Energy savings in compressed air systems a case of study

Abstract

The compressed air applications are highly used in the industrial sector due to its easy transportation, safety, purity, cleanliness and storage capacity. In many regions, compressed air system accounts for about 10% of the industrial electricity energy bill. However, compressed air is expensive because around 30% of the consumed energy is used for these systems in an industrial facility. Energy used to be lost as leaks, pressure drops, heat, misuse, among others. Several energy efficiencies measures help to improve energy savings in companies such as: pressure reduction, reduce the inlet air temperature, use a well-calculated capacity tank for storage, control heat recovery and reduce leaks, giving potential energy savings in a range between the 20% to 60%, with a return of investment not higher than two years. As result, this document analyzes the energy efficiency measures that can be considered for compressed air systems applications, calculates the energy saving potentials, and assesses a case of study in a company in the city of Barranquilla.

Full text

IOP Conference Series: Materials Science and Engineering
PAPER • OPEN ACCESS
Energy savings in compressed air systems a case of study
To cite this article: H Hernández Herrera et al 2021 IOP Conf. Ser.: Mater. Sci. Eng. 1154 012009
View the article online for updates and enhancements.
This content was downloaded from IP address 181.215.50.154 on 15/07/2021 at 02:46

Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution
of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Published under licence by IOP Publishing Ltd
EXPOTECNOLOGIA 2020
IOP Conf. Series: Materials Science and Engineering 1154 (2021) 012009
IOP Publishing
doi:10.1088/1757-899X/1154/1/012009
1
Energy savings in compressed air systems a case of study.
H Hernández Herrera1, D Patiño Villalba1, E Noriega Angarita2, J I Silva Ortega2 and
C A Caraballo Echavarría1.
1Facultad de
Ingeniería, Universidad Simón Bolívar, Barranquilla, Colombia
2Departamento de Energía, Universidad de la Costa, Colombia.
Abstract. The compressed air applications are highly used in the industrial sector due to its easy
transportation, safety, purity, cleanliness and storage capacity. In many regions,
compressed air
system accounts for about 10% of the industrial electricity energy bill. However, compressed air is
expensive because around 30% of the consumed energy is used for these systems in an industrial
facility. Energy used to be lost as leaks, pressure drops, heat, misuse, among others. Several energy
efficiencies measures help to improve energy savings in companies such as: pressure reduction,
reduce the inlet air temperature, use a well-calculated capacity tank for storage, control heat
recovery
and reduce leaks, giving potential energy savings in a range between the 20% to 60%, with a return
of investment not higher than two years. As result, this document analyzes the energy efficiency
measures that can be considered
for
compressed air systems applications, calculates the energy
saving potentials, and assesses a case of study in a company in the city of Barranquilla.
Keywords: Compressed air systems; energy efficiency; energy savings.
1. Introduction.
Global energy consumption has doubled over the past four decades, and this trend will continue with an
average annual increase of 1.5% in the period from 2018 to 2050 [1]. The industrial sector is consuming
about 50% of the world’s energy, while other sectors such as the residential and commercial are consuming
between 29 and 21% respectively [2]. In Colombia, the manufacturing sector is consuming around 30% of
the total energy, making it the second most consuming sector after transportation with 40% [3, 4].
The compressed air systems (CAS) in many industries worldwide represent around a 10% of the total
elect
ricity consumption as shown on f
igure 1. Commonly this system is used to operate plants and
instrumentation equipment due to its easy transportation, safety, purity, cleanliness, and storage capacity [5-
9]. Implementing these systems differs from the activity of every organization and its adequate usage
guarantees great energy savings. The major cause of energy loss are leaks, inappropriate pipeline settings,
small storage, pressure drops, and inadequate usage of the system. If energy efficiency measures (EEM) are
applied in these systems, it could translate into a reduced energy consumption between 20%
-
60%.
These factors prove that CAS can be one of the most important objectives for the EEM application in the
industrial sector [10-12]. A major energy saving, and the increase of efficiency could assure other benefits
such as the increase of production with a capital investment reduction, improvement of the product, decrease
maintenance costs; these advantages commonly are more representative than the energy-saving itself [13 -
15]. This research main purpose is to analyze the main EEM that could be applied for CASs and its
evaluation in a c
ase of study in the city of Barranquilla.

