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For the
sustainable operation of a building, it is important to understand the interplay
between the essential parameters. These parameters can be grouped into four
categories.
a) Aspects of use
The comfort conditions in the rooms are an essential requirement for the
overall planning and operation concept. This includes the thermal conditions
(e.g. set-point temperature: 20°C), adequate illuminance (daylight and
artificial light) and the possibility of adjusting the parameters.
b) Energy-efficient operation of buildings
The focus here is on the efficient use of energy (electricity, heating,
cooling).
This efficiency can be achieved with suitable functions of room and building
automation.
c) Building envelope
The envelope is the interface with the environment (e.g. facade systems or
building physics).
d) Building systems
This includes all technical systems which are used for heating, cooling,
ventilation and the power supply of a building.
In the
context of the EPBD (Directive 2010/31/EU of The European Parliament and of the
Council of 19 May 2010 on the energy performance of buildings), the standard EN 15232
“Energy performance of buildings - impact of Building Automation, Controls and
Building” was developed.
This standard
divides the functions of room and building automation into four BACS (Building Automation and Control Systems) efficiency
classes:
·
Class D
corresponds to BACS that are not energy-efficient. Buildings with such systems must
be retrofitted. New buildings may no longer be built with such systems.
·
Class C
corresponds to standard BACS.
·
Class B
corresponds to advanced BACS and some specific TBM functions.
·
Class A
corresponds to highly energy-efficient BACS and TBM.
The standard
provides two basic methods: the detailed and the simplified method (BACS factor
method). The simplified BACS factor method allows the use of factors to
calculate the final energy demand, depending on the BACS efficiency class.
This
approach allows easy explanations, e.g. for owners, of how much the energy
demand can be reduced for a given type of building through the functions of
room and building automation.
To analyze these
standardized methods under real-life conditions, Biberach University of Applied
Sciences has performed theoretical research (simulation studies) as well as experimental
analyses in seminar rooms in order to demonstrate the possible energy savings.
The goal of
the measurement campaign is to answer the key question of whether it is
possible to determine a potential for savings, in rooms in which different BACS
efficiency classes (according to the standard EN 15232) have been realized,
during the building’s actual operation, and if so, how high the potential
savings are.
For that
purpose, the University of Applied Sciences Biberach has organized a
measurement campaign involving three seminar rooms (G0.02, G0.03, G1.03, Figure 1) in the “Technikum G” building with comparable
boundary conditions over a longer period of time. These three rooms have
different functions in terms of room and building automation according to the
norm EN 15232.
For the
results, only the BACS efficiency classes C, B and A are compared. Class D
no longer complies with current technical standards.
The seminar
room G0.02 was chosen as the reference room. The functions in this room are based
on the BACS efficiency class C. In the other seminar rooms, different functions
of room and building automation were realized according to BACS efficiency
classes B and A, making it possible to determine potential energy savings
through technical measurements.
Table 1 lists the functions which were implemented. BACS efficiency
class A has the most extensive functional configuration. Class C is the
reference value for the energy savings.
Table 1.Combined functions of the
measurement campaign for the three test rooms according to the standard EN 15232.
G0.02 BACS
efficiency class C | G0.03 BACS
efficiency class A | G1.03 BACS
efficiency class B |
Manual lighting
on/off, without dimming | Manual lighting
on/off, without manual dimming automatic off (presence, daylight), constant
light control | Manual lighting
on/off, without manual dimming automatic off (presence, daylight) |
Temperature
control with a thermostatic valve | Individual
room control with three different set values: ·
14°C night setback/window opening monitoring ·
19°C stand-by ·
21°C normal mode | Individual
room control with three different set values: ·
10°C night setback/window opening monitoring ·
16°C stand-by ·
21°C normal mode |
Figure 1.Spatial arrangement of the seminar rooms for
the measurement campaign in the “Technikum G” building at Biberach University
of Applied Sciences.
Figure 2 shows the electrical energy consumption which was
measured in the three previously mentioned rooms with the different functional
configurations. The figures have been adjusted to account for the different
occupancies of the rooms.
While the lighting
in the reference room (G0.02, Class C) is controlled manually, the other
rooms have an automatic control which takes occupancy and available daylight into
account. In addition to this, there is a constant light control in Room G0.03 (Class A).
The clear improvement in the savings for Class A (G1.03) is due to the
optimization of the constant light control which took place between the
measurements “December 2009 – May 2010” and “October 2010 – March 2011”. This
optimization was based on experiences made during the first measurement period and
involved the correction of sensor placement, among other things.
