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Techno-economic feasibility of off-grid solar irrigation for a rice paddy in Guilan province in Iran: A case study
Solar Energy 150 (2017) 546–557
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Techno-economic feasibility of off-grid solar irrigation for a rice paddy in Guilan province in Iran: A case study Mehdi Niajalili a, Peyman Mayeli b,⇑, Mohammad Naghashzadegan c, Amin Haghighi Poshtiri c a
Department of Mechanical Engineering, Kadous Institute of Technology and Higher Education, Rasht, Iran Young Researchers and Elite Club, Lahijan Branch, Islamic Azad University, Lahijan, Iran c Department of Mechanical Engineering, Guilan University, P.O. Box 3756, Rasht, Iran b
a r t i c l e
i n f o
Article history: Received 23 January 2017 Received in revised form 20 April 2017 Accepted 4 May 2017
Keywords: PV pumping system Irrigation Global irradiance Lifecycle cost Clearness index Solar panel
a b s t r a c t In this study, a typical rice paddy in Guilan province of Iran is considered and the technical and economical feasibility of the solar powered pumping system is studied. The monthly mean daily solar irradiance has been studied for this area and the measured data is compared with European Photovoltaic Geographic Information System (EU PVGIS) model for Middle East, including Iran. The investigations imply that the average monthly mean daily solar irradiance in irrigation months are reported equal to 5.92 kW h/m2/day by Guilan Meteorological Administration and 5.95 kW h/m2/day by EU PVGIS. A mean monthly clearness index from 0.54 to 0.57, in irrigation period, gives Guilan province a good potential to employ photovoltaic (PV) pumping system. In this study, the appropriate size of the PV panels and the lifecycle cost estimation of PV pumping system in comparison with conventional systems are presented. Also, the area of the PV solar panel to supply required power of the pumping system for a rice paddy with specified area is calculated. Results show that though the initial outlay of the PV system is about 9 times of the conventional systems but the total lifecycle costs of the PV pumping system is just 65.6% costs of the conventional pumping system. Also in spite of high initial costs of the PV pumping system, it is found that after around 9 years, the total costs of both systems would be equal to conventional one i.e. gasoline pumping system and after this time, the costs of the conventional pumping system will exceed the PV solar panel system. Ó 2017 Elsevier Ltd. All rights reserved.
1. Introduction The idea of using the sustainable solar energy by means of photovoltaic (PV) cells for irrigation and water pumping is a modern and well-accepted one. Many developing countries are using PV systems as a source of energy at least in remote areas (Zabihi et al., 1998; Al-Karaghouli and Al-Sabounchi, 2000; Diarra and Akuffo, 2002; Mahmoud and el Nather, 2003; Firatoglu and Yesilata, 2004; Ramos and Ramos, 2009; Bouzidi, 2011). The main problem of using PV in Iran and other developing countries is the initial cost of these systems. Because of both falling costs of the PV cells (Raugei and Frankl, 2009) and price fluctuations of the fossil fuels, the general tendency toward the employing solar energy systems is increased. It means that using PV as a source of green and sustainable energy can have economic reasons. Like other uses of PVs in industry, here, to irrigate a typical field, estimation of the ⇑ Corresponding author at: Islamic Azad University, Lahijan Branch, University Blvd, P.O. Box: 41438-57986, Lahijan, Guilan, Iran. E-mail address: [email protected] (P. Mayeli). http://dx.doi.org/10.1016/j.solener.2017.05.012 0038-092X/Ó 2017 Elsevier Ltd. All rights reserved.
required array area is an important part of design process. Hamidat et al. (2003) studied the Sahara regions; an area of high level of monthly average solar radiation. They considered several crops, say, wheat, potato, tomato and sunflower. It was found that the PV water pumping system could easily cover the daily water need rates for small-scale irrigation with an area smaller than two hectares. Cuadros et al. (2004) studied a procedure to estimate the required dimension of a PV installation designed to power a pumping system for the drip irrigation of an olive tree orchard in southwest Spain. They divided their work into three different parts: first, determination of the soil and climate characteristics of the considered land, second, a hydraulic analysis of the pumping system and finally calculating-measuring the peak photovoltaic power required for irrigation. As it was remarked earlier, PV powered pumping is a tempting and modern way to use the available solar irradiance, so lots of countries are trying to examine the feasibility of the PV pumping system (PVPS) for irrigation or even for pumping clean water. Kelley et al. (2010) presented a comprehensive study on the feasibility of solar-powered irrigation. They showed that two main
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Nomenclature APV ACG ACGnet ACP ACPnet A0 CPWF ECPWF EFR DP d ET0 ETc g h Ip
area of PV panels (m2) annual cost of gasoline pumping system ($) net annual cost of gasoline pumping system after n year ($) annual cost of PVPS ($) net annual cost of PVPS after n year ($) price of equipments in present year ($) cumulative present worth factor cumulative present worth factor at the end of year effective rainfall (mm) deep percolation (mm) discount rate reference evapotranspiration (mm) crop evapotranspiration (mm) gravitational constant (m/s2) pumping head (m) peak solar radiation (W/m2)
issues must be considered for having a feasible PVPS. They urged that a feasible PVPS must be both technically and economically viable. Having available land to put the PV panel is the crucial point in the technical issue. On the other hand, the PVPS is considered economically feasible if its lifetime cost is the lowest among all alternatives available in the farm. Belgacem (2012) investigated solar water pumping in Tunisia. According to his studies, PVPS is one of the most economical ways to irrigation in remote areas especially in developing countries. He illustrated performance test of the water pumping system under the local climate condition and showed that at the constant head pumping, the maximum overall efficiency of the system is 3.7% and the mean efficiency in this period is 2.5%. Cloutier and Rowley (2011) investigated the feasibility of the renewable energy sources such as solar energy and wind energy for drinking water and other domestic or agricultural uses. They reported that the mean daily global solar radiation of 4.39 kW h/m2 in some cities of Nigeria as a vital requirement value for having a feasible solar pumping system. The technical and economic feasibility of the PV water-pumping in Turkey, a neighbor of Iran, is what Senol (2012) has studied. He proposed a mobile PV power station to derive a pump to store water in a tank for irrigation use. The ability of the power station movement allows using this system from one farm to another. In addition, protection of this system against the act of vandalism is easier than the fixed one. The economic analysis proves that the PV powered pump was preferable in the long run it Turkey. Locating in the sun belt of the world, the application of PV systems has started since 1982 in Iran (Zabihi et al., 1998). The PV systems have been installed in all over the country, except the north and west bands. The reason is in the high price of PV systems and the few numbers of sunny days per year. Zabihi et al. (1998) reported some examples of PV power plant in the range of 5– 10 kW for several purpose of use such as lighting of a village, building electrification, supply a telecommunication site, supply of VHF link and water pumping in the different cities of Iran. They stated that in 1993 CE a production line for fabrication of multicrystalline silicon solar cells and modules was installed with the nominal capacity of 1 MW per year in one shift of operation. The efficiency of cells was between 12.5% and 14%. Nowadays there are several industrial corporations in Iran, which are working on fabrication, production and manufacturing solar panels. Guilan province, the Southwest coast of the Caspian Sea, has a different climate in comparison with the other hot and dry parts of Iran. This region has a temperate and humid climate with aver-
