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Electrical engineering
Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics, and electromagnetism
Sunday, June 28, 2015
Advantages of Building Automation Systems
Advantages
of Building Automation Systems
Building automation systems have become powerful and effective
tools and are becoming more and more popular. They help resolve problems
quickly, reduce energy use, improve system performance, increase occupant
comfort and safety, and help manage maintenance costs. Savings produced by the
systems can pay for installation in as little as three to five years. The main
advantages of an automated system are discussed below.
Transparency
Which allow more controllability
on the building without need of any new installations, only some intelligent
devices are connected with the electromechanical equipments.
Multi-Functionality
The system can perform many
functions at the same time such as: switching, measuring, monitoring, and
recording ...etc. without additional cost.
Flexibility and Extendibility
Changes in programming of device can
be allowed and more devices can also be added on the existing system.Wall
switches, occupancy sensors, and load controllers have long useful life.
However the specific configuration of sensors and loads are likely evolve over
time.
Ideally configuration does not
need to occur when devices are physically installed. Configuration can occur at
any time and be readily changed as needs evolve. A room entry switch or sensor
can be reconfigured later to implement functions not envisioned when the sensor
was initially installed.
Economic Return
A building Automation system may
as well be called an energy management system that is because is controls
energy consuming equipment in a building to make is operate more efficiently
while maintaining a comfortable environment. As a result it could save a lot of
wasted energy which in return saves a lot of money.
Energy Efficient
The automation system represents
a parasitic energy load placing great value on maximizing functionality while
reducing energy consumption of the automation system itself.
Open Specifications
Open standards assure healthy
competition and compatibility among multiple players reducing risk of obsolete
or orphaned equipment.
Open stands encourage niche
players to market specialty devices increasing the likelihood special needs can
be met with off the shelf equipment.
ZigBee Advantage
New wireless command and control
technologies such as ZigBee IEEEE 802.15 are well suited to automation systems.
The radios are optimized for reliable short burst low latency traffic. ZigBee
radios have very low power consumption making them ideal for battery power
wireless sensors. Battery life in years is possible.
Radio based networks dramatically
reduce cost, especially in retrofit situations. Using a radio-based system
eliminates the functional distinction between fixed location and portable
devices. This minimizes development cost and maximizes reusability. The same
basic radio and firmware can be used in a fixed location light switch and hand
held A/V remote control.
Friday, June 26, 2015
Main Parts of Building Automation Systems
Main Parts of Building Automation Systems
Building automation is a
programmed, computerized, "intelligent" network of electronic devices
that monitor and control the different systems of a building such as HVAC,
security, fire, or lighting systems. The intent is to create an
intelligent building and reduce energy and maintenance costs.
Controller
The controller is normally one or
more programmable logic controllers (PLC), often with custom programming. PLCs
come in a wide range of sizes and capabilities to control devices that are
common in buildings. Usually the primary and secondary buses are chosen based
on what the PLCs provide.
Most PLCs provide general purpose
feedback loops, as well as digital circuits.
The operation of a building is
typically based on occupancy. Occupancy is defined by time of day schedules to
show when the building's systems are most likely in need of operation.
Override is possible through different means. Some buildings can sense occupancy in their internal spaces by an override
switch or sensor.
Lighting System
Lighting is another automated
service that can be turned on and off with a building automation system based
on time of day, or the occupancy sensors and timers. Operating times can
be set by individual tenants within the building. One typical example is
to turn the lights in a space on for a half hour since the last motion was
sensed. A photocell placed outside a building can sense darkness, and the time
of day, and modulate lights in outer offices and the parking lot.
Heating ,Ventilation and Air Conditioning
(HVAC) System
Climate control in buildings is an important automated service that can
save a lot of energy and thus money if the right technologies and design were
used. For example, the heating system can be turned down automatically
during the night or switched off completely when windows are open during the
day. The building also "considers" its occupants. The night-time
heating control temperature is not simply reduced on a timer basis like in
conventional systems, it is automatically adjusted to the actual utilization
levels and temperatures can automatically be adjusted to the actual weather
conditions. The indoor air quality can be monitored via suitable sensors, and
the climate can be adjusted as required.
Alarm and Security Systems
Many building automation systems have alarm capabilities. It can be programmed to notify someone if an alarm is detected.
Notification can be through a computer, pager, Mobile phone or audible alarm.
-
Common temperature alarms are
Space, Supply Air, Chilled Water Supply and Hot Water Supply.
-
Differential pressure switches can
be placed on the filter to determine if it is dirty.
-
Status alarms are common. If a
mechanical device like a pump is requested to start, and the status input
indicates it is off. This can indicate a failure.
-
Some valve actuators have end
switches to indicate if the valve has opened or not.
-
Carbon monoxide and carbon dioxide
sensors can be used to alarm if levels are too high.
