In total 8 months were spent in Gogma by members of our research group, split at different moments during the last 3 years. This allowed us to perform 250 on-field observations. For each observation, the following elements were specified:
Is it something that was observed with the eyes or is it something that was said by someone. For the latter case, the name of the person was written down.
Day and time of the day.
The following key information were gathered through on-field observations:
Households do not need to pay to collect water at open wells.
Most of the inhabitants perceive the water at sealed boreholes (hand pumps and PVWPS) as potable and perceive the water at open wells as non-potable.
Inhabitants perceive water extraction at PVWPS as easy.
Most of the households collect water in the morning and in the evening but it seems that they collect more water in the evening than in the morning.
Inhabitants sometimes use their bike to carry water.
In the household surveys, inhabitants reported to use ~20 L/capita/day for personal hygiene. According to our on-field observations, we think that it is overestimated.
Inhabitants sometimes make several return journeys to collect water.
The GPS coordinates of the households, water sources and important locations in the village have been collected. We went to each location and used the mobile application “GPS Satellite” . The coordinates obtained are represented on the satellite picture in Figure II-10.
The geophysical study was realized by the Institut Superieur d’Application des Géosciences (ISAG) by using the very low-frequency electromagnetic method . Geophysical measurements were performed along 4 profiles of 150 m each, which corresponds to scanning a square of ~350×350 m. These profiles are represented in Figure II-10. Measurements along profiles 1, 2 and 4 did not suggest the presences of water along those profiles. On profile 3, there is a specific position that suggested the presence of water. It is at this position that the borehole for the current PVWPS was drilled.
Typically, performing measurements in a square of 350×350 m (i.e. 0.12 km2) takes half a day and costs ~$500. It would therefore be very costly and time consuming to perform geophysical measurements over an entire village of several square kilometres (e.g. Gogma has an area of 4 km2). In addition, it is important to have in mind that these geophysical measurements only provide information about the level of the top of the aquifer, which is not equal to the static water level in the borehole that will be drilled in the case of a confined aquifer . Besides, geophysical measurements do not provide information about the response of the water level in the borehole to water pumping nor about the water quality . This explains why geophysical measurements and groundwater exploration are performed only after the positioning of the PVWPS, i.e. after a position is proposed by the decision maker (see Figure II-6).
Account books of water sources
Account books of the 5 hand pumps and of the PVWPS were accessed by our research group. There is one account book for each hand pump and one account book for the PVWPS. The account book specifies which households go to this source and the cost to collect water at this source. We also remind that we determined that open wells are free of charge through on-field observations (section II.2.1). The cost for each source is given in Table II-3. The hand pumps numbers correspond to the ones presented in Figure II-10.
It is interesting to note that households have to pay annually for hand pumps and monthly for the PVWPS. In addition, we observe that the yearly amount paid for water at hand pumps and at the PVWPS does not depend on the quantity of water consumed.
Monitoring of the PVWPS of Gogma
The quantities measured in the frame of the monitoring of the PVWPS of Gogma are presented in Table II-6. In this table, the pump flow rate 𝑄𝑝 is the flow rate extracted from the borehole and is measured thanks to a flow meter set on PA1 (see Figure II-7). The consumption flow rate 𝑄𝑐 corresponds to the water collected by the inhabitants at the fountain. This flow rate is the amount of water retrieved from the water tank and is measured by setting up a flow meter on PA2.
Most of the quantities of Table II-6 have been collected since January 2018 thanks to a data logger that we developed. The data logger is powered by external PV modules (different from the ones of the PVWPS) and the recorded data are collected by using a USB stick. This data logger was conceived with the idea of minimizing its cost in order to encourage its use for monitoring other PV water pumping installations. The architecture and a picture of the data logger are shown in Figure II-13. The data logger permits to collect data with a time step of ~2.2 s and the recording rate is equal to the frequency of acquisition. In February 2019, an independent hydrostatic pressure sensor was added to measure the water level in the borehole 𝐻𝑏. The water level in the borehole is measured with a time step of 1 minute. For convenience, all the measured data were rescaled to an equally spaced temporal resolution of 1 min by nearest interpolation for this PhD thesis.
Table of contents :
List of figures
List of tables
Chapter I Literature review
I.1 The water-energy nexus in rural areas of sub-Saharan Africa
I.1.1 Domestic water access
I.1.2 Electricity access
I.2 Electrified water pumping technologies for off-grid areas
I.3 Conventional PVWPS design
I.4 Literature gaps and research objectives
Chapter II Experimental setup
II.1 Case study village and PVWPS
II.1.1 The village of Gogma, Burkina Faso
II.2 Data collection
II.2.1 On-field observations
II.2.2 GIS mapping
II.2.3 Geophysical measures
II.2.4 Account books of water sources
II.2.5 Household surveys
II.2.6 Pumping test
II.2.7 Water quality data
II.2.8 Monitoring of the PVWPS of Gogma
II.3 Partial conclusion
Chapter III Interdisciplinary model
III.2 Demand model
III.2.1 Determination of the water sources where the households wish to go after installation of the PVWPS
III.2.2 Determination of the water demand profile at the PVWPS
III.3 Technical model
III.3.1 Energy conversion model – presentation and application to the current PVWPS of Gogma
III.3.2 Energy conversion model – generalization
III.3.3 Beneficiaries identification model
III.4 Impact model
III.4.1 Indicators identification and ranking
III.4.2 Quantification of the indicators for each household
III.4.3 Socio-economic impact at the scale of the village
III.5 Economic model
III.6 Partial conclusion
Chapter IV Optimal design
IV.1 Optimisation problem
IV.2 Analysis of a reference result
IV.2.1 Mono-objective optimisations results
IV.2.2 Bi-objective optimisation results
IV.3 Influence of the error in the demand model output
IV.4 Influence of the expression of the socio-economic impact function
IV.5 Influence of the groundwater parameters
IV.6 Proposition of an improved procedure for the design and installation of PVWPS
IV.6.2 Case study
IV.7 Partial conclusion
List of Publications
Appendix A. Household survey
Appendix B. Motor-pump model polynomial coefficients – case of the SQFlex 5A-7
Appendix C. Satellite climatic data
Appendix D. Economic survey for local companies
Appendix E. Range of variation of groundwater parameters
Extended summary in French
Chapitre I : Revue de littérature
Chapitre II : Dispositif expérimental
Chapitre III : Modèle interdisciplinaire
Chapitre IV : Conception optimale