Content uploaded by Luis Fonseca
Author content
All content in this area was uploaded by Luis Fonseca on Nov 25, 2015
Content may be subject to copyright.
Abstract—A very important part of the globally produced
energy is consumed in buildings, being an important share
frequently used in the HVAC systems. These ones are
increasing both in performance and in complexity, taking
advantage from the use of the recent advances in mechanical
and power electronic devices, particularly in the speed variation
field. However the improved efficiency only occurs while the
HVAC unit is working in the conditions specified by the
manufacturer, otherwise the energy consumption raises to
values considerably higher than the nominal ones. The adequate
maintenance enforces the system to run on its nominal
performance and the contrary has undesirable impact both in
the performance and in the system expected life time. Therefore,
HVAC field maintenance assumes a very important role in the
global building sustainability concept.
This work presents some results of an incorrect use of HVAC
and the associated electric energy overconsumption that can
assume values 50% higher than those that occur when the
installation is operated according to the adequate maintenance
plan.
Index Terms—Building sustainability, electric energy, HVAC
performance.
I. INTRODUCTION
Energy is a key issue to sustainable development (that,
according to the Bruntland Report [1] is development that
meets the needs of the present without compromising the
ability of future generations to meet their own needs)
indispensable for the many human activities (industry,
agriculture, etc.). Traditionally energy systems are based on
fossil fuel but its scarcity, irregular distribution, increasing
demand and consequent economic implications (e.g. price)
and environmental issues such as Climate Change have led to
a shift in energy policies. The 40% of energy-related CO2
emissions is derived from electricity generation [2].
Efficiency increase and use of Renewable Energy Sources
(RES) are the main features of today’s new energy policies.
In modern societies the use of energy is becoming more and
more common, and everyday new electric appliances reach
the market contributing to raise the energy demand. Also the
development of BRIC countries (Brazil, Russia, India and
China) contributes to intensify this problem relying in new
solutions and/or production paradigms [3].
Major energy consumers include transportation, industry,
and buildings. This last is responsible for a demand of over
40%. Particularly, the HVAC systems represent a significant
share of the global energy consumed in the building. More
important, if these systems are running out of the conditions
Manuscript received April 20, 2015; revised September 26, 2015. This
work was done in the framework of a MSc Thesis in Sustainable Energies,
and presented at ISEP, in November 2014.
The authors are with the School of Engineering of the Polytechnic
Institute of Porto, ISEP, Portugal (e-mail: mcf@isep.ipp.pt,
1100094@isep.ipp.pt, lmf@isep.ipp.pt, nsc@isep.ipp.pt).
clearly indicated by the manufactures the efficiency drops
and the energy consumption raises dramatically, with serious
consequences both at electric energy consumption and in the
expected system life time.
This paper is organized as follows: Energy use; Energy in
buildings; HVAC tested systems; Conclusions.
II. ENERGY ISSUE
The modern life style has been associated to the use of an
important amount of energy, and for many years consuming
energy was a synonym of high comfort level and good quality
of life. The rapidly growing energy consumption has also
raised concerns about the supply, exhaustion of resources and
environmental impacts on ozone layer depletion, climatic
changes and global warming. To reverse this situation several
measures have been proposed. Kyoto protocol was probably
the first agreement planned in order to invert this situation, on
a global scale that was rapidly followed by actions in all
continents. The European Union (EU) approved a first set of
targets that will be followed by a second set of new ones in
the so called Europe 2020. This is a 10-year plan proposed by
the European Commission in March 2010 to revive the
European economy. It aims at smart, sustainable, inclusive
growth with greater coordination of national and European
policy. The policy identifies five headline targets the EU
should take to boost growth and employment. One of the five
headline goals refers to the previously agreed target to reduce
greenhouse gas emissions by at least 20% compared to 1990
levels or by 30% if the conditions are right, increase the share
of renewable energy in final energy consumption to 20%, and
reach a 20% increase in energy efficiency. The 20-20-20
consists of an emissions and renewables target which is
legally binding while the energy saving target is not. The
Europe 2020 process which can help promote efficiency and
a sustainable growth agenda should not be used to replace
national targets and plans, especially at a time when greater
transparency, comparability and commitment is required [4].
