various energy efficiency measures. It could therefore be described as a tool which assists in decision-making rather than a complete energy analysis tool. Little information about this package is available in the public domain due to its proprietary nature, however, available features are: daylight simulation, passive solar heating and cooling, natural ventilation, insulation, high performance windows, lighting and mechanical equipment.

The “Transient System Simulation Program” or TRNSYS [83-84] is a proprietary software package which is developed by the University of Wisconsin-Madison in partnership with a number of industrial partners. The package is a modular, general-purpose transient simulator. However, the majority of the built-in mathematical models reflect the fact that it is very much targeted at the modelling of energy systems. In contrast to the whole-building definition approach, TRNSYS provides a more flexible method of modelling where individual components which are represented by mathematical models that can be connected together to form a complete system. In simple terms, the output of one mathematical model in the system becomes the input to others. The TRNSYS solver performs a simultaneous solution of the algebraic and differential equations which make up the model on each time-step of the simulation and records the results [48]. Systems are designed using a graphical user interface by adding mathematical models (either user-defined or from the built-in library) and making connections between them with lines to indicate the flow of data. The OpenStudio plug-in for EnergyPlus [54] which provides integration with Google Sketchup is also supported by TRNSYS, allowing a geometrical description of a building to be automatically converted into a mathematical model block for use in the package.

Matlab [85] is a mature mathematical programming environment which has gained widespread acceptance in the engineering community. The Simulink [86] simulation environment is a model-based simulation system which accompanies Matlab and enables the creation of Matlab programs from a graphical drag and drop based modelling interface. From

a usability perspective, Matlab and Simulink provide a good environment for the rapid development of system models. The SimPowerSystems package which is available for Simulink provides a mature power system modelling capability and the Communications System Toolbox provides a comprehensive communications system modelling capability, from the high-level protocol level down to the physical link level. Where the package falls short in meeting the requirements for domestic smart grid simulation is its lack of building simulation capabilities.