D-Lab I Final Report: Adapting a Solar Microgrid to Provide
Lighting in Rural Nigeria
Jon Cook, Laleh Rastegarzadeh, and Daniel Sheeter
Prepared for D-Lab, UC Davis
Feb. 14, 2011
1
Introduction
For most remote, off-grid communities in the Niger Delta, candles and kerosene lamps are
the primary sources of light for households after the sun goes down. In addition to being
relatively expensive, these lighting sources provide poor light and contribute to respiratory
problems when used in poorly ventilated indoor environments. As advanced lighting
technologies have continued to become more efficient and inexpensive, the goal of replacing
fuel-based lighting with electric light powered by small-scale renewable sources is becoming
increasingly possible.
1.1 Problem Statement
In this paper we address the feasibility of adapting an existing solar microgrid in India for
use in the small village of Aduku, Nigeria. The purpose of the paper is to analyze the technical
modifications of an existing microgrid in India that would be needed to set up a similar grid in
Aduku and also outline sets of equipment that could be used to create a functional pilot
microgrid in the community.
1.2 Description of Aduku
Aduku is a village in Niger Delta and similar to many other parts of Nigeria is not
connected to the national grid. Aduku is located in the state of Bayelsa (highlighted in Figure 1),
which is a coastal state in the heart of the Niger River delta. Bayelsa state is one of the newest
states in Nigeria, having been formed from neighboring Rivers state in 1996. It is the least
populated of the delta states (~ 1.1 million people), but is a major oil and gas producing area due
to its large crude oil deposits. The state government estimates that Bayelsa state currently
accounts for about 30% of Nigeria’s oil production. The intensity of oil exploration and
production has brought with it many conflicts between multinational oil companies, the Nigerian
government and local communities.
Figure 1 - Location of Bayelsa State
Source: http://commons.wikimedia.org/wiki/File:Nigeria_Bayelsa_State_map.png
Despite the vast amount of resources in the delta, quality of life remains poor. The
region’s human development index (HDI) score, a measure of well being encompassing the
longevity of life, knowledge and a decent standard of living, remains at a low value of 0.564
(with 1 being the highest score). Bayelsa state is slightly worse off than the rest of the delta with
an HDI score of 0.499 (UNDP 2006). Rural areas typically have a lower HDI than urban areas,
so we can reasonably expect that the HDI for the area immediately around Aduku is even lower
than that. As a whole, the region has little working infrastructure, low access to safe drinking
water and high child mortality rates. In Aduku, several attempts have been made to install solar
water pumps (by the World Bank and Niger Delta Development Commission), but as of yet none
have been successful and the community is still without good access to water. Our partner
organization, the Niger Delta Wetlands Center (NDWC), has had success in building solar water
pumps in other communities in the delta and is reportedly making plans to install one in Aduku.
In terms of environment, the Niger delta is made up of a vast network of rivers and creeks
that are surrounded by swamps, marshland and tropical rain forest (Figure 2). The area is almost
entirely below sea level and contains around 12,000 sq. km of mangrove forests, the largest such
forest in the world. Due to this difficult topography, 94% of the delta’s estimated 30 million
people live in settlements of fewer than 5,000 people that offer very little in the way of economic
opportunities (UNDP 2006). Aduku is no exception: it is a small village of about 86 households
on the bank of a large river where the primary activities are subsistence fishing, farming (goats
and cassava), palm oil production and logging.
Figure 2 - Satellite view of the Niger Delta
Source: http://www.imagekind.com/Niger-Delta-(Nigeria)-:-Satellite-Image-art?IMID=6c54ca41-9a46-4da4-bf778f82936144cc
One unique aspect of Aduku is its layout (Figure 3). The village is linear, with almost all
of the residences and businesses being located off of a main road/path that stretches from one
end of the community to the other. This road runs parallel to the River Aduku (a tributary of the
large River Forcados) and the area between the two is the primary land used for farming. Houses
are made of mud walls and have either a thatched roof or one made of zinc. In terms of density,
the majority of houses in Aduku (about 70 of 86) are located west of the north-south road that
connects Aduku to more populated parts of the delta. Landowners typically live directly across
the River Forcados in the Noari Community and not in Aduku proper. The linear nature of
Aduku is one of the most important features to consider when designing a microgrid due to the
impact it will have on wiring costs, battery size and placement of solar panels.