i Kc NIWR NNSD n PP PW PWF Q Rtot SD TDL
q gA gcoulomb gp
inflation rate crop coefficient net irrigation water requirements (mm) number of no sunny days number of year pumping power (W) present worth ($) present worth factor pumping volumetric flow rate (m3/s) total rainfall (mm) storage demand (W h) total daily load (W h) water density (kg/m3) array conversion efficiency Coulomb efficiency pumping efficiency
age annual precipitation around 1850 mm (Guilan Meteorological Administration, 2012). It should be noted that the average annual precipitation in Iran is around 236 mm (Guilan Meteorological Administration, 2012). Having enough water, fertile lands and rather high relative humidity make Guilan province one of the main sources of producing rice in the country. More than 205,000 ha (0.5 million acres) of this province, which is 35.81% of the total paddy fields of Iran, has been cultivated with rice. In this region, the usual irrigation method is flood irrigation which continues from the beginning to the end of the growing season and the conventional method of cultivation is wet tillage with manual transplanting (Mostafazadeh-Fard et al., 2010). These flooded rice fields have different sizes about 200 m2 up to several hectares. Fossil fuel price fluctuations and cutting and gradually elimination of subsidies by the government have urged the farmers to use the other sustainable types of energy to power the farm pumping system. Moreover, because of limitation in water source, using of water saving irrigation systems rather than conventional system is an inevitable plan in the near future. Solar energy by using stand-alone PV panels is superseding the conventional pumping system. As stated before, this area has the lower sunny days than the other parts of the country so in this paper, the PV system is designed just for use in the sunny months when the energy usage for irrigation fields increases. In the following sections, some climatologically aspects of the Guilan province, paddy fields description, water requirement and the conventional pumping system are presented. The measured global solar irradiance is studied and compared with EU PVGIS data. In addition the daily average clearness index is computed. The lifecycle costs method is used to compare the conventional and PV pumping system economically.
2. Field and pumping description 2.1. Field and climatologically characteristics Fig. 1 illustrates Caspian Sea, Guilan province and its location in Iran. The Alborz Mountain range separates the Iranian plateau from the Caspian Sea and the Safidrud river crosses through the mountains and flat plain and enters into the Caspian Sea near the city of Rasht, the capital of Guilan province. Guilan has several synoptic meteorological stations. One of them is located at Rasht with lati-
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Fig. 1. A schematic view of Guilan province and its location in Iran.
tude 37.15°N, longitude 49.36°E coordinates and 6.9 m above sea level named Agriculture station. This station has collected data from 1956 CE until now. To find out a crude estimation of the climate condition of this region, some selected data of this station are shown in Figs. 2–4. Fig. 2 shows the variation of monthly average daily temperature. In the hot months, the average daily temperature reaches to 25 °C, although the maximum monthly average temperature of 32.9 °C has been recorded at 1975, July (Guilan Meteorological Administration, 2012).
Fig. 3 presents the average relative humidity in Rasht (Guilan Meteorological Administration, 2012). The minimum value is around 74% in the hottest month of summer. Rather high value of the average relative humidity is one of the main characteristics of this area and is essential for rice to grow. Fig. 4 illustrates the investigation of total amount of precipitation (Guilan Meteorological Administration, 2012). The heavy rainfall in the fall, winter, and early of spring is collected in some natural reservoirs. This water is used as a source of water supply for irrigation during the irrigation period. This precipitation
Fig. 2. Average of daily temperature, Average value from 1956 to 2005.
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Fig. 3. Average of relative humidity from 1956 to 1991.
Fig. 4. Average of total precipitation, average value from 1956 to 2005.
amount guarantees the existence of required amount of water for irrigation during springs and summers. Fig. 5 presents the average recorded sunny hours (Guilan Meteorological Administration, 2012). As it can be seen, the sunny hours increase in spring and summer with an average 5.81 h per day. This is in accordance with the supposed daily working hours of pump in the next sections. To be more specific, Fig. 6 shows the details of the sunny hours and rainfall during the irrigation period in 2015 CE (Guilan Meteorological Administration, 2012). There are 82 days with the sunny hours more than 6 h per day. Moreover, the number of days with a minimum of 10 mm rainfall is 13 days. The number of the fully cloudy days, i.e. no sunshine and no rainfall, is 20 days with a maximum 4 consecutive days. In this study, a 5000-m2 rice field has been considered to study. It is located near to the Rasht and there is no grid line in the vicinity.
2.2. Water requirement Rice water consumption is high in growing period. According to the international rice research institute there are no data available on the amount of the irrigation water used by all the rice fields in
the world (Bouman et al., 2007). Yoo et al. (2012) proposed the following expression for net irrigation water requirements (NIWR):
NIWR ¼ ET C þ DP EFR
ð1Þ
where ETC is the crop evapotranspiration (mm), DP is the deep percolation (mm) and EFR is the effective rainfall (mm). The crop evapotranspiration can be determined by using reference evapotranspiration (ET0) and crop coefficient (KC) as follows:
ET C ¼ K C ET 0
ð2Þ
In Eq. (2) KC is a dimensionless parameter that is related to the crop water consumption. FAO exclaimed the amount of rice crop coefficient equal to 1.2 (FAO corporate document repository, 2016). Tyagi et al. (2000) obtained the rate of rice crop coefficient equal to 1.29. Although the most rate of crop coefficient is expressed by Mohan and Arumugam (1994) equal to 1.65, for dry season’s rice. Reference evapotranspiration (ET0) can be determine by climate and whether characteristics. Dinpashoh (2006) expressed ET0 for capital of Guilan province, Rasht, in the irrigation period. For more details, see Table 1. Deep percolation is determined by Plusquellec (1996) for Guilan province. According to his investigations, daily rice deep percola-
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Fig. 5. Average sunny hours, average value from 1956 to 2005.