New trends try to keep the achieved modern quality of life
style while lowering the level of energy used. Those includes
several procedures that can, in simple ways, be divide in two
set of objectives, one from the production side and other on
the consumer side:
The increase on the use of RES;
The rational use of energy.
The first has as outcome several measures from numerous
countries around the world, including EU, to implement and
to increase the efficiency and the share of RES in order to
contribute to increase the sustainability [5]. The major
drawback in the use of RES is its inherent unpredictability
that poses huge problems when using an electric energy
production paradigm based on the control. In fact, every time
one consumer turns on a device (e.g. a light) the demand
Buildings Sustainability: The HVAC Contribution
Manuel C. Felgueiras, Rute Santos, Luís M. Fonseca, and Nídia S. Caetano
Journal
of Clean Energy Technologies, Vol. 4, No. 5, September 2016
375
doi: 10.18178/jocet.2016.4.5.316
increase and the electric service provider should dynamically
and in real-time balance the demand with the production. In
order to do that the use of primary controllable energy
sources is crucial. Except for the hydro-storage energy, all
controllable energy sources are fossil derived.
In this scenario, the use of RES energy such as the
wind-based brings serial constrains resulting from its lack of
controllability. As consequence, typically are only injected in
the grid power values from the wind-based energy lower than
25% of the total power installed.
This percentage remains approximately constant even
when higher values of wind-based energy are available from
wind-energy farms. In this case we have available energy that
is not injected in the grid mainly because of the growing risks
associated with the continuity of service. The higher was the
over percentage, the more often was the associated wind-cuts,
i.e. the refuse in the use of wind-based energy. The solution
for this issue includes the use of a different electric energy
production paradigm that will take advantage of the use of
Information and Communications Technology (ICT).
However, all that issues and specifically the migration to a
different energy paradigm able to accommodate more, and
virtually unlimited, amount of electric energy, are currently
under development and consequently not feasible at
short-term.
The second includes several aspects including the
device/equipment performance, the user behaviors, the
equipment use conditions, etc. Efforts to increase the
efficiency are a matter considered transversely to all
industrial and household appliances. The most perceptible
face of this modification is the use of Light Emitting Diode
(LED) applied in lighting, TVs, Personal Computers (PC),
and a panoply of new and more efficient appliance devices. In
general, we can perceive that performance increase is often
associated with a complexity raise. As an example, in the past
traditional power supply generically used in all electronic
devices were based in the topology of the so called Linear
Power Supply, in which the first block was a power
transformer used to step-down the 110V or 230V voltages
from electric power grid to voltages compatible with the used
electronic, (e.g. 5V) typically used in digital circuits, such as
the mobile phone chargers. As attributes, those power supply
devices were heavy (due to the presence of the transformer)
and presented a global efficiency around 50%. Gradually
those equipment have been replaced by a new generation of
power supply devices based in the topology Switch-mode
Power Supply. These are much lighter, present considerably
higher level of complexity but also a global performance
never lower than 90%.
Generically we can perceive that the electronic and the ITC
technologies arenas have a raising importance in the modern
equipment. In fact they frequently are not essential to the
basic function of the equipment but are crucial if high
performance and low consumption is wanted. As an example,
if we compare modern cars with their ancestral models the
first present higher efficiency only possible to obtain due to
the use of massive electronic sensors and control systems.
The same conclusion is obtained when comparing new and
older light bulbs: higher efficiency but also higher
complexity. However, the introduction of electronics carries
also disadvantages as traditional linear loads are often
transformed in non-linear ones. This has negative impact on
the electric grid because increases the Total Harmonic
Distortion (THD) and for so, lowers the electric quality of
energy [6].
In general, electronics and ICT have special role in
systems, increasing their efficiency but also complexity. The
field maintenance is essential to maintain those systems in the
nominal conditions. The complexity of systems raises and for
so, technicians with higher skills level are needed.
