ESP-r is an integrated simulation system that may be used to explore a range of building performance issues relating to embodied and operational energy , health and comfort, environmental impact, system operation and the deployment of novel technologies—at timescales ranging from seconds to years. .The system comprises a central Project Manager connected to support programs for simulation, results analysis, database management and visualisation. The aim is to simulate the real world as rigorously as possible using techniques that are consistent with modelling best practice. The system has mathematical models for heat & moisture transfer, air & light flow, electrical power flow, control systems and a range of conventional and renewable energy technologies.
Such a tool can be applied at any design stage although the translation of design intent to model definition is non-trivial given the potentially large number of input parameters. To assist users, the Project Manager supports model definition in relation to:
During model definition, the user is given access to in-built databases of constructional materials, plant components, profile prototypes, optical properties and climate sequences. Where possible, inputs are achieved through graphical interaction or by importing data from CAD tools.
A Web-based training course is available for the ESP-r system.
The ESP-r system has been the subject of sustained developments since 1974 with the objective of emulating building performance in a manner that:
The system-r allows a detailed appraisal of the energy and environmental performance of buildings: a topic which is assuming increasing importance as energy and environmental awareness grows.
By addressing all aspects of performance simultaneously, ESP-r allows the designer to explore the complex relationships between a building's form, fabric, plant and control. The modelling technique is based on a finite volume, conservation approach in which a model (specified in terms of geometry, constructions, operation, leakage distribution etc) is transformed into a set of conservation equations for simultaneous solution at each time step when subjected to climate variations, occupant interactions and control actions. ESP-r's theoretical basis has been extensively documented.
A central Project Manager (PM) co-ordinates
the model definition process and the transfer of data to and from the support
programs.
Significantly, the PM supports an incremental evolution of the model as additional
detail becomes available. The PM requires that a record be kept of the problem
composition and to this end is able to store and manipulate text and images
which document the problem and any special technical features. It is also possible
to associate an integrated performance summary with this record so that the
design and its performance can be assessed without having to commission further
simulations.
While the databases issued with the system are comprehensive, users may add entries as new product information becomes available.
Building geometry can be defined using a CAD tool or via in-built facilities. ESP-r is compatible with the dxf compatible systems. The PM also offers model management whereby past designs are stored as fully attributed 3D models.Constructional and operational attribution is achieved by selecting products and entities from the support databases and associating these with the surfaces and spaces comprising the model.The PM provides coloured, textured images via the RADIANCE system, automatically generating the required input model and driving this external applications. As required, component networks can be defined to represent HVAC systems, distributed fluid flow (for the building-side air or plant-side working fluids) and electrical power circuits. Control system definitions can be made depending on the appraisal objectives. Within ESP-r this involves the establishment of several closed or open loops, each one comprising a sensor (to measure some simulation parameter at each time-step), an actuator (to deliver the control signal) and a regulation law (to relate the sensed condition to the actuated state). Typically, these loops are used to:Control loops can also be used to change portions of a problem with time (e.g. substitute alternative constructions) or impose replacement parameters (e.g. heat transfer coefficients).
For specialist applications, the resolution of parts of a model can be selectively increased. For example, ESP-r's default one-dimensional gridding scheme representing wall conduction can be enhanced to a two- or three-dimensional scheme to better represent a complex geometrical feature or thermal bridge. Alternatively, a one-, two- or three-dimensional grid can be imposed on a selected space to enable a thermally coupled computational fluid dynamics simulation. For problems involving daylight utilisation, the Simulator can invoke the RADIANCE system to quantify the internal illuminance distribution for input (via a sensor) to an artificial lighting control loop.
Special behaviour can be associated with a material to model, for example,
The defined model—from a single space with simple control and prescribed ventilation, to an entire building with systems, distributed control and enhanced resolution—can be passed to the Simulator where, in discretised form, the underlying conservation equations are numerically integrated at successive time intervals over some period of time. Simulations, after some minutes or hours, result in a time-series of state information (temperature, pressure etc) for each discrete region.
ESP's results analysis modules are used to view the simulation results and undertake a variety of performance appraisals: changes to the model parameters can then follow depending on these appraisals. The range of analyses are essentially unrestricted, allowing the different performance indicators to be inter-related and these indicators to to be translated to proposed design changes.
It is often necessary to estimate the overheating risk of an office block with natural ventilation. Combined thermal and air flow simulations may be undertaken to determine the frequency distribution of internal summertime dry resultant temperatures for assumed occupancy and internal gains.
Galleries within museums have strict requirements regarding the control of temperature and humidity and a need to operate within strict capital and running cost constraints. Combined simulation of the building and plant systems can be used to compare various plant configurations and to determine optimum component sizes.
A large number of glazing and shading devices are available. ESP-r can be used to assess the relative merits of these in terms of thermal, lighting and acoustic comfort, and energy consumption.
To facilitate passive design, the benefits of techniques such as thermal mass, night purging and displacement ventilation can be quantified.
Many prestige office blocks now include atria and sunspaces. ESP-r can be used to assess solar and daylight utilisation as well as the inherent buffering effects.
In many buildings, heat recovery appears an attractive option. ESP-r can be used to quantify the corresponding energy benefits of both heat recovery and partial recirculation of air.
Many new buildings are being constructed which attempt to integrate new technologies, either as prestigious developments or as demonstration buildings. ESP-r is equipped to model the impact of advanced concepts such as daylight responsive light, heat recovery, transparent insulation, breathable construction, photovoltaic facades and ground source heat pumps.
In short, tthe integrated simulation approach it extremely powerful. That said, it does have limitations. To address these, ESP-r has been subjected to many validation trials to test the robustness and accuracy of the underlying mathematical models. Other important considerations are user error and input data uncertainty.