IEEE Africon 2017 Proceedings
Hybrid energy system for low-income households
O.M Babatunde, J.L. Munda, Y. Hamam
Dept. of Electrical Engineering
Tshwane University of Technology
Pretoria, South Africa
olubayobabatunde@gmail.com, mundaJL@tut.ac.za, HamamA@tut.ac.za
Abstract— This paper presents an analysis of an off-grid
hybrid energy system (HES) for a single residential
apartment owned by a low-income earner. The system is
made up of photovoltaic (PV), wind, battery storage system,
and a gasoline generator. Using a house in Akoka, Nigeria
as a case study, the HES is developed to adequately supply a
load of 3.8kWh/day. The technical, economic and
environmental considerations are presented. The results
revealed the potential of the HES to provide environmentfriendly, cost-effective and affordable electricity for the low
income household, as compared to using only gasoline
generators
Keywords—hybrid energy system, low-income household;
HOMER; affordability; techno-economic
I. INTRODUCTION
Developing countries are faced with the twofold challenge of
shortage of modern, clean electricity and high dependence on
exhaustible fossil fuels. Over 620 million people in subSaharan Africa lives without access to electricity [1]. This is
the largest in the world and about 50%of the total population
of people living without electricity worldwide
Access to affordable, reliable and green modern electricity
was listed as part of the criteria for achieving the United
Nation’s sustainable developmental goals of transforming the
world to a better place for all, by 2030”.The goal seeks to
significantly increase the renewable energy penetration in the
global energy mix [2]. Target 7a of the sustainable goal
expects investment in renewable energy infrastructure as well
as clean technology to increase by 2030 so as to make
electricity available to a wider spectrum of people [2].
Consequently, this will reduce the poverty level, health related
diseases and the damages caused by emissions as well as
increase access to improved quality of living [3].
In response to this, most developed economies have adopted
the integration of renewable energy sources (RES) in the
energy mix of their respective countries. As reported in [4],
renewable energy is ranked and considered the first source of
power generation in Europe. Countries like Norway, Iceland,
Denmark, Albania, etc. have achieved more than 50%
renewable energy contribution as of 2015. In order to achieve
target 7a of the sustainable developmental goal, there is a need
to intensify efforts in the adoption of RES. Adoption of RES
starts with enlightening electricity consumers on the economic
and environmental advantages of adopting the system.
According to Monroy and Hernandez [5], in a survey carried
out by renewable energy professionals, financing hybrid
renewable energy system (HRES) projects is the main
limitation to its adoption. Respondents identified that a huge
initial capital is involved in the implementation of such
projects as a bottleneck. It is, however unclear if respondents
were able to compare the long-term benefits to the cost of
implementing a renewable energy project. Rather than dwell
on the advantages of HRES, many low-income households
whine about the “up-front cost” of adopting the technology.
Presently, Nigeria, a country with a population of about 140
million people generates less than 4000MW of power when at
its best [6]. This is less than 30W per head– an indicator of
energy poverty in the country. Consequently, about 44% of
Nigerian households lack adequate access to electricity supply
or experience severe shortage of electricity supply.
Meanwhile, in order to meet the unserved energy needs,
majority of the low-income households in Nigeria opt for
gasoline generators despite its high cost of maintenance which
they consider more affordable than adopting the renewable
energy technology. This is a result of the very little
information available about its numerous advantages and other
facts such as the actual life cycle cost, and the best method of
raising such initial capital cost. Numerous literature exists on
techno-economic analysis of HRES implementation [7-16]. As
a contribution, the aim of this study is to analyze the technoeconomic, environmental benefits of renewable energy
technology and more importantly the cost effectiveness of
HRES for low-income households. This will provide major
insights to ways of acquiring HRES for low income
households.
II.
A. Project location
This study made use of a location in Akoka, Lagos, Nigeria
(6o32’27oN, 3o23’E). Based on the afore stated benefits of
adopting renewable energy sources, an analysis of utilizing
small scale wind turbine, PV as well as gasoline generator is
carried out. Presently, the majority of people in the area makes
use of the epileptic grid supply and gasoline generators.
