Energy Efficiency with Building Automation Systems I
Course Transcript
Slide 1
Welcome to Energy Efficiency with Building Automation Systems Part 1. This is the first course in a two part
series. Once you have completed this course please move on to take Energy Efficiency with Building
Automation Systems Part 2.
Slide 2
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Slide 3
At the completion of this course you will be able to
• Define what a building automation system is
• Review the main terminology and components of a Building Automation System and HVAC system
• List the most common HVAC strategies that may be controlled by a Building Automation System
Slide 4
A building automation system, also referred to as a BAS can be set up to automate a building to make work
more efficient for facility managers and more effective for occupants. An Energy Management System, or
EMS, is a subset of that. It performs like a Building Automation System but it also focuses to automate the
building to run as energy efficiently as possible. The energy conservation measures implemented bring
utility bill savings without compromising the comfort or safety of building occupants. It will still optimize
Indoor Air Quality, Temperature Control, and Lighting.
The amount of global Energy used in 2004 was approximately 447 Quadrillion BTU. That equates to almost
80 million barrels of oil per day. Global energy consumption is expected to double in the next 25 years. The
World Business Council for Sustainable Development says that “buildings today account for 40 percent of
energy consumption in developed countries.” Their goal by the year 2050 is for new buildings to be built that
will consume zero net energy and produce zero net carbon dioxide emissions, and an overall reduction of
buildings’ carbon footprint.
They also report that global energy consumption for buildings is expected to grow 45% from 2002 to 2025,
and global carbon emissions is expected to increase 92%.
The WBCSD shows by modeling that energy use in buildings can be cut 60% by 2050. To make that
happen, they are suggesting the following.
First, to Strengthen building codes and energy labeling for increased transparency. Second, to encourage
integrated design approaches and innovations. And third, to develop and use advanced technology to
enable energy-saving behavior.
It’s a common misconception that energy conservation measures won’t generate much savings on a
building that already has a building automation system. However, just because a building has a building
automation system does not guarantee that it is running efficiently.
In this course we will focus on what a building automation system (BAS) is as well as some of the commonly
used terminology. We will also look at some of the HVAC strategies used in building automation systems. In
part 2 of this series, we will focus on some of the energy conservation measures (ECM) used within a BAS.
Slide 5
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A building automation system is a type of control system. The goal of a BAS incorporating energy
management is to maintain comfort and safety, while minimizing energy consumption and facility
management effort.
Control systems are composed of three basic types of components:
• Something to measure data
• Something to take those measurements and compare them with defined parameters, and
• Something causing an action to bring about a change
In a building some examples of parameters that might be measured are temperature, humidity, pressure, or
flow rate. Once these measurements are taken and processed, an adjustment may need to be made.
Examples of devices which could be used to make those adjustments are fans and pumps within the HVAC
system.
Building automation systems can be scalable to control specific floors or zones within a building. They can
manage single buildings or entire campuses sharing the same equipment, such as a chiller or boiler.
Slide 6
Now that we understand what a BAS system is, let’s talk about its functions.
Building Automation Systems can be applied in various ways.
The most well-known function of a BAS is to adjust lighting and HVAC equipment for occupant comfort. An
Energy Management System or EMS is a more focused version of a BAS in that it looks at occupant comfort
and energy efficiency. We’ll see a variety of techniques in part 2 of this series, including demand limiting,
resets and schedules.
Another function is monitoring and surveillance. A Building Automation System can be used to support
security functions such as access control. This can be linked to other functions, for example, using
occupancy sensors to detect when someone is in a room and adjusting HVAC accordingly. The system
knows who is where and can use that information to automate the building based upon where people are.
Maintenance can also be supported by a control system. Maintenance schedules can be supported by
reminder alarms from the system, or highlighting declining equipment performance to trigger maintenance
actions.
Finally, generating records is a great proactive application that can be implemented with a control system. If
there is a zone that is suspected to have problems or subject to occupant complaints, a record could be
started to record readings on several sensors within that zone. This is a great way to begin trouble-shooting
efforts to find a solution.
Slide 7
Let’s discuss the parts of the BAS.
A BAS measures data such as temperature, feeds that to a controller that compares the measurement to a
standard, such as a targeted temperature set-point, and when needed makes any necessary changes with a
controlled device.
Because data flows into the component that processes it, the devices used for measuring data are called
inputs, or sensors. This is the first step of control. You need to measure what you wish to control. When you
make changes to a system, there has to be some kind of feedback loop that tells you how successful the
changes are. Sensors repeatedly measure variables such as temperature, and feed that information to a
component that processes it.