III. ENERGY IN BUILDINGS
Buildings are crucial to a sustainable future as their design,
construction, operation, and the activities in buildings are
substantial contributors to energy-related sustainability
challenges. Consequently, reducing energy demand in
buildings can play one of the most important roles in solving
these challenges. In fact buildings activities are responsible
for approximately 31% of global final energy demand,
approximately one-third of energy-related CO2 emissions,
approximately two-thirds of halocarbon, and approximately
25–33% of black carbon emissions. Also energy-related
problems affecting human health and productivity take place
in buildings, including mortality and morbidity due to poor
indoor air quality or inadequate indoor temperatures.
Therefore, improving buildings and their equipment offers
one of the entry points to addressing these challenges [7].
The global energy demand has been usually grouped in a
few main areas such as industry, transports and other that
include the energy consumed in buildings. The share of
energy used in each area is continuously changing but we can
denote that the share of energy used in buildings is increasing.
In fact, this last has assumed so high importance that is
currently identified as one independent share. Energy
efficiency in buildings is today a prime objective of the
European Commission that has launched the Greenbuilding
programme, aiming at raising awareness and triggering
additional investments in energy efficiency and renewable
energy among owners in new and refurbished non-residential
buildings. As a result of the participation of more than 650
buildings that have included better insulation, more efficient
heating, cooling or lighting devices, control systems and
energy management, the programme is saving more than 514
GWh per year [8]. From that, an important part is due to the
HVAC systems. With the implementation of the Ecodesign
Directive, it is expected that by the end of the year 2020 about
11 TWh of energy can be saved each year, only due to the use
of more efficient HVAC systems [8].
Among the building services the growth in HVAC energy
systems use is important, achieving 50% of the total building
energy consumption.
In the EU the total amount of energy produced is mainly
consumed by three sectors as represented in Fig. 1 [9].
In the U.S. every year, nearly half (47.6%) of all energy
produced is consumed by the Building Sector – about the
same amount of energy consumed by both transportation
(28.1%) and industry (24.4%) combined sectors [9]. As
shown the share of energy consumed in buildings represents
about 40%. Accordingly [9] the global contribution from
buildings towards energy consumption, both residential and
commercial has progressively increased reaching values
Journal
of Clean Energy Technologies, Vol. 4, No. 5, September 2016
376
between 20% and 40% in developed countries, and has
exceeded the other major sectors: the industrial and
transportation. In terms of primary energy consumption,
buildings represent around 40% in most IEA countries. The
U.S. Energy Information Administration (EIA) now reports
that, in coming years, Building sector energy consumption
will grow faster than that of industry and transportation.
Between 2012 and 2030, the EIA reports, total Building
sector energy consumption will increase by 4.74 Quadrillion
Btu (QBtu). Industry will grow by 3.33 QBtu and
Transportation is expected to decrease by 0.37 QBtu. To put
these projections into perspective, 1 QBtu is equal to the
delivered energy of thirty-seven 1000-MW nuclear power
plants, or 235 coal-fired power plants at 200-MW each [10],
[11].
Fig. 1. Share of the energy consumed by household and services in EU.
For counteracting this state it is necessary to use new
technologies and techniques that point the ideal situation, i.e.,
an energetically self-sufficient building. This scenario is no
longer as far as it has been in the near past. The so called Zero
Energy Building (ZEB) [12], [13] is under strong research at
present. This new buildings design involves assessing how
the building will integrate into its surrounding environment.
(e.g., if a building is near a mountain, this will determine
where the windows are placed to ensure maximum exposure
to sunlight in cold climate). The process also involves
working on the design and overall shell (roofs, walls,
windows) of the building. The last step is to use the most
efficient appliances and equipment [14].
One important step was done by the presentation of the
Energy Performance of Buildings (EPBD) Directive (2002
and recast in 2010). The EPBD addresses new buildings and
those undergoing major renovation (which amounts to 40%
of the EU energy use, 36% CO2 emissions). Both its
transposition and implementation have been slow. Its recast
in 2009 has strengthened the Directive but less than hoped, in
particular regarding to existing buildings, financing and
urgency of deadlines [15]. The other important step refers to
the adequate use of building equipment’s in which the
appropriate use of HVAC represents a significant portion of
energy used in buildings. Several projects intend to know in
what conditions HVAC are operating and how they can be
more efficient. The main idea consists on inspection of
HVAC systems through continuous monitoring in order to
later compare results and perform benchmarking [16].
