research paper performance

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Performance analysis of hybrid photovoltaic/diesel energy system under

Malaysian conditions

K.Y. Lau, M.F.M. Yousof, S.N.M. Arshad, M. Anwari*, A.H.M. Yatim

Faculty of Electrical Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia

a r t i c l e i n f o

Article history:

Received 29 October 2009

Received in revised form

5 April 2010

Accepted 7 April 2010

Available online 15 May 2010

Keywords:

Hybrid PV/diesel system

Standalone diesel system

Performance analysis

HOMER software

a b s t r a c t

Standalone diesel generating system utilized in remote areas has long been practiced in Malaysia. Due tohighly fluctuating diesel price, such a system is seemed to be uneconomical, especially in the long run if

the supply of electricity for rural areas solely depends on such diesel generating system. This paper

would analyze the potential use of hybrid photovoltaic (PV)/diesel energy system in remote locations.

National Renewable Energy Laboratorys (NREL) HOMER software was used to perform the techno-

economic feasibility of hybrid PV/diesel energy system. The investigation demonstrated the impact of PV

penetration and battery storage on energy production, cost of energy and number of operational hours of

diesel generators for the given hybrid configurations. Emphasis has also been placed on percentage fuel

savings and reduction in carbon emissions of different hybrid systems. At the end of this paper, suitability

of utilizing hybrid PV/diesel energy system over standalone diesel system would be discussed mainly

based on different solar irradiances and diesel prices.

2010 Elsevier Ltd. All rights reserved.

1. Introduction

In Malaysia, there are abundances of remote villages that are

located far away from utility grid. These areas normally lack in the

supply of electricity since it is impractical to extend the utility grid

to these dispersed populated areas that are usually located in

rugged terrains. As a result, such villages are normally powered by

standalone diesel generators to cope for the demand of electricity.

However, current increase in global fuel price has drawn serious

attention of using renewable energy sources in these remote

locations. Since these remote areas largely depend on diesel

consumption for electricity supply, increase in global fuel prices

will have great impact to these societies. Therefore, the use of

renewable energy in these locations would be of great benefit,

especially in reducing the dependence on such highly fluctuating

diesel price.Solar energy is one of the in-exhaustible energy sources avail-

able for the implementation of renewable energy system in remote

areas. It has been pursued by a number of countries with monthly

average daily solar radiation in the range of 3e6 kWh/m2 in an

effort to reduce their dependence on fossil fuels [1e4]. Malaysia,

being gifted with abundance of solar radiation, has a wide potential

of solar energy applications to meet the electricity demand of

remote villages. Therefore, integration of solar photovoltaic with

readily available standalone diesel generators (or generally known

as the hybrid PV/diesel system) has seen potential application in

such remote areas.

The use of hybrid PV/diesel system comes with various advan-

tages. Among them are improved reliability, reduced emissions and

pollutions, reduced cost and more efficient use of power. The

maintenance cost involved for PV system is negligibly small, and

can be assumed to be maintenance-free after its installation. Unlike

standalone diesel generator, it has to be maintained accordingly,

such as replacing diesel or components exhausted during operation

to ensure reliable supply of the generator. Apart from that, the use

of PV also allows it to be easily expanded to meet the growing

energy needs. However, since the use of PV is still new, its initial

cost, especially its installation cost is quite high. Another drawbackis that PV is sunshine-dependent and its output does not match the

load demand on 24-hour basis.

Luiz Carlos Guedes Valente et al. [5] performed an economic

analysis on hybrid PV/diesel system and demonstrated that the

system has advantages over standalone diesel system. With cost

analysis over a 20-year period, hybrid system was proven to reduce

fuel consumption, operation and maintenance costs while

improving the quality of service. This is exceptionally true for small

villages with up to 100 families.

The application of hybrid PV/diesel system has seen its

successful implementation in Malaysia with the Langkawi Cable* Corresponding author. Tel.: 60 75535235; fax: 60 75566272.

E-mail address: [email protected] (M. Anwari).

