Sizing and Design of Standalone PV Water Pumping System in Hargeisa/Somaliland: Case Study Abdirashid Aided Mohamed*, Numan S. Cetin*, Kivanc Basaran+ *
Institute of Solar Energy, Energy Technology, Ege University.
Ege University Campus 35100, Bornova – Izmir, Turkey.
[email protected] + Hasan Ferdi Turgutlu Faculty of Technology, Energy System Engineering, Celal Bayar University. CBU Hasan Ferdi Turgutlu Faculty of Technology 45040, Turgutlu – Manisa, Turkey.
[email protected] Abstract— Water is one of the basic needs for human, but its availability and the ability to access is difficult for rural areas in most of the developing countries including Somaliland, which is not only difficult for rural areas but also the water supply for Somaliland’s urban centres is difficult due to the lack of modern electricity grid. Somaliland is well endowed in wind and solar energy resources; it has one of the highest rates of daily total solar radiation in the world. Therefore, well designed and sized standalone PV water pumping systems are the best alternative solutions for remote areas and even urban centers in Somaliland for water requirements. This paper introduces the design of standalone PV water pumping system in Hargeisa to meet the needs of water for a small garden that uses 9m3 daily. First, we calculated the required amount of water for three autonomy days (27m3) also the total head including the head losses (104m) and from these findings, we determined the size of the pump set which was (4hp) and calculated the required energy of the system and the size of the PV. The PV area was 26.73m2 with the efficiency of 11.45% considering the other losses of the PV due to the dust, shading, temperature etc, and also the peak power was 4081Wp. Keywords—Photovoltaic, Water pumping systems, Somaliland/Hargeisa, Design and Sizing, Deep well.
1. INTRODUCTION The Republic of Somaliland lies in the Horn of Africa. It has borders with Djibouti to the west, Ethiopia to the south, and Somalia to the east with an area of 137,600 km2 (53,100 sq mi). It lies between Latitudes 8o and 11o27’’ North and Longitudes 42o35’ and 49o East [1]. It is one of the developing countries yet pays one of the highest tariffs on electricity ranging $0.8-$1.5/kWh [2]. This high price is due to the electricity being produced from the diesel generators and this diesel is imported from outside. Even though the price of the electricity is too high still most of the population doesn’t have access to the electricity which is mainly available in the cities and the towns, less than 20% of the population has access to the electricity [3]. Coming to the part of the energy 87 % of the total energy used in the country is produced from the
conventional ways i.e. biomass (charcoal) which caused massive deforestation that is a key factor to the regular droughts, water and food scarcity, climate change and many other environmental problems [4]. Somaliland due to its location it has a high potential of renewable energy resources including solar and the wind [5] which can address to this problem if it’s taken proper steps for solving it. In Somaliland, more than 55% of the population lives in the rural area [6] which has fewer infrastructures for basic needs and almost has no access to electricity. One of the most important things also basic needs in life is water but water is much more important in Somaliland especially the areas that are far away from the cities since most of the country is arid and semi-arid land with less than 500mm [6] 250mm of annual rain [7]. The water resources in Somaliland is limited to rainwater and deep underground water which needs too much energy to produce for the people to utilize in drinking, irrigation, livestock watering and other domestic uses. Since the energy to produce this water is very high and it’s impossible to use fuel dependent electricity. The utilization of PVWPS has a long history and recently especially last 15 years got considerable awareness among the researchers across the globe [8]. Many studies have been carried out including Omer [9] who conducted solar water pumping clean water for Sudan rural areas and he encouraged the use of PVWPS in Sudan, Belgacem [10] also did performance of submersible PV water pumping systems in Tunisia and he concluded that solar radiation intensity changes the overall efficiency and the pumping flow rate, but in Somaliland almost there are no such researchers and very few people are using PVWPS without the proper installations and studies. In this paper, we will study the possibility of using photovoltaic water pumping systems (PVWPS) in Somaliland. The Main objectives of this paper to introduce the utilization of SPVWPS in Somaliland by studying the solar energy potential in Hargeisa and conducting a case study for a garden in Hargeisa that needs water for irrigation, livestock watering, drinking and other domestic uses. First, we found the amount of water that was needed to designing the system, we assumed three autonomy