EXPOTECNOLOGIA 2020
IOP Conf. Series: Materials Science and Engineering 1154 (2021) 012009
IOP Publishing
doi:10.1088/1757-899X/1154/1/012009
2
Figure 1. Percentage of electricity consumption of CAS in different countries. Data Sources based on:
[5, 16-20].
2. Typical EEM in CASs.
2.1. Components o
f
a CASs.
CASs has two 2 sides defined as supply and demand sides. The compressor (which oversees the
increasing pressure), a storage humid tank, a dryer, a dry storage tank, and the filters located on the supply
side. While, on the demand side, the flow and pressure controls and the
transportation lines deliver the
amount of air to every machine based on its consumption specifications. Figure 2 shows the key elements
inside a CAS.
Figure 2. Description of the CAS sides and elements. Data source based on: [13, 14, 21].
2.2.
Leaks: Identification and measurement.
The most significant cause of energy loss in the CAS is leakages. In an adequate system they are between
5% to 10% of the compressed air production [10, 22]. However,
in the industry
the regular range for leaks
are in the range of 20% to 40% and without proper maintenance and use, it could reach up to 60% [23-25].
Commonly, leaks are found in the joints and connections of the compressed air pipelines, elbows, among
others. The leakages value could be registered using
two
procedures: the first one is for compressors with a
start/stop control and it comprises turning on the compressor when the system is without loads, the leaks
can be able to pressure drops, by which the compressor will run into a load-unload cycle; according to [17,
26], the total leakage (TL) measured in percentages are:

EXPOTECNOLOGIA 2020
IOP Conf. Series: Materials Science and Engineering 1154 (2021) 012009
IOP Publishing
doi:10.1088/1757-899X/1154/1/012009
3
% =
 +
 100
(1)
Where:
Tload – Time the compressor is in load mode.
Tdownload -
Time the compressor is in
download mode.
Other control strategies can be as follow: a pressure gauge (manometer) is placed downstream of the
receiver tank. The compressor is turned on without loads until it reaches the working pressure P1. Then, t
he
compressor is then turned off measuring the time (t) until that the system drops of until a half of the working
pressure P2. It is necessary to know the system volume (V) including the storage tank capacity. The value
of the loss flow (
) measure in (m3/s) and can be calculated using the equation 2 as follow:

=(−
)
 1,25
(2)
Where:
P0 - atmospheric pressure
In equation 2, the multiplier factor 1,25 corrects the leak to the normal system pressure. The annual
energy saving in a start/stop control can be expressed as:
ES=AECT
%
(3)
Using
other control strategies
ES=LSECOPH
(4)
Where,
OPH: is the operating hours in year (h/year).
SEC: is the specific energy consumption, (kWh/m3).
AEC: Annual energy consumption in the CAS.
2.3. Storage Tanks Volume
The storage tanks in a CAS have several functions including: providing storage capacity to avoid short
start/stop cycles, to condense air humidity, to cover periods of pressure peaks, to keep the system’s pressure
and to allow the systems control to work with more efficiency [24]. The compressed air provider companies
recommend the use of two storage tanks, a humid and a dry tank. The first is placed between the
dryer and
the compressor while the other is located next to the dryer [25]. Sometimes, this makes more sense to have
additional storage tanks near the applications with high consumption of air and intermittent usage [24].
Some authors recommend the tank volume should be between 12-120 m3 for each cubic meter per second
of air delivered by the compressor at full load as shown in figure 3 [21, 27, 28].