Fig. 6. Daily sunny hours and rainfall for irrigation period, 2015.
tion changes between 1.6 mm/day to 9 mm/day for Fuman city (close to the Rasht) in the most permeable areas. In the next step, effective rainfall (EFR) can be determined according to total rainfall (Rtot ) by Smit et al. (1992) approximation which is expressed as follow:
EFR ¼ 0:6Rtot 10 for Rtot < 70 mm=month
ð3Þ
EFR ¼ 0:8Rtot 24 for Rtot P 70 mm=month
ð4Þ
In this study, the Dinpashoh (2006) value for ET0 is used for determining ETC by consideration crop coefficient equal to1.65 (Mohan and Arumugam, 1994) (the highest water consumption value among the reported data for K C ). Rice deep percolation is considered 5.45 mm/day (mean of the maximum and minimum
rates of percolation depth reported by Plusquellec (1996). Details of the rice water requirement are demonstrated in Table 1. In Guilan province, rice irrigation is carried out arbitrarily at a time between April to May. Hence, two states are considered and studied for determining the net rice water requirement in which in the first state irrigation is started in April and finishes in August. Also in the second state, irrigation begins in May and it is stopped in September.
2.3. Pumping power requirement The required pumping power for irrigation relies on several parameters such as pumping head, suction head, pipes length,
Table 1 Mean monthly rice water requirement in irrigation period (mm).
April May June July August September
ET 0 Dinpashoh, 2006
KC
ETc
DP
Rtot (Guilan Meteorological Administration, 2012)
EFR
68 112 154 169 148 105
1.65 1.65 1.65 1.65 1.65 1.65
112.2 184.8 254.1 278.8 244.2 173.2
163.5 169 163.5 169 169 163.5
63.5 54.3 44.7 42 71.4 157.4
28.1 22.6 16.8 15.2 33.1 102
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and volumetric flow rate. Eq. (5) shows the pumping power as a function of some important parameters (Kelley et al., 2010):
PP ¼ qghQ=gP
ð5Þ
where PP is the pumping power (W), q is the water density (kg/m3), g is the gravitational acceleration (m/s2), h is the pumping head (m), gp is the pump efficiency, and Q is the required volumetric flow rate (m3/s). Table 2 shows some general information about the irrigation time and other parameters related to pump in two states which will be used later. From Table 2 it can be concluded that the maximum required water for rice paddies in Guilan province fields is 11.7 mm/day for irrigation started in April. Pumping head is determined as for pipe friction losses 5 m length by 1.5 in. diameter. The higher rate of insolation increases the rate of water evaporation. On the other hand, the greater rate of water evaporation results the higher power for irrigation because of increasing pumping hours. Meanwhile with a greater rate of irradiance, the more energy will be achieved by PV panels. Therefore, there is a coincidence between the peak of required power for irrigation and peak of received solar energy. This fact is an important advantage of solar irrigation systems. 2.4. Conventional pumping system The conventional pumping system employed a gasolinepowered motor-pump to irrigate the paddy. Table 3 shows the considered pump’s characteristics (Robin Industrial Engines, 2012). This pumping system is an on-off system. It means the pump has to work during a required time interval, which in this case is four to six hours per day. The irrigation hours strongly depends on the stage of the rice growing. An energy review reveals that just the pumping system is the main energy consumer in this filed. Fig. 7 shows a schematic of the paddy, the natural reservoir, and the gasoline pumping system. 3. PVPS design In this section, some important aspect of the PV pumping system is discussed. The daily-average measured global solar irradiance, the tilt angle, PV panels sizing and the required pumping system are investigated. Fig. 8 illustrates a general schematic of the PVPS. 3.1. Solar irradiance Fig. 9 shows the albedometer which is used to record global irradiance in the Rasht synoptic meteorological stations (Guilan Meteorological Administration, 2012). The albedometer model is CMA6 which is constructed around two CMP6 pyranometer sensors manufactured by Kipp and Zonen, the Netherland. The spectral range of this device is from 285 to 2800 nm, sensitivity is 5 to 20 mv/W/m2 and its response time is less than 18 s. The crude pyraTable 2 Details of two state irrigation beginning.
Irrigation beginning time Irrigation period (days) Sum of ETc (mm) Sum of EFR (mm) Sum of DP (mm) Net water requirement (m3 =ha) Pump efficiency % Pumping head (m) Power requirement (W)
State 1
State 2
April 153 1074.1 115.8 834 17,923 0.6 3 132
May 153 1135.1 189.7 834 17,794 0.6 3 128
Table 3 Characteristics of a conventional pumping system (Robin Industrial Engines, 2012). Model
Robin EY15D
Continuous rated output (HP/rpm) Cooling system Lubrication/Lubricant
2.2/3000 (1.64 kW) Forced Air Cooling Splashing type/automobile oil class SC Automobile gasoline 280 (0.832 L/h) at continuous rated output 600
Fuel Fuel consumption ratio (g/HP h) Continuous delivered volumetric flow (L/min)
nometer data are analyzed with respect to other data like daily sunshine hours. These data represent the sum of direct, ground, and diffuse reflected irradiance in 2015. Fig. 10 presents the data of maximum and average daily global solar radiation. The highest values of 1060 and 441.7 W/m2 in maximum and average data are recorded in June 10 and July 30, respectively. Table 4 presents the monthly mean daily values of global solar irradiance in Rasht (Guilan Meteorological Administration, 2012). These data are compared with EU PVGIS data (European Commission Joint Research Center, 2012) which are calculated from satellite data for a period 1999 up to present in 30-min time-step. According to Table 4, the average peak sunny hours are equal to 6.08 kW h/m2/day and 6.17 kW h/m2/day for irrigation period began in April and May, respectively. As it was remarked earlier, there are some fully cloudy days in this region, so calculating the daily average clearness index is necessary. This parameter is defined as the ratio of the global solar irradiance at the surface falling on a horizontal plane by the corresponding extraterrestrial irradiation on a horizontal plane for the sometime period (Markvart and Castaner, 2003). Fig. 11 shows the values of mean monthly clearness index from 2010 to 2015 for Rasht city (Guilan Meteorological Administration, 2012). This data are compared with the Islam et al. (2009) data in Abu Dhabi. The results of the Islam et al. (2009) investigations are also reported in Table 5. According to the Table 5 and Fig. 10, though the annual scale between Rasht and Abu Dhabi (that has a strong potential for solar energy capture) is different, but in six months of irrigation period, mean monthly clearness index values are very close together. This average value of clearness index in irrigation months indicates that Guilan province is a good candidate for using PVPS system.
3.2. Solar panel tilt angle Tilt angle is one of the most important parameters in gaining solar energy by PV panels. It depends on the many parameters such as season, location, PV capacity, and climate. Kaldellis and Zafirakis (2012) investigated the optimum value of the tilt angle in nearAthen regions, experimentally. They reported that for summeronly applications the optimum tilt angle is 15° ± 2.5. AslSoleimani et al. (2001) worked on the optimum tilt angle experimentally for Tehran, the capital of Iran. Results show that a small tilt angle around 0°–5° is preferable in summers especially for irrigation pumping. Due to close latitude between Rasht and Tehran, in the present work the tilt angle is assumed to be around 5° ± 2.5. The tilt angle variation from 0° to 23°, showed a slight variation in energy achieved by PV panels, (less than 5%) AslSoleimani et al., 2001. Thus, the horizontal albedometer data are used for recording the solar irradiance.
