Flavia Melo Menezes
Federal University of Bahia (UFBA), Brazil
E-mail: flaviamelomenezes@gmail.com
Maria Fátima Góes
Federal University of Bahia (UFBA), Brazil
E-mail: mfbgoes@gmail.com
Ricardo Araújo Kalid
Federal University of Southern Bahia (UFSB), Brazil
E-mail: ricardo.kalid@gmail.com
Armando Hirohumi Tanimoto
Federal Institute of Education, Science and Technology
of Bahia (IFBA), Brazil
E-mail: armando.tanimoto@gmail.com
José Celio Andrade
Federal University of Bahia (UFBA), Brazil
E-mail: jcelio.andrade@gmail.com
Submission: 15/05/2017
Accept: 17/05/2017
ABSTRACT
The burning of fossil fuels majorly contributes to
the increase in global warming, and it represents 93% of greenhouse gases
emissions in the chemical industry. Most of the energy demand in this sector is
associated with steam systems, where 1/3 of the energy efficiency opportunities
are located in its distribution system. However, most of the literature focuses
on the design of new systems. Those that deal with existing systems, not always
use simple and available methods. Furthermore, they address energy losses of
steam systems only due to thermal insulation, ignoring those due to leakages of
traps. Given this context, the purpose of this paper is to determine the
economic feasibility of an energy efficiency project for a steam distribution
system in a chemical industry, located in the metropolitan region of Salvador,
Brazil. First, the energy lost in the steam distribution system through heat
insulation and steam traps was estimated by applying thermodynamic principles,
and technic consulting, respectively. Then, investments were estimated using
commercial prices for new thermal insulation and steam traps. Finally, an
economic evaluation of the improvement project was made, through the
construction of a cash flow, and calculation of economic indicators: payback
time, net present value (NPV), and internal rate of return (IRR). Economic
indicators showed that the project is economically viable. The NPV and IRR
reached approximately 5 million reais, and 66% per year, respectively.
Additionally, this project also had social and environmental benefits, such as
a reduction in greenhouse gases emissions, and increased local water
availability.
Keywords:
economic feasibility; energy efficiency; steam distribution system.
1. INTRODUCTION
Currently,
the delivery of high quality thermal energy in large quantities is essential in
many processes of manufacturing goods and services. Steam systems generally
provide this thermal energy, and it is largely derived from the burning of
fossil fuels (CEB; FUPAI/ EFFICENTIA, 2005a). This is worrying, as its burning
is a major factor that contributes to increase in global warming.
The
Intergovernmental Panel on Climate Change (IPCC) states that anthropic climate
warming is unquestionable, and if current pace is maintained, irreversible
environmental damages to the planet may occur (IPCC, 2014). At the 21st
Conference of Parties (COP-21) of the United Nations Framework Convention on
Climate Change (UNFCCC), countries agreed to restrict greenhouse gas emissions
(GHG) as soon as possible, and then make major reductions by 2050, in order to
limit the global temperature increase well below 2°C (UNFCCC, 2015). Analysts
suggest that a reduction in emissions should be done initially by decreasing
the amount of burning of fossil fuels (WYNN, 2015).
The
Brazilian Chemical Industry Association (ABIQUIM) states that the theme is
relevant to the sector, because chemical industries use materials rich in
carbon as raw material, as well as energy sources (BRAZIL, 2010). Data from the
System Study Greenhouse Gas Emissions Estimates shows the industrial sector
emissions related to production processes, use of fossil fuels and treatment of
effluents, totaling 23% of Brazilian GHG emissions in 2014 (SEEG/OC, 2016).
Thirteen percent of this amount came from chemical industries, whose use of
fossil fuels accounted for 93% of their emissions (SEEG/OC, 2016).
According
to the Ministry of Mines and Energy, about 90% of the fossil fuel used by the
chemical industry is associated with steam production, which represents a
consumption of more than 4 million tons of equivalent oil (BRAZIL, 2005;
BRAZIL, 2015). However, about 20% of this fuel can be saved in steam systems,
where one third of the energy efficiency opportunities are located in its
distribution system (CEB; FUPAI/ EFFICENTIA, 2005b).
In
addition to fuel, water is also an important raw material that must be taken
into account in energy efficiency projects for steam systems. Brazil has a
water deficit, and the northeast region, in particular, suffers increasing
water stress in the semiarid region. The National Water Resources Policy
establishes that in a situation of scarcity, the priority use of water
resources is for human and animal consumption (BRAZIL, 1997). Therefore,
industrial activities would be among the first ones to be hit by water
scarcity. In this context, measures for rational use of water by industries are
even more relevant.