The components that take in that data and process it, called controllers, contain the logic of the control
system. Controllers collect needed data that has been measured by the sensors, and then they compare
those measurements with a set of standards or instructions.
Slide 8
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Typically a building’s automation system would have a central computer for overall monitoring and control of
settings which would be supported by other controllers throughout the building or campus. Let’s say a
conference room in a building got up to 79°F/26°C. The controller would sense that reading and, based on
a previously programmed set-point, it would respond and bring the temperature back to that set-point.
The components that the controller activates to cause some change in the system are called outputs, or
controlled devices. Controlled Devices bring about some kind of change in the environmental system like
speeding up a fan, or an actuator opening a damper to let more air through.
To learn more about these components and how they function, see our course titled Introduction to Building
Controls.
Slide 9
In order to have a clear understanding of building automation systems, let’s review some of the terminology
used to explain these systems.
Slide 10
A set point is simply the target value that the control system will try to reach, for example, the desired
interior temperature.
Slide 11
The Outside air or makeup air is air drawn from outside the building to ensure that sufficient fresh air is
provided through the ventilation system. This is done to guarantee that CO2 and contaminant levels are
acceptable.
Supply air is conditioned air that is being provided to the space within the building.
Return air is air that is drawn from the space within the building back into the HVAC system.
The Exhaust air is the air that is ventilated from the building to the outside.
Let’s move on to discuss HVAC Equipment.
Slide 12
To explain how a BAS makes a building more efficient, let’s start with an overview of the equipment in the
building related to HVAC.
If you would like more information about how the HVAC equipment functions and how it can be optimized
please take our course entitled HVAC equipment and optimization.
Slide 13
The Air Handling Unit, or AHU, conditions the air that will go to the building occupants. Conditioning air can
have a variety of meanings, but the three things that are almost always done in the conditioning process are
cooling, heating, and filtering.
An AHU is usually a metal box that contains a blower fan to move the air, filters to clean it, heating and
cooling elements, and potentially a humidifier to add moisture content if required. The AHU often connects
to ductwork that moves the air to locations inside the building and returns it to the AHU, but in some spaces
the AHU may vent directly into the space. It may include a mixing chamber to combine air from the building
with fresh outside air, devices for heat recovery to minimize heat loss to the outside, and control
components to connect to the building automation system.
Chilled water pipes enter the air handler and wind through a set of fins which are sheets of metal. When the
fan blows air across those fins, the air rejects its heat energy to the cooler fins. When air is blown across
heated coils, the air is heated. Filtering reduces contaminants that are either coming from occupants or the
outside air. A building may have several air handling units.
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Slide 14
In larger facilities or campuses, a chiller may be used to provide cooling. Working through processes of heat
rejection, the chiller system functionally removes heat from the building and rejects it to the atmosphere.
Heat rejection is accomplished through three main loops: the chilled water loop, the refrigerant loop, and the
condenser water loop.
Air is circulated through the building by the HVAC system. During periods when cooling is required, warm
air will be returned from rooms through return vents to the air handler. That warm energy in the returned air
is then transferred from the air into the chilled water loop at the heat exchanging cooling coils.
As energy always moves from a hotter mass to a cooler mass, the heat energy in the air moves to the
cooling coils.
Slide 15
When the chilled water loop reenters the chiller (or the evaporator tank), the chilled water rejects its heat to
the cooler refrigerant loop.
This again is done through a heat exchanging process. Usually in a chiller, chilled water is pushed through
tubes with refrigerant in the shell around it to protect the two liquids from mixing.
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Since the refrigerant has quite a low boiling point, the refrigerant turns into a vapor. The near vapor portion
of the refrigerant, having never left the chiller, is sucked through a compressor and under pressure goes
back to a very hot liquid into the condenser tank which rejects its heat to the cooler condenser water loop.
That condenser water leaves the condenser tank and heads to the cooling tower. Finally, it rejects its heat to
the cooler atmosphere.
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Slide 16
The Cooling Tower works with the chiller as a method of heat rejection for the condenser water leaving the
condenser tank of the chiller. In most cases, water is sprayed out of nozzles at the top of the cooling tower
and trickles down over fins. As air falls down, more air is brought in at the bottom of the Cooling Tower and
blown out the top. This introduces cooler air which cools the condenser water trickling down over the fins
and also causes some of that water to evaporate, taking further energy from the water. The cooler
condenser water returns to the condenser tank of the chiller to remove more heat energy from the
refrigerant.