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Fig. 7. A schematic of the paddy, the natural reservoir, and the gasoline pumping system.
Fig. 8. A general schematic of the PVPS.
Fig. 9. Two view of Rasht metrological albedometer.
Fig. 10. Data of daily maximum and average global irradiance, 2015.
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Using Eq. (6) and according to the suggested centrifugal pump specifications, panel area for satisfy two states of irrigation periods is calculated about 2.7 m2.
Table 4 Monthly mean daily of global solar irradiance. Month
January February March April May June July August September October November December
Global solar irradiance, kW h/m2/day Present study (Guilan Meteorological Administration, 2012)
EU PVGIS data (European Commission Joint Research Center, 2012)
2.52 2.73 4.72 4.69 5.58 7.10 6.69 6.37 5.10 3.84 2.58 2.12
2.05 2.71 3.69 4.97 6.28 7.04 6.76 5.99 4.66 3.32 2.16 1.84
3.5. Storage system designing It is common in designing PV systems to store excessive energy into the some batteries. The excessive energy is stored in the battery to provide electricity for cloudy day’s irrigation. Indeed, there will be some cloudy days during the irrigation period. So to overcome the loss of sunshine, the paddy should be irrigated by the battery storage. The storage demand can be determined by following expression (Zobaa and Bansal, 2011):
SD ¼ ðTDL NNSDÞ=gcoulomb
3.3. PV power station sizing Estimation the size of the PV panel area is related to the continuous power that is needed in the pumping system. In Eq. (6) the relation among panel area (m2), continuous power (W), peak solar radiation (W/m2) and selected PV panel’s efficiency is given (Kelley et al., 2010):
APV ¼ PP =ðIP gA Þ
553
ð6Þ
In this study the LG220P1C is used for solar panel. The specifications of the selected panel are provided in Table 6.
ð7Þ
where SD is the storage demand (Wh), TDL is the total daily load and equal to 1.2 times of total daily energy (Wh), NNSD is the number of no sunny days and gcoulomb is the coulomb efficiency which is usually taken as 0.8 (Zobaa and Bansal, 2011). Fig. 12 shows the number of the consecutive no sunny days from 2010 to 2015 (Guilan Meteorological Administration, 2012). According to Fig. 12, five years average of this parameter varied from 1.33 for June to 5.5 for January. In this investigation this parameter is intended 4 days consecutive for irrigation period. The battery storage demand (SD) for two irrigation states began in April and May is calculated equal to 4815 (W h) and 4739 (W h), repectively. Table 8 shows the selected battery details (Trojan Battery Company, 2013). As stated before, there should be enough land in the field to put the PVPS facilities like PV modules, battery, inverter and other equipment on it.
3.4. Motor-pump system 4. Economic analysis The motor pump unit in the PVPS is a centrifugal AC motor pump unit. Its characteristic is shown in Table 7 (PEDROLLO Distribution Ltd, 2016). Selected pump is determined according to the power requirement and pumping head. This pumping system is widely used in irrigation applications.
The lifecycle costs of both conventional pumping system and PVPS are studied in this section. This method is widely used to compare the renewable system versus conventional ones (Kelley et al., 2010; Cloutier and Rowley, 2011; Senol, 2012). All prices
Fig. 11. Values of clearness Index: monthly average values from 2010 to 2015.
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Table 5 Comparison of clearness index between Rasht and Abu Dhabi from 2010–2015.
Rasht Station (Guilan Meteorological Administration, 2012)
2010 2011 2012 2013 2014 2015
Abu Dhabi (Islam et al., 2009)
Six months irrigation period
Annual
0.57 0.54 0.56 0.55 0.57 0.56
0.5 0.48 0.49 0.49 0.48 0.5
0.59
0.58
Table 6 PV Module characteristics (LG Electronics Company, 2016). PV Model
LG220P1C
Area (m2) Efficiency Pmax (W) Voltage in maximum power (Volt) Current in maximum power (A) Open circuit voltage (V) Short circuit current (A)
1.46 13.7 220 28.9 7.62 36.1 8.21
Table 7 Selected pump’s details. Type
Centrifugal pump HFm 50B
Factory Nominal power (W) Inlet diameter(in) Outlet diameter(in) Maximum volumetric flow rate (L/min) Maximum pumping head (m)
PEDROLLO 370 1.5 1.5 300 10
Table 8 Details of the selected battery (Trojan Battery Company, 2013). Model number
L16RE-B
Company Voltage (V) Amperage (20 h) (A h) Weight (kg) Chemistry
Trojan 6 370 54 Flooded
cant and worker’s payment for periodically checking. The motor pump unit is assumed to work for 10 years. After that it should be replaced with a new one. The fuel price for this pumping system is calculated based on no-subsidy price and according to one irrigation period with average working time of 5 h per day. Transition cost is all of costs for transference gasoline from gasoline station to the rice field. The one liter of gasoline is assumed to be constant and equal to 0.25 US dollar. Table 9 shows the details of the conventional system costs. 4.2. PV pumping system In the PV pumping system major costs, consist of the centrifugal pump, wiring, electronics, battery, and the installation. Repair and maintenance costs include equipment replacement, worker’s payment, security issues and salvage prices. The main electrical equipment, such as inverter assumed to work for 9 years. In addition the motor pump unit will work for 10 years because of working under a very humid situation. The battery storage will work for 10 years, too. Table 9 shows the prices for PVPS per year. 4.3. Lifecycle cost method
are converted to US dollar for simplification. It is obvious that if the lifecycle costs of PVPS are lower than the conventional system, the PVPS is economically feasible.
Lifecycle cost method uses the present worth factor (PWF) for comparison of the price of equipment during different years, and is defined by Eq. (8) Messenger and Ventre, 2003: n
PWF ¼ ð1 þ i=1 þ dÞ 4.1. Gasoline pumping system In Conventional pumping system, the major costs include motor-pump unit and installation of system. Repair and maintenance costs include equipment replacement such as oil filter, lubri-
ð8Þ
where i is the inflation rate, d is the discount rate and n is the number of years. Eq. (9) shows the present worth by assuming that, x = 1 + i/1 + d (Messenger and Ventre, 2003):
PW ¼ PWF:A0 ¼ xn A0
Fig. 12. Data for number of average consecutive no sunny days from 2010 to 2015.
