FP7-2010-NMP-ENV-ENERGY-ICT-EeB
TIBUCON
Self Powered Wireless Sensor Network for HVAC System Energy
Improvement - Towards Integral Building Connectivity
Instrument:
Small or medium-scale focused research project - STREP
Thematic Priority:
EeB.ICT.2010.10-2 – ICT for energy-efficient buildings
and spaces of public use
BUILDING THERMAL SIMULATION AND CONTROL MODELS
AUTHORS: J. VAN DER VEKEN, J. VERHELST, P. DYMARSKI
Due date of deliverable:
Actual submission date:
31.12.2011
20.12.2011
Start date of project: 01.09.2010
Duration: 36 months
Organisation name of lead contractor for this deliverable: KHK
Dissemination level: Public
Revision
Final
TIBUCON
Building Thermal Simulation and Control Models
Abbreviations
BMS
Building Management System
D
Deliverable
EC
European Commission
ICT
Information and Communications Technologies
TIBUCON Self Powered Wireless Sensor Network for HVAC System Energy Improvement Towards Integral Building Connectivity
WP
Work Package
WT
Work Task
HVAC
Heating, Ventilation, Air Conditioning
TIBUCON
Building Thermal Simulation and Control Models
Introduction
The energy and comfort simulations of the demonstrator buildings play a central role in
the TIBUCON project. This report explains the construction of a software model to estimate the
transient thermal behaviour of a building and its HVAC installation, in response to the HVAC
control, its occupants behaviour and weather disturbances. This model will be used to simulate
the energy consumption and the thermal comfort in the demonstrator buildings where the
TIBUCON sensors are deployed, so that current and new control strategies can be
assessed and improved.
Steps of the modeling process
To model the thermal response of a building, a suitable modelling environment should
be selected. The software must be capable of modelling the hygro-thermal properties of the
demonstrator buildings, in combination with the type and sizing of HVAC installations, HVAC
control and the inhabitant behaviour. Only then it is possible to simulated in detail (emulate) their
heavily interacting and dynamic thermal responses. TRNSYS was selected as the most suitable
simulation environment for these cases.
Secondly, the amount of energy required to keep the zones at the requested temperatures
(and humidity) should be determined, under the assumption of a perfect heating system and
perfect heating control. This energy demand is called the Net Energy Demand (NED).It heavily
depends on the geometry of the buildings and its surrounding, the outdoor climate, the building
occupancy and the requested comfort level. Since weather conditions and user behaviour (indoor
environment) are not constant, a standardized climate for the region under investigation and typical
occupancy behaviour are included in the models.
The geometrical structure of one of the (residential) demonstrator buildings and its
corresponding model are represented in Figures 1 and 2 below. Figure 1 shows the residential
demonstrator building in the Sketch-up plug-in that makes it possible to model the geometry and
solar gains of the building in detail. Information about the building facade, climate, internal heat
gains (user behaviour) and HVAC-system and -control are added afterwards. Figure 2 shows
the simulation environment in which all building, inhabitant and HVAC-system models are coupled.
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TIBUCON
Building Thermal Simulation and Control Models
Figure 1.
Building blocks of the
residential demonstrator site
with neighbouring buildings in
SketchUp-TRNSYS 3 modul to
assess solar gains and
shadowing
Figure 2.
Screenshot of the integrated
(residential) building model in
the TRNSYS simulation studio
Unique aspects of this project
The TIBUCON project aims to produce sensor nodes that can be deployed into two main
environments: residential properties and office spaces. These nodes will provide information about
the thermal condition in the buildings. This information may be used to improve the control
strategy in order to save energy, and/or to increase the comfort level indoors.
To this end,
especially the HVAC system, the sensor nodes and HVAC control should be implemented in detail
in thermal simulation models. This was performed both for a residential environment and a
commercial office building.
Residential Environment:
Especially the residential demonstrator proved to be a modelling challenge, due to the size and
the unconformity of its heating system. In those buildings, a monotubular heating system (vertically
serially connected radiators) is present, frequently causing overheating of the lower apartments
and critically cold top apartments. This necessitates integral modelling and simulation of the
building to capture the interaction between different radiators in series. Suitable water
temperatures and water flows are crucial for a good comfort and low energy consumption, but this
is difficult to control with such a heating system.
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TIBUCON
Building Thermal Simulation and Control Models
Figure 3.