In
general, the literature on energy efficiency projects for heat distribution
systems focus on the design of new systems (ÇOMAKLI; YUKSEL; ÇOMAKLI, 2004;
OZTUK; KARABAY; BILGEN, 2006; CHEN; LIN, 2011; KUZNETSOV; POLOVNIKOV, 2011;
DALLA ROSA; SVENDSEN, 2011; LI; SVENDSEN, 2012; SANAEI; NAKATA, 2012; KAYFECI,
2014; POLOVNIKOV; GUBINA, 2014; POLOVNIKOV; GUBANOV, 2015). Those who approach
the subject in existing systems, do so with the aid of measuring devices,
laboratory tests, and mathematical simulations, from which they generate data
to evaluate heat loss in the operational condition of facilities (KRUCZEK, 2013;
TSYGANKOVA; DMITRIENKO, 2014).
Kruczek
(2013) determined the annual energy loss of a steam distribution system by
measuring the external temperature of thermal insulation using a thermovision
camera, as well as laboratory tests to define the emissivity coefficient of the
pipe cover. Tsygankova and Dmitrienko (2014), in turn, used mathematical
modeling to calculate the energy loss, considering the operating conditions of
the thermal insulation and heat conductors.
Both
studies focus on heat loss exclusively through thermal insulation (KRUCZEK,
2013; TSYGANKOVA; DMITRIENKO, 2014). Therefore, no studies that identify and
estimate heat loss through thermal insulation and steam traps were found. This
joint analysis is interesting because they can be sources of great heat loss in
steam distribution systems.
Energy
efficiency projects involves time and resources, which often companies do not
have or have no interest in spending immediately. Thus, energy losses through
thermal insulation and steam traps can be preliminarily estimated by applying
the principle of energy conservation/ heat transfer by conduction on
cylindrical surfaces, and by means of technical advice, respectively. Then, an
economic feasibility study of the energy efficiency project can be carried out,
from which a company has the elements to decide whether to carry out a more
detailed study on the subject.
Nonetheless,
energy efficiency is still a great challenge for Brazil. It is the second worst
country in terms of energy efficiency among the 23 largest energy consumers in
the world; furthermore, Brazil has a poor prognosis, because its energy
efficiency has been stagnant in the last decade (ACEEE, 2016). Therefore,
however simple they might be, energy efficiency projects should be encouraged
and implemented in order to promote Brazil's progress in this area.
Given
this context, and the interest of a chemical industry located in the
metropolitan region of Salvador, Brazil, this study could be carried out.
Therefore, the purpose of this paper is to determine the economic feasibility
of an energy efficiency project for a steam distribution system in a chemical
industry.
This
paper has the following structure. It presents in section 2: main concepts
studied for energy loss estimates through steam traps and thermal insulation,
and techniques to carry out economic evaluation of this project. Next, the
results are presented and discussed in section three, considering data of the
steam distribution system of the chemical industry. Finally, conclusions and
final considerations about the economic feasibility of the energy efficiency
project are presented in section 4.
2. METHODOLOGY
The
methodologies for heat loss estimates by thermal insulation and steam traps, as
well as the techniques and indicators adopted for economic analysis, are
described in this section. In order to refer to the chemical industry whose
data were used in this study, the expression Efficient Industry was adopted.
2.1.
Energy
Loss Estimate in the Steam Distribution System
The
methods for energy losses estimates by steam traps and thermal insulation are
presented in this section, using ton of steam as unit.
2.1.1. Energy
Loss Estimate through Steam Traps
In
order to identify and quantify steam leaks, manufacturers of steam traps should
be contacted as they provide services with specific instruments for this
purpose (CEB; FUPAI/ EFFICENTIA, 2005a). Accordingly, the Efficient Industry hired Spirax Sarco Industry and Commerce (Spirax
Sarco) and Techsol Industry, Commerce and Services (Techsol) to evaluate the
operating conditions of its steam traps, in different moments (SPIRAX SARCO,
2006; TECHSOL, 2016).
Spirax
Sarco (2006) used the ultrasonic vibration analyzer UP-100 in the inspection of
steam traps. It is an electromechanical transmitter, which converts mechanical
vibration into an audible small-intensity electrical signal that identifies the
steam trap condition (SPIRAX SARCO, 2006). Techsol assessment, in turn,
presented current data on the operating conditions of the steam traps, although
it did not quantify the steam leaks (TECHSOL, 2016).