In the next section we present comparative results of poor
and appropriate use of HVAC systems.
IV. HVAC STUDIED
The main objective of the HVAC is to (i) renew the air
inside (e.g. room, store, office. etc.) and (ii) control air
temperature. Depending on the season, the system should be
able to remove or introduce heat.
A. HVAC Principle
The HVAC system principle is presented in Fig. 2. The
system includes an air fan, an air cooler element, an air heater
element, air filter and additional elements such silencer
elements and pipelines. The air intake is a mixture of the air
input from the inside of the room and of the new air coming
from the outside of the room. This air mixture crosses the
filter and then the cooler element, the heater element, the fan
and finally is introduced in the room. The use of new air is
necessary to satisfy ventilation requirements whereas the
recirculated air is used to obtain performance benefits. Major
energy consumers include the chiller that supplies the cooler
element, the boiler that supplies the heater element and the
fan that is responsible for flowing all the air mass involved in
the process.
B. Tested HVACs
There were tested three different equipment, with very
different features (e.g. size, power, etc.) and designed for
different installation needs [17]. As a common characteristic
those equipment were used to service a single room.
New air
(fr om t he outsi de room)
Air
filte r Cool er Hea ter
Recircu lata d air
(fr om t he inside room)
Suppli ed air
(to th e inside roo m)
Energy
Fan
out
Fan
in
BoilerChille r
Fig. 2. HVAC system principle.
C. The Test Method
The test methodology intends to demonstrate the impact of
an adequate maintenance in HVAC equipment, particularly
the filter. The comparative test aims to demonstrate in what
way the filter changes HVAC behavior and how important
are the deviations from the nominal conditions when the
Journal
of Clean Energy Technologies, Vol. 4, No. 5, September 2016
377
system runs out from the reference manufacturer
requirements. The methodology used was based in the
measurement of a set of properties before and after the filter
replacement action is all equipment. The selected set of
properties is as follows:
Temperature in the recycled air input
System response time
New air flowrate
Recirculated air flowrate
Supplied air flowrate
Current absorbed by motor 1
Current absorbed by motor 2
The test method is based on the time needed to make the
room internal air temperature drop 1ºC. To perform this
operation it is necessary to measure the temperature in the
recycled air input and the time associated to the specified
temperature decrease.
The measured air flow rate in the three input/output intends
to compare the impact before/after the filter replacement.
The filter acts as an air flow obstruction and for so this
opposition rises as consequence of the filter clogging.
Therefore it was expected the resistant torque to rise as well
as the associated current in the electric motors fan.
Consequently, it was considered important to measure the
three currents in the AC motors.
D. Test Results and Discussion
As explained before, the proposed methodology was
applied to three HVAC systems and the results are presented
in Table I.
TABLE I: CHARACTERIZATION OF HVAC SYSTEMS TESTED
HVAC system under test
#1
#2
#3
Before
After
Before
After
Before
After
New air flowrate
(m3/h)
5 100
11 000
2 650
4 000
19 500
24 400
Supplied air flowrate
(m3/h)
5 200
12 000
2 700
4 100
19 500
24 400
Recirculated air
flowrate (m3/h)
4 900
9 000
2 400
3 800
18 000
23 000
Supplied air
temperature (ºC)
21.8
20.3
20.0
21.0
25.0
24.0
New air temperature
(ºC)
33.0
32.5
28.0
27.0
28.0
27.0
Recirculated air
temperature (ºC)
23.5
23.5
21.0
21.0
22.0
21.0
Recirculated air set
point (ºC)
22.5
22.5
20.0
20.0
21.0
20.0
System response time
(min)
4
1.45
3
1
18
11
Motor-in [RST
currents] (A)
5.30
5.40
1.5
1.5
12.7
12.9
Motor-out [RST
currents] (A)
2.80
2.90
0.8
0.8
12.0
12.2
Increased supplied air
flowrate (%)
130
52
25
Increased recirculated
air flowrate (%)
84
58
28
Decreased syst.
response time (%)
36
33
61
Table I presents some data collected directly from the
HVAC system under test, whereas the lower part shows some
calculations.