EXPOTECNOLOGIA 2020
IOP Conf. Series: Materials Science and Engineering 1154 (2021) 012009
IOP Publishing
doi:10.1088/1757-899X/1154/1/012009
4
Figure 3. Recommended relative receiver tank volume in compressed air systems.
The annual energy saving for an adequate air receiver volume is:
 =
5
2.4. Suction Temperature
Compressors are in a separate room inside the factory, or adjacent shelters, built specifically for this
equipment. Most of them suck the air in that same room, at temperatures higher than the normal environment
temperature, due to the heat generated by the compressor itself. The compression of the air becomes more
inefficient as the suction temperature increases [29, 30], the potential savings from this concept can be
calculated as:
=−
+273
(6)
Where:
T1 - average compressor air suction temperature.
T0 - average environment air temperature.
The savings produced by the reduction of the air intake temperature
are calculated
as:
 =

(7)
3. Case Study
The plant analyzed is in the city of Barranquilla and it use is the glasses manufacture for the construction
sector. To determine the potential savings in the compressed air systems, the efficiency measures previously
discussed will be evaluated.
3.1 Leakage
The compressor has a start/stop control, so the leakage is calculated using equation (1). The
corresponding measurements were carried out where it was determined that in the company the values of
the leaks correspond to 33%. If we consider
that a system with a proper functioni
ng, the percentage of
leakage allowed is 5%, we can state that there is a considerable saving potential in this case of 28%.
Using equation (3) potential savings could be determined, considering that the monthly electricity
consumption is 10,852 kWh/month. ES=T
%
ES=10852kWh/month0,28
%
ES= 3038,56 kWh/month

EXPOTECNOLOGIA 2020
IOP Conf. Series: Materials Science and Engineering 1154 (2021) 012009
IOP Publishing
doi:10.1088/1757-899X/1154/1/012009
5
If the kWh cost is 451,28 COP/kWh, the company has an annual potential saving of 16.454.896 COP.
3.2 Storage Tanks.
The company has an Atlas Copco GA55P compressor, which has 56 kW and handles a flow (Q) of 0.128
m3/sec, the system has a storage tank with a
volume (V) of
1m3. The value of the relative receiver tank
volume is.
∗=
=1
0,128
 =7,81 ()


In figure 4 load/unload compressor cycles are shown. The relative consumption conditions are at 53%.
Figure 4. Power consumption of compressor.
Figure 5 shows the relative receiver tank volume for the plant. As seen that it is below the recommended
value giving by manufacturers.
Figure 5
. Relative receiver tank volume for the plant.
If the company buys a storage tank to achieve the relative volumes recommended by the manufacturers
there would be savings in energy consumption (ESPC) caused by increasing the relative storage values of 12
% figure 6.

EXPOTECNOLOGIA 2020
IOP Conf. Series: Materials Science and Engineering 1154 (2021) 012009
IOP Publishing
doi:10.1088/1757-899X/1154/1/012009
6
Figure 6. Potential savings with the required receiver tank volume.
Using equation (5) potential savings are determined as follow:
 =
 =10852/0,12
 = 1302.24 /
Considering the kWh cost, the company has an annual savings potential of 7.052.098 COP.
3.3 Temperature.
For the case study analyzed, the compressor location is not appropriated because it is located on a second
floor, above the oven and next to the electric motor of the oven's fan. Temperature measurements were taken
in unison inside the compressor room and the ambient temperature for a week, resulting in an average
suction temperature of 10 degrees above an ambient temperature at the company, reaching a difference of
15 degrees at the most critical times. The reduction in energy consumption as a result of the reduction in air
temperature is calculated as follows:
=42−32
42+273
=3,
1
%
We calculate the savings from reducing the inlet temperature according to equation (7).
 =

 = 10852kWh/mes  0,031= 336 /
Considering the cost of kWh, the company has an annual savings potential of 1.821.792 COP.
4. Conclusion.
The CASs in industry commonly consumes about 10% of the billed electricity, highlighting that they are
inefficient systems
where
only between 10% to 30% of the produced air is used, implementing EEM such
as reducing the improper use of compressed air, reducing the pressure of the compressors, lowering the air
intake temperature, ensuring an adjusted storage capacity, obtaining a residual heat recovery from the air
compressor and reducing leaks can provide savings in a range between
20% to 60% with
a return of
investment not higher than two years which makes it one of the main systems to be used by companies and
countries when are considered strategies to reduce energy consumption. Also, this measure provides other
benefits such as the increase of production with a lower capital investment, maintenance reduction, quality