Vertically serial connected radiators in residential demonstrator building
Also the orientation of the apartments has a distinctive influence due to the variance of
solar gains (position of the sun during the day, and shadowing effects), causing underheating in
some apartments (mainly at the north) and overheating at others (mainly west orientated
apartments).
To cope with these interactions, two different modelling approaches were chosen :
First of all, a “Simplified whole building model” was generated, based on the
assumption of a simplified floor layout, so that all apartments of a building can be simulated
together in the simulation environment, as shown in Figure 4. This requires the assumption that
every apartment is a well-mixed thermal zone, but it allows to model a radiator on every floor and
study the influence of the serial connection.
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TIBUCON
Building Thermal Simulation and Control Models
Figure 4.
Picture and “Simplified whole building model” for one of the buildings on the residential
demonstrator site (existing residential apartment buildings)
Secondly, a “Detailed zone model” was created, based on four different zones per
apartment (living room, kitchen, bedroom and bathroom). The assumed apartment occupancy was
distributed over these different zones. In this detailed model, not all floors are incorporated
because that would lead to infeasible long simulation times with more than 150 separate zones per
building. Only three floors were retained (bottom, middle and top floor), as shown in Figure 5.
However, all radiators were modelled and a comparison with the simplified whole building model
showed good results. Now, both levels of detail can be used to verify the simulation models and
validate the control performance of the Tibucon solution.
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TIBUCON
Building Thermal Simulation and Control Models
Figure 5.
“Detailed zone models” of two other building at the residential demonstrator site (existing
residential apartment buildings).
Office Environment:
For the office environment demonstrator, a three story office building in Warsaw, Poland
was modelled together with its HVAC-system (fan coil units, radiators, AHU, chillers, boilers,
distribution system, etc), a standardized climate and typical occupancy and occupancy behaviour.
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TIBUCON
Building Thermal Simulation and Control Models
Figure 6.
Landscape zone model for one office floor (new office demonstrator) and screenshot of
the integrated (office) building model in the TRNSYS simulation studio
Simulations with the developed (hygro-)thermal models
In the following graphs (Figure 7,8,9), some screenshots of the simulations are shown. On
the vertical axis, the outside temperature [°C], room temperatures [°C] and set point temperatures
are shown. The horizontal axis shows the time (hours). Every graph depicts the temperature profile
of one typical week. There are large differences between the different orientations; Figure 7 shows
that temperatures at orientation CD (North) are much lower than at orientation AD (South), while
the former apartment consumes on average 15% more with the currently implemented control
function.
If on site measurements should show slightly different profiles, assumptions and
parameters (e.g radiator sizing and water flows in these zones or orientations) can be adjusted
accordingly.
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TIBUCON
Building Thermal Simulation and Control Models
Figure 7.
Screenshots of a (residential demonstrator) simulation, showing typical temperature
profiles of room temperatures and outside temperature in different apartments of one
building over a period of one week (during heating season).
Figure 8.
Office demonstrator simulation of typical temperature profile in office environment in the
heating season (left) and cooling season (right) in relation to the ambient temperature
heating and cooling set point, for a landscape office model.
Preliminary simulation results
From these simulations, both room temperature profiles, energy consumption profiles and
comfort estimations can be estimated for the different control schemes that will be assessed.
Preliminary simulation results of energy saving and/or comfort improving solutions are
visualised in Figure 9. This graph shows that up to 30% energy savings might be feasible for this
installation, with a small investment in additional sensors and actuators. Keep in mind however,
that these simulation results are not yet verified based on measurements. Later in the project, a
thorough validation of these models will be performed, based on measurement data gathered by
the TIBUCON sensor prototypes, which are being installed at the moment.
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TIBUCON
Figure 9.
Building Thermal Simulation and Control Models
Tradeoff of Comfort and energy consumption by changing HVAC control residential
demonstrator buildings (based on unvalidated simulations).
The blue rectangle depicts the current situation at the residential demonstrator building; a low
comfort is combined with a relatively high energy consumption. With a perfect heating system and
perfect heating control, no discomfort would be present and a very low energy consumption (the
blue circle at the bottom left) would be demanded. The blue and purple rectangle show a solution
that greatly improves the comfort, while the red triangle shows an energy saving solution compared
to the current situation. However, a combination of both measures (purple and orange dots) are the
most interesting and a variation of control parameters makes it still possible to choose whether the
focus is more on comfort or energy consumption (depicted by the curved line).
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