Let us examine the first example, the HVAC #1. As said,
the system set point corresponded to the recirculated air
temperature decreased by one degree. The recirculated air
temperature was 23.5ºC and for so the correspondent
recirculated air set point should be 22.5ºC.
After the maintenance operation, the increase supplied air
flowrate variation obtained was about 130% whereas
increased recirculated air flowrate was 84%. The decreased
system response time was only 36%, i.e. the new response
time is only 36% of the previous. The fan motors currents
remain approximately constant and for so the corresponding
input power. We did not use electric energy meters during the
tests but the electric energy is estimated by:
E = P . t
where P represents the electric power (i.e. W), t represents
the time interval (e.g. h = hour) and E represents the electric
energy (e.g. kW/h). In the analyzed example (HVAC #1) the
motors power remain constant while the new response time is
only 36% of the initial time. It is easy to calculate that we
obtain 64% of energy savings for the fan motors.
Therefore, the savings are directly linked to the decreased
system response time. Analyzing all the remaining tested
examples we can perceive similar figures although results are
dependent of the clogging filter level. In all the systems tested,
the relative energy saved is significant but the absolute
energy savings depends on the fan power that is linked to
dimension and also to the global power system.
These results are consistent with those obtained by Balaras
et al. [18], who concluded that adequate maintenance can
contribute to better quality of the indoor air exchange, as well
as to better control on indoor thermal conditions, therefore
with lower energy consumption.
V. CONCLUSION
The HVAC systems are responsible for a very important
share of the globally consumed energy. If they work under
the conditions indicated by the manufacturers the energy
consumed in under the nominal conditions. However, the
absence or inadequate maintenance makes the HVAC system
run out of those conditions. The energy consumption raises
and the expected equipment life-time can be significantly
reduced. Both situations are against the sustainability
guidelines and for so should be avoided.
These systems include several energy consuming parts.
This paper presented some data related to the importance of
adequate HVAC maintenance in field and the corresponding
electric energy savings for the HVAC electric fan due to
proper maintenance. As seen the inadequate maintenance
(that includes filter replacement) has a high importance and
can be responsible for the raising in energy consumption of
275%. This study does not include the energy in the boiler
and chiller.
Improvements and new directions of this work will include
the development of a new system that automatically displays
the need for filter replacement.
REFERENCES
[1] World Commission on Environment and Development, Our Common
Future, Oxford: Oxford University Press, 1987, p. 27.
[2] International Energy Agency. (February 2015). [Online]. Available:
http://www.iea.org/topics/electricity/
Journal
of Clean Energy Technologies, Vol. 4, No. 5, September 2016
378
[3] C. Felgueiras and F. Martins, “RES-Managing the unpredictability,” in
Proc. the 4th International Conference on Renewable Energy Sources,
Tatranské Matliare, High Tatras, Slovak Republic, 2013, pp. 179-182.
[4] European Environmental Bureau. (2015). Current EU Energy Saving
Legislation and other Instruments. [Online]. Available:
file:///C:/Users/Calos%20Felgueiras/Downloads/FACT%20SHEET%
202%20-%20Current%20EU%20Energy%20Legislation%20and%20
other%20instruments%20(10).pdf
[5] C. Felgueiras and F. Martins, “RES-Electricity in Europe – Policy and
support instruments,” in Proc. the 4th International Conference on
Renewable Energy Sources, Tatranské Matliare, High Tatras, Slovak
Republic, 2013, pp. 135-139.
[6] C. A. Petry, J. Moia, F. S. Pacheco, R. A. Gustavo, and M. C.
Felgueiras, “Streamlining power electronics teaching,” XI Congreso de
Tecnologías, Aprendizage y Enseñanza de la Electrónica (TAEE),
Bilbao, España, 2014.
[7] D. Ürge-Vorsatz, “Energy end-use: Buildings,” Global Energy
Assessment - Toward a Sustainable Future, Cambridge, UK:
Cambridge University Press, 2012, ch. 10, pp. 649-760.
[9] European Commission, EU Energy and Transport in Figures -
Statistical Pocket Book, 2014.
[10] U.S. Energy Information Administration. (2014). [Online]. Available:
http://www.iea.org/
[11] L. Pérez-Lombarda, J. Ortiz, and C. Pout, “A review on buildings
energy consumption information,” Energy and Buildings, vol. 40, no. 3,
pp. 394-398, 2008.