EXPOTECNOLOGIA 2020
IOP Conf. Series: Materials Science and Engineering 1154 (2021) 012009
IOP Publishing
doi:10.1088/1757-899X/1154/1/012009
7
in final product improvements, and maintenance reduction; otherwise it is important to emphasis that these
advantages are better than common electricity bill savings.
The company analyzed is dedicated to glass manufacture for the building sector where was evaluated all
the compressed air systems located in the production area giving all possible recommendations that could
be applied energy savings. According to this research could be estimated that exist a potential energy saving
of 28% if the company applies measure to reduce leakages.
If a storage tank is purchased to bring the relative
volumes to the recommended values by the manufacturers it can be reached potential energy savings
reaching 12% and if the temperature in the compressor can be reduced to the environment it can be reached
potential energy savings equal to 3.1%. The potential energy savings of the company can reach a total energy
saving of 43.1% which is equal to 25.328.786 COP per year.
5. References
[1]
Wu, X. D., Guo, J. L., Ji, X.,
and Chen, G. Q. (2019). Energy use in world economy from household-
consumption-based perspective. Energy policy, 127, 287-298.
[2] BP Energy. (2019), BP Energy Outlook. Available from: https://www.bp.com/content/dam/bp/
en/corporate/pdf/energyeconomics/energy-outlook/bp-energy-outlook-2018.pdf. [Last accessed on
20
20 Jun 28].
[3] Chikunov, S. O., Gutsunuk, O. N., Ivleva, M. I., Elyakova, I. D., Nikolaeva, I. V. and Maramygin, M.
S. (2018), Improving the economic performance of Russia’s energy system based on the development
of alternative energy sources. International Journal of Energy Economics and Policy, 8(6), 382-391.
[4]
UPME (2018), Balance Energético Colombiano. BECO. Available from:
http://www1.upme.gov.co/InformacionCifras/Paginas/BalanceEnergetico.aspx.[Last accessed on 2019
Feb 14].
[5] Benedetti, M., Bertini, I., Introna, V. and Ubertini, S. (2018). Explorative study on Compressed Air
Systems’ energy efficiency in production and use: First steps towards the creation of a benchmarking
system for large and energy-intensive industrial firms.
Applied energy
, 227, 436-448.
[6] Radgen, P. and Annegret, C. (2003), Efficient Compressed Air a Successful Campaign for Energy
Efficient Compressed Air Systems in Germany. Saint-Raphaël, France: ECEEE 2003 Summer Study
Proceedings.
[7] Dos Santos Mascarenhas, J., Chowdhury, H., Thirugnanasambandam, M.,Chowdhury, T. and Saidur,
R. (2019), Energy, exergy, sustainability, and emission analysis of industrial air compressors. Journal
of Cleaner Production
, 231, 183-195.
[8] Taheri, K. and Gadow, R. (2017), Industrial compressed air system analysis: Exergy and
thermoeconomic analysis. CIRP, Journal of Manufacturing Science and Technology, 18, 10-17.
[9] Yin, Y., Zheng, B., Yang, C. and Zhang, X. (2015), A proposed compressed air drying method using
pressurized liquid desiccant and experimental verification. Applied Energy, 141, 80-89.
[10] European Commission. (2009), Reference Document on Best Available Techniques
for
Energy Efficiency. Available from: http://www.eippcb.jrc.ec.europa.eu.
[11] Hernandez-Herrera, H., Silva-Ortega, J. I., Martínez Diaz, V. L., García Sanchez, Z., González García,
G., Escorcia, S. M., and Zarate, H. E. (2020). Energy savings measures in compressed air systems.
International Journal of Energy Economics and Policy
10 (3), 414
-422
[12] Bonfàa, F., Salvatorib, S., Benedettic, M., Intronad, V. and Ubertinie, S. (2017), Monitoring
compressed air systems energy performance in industrial production: Lesson learned from an
explorative study in large and energy-intensive industrial firms. Energy Procedia, 143, 396-403.
[13] Nethler, T. (2018a), Linking energy efficiency measures in industrial compressed air systems with non-
energy benefits
-a review. Renewable and Sustainable Energy Reviews, 89, 72-87.