days and the amount of water was 27m3 as the daily use of the garden was 9m3. According to this amount of water and the climate and hydrological data of the site we calculated the water flow rate taken as Q in (m3/s) or (m3/hr), after finding Q we determined the energy demand ET in (kWh) required to be supplied to the motor for specific period of time considering the efficiency of the subsystem. And finally, we calculated the size of the PV generator and its area. SOLAR ENERGY POTENTIAL OF THE SITE (HARGEISA SOMALILAND) Hargeisa is the Capital and the largest city of Somaliland with population of almost 1.2 million with the coordinates of 9.562º N, 44.077º E. Due to the lack of strong government there are very few meteorological stations especially in airports which are very difficult to access their data, therefore, the solar irradiation information has been taken from PVGIS website [11] which shows that Somaliland has one of the best solar radiations in Africa if we look closely at the monthly solar irradiation for both irradiation on horizontal plane and irradiation on optimally inclined plane ( i.e. Hargeisa = 12º ), for the irradiation on optimally inclined plane of Hargeisa, the maximum irradiation is in the month of March with 7.71kWh/m2 and the minimum irradiation is in the month of July with 6.24kWh/m2 while the average daily solar radiation is 6.86kWh/m2, table 1.1 shows the information of monthly solar irradiation of the location and figure 1.1 shows global irradiation and solar electricity potential (optimally-inclined photovoltaic modules) of Somalia taken from the PVGIS website. The PVGIS database has been developed from solar radiation data estimated from the satellite using data and models from CMSAF representing the period 1996-2013.
suction point K= 0.5, pump inlet point K=1.5, discharge point K= 1.0 [13]. Therefore, the volume of water V (m3) in a tank that is required to supply the garden for three autonomy days can be determined by [16][17].
2.
Month G (kWh/m2/day) Month G (kWh/m2/day)
Jan 7.02 Jul 6.24
Feb 7.71 Aug 6.52
Mar 7.59 Sep 6.82
Apr 6.68 Oct 6.92
May 6.45 Nov 7.07
Jun 6.4 Dec 7.03
1.1 Irradiation on optimally inclined plane (kWh/m2/day)
3.
CASE STUDY ON HARGEISA
The typical borehole in Hargeisa is about 120m deep, while the static water level is 88m. The daily water requirement for the garden is 9m3 for irrigation, livestock watering, drinking and other domestic uses. In order to remove the requirement of the batteries in the system, we would use a tank to store the water for later use when the sun is not available during night and cloudy days. Table 1.2 shows the system parameters and its specifications including the average water required per day this value are taken from the owner of the garden and the depth of the well is known since it was already constructed but the pumping head was calculated considering the size of the pipe and the head losses etc. Components efficiency and factors: Inverter MPPT set efficiency is 98% [11], Motor-Pump set efficiency is 42% [13][14] , cable efficiency 98% [15], PV other losses 25% [15], K factors: straight pipe K= 0.02, pipe elbow K= 0.35,
Figure 1.1 Map of Somalia including Somaliland from PVGIS. Irradiation on Optimally Inclined Plane (kWh/m2/day) 10 8 6 4 2 0
Figure 1.2 Irradiation on optimally inclined plane (kWh/m2/day) Item
Parameter
Average water required per day
9m3
Well depth
120m
Pumping head
104m
Location
9.562⁰ N, 44.077⁰ E
Optimum inclination angle
12⁰
Autonomy period
3 days
Table 1.2 System Parameters and its specification
V
tank
9 m 3 3 27 m 3
Where Vtank is the Volume of tank or amount of the water required by community three autonomy days (litre or m3 per
day), after you determine the volume of the water that is needed and the pumping hours, then you calculate the water flow rate Q in (m3/s or m3/hour) using the number of sunlight hours in that location.
Q
.
Q
V and v t 27 6 . 24 60 60
v A .
.
tank
T
0 . 00121
3
m
/s
.
Q A
3
/ hr
2
LPF
5
.
2
5
2
.
LSP
2 2
8 . 51 m
.
4
80.001212 (2 0.35 + 1.0 + 0.5 + 1.5) 9.810.05 4 2
0.07 m
Therefore, the total dynamic head TDH is the sum of suction head HS, discharge head HD and total frictional head losses HL given by [18].
