D-Lab I Final Report: Adapting a Solar Microgrid to Provide Lighting in Rural NigeriaJon Cook, Laleh Rastegarzadeh, and Daniel SheeterPrepared for D-Lab, UC DavisFeb. 14, 2011IntroductionFor 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.Modification of Indian Solar lighting Model for AdukuThe Indianmicrogrid 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 powers2-4 LEDs per home for 9 hours a day (Figure 4).

Figure 5 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 2shows the main specifications of Indian and Aduku model.

Table 2 Main characteristics of Indian model and Aduku modelIndian ModelAduku Model

SpecificationQuantitySpecificationQuantity

PV panel136 W1200 W1

Batteries12 V, 72 Ah212 V, 72 Ahvariable

Copper wire1.5 mm2100 m per distribution linevariablevariable

LED per house1 W41 W2

Daily powerlight9 hourslight9 hours

Voltage drop 5.7%Per distribution line5.7%Per distribution line

Houses to covercluster40Linear86

ResultsThe 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 Theload current of each house is 1/12 AThe values input in the voltage drop calculator and the calculated wire size are shown inTable 3.

Table 3 Wire size for different length of distribution line to maintain the voltage drop about Wire Length (m)# HomesLoad current (A)Wire size (mm2)voltage drop

1000352.9854.9 %

50017.51.521.45.4%

2508.750.75.26 5.1%

100100.82.08 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 70households in a 2 km long segment of Aduku is about 40 times the wiring cost in the Indian model. Solar lighting pilot modelsThe 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 6 Lay out 1 covers average of 16 houses in 200 m.

Figure 7 - Lay out 2 covers average of 28 houses in 400 m.

HOMER cost analysis of pilotsThe cost values of the components of the pilot models are in 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 modelComponentsSpecification Unit cost

PV panel136 W$500

Battery12 V, 72 Ah$180

LED module12 V, 1 W$3

Charge controllerNA$100

WiringCopper 1.5 mm2$30/100 m

Fixed capital costTimer, circuit breaker, mounting track. Unexpected costs$900

Table 5 HOMER analysis for pilot plans, Layout 1 and Layout 2Lay-outPV (W)Battery capacity (Ah)Capital cost ($)M&O ($/yr)COE($/kWh)Capacity shortage

5 yr5 yr

1136721760242.2450%

2136722400-122.3430 %

Sensitivity analysisSensitivity analysis was conducted for both layouts. Battery rating, PV panel power, and system lifetime were considered as variable values to do the sensitivity(Table 6 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 6 sensitivity analysis for pilot system, Layout 1PV (W)Battery capacity (Ah)Capital cost ($)M&O($/yr)COE ($/kWh)Capacity shortage

5 yr10 yr5 yr10 yr

100401,44857572.212.2113 %

100601,56819493.622.2413 %

10072162824603.632.318 %

13640158041592.133.53 %

13660170021512.153.522 %

13672176024242.253.580 %

Table 7 Sensitivity analysis for Layout 2PV (W)Battery capacity (Ah)Capital cost ($)M&O($/yr)COE($/kWh)Capacity shortage

5 yr10 yr5 yr10 yr

27240254027582.5981.533 %

272602780-19412.6181.5562 %

136722400-12602.342.043% 30

DiscussionHOMER 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 1.0. Security concernsThe 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. ConstructionMost 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 suns path across the sky.NEXT STEPSViPORThe 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 ViPORin 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.Charging StationCharging 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. Cell Phone and Light ChargingIf 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. Hybrid GridSolar 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 oil-rich 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. Detachable LightingCurrently, 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.

ConclusionStarting 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.

BibliographyAdurodijaa, F.O., I.O. Asiab and M. A. C. Chendoc. The Market Potential of PhotovoltaicSystems in Nigeria.Solar Energy. 64.4 (61) (1998): 133-139."Aduku, Nigeria." GeoNames. 2011. Web. 14 Feb. 2011. .Aduku in Brief. Feb. 2011. PowerPoint presentation."Bayelsa State." Welcome to Bayelsa State. Web. 14 Mar. 2011..Fadare, D.A. "Modelling of Solar Energy Potential in Nigeria Using an Artificial Neural Network Model." Applied Energy 86.9 (2009): 1410-422. Print.Google Earth. Computer software. Vers. 5.2. Google Inc., 2011. Web. 14 Feb. 2011.Interviews with Brian Shaad and Bryan Pon, Feb 6 and 8, 2011.Jaisinghani, Nikhil. "Sites." Mera Gao Micro Grid Power. VDI, 3 Jan. 2011. Web. 14 Feb. 2011. ."MapSearch." National Renewable Energy Laboratory (NREL). U.S. Department of Energy, 2005. Web. 14 Feb. 2011. .Mera Gao Micro Grid Power. An Innovative Rural Lighting Solution for India. PowerPoin Presentation.Niger Delta Human Development Report, 2006, United Nations Development ProgrammeOfficial Portal of Bayelsa State . Web. 11 Feb. 2011< http://www.bayelsa.gov.ng/about-us.html>Reysa, Gary. "Solar Site Survey." BuildItSolar. 2 May 2006. Web. 14 Feb. 2011. .Tukiainen, Matti. "Sun Data." Gaisma. 2011. Web. 14 Feb. 2011. .UNDP, 2006. Print Fawundu, Alfred A. Niger Delta Human Development Report. Rep. Garki."Voltage Drop Calculator." NoOutage Home. Web. 14 Feb. 2011.. Usman, Shamsuddeen. Niger Delta Human Development Report, 2006, United NationsDevelopment Programme