Figure 3 - Linear layout of Aduku
Source: NDWC
In terms of lighting, the status quo in Aduku (like most of rural Nigeria) involves the use of
candles, kerosene lamps and gasoline generators. Roughly one in three households in Aduku
have generators (~1 kW), but these devices are used primarily to power larger appliances. This
leaves the bulk of the ambient lighting load to be picked up by candles and kerosene lamps. The
current prices of gasoline, diesel and kerosene are about US $1.80, $3.60 and $1.50 per liter,
respectively, but the price of candles is still unknown as is the typical household’s monthly
expenditure on lighting. As of the writing of this paper, our group has not learned of any lighting
projects or studies that have been conducted in Aduku or the immediate surrounding area.
Politically, little is known about Aduku other than the fact that the governing body is a
village council headed by a chief. The exact size, powers and scope of the council are pieces of
information that will be particularly useful when designing a pilot grid in Aduku.
Considering the geographic location of Nigeria and the annual solar radiation to the country,
solar energy is one of the most attractive energy options to be promoted to improve the living
standards of Nigerian especially in rural area (Adurodija 1998). India is one of the countries that
has been very successful in implementing solar off-grid energy systems in the last decade. Mera
Gao Mirogrid Power (MGP) is a successful lighting company launching micro-grid solar energy
to provide rural lighting in India. The framework of MGP service is being used to design the
lighting service for Aduku community in Niger Delta. The primary objective of this paper is to
evaluate the feasibility of adapting the existing MGP solar microgrid lighting framework for
Aduku.
2
Methodology
To examine the feasibility of adapting the Indian solar microgrid lighting model in Aduku we
had to address the main questions as follow:
1- Is solar energy a potential energy source in Aduku, Niger Delta?
2- What are the technical aspects of Indian solar microgrid lighting model?
3- What technical modifications need to be considered to adapt the Indian model in Aduku?
4- What social factors in the community will affect the success of the project?
2.1 Solar potential
Aduku, our partner village, is located at N 5° 15' 58'' E 6° 17' 26'', 361 miles north of the
equator ("Aduku, Nigeria"). Given its close proximity to the equator, the community is in a
perfect location to take advantage of solar energy. The annual global horizontal solar radiation
for the Niger Delta is 4.5-5.0 kWh/m2/day ("MapSearch"). This measures the total amount of
shortwave radiation received from above by a surface horizontal to the ground. It is the
combination of direct normal (radiation that comes in a straight line from the sun) and diffuse
horizontal (radiation that does not arrive on a direct path from the sun) solar radiation. Most solar
radiation received on a clear day will be direct normal, while on a cloudy day most will be
diffuse horizontal. The annual direct normal solar radiation for the Niger Delta is less than 2
kWh/m2/day ("MapSearch"). This suggests that much of the radiation hitting the Niger Delta is
not coming in a straight line directly from the sun but instead passes through clouds or haze.
Table 1 - Solar Data for Yenagoa (Tukiainen)
Site-specific solar radiation data only existed for the city of Yenagoa, 23 miles south of
Aduku (Error! Reference source not found.). Its annual global horizontal radiation is 4.61
kWh/m2/day (averaged over 22 years). Monthly data reveals that radiation peaks at 5.69
kWh/m2/day in February and is lowest in July at 3.49 kWh/m2/day. This corresponds with the
region’s dry and rainy seasons. Average temperature for Yenagoa remains fairly constant
throughout the year, ranging from 75.85 to 79.05 °F. The clearness index for Yenagoa ranges
from 0.35 to 0.60. The index is the fraction of insolation at the top of the atmosphere that reaches
the surface of the earth (0 = very overcast and 1 = sunny). The range of daylight throughout the
year in Yenagoa is 11-13 hours (Tukiainen).
2.2 Modification of Indian Solar lighting Model for Aduku
The Indian microgrid model of our focus was designed and implemented by Mera Gao
Micro Grid power company (MGP). The main components of the Indian model are one PV
panel, two valve regulated lead acid (VRLA) batteries in series, one charge controller and circuit
breaker at each distribution line. This model provides enough electricity for 40 homes, which
powers 2-4 LEDs per home for 9 hours a day (Figure 4).
Figure 4 – Lay out and technical specification of Indian solar lighting components
The distribution line in Indian model uses 1.5 mm2 copper wires. The optimal length and
load of each distribution line in respect to distribution power loss or voltage drop is 100 m and
10 houses. The voltage drop of Indian model was calculated to be 5.7% (“Voltage Drop
Calculator”). The model in Aduku is suggested to start with 2 LED per house. The power per day
is same as Indian model, 9 hours per day. Table 2 shows the main specifications of Indian and
Aduku model.