This
illustrates the high importance of continuous improvement during operation.
Figure 2.Electric energy consumption with percentage savings of the BACS classes A, B, C
The data for heating energy consumption was analyzed analogously to the
method used for electrical energy consumption. While the control in the
reference room (G0.02) is realized with thermostatic valves, the room with the
BACS class C (G1.03) has an individual room control with a zone valve which is
blocked if a window is open. In addition to this, room G1.03 (BACS class A) has
an optimized set point if the room is unoccupied.
Figure 3 shows the comparison between the measurement data for
heating energy consumption. For the analysis, it was necessary to adjust for internal
loads (e.g. lighting, occupancy), geometrical dimensions and building physics
during the measurement periods.
The savings are based on the reference room G0.02. The data for March was
very well suited for the analysis, because the weather conditions were similar
in both years. You can see high energy
savings between the reference room and the rooms with constant light control.
While the savings in Room G0.03 were similar in both years, Room G1.03 shows
clear improvements between March 2010 and March 2011. The reason for this is
the realization in the first measurement period that the installed valve didn’t
fit to the valve gear. As a result, the control behavior was very bad.
This optimization process which was identified with the installed energy monitoring
made it possible to achieve a huge improvement in energy efficiency. This
example shows once more that continuous monitoring is very important. Continuous
monitoring is the basis for straightforward optimization during building
operation.
Figure 3.Comparison between the months March 2010 and
March 2011; reduced consumption of heating energy (adjusted)
A major advantage of integrated building automation systems lies in the ease
with which different types of data on the building and its systems can be
analyzed. These possibilities are more than the usual error messages and energy
analyses. For example, it is possible to check whether the automation strategy
suits the room (occupancy) profile.
The following section contains an example which demonstrates how differently
users can control the lighting of a room.
So-called carpet plots were used for the illustration. A carpet plot is a
type of chart which is very well suited for concentrated information analysis.
The abscissa of the chart is used for the day in a month or year and the
ordinate for every hour of a day. This makes it possible to display a mean
value (e.g. temperature) for data which is color-coded, allowing the analysis of
electrical power or the runtime of components such as pumps or fans over a
longer period of time at a glance.
A very clear example is shown in Figure 4 and Figure 5. The electrical power for the lighting and the
occupancy of Room G0.02 are color-coded. As noted in Table 1, the lighting in this room can only be switched on
and off manually (BACS class C). The occupancy sensor is only used to determine
occupancy, not control the lighting.
Figure 4 shows that the users switched the lighting on and off
in a fairly exemplary fashion in December 2010. During this period, users
switched off the lighting as soon they left the room. An occupancy sensor would
not result in any energy savings in this case.
In contrast to this, the situation with the same boundary conditions is
shown for October 2010. Figure 5 shows that the lighting was almost never switched off
from 14 October 2010 onwards, even if nobody was in the room. The light green
color shows an electrical power consumption of about 500 W. This amount may
represent a single light-band in the room which users forgot to switch off. In
this example, an occupancy sensor would save a lot of energy by deactivating the
light-band as soon as no one is in the room.
Figure 4.Carpet plot with an example of energy-efficient
user behavior (December 2010)
Figure 5.Carpet plot
with an example of inefficient user behavior (October 2010)
Along with
good building physics and building systems, building automation is the third
pillar in the energy-efficient operation of a building. Building automation
combined with energy monitoring is a particularly important tool for showing
potential for optimization in regard to users’ behavior.
As a basis
for this, it is necessary that building automation be considered during the
planning process. The standard EN 15232 with the defined BACS efficiency classes
provides a foundation for planning which has to be considered for the
realization of new and modernized buildings in order to arrive at
energy-efficient solutions.
Biberach
University of Applied Sciences has analyzed the energy consumption of three seminar
rooms with different BACS efficiency classes in order to determine the possible
energy savings in the norm.
The
analysis shows high potential energy savings through the use of room and
building automation. An additional insight is that a process (e.g. a building)
which has changing boundary conditions (e.g. the weather) or different
disturbances (e.g. user behavior) can only be operated with an automation
system which includes every building system.
The results
of the analysis show very well that user behavior has a huge influence on
measurements during the actual operation of a building. Even the prediction of
the possible energy savings and the analysis of the results are dependent on
this user influence.
Another
important insight for practical applications is the high influence that the
positioning of the sensor systems and the correct use of actuators have on the
potential energy savings.
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