Baseline of the Use of Solar Irrigation Pump in the Niayes Area in Senegal

Solar irrigation pumps are considered as an alternative to the use of diesel and electric pumps due to the high cost of energy. These pumps are now in-creasingly used in the Niayes area. Thus, a more in-depth knowledge about the components of a solar pumping system and their characteristics available on the market as well as prices can be beneficial. This study was conducted to have an idea on the baseline of the use of solar irrigation pumps in this area. To perform this study, surveys were conducted among 12 suppliers and 10 service providers located in Dakar, Thies, Louga and Saint-Louis region and among 53 users located in Potou area which is in Louga region. Results show a wide range of pump brands and characteristics. Brands found were Lorentz, LIKOU, SHIMGE, Grundfos, Solar pump, Feili, Difful, JUQIANG, Solar tech, and Asaman. The pumps’ flow rate varies between 2.5 m 3 /h and 45 m 3 /h, the pressure ranges from 15 m to 160 m and the power is between 0.072 kW and 10 kW. The price of these pumps varies depending on the brand used and their characteristics. in general do not perform pump maintenance due to a lack of knowledge and financial means. Thus, according to farmers, factors that impact pumps operation are the low sunshine that occurs between December and January and the iron in the water and low well discharge.


Introduction
Water and energy consumption for irrigation is very important. Traditionally, electricity and fuel have been the main sources of energy used in pumping for irrigation in remote areas [1]. However, the inaccessibility of electricity and the high cost of diesel negatively impact on irrigation. Therefore, the use of solar energy in pumping water is considered a promising alternative to conventional energy [2]. Many developing countries are quickly adopting solar irrigation pumps [3].
During the last decade, a steady growth of solar energy has occurred in the world as an environmentally friendly and renewable energy resource. In fact, developed nations such as Germany, Spain, Italy, etc., and the United States of America are the main contributors to the success of solar energy. In recent years, solar photovoltaic industry development has outpaced all other renewable energy sources in the world. Nevertheless, solar photovoltaics in many developed counties is a recognized and realizable technology, while it is practically absent in African countries [4]. The use of solar irrigation pumps is considered a viable option for both large and small farmers due to lower investment costs and the increasing application of subsidy programs. Indeed, the use of solar pumps is possible in both large-scale and small-scale decentralized irrigation systems. Increasing demands for implementation, financing, and training from agricultural institutions in developing countries reflect the growing interest in solar-powered irrigation solutions worldwide [5]. Solar irrigation pumps are competitive with conventional power generation with significant recently photovoltaic cost reductions [6]. The cost of solar panels is continuously decreasing leading to their use in different sectors, namely the agricultural sector. For instance, the solar powered irrigation system is an appropriate alternative for farmers in given the present situation of energy crisis [7].
In the Niayes area in Senegal particularly, solar pumping is perceived as a very prospective solution enabling farmers to reduce their production costs. Currently, surface gasoline-powered pumps operating at a depth of up to 10 meters are practically used for groundwater pumping in irrigation besides hand pumps. In this regard, this area is considered one of the most potential areas for testing solar-powered pumping for intermediate irrigation depths for smallholders [8]. Also, solar irrigation pumps are becoming used by these farmers but without any prior study. For this purpose, it is important to assess the baseline of using solar irrigation pumps in the Niayes area in order to identify both the current status of the use of these pumps as well as the constraints to their implementation.

Study Area
The Niayes area is located in the north-west of Senegal, located between latitudes 14˚55' and 15˚27' and longitudes 16˚50' and 17˚07' west. It consists of a coastal narrow strip of 183 km long. It is part of the four regions: Dakar the capital of Senegal, Thies, Louga, and Saint-Louis ( Figure 1) and bordering on the northern maritime fringe between Dakar and Saint-Louis [9].

Data Collection and Method
Surveys were conducted in order to collect data related to the equipment, characteristics and the cost of the different components, the cost of installation and maintenance and the constraint regarding the use of solar pumping systems Surveys were conducted between December 2, 2019, and January 30, 2020 at three levels: 1) suppliers of solar irrigation pumps, 2) service providers that installed solar pumps in the Niayes area and 3) user located in Potou area in Louga region.