2.1.2. Energy
Loss Estimate through Thermal Insulation
Depending
on thermal insulation conditions, the actual heat loss may be at least 150%
greater than that originally estimated (TSYGANKOVA; DMITRIENKO, 2014; KRUCZEK,
2013). The insulation of the steam distribution system of the Efficient Industry is about 40 years
old. Therefore, it has been considered to be degraded in order to allow a 150%
greater heat emission, compared to the design condition.
2.1.2.1.
Saturated
Steam Loss Estimate through Thermal Insulation
In
saturated steam systems, when part of the steam becomes condensate (liquid),
there is heat loss. In a new system where there are no steam leaks and the
steam traps work well; this energy loss usually occurs through thermal
insulation, because it is a cylindrical surface that conducts heat. In order to
calculate the rate of heat emission, some simplifications were made: the
conduction resistance of the tube wall and the convective resistance between
the steam and the inner wall of the tube were considered negligible (KRUCZEK,
2013). Consequently, it was assumed that the temperature of the internal
surface of the thermal insulation was the same as the steam temperature,
allowing heat emission rate estimate through the equation:
(1)
Where:
Q – heat emission rate (kJ/h);
k – thermal conductivity of thermal
insulation (kJ/m.h.°C);
l – pipeline length (m);
Ts – steam temperature
(°C);
Tei – external surface
temperature of thermal insulation (°C);
re – external radius of
thermal insulation (m);
ri – internal radius of
thermal insulation (m).
The
amount of condensate formed due to energy loss was assumed to be equal to the
amount of steam loss. Since steam operates under conditions of partial
saturation in the Efficient Industry,
its quality must be known, in order to estimate the annual steam loss through
the equation:
(2)
Where:
Ms – annual steam loss
amount (t);
Q – heat emission rate (kJ/h);
hv – specific enthalpy
of vaporization (kJ/kg);
X – steam quality (%).
2.1.2.2.
Superheated
Steam Loss Estimate through Thermal Insulation
In
new superheated steam systems, where steam leaks are negligible and steam traps
work well, energy loss through thermal insulation can be considered
proportional to temperature variation along the pipeline. According to Cengel
(2003), this variation can be between 1ºC and 5ºC in a standard system. In
order to estimate energy loss, it was considered that a standard superheated
steam system has 100m of pipeline length, and a 3ºC mean temperature variation.
In
open systems with steady flow, such as that occur in the steam distribution
system of the Efficient Industry, it
is possible to estimate energy loss from the energy conservation principle
(CEB; FUPAI/ EFFICENTIA, 2005a). Thus, as no work is performed, and kinetic and
potential energy difference is considered negligible, heat loss rate through
thermal insulation corresponds to steam enthalpy change along the pipeline.
Assuming a 150% higher heat emission rate due to thermal insulation degradation,
the variation of 4.5ºC / 100m was considered, using the equation:
(3)
Where:
Q – heat emission rate (kJ/h);
ms – steam mass flow
(kg/h);
hi, ho –
steam specific enthalpy at the inlet and outlet operating conditions of the
pipeline (kJ/kg)
l – pipeline length (m).
In
the Efficient Industry, steam is
produced in a boiler, where the water goes from an ambient condition of
temperature and pressure, to become a steam at 380°C temperature and 42bar
pressure. In order to estimate the equivalent steam loss amount, the energy
conservation principle was used once again, considering the enthalpy change in
the steam production process (CEB; FUPAI/ EFFICENTIA, 2005a). Thus, the annual
amount of steam loss could be estimated through the equation:
(4)
Where:
Ms – annual amount of
lost steam (t);
Q – heat emission rate (kJ/h);
hi – water specific
enthalpy in the initial condition (kJ/kg);
hf – water specific
enthalpy in the final condition (kJ/kg).
The
mathematical expressions presented to estimate the losses of saturated and
superheated steam through thermal insulation considered simplifications in the
system. Only main pipelines were analyzed in this study in order to reduce the
error in estimates.
2.2.
Economic
Evaluation of the Project
The
economic feasibility study is based in the income generated from the energy
saved in the steam distribution system from the implementation of the energy
efficiency project. This evaluation involves problem modeling in a cash flow,
from which it is possible to calculate and analyze the economic indicators.
