Low Carbon Economy, 2010, 1, 1-7
doi:10.4236/lce.2010.11001 Published Online September 2010 (http://www.SciRP.org/journal/lce)
Carbon Emissions Reduction and Power Losses
Saving besides Voltage Profiles Improvement
Using Micro Grids
Rashad M. Kamel, Aymen Chaouachi, Ken Nagasaka
Environmental Energy Engineering, Department of Electronics & Information Engineering, Tokyo University of Agriculture and
Technology, Tokyo, Japan.
Received July 21st, 2010; revised August 27th, 2010; accepted August 27th, 2010.
ABSTRACT
The objective of this paper is to evaluate the value of enhancement in voltage, amount of emission reduction and
amount of power losses saving with using micro grids. The paper is divided in two parts, the first part evaluates the
voltage improvement and power losses saving with micro (μ) sources (distributed generators like fuel cell, micro tur-
bine, solar cell, wind turbine etc.). The obtained results indicate that using μ sources reduce voltage drop by about 3%,
Also, it is found that using μ sources can reduce the power losses to more than one third of its value without using μ
sources. The voltage at the buses near the μ sources location will suffer from small drop than the buses far from μ
sources locations. The second part calculates amount of CO2, SO2, NOx and particulate matters emissions from main
grid and from μ sources which forms micro grid. The results indicates that more penetration of μ sources in the power
systems especially the renewable sources (solar and wind) will help in reducing or removing emission problems and
solve the green house gas problems. Finally this paper proved with calculations that the micro grid can solve most of
the problems which facing the conventional power system and keep the surrounding environment clean from pollution
and the micro grid will be the future power system.
Keywords: Micro Grid, Voltage Enhancement, Losses Saving, CO2, SO2, NOx and Particulate Matter Emissions
1. Introduction
Increasing penetration of distributed generation (DG)
resources to the low voltage (LV) grids, such as Photo-
voltics, CHP micro-turbines, small wind turbines areas
and possibly fuel cells, alters the traditional operating
principle of the grids. A particularly promising aspect,
related to the proliferation of small-scale decentralized
generations (μ sources), is the possibility for parts of the
network comprising sufficient generating resources to
operate in isolation from the main grid, in a deliberate
and controlled way. These are called micro grids and the
study and development of technology to permit their ef-
ficient operation has started with a great momentum
[1-3].
With the efficient integration of small scale distributed
generation into LV system and ability of supplying its own
local demand customers, exporting energy to neighbor’s
systems and providing ancillary services (flow manage-
ment, voltage and frequency control capabilities) to the
public systems, the development of micro grids has po-
tential to bring a number of benefits into the system in
term of [4]:
 Enabling development of sustainable and green elec-
tricity: Clearly, electricity generated by renewable energy
sources can substitute electricity supplied by conven-
tional power plants with many benefits such as carbon
emission reduction, reducing dependency on depleting
fossil sources and sustainable and “free” energy sources
which in the long term brings lower energy prices.
 Enabling larger public participation in the invest-
ment of small scale generation: Economic appraisal for
installing micro generation will likely require less com-
plex analysis in contrast to large generation. With much
smaller magnitude in the investment, and less complexity
in trading electricity, the financial risks exposed to the
investors are much lower. At a domestic level, the deci-
sion to invest in such generation may be less motivated
by financial gain and influenced by Individual’s will to

2 Carbon Emissions Reduction and Power Losses Saving besides Voltage Profiles Improvement Using Micro Grids
contribute for clean environment. This will clearly enable
larger public participation in contributing to the deploy-
ment of Renewable Energy Sources (RES) in the form of
micro generation.
 Reduction in marginal central power plants: Micro
generation can displace the capacity of peak load or mar-
ginal central power plants.
 Improved security of supply: With a considerable
large number of installed micro generation, the total gen-
eration margin increases. This will also directly increase
the available capacity of supplying peak load condition.
