Solar Is Dead

Feasibility of Solar Power for Water Distribution in Adu Achi Nathaniel Hanna Holloway and Michelle Nahas

Abstract The Engineers Without Borders – USA, University of Illinois Urbana-Champaign Chapter has undertaken as project to supply water to the village of Adu Achi, Nigeria. This report presents the results of a feasibility study to determine if using solar power is the most economically viable option to power the pump for the water distribution system. After determining the power requirements for the system it was determined that solar would not be a viable option at an initial investment of close to $2 million. Problem Statement The village of Adu Achi is not connected to electric grid. Therefore, it is necessary to investigate other ways of producing the power necessary to power the pump for the water distribution system. Objectives The main objective of the solar team was to complete a feasibility study of solar energy as an option for powering the pump for the water distribution system, and compare results with the feasibility study performed by the Genset team. Completing this objective required several intermediate objectives. The first and most important was determining what equations were needed for the feasibility model. For these equations the relevant input parameters and data needed to be collected, creating other intermediate objectives. The equations and input parameters will be presented in the Method section of this

report. Another objective was to determine how to develop the model. This included looking into using HOMER, a software program developed by the National Renewable Energy Laboratory. Ultimately, Microsoft Excel was used to develop the feasibility model. Method The feasibility model incorporates a few basic equations and one major assumption. Before presenting the equations the assumption under which the system is designed to be operating should be presented: •

The system is designed to be operating as a “day use” system.

A “day use” system is a solar power system that does not include battery storage. A “day use” system was chosen for the design because of the extra cost of batteries (having to replace them every 5-10 years) and the decreased system efficiency with batteries. One important item to note is the results of this study are based on the worst case scenario. This means using the highest daily water demand and month with lowest solar irradiation (available solar energy), these being 800 m3/day and September respectively. The month of September has an average daily irradiation of 3.5 kWh/m2 or 3.5 peak sun hours (PSH) as can be seen in Figure 1 below. The optimal angle of inclination of the solar panel is 12 degrees from horizontal facing due south.

Average Daily Irradiation at 12 degree inclination 7 6

kWh/m^2/day

5 4 3 2 1 0 0

2

4

6

8

10

12

14

Month

Figure 1. Average Daily Irradiation for Adu Achi, Nigeriai

Equations The first equation necessary to developing the model is an equation that will determine how much power the motor that drives the pump will require. One important assumption to note is the neglect of headloss due to friction, as well as local headlosses, in the ∆p term. Neglect of headloss due to friction is a safe assumption because PVC pipe will be used for the borehole; PVC has a Hazen-Williams surface roughness coefficient of 0.0ii. The equation used is presented belowiii:

P=

Where: P = motor power required(Watts)

∆p = change in pressure (meters) Q = peak flow (l/min) e = pump efficiency (%)

∆p * Q *16.3 e

The peak flow term is calculated by the following equation:  1000l  Daily _ demand *   1m 3   Q=  60 s  PSH *    1hr  This equation gives the peak flow rate in liters per minute. The pressure term was determined by the following equation:

∆p = z2 − z1 Where: z2 = storage tank elevation (m) z1 = water table elevation , datum (m) Note: referred to as borehole depth in The amount of power required from the panels can be determined from the following equationiii: Solar _ array _ output = P * F Where: P= motor power (Watts) F = loss multiplier = 1.2 The cost for the Photovoltaic system was determined by using an estimation of $10/Wattiv. This cost estimation includes the entire system (panels, pump, wiring, inverters, etc.). Results As stated before the results of this feasibility study are for the critical conditions, being: highest daily demand and lowest average daily irradiation. Results for these are presented in Table 1 below:

Daily demand 800 m3/day Daily demand (m3/day)

800

Peak Sun Hours

3.5

Borehole depth (m)

150

Loss Multiplier

1.2

Peak flow (liters/min)

3,810

Pump efficiency (%)

60

Motor Power (Watts) Solar array output (Watts) PV system cost ($/W)

155,238

Initial PV Cost

186,286 10

$1,863,000

Table 1. Input Parameters, Power calculations and Cost calculations

Conclusions In conclusion, a stand alone solar power system would require a 155 kW motor with the entire system costing approximately $1,863,000. Upon inspection the cost is prohibitively high. With the results being what they are solar is not a viable option for the water distribution system. It would be nearly impossibly for EWB-UIUC to raise this amount of money in a timely fashion.

References

i

European Commission Joint Research Centre. “PVGIS: Solar Irradiation Data”. Accessed 5/18/2007. . ii

Hazen-Williams Coefficients. Accessed 5/18/2007. . iii

Green Empowerment. Solar Pumping System (SPS) – Introductory and Feasibility Guide. Accessed 5/18/2007. . iv

Personal Communication. Michel Maupoux. Green Empowerment.