2.2.1. Cash
flow
Cash
flow presents the movement of resources over time, that is, cash inflows and
outflows. One of the most important aspects in the investment analysis is the
estimate of the values that will make up the cash flow (ASSAF NETO, 1992). The Efficient Industry provided the
reference data for steam production, total cost, variable cost, and fixed cost;
while the amount of steam saved by the energy efficiency project was the result
of the calculations presented in Section 2.1. Cash flow was calculated using
the equation:
(5)
Where:
CFi – Cash flow in year i (R$)
Tr – Total reference
cost (R$/ year);
Fai – Fixed cost after
investment, in year i (R$);
Vai – Variable cost
after investment, in year i (R$),
wherein:
(6)
Where:
Pr – Steam reference
production (t/ year);
SSi – Saving steam after
project implementation in year i (t);
Vr – Variable reference
cost (R$/ year).
2.2.2. Economic
Viability Indicators
Several
indicators can be used to analyze the economic viability of a project. The
indicators used in this study were: payback time, net present value (NPV), and
internal rate of return (IRR).
2.2.2.1.
Payback
time
Payback
time is considered a primary economic indicator, because it does not consider
the time value of money. However, it is still an indicator widely used by
companies. It refers to the time required for the investment to be returned,
according to equation (ASHRAE, 2007):
(7)
2.2.2.2.
Net
Present Value (VPL)
NPV
is considered a rigorous criterion of project evaluation. It corresponds to the
algebraic sum of cash flow values updated at the discount rate over time,
subtracted from the investment (BRUNI; FAMÁ, 2004). Discount rate is a
reference interest rate that represents the minimum amount that the investor
agrees to earn when making an investment. Thus, a project will be economically
feasible if it presents a positive NPV (BARROS et al. 2015). Considering that
all investments are made at the beginning of the project, the NPV calculation
is done using the equation:
(8)
Where:
NPV – net presente value;
CF – cash flow;
n – total number of years;
t – analyzed year;
I – investment.
2.2.2.3.
Internal
Rate of Return (IRR)
The
IRR of a project can be defined as the interest rate that makes the NPV equal
to zero. A project is economically viable and should be implemented when its
IRR is greater than the discount rate defined by the investor (BARROS et al.
2015; CEB; FUPAI/ EFFICENTIA, 2005a). The calculation of the IRR can be done
using the equation:
(9)
Where:
IRR – internal rate of return;
CF – cash flow;
n – total number of years;
t – analyzed year;
I – investment.
3. RESULTS AND DISCUSSION
The
steam system of the Efficient Industry
has the following steps: generation, distribution, and end use. The steam is
generated in aquotubular boilers, which produce 11.5 kg of steam for each m3
of natural gas. It exits the boilers at 380°C temperature and 42bar pressure.
Then
it passes through reduction valves, which transform it into superheated steam
with a pressure of 19bar and 290°C temperature, as well as saturated steam of
2.5bar pressure. Under these conditions, the steam is distributed to several
areas for final use, without condensate return.
The
steam distribution system mainly employs rock wool as thermal insulation; the
types of steam traps used are mainly: mechanical and thermodynamic. Table 1
shows the main pipelines and its length in each operating system.
Table
1: Main steam system pipelines, according to their
operating pressure.
Steam
pressure (bar) |
Pipeline
diameter (in) |
Pipeline
length (m) |
2,5 |
10 |
260 |
12 |
372 |
|
14 |
190 |
|
19 |
8 |
310 |
42 |
8 |
60 |
10 |
20 |
3.1.
Energy
Loss Estimate in the Steam Distribution System
In
the industrial sector, steam systems parameters can be considered constants
throughout the year (KRUCZEK, 2013). Therefore, from data collected in the Efficient
Industry, it was possible to estimate the energy losses through thermal
insulation and steam traps.
3.1.1. Energy
Loss Estimate through Steam Traps
The
analysis performed by Techsol (2016) concluded that seven steam traps were
leaking, out of 42 steam traps in the Efficient Industry. In steam systems
where maintenance has not been carried out for 3 or 5 years, between 15% and
30% of steam traps may present defects, such as live steam exhaust (CEB; FUPAI/
EFFICENTIA, 2005a).
Given
this context, steam traps state is reasonable, since 17% of them had steam
leak. The average flow rate of steam leaks considered was 33 tons of steam per
trap per month (SPIRAX SARCO, 2006). Therefore, the estimated total steam loss
from the traps was approximately 3 thousand tons of steam per year.
3.1.2. Energy
Loss Estimate through Thermal Insulation
3.1.2.1.