ð9Þ
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M. Niajalili et al. / Solar Energy 150 (2017) 546–557 Table 9 Lifecycle costs of two pumping system. PVPS costs (US Dollar)
Conventional costs (US Dollar)
Major Costs
Panels Centrifugal Pump Battery Inverter and other electronics Installation
650 200 1400 450
Repair and Maintenance Costs
Cleaner labor plus security (per year) Electronic replacement plus maintenance (per year)
300
300 100
Oil filter, fuel filter, Lubricant oil replacement (per year) Maintenance labor (per year)
300
Fuel & transition cost Annual R and M plus Fuel costs
450 950
200
100
Annual R and M costs
400
Average discount rate Average inflation rate Total lifecycle cost
Gasoline Pump Installation
200
13% 13.75% 19766
Total lifecycle cost
30890
where A0 is the price of equipments in the present year. In the next step for accounting the fuel cost and other annual costs that is purchased at the outset of the year, used the cumulative present worth factor (CPWF) which is shown in Eq. (10) Messenger and Ventre, 2003.
CPWF ¼ ðð1 xn Þ=ð1 xÞÞ
ð10Þ
Then for accounting the annual cost that supply is purchased at the end of lifetime, used the cumulative present worth factor at the end of year (ECPWF) which is shows in Eq. (11) Messenger and Ventre, 2003:
ECPWF ¼ xðCPWFÞ
ð11Þ
In this paper, the annual fuel requirement cost and other annual costs for gasoline pumping system are assumed to be purchased at the beginning of the year. In the other hand, the PVPS annual cost is purchased at the end of the year. Hence, the net annual cost for PVPS (ACPnet) and gasoline pumping system (ACGnet) are expressed as follow:
ACPnet ¼ ECPWF ACP
ð12Þ
ACGnet ¼ CPWF ACG
ð13Þ
In this analysis, the average inflation rate per year assumed constant and equal to 13.75% (Cetral Bank of The Islamic Republic of Iran, 2016. The life time of both systems are considered to be equal, about 25 years. The average discount rate assumed to be around 13% (Melli Bank of The Islamic Republic of Iran, 2016; Maskan Bank of The Islamic Republic of Iran, 2016). A US dollar considered to be equal to 3500 Iranian Rials in this study. The price of common facility in both systems such as pipes is not included. Costs are divided into three parts: major costs, repair and maintenance, and fuel. Data is obtained from local people and construction companies by a query.
Fig. 13. Pumping power and PV area versus field area.
varies according to the required irrigation power and for this case the PV panel area should be 2.7 m2. This PV panel area dictates the farmer to select two pieces suggested PV panels (see Table 6) which can provide the maximum power up to 0.44 kW. As depicted before in Fig. 2, the average monthly temperature does not exceed 25.2 °C in hot months, which is an advantage of Guilan weather that makes it possible to get the maximum efficiency from selected PV.Table 10 shows the details of the solar design parameters in irrigation period in this study. According to Table 10, selected centrifugal pump and battery storage require two pieces selected PV panel and four pieces suggested batteries. Also according to Table 9, the total lifecycle cost for gasoline pumping system is around 1.56 times of the PVPS.
5. Results and discussion In this section, results are presented for both technical and economical aspects of the PVPS feasibility in Guilan province in Iran. Fig. 13 presents the required pumping power for paddy and the panel area according to the paddy area specifications. It is evident that as the area is increased, pumping system needs more power to handle the necessary irrigation water. For the case study, a 5000 m2 paddy, by assumed the selected centrifugal pump, the required pumping power is 0.37 kW. In addition the PV panel area
Table 10 Solar design parameter for irrigation period. Power requirement (W) Average peak sunny hours Panel area (m2) Battery capacity (W h) Field area (m2) Number of panel requirement (pieces) Number of battery requirement (pieces)
370 6.08 2.7 7559 5000 2 4
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ments. The authors also thank the Rice Research Institute of Iran for their valuable information about rice cultivation and water usage.
References
Fig. 14. Data of lifecycle cost estimation.
Fig. 14 shows the investigation of the lifecycle cost analysis for both PVPS and conventional pumping system. According to Fig. 14, the initial cost of the PVPS is about 7 times of the conventional pumping system. This is the main impediment in using PVPS in the paddies for irrigation. As it can be seen, after around 9 years the total costs of both systems would be equal. Therefore using PVPS is economically feasible and logical. Also Fig. 14 indicates that at the end of the 25 years irrigation period, the final costs of the conventional pumping are 1.56 times of the PVPS. It is worth to mention that, there should be enough land in the field to put the panel area on it. For this case study, the required area is assumed to replace with the conventional system. In the studied case, the paddy’s area is 0.5 ha and the required PV panel area is 2.7 m2, so certainly covering just 0.05% of paddy’s total area with PV panel, cannot have tangible effects on the rice production. This fact is also meaningful for larger paddies. 6. Conclusion Enough available water and solar irradiance are two important parameters for having a viable PVPS. The North of Iran, especially Guilan province, has a good potential to experience the sustainable and clean solar energy. Having enough precipitation, monthly mean solar irradiance of 5.92kW h/m2/day and the six year average clearness index of about 0.56, make Guilan a perfect place to employ solar irrigation. The main barrier is the relatively large initial outlay, although the lifecycle cost comparison with the gasoline pumping system shows the lower costs of the PV pumping systems. For the considered case study, a 5000-m2 rice paddy, the required PV modules area is calculated equal to 2.7-m2 to power a selected centrifugal pump system of 0.37 kW. Also, the economical comparison between PVPS and gasoline pumping system in 25 years period of irrigation reveals that in spite of high initial costs of the PVPS, it will reach to the conventional gasoline pumping system costs just in 9 years. Moreover, it is found that at the end of mentioned irrigation period, the final costs of the conventional pumping system would be equal to 1.56 times of the PVPS which implies the PVPS merriness for irrigation in Guilan province. Acknowledgement The authors would like to acknowledge Guilan Meteorological Administration for giving the crude data and their useful com-