 With a large number of generators, failure in a
number of small generators will not have a considerable
impact on the capability of supplying the demand. This is
in contrast to systems which rely on a relatively small
number of big generators. A failure of one large genera-
tor may cause significant generation deficit and may lead
to load shedding. Micro generation technologies also
bring more diversity in the types of fuel that can be used
to generate electricity. This is likely to increase the secu-
rity of supply and reduce dependency on a particular type
of fuel [5,6].
 Reduction of losses: Currently, losses in a system
which primarily relies on central generation are typically
around 7%-10% of total electricity consumption per year
[4]. The magnitude of losses is influenced by many factors
such as the proximity of generation to loads, circuit im-
pedances, loads, and profiles of loading in each circuit
among others. Bearing in mind that losses are a quadratic
function of the current, the largest losses occur during
peak loading conditions of the circuit. As micro grid is
able to supply its loads locally, it reduces the amount of
power transfer from remote generation via transmission
and distribution circuits. Hence, it will reduce system
losses. This also leads to the reduction of total energy
produced by central power plants. Thus, it will also re-
duce Pollutants (CO2, NOx, SO2 and other particulate
matter) from these plants.
 Enabling better network congestion management
and control for improving power quality: The introduc-
tion of micro generation in the LV networks will provide
better capability of controlling power flows from the LV
systems to the upper voltage networks. Hence, it may
avoid the need for reinforcing the networks due to net-
work congestion or voltage problems.
Based on the previous discussion, using micro grid
will help on voltage improvement, emission reduction
and power losses saving. Many papers discussed the ef-
fect of micro grid on voltage improvement, power losses
reduction and emission reduction, but quantifying
amount of improvement or reduction is not considered.
The main goal of this paper is to evaluate the effect of
the micro grid on voltage enhancement, emission reduc-
tion and losses saving. To conduct the proposed studies,
the benchmark networks used for analysis and its data are
described in Section 2 [single feeder and multi feeder
networks]. Section 3 presents the daily load curves of the
one feeder network (residential load) and three feeders
network with three types of loads (residential, industrial
and commercial loads). Section 4 shows the effect of the
micro grid on voltage improvement and power losses
saving for single feeder and multi feeders networks.
Amount of emission reduction due to using micro grid is
given in Section 5. Conclusions are stated in Section 6.
2. Benchmark Network Used for Analysis
Bench mark network described in references [3] and [7] is
used for analysis. Single line diagram with all buses
marked is shown at the end of the paper (Figure 12). One
feeder network includes 7 buses (buses 1-7) represent the
residential loads. Industrial load (bus 8) represents the
second feeder. The remaining buses (buses 9-16) feed
commercial loads and represent the third feeder. Imped-
ance of the network lines, data for μ sources used and
renewable power time-series used [output KW/Installed
KW] are given in Tables 1-3 respectively [7].
The units have been calculated in power base of 100
KVA and voltage base 400V. Bus 0 represents the main
grid (distribution network).
Micro turbine is located at bus 7, fuel cell is located at
bus 6, and PV3 is located at bus 5 while wind turbine and
PV2-5 are connected to bus 4.
3. Daily Load Curves for Single and
Multiple Feeders Networks
Aggregate daily load curves for single feeder (residential
loads) and three feeders (residential, industrial and com-
Table 1. Line data for micro grid.
Sending BusReceiving
Bus R (p.u.) X (p.u.)
0
1
2
3
4
5
3
1
1
9
10
11
9
13
10
15
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
0.0025
0.0001
0.0125
0.0125
0.0125
0.0125
0.021875
0.033125
0.0075
0.015
0.02125
0.02125
0.010625
0.010625
0.023125
0.023125
0.01
0.0001
0.00375
0.00375
0.00375
0.00375
0.004375
0.00875
0.005
0.010625
0.005625
0.005625
0.005625
0.005625
0.00625
0.00625

Carbon Emissions Reduction and Power Losses Saving besides Voltage Profiles Improvement Using Micro Grids3
Table 2. Data of the used μ sources.