EXPOTECNOLOGIA 2020
IOP Conf. Series: Materials Science and Engineering 1154 (2021) 012009
IOP Publishing
doi:10.1088/1757-899X/1154/1/012009
8
[14] Nethler, T., Parra, R. and Thollander, P. (2018), Implementation of energy efficiency measures in
compressed air systems: Barriers, drivers and non-energy benefits. Energy Efficiency, 11(5), 1281-
1302.
[15] Fleiter, T., Hirzel, S. and Worrell, E. (2012), The characteristics of energy efficiency measures a
neglected dimension. Energy Policy, 51,
502
-513.
[16] Šešlija, D., Ignjatović, I., Dudić, S. and Lagod, B. (2011), Potential energy savings in compressed air
systems in Serbia. African Journal of Business Management, 5(14), 5637-5645.
[17] Saidur, R., Rahim, N. A., and Hasanuzzaman, M. (2010). A review on compressed-air energy use and
energy savings. Renewable and sustainable energy reviews
, 14(4), 1135
-1153.
[18] UPME Corpoema. (2014), Determinación y Priorización de Alternativas de Eficiencia Energética Para
los Subsectores Manufactureros Informe Final Códigos CIIU 19 a 31. Vol. I. Colombia. Available
from: http://www.upme.gov.co/estudios/2014/informefinalvolumen_1.pdf. [Last accessed on 2020 Jul
2].
[19] UPME Corpoema. (2014a), Determinación y Priorización de Alternativas de Eficiencia Energética Para
los Subsectores Manufactureros Informe Final Códigos CIIU
19 a 31. Vol. II. Colombia. Available
from:http://www1.upme.gov.co/demandaenergetica/determinacioneficiencia/informe_final_volumen
_2.pdf. [Last accessed on 2020 Jun 17].
[20] UPME Incombustion. (2013), Determinación del Potencial de Reducción del Consumo Energético en
los Subsectores Manufactureros Códigos CIIU 10 a 18 en Colombia. Available from:
http://www.upme.gov.co/demandaenergetica/INFORMEIII_caracterizacion_energeticaVerpub.pdf.
[Last accessed on 20
20 Jun 12].
[21] DoE, U. S. (1998). Improving Compressed Air System Performance, a Sourcebook for Industry.
Prepared for the US Department of Energy, Motor Challenge Program by Lawrence Berkeley National
Laboratory (LBNL) and Resource Dynamics Corporation (RDC).
[22] Castellanos, L. M., Hernández Herrera, H., Silva Ortega, J. I., Martínez Diaz, V. L., and García
Sanchez, Z. (2019). Potential energy savings and CO2 emissions reduction in Colombia compressed air
systems. https://doi. org/10.32479/ijeep. 8084.
[23] Abdelaziz, E.A., Saidur, R. and Mekhilef, S. (2011), A review on energy saving strategies in industrial
sector. Renewable and Sustainable Energy Reviews, 15(1), 150-168.
[24] Yang, M. (2009). Air compressor efficiency in a Vietnamese enterprise. Energy Policy, 37(6), 2327-
2337.
[25]
Dudić, S., Ignjatović, I., Šešlija, D., Blagojević, V.,
and Stojiljković, M. (2012). Leakage quantification
of compressed air using ultrasound and infrared thermography. Measurement, 45(7), 1689-1694.
[26] Dindorf, R. (2012). Estimating Potential Energy Savings in Compressed Air Systems”. Procedia
Engineering. 39, 204-211.
[27] Compressed Air System Guide Designing Your Compressed Air System Provided as a Service by
Kaeser Compressors, Inc. 2010. http://www.kaeser.com.co
.
[28] Olszewski, P., and Borgnakke, C. (2016). Influence of volumetric capacity on energy consumption in
oil-lubricated compressed air systems. Journal of Thermal Science and Engineering Applications, 8(4),
041007.
[29] UPME (2016), Plan de acción indicativo de eficiencia energética 2017-2022, una realidad y
oportunidad para Colombia (PAI Proure 2017-2022), Available from:http://www1.upme.gov.co/
DemandaEnergetica/MarcoNormatividad/PAI_PROURE_2017-
2022.pdf. [Last accessed on 2018 Jan
29].
[30] Kluczek, A., and Olszewski, P. (2017). Energy audits in industrial processes. Journal of cleaner
production, 142, 3437-3453.