Al-Karaghouli, A., Al-Sabounchi, A.M., 2000. A PV pumping system. Appl. Energy 65, 145–151. Asl-Soleimani, E., Farhangi, S., Zabihi, M.S., 2001. The effect of tilt angle, air pollution on performance of photovoltaic systems in Tehran. Renewable Energy 24, 459– 468 . Belgacem, B.G., 2012. Performance of submersible PV water pumping systems in Tunisia. Energy Sustain. Develop. 16, 415–420 . Bouman, B.A., Lampayan, R.M., Tuong, T.P., 2007. Water Management in Irrigated Rice. International Rice Research Institute, Los Banos, Philipine. https://goo.gl/ 9oCWbY. Bouzidi, B., 2011. Viability of solar or wind for water pumping systems in the Algerian Sahara regions – case study Adrar. Renew. Sustain. Energy Rev. 15, 4436–4442 . Cetral Bank of The Islamic Republic of Iran, 2016. Advance Statistics. Available in: (accessed 15.12.2016). Cloutier, M., Rowley, P., 2011. The feasibility of renewable energy sources for pumping clean water in sub-Saharan Africa: a case study for Central Nigeria. Renewable Energy 36, 2220–2226 . Cuadros, F., Lopez-Rodrıguez, F., Marcos, A., Coello, J.A., 2004. Procedure to size solar-powered irrigation (photo irrigation) schemes. Sol. Energy 76, 465–473 . Diarra, D.C., Akuffo, F.O., 2002. Solar photovoltaic in Mali: potential and constraints. Energy Convers. Manage. 43, 151–163 . Dinpashoh, Y., 2006. Study of reference crop evapotranspiration in I.R. of Iran. Agric. Water Manag. 84, 123–129 . PEDROLLO Distribution Ltd, 2016. Available in: (accessed 15.12.2016). European Commission Joint Research Center, 2012. PVGIS Solar Irradiance Data. Available in: (accessed 15.12.2016). FAO Corporate Document Repository, 2016. Available in: http://www.fao. org/docrep/x0490e/x0490e0b.htm (accessed 15.12.2016). Firatoglu, Z.A., Yesilata, B., 2004. New approaches on the optimization of directly coupled PV pumping systems. Sol. Energy 77, 81–93 . Guilan Meteorological Administration, 2012. Iran, Rasht. Available in: (accessed15.12.2016). Hamidat, A., Benyoucef, B., Hartani, T., 2003. Small-scale irrigation with photovoltaic water pumping system in Sahara regions. Renewable Energy 28, 1081–1096 . Islam, M.D., Kubo, I., Ohadi, M., Alili, A.A., 2009. Measurement of solar energy radiation in Abu Dhabi, UAE. Appl. Energy 86, 511–515 . Kaldellis, J., Zafirakis, D., 2012. Experimental investigation of the optimum photovoltaic panels’ tilt angle during the summer period. Energy 38, 305–314 . Kelley, L.C., Gilbertson, E., Sheikh, A., Eppinger, S.D., Dubowsky, S., 2010. On the feasibility of solar-powered irrigation. Renew. Sustain. Energy Rev. 14, 2669– 2682 . LG Electronics Company, 2016. Solar Products. Available in: (accessed 15.12.2016). Mahmoud, E., el Nather, H., 2003. Renewable energy and sustainable developments in Egypt: photovoltaic water pumping in remote areas. Appl. Energy 74, 141– 147 . Markvart, T., Castaner, L., 2003. Practical Handbook of Photovoltaic’s: Fundamentals and Applications. Elsevier Advanced Technology https://goo.gl/1YGLV1. Maskan Bank of The Islamic Republic of Iran, 2016. Available in: (accessed 15.12.2016). Melli Bank of The Islamic Republic of Iran, 2016. Available in: (accessed 15.12.2016). Messenger, R.A., Ventre, J., 2003. Photovoltaic Systems Engineering, second ed., New York Washington DC. . Mohan, S., Arumugam, N., 1994. Irrigation crop coefficients for lowland rice. Irrigat. Drainage Syst. 8, 159–176 . Mostafazadeh-Fard, B., Jafari, F., Mousavi, S.F., Yazdani, M.R., 2010. Effects of irrigation water management on yield and water use efficiency of rice in cracked paddy soils. Aust. J. Crop Sci. 4, 136–141 .
M. Niajalili et al. / Solar Energy 150 (2017) 546–557 Plusquellec, H., 1996. Guilan, a successful irrigation project in Iran. Irrigat. Drain. Syst. 10, 95–107. Ramos, J.S., Ramos, H.M., 2009. Solar powered pumps to supply water for rural or isolated zones: a case study. Energy sustain Develop. 13, 151–158 . Raugei, M., Frankl, P., 2009. Life cycle impacts and costs of photovoltaic systems: current state of the art and future outlooks. Energy 34, 392–399 . Robin Industrial Engines, 2012. Manual models EY15D, No 1193S103. Robin America, INC (accessed 15.12.2015). Available in: . Senol, R., 2012. An analysis of solar energy and irrigation systems in Turkey. Energy Policy 47, 478–486 . Smit, M., 1992. A computer program for irrigation planning and management, Irrigation and Drainage Pap. 46, Food and Agric. Org. of the U. N., Rome. .
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Contents lists available at ScienceDirect
Solar Energy journal homepage: www.elsevier.com/locate/solener
Techno-economic feasibility of off-grid solar irrigation for a rice paddy in Guilan province in Iran: A case study Mehdi Niajalili a, Peyman Mayeli b,⇑, Mohammad Naghashzadegan c, Amin Haghighi Poshtiri c a
Department of Mechanical Engineering, Kadous Institute of Technology and Higher Education, Rasht, Iran Young Researchers and Elite Club, Lahijan Branch, Islamic Azad University, Lahijan, Iran c Department of Mechanical Engineering, Guilan University, P.O. Box 3756, Rasht, Iran b
a r t i c l e
i n f o
Article history: Received 23 January 2017 Received in revised form 20 April 2017 Accepted 4 May 2017
Keywords: PV pumping system Irrigation Global irradiance Lifecycle cost Clearness index Solar panel
a b s t r a c t In this study, a typical rice paddy in Guilan province of Iran is considered and the technical and economical feasibility of the solar powered pumping system is studied. The monthly mean daily solar irradiance has been studied for this area and the measured data is compared with European Photovoltaic Geographic Information System (EU PVGIS) model for Middle East, including Iran. The investigations imply that the average monthly mean daily solar irradiance in irrigation months are reported equal to 5.92 kW h/m2/day by Guilan Meteorological Administration and 5.95 kW h/m2/day by EU PVGIS. A mean monthly clearness index from 0.54 to 0.57, in irrigation period, gives Guilan province a good potential to employ photovoltaic (PV) pumping system. In this study, the appropriate size of the PV panels and the lifecycle cost estimation of PV pumping system in comparison with conventional systems are presented. Also, the area of the PV solar panel to supply required power of the pumping system for a rice paddy with specified area is calculated. Results show that though the initial outlay of the PV system is about 9 times of the conventional systems but the total lifecycle costs of the PV pumping system is just 65.6% costs of the conventional pumping system. Also in spite of high initial costs of the PV pumping system, it is found that after around 9 years, the total costs of both systems would be equal to conventional one i.e. gasoline pumping system and after this time, the costs of the conventional pumping system will exceed the PV solar panel system. Ó 2017 Elsevier Ltd. All rights reserved.