Unit ID Unit Name
Minimum
capacity
(KW)
Maximum
capacity
(KW)
1
2
3
4
5
6
7
8
Micro tur-
bine
Fuel cell
Wind
PV1
PV2
PV3
PV4
PV5
2
1
0.1
0.05
0.05
0.05
0.05
0.05
30
30
15
3
2.5
2.5
2.5
2.5
Table 3. Renewable power time-series (Output KW/Installed
KW).
Hour Wind
Power
PV-time
series Hour Wind Power
PV-time
series
1
2
3
4
5
6
7
8
9
10
11
12
0.364
0.267
0.267
0.234
0.312
0.329
0.476
0.477
0.424
0.381
0.459
0.39
0
0
0
0
0
0
0.002
0.008
0.035
0.1
0.23
0.233
13
14
15
16
17
18
19
20
21
22
23
24
0.494
0.355
0.433
0.321
0.329
0.303
0.364
0.373
0.26
0.338
0.312
0.346
0.318
0.433
0.37
0.403
0.33
0.238
0.133
0.043
0.003
0
0
0
mercial loads) are shown in Figure 1.
4. Voltage Enhancement and Power Losses
Saving Evaluation with Using Micro Grid
Load flow program [8] is used to calculate the voltages at
all nodes of the micro grid. Results are shown in Figures
2-7. The power factor is 0.85 lagging for residential and
commercial consumers and 0.9 for the industrial ones.
All calculations have been made at p.u of base Vbase =
400 V and Sbase = 100 KVA. The network data are pre-
sented in Sections 2 and 3. It has also been assumed that
in the μ sources the power electronic interface has been
adjusted to give or absorb zero reactive power at all
buses except fuel cell and micro turbine buses. At all
time, we assume that the micro turbine and fuel cell op-
erated at 84% of their maximum capacity (25 KW), and
the renewable sources outputs powers as listed in Table
3. The dashed lines represent results without μ sources
while the solid lines represent results with using μ
sources.
From the above results the following points can be
raised:
 With using μ sources, in the two studied cases (sin-
gle feeder and three feeder), the voltages at all buses are
improved.
 Amount of improvement in case of single feeder
network is better than three feeder case because amount
2 4 6 810 12 14 1618 20 22 24
0
20
40
60
80
100
120
140
160
180
200
Hou
r
Power( KW )
One feeder
Three feeder
Figure 1. Daily load curves for one feeder and three feeders
networks.
510 1520
0. 96
0. 98
1
1. 02
Hour
Voltage ( pu )
Main grid
510 15 20
0. 96
0. 98
1
1. 02
Hour
Voltage( pu )
Bus# 1
510 1520
0. 96
0. 98
1
1. 02
Hour
Voltage( pu )
Bus# 2
510 15 20
0. 96
0. 98
1
1. 02
Hour
Voltage( pu )
Bus# 3
Figure 2. Voltage at buses 1, 2, 3 and main grid for single
feeder network with and without using μ sources.
510 15 20
0.96
0.98
1
1.02
Hour
Voltage( pu )
Bus# 4
510 15 20
0. 96
0. 98
1
1. 02
Hour
Voltage( pu )
Bus# 5
510 15 20
0.96
0.98
1
1.02
Hour
Voltage( pu )
Bus# 6
510 15 20
0. 96
0. 98
1
1. 02
Hour
Voltage( pu )
Bus# 7
Figure 3. Voltage of buses 4, 5, 6 and 7 for single feeder
network with and without using μ sources.

4 Carbon Emissions Reduction and Power Losses Saving besides Voltage Profiles Improvement Using Micro Grids
510 1520
0. 96
0. 98
1
Hour
Voltage ( pu )
Bus# 1
510 15 20
0. 96
0. 98
1
Hour
Voltage( pu )
Bus# 2
510 1520
0. 96
0. 98
1
Hour
Voltage( pu )
Bus# 3
510 15 20
0. 96
0. 98
1
Hour
Voltage( pu )
Bus# 4
Figure 4. Voltage of buses 1, 2, 3 and 4 for three feeder
network with and without using μ sources.