H H
TDH TDH
H H H where H h 7 88 8 . 58 103 . 58 104 m S
D
L
104
1 . 23 kW
Where Phyd= Hydraulic power delivered by the pump to water (kW) = Water density (kg/m3) g= Acceleration due to gravity (9.81m/s2) HTDH= Total dynamic head (m) Q= water flow rate (m3/s) The subsystem efficiency is given by
subsyst
mp
c
pcu
0 . 98 042 0 . 98 0 . 4034
Where subsystem = efficiency of the subsystem which consists of the following components’ efficiencies; pcu =efficiency of power condition Units and other electronics c = efficiency of Cables mp = efficiency of Motor-Pump set. 3.2. Total Energy Demand: The total energy ET (kWh) that needs to be supplied to the motor for the specific period of time t called specific pumping time is determined by
E
T
P
t
subsyst
TF
subsyst
1 . 23 6 . 24 0 . 4034
19
. 10 kWh
2
.
.
.
The figure 2 below shows the typical energy conversions in the PV water pumping system.
2
8Q h 4K 2vg k g.D
TDH
.
Where Q= Pumping rate (m3 /s) or (m3/hr), tT = number of sunlight hours or the total pumping time (hr) in order to increase the reliability of the system it’s good to take the month with the minimum irradiation, in this case, it’s the month of July with 6.24kWh/m2, v= velocity of water or liquid (m/s) and A= cross-section area of the pipe (m2). Now we will calculate the Total Dynamic Head (TDH), the total dynamic head TDH is the sum of suction head HSH, discharge head HDH and total frictional head losses HHL determined as shown below [17][18]. Where Suction head; is the height from suction point till pump and Discharge head; is the height from pump to storage inlet and frictional head losses are the losses due to the friction which is determined by the following equation.
8 LQ k h g .D 0 . 2 8 110 0 . 00121 9 . 81 0 . 05
gQH
1000 1000 9 . 81 0 . 00121 1000 hyd
.
4 . 33 m
or
P
L
LPF
h
3.3. Motor-Pump Sizing in kW and Hp 3.3.1. Motor-Pump Size in kW:
P 3.3.2.
t
P
m
mp
P
hyd mp
1 . 23 0 . 42
. .
Motor-Pump size in HP:
P
HP
P 0 . 745
t
.
2 . 94 0 . 745
2 . 94 kW
.
(1hp =0.745kW)
.
3 . 94 4 hp .
.
.
LSP
Where HL = total frictional head losses (m) HS = Suction head (m) HD = Discharge head (m) hLPF= Head loss for pipe fittings (m) hLSP= Head loss for straight pipe (m) 3.1. Determining Pump Energy Requirements The energy required to be supplied to the pump depends on the efficiency of both the motor and the pump. The power delivered by the pump to the fluid called hydraulic power which is required per day to supply volume V of water (m3) at total dynamic head HTDH is determined by [16][17].
3.4. PV Generator Sizing In order to determine the size of the PV generator, firstly it is important to determine the required PV area APV (m2) from the worst case minimum average monthly solar radiation, G (kWh/day), and the efficiency of the PV generator, PV using the following equations [19]. 3.4.1.
PV operating efficiency: PV
PV , u
. 0 . 1527 0 . 75 . 0 . 1145 o
Where PV,U = array efficiency at 1000 (W/m2) and 25 0C O = array efficiency due to other losses in PV (shading, dirty, temperature, etc).
3.4.2.
A
Area of the PV generator: PV
E G
subsyst
.
3.4.3.
PV
19 . 10 6 . 24 0 . 1145
.
PV
MPP
TDH
.
PV
subsyst
.
PV , u
[9] [10] [11] [12]
PV , u
G
.
PV 1000 A 1000 0 . 1527 26 . 73 4081 . 67 W MPP
2
.
.
PV generator Power:
gQH 1000
26 . 73 m
[13]
PV
.
P.
[14] [15]
3.4.4.
Number of Panels:
PV PV P V I 4081 . 67 16 . 32 17 Panels 250 N
PV
MPP
MPP
MPP
[16]
MPP
MPP
.
.
[17]
.