[12] P. Hernandeza and P. Kennyb, “From net energy to zero energy
buildings: Defining life cycle zero energy buildings (LC-ZEB),”
Energy and Buildings, vol. 42, no. 6, pp. 815-821, 2010.
[13] A. J. Marszala, P. Heiselberga, J. S. Bourrelleb, E. Musallc, K. Vossc, I.
Sartorid, and A. Napolitanoe, “Zero energy building – A review of
definitions and calculation methodologies,” Energy and Buildings, vol.
43, no. 4, pp. 971-979, April 2011.
[14] G. Li, Z. G. Huang, and H. B. Zhou, “The study on how to optimize
energy saving technology on central air-conditioning for existing
buildings,” Journal of Clean Energy Technologies, vol. 1, no. 4, pp.
339-341, 2013.
[15] S. Schimschar, S. Surmeli, and A. Hermelink, “Guidance document for
national plans for increasing the number of nearly zeroenergy
buildings,” European Environmental Bureau, 2013.
[16] Inspection of HVAC Systems through Continuous Monitoring and
Benchmarking. (2011-2014). [Online]. Available:
http://www.iservcmb.info/
[17] R. C. C. Santos, “Contribution of the building technical maintenance to
sustainability,” MSc dissertation on sustainable energies, ISEP, School
of Engineering, Polytechnic Institute of Porto, 2014.
[18] C. A. Balaras, E. Dascalaki, and A. Gaglia, “HVAC and indoor thermal
conditions in hospital operating rooms,” Energy and Buildings, vol. 39,
no. 4. pp. 454-470, 2008.
Manuel C. Felgueiras received the B.S. and Ph.D.
degrees in electrical and computer engineering from
the Faculty of Engineering, University of Porto, Porto,
Portugal, in 1987 and 2008, respectively. He started
his activity in 1994 as an assistant professor and later
on as an adjunct professor and researcher with the
Department of Electrical Engineering, School of
Engineering (ISEP), Polytechnic Institute of Porto
(IPP), Porto, Portugal.
His research interests at CIETI include design for debug and test of
mixed-signals, remote experimentation in e-learning and renewable energy
source.
Rute Santos obtained her B.S. degree in electrical
engineering: energy systems from the School of
Engineering, Polytechnic Institute of Coimbra in 1999
and MSc degree in sustainable energies from ISEP,
IPP, in 2014, respectively. She started her professional
activity in 2000 in the paper pulping industry, as the
chief in charge of the electricity and instrumentation
maintenance. In 2005, she started the activity as
maintenance contracts officer in the field of both
buildings in industrial environment and in the service sector.
Luís M. Fonseca is an adjunct professor at ISEP-IPP,
School of Engineering Polytechnic of Porto since
1989. He has a PhD degree in management from
ISCTE-IUL, Lisbon University Institute in 2012 and
was an electrical engineer in FEUP, the Faculty of
Engineering of the University of Porto in 1982. He is
an ASQ fellow with 15 years’ experience in systems
certification business in addition with senior manager
experience.
His research interests include quality, management, sustainability, social
responsibility and industrial engineering and management.
Nídia S. Caetano received her B.S. and Ph.D.
degrees in chemical engineering from the Faculty of
Engineering of the University of Porto (FEUP), Porto,
Portugal, in 1987 and 1996, respectively. She started
the teaching activity in 1992 as an assistant professor
and today is a coordinator professor with the CED, of
ISEP/IPP. From March 2013, she has been the
director of the master course on Sustainable Energies
of ISEP/IPP, in the MED.
Her research interests include biofuels (waste to energy: biodiesel,
bioethanol, biogas, combustion) either from waste biomass, oil or
microalgae; efficient use of solar energy for microalgae production;
valorization of solid waste and wastewater treatment, always using a
sustainability based approach.
Journal
of Clean Energy Technologies, Vol. 4, No. 5, September 2016
379
[8] Science for Energy. Joint Research Centre, Scientific and Technical
Research Series Luxembourg: Publications Office of the European
Union. [Online]. Available: http://Dx.Doi.Org/10.2788/88328
Energy Policy