Contents lists available at ScienceDirect

Energy

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / e n e r g y

0360-5442/$ e see front matter 2010 Elsevier Ltd. All rights reserved.

doi:10.1016/j.energy.2010.04.008

Energy 35 (2010) 3245e3255
mailto:[email protected]://www.sciencedirect.com/science/journal/03605442http://www.elsevier.com/locate/energyhttp://www.elsevier.com/locate/energyhttp://www.sciencedirect.com/science/journal/03605442mailto:[email protected]


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Car Resort Facilities Project [6]. The hybrid system consists of

diesel generators with electronic control system, lead-acid battery

system, solar PV, inverter module and system controller with

remote monitoring capability. The project has been proven

successful in offering solution to off-grid power generation in

terms of reduced operation, maintenance and logistics problemand cost, providing 24-hours reliable supply at an effective cost as

well as preserving the nature. With such a good experience in

hybrid PV/diesel system installation, the use of such system,

especially in remote areas should gain wider consideration in

Malaysia.

Another successful implementation of hybrid PV/diesel project

in Malaysia is described in [7]. In the paper, the authors conducted

studies on the alternative energy design scheme for an Informa-

tion and Communication Technologies (ICT) Telecenter. The

authors remarked that hybrid PV/diesel energy system was more

practical than standalone diesel generator. This has yet proven

economically the potential use of hybrid PV/diesel energy system

in Malaysia.

According to Farret et al. [8], there are four majoraspects related

to distributed generation which involve the use of renewable

energy. They are the hardware and control, effect on the grid,

interconnection standards and economic evaluation. Since hybrid

PV/diesel system is a standalone system which does not involved

interconnection to the grid or with other renewableenergy sources,

this report will seek to analyze the potential use of hybrid PV/diesel

system with and without battery to determine its suitability in

remote areas, in the perspective of hardware and economical

analysis.

HOMER software has been used to perform the techno-

economic feasibility of hybrid PV/diesel energy system. The inves-

tigation demonstrated the impact of PV penetration and battery

storage on energy production, cost of energy, number of opera-

tional hours of diesel generators for a given hybrid configurations.

Emphasis has also been placed on percentage fuel savings andreduction in carbon emissions of different hybrid systems. The

suitability of the hybrid PV/diesel energy system over the

standalone diesel system was discussed mainly based on different

solar irradiances and diesel prices.

2. HOMER software

HOMER is a computer model that simplifies the task of evalu-

ating design options for both off-grid and grid-connected power

systems for remote, stand-alone and distributed generation (DG)applications [9]. It has been developed by United State (US)

National Renewable Energy Laboratory (NREL) since 1993. It is

developed specifically to meet the needs of renewable energy

industrys system analysis and optimization.

There are three main tasks that can be performed by HOMER:

simulation, optimization and sensitivity analysis. In the simulation

process, HOMER models a system and determines its technical

feasibility and life cycle. In the optimization process, HOMER

performs simulation on different system configurations to come

out with the optimal selection. In the sensitivity analysis process,

HOMER performs multiple optimizations under a range of inputs to

account for uncertainty in the model inputs. Detailed description

on HOMER software can be found in [8].

3. Background information

3.1. User load

It was assumed that the remote residential area consisted of

a total of 40 houses. Each house required loads of 2 kW peak.

Therefore, 40 houses would require a maximum of 80 kW peak

demand, approximately.

The daily load profile of a typical remote inhabitant area is as

shown in Fig. 1. It can be noticed that load requirement varies

throughout the day, with the maximum demand occurs at night.

Since the area investigated was a purely residential area, most of

the users will not be at home in the morning or afternoon.

However, at noon, family members would be at home for lunch and

rest, which caused the load demand to increase.

Load requirements further changes according to each month.

This is shown in Fig. 2. It was assumed that the hottest month

occurs between May to August. Therefore, the load requirements

would be high for those few months. However, from November to

January, more cloudy days are expected and the weather would be

cooler. Thus, it was assumed that those few months would require

less electricity demand, especially for cooling purpose (e.g. fan).

A random variability factor was given to HOMER software in

order to estimate differences that may be encountered each day

when using the load profile. They are known as day-to-day vari-

ability and time-step-to-time-step variability, with each approxi-

mated to be around 2% respectively. Based on all of the assumption

made, the energy demand required by the remote inhabitant area,

as simulated by HOMER software, was estimated to be about

1156 kWh/day (or 421.94 MWh/year).

Fig. 1. Daily load profile.

Fig. 2. Monthly load profi

le.

K.Y. Lau et al. / Energy 35 (2010) 3245e32553246


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3.2. Solar radiation

From the data provided by Malaysian Metrological Department

[10], the solar radiation data for the selected remote area was

estimated to range between 4.8 kWh/m2 and 6.1 kWh/m2. This is

illustrated in Fig. 3. It can be noticed that more solar irradiance can

be expected from the month of May to August while less solar

irradiance is to be expected from November to December. This

correlates to the load requirements as discussed earlier (refer

Fig. 2). The scaled annual average of the solar radiation was esti-

mated to be 5.51 kWh/m2/day.

