BEMS for VAV Systems Assignment

Running head: BEMS FOR VAV SYSTEMS 1
Bems For Vav Systems
Name
Institution Affiliation

BEMS FOR VAV SYSTEMS 2
Table of Contents
Introduction to VAV
systems..................................................................................................................
...............3
Technical analysis of VAV systems
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Advantages of BEM systems
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.6
Disadvantages of BEM systems
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Discussion...............................................................................................................
..............................................13
Comparison of energy saving in VAV and CAV
..............................................................................................18
Comparison of carbon emission in VAV and
CAV..........................................................................................18
Conclusion...............................................................................................................
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BEMS FOR VAV SYSTEMS 3
INTRODUCTION OF BEMS FOR VAV SYSTEM
Research shows that buildings in Hong Kong consume around 53% of the total energy
consumed in the country annually. Energy is a very scarce and expensive resource that should be
used economically. Building energy management systems have been developed to ensure
efficient energy consumption as well as improve on the comfort in the buildings. These systems,
also branded as building automation systems (BAS), are mostly computerized control systems
fitted in buildings to monitor and control the electrical and mechanical equipment in the building
such as fire systems, heating, ventilation and air conditioning systems (HVAC), safety systems
and lighting systems. Building ( Papanton, Kolokotsa, & Kalaitzakis (2015),page 69). Energy
management systems can also be described as a control system for a set of buildings or single
building that use disseminated microprocessors and computers to monitor, communicate as well
as store data. VAV refers to variable air volume. It is a type of HVAC system that varies the
airflow at a fixed temperature. This working mechanism differs from that of constant air volume
(CAV) where airflow is supplied at a variable temperature. The VAV systems distribute air at a
constant temperature and varying the amount of air supplied to every single space controls the
temperatures of the building. These systems are useful in large buildings that necessitate cooling

BEMS FOR VAV SYSTEMS 4
since they provide air at a constant temperature. The VAV system comprises of various
components such as the exhaust ductwork, air handling unit and the supply ductwork unit.
TECHNICAL CONTENT.
BEMS basically means building energy management which entails a variety of design options
involved in construction management of both residential and commercial buildings. This is a
method of managing and controlling of energy required for buildings.
VAV means variable air volume. This is a system of heating, ventilating and air conditioning
system (HVAC). A comparison to constant air volume systems (CAV), the VAV system
operates by varying the airflow at a set constant temperature whereas the CAV system operates
by supplying a constant airflow with varying temperatures (Martin 2013,page 43). The VAV
system directly relates to the BEMS due to the operation and efficiency input it brings in the
building industry. For an efficient building energy management system to be achieved a parallel
VAV system which corresponds to the system being should be installed.
Simple VAV systems have the components being a single supply duct that when in cooling mode
it functionally distributes air supply at a constant temperature of about 12.50 C (Hong S, 2006,
page 103). Managing the building energy requires air temperature to be maintained at a
constant value and the airflow rate thereby controlled to commensurate then rising and falling
heat energy in the surrounding thermal region being supplied with heat energy.

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Simple VAV systems have much efficiency and a maximized output per unit as compared to the
CAV systems more precisely on then temperature control. the CAV system operates by rotation
of a fan and a compressor at full capacity to enable the temperature drop by set limit and the
automatically the compressor turns off. The overall operation of the CAV system is practically
inefficient due to the challenge which comes to maintaining the temperature at the set point.
Building energy management is a key aspect which considers majorly the quantitative and
qualitative energy management in buildings. Simple VAV systems have an advantage of
conserving energy thereby increased energy savings. The fans control system is composed of
electronic variable speed-drives thus reducing the amount of energy consumed and this has a
general impact on the total cooling energy required for a specified building.
VAV system has a substantially increased dehumidification due to reduced airflow thus air is
cooled for a longer period of time and more air moisture condenses on the coils of the system.
When the room temperature is maintained perfectly the dehumidification and ample and
comfortable space conditions is attained (Baggini, 2012,page 50).
Fig 1.Showing a typical air handling unit. (Muennig, P. 2007)

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Green building design.
Most buildings account for an approximate of 40% of the total energy utilized and this results in
the overall carbon emissions in the atmosphere worldwide. It is evident that commercial
buildings contribute the largest proportion of this emission.
To minimize this effect in the atmosphere, buildings have been modernly designed efficiently at
the planning stage whereas the existing buildings can be rejuvenated to improve the energy
consumption and costs incurred. For a greater approach to the energy management to achieve
better energy efficiency in the building there are numerous factors to be taken into consideration
(Moss, 2006. 52).
a. Energy recovery: this aims at the reuse of byproducts that originates from a predecessor
system processes as the input energy source at another system.
b. Energy substitution: the substitution of energy source aims at the utilization of a better
and much more efficient alternative that is likely to pollute the environment by a small
margin and optimize on the energy output.
c. Energy conservation; this is putting more efforts to reduce energy wastage and energy on
consumption, elimination of waste materials from energy production and subjecting
energy to more crucial utilization options.
Advantages of building energy management systems are the following:
 Substantial energy efficiency to maximum level
 Environmentally friendly and improves the environmental conditions.
 Emergency practices of fire and the general security is greatly enhanced.
 Higher standards of building technology.