1. Introduction The idea of using the sustainable solar energy by means of photovoltaic (PV) cells for irrigation and water pumping is a modern and well-accepted one. Many developing countries are using PV systems as a source of energy at least in remote areas (Zabihi et al., 1998; Al-Karaghouli and Al-Sabounchi, 2000; Diarra and Akuffo, 2002; Mahmoud and el Nather, 2003; Firatoglu and Yesilata, 2004; Ramos and Ramos, 2009; Bouzidi, 2011). The main problem of using PV in Iran and other developing countries is the initial cost of these systems. Because of both falling costs of the PV cells (Raugei and Frankl, 2009) and price fluctuations of the fossil fuels, the general tendency toward the employing solar energy systems is increased. It means that using PV as a source of green and sustainable energy can have economic reasons. Like other uses of PVs in industry, here, to irrigate a typical field, estimation of the ⇑ Corresponding author at: Islamic Azad University, Lahijan Branch, University Blvd, P.O. Box: 41438-57986, Lahijan, Guilan, Iran. E-mail address: [email protected] (P. Mayeli). http://dx.doi.org/10.1016/j.solener.2017.05.012 0038-092X/Ó 2017 Elsevier Ltd. All rights reserved.
required array area is an important part of design process. Hamidat et al. (2003) studied the Sahara regions; an area of high level of monthly average solar radiation. They considered several crops, say, wheat, potato, tomato and sunflower. It was found that the PV water pumping system could easily cover the daily water need rates for small-scale irrigation with an area smaller than two hectares. Cuadros et al. (2004) studied a procedure to estimate the required dimension of a PV installation designed to power a pumping system for the drip irrigation of an olive tree orchard in southwest Spain. They divided their work into three different parts: first, determination of the soil and climate characteristics of the considered land, second, a hydraulic analysis of the pumping system and finally calculating-measuring the peak photovoltaic power required for irrigation. As it was remarked earlier, PV powered pumping is a tempting and modern way to use the available solar irradiance, so lots of countries are trying to examine the feasibility of the PV pumping system (PVPS) for irrigation or even for pumping clean water. Kelley et al. (2010) presented a comprehensive study on the feasibility of solar-powered irrigation. They showed that two main
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Nomenclature APV ACG ACGnet ACP ACPnet A0 CPWF ECPWF EFR DP d ET0 ETc g h Ip
area of PV panels (m2) annual cost of gasoline pumping system ($) net annual cost of gasoline pumping system after n year ($) annual cost of PVPS ($) net annual cost of PVPS after n year ($) price of equipments in present year ($) cumulative present worth factor cumulative present worth factor at the end of year effective rainfall (mm) deep percolation (mm) discount rate reference evapotranspiration (mm) crop evapotranspiration (mm) gravitational constant (m/s2) pumping head (m) peak solar radiation (W/m2)
issues must be considered for having a feasible PVPS. They urged that a feasible PVPS must be both technically and economically viable. Having available land to put the PV panel is the crucial point in the technical issue. On the other hand, the PVPS is considered economically feasible if its lifetime cost is the lowest among all alternatives available in the farm. Belgacem (2012) investigated solar water pumping in Tunisia. According to his studies, PVPS is one of the most economical ways to irrigation in remote areas especially in developing countries. He illustrated performance test of the water pumping system under the local climate condition and showed that at the constant head pumping, the maximum overall efficiency of the system is 3.7% and the mean efficiency in this period is 2.5%. Cloutier and Rowley (2011) investigated the feasibility of the renewable energy sources such as solar energy and wind energy for drinking water and other domestic or agricultural uses. They reported that the mean daily global solar radiation of 4.39 kW h/m2 in some cities of Nigeria as a vital requirement value for having a feasible solar pumping system. The technical and economic feasibility of the PV water-pumping in Turkey, a neighbor of Iran, is what Senol (2012) has studied. He proposed a mobile PV power station to derive a pump to store water in a tank for irrigation use. The ability of the power station movement allows using this system from one farm to another. In addition, protection of this system against the act of vandalism is easier than the fixed one. The economic analysis proves that the PV powered pump was preferable in the long run it Turkey. Locating in the sun belt of the world, the application of PV systems has started since 1982 in Iran (Zabihi et al., 1998). The PV systems have been installed in all over the country, except the north and west bands. The reason is in the high price of PV systems and the few numbers of sunny days per year. Zabihi et al. (1998) reported some examples of PV power plant in the range of 5– 10 kW for several purpose of use such as lighting of a village, building electrification, supply a telecommunication site, supply of VHF link and water pumping in the different cities of Iran. They stated that in 1993 CE a production line for fabrication of multicrystalline silicon solar cells and modules was installed with the nominal capacity of 1 MW per year in one shift of operation. The efficiency of cells was between 12.5% and 14%. Nowadays there are several industrial corporations in Iran, which are working on fabrication, production and manufacturing solar panels. Guilan province, the Southwest coast of the Caspian Sea, has a different climate in comparison with the other hot and dry parts of Iran. This region has a temperate and humid climate with aver-
i Kc NIWR NNSD n PP PW PWF Q Rtot SD TDL
q gA gcoulomb gp
inflation rate crop coefficient net irrigation water requirements (mm) number of no sunny days number of year pumping power (W) present worth ($) present worth factor pumping volumetric flow rate (m3/s) total rainfall (mm) storage demand (W h) total daily load (W h) water density (kg/m3) array conversion efficiency Coulomb efficiency pumping efficiency
age annual precipitation around 1850 mm (Guilan Meteorological Administration, 2012). It should be noted that the average annual precipitation in Iran is around 236 mm (Guilan Meteorological Administration, 2012). Having enough water, fertile lands and rather high relative humidity make Guilan province one of the main sources of producing rice in the country. More than 205,000 ha (0.5 million acres) of this province, which is 35.81% of the total paddy fields of Iran, has been cultivated with rice. In this region, the usual irrigation method is flood irrigation which continues from the beginning to the end of the growing season and the conventional method of cultivation is wet tillage with manual transplanting (Mostafazadeh-Fard et al., 2010). These flooded rice fields have different sizes about 200 m2 up to several hectares. Fossil fuel price fluctuations and cutting and gradually elimination of subsidies by the government have urged the farmers to use the other sustainable types of energy to power the farm pumping system. Moreover, because of limitation in water source, using of water saving irrigation systems rather than conventional system is an inevitable plan in the near future. Solar energy by using stand-alone PV panels is superseding the conventional pumping system. As stated before, this area has the lower sunny days than the other parts of the country so in this paper, the PV system is designed just for use in the sunny months when the energy usage for irrigation fields increases. In the following sections, some climatologically aspects of the Guilan province, paddy fields description, water requirement and the conventional pumping system are presented. The measured global solar irradiance is studied and compared with EU PVGIS data. In addition the daily average clearness index is computed. The lifecycle costs method is used to compare the conventional and PV pumping system economically.