The HOMER software can generate the clearness index from the

solar radiation data obtained from [10], according to the latitude ofthe place that has been chosen. In this analysis, the latitude was

selected to be 1280 North, according to data provided by [11]. It

should be highlighted that this latitude was chosen just for simu-

lation purposes, whereby it was assumed that a remote location

existin such an area. With this information,if thesolarradiationdata

isnot available, clearnessindex canalsobe used togeneratethe solar

radiation data. Therefore, either the clearness index or the solar

radiation data can be used to represent the solar resource input, as

long as the data of latitude is available to the HOMER software.

3.3. Diesel

Currently available diesel price in Malaysia is RM 1.70 per liter.

This value, when convertedinto US dollar ($), would be about $0.49per liter. Unfortunately, according to AsiaOneNews [12], the price of

diesel can be unreasonably high in rural areas. Checks found that

diesel is priced at about RM 7.00 ($ 2.03) per liter in many places in

the Ulu Baram district, some 200 km inland from Miri, Sarawak.

Therefore, in this simulation, diesel price was varied to determine

its effect on the system, since current global fuel shortage is also

causing the potential increase in diesel price.

4. Design specification

In a hybrid PV/diesel energy system, there are four main

components to be considered. They are the generators,PV modules,

batteries and converter.

Fig. 3. Solar radiation data.

Fig. 4. Hybrid PV/diesel energy system.

Table 1

Data for selected components.

Description Data

PV

Size 60 kW

Capital cost/replacement cost $ 5600/kW

Operating and maintenance cost $ 0/year

Lifetime 25 years

Storage battery

Type of battery Surette 6CS25P

Nominal voltage

(2 batteries per string)

6 V (12 V)

Nominal capacity 1156 Ah

State of charge 40%

Nominal energy capacity of

each battery

6.94 kWh

Capital cost $ 1100

Replacement cost $ 1000


Inverter

Size 60 kW

Capital cost $ 900/kW


Lifetime 15 years

Efficiency 90%

Diesel generators

Number of generators 2

Size 50 kW each

Capital cost $ 500/kW each

Replacement cost $ 400/kWh each

Operati ng and main tenanc e c ost $ 0.025/h our/kW each

K.Y. Lau et al. / Energy 35 (2010) 3245e3255 3247


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For the purpose of simulation, the hybrid PV/diesel energy

system was designed in such a way that it consisted of two diesel

generators, one photovoltaic array, one inverter and a battery bank

(optional), to supply to the AC load. This is illustrated in Fig. 4.

In order to meet the user ACload profile as discussed previously,

the following design specifications for each of the component are

provided.

4.1. PV module

Solar energy is used as the baseload power source. In an isolated

system, the renewable energy contribution of 50% is considered tobe high. Such a system might be very difficult to control while

maintaining a stable voltage and frequency. The level of renewable

energy penetration in hybrid systems (deployed around the world)

is generally in the range of 11e25% [13].

The designed PV array size was 60 kW. This amount would be

enough to cater for the load in the day (about 50 kW). The excess

power generated would be used to charge the battery bank. Each of

the proposed PV modules is rated at 50 W, with a 12 V nominal

voltage.

In order to obtain a total generation of 60 kW,1200 moduleswere

stacked together. Since the area of each module would be 0.451 m2,

the total modules resulted in an area of 540.652 m2.

It should be highlighted that this PV array would only generate

electricity at day time, from 6 a.m. to 6 p.m. At night, there is noelectricity generated. Therefore, the output from solar would be 0 W.

At night, either the battery or the generators will take over the task.

For economical analysis, it was assumed that each kW of PV

modulewould cost $ 5600. The cost of replacement wasassumed to

be the same as the initial cost. Operatingand maintenance cost was

assumed to be zero since it is negligibly small.

4.2. Storage battery

The storage battery chosen was Surrette 6CS25P. These batteries

were configured such that each string consisted of two batteries,

Fig. 5. Configuration of hybrid PV/diesel energy system.

Fig. 6. Comparison between different energy systems.



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with a total of six strings. This means the total batteries used were12 units, with a bus nominal voltage of 12 V. This battery bank is

capable of providing about one hour of electricity.