Suppliers
Surveys with suppliers were carried out with 12 suppliers in three region: Daker, Saint-Louis, Thies. Questionnaires were developed to get information about the components of a solar pumping system, the cost of each component, the brands of pumps existing on the market, the characteristics of these pumps (flow rate, pressure head, and power), etc. Realizing that suppliers of solar irrigation pumps are not very numerous. In total, 73 solar irrigation pumps were studied for 11 different brands.

Service Providers
Interviews were performed with 10 service providers in Saint-Louis, Dakar, Thies, Louga regions. These questionnaires were developed in order to find out the brands and characteristics (flow, pressure head, and power) of pumps that are installed in the Niayes area. 57 pumps models distributed over nine (9) brands were the subject of this study following the investigations.

Users
Potou area was selected to conduct the surveys with users. Potou is an area in which we find drip, sprinkler and manual irrigation systems. To carry out this study, a meeting was made with farmers using solar irrigation pumps in this area. It was conducted in order to identify the users of solar irrigation pumps, irrigation techniques used by each farmer and irrigation water distribution system at plot level (reservoir use or not). Following this meeting, sixty-five (65) farmers were identified in ten (10) separate villages in Potou area. The process followed to performed investigation with users is summarized in Figure 2.
Sampling was performed using Giezendanner's (2012) formula after identifying farmers having solar irrigation pumps in Potou area. Thus, the sample size was determined using the Equation (1).
n is the sample size, N is the population size, є is the margin of error, estimated at 5% with a confidence interval of 95%, and t is the confidence margin estimated at 1.69 and deducted from the Confidence interval.
After calculation, the sample size was estimated at 53 farmers. Knowing the sample size, it was necessary to determine the sampling rate, which was calcu-    R is the sampling rate, n is the sample size, and N is the population size. Table 1 gives the number of user of solar irrigation pumps in the Potou area and the number of farmer selected by using the sampling rate. Each farmer was selected randomly in the ten (10) villagers.  [8] which showed that the majority of pumps on the market are of Chinese origin.

Characteristics of Solar Irrigation Pumps Available on the Market
The pumps existing in the market have different characteristics. They vary from one pump to another and from one brand to another. These characteristics are flow rate, pressure head, and power.  2) Pumps pressure   3) Pumps power Figure 6 shows that the pump power is divided into six (6) categories: a) less than 1 kW, b) from 1 to 2 kW, c) from 2 to 3 kW, d) from 3 to 4 kW, e) from 4 to 5 kW and more than 5 kW. That is explained by the fact that these pumps have more or less low flow rates and pressures (86.8% have flow rates less than or equal to 15 m 3 /h and 82.2% have pressures less than or equal to 95 m). As a result, the power of these pumps is sufficient for water pumping.   Lorentz pumps compared to the other brands. This is due to the fact that Lorentz pumps have higher flow rates and power ratings. In addition, according to the suppliers, the service life of Lorentz brand pumps is higher, up to 10 years or more. In addition, prices are lower for some SHIMGE, Solar Pump and JUQIANG pumps. This is because these pumps have low flow rates, pressures as well as powers and are not equipped with controllers. Also, the high cost of Grundfos brand is due to their high-pressure head.

Relationship between Flow, Pressure and Power
In addition, a comparative study between the prices of the pumps available from suppliers with whom these surveys were conducted and the prices of these pumps in the e-commerce sites showed that the prices of the pumps are higher

1) Panels
The solar panels that exist on the market are either made of monocrystalline sillicum or polycrystalline sillicum. These modules exist under a wide range of power (Table 2).  show that the cost of solar panels is lower in shops compared to companies.