Saturated
Steam Loss Estimate through Thermal Insulation
Equations
(1) and (2) were used to estimate the annual steam loss from heat emission
through thermal insulation. The saturated steam system operates at a
temperature of 139°C and a pressure of 2.5bar, with a steam quality estimated
at 70%. The thermal insulation data were collected from commercial catalog:
thermal conductivity (0.155 kJ/m.h.°C), internal surface temperature (28ºC) and
thickness (50mm) (ISOVER, 2010). The annual amount of steam lost in the
saturated steam system was about 2,800 tons.
3.1.2.2.
Superheated
Steam Loss Estimate through Thermal Insulation
Superheated steam loss through thermal insulation was
estimated using equations (3) and (4). Therefore, the emitted heat rate was 592
596kJ/h for the steam system that operates at 19bar pressure, 290ºC
temperature, and have a mass flow rate of approximately 18000kg/h. Considering
that 3 048 kJ of energy is required for the production of a kilo of steam from
water initial conditions, steam loss is about 1.7 thousand tons per year.
As
for the steam system operating at 42 bar pressure, 380°C temperature, and have
an approximate mass flow rate of 52200kg/h, heat loss rate resulted in 459 360
kJ/h. Considering the same previous premise for the production of steam, the
steam loss resulted in approximately 1.3 thousand tons per year.
Thus,
the degradation of thermal insulation and defective steam traps generated an
annual steam loss of approximately 8,600 tons.
3.2.
Investment
Estimate
In
order to remedy steam loss through steam traps leakage, new devices must be
acquired to replace the defective ones. According to TECHSOL (2016), the total
investment in the acquisition of steam traps should be R$ 22 thousand
approximately.
Thermal
insulation reduces heat emission to the environment, nevertheless, the greater
the thickness, the higher the installation cost. Hence, in most cases,
thicknesses consecrated by use are recommended (CEB; FUPAI/ EFFICENTIA, 2005a).
Therefore, a supplier of glass wool tubes was consulted, and the investment
value for the acquisition of new thermal insulation was estimated in R$ 107
thousand.
Smooth
aluminum can be used for the mechanical protection of thermal insulation. Based
on commercial values, this item was estimated at approximately 33 thousand
reais.
The
steam pipeline is located at an average height of 10 meters. In order to carry
out disassembly and assembly of thermal insulation, adequate infrastructure is
necessary. Despite the existence of a couple of technologies, scaffolding was
chosen in order to consider the most conservative scenario. Thus, from
scaffolding cost estimate provided by the Efficient
Industry, this investment resulted in about 1.4 million reais.
The
investment in labor, in turn, was calculated considering reference values given
by the Efficient Industry, reaching
approximately R$ 484 thousand, for disassembly/ assembly of thermal insulation,
and installation of aluminum protection.
Therefore,
the total investment required for the implementation of the energy efficiency
project, considering the acquisition of steam traps, thermal insulation,
mechanical protection, scaffolding and work force is approximately R$ 2
million.
3.3.
Economic
Evaluation of the Project
The
economic evaluation of the project was carried out from cash flow elaboration,
and calculation and analysis of economic indicators.
3.3.1. Cash
Flow
The
energy efficiency project shall be implemented in a real steam distribution
system in the Efficient Industry.
After the project implementation, a proportional decrease of variable expenses
is estimated because the system becomes more efficient, decreasing the need of
steam production. The depreciation rate for steel distribution facilities is
10% per year, thus, project lifetime is 10 years (BRAZIL, 2017).
However,
technical-economic condition will not remain stable over time, making it
necessary to vary some factors, such as production costs and steam economy
after project implementation. In order to simulate the variation of steam
production costs due to inflation, the General Price Index - Internal
Availability (IGP-DI) of the last five years was adopted: 7% (FGV, 2017).
Progressive loss of steam economy after project implementation was considered,
due to the degradation of thermal insulation and steam traps over the lifetime
of 10 years. From these considerations and equations (5) and (6), cash flow was
constructed, as shown in table 2.
Table
2: Cash flow of the energy efficiency project.
Year |
Cash flow (R$) |
0 |
(2 071 868,94) |
1 |
1 344 755,71 |
2 |
1 410 110,83 |
3 |
1 447 234,16 |
4 |
1 449 697,54 |
5 |
1 410 160,33 |
6 |
1 320 262,61 |
7 |
1 170 507,11 |
8 |
950 128,87 |
9 |
646 951,39 |
10 |
247 227,85 |
3.3.2. Economic
Viability Indicators
Feasibility
indicators of the project was calculated using equations (7) to (9), from the
cash flow data. The results are presented and interpreted below.