From the datasheet given by HOMER software, the minimum

state of charge of the battery is 40%. Its round trip efficiency is 80%.

The batterys capital cost was assumed to be $ 1100; replacement

cost $ 1000; operating and maintenance cost $ 10/year.

4.3. Diesel generator

Diesel generator is usually sized to meet the peak demand of the

power [14]. Since the peak demand of the residential area is 84 kW,

two diesel generators were chosen, each with 50 kW capacity,

which resulted in a total capacity of 100 kW. The excess 16 kW from

the generators will cover the spinning reserve of about 19%. Thiswould cater for the additional loads in the future.

The generators mainly operate at night since solar power is not

available at this time, and the load demand is higher at night. In the

day time, one of the generators would operate if the solar power

and the battery could not meet the load demand.

The initial cost and the replacement cost of 50 kW generator

was assumed to be $ 25,000 and $ 20,000 respectively. For oper-

ating and maintenance cost, it was assumed to be quite high, with $

1.25/hour. This is because the area considered is a remote area.

Therefore, difficulty arises in transportation problem when main-

tenance is required, which would indirectly add up the cost. Each of

the generators was assumed to have a lifetime of 15,000 operatinghours.

4.4. Inverter

The inverter was rated based on the selected PV array. Since

60 kW output would be generated from PV, the inverter was rated

at 60 kW to fully supply the power from PV. However, it is assumed

that the inverter has an efficiency of 90%. Therefore, the supplied

power would be less than 60 kW. The initial cost of the inverter is

assumed to be $ 900, which is the same as the replacement cost.

There was no operating and maintenance cost estimated.

A brief summary on the data for each of the selected compo-

nents is provided in Table 1.

5. Operating strategies

The designed system was assumed to operate load following

dispatch strategies. This means that only PV array will charge the

battery bank. Generators would not charge the battery bank. They

would only generate power to serve the required load.

The configuration of the hybrid PV/diesel system is as shown in

Fig. 5. The PV was used as the base load supply which produced DC

power. It was then converted into AC source by using an inverter.

Since the PV will charge the battery bank, this happens when there

is extra power after meeting the demand of the end user load. If the

Fig. 7. Total NPC for standalone diesel system.

Fig. 8. Monthly average electric production for standalone diesel system.



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PV cannot meet the demand, the battery bank will not be charged,

but being discharged to cater for the demand.

Generator 1 and Generator 2 will operate if both PV and battery

bank cannot meet the demand. It should be highlighted that

Generator 1 will be more frequently operated. Meanwhile, Gener-

ator 2 mainly operates at night since solar energy is unavailable at

night. In other words, during the day, the PV and Generator 1 will

operate. At night, Generator 1 and Generator 2 will operate.

The operating reserve as a percentage of hourly load was 10%.

Meanwhile, the operating reserve as a percentage of solar power

output was 25%. Operating reserve is the safety margin that helps

ensure reliability of the supply despite variability in electric load

and the solar power supply. For an example, if the load at an hour is

50 kW and the PV output is 30 kW, this means that the operating

reserve would be 5 kW 7.5 kW12.5 kW. The diesel generator

must therefore provide 20 kW of electricity plus 12.5 kW of oper-

ating reserve. This means that the capacity of the operating

generator must be at least 32.5 kW.

6. Results and discussions

Simulation was performed by comparing the use of standalone

diesel system, hybrid PV/diesel system without battery, and hybrid

PV/diesel system with battery. It was done based on a projection

period of 25 years and 6% annual real interest rate. The PV capacity

was varied from 0 kW to 100 kW while the battery storage was

varied from 12 units to 36 units for comparison purpose. The result

of the simulation is shown as in Fig. 6.

It should be highlighted that the 6% annual real interest ratewas

applied to the investment cost as well as the diesel price. Since

HOMER assumes all prices escalate at the same rate, it is not

possible to model the escalation of diesel price at different rate.

Therefore, calculations are based on current diesel prices and do

not reflect the effects of possible further increases of the diesel

prices. It is possible, however, to explore the effects of an escalating

diesel price by doing a sensitivity analysis on the diesel price.

It should be noted that the hybrid diesel/battery system is

presented in Fig. 6. However, since the load following dispatch

strategy was used, the generator will not charge the battery, except

that at the beginning of the simulation, the software might assume

that battery was available. But the battery will not be charged after

being discharged for just one single cycle. Therefore, this combi-

nation will not be discussed, since its configuration is somehow the

same as the diesel only system. However, it appeared in the

simulation since HOMER software will calculate for each of the

possible combinations.