Pump Warranty Period
The warranty period of the pumps differs according to the brand and the capac-

After-Sales Service
The maintenance of the solar pumping system is not carried out by all suppliers.
In fact, only 67% of the suppliers carry out maintenance after the sale (Figure 9).
The after-sales service is mainly carried out by the companies that sell and install the solar pumping system. It is free of charge during the warranty years.
However, after these years, the farmers will be required to pay for the maintenance. Moreover, shops only provide equipment for sale and do not take care of after-sales maintenance. However, they are often working with designers who can perform maintenance of the pumping system after installation.

Pumps Installed by Service Providers
In the Niayes area, solar irrigation pumps are installed by companies that sell    [11]. According them, polycrystalline panels are not very sensitive to variations in illumination, which is not the case with monocrystalline silicon panels.
Thus, panels made from polycrystalline silicon are more recommended for areas with high levels of sunlight because they are designed to be unheated.

Installation Cost and Maintenance 1) Installation cost
The cost of pump installation in the Niayes area is quite variable for the dif-  (Table 3).
The installation cost of the most commonly implemented solar irrigation pumps in the Niayes area varies between 76.23 euros and 1219.59 euros. According to the service providers, the cost of installing a solar pumping system depends on the environmental conditions in which the pump will be installed, the size of the pump, the number of panels that will be installed, and the accessibility of the area. The highest installation cost is obtained from Lorentz brand. • disassemble and repair the pump in case of failure; • inspection of the connection network; • checking the voltage and the solar panels.
According to the service providers, maintenance is performed at the end of each crop season if water quality is suitable. However, it is carried out every 4 to 2 months when the well water is charged.

Evaluation of the Investment Cost for Solar Pumping System Installation by Suppliers
The investment cost of a solar irrigation pumping system can be determined based on prices provided by companies. Indeed, 50% of the suppliers of solar Considering Lorentz brand, which is installed by 80% of the companies and which costs more, it has been found that the investment cost of solar irrigation pumps varies between 2286.74 euros (1,500,000 CFA) and 25,086.89 euros (16,455,919 CFA). Among these pumps, the most installed in the Niayes area are the PS600, PS1800, and PS4000. PS600 pumps have flow rates of up to 12 m 3 /h and are generally used in areas of 0.5 to 1 ha. PS1800 pumps have flow rates of up to 15 m 3 /h and are used on areas of 1 to 2 ha. PS4000 pumps have flow rates of up to 24 m 3 /h and are generally used on surfaces of more than 2 ha. The price of the PS600 is fixed for all companies. It is estimated at 3811.24 euros. However, the investment cost of the PS1800 and PS4000 varies from one company to another. The investment cost of the PS1800 pumps varies between 5457.67 euros and 5640.61 euros. Investment costs for PS1800 pumps are very close in the different companies. However, the difference in costs is significant for PS4000 pumps. The investment cost of PS4000 pumps ranges from 6402.86 euros to 11,078.47 euros. The variation in price is mainly due to the difference in the number and power of panels, the diameter of the piping, as well as the type of cabling used during installation. In addition, the change in investment cost is related to the expensive cost of customs clearance for some of them, which has an impact on prices. In addition, the investment cost to implement Feili pumps varies between 1920.86 Euros (1,260,000 CFA) and 8384.70 Euros (5,500,000). That of JUQIANG brand ranges from 640.29 Euros (420,000 CFA) to 3018.49 Euros (1,980,000 CFA). For CNP brand pumps, the cost of installation is either equal to 4344.80 Euros (2,850,000 CFA) or 5267.11 Euros (3,455,000 CFA) or equal to 6494.33 Euros (4,260,000). Difful pumps cost 1631.20 Euros (1,070,000 CFA), 2667.86 Euros (1,750,000 CFA) or 3430.10 Euros (2,250,000 CFA). The investment cost for the installation of solar irrigation pumps is cheaper for Difful and JUQIANG brand pumps. This is due to the fact that Difful pumps are generally low power pumps (0.75 kW to 1 kW) that are installed with 4 to 6 panels. Also, JUQIANG pumps are small pumps with low flow rates of 3 m 3 /h to 6.5 m 3 /h.  (Table 4). Also, Grundfos brand pumps used by farmers in Gabar village were installed in a test project, which meant that farmers received them free of charge.   polycrystalline silicon have power ratings of 250 to 300 W. In fact, the rarity of using amorphous panels can be explained by the fact that the price of polycrystalline panels is very profitable, and its output is higher than that of amorphous panels. This efficiency is estimated at 15% for polycrystalline crystals and 7% for amorphous crystals [12].