Considering the high cost of operation and maintenance of the
gasoline generators, there is a need to explore the renewable
energy technology to meet load requirements. Described in this
section are the parameters used in the simulation and analysis
of the proposed hybrid system. Mathematical model details for
all components used in this study can be obtained in [15], [16].
All techno-economic and environmental analysis are performed
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978-1-5386-2775-4/17/$31.00 ©2017 IEEE
METHODOLOGY
IEEE Africon 2017 Proceedings
by HOMER based on these mathematical models. It is
important to state that though Lagos state, Nigeria was selected
as the study site, the methodology of this research can be
reproduced globally.
B. Renewable energy resources
The solar and wind resources for Akoka was retrieved from
NASA website [17]. Fig.1 shows the average monthly solar
radiation and the clearness index for the site. The annual scaled
average value is 4.69 kWh/m2/day. The lowest and the highest
radiance occurred in August and February respectively. A chart
showing the monthly average values of wind speed related to
the case study location is given in Fig. 2. It is evident from this
figure, that the minimum speed of 2.8 m/s is experienced in
October and maximum of 4.3 m/s in February. The average
wind speed for the whole year is 3.5 m/s.
Global Horizontal Radiation
1.0
5
0.8
0.6
3
0.4
2
0.2
1
0
energy demand (kWh)
4
Clearness Index
Daily Radiation (kWh/m²/d)
6
(electricity consumption) will be minimal during this period.
Appliances such as iron and fridge operate intermittently for a
few minutes during the night. The two fans only operate
concomitantly from 8 pm-10 pm after which one is switchedoff. Except for the pressing iron, it is assumed that all
appliances in use are energy efficient and consume less
energy. It is also worth noting that the load model is analysed
based on the dry season demand. The utilisation of energy in
Nigerian households is at the peak in the dry season because
of the demand for adequate cooling and ventilation. For the
load model in this study, the demand peaks between 4 am and
6am as people prepare to go to work and also between 8 pm
and 10 pm (as people retire from work) after which it drops as
the consumer goes to bed. The demand by individual
appliance is estimated for 24 hours and its cumulative value is
estimated. In order to obtain the annual load, HOMER was
used to obtain the load profile. The daily demand and power
are 3.8 kW h/d and 874 W at peak respectively. Fig 3 shows
the load profile of a typical low-income household.
Jan
Feb
Mar Apr May Jun
Daily Radiation
Fig. 1
Jul
Aug Sep Oct
Nov Dec
0.0
Clearness Index
Average monthly solar radiation and the clearness index for Akoka
Wind Resource
3.5
0.6
0.5
0.4
0.3
0.2
0.1
0
0
W i n d S p e e d (m /s )
3.0
2
4
6
8 10 12 14 16 18 20 22
hour of the day
2.5
Fig. 3.
2.0
1.5
1.0
0.5
0.0
Fig. 2
Jan Feb Mar
Apr May Jun
Jul
Aug Sep
Oct Nov Dec
Monthly average wind speed for Akoka
C. Load profile
In this study, it is assumed that the consumers are junior staffs
of the University of Lagos, Nigeria. Junior staffs are usually
considered as low-income earners. The 24-hour load demand
for a typical low-income household is shown in Fig. 3. This
was estimated based on the various appliances (television,
iron, fan, lamp and fridge) as shown in Table 1. It is also
assumed that the occupant will be away from home on
weekdays between 8 am – 6 pm which implies that demand
24-hour energy demand for a typical low-income earner household
D. Other input parameters
Based on the solar and wind resource available at the study
site, the proposed hybrid system will be a combination of the
PV array, wind turbines, diesel generators and storage
batteries. Fig. 4 shows the schematics for the possible
configuration and individual components. Final configuration
and actual sizes, is decided after performing optimization.
Multiple solution candidate values and other requirements are
entered into HOMER. The PV module technical parameters
used here are as presented in [15] and the economic details of
the components are presented in Table 3. Economic values
are based on the literature as well as the dollar equivalent of
market prices [3], [15]. A 12% annual real interest rate was
applied.