510 15 20
0.96
0.98
1
1.02
Hour
Voltage( pu )
Bus# 5
510 15 20
0.96
0.98
1
1.02
Hour
Voltage( pu )
Bus# 6
510 15 20
0.96
0.98
1
1.02
Hour
Voltage( pu )
Bus# 7
510 15 20
0.96
0.98
1
1.02
Hour
Voltage( pu )
Bus# 8
Figure 5. Voltage at buses 5, 6, 7 and 8 for three feeder
network with and without using μ sources.
5101520
0. 96
0. 98
1
1. 02
Hour
Voltage( pu )
Bus# 9
510 15 20
0. 96
0. 98
1
1. 02
Hour
Voltage( pu )
Bus# 10
5101520
0. 96
0. 98
1
1. 02
Hour
Voltage( pu )
Bus# 11
510 15 20
0. 96
0. 98
1
1. 02
Hour
Voltage( pu )
Bus# 12
Figure 6. Voltage at buses 9, 10, 11 and 12 for three feeder
network with and without using μ sources.
510 1520
0. 96
0. 98
1
1. 02
Hour
Voltage( pu )
Bus# 13
510 1520
0. 96
0. 98
1
1. 02
Hour
Voltage( pu )
Bus# 14
510 1520
0. 96
0. 98
1
1. 02
Hour
Voltage( pu )
Bus# 15
510 1520
0. 96
0. 98
1
1. 02
Hour
Voltage( pu )
Bus# 16
Figure 7. Voltage of buses 13, 14, 15 and 16 for three feeder
network with and without using μ sources.
of power produced by the μ sources is less than the
power demand by loads of the three feeder, also the μ
sources are far from loads of industrial (bus 8) and com-
mercial (buses 9-16) feeders.
 The largest drop of the voltage is about 4.5% with-
out μ sources, because we assume that the voltage at the
main grid (distribution network) equal to 1 p.u., if we
assume that the voltage at the distribution network less
than 1 p.u (due to voltage drop in the transmission net-
work) as actually occur, the voltage drop without using μ
sources will be more than 4% and may be reach to 8%.
The total power losses for one feeder and three feeder
networks at the same conditions mentioned before are
evaluated and the results are shown in Figures 8 and 9.
From the above figures, the following points can be
summarized:
 The total power losses with using μ sources is less
than the losses when μ sources are not used, because us-
ing μ sources reduces the distance between the load and
generation and also, reduce the current flowing from the
main grid. In addition, in our analysis, we calculated the
losses in the transformer which connect the main grid
with the micro grid network. If we take the losses in the
upper distribution and transmission networks, the amount
of losses will exceed the calculated value.
 For single feeder network, at lightly load μ sources
production will feeds the load and export the remaining
power to the distribution grid which make the losses with
using μ sources larger than losses without μ sources.
5. Emission Reduction Evaluation with
Using μ Sources
In order to evaluate the potential of environmental bene-
fits from the micro grids, data about the emissions from

Carbon Emissions Reduction and Power Losses Saving besides Voltage Profiles Improvement Using Micro Grids5
05 10 15 20 25
0
0. 5
1
1. 5
2
2. 5
3
Hour
Power losses (KW)
with micro sources
without micro sources
Figure 8. Total losses for single feeder network with and
without μ sources.
05 10 15 20 25
0
1
2
3
4
5
6
Hou
r
Power losses ( KW )
with micro sources
without micro sources
Figure 9. Total losses for three feeders network with and
without μ sources.
the main grid and data about the emissions of the μ sources
should be taken into account. The emissions for which
calculations are made are: CO2, SO2, NOx and particulate
matters.
5.1. Emissions of the Main Grid
The production of the μ sources displaces power from the
main grid. Thus the emissions avoided are an average
value of the main grid emissions multiplied by the pro-
duction of the μ sources. In our study, typical values of
emissions have been used as shown in Table 4 [7].
Table 4. Typical values of emissions from the main grid.