Fig. 9. Total NPC for hybrid PV/diesel system without battery.

Fig. 10. Monthly average electric production for hybrid PV/diesel system without battery.



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6.1. Standalone diesel system

From HOMER simulation, the use of standalone diesel system

was the cheapest, with the total Net Present Cost (NPC) of

$1,482,455. This was according to the global solar irradiance of

5.51 kWh/m2/d and diesel price of $ 0.49/L. Detailed breakdown of

the NPC is shown in Fig. 7. It can be noticed that the largest portion

of NPC came from generator 1, since it operates most of the time.

Monthly average electric production is shown in Fig. 8. It can be

noticed that Generator 1 will operate the most, followed by

Generator 2. This means that Generator 1 served as the base load. If

Generator 1 could not meet the load demand, Generator 2 would

operate to cover for the inadequacy. In other words, Generator 1 is

always ON (1 start/year, according to the simulation). Generator 2,

on the other hand, will be turned ON and OFF depending on the

load demand (847 starts/year, according to the simulation).

It could be further noticed that the monthly average electric

production match the monthly load profile as given in Fig. 2. As

mentioned earlier, the demand for electricity is the highest from

May to August, which resulted in the higher electric generation for

those months. Meanwhile, for period between November to

January, the demand of load is lower. This resulted in lower

generation of electricity, as shown in Fig. 8.

From HOMER simulation, if only generators are used to supply

for all the loads, Generator 1 would produce electricity of

344,493 kWh/year (82%), while Generator 2 would produce elec-

tricity of 77,447 kWh/year (18%). This gives the total electricity

generation of 421,940 kWh/year (100%) to meet the load demand.

Since solar photovoltaic is not being considered, there was no

electricity from the PV. It should be noted that the cost of energy

(COE) for diesel only system was $ 0.275/kWh.

To determine the feasibility of hybrid PV/diesel installation, two

types of configurations was analyzed, one without storage element

(battery) and one with storage element (battery) respectively.

6.2. Hybrid PV/diesel system without battery

As highlighted by Shaahid et al. [13], the level of renewable

energy penetration in hybrid systems (deployed around the world)

is generally in the range of 11e25%. From the simulation, the

proposed hybrid PV/diesel system (one unit of 60 kW PV array, two

units of 50 kW diesel generator, without battery) satisfied the PV

Fig. 11. Total NPC for hybrid PV/diesel system with battery.

Fig. 12. Monthly average electric production for hybrid PV/diesel system with battery.



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penetration of 22%. The utilization of PV array size more than

60 kW is out of consideration since it would result in higher values

of the total NPC as well as the COE (as compared to60 kW PVarray).

In addition, higher contribution of renewable energy fraction might

result in difficulties in control while maintaining stable voltage and

frequency [13]. On the other hand, reducing the PVarray size wouldresult in higher dependence of diesel generators. This is not

favorable since the objective is to reduce the dependence on diesel.

Therefore, the use of 60 kW PV array is justified.

By using the proposed hybrid PV/diesel system without battery

(one unit of 60 kW PV array, two units of 50 kW diesel generator,

without battery), the total NPC was $ 1,669,299. This combination

was the most expensive among the 22% renewable energy fraction.

One of the main reasons is because the power generated by PV is

not being fully utilized. The excess solar power, which could have

been used to charge a battery (which was not available in this case),

was considered a loss. As a result, when the PV cannot meet the

demand, there was no storage element that existed to cover the

increased demand. The generator will have to be operated in order

to cope for the demand.Both the NPC for Generator 1 and Generator 2 have been

reduced (as compared to standalone diesel system) since PV is

available to supply the load. However, the initial PV cost is quite

high, which mainly contribute to the extremely high total NPC cost

(refer Fig. 9).

The monthly average electric production is shown in Fig. 10. For

Generator 1, no significant reduction can be noticed as compared to

the standalone diesel system. Electric production from Generator 2

has somehow been reduced due tothe existence of PV. The PV array

provided energy of 96,512 kWh/year (22%). In other words, PV

penetration was 22%. Generator 1 provides energy of 292,127 kWh/

year (66%). Generator 2 provides energy of 51,871 kWh/year (12%).