[18]
4. CONCLUSION The high potential in Somaliland due to its location, the excellent sunshine and having long coastal area 740km with the majority along the Gulf of Aden are influencing the energy requirements in Somaliland. In this paper, we can conclude that according to all the above-mentioned reasons, Somaliland should increase the use of PV Water Pumping Systems in order to reduce the water crises and scarcity that the country has. Since it’s the only visible solution to the problem it’s advised that Somaliland government should encourage the use and enhancement of these systems. REFERENCES [1] [2] [3] [4] [5] [6]
[7]
[8]
(2016) The Somaliland government website. [Online]. Available: http://www. http://somalilandgov.com/somaliland-geography/ Jami Nelson Nuñez, “a Research Report on Powering Progress: The Potential of Renewable Energy in Somalia” 2015, p.07, http://shuraako.org/publications/somalia-renewable-energy IEA, “African Energy Outlook 2014 report” https://www.iea.org/publications/freepublications/publication/WEO201 4_AfricaEnergyOutlook.pdf Istanbul conference on Somalia 21 – 23 May 2010 “Alternative Energy” http://www.sorenergy.com/wpcontent/uploads/2015/03/energy_somalia.pdf Pallabazzer R, Gabow AA. Wind generator potentiality in Somalia. Renewable, Energy 1992;2:353–61. Water Infrastructure Development for Resilience in Somaliland Program 2016 http://www.afdb.org/fileadmin/uploads/afdb/Documents/Environmenta l-and-Social-Assessments/Somaliland__Water_infrastructure_development_for_resilience_in_Somaliland_pro gram_%E2%80%93_ESMF_Summary.pdf Appraisal Report on “Building Resilience To Water Stress In Somaliland “Preparation of Water Resources Management and Investment Plan” http://www.afdb.org/fileadmin/uploads/afdb/Documents/EvaluationReports-_Shared-With-OPEV_/Somalia-Approved-Appraisal_Report__Building_Resilience_water_stress_Somaliland_-_10_2014.pdf S.S. Chandel, M. Nagaraju Naik, R. Chandel, 2015,‘Review of Solar Photovoltaic Water Pumping System Technology for Irrigation and
[19]
Community Drinking Water Supplies’, Renewable and Sustainable Energy Reviews 49 (2015) 1084-1099, ScienceDirect. Abdeen Mustafa Omer, 2001, ‘Solar water pumping clean water for Sudan rural areas’, Renewable Energy 24 (2001) 245-258, ScienceDirect. Ben Ghanem Belgacem, ‘Performance of Submersible PV Water Pumping Systems in Tunisia’, Energy for Sustainable Development (2016) The PVGIS website www.pvgis.com [Online]. Available: Vimal Chand Sontake, Vilas R. Kalamkar, 2016 ‘Solar Photovoltaic Water Pumping System - A Comprehensive Review’, Renewable and Sustainable Energy Reviews 59 (2016) 1038-1067, ScienceDirect Paul Mac Berthouex, Linfield C. Brown , 2015, ‘Pollution Prevention and Control: Part II Material and Energy Balances’. pp 257-265, www.bookboon.com Tuma Nocchi Pentair Water, Electric Pumps Catalogue Mahmoud M, Ibrik I. Techno-economic feasibility of energy supply of remote villages in Palestine by PV-systems, diesel generators and electric grid. Renewable and Sustainable Energy Reviews 2006;10:128–38. Tamer Khatib, 2010, ‘Design of Photovoltaic Water Pumping Systems at Minimum Cost for Palestine: A Review’, Journal of Applied Sciences 10 (22): 2773-2784, 2010 ISSN 1812-5654. K.G. Mansaray, 2014,‘Optimum Design of Solar Photovoltaic Pumping Systems by Computer Simulation’, International Journal of Emerging Technology and Advanced Engineering, www.ijetae.com (ISSN 2250-2459, ISO 9001: 2008 Certified Journal, Volume 4, Issue 9, September 2014). Abdelmalek Molceddem, Abdelhamid Midoun, D.Kadri, Said Hiadsi, Iftikhar A. Raja, 2011, ‘ Performance of a Directly-Coupled PV water Pumping System’, Energy Conversion and Management 52 (2011) 3089-3095, ScienceDirect. M. Benghanem, A. Hadj Arab, 2007, ‘ Photovoltaic Water Pumping Systems for Algeria’, Desalination 209 (2007) 50-57. ScienceDirect.