Based
on the steam loss estimate and investment, payback time resulted in 1.8 year.
According to the criteria of the Efficient Industry, the energy
efficiency project is considered economically feasible, because this indicator
is less than 2 years.
The
discount rate adopted by the Efficient Industry
for economic evaluation of projects is 12% per year. From this parameter, it
was possible to calculate NPV and IRR. The NPV had a positive value of about R$
5 million. The calculated IRR resulted 66% per year, more than 5 times the
discount rate considered.
All
indicators pointed to the economic feasibility of the project. In addition, NPV
and IRR quantified the economic benefit that the company would obtain after 10
years of implementation of the energy efficiency project.
3.4.
Environmental
Evaluation of the Project
Environmental
evaluation of a project is extremely important, since it can result in an
improvement of the company's environmental indicators. The environmental
assessment of the energy efficiency project was carried out by analyzing the changes
in use of main raw materials in steam production.
Natural
gas is one of the main raw materials for steam production in the Efficient Industry. For every ton of
steam produced, 87m3 of this fuel is consumed. The use of natural
gas, however, generates greenhouse gases that contribute to the increase in
global warming. Thus, through the implementation of this project, it would be
possible to avoid the use of about 5x106 m3 of natural
gas.
This
represents a reduction in emission of about 11,600 tons of equivalent carbon
dioxide, contributing to mitigate global warming and climate change.
Furthermore, this carbon emissions reduction can generate tradable carbon
credits, which can be incorporated into the cash flow. However, this factor was
not considered in the economic evaluation of the project, since it was not
estimated the cost that this process would generate for the Efficient Industry.
Water
is an indispensable resource in steam production. Moreover, in the Efficient Industry, all generated steam
is consumed or discarded throughout the production process. Then, once the
energy efficiency project is implemented, it will be able to reduce steam
production around 57 thousand tons. In addition, the Efficient Industry considers 5% water waste in boilers, which would
represent 3 thousand tons of water.
The
production of demineralized water for steam production, in turn, uses water in
the regeneration of some operational units, in the order of 0.24m3/m3
of demineralized water produced. This would represent the consumption of 15
thousand tons of water. Thus, considering all the uses and consumptions of
water in the steam system, 75 thousand tons of water is saved during the 10
years of the project, contributing to increase local availability of water, and
consequently, decreasing water stress in the region.
Hence,
we highlight some improvement in environmental indicators, which could enhance
the corporate image of the Efficient
Industry. Besides, the environmental agency could recognize the benefits of
the project implementation during the renewal process of operational license.
4. CONCLUSIONS
This
paper proposes to analyze the economic viability of an energy efficiency
project for a steam distribution system in a chemical industry, from energy
loss estimates through thermal insulation and steam traps. The objective was
achieved, because:
–
Energy losses of the steam distribution system were
estimated at approximately 8.6 thousand tons of steam in the first year,
totaling 57.4 thousand tons at the end of the 10-year project;
–
The investment was estimated at approximately R$ 2
million, considering new materials and equipment, labor and scaffolding;
–
The cash flow of the project was built, and the
economic indicators were calculated and analyzed: payback time, NPV and IRR.
All indicated that the project is economically feasible;
–
In addition, the project had environmental benefits:
lower consumption of energy and water, about 5x106 m3 of
natural gas and 75,000 tons, respectively, and a reduction in greenhouse gases
generation of around 11,600 tons of equivalent carbon dioxide.
Therefore,
the energy efficiency project is attractive economically, besides presenting
socio-environmental viability. Moreover, this economic attractiveness can be
improved if the following limitations are considered in future works:
–
Energy loss in the distribution system could be
higher, since the heat emission rate considered through thermal insulation was
conservative compared to the studies conducted by Tsygankova and Dmitrienko
(2014), and Kruczek (2013). Thus, on-site measurements of the operating
conditions of thermal insulation should be made;
–
Although thermal insulation degradation is not uniform
throughout the steam distribution system, it was considered so. This prevented
progressive projects of thermal insulation renewal, limiting the economic
benefits of their implementation.
–
The investment was probably overestimated, since among
available technologies of infrastructure for disassembling / assembling thermal
insulation, the most expensive one was chosen: scaffolding.
–
The depreciation rate adopted for steam traps and
thermal insulation has probably been underestimated. According to commercial
representatives, their lifetime is at least 10 years, and around 50 years,
respectively.