This means that Generator1 still operatesthe most, followed by the

PV and then Generator 2. Comparing this system with the

previously analyzed standalone diesel system, the electricity

output of Generator 1 has reduced for about 15%. Meanwhile,

electricity output from Generator 2 decreased by 33%. This means

that the dependence on diesel has also been reduced.

The cost of energy for this type of system is $ 0.309/kWh.

Meanwhile, its operating cost would be $ 96,164/year. Since batterywas not available, the operating hours of Generator 1 was the same

as standalone diesel system. The use of PV caused the operating

hour of Generator 2 to reduce to 3126 hours (4826 hours when

using standalone diesel system). This resulted in a total saving of

diesel, for approximately 16.5% as compared to standalone diesel

system.

However, as mentioned earlier, this type of configuration does

not take into account of energy storage. The electricity production

generally depends on either PV or the generator to supply the load.

If PV is insufficient or unavailable, the generator will take over the

task.

From renewable energy viewpoint, battery storage is important

to ensure that the excess of power produced from PV can be stored

for later use. This would greatly optimize the system. The followingdiscussion will focus on the hybrid PV/diesel system with battery.

6.3. Hybrid PV/diesel system with battery

From the simulation result shown in Fig. 6, it can be noticed that

the higher number of batteries would increase the total cost of the

system. Therefore, 12 units of batteries (1 h of autonomy) were

considered to be sufficient. Considering the use of hybrid PV/diesel

system with battery (one unit of 60 kW PV array, two units of

50 kW diesel generator, with 12 units of battery), it can be noticed

that operating cost of the system has been reduced to $ 89,170 per

year. This was the cheapest among the different configurations

proposed. This is a huge reduction as compared to the standalone

diesel system. However, the total NPC was still high, which was

Fig. 14. Comparison between different energy systems with high diesel price.

Fig. 13. State of charge of battery.



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about $ 1,593,086. This is due to the extremely high initial capital

cost for PV installation, which will not occur if a standalone diesel

system is used. This is shown in Fig. 11. Despite Generator 1s NPC

still being high, it is lower if compared to the standalone diesel

system. The same principle is applied to Generator 2. However, the

use of the PV, inverter and batteries has added up the total NPC of

the system.

The monthly electrical energy production for hybrid PV/diesel

system with battery is shown in Fig.12. Itcanbe noticed thatPV has

taken over the Generator 1s function as the supply tothe base load.

Since battery storage capacity was quite small (only 1 hour of

autonomy supply), its portion can hardly be noticed as shown in

Fig. 12. The PV array provided energy of 96,512 kWh/year (22%).

Generator 1 provides energy of 307,023 kWh/year (70%). Generator

2 provides energy of 32,086 kWh/year (7%). The batteries provide

energy of 2301 kWh/year (less than 1%) due to its low energy

storage.

Up to this point, it should be highlighted that most of the load

demand occur at night time, which is when the PV is not available.

At this time, the battery will function to supply the load, since PV is

not available. Unfortunately, the battery storage can only provide

up to 1 hour of supply. After that, generators will operate to supply

the load.

With the availability of PV, Generator 1 does not need to operate

nonstop throughout the year. It will only operate when the PV and

batteries cannot meet the load demand. From the simulation, the

Fig. 15. Total NPC for hybrid PV/diesel system with battery under high diesel price.

Fig. 16. Total NPC for standalone diesel system under high diesel price.



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start cycle for Generator 1 is 98 starts/year. For Generator 2, it had405 starts/year.

The state of charge of the battery bank is shown in Fig. 13. Since

May to August has the highest demand of energy, the battery can

hardly maintain its charge. It should be noted that the minimum

battery charge need to be maintained at 40%, as provided by the

specification and should not fall to less than 40%.

The use of battery allows the reduction of Generator 1 and

Generator 2 operating hours. The operating hours for Generator 1

has been reduced to 8545 h. For Generator 2, it has been reduced to

1807 h. This shows that battery has significant contribution in the

long run. As compared with the hybrid PV/diesel system without

battery, electricity generation from Generator 2 has been reduced

significantly for this type of system. At the same time, dependence

on diesel was found to be much lower. The total consumption ofdiesel has been reduced by about 21%. Besides that, excess elec-

tricity from PV has also reduced from 9910 kWh/year (without

battery) to 3999 kWh/year (with battery).