Table 2 – Main characteristics of Indian model and Aduku model
Indian Model
PV panel
Batteries
Copper wire
LED per house
Daily power
Voltage drop
Houses to cover
Aduku Model
Specification
Quantity
Specification
Quantity
136 W
12 V, 72 Ah
1
2
200 W
12 V, 72 Ah
1
variable
1.5 mm2
100 m per
distribution line
4
9 hours
Per distribution line
40
variable
variable
1W
light
5.7%
Linear
2
9 hours
Per distribution line
86
1W
light
5.7%
cluster
The linear settlement of houses in Aduku limits the grid coverage to two distribution line
extending in opposite directions leaving the battery (Figure 5). Indian voltage drop of 5.7% per
distribution line was considered to be the fixed value in designing the microgrid model in Aduku.
To extend the grid coverage and yet comply with the optimal voltage drop the wire thickness
needs to be increased. These modifications were used as inputs in HOMER, a microgrid power
system analyzer, to optimize potential pilot microgrids in Aduku.
2.3 Community acceptability of the project
The Indian microgrid lighting model in rural area of India is structured as a profit-driven
business model. It is a well developed model and communities have become familiar with the
service since it was implemented. However, communities in the Niger Delta have not been
exposed to solar microgrid lighting. This project is one of the first attempts to introduce solar
lighting to rural communities in the Niger Delta. Also, the solar microgrid in Aduku is supposed
to be implemented as a social initiative and not a business model. Per our conversation with
Brian Shaad, the main reason of failure of the other development projects in Niger Delta was
because of lack of community ownership in operations and maintenance.
To increase the likelihood of a successful microgrid lighting project we suggest first
introducing a pilot model for the lighting service in the community. The level of acceptance in
the community and their willingness to own the solar lighting could be used as a guideline to
develop the social and technical aspects of a full-scale microgrid covering the entire village. For
instance, the number and location of the people who are willing to operate and maintain the
system could indicate the location and lay out of the microgrid model.
3
Results
The required wire size to comply with a voltage drop of about 5.7% for different distribution
lengths was calculated using an online voltage drop calculator (“Voltage Drop Calculator”). The
assumptions for this calculation are as follows:

Seventy homes are equally distributed along the 2 km road passing through Aduku.

The homes are connected to 24 V battery through the distribution line in parallel

Each home has 2 LED fixtures with total power of 2 W

The load current of each house is 1/12 A
The values input in the voltage drop calculator and the calculated wire size are shown in
Table 3.
Table 3 – Wire size for different length of distribution line to maintain the voltage drop about
Wire Length (m)
# Homes
Load current (A)
Wire size (mm2)
voltage drop
1000
35
2.9
85
4.9 %
500
17.5
1.5
21.4
5.4%
250
8.75
0.7
5.26
5.1%
100
10
0.8
2.08
5.6%
The price of copper wire is linearly proportional with the cross section of the wire. The cost of
distribution wiring for providing light for 70 households in a 2 km long segment of Aduku is
about 40 times the wiring cost in the Indian model.
3.1 Solar lighting pilot models
The components of pilot plans proposed in this section are similar to what is used in the
Indian model. Layout 1 covers 200m and provides light for about 16 homes (Figure 5). Layout 2
is designed to cover a longer distance of 400 m and 24 homes. To use the same wire size as
Indian model with a single PV panel, 2 more batteries were added to the model (Figure 6). The
choice of the layouts is based on the number of the homes which is planned to be included in the
pilot model.
Figure 5 – Lay out 1 covers average of 16 houses in 200 m.
Figure 6 - Lay out 2 covers average of 28 houses in 400 m.
3.2 HOMER cost analysis of pilots
The cost values of the components of the pilot models are in
Table 4
Table 4. HOMER analysis showed Layout 2 is 73% more expensive than Layout 1 for
covering twice homes than Layout 1. Another important outcome of HOMER analysis was the
percent capacity shortage or failure rate (Table 5). The capacity shortage of layout 2 is 30%
meaning this layout does not meet 30% of the load.