Pollutants gr/KWh
CO2
SO2
NOx
Particulate Matters
889
1.8
1.6
0.501
5.2. Impact of μ Sources
From the installed μ sources the ones that consume fuels
have emissions which are significantly lower than the
ones in the main grid. Where as the renewable such as
wind and solar energies have zero emissions in their op-
eration. It is assumed that the fuel burned by the Micro
turbine and the fuel cells is natural gas. Table 5 gives the
data used for our analysis [7].
5.3. Results and Discussions
Amounts of emissions with and without using μ sources
for single feeder and three feeder networks are shown in
Figures 10 and 11.
According to the results obtained in the previous fig-
ures the following point can be summarized:
 Using μ sources has large effect in reducing the
amount of emissions on CO2, SO2, NOx and particulate
matters, but the reduction in SO2, NOx and particulate
matters is greater in percentage than CO2 reduction due
to the fact that the fuel burning units use natural gas that
has lower emission levels in particulate matters, NOx and
SO2 compared to thermal stations that use Heavy Oil.
Table 5. Typical emission data for μ sources.
Unit nameCO2 coeff.
(gr/KWh)
NOX coeff.
(gr/KWh)
SO2 coeff.
(gr/KWh)
Parti.
Matters
(gr/KWh)
Micro
Turbine
Fuel Cell
Wind1
PV1
PV2
PV3
PV4
PV5
724.6
489
0
0
0
0
0
0
0.2
0.01
0
0
0
0
0
0
0.004
0.003
0
0
0
0
0
0
0.041
0.001
0
0
0
0
0
0
010 20 30
20
40
60
80
100
Hour
CO2 emissions( Kg )
010 20 30
0
50
100
150
200
Hour
SO2 emissions ( gr )
010 20 30
0
50
100
150
Hour
NOX emissions ( gr )
010 20 30
0
20
40
60
Hour Particulate Matters emissions ( gr )
SO2 emissions (gr)
CO2 emissions (Kg)
N
OX emissions (gr)
Figure 10. Amount of CO2, SO2, NOx and particulate mat-
ters emissions for one feeder network with and without μ
sources.

6 Carbon Emissions Reduction and Power Losses Saving besides Voltage Profiles Improvement Using Micro Grids
010 20 30
0
50
100
150
200
Hour
CO2 emission( Kg )
010 20 30
0
100
200
300
400
Hour
SO2 emission ( gr ) SO2 emissions
(g
r
)
010 20 30
0
100
200
300
400
Hour
NOX emission ( gr )
010 20 30
0
50
100
Hour
Particulate matters emission ( gr )
Figure 11. Amount of CO2, SO2, NOx and particulate mat-
ters emissions for three feeder network with and without μ
sources.
 In our study, the amount of power produced by re-
newable energy is small (15% of the μ sources power), if
the renewable sources increases, amount of emissions
reduction will be more than the value shown in the pre-
vious figures.
CO2 emissions
(
K
g)
6. Conclusions
Distributed generation (DG) operation can improve the
voltage profile in the micro grid nodes especially at the
feeder where μ sources are installed. Therefore the in-
stallation of DG sources seems to be a solution in im-
proving the voltage profile within a micro grid during
times of low voltages (peak loads). It is found that when
the power produced by μ sources sufficient to loads, the
voltage drop at all buses has a negligible values, also,
using micro grid will decrease the amount of power
losses because the power which produced by μ sources
will consumed locally with the load near from the μ
N
OX emissions (gr)
Figure 12. Single line diagram for three feeder network.

Current Distortion Evaluation in Traction 4Q Constant Switching Frequency Converters 7
sources which prevent current from flowing or circulat-
ing in the networks transmission lines. Results showed
that using μ sources has more effects in reducing all
types of emissions especially when the μ sources contains
many renewable sources such as wind and solar energy
sources. The authors next step research aims to study the
effects of micro grid in the dynamic performance of the
main grid and how to use the μ sources to solve some of
power system dynamic problems such as voltage stability,
power quality and power system reliability.
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