At sites with several buildings,
momentary power failures can cause hundreds or thousands of alarms from
equipment that has shutdown. Some sites are programmed so that critical alarms
are automatically re-sent at varying intervals. For example, a repeating
critical alarm (of an uninterruptible power supply in 'by pass') might resound
at 10 minutes, 30 minutes, and every 2 to 4 hours there after until the alarms
are resolved.
Security systems can also be
interlocked to a building automation system. If occupancy sensors are present,
they can also be used as burglar alarms.
Fire and smoke alarm systems can
be hard-wired to override building automation. For example: if the smoke alarm
is activated, all the outside air dampers close to prevent air coming into the
building, and an exhaust system can isolate the alarmed area and activate an
exhaust fan to move smoke out of the area. Life safety applications are
normally hard-wired to a mechanical device to override building automation
control.
flashback of Building Automation
flashback of Building Automation
1. Centralization of Operations
Before the Second World War, the technical installations in commercial buildings were completely manually operated. Large control panels were built to centralize the flow of information from the technical installations and enabled remote operation.
These panels took up a lot of floor space and required extensive and expensive cabling as each data point (field input or output signal) was wired individually to the control panel. To enhance the transfer of information these control panels were sometimes equipped with mimic diagrams depicting the technical installations. The mimic diagrams contained indicators to reflect the actual state of various process parameters and control elements for remote control purposes.
2. Selective Data Presentation
In the nineteen sixties the complexity of the technical installations grew considerably. Consequently the central control panels became so large that these were no longer manageable. To overcome these problems, selective data presentation systems were introduced.
These systems used the switching methods employed by telephone switchboards. The mainly digital signals(status indication and switching commands)were no longer wired directly to the control panel but were collected in so-called data gathering panels(DGP's), or also called substations. These DGP's were connected to the central control panel via multi-core cables. The number of conductors in the cable links was lower than the number of data points being relayed. This was made possible by connecting the data points to multiplexed system with selection options.
he beginning of the nineteen
seventies, developments in electronics and communications led to the internal
transformation of these so-called Building Automation systems.
Although the external structure
remained the same, the matrix switching relay techniques in substations were
replaced by digital switching techniques. This made it possible to replace the
multi-core cables with two or four core serial links that could also be used to
transmit digitized analogue signals. The central control panel was replaced by
a computer system with a monitor display and keyboard, and a printer replaced
the analogue recorders. Computer systems and software were developed especially
for this purpose.
As a result of the limited
processing capabilities, the functionality of these systems was limited to the
presentation of process statuses and values and alarm reporting functions. As a replacement for the mimic diagrams slide
projection systems were sometimes added, on which process diagrams and floor
layouts could be displayed.
3- Energy Saving
After the energy crisis of 1973
there was an urgent need to reduce energy consumption as far as possible.
Making use of the capabilities the central computer of the Building Automation
Systems could provide, many energy
saving functions were developed and
integrated into the
Building Automation Systems. Functions such as optimization, night purging
and time- and event- triggered switching programs. Also, the reporting
capabilities of the system were enhanced to provide information regarding
energy usage and to show the effects of energy conservation measures.
4-
Management Functions
The need for more detailed
information grew as building management efficiency became more important. It
became clear that a Building Automation System offered more potential than
simply reducing energy costs. The reporting
functions were considerably expanded and other management tasks such as fire
and intruder detection and access control were added to the Building Automation
Systems.
The most important reason for
this integration was the use of the expensive central computer system as
efficiently as possible.
The building management tasks are now being distinguished as
follows:
-
Installations management:
The operation and control (from a
central point) of technical installations and the collection of information for
management and maintenance purposes.
-
Energy management:
The implementation of
energy-saving measures and the collection of information on the results, for
control and adjustment purposes.
-
Risk managements:
The complete and systematic
management of risks posing a threat to the business or organization, in an
economically responsible manner.
5-
Standard
Computer Systems
As a result of the expansion of
management tasks, it became necessary to connect more and sometimes specialized
operator stations. In addition, there was a requirement to be able to collect
data such as alarm reports and measurement results over a given period and
store these for later analysis. This required special provisions such as hard
disk storage facilities. Systems that previously used the dedicated computer
systems were altered so that standard mini-computers could be used as the
central system. Later on color graphic displays were added to replace the slide
projection equipment to display process diagrams and curve plots. Out of this,
a distinctly hierarchical system structure evolved with the central computer
(the master) at the highest level and below that, the substations (the slaves).
6- Intelligent Substations
Up to this time the main function
of the substations was to collect data at the local level, digitize these and
relay them to the central computer through serial link. In the second half of
the nineteen seventies micro-processors were being implemented in the
substations to provide local processing capabilities. A number of functions, until
then still carried out by the central computer, were transferred to the
substations. This marked the birth of the intelligent substation. At first this
intelligence was mainly restricted to the detection of alarms and deviations
from analogue alarm limits, or the conversion and sometimes linearization of
analogue measurements into digital signals. To utilize the still expensive
microprocessor technology efficiently these substations had a modular
construction, enabling connection of as much as possible input and output
functions (I/O modules).
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