Table 4 – Cost of the components of the pilot model
Components
Specification
Unit cost
PV panel
Battery
LED module
Charge controller
Wiring
136 W
12 V, 72 Ah
12 V, 1 W
NA
Copper 1.5 mm2
$500
$180
$3
$100
$30/100 m
Fixed capital cost
Timer, circuit breaker, mounting
track. Unexpected costs
$900
Table 5 – HOMER analysis for pilot plans, Layout 1 and Layout 2
Lay-out
PV (W)
Battery
capacity
(Ah)
Capital
cost ($)
M&O ($/yr)
COE ($/kWh)
5 yr
5 yr
Capacity
shortage
1
136
72
1760
24
2.245
0%
2
136
72
2400
-12
2.34
30 %
3.2.1 Sensitivity analysis
Sensitivity analysis was conducted for both layouts. Battery rating, PV panel power, and system lifetime were considered
as variable values to do the sensitivity (Table 7 and Table 7). We assumed the cost of other rating of batteries and PV
panels are linearly proportional with their costs in Table 4
Table 4.
Table 6 – sensitivity analysis for pilot system, Layout 1
PV (W)
Battery
capacity (Ah)
100
100
100
136
136
136
40
60
72
40
60
72
Capital cost ($)
1,448
1,568
1628
1580
1700
1760
M&O($/yr)
COE ($/kWh)
5 yr
57
19
24
41
21
24
5 yr
2.21
3.62
3.63
2.13
2.15
2.25
10 yr
57
49
60
59
51
24
10 yr
2.21
2.24
2.31
3.5
3.52
3.58
Capacity
shortage
13 %
13 %
8%
3%
2%
0%
Table 7 – Sensitivity analysis for Layout 2
4
PV (W)
Battery
capacity (Ah)
Capital cost ($)
272
272
136
40
60
72
2540
2780
2400
M&O($/yr)
5 yr
27
-19
-12
10 yr
58
41
60
COE($/kWh)
5 yr
2.598
2.618
2.34
10 yr
1.53
1.556
2.043
Capacity
shortage
3%
2%
% 30
Discussion
4.1 HOMER
The HOMER model used to obtain these results is a modified version of the model
developed by the D-Lab group working on the optimization of the India grid. Major adjustments
to their final model included changing the solar resource data to the sun conditions in Aduku,
reducing the load of the system, and performing sensitivity analyses around battery size, panel
size and maximum acceptable capacity shortage (failure rate). Inputs such as the load profile,
number of LED fixtures per house, and battery specifications (other than size) were not changed.
The main result from the HOMER model is that compared to the current microgrid in India, a
microgrid designed for Aduku should be able to use smaller panels, smaller batteries, or both,
due to smaller loads that result from the linearity of the community. Whether or not both
components can be downsized depends on the maximum allowable failure rate that is specified.
The output from our HOMER model provides several important pieces of information to
think about when designing a microgrid for Aduku. First, because of the linear nature of Aduku,
only two distribution lines will be coming off of each battery group. The implication of this is
that a grid in Aduku can use a smaller battery than the 75 Ah batteries being used in India. We
found that running the HOMER model with a 40 Ah battery from the same company as the 75
Ah battery resulted in lower capital and levelized costs of both microgrid layouts without
increasing the failure rate of the grid.
Another area where the Aduku may be able to be downsized compared to the India grid is
the solar panel size. We specified three different sizes of panels in our model (with 272 W being
the largest of the three) and allowed HOMER to choose the panel that resulted in the lowest cost
while still meeting the performance level specified by the maximum allowable capacity shortage.
For the lowest failure rate of 5%, the microgrid requires one 136 W panel (same size as the India
grid). When the failure rate is relaxed to 15% or 25%, however, a 100 W panel can be used
instead (a more detailed sensitivity analysis showed the switching point to be around 12.5%).
None of the models that we ran required the use of a 272 W panel.
When considering pilot layouts, the sensitivity analysis conducted in HOMER provides
useful information with regard to the size of components needed and capacity shortage rate. The
optimal pilot layout will depend on the number of houses that would need to be covered. For a
small number of houses, Layout 1 can be used with both a smaller panel and smaller battery,
depending on the desired failure rate. If the number of houses to be covered is closer to 30, then
it would likely be more economical to use Layout 2 with a larger panel instead of two systems of
Layout 1.
4.2 Security concerns
The implementation of solar-powered lighting utility in Aduku will affect the kerosene
market in the area. If people shift away from kerosene, the people whose livelihoods depend on
supplying and distributing the fuel may feel threatened by the micro-grid. Steps will have to be
taken to ensure the microgrid components are protected from vandalization. This will be
especially important, as the PV array will likely be installed on a community building or
structure.