–
Costs estimate related to registration and sale of
carbon credits generated from the implementation of energy efficiency projects
was not considered in the economic evaluation of the project.
REFERENCES
ACEEE – AMERICAN COUCIL FOR AN ENERGY-EFFICIENT ECONOMY (2016). The 2016 International Energy Efficiency
Scorecard. Washington DC: ACEEE. Available:
http://aceee.org/research-report/e1602. Access: 3rd April, 2017.
ASHRAE - AMERICAN SOCIETY OF HEATING, REFRIGERATING AND AIR-CONDITIONING
ENGINEERS (2007). Handbook 2007: HVAC
Applications. Atlanta: ASHRAE.
ASSAF NETO, A. (1992) Quantitative methods for investment analysis. Caderno de Estudos, São Paulo, n. 6, p. 01-16.
Available: http://dx.doi.org/10.1590/S1413-92511992000300001. Access:
20th March, 2017. [Portuguese]
BARROS, M. C. C.; MARQUES, J. A.; SILVA, R. R.; SILVA, F. F.; COSTA, L.
T.; GUIMARÃES, G. S. (2015) Economic feasibility of crude glycerin use for
finished lambs in confinement. Semina: Ciências
Agrárias, Londrina, v. 36, n. 1, p. 443-452. Available:
http://dx.doi.org/10.5433/1679-0359.2015v36n1p443. Access: 20th
March, 2017. [Portuguese]
BRAZIL (1997) Ministry of the Environment, Water Resources, and Legal
Amazon. Law n.9.433: National Water
Resources Policy. Brasília: Department of Water Resources. Available:
http://www.planalto.gov.br/ccivil_03/leis/L9433.htm. Access: 18th March, 2017.
[Portuguese]
BRAZIL (2005) Foundation for the Technological Development of
Engineering. Useful Energy Balance – BEU
2005. [Portuguese].
BRAZIL (2010) Ministry of Science and Technology. Greenhouse gases emissions in industrial processes: Chemical Industry/
Brazilian Chemical Industry Association (ABIQUIM). Reference report of the
Second Brazilian Inventory of Anthropogenic Greenhouse Gas Emissions and
Removals. Brasília: MCT. Available:
http://www.mct.gov.br/upd_blob/0228/228961.pdf. Access: 20th March, 2017.
[Portuguese]
BRAZIL (2016) Energy Research Company (EPE). National Energy Balance, 2016 – Base year 2015. Rio de Janeiro:
EPE. Available: https://ben.epe.gov.br/. Access: 20th March, 2017 [Portuguese].
BRAZIL
(2017) Normative Instruction RFB nº1700,
de 14 de março de 2017. Diário Oficial da República Federativa do Brasil,
Brasília, DF, 16 mar. 2017. Seção 1, p. 23. Available:
http://normas.receita.fazenda.gov.br/sijut2consulta/link.action?visao=anotado&idAto=81268#1706802.
Access: 20th March, 2017. [Portuguese]
BRUNI, A. L.; FAMÁ, R. (2004) Financial
Mathematics: with HP 12C and Excel. 3 ed. São Paulo: Atlas. [Portuguese]
CEB; FUPAI/ EFFICENTIA – BRAZILIAN ELECTRICAL CENTERS (2005a) Energy efficiency in the use of steam. Rio de Janeiro:
Eletrobrás. [Portuguese]
CEB;
FUPAI/ EFFICENTIA – BRAZILIAN ELECTRICAL CENTERS (2005b). Energy efficiency in steam use: practical manual. Rio de Janeiro:
Eletrobrás. [Portuguese]
CENGEL,
Y.A. (2003) Heat transfer: a practical
approach. Nova Iorque: McGraw-Hill Inc.
CHEN, C.L.; LIN, C.Y. (2011) Design and optimization of steam distribution
systems for steam power plants. Industrial
& Engineering Chemistry Research, v.50, p.8097-8109. Available:
http://dx.doi.org/10.1021/ie102059n. Access: 18th March, 2017.
ÇOMAKLI, K.; YUKSEL, B.; ÇOMAKLI, O. (2003) Thermophysical Evaluation of
energy and exergy losses in district heating network. Applied Thermal Engineering, v.24, p.1009-1017. Available:
http://dx.doi.org/10.1016/j.applthermaleng.2003.11.014. Access: 18th March,
2017.
DALLA ROSA, A.; LI, H.; SVENDSEN, S. (2011) Method for optimal design of
pipes for low-energy district heating, with focus on heat losses. Energy, v.36, p.2407-2418. Available:
http://dx.doi.org/10.1016/j.energy.2011.01.024. Access: 18th
March, 2017.