Slide 17
As we will see, some HVAC strategies depend on supplying varying amount of air to the space. In this case
a flow controller or flow station will be fitted in the ductwork. This will include a sensor in the ductwork to
detect the velocity and volume (cubic-feet-per-minute or cubic-meters-per-second) of air, and a connection
to the temperature sensor in the room. Based on the inputs from the sensors, the flow controller adjusts the
©2021 Schneider Electric. All rights reserved. All trademarks provided are the property of their respective owners.
position of a damper to allow the proper volumetric flow rate (CFM – cubic feet per minute / CMS – cubic
meters per second)
A damper is typically a swiveling plate whose angle can be adjusted to partially block the duct and thus
allow more or less air through.
Slide 18
In large campus/building cases, it is better to transfer heat energy through steam. In these cases, a boiler is
used to heat water up into steam, and that steam is then put into a pressurized system. When the steam
cools at the end use devices, it turns back into water as energy is pulled out of the steam. That condensed
water, called condensate, is still quite hot, so it is transferred back to the boiler to turn back into steam.
Now that we have an understanding of the terminology, let’s talk about some of the HVAC strategies used in
building automation systems.
Slide 19
To understand how a BAS can function to improve efficiency, we need to understand some of the different
strategies that may be employed. Let’s move on to talk about that now.
Slide 20
Some older HVAC systems use parallel heating and cooling surfaces, called hot and cold decks. The
heating and cooling systems are run simultaneously and the air is supplied thorough separate ducts for hot
and cold air. The air provided in these dual duct systems is mixed in a plenum or mixing box to achieve the
desired temperature and then supplied to the room. Running both heating and cooling simultaneously is
inefficient and these systems are now banned by many building codes.
Slide 21
The constant volume/Variable temperature system keeps the same amount of air flowing all the time, but
changes the temperature according to the needs. If the space has to be cooled considerably, the system will
supply very cold air, until the temperature approaches the set-point. Then the system will continue supplying
air, but at a warmer temperature, so as not to over-cool the space.
Slide 22
Variable Air Volume provides air at a constant temperature, but provides more of it when cooling or heating
needs are present. For example in cooling mode, the air coming into the room will typically be at a
temperature of 55 F (13 C). The air gradually replaces the existing air, and achieves the required
temperature level. When the setpoint is achieved, the volume of supplied air is reduced.
Slide 23
There are some different HVAC strategies where a BAS can have an impact. Let’s define terminal reheat,
also known as variable air volume. Some HVAC systems work by cooling all the air supplied to the space in
the building to manage the humidity. The quantity of air supplied is varied in order to control temperature. If
a room is too warm, more cold air is supplied until the required temperature is reached. If some zones in the
space have requirements for warmer air, the cold air is heated by reheat coils in a plenum or by a duct in the
plenum just before it is supplied to the space. This is called terminal reheat. Clearly this is inefficient
because the air is being cooled and then reheated. We will look at some methods of minimizing inefficiency
in part 2 of this series.
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Slide 24
Let’s take a moment to review what we have covered throughout this course.
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Building Automation Systems automate a building for better
• Efficiency for facility managers and
• Effectiveness for occupants
An Energy Management System is a sub section of the BAS that focuses to automate the building
to run as energy efficiently as possible
The goal of an EMS is to maintain comfort and safety while minimizing energy consumption
There are three basic types of components in control systems
• Something to measure data
• Something to compare measurements to a standard
• Something to enact any necessary change based on those measurements
A BAS can be used for many purposes including lighting and HVAC adjustments
BAS’s usually have a central computer for overall monitoring and control of settings in a building or
campus; other controllers may be distributed throughout the building
We looked at some key terminology for understanding the operation of a BAS
• A set point which is the target value that a control system is trying to reach
• Outside or Make-up air which is fresh air being brought into a building from the outside
• Supply air which has been conditioned and is supplied into the space inside a building
• Return air which is the air that is drawn from the space in the building and returned to the
HVAC system and
• Exhaust air which is the air that is expelled from the building HVAC system back outside
We briefly looked at some of the key components used to maintain occupant comfort in an HVAC
system including air handling units, chillers, cooling towers, flow controllers, and boilers
There are a number of different HVAC strategies that can be used with a BAS: Some of these are
• Dual duct - also known as hot deck / cold deck
• Constant volume / variable temperature
• Variable air volume
• Variable air volume with terminal reheat
Slide 25
Thank you for participating in this course.
©2021 Schneider Electric. All rights reserved. All trademarks provided are the property of their respective owners.