4.3 Construction
Most of the houses in Aduku are rentals and have thatched roofs that must be replaced
every 2-3 seasons. Landlords do not install more durable tin roofs because they want their
tenants to feel like they are in temporary housing. The tin roofs make the residence seem more
permanent to the tenants. The thatched roofs mean that a permanent array of PV panels cannot be
installed on homes in the village. The roof will not be strong enough to support the weight of the
panels. We are examining alternative structures that may be suitable for a PV array. There are a
number of structures constructed to shelter workspaces from the elements. According to our
partners, these structures are generally located in central locations surrounded by a dense cluster
of homes. However, in their current state, they are not rugged enough to support an array. One
option is to rebuild them so the structure supporting the PV panels also provides a benefit to the
village as a shelter.
Before a structure is built, it must be determined where panels should be located to
maximize exposure to the sun throughout the year. A site obstacle survey can provide the data
necessary to place the panels in area large enough to support the array with a clear field of view
of the sun’s path across the sky.
5
NEXT STEPS
5.1 ViPOR
The ViPOR (Village Power Optimization Model for Renewables) software suite is an
optimization model for designing village electrification systems. The National Renewable
Energy Laboratory (NREL) developed ViPOR in conjunction with HOMER. While HOMER
evaluates the economic and technical feasibility of a large number of technology options, ViPOR
uses spatial data to optimize the physical layout of the electrical distribution grid. Given a
detailed map of the village, ViPOR will determine which houses should be powered by isolated
power systems (like Smart Lights) and which should be included in a centralized distribution
grid. It does require the cost of generating electricity, which is modeled in a hybrid system
design tool like HOMER beforehand. The output displays a map of the optimal configuration
based on the spatial and economic data inputted in advance. The recommended configuration
will avoid difficult terrain, which adds to transmission costs.
We attempted to model Aduku within ViPOR but could not do it accurately because we
lacked a detailed map of the village. If the pilot phase is successful, obtaining precise spatial
information and modeling Aduku in ViPOR will determine which areas of the village are most
feasible for a centralized distribution grid and where isolated power systems should be used.
5.2 Charging Station
Charging the 12V batteries at large, centrally located PV array is an option if suitable
structures near the densely populated areas of the village cannot be found. Once the batteries are
charged, they would be carried to the midpoint of the micro-grid and plugged into the grid to
power the lights overnight. The next morning, the batteries would be brought back to array to be
recharged. It could also be implemented if the security of the panels is a problem. It would be
much easier to secure one large array than three or four small arrays. This type of system is
theoretically possible, but has not been modeled.
Potential issues with this configuration include managing the one or two people required
to move the batteries back and forth between the grid and array. Furthermore, the batteries and
their connections would need to be very robust to stand up to the repeated transport and
disconnection/reconnection to the grid and panels.
5.3 Cell Phone and Light Charging
If there is an interest in a cell phone charging service, a centrally located charging station
can be added to the grid. This station can also provide a place for residents of the village who
live outside the range of the grid to charge battery-powered lanterns and flashlights.
5.4 Hybrid Grid
Solar was the only electrical grid technology modeled with HOMER. An analysis of a
diesel or gasoline generator used in conjunction with a PV array could be conducted to determine
if costs can be reduced with a hybrid system. Gasoline and diesel are readily available in the oilrich Niger Delta. A small generator could reduce the number of batteries required by providing
extra capacity during peak hours or periods when the panels cannot fully recharge the batteries.
5.5 Detachable Lighting
Currently, the LED lights designated for use in the project are hardwired into the grid.
Research could be conducted to investigate the technical feasibility of a detachable LED light.
The light can be plugged into the grid to provide light within the home and charge its own
internal battery. If the customer ventures somewhere at night without lighting, they can detach
the light and use it as a flashlight. Furthermore, the internal battery would provide a backup for a
period of time if the grid were to fail.
6 Conclusion
Starting from a solar microgrid framework developed for a rural village in India, we
analyzed the technical modifications that would be required to implement a similar grid in
Aduku, Nigeria. Using HOMER software, we specified two potential layouts for pilot microgrids
and determined the components that are required for each of them. Due to the linear nature of
Aduku, we found that the number of connected households and the capacity shortage that is
deemed acceptable have an important impact on the optimal layout of the microgrid. Choosing
the appropriate sizes of components can reduce capital costs for a pilot microgrid.
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