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IEEE Africon 2017 Proceedings
TABLE 1. TYPICAL APPLIANCE RATING AND LOAD DEMAND FOR LOW-INCOME HOUSEHOLDS
Qty
Television
Iron
Fan
Lamps
Fridge
Others
1
1
2
6
1
Power
(W)
Total
power (W)
Daytime hours
(07:00–17:59)
Evening hours
(18:00–21:59)
Night hours
(22:00–06:59)
Total
Hours/day
Total energy
(kWh/day)
65
1000
65
18
65
50
65
1000
130
108
65
50
0
0
0
3
1
0
5
0.17
3
3
1
3
0
0
9
2
4
2
5
0.17
12
8
6
5
0.33
0.17
0.98
0.59
0.39
0.25
TABLE 2. COMPONENT DATA
Cost
Component
($/kW)
Replacement
cost ($/kW)
Operation &
maintenance cost
Sizes consider
Life
span
PV
4250
4200
0$/yr
0-5kW
20yrs
Battery (4V,1900Ah)
269
260
5$/yr
0,6,12,18,24,32,40 (No)
4yrs
Converter
622
569
3$/yr
0,1,2,3,4 (kW)
15yrs
Gasoline Gen. (2.6kW)
900
900
0.04$/hr
0.4,0.5,0.75 (kW)
15,000hrs
Wind turbine (3kW DC)
1200
1100
20/yr
0,1,3 (No)
15yrs
III.
RESULTS AND DISCUSSION
A. Techno-economic
A system configuration of 1kW PV, 400W gasoline generator,
6 batteries and 1kW converter would be the most
economically feasible with a minimum total net present cost of
$4654 and cost of energy of $0.442/kWh. Its initial setup cost
is $2682 while its renewable fraction is 98% of the total
energy production. Consumers using this architecture would
only need to run the gasoline generator for 121 hours annually
as compared to 4745 hours if only gasoline generator is used.
The system with the lowest initial capital cost is the gasoline
generator only system which requires $288 for setup. This
system incurs the second highest operating cost of $655
annually. This in turn increases its TNPC and it is estimated as
$7285. This is approximately 56% higher than the most
economically viable system. The most expensive option for
generation is the wind-battery system with 2 wind turbines, 32
batteries and 1 kW inverter. The capital cost for this system is
$14, 923, TNPC of $22,842, COE of 2.17$/yr and RF of
100%. Other economic metrics are given in Table 3. When
the optimal system is compared with the generator only
system, a simple payback period and discounted payback
period of 4.05 years and 4.96 years respectively is achievable.
consumed by the generator. This information is then employed
to estimate the quantity of emissions produced by the
generator. Various values of CO 2 emission factors were
reported in [15]; 3.20, 3.15 and 3.00 kg CO2 per litre of diesel,
respectively. For the purpose of this work, emission factor of
2.66 kg CO2 per litre of fuel is adopted by HOMER to
evaluate the quantity of carbon dioxide. Comparison of
emission results of the optimal system and the Generator only
system as indicated by HOMER is given in Table 4.
Fig. 4. Architecture of the proposed HRES system
B. Environmental
The environmental merit of the optimal PV-generator system
is first considered in terms of the amount of fossil fuel
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IEEE Africon 2017 Proceedings
TABLE 3. RESULT OF ECONOMIC INDICES
40
Payment
1,800
35
Total Interest
1,600
1,400
30
1,200
25
1,000
20
800
15
600
10
400
5
200
Annual Interest Rate
0
10.0%
9.0%
0
8.0%
C. Affordability
Generally, the affordability of the PV technology will depend
largely on the load demand and the accessibility of initial
capital. The initial capital depends on the income of a
prospective household. The higher the load to be served, the
higher the system requirement and also the investment cost.
Load demand may be reduced with the adoption of energy
efficient appliances and energy conservation techniques.
The challenge of raising the initial cost of assembling the
system can only be addressed through access to credit
facilities from relevant credit organisations. The majority of
the government workers in Nigeria form cooperative societies
(in their respective organisations) which provides easy access
to loans as high as twice an individual cumulative savings.