6.4. High price of diesel

As highlighted previously, the price of diesel can be unreason-

ably high in rural areas. Checks found that diesel is priced at about

RM 7.00 ($ 2.03) per liter in very remote places where the cost of

transportation of goodsand fuel is very expensive such as in the Ulu

Baram district, some 200 km inland from Miri, Sarawak. Therefore,

this section seeks to discuss the effect of such high diesel price on

the utilization of hybrid PV/diesel system.As shown in Fig. 14, the use of hybrid PV/diesel system with

battery has benefited significantly when the cost of the diesel is as

high as $ 2.03 per liter, with the same solar irradiance of 5.51 kWh/

m2/day as analyzed previously. In such a circumstance, the use of

hybrid PV/diesel with battery was found to have the least total NPC,

approximately $ 4,292,632. Its operating cost would be about $

300,346/year with its COE of $ 0.796/kWh. Fig. 15 shows break-

down of the NPC.

However, if the standalone diesel system was used to supply the

energy, the total NPC would yield up to $ 4,628,908 (refer Fig. 16),

which is 7.8% more compared to the use of hybrid PV/diesel system

with battery. Besides that, the cost of energy would also be higher,

about $ 0.858/kWh, which is about $ 0.09/kWh more expensive

than the hybrid system.

From this simulation, it can be seen that although the initialcapital cost of the hybrid PV/diesel energy system was extremely

high ($ 453,200) as compared to standalone diesel system ($

50,000), it can be compensated within the projected lifetime of 25

years, with the annual real interest rate of 6%. Therefore, for high

price of diesel, it was proven that the use of hybrid PV/diesel system

with battery is the best solution in remote areas.

6.5. Sensitivity analysis

As highlighted previously, the total NPC of hybrid PV/diesel

system with battery was still higher as compared to standalone

diesel system, provided if diesel price is low enough. However, if

the diesel price increases considerably, the total NPC of hybrid PV/

diesel system with battery would be the lowest among all other

systems. For this reason, the value of global solar irradiance and

diesel price has been varied in order to determine the suitability of

the implementation of the different types of energy systems.

Fig. 17 shows the appropriate implementation of those three

generating systems under different global solar irradiance and

diesel price. The optimized option would be such that if the diesel

price is less than $1.05/L, the use of the standalone diesel system

would still be the cheapest among all. The choice of the hybrid PV/

diesel system is only feasible if the diesel price is more than $1.05/L.

On the other hand, it can also be noticed that the use of battery in

hybrid PV/diesel system does not always yield the cheapest solu-

tion as compared to the one without battery. In other words, the

Fig. 17. Optimal system type.

Fig. 18. Pollutants emissions for standalone diesel system.



11/11

use of battery would become the best option when the diesel price

is more than $1.6/L, or when the global solar irradiance is higher.

This is best explained in the shaded area as shown in Fig. 17.

6.6. Harmful gas emissions

Since the use of diesel generally causes air pollution, in thissection, a comparison between standalone diesel system and

hybrid PV/diesel system with battery is done, in terms of harmful

gas emissions. It should be noted that the analysis assumed no

penalty cost to be imposed for the pollutant. However, if non-zero

cost penalty is imposed for a particular pollutant, HOMER will add

the cost to the total annual cost of the system.

As shown in Fig. 18, for standalone diesel system, the total

emissions of pollutants were 432,259 kg/year.

For the hybrid PV/diesel system with battery, total emissions

were 342,246 kg/year (refer Fig. 19). This has shown considerable

reduction in emission with the introduction of PV system.

7. Conclusion

From HOMER software simulation, it has been demonstrated

that the use of hybrid PV/diesel system with battery (one unit of

60 kW PV array, two units of 50 kW diesel generator, with 12 units

of battery) can significantly reduce the dependence on solely

available diesel resource. Although utilization of hybrid PV/diesel

system with battery might not significantly reduce the total NPC

and COE, it has been able to cut down the dependence on diesel. In

addition, it also helps to reducepollutants,such as carbon emission,

thus reducing the green house effect. On the other hand, it was also

proven that the use of hybrid PV/diesel system with battery would

be more economical if the price of diesel increased significantly.

With a projection period of 25 years and 6% annual real interest

rate, it was found that the use of hybrid PV/diesel system with

battery could achieve significantly lower NPC and COE as compared

to a standalone diesel system. As a conclusion, the hybrid PV/diesel

system has potential use in remote areas, especially in replacing or

upgrading existing standalone diesel systems in Malaysia.

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Fig. 19. Pollutants emissions for hybrid PV/diesel system with battery.

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