FGV – GETÚLIO VARGAS FOUNDATION (2017).
IBRE – BRAZILIAN INSTITUTE OF ECONOMICS. IGP-DI Report. Available: http://portalibre.fgv.br/. Access: 16th
February, 2017. [Portuguese].
ISOVER – SAINT GOBAIN (2010) Thermal
insulation with Super Tel split pipes - Ruler nº01. [Portuguese].
KAYFECI, M. (2014) Determination of energy saving and optimum insulation
thickness of the heating piping systems for different insulation materials. Energy and Buildings, v.69, p.278-284,
2014. Available: http://dx.doi.org/10.1016/j.enbuild.2013.11.017. Access: 18th
March, 2017.
KUZNETSOV, G.V.; POLOVNIKOV, V.Y. (2011) The conjugate problem of
convective-conductive heat transfer for heat pipelines. Journal of Engineering Thermophysics, v.20, n.2, p.217-224.
Available: http://dx.doi.org/10.1134/S181023281102010X. Access: 18th March,
2017.
KRUCZEK, T. (2013) Determination of annual heat losses from heat and
steam pipeline networks and economic analysis of their thermomodernisation. Energy, v.62, p.120-131. Available: http://dx.doi.org/10.1016/j.energy.2013.08.019.
Access: 18th March, 2017.
IPCC - INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE (2014) Climate Change 2014: Synthesis Report. Contribution
of Working Groups I, II and III to the Fifth Assessment Report of the
Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and
L.A. Meyer (eds.)]. Genebra: IPCC. Available:
https://www.ipcc.ch/report/ar5/syr/. Access: 20th March, 2017.
LI, H.; SVENDSEN, S. (2012) Energy and exergy analysis of low
temperature district heating network. Energy, v.45, p.237-246. Available:
http://dx.doi.org/10.1016/j.energy.2012.03.056. Access: 18th
March, 2017.
OZTURK, I.T.; KARABAY, H.; BILGEN, E. (2006) Thermo-economic
optimization of hot water piping systems: a comparison study. Energy, v.31, p.2094-2107. Available:
http://dx.doi.org/10.1016/j.energy.2005.10.008. Access: 18th
March, 2017.
POLOVNIKOV, V.Y.; GUBANOV, Y.Y. (2015) Numerical analysis of a heat loss
of channel-free heat pipeline in the real application conditions. EPJ Web of Conferences, v.82.
Available: https://doi.org/10.1051/epjconf/20158201008. Access: 18th March,
2017.
POLOVNIKOV, V.Y.; GUBINA, E.V. (2014) Heat loss of heat pipelines in
moisture conditions of thermal insulation. EPJ
Web of Conferences, v.76. Available: https://doi.org/10.1051/epjconf/20147601029.
Access: 18th March, 2017.
SANAEI, S.M.; NAKATA, T. (2012) Optimum design of district heating:
application of a novel methodology for improved design of community scale
integrated energy systems. Energy, v.38,
p.190-204. Available: http://dx.doi.org/10.1016/j.energy.2011.12.016. Access:
18th March, 2017.
SEEG/OC – SYSTEM STUDY GREENHOUSE GAS EMISSIONS ESTIMATES/ CLIMATE
OBSERVATORY (2016). General Emissions
Table. Available: http://seeg.eco.br/tabela-geral-de-emissoes. Access: 7th
January, 2016. [Portuguese]
SPIRAX SARCO (2006) Steam system
evaluation of the Efficient Industry. [Portuguese].
TECHSOL (2016) Steam traps
evaluation of the Efficient Industry. [Portuguese].
TSYGANKOVA, Y.S.; DMITRIENKO, M.A. (2014) Comprehensive definition of
thermal losses taking into account to the conditions of thermal networks. MATEC Web of Conferences, v.19.
Available: http://dx.doi.org/10.1051/matecconf/20141901022. Access: 18th March,
2017.
UNFCCC - UNITED NATIONS FRAMEWORK CONVENTION ON CLIMATE CHANGE (2015). The Paris Agreement. Available:
http://unfccc.int/paris_agreement/items/9485.php. Access: 1st May, 2017.
WYNN, G. (2015) Decoding the Paris climate deal: What does it mean? Climate Home. Politics, COP21.
Available: http://www.climatechangenews.com/2015/12/12/decoding-the-paris-climate-deal-what-does-it-mean.
Access: 17th March, 2017.