Depending on the cooperative society, interest rates vary from
5% to 10% with the most common being 10%. Payment plan
can be spread over a short duration or long term as long as the
beneficiary remains in active service of the organisation. This
will enable deduction of payments directly through employers
before the monthly salary payment is received by the
employee. Based on the current exchange rate, low-income
earners particularly junior government officers in Nigeria earn
between $607 and $2200 annually. On the average a junior
officer earn about $1403 dollars annually. The analysis in this
section is based on the assumption that the annual
remunerations of participant in the programme will not go
below $ 1403. The housing allowance is about 11% of the
total remunerations. Many workers are still able to save close
to 10-20% of their salary monthly. For the purpose of this
analysis, since the cooperative societies involve a large
number of members who will be willing to participate in the
programme, the highest interest rate among the various
cooperative (10%) is expected to go down to as low as 2%.
Since banks have a larger capital base compared to these
cooperative societies, they may also be able to offer
competitive interest rate or collaborate with the cooperative
societies to adopt a flexible payment plan. From the results of
the optimal system presented in table 3, the initial capital for
setup is estimated at $2682. Fig. 5, shows the total interest
with the corresponding payment if the loan payment is made
monthly over a 10 year period.
7.0%
$
$/yr
%
%
yrs
yrs
6.0%
2,632
247
19.2
21.1
4.05
4.96
5.0%
Present worth
Annual worth
Return on investment
Internal rate of return
Simple payback
Discounted payback
4.0%
Unit
3.0%
Value
2.0%
Metric
Fig 5. Annual interest rate and corresponding payments
It can be seen that as the interest rate increases, so does the
periodic (monthly) payments made, and total interest paid on
the loan over the loan term. Consequently, if negotiation can
be made with loan providers to reduce the present 10% to 2%
a saving of at least 82% can be achieved on the total interest
paid. From Fig. 6, as expected the payment decreases with an
increase in the number of payments made. The payment value
is inversely proportional to the number of payments while the
total interest paid is directly proportional to the number of
payments. At the end of the tenth year (loan term payment due
date), with a 10% interest rate, a total of $4253 would have
been paid with the total interest estimated at $1571. Therefore,
at 10% (highest from survey) interest rate, a deduction of $35
will be made monthly from the employee’s salary. This is a
more flexible and fair payment plan as compared to making
low-income households pay a bulk sum of $2682.
250
Payment
1,800
Total Interest
1,600
200
1,400
1,200
150
1,000
800
100
600
400
50
200
0
0
12 18 24 30 36 42 48 54 60 66 72 78 84 90 96102108114120
Number of Payments
Fig. 6: Effect of number of payments on total interest and payments
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IEEE Africon 2017 Proceedings
TABLE 4. EMISSION RESULTS
[6]
Emissions (kg/yr)
Pollutant
Carbon dioxide
Carbon monoxide
Unburned hydrocarbons
Particulate matter
Sulfur dioxide
Nitrogen oxides
PV-Gen-Bat
36.60
0.09
0.01
0.007
0.07
0.80
[7]
Gen only
2,182
5.39
0.597
0.406
4.38
48.1
[8]
[9]
[10]
IV. CONCLUSION
[11]
Analysis, simulation and evaluation of affordable alternative
energy for low-income households in Nigeria have been
evaluated. The results of the simulation suggest that PVGasoline-battery combination offers the least total net present
cost. The optimal system architecture (PV-gasoline-battery)
has a TNPC of $4654 while the present means of power
generation (gasoline only) had a TNPC of $7285. Hence,
consumers switching from gasoline generator to hybrid PVgasoline-battery system configuration can save about
approximately 36% on the TNPC. Compared to the present
gasoline generator only used by majority in Nigeria, emission
can be minimised by 98.3% for an individual user. If this is
adopted nationwide, it will eliminate the emission of thousands
of tonnes of GHGs. As a contribution to literature, this study
proposed provision and acquisition of low interest loans for the
PV projects. A range of interest rates, the corresponding
interest payable and total payment on loan for solar energy
project for the optimal system was also evaluated. If paid over
a ten year period participant can pay between $24.68 and
$35.44 per month depending on the interest rate and the
frequency of payment. The implementation of this study can be
of benefit to low-income household worldwide.
[12]
[13]
[14]
[15]
[16]
[17]
ACKNOWLEDGMENT
The financial assistance of the National Research Foundation
(NRF) through the DST-NRF-TWAS doctoral fellowship
towards this research is hereby acknowledged. Opinions
expressed and conclusions arrived at, are those of the authors
and are not necessarily to be attributed to the NRF.
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