Use of Solar Pump by Farmers in Potou Area
In addition, for the most part, farmers remain unaware of the unit prices of However, despite this, farmers consider that the use of solar irrigation pumps is more economical compared to the use of diesel pumps which were mainly used.
In fact, they estimate that each year on average 1986.18 euros (1,302,847 CFA) are spent with regard to diesel used for irrigation on an average area of 1.3 ha for a season with an average duration of 8 months. Thus, they are no longer dependent on fuel with the solar-powered irrigation pumps.
Moreover, knowing the significant contribution of the Niayes area in Senegalese agriculture, the government can make an effort to subsidize farmers in this area. These subsidies will allow them to easily access to solar-powered irrigation pumps. Therefore, this could allow the development of irrigated agriculture in the Niaye zone and shift production in the direction of self-sufficiency.

Performance of Solar of Solar Irrigation Pumps in the Niayes Area
According to farmers, solar irrigation pumps are very efficient and thus allow farmers to meet crop irrigation water requirements. In fact, 84% of the pumps operate between 8 am and 6 pm, which corresponds to an operating time of 10 hours. Thus, for 68% of the farmers, the flow rate of solar irrigation pumps varies from one period to another during the year.
The results of the surveys show that the peak period of solar irrigation pump flow is between May and April. However, the flow rate of solar irrigation pumps is lower between December and February. This is due to the variation in sunshine during the year. In Saint-Louis region, the lowest average daily irradiation values range from 4.72 to 4.97 kWh/m 2 /day. They are recorded between January and December. On the other hand, the maximum average daily irradiation values vary between 6.28 and 7.27 kWh/m 2 /day and occur between March and July (RETScreen Expert). Indeed, in a solar pumping system, the electrical energy used to operate the pump is generated by the photovoltaic panels. The production of electricity in a solar system occurs at the level of the solar photovoltaic cells [3], which directly convert sunlight into electricity through the semiconductor material [13]. The PV panels are connected to a motor (DC or AC) that converts the electrical energy supplied by the PV panel into mechanical energy which is converted into hydraulic energy by the pump [2]. This result confirms that of [14] which shows that the direct current produced by solar photovoltaic cells is a function of the total incident solar irradiation.

3) Maintenance of solar irrigation pumps
The maintenance of solar pumping systems is not always carried out by farmers. Indeed, the solar panels are flooded every two or three days and even every day during dusty periods. However, not all pumps are maintained as such by farmers.
The results show that in the Potou area, 70% of farmers do not perform pump maintenance. In this case, pumps are only repaired when there is a failure.
Pumps are repaired free of charge by the company that installed them if failure occurs during the warranty period, which varies from 1 to 5 years depending on the company. After the warranty period, farmers usually employ electricians or technicians to repair the pump. However, only 30% of farmers perform pump maintenance after installation. Maintenance is carried out every 2 to 4 months for the most part. But for other farmers the maintenance is done once a year.
Maintenance is mainly carried out by the companies that installed the pumps.
Farmers who benefit from maintenance are always under warranty. Also, it was observed that some farmers perform pump maintenance themselves. In this case, In addition, for 96% of farmers, training on pump maintenance would be appreciated. Indeed, training will enable them to better maintain the pumps to avoid breakdowns. Also, it will allow them to avoid damage that is often caused by the time that companies take to come for pump reparation.

Conclusion
This study focused on the baseline of the use of solar irrigation pumps in the Niayes area. Surveys were conducted among twelve (12) suppliers and ten (10) service providers located in Dakar, Saint-Louis, Thies, and Louga regions and also among users of solar irrigation pumps located in ten (10)  ros/year. In order to farmers, it be would be interesting to carry out a more in-depth study on the technical and economic feasibility of using solar energy in irrigation in the Niayes region.