2. Field and pumping description 2.1. Field and climatologically characteristics Fig. 1 illustrates Caspian Sea, Guilan province and its location in Iran. The Alborz Mountain range separates the Iranian plateau from the Caspian Sea and the Safidrud river crosses through the mountains and flat plain and enters into the Caspian Sea near the city of Rasht, the capital of Guilan province. Guilan has several synoptic meteorological stations. One of them is located at Rasht with lati-
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Fig. 1. A schematic view of Guilan province and its location in Iran.
tude 37.15°N, longitude 49.36°E coordinates and 6.9 m above sea level named Agriculture station. This station has collected data from 1956 CE until now. To find out a crude estimation of the climate condition of this region, some selected data of this station are shown in Figs. 2–4. Fig. 2 shows the variation of monthly average daily temperature. In the hot months, the average daily temperature reaches to 25 °C, although the maximum monthly average temperature of 32.9 °C has been recorded at 1975, July (Guilan Meteorological Administration, 2012).
Fig. 3 presents the average relative humidity in Rasht (Guilan Meteorological Administration, 2012). The minimum value is around 74% in the hottest month of summer. Rather high value of the average relative humidity is one of the main characteristics of this area and is essential for rice to grow. Fig. 4 illustrates the investigation of total amount of precipitation (Guilan Meteorological Administration, 2012). The heavy rainfall in the fall, winter, and early of spring is collected in some natural reservoirs. This water is used as a source of water supply for irrigation during the irrigation period. This precipitation
Fig. 2. Average of daily temperature, Average value from 1956 to 2005.
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Fig. 3. Average of relative humidity from 1956 to 1991.
Fig. 4. Average of total precipitation, average value from 1956 to 2005.
amount guarantees the existence of required amount of water for irrigation during springs and summers. Fig. 5 presents the average recorded sunny hours (Guilan Meteorological Administration, 2012). As it can be seen, the sunny hours increase in spring and summer with an average 5.81 h per day. This is in accordance with the supposed daily working hours of pump in the next sections. To be more specific, Fig. 6 shows the details of the sunny hours and rainfall during the irrigation period in 2015 CE (Guilan Meteorological Administration, 2012). There are 82 days with the sunny hours more than 6 h per day. Moreover, the number of days with a minimum of 10 mm rainfall is 13 days. The number of the fully cloudy days, i.e. no sunshine and no rainfall, is 20 days with a maximum 4 consecutive days. In this study, a 5000-m2 rice field has been considered to study. It is located near to the Rasht and there is no grid line in the vicinity.
2.2. Water requirement Rice water consumption is high in growing period. According to the international rice research institute there are no data available on the amount of the irrigation water used by all the rice fields in
the world (Bouman et al., 2007). Yoo et al. (2012) proposed the following expression for net irrigation water requirements (NIWR):
NIWR ¼ ET C þ DP EFR
ð1Þ
where ETC is the crop evapotranspiration (mm), DP is the deep percolation (mm) and EFR is the effective rainfall (mm). The crop evapotranspiration can be determined by using reference evapotranspiration (ET0) and crop coefficient (KC) as follows:
ET C ¼ K C ET 0
ð2Þ
In Eq. (2) KC is a dimensionless parameter that is related to the crop water consumption. FAO exclaimed the amount of rice crop coefficient equal to 1.2 (FAO corporate document repository, 2016). Tyagi et al. (2000) obtained the rate of rice crop coefficient equal to 1.29. Although the most rate of crop coefficient is expressed by Mohan and Arumugam (1994) equal to 1.65, for dry season’s rice. Reference evapotranspiration (ET0) can be determine by climate and whether characteristics. Dinpashoh (2006) expressed ET0 for capital of Guilan province, Rasht, in the irrigation period. For more details, see Table 1. Deep percolation is determined by Plusquellec (1996) for Guilan province. According to his investigations, daily rice deep percola-
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Fig. 5. Average sunny hours, average value from 1956 to 2005.
Fig. 6. Daily sunny hours and rainfall for irrigation period, 2015.
tion changes between 1.6 mm/day to 9 mm/day for Fuman city (close to the Rasht) in the most permeable areas. In the next step, effective rainfall (EFR) can be determined according to total rainfall (Rtot ) by Smit et al. (1992) approximation which is expressed as follow:
EFR ¼ 0:6Rtot 10 for Rtot < 70 mm=month
ð3Þ
EFR ¼ 0:8Rtot 24 for Rtot P 70 mm=month
ð4Þ
In this study, the Dinpashoh (2006) value for ET0 is used for determining ETC by consideration crop coefficient equal to1.65 (Mohan and Arumugam, 1994) (the highest water consumption value among the reported data for K C ). Rice deep percolation is considered 5.45 mm/day (mean of the maximum and minimum
rates of percolation depth reported by Plusquellec (1996). Details of the rice water requirement are demonstrated in Table 1. In Guilan province, rice irrigation is carried out arbitrarily at a time between April to May. Hence, two states are considered and studied for determining the net rice water requirement in which in the first state irrigation is started in April and finishes in August. Also in the second state, irrigation begins in May and it is stopped in September.
2.3. Pumping power requirement The required pumping power for irrigation relies on several parameters such as pumping head, suction head, pipes length,
Table 1 Mean monthly rice water requirement in irrigation period (mm).
April May June July August September
ET 0 Dinpashoh, 2006
KC
ETc
DP
Rtot (Guilan Meteorological Administration, 2012)
EFR
68 112 154 169 148 105
1.65 1.65 1.65 1.65 1.65 1.65
112.2 184.8 254.1 278.8 244.2 173.2
163.5 169 163.5 169 169 163.5
63.5 54.3 44.7 42 71.4 157.4
28.1 22.6 16.8 15.2 33.1 102
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and volumetric flow rate. Eq. (5) shows the pumping power as a function of some important parameters (Kelley et al., 2010):
PP ¼ qghQ=gP
ð5Þ
where PP is the pumping power (W), q is the water density (kg/m3), g is the gravitational acceleration (m/s2), h is the pumping head (m), gp is the pump efficiency, and Q is the required volumetric flow rate (m3/s). Table 2 shows some general information about the irrigation time and other parameters related to pump in two states which will be used later. From Table 2 it can be concluded that the maximum required water for rice paddies in Guilan province fields is 11.7 mm/day for irrigation started in April. Pumping head is determined as for pipe friction losses 5 m length by 1.5 in. diameter. The higher rate of insolation increases the rate of water evaporation. On the other hand, the greater rate of water evaporation results the higher power for irrigation because of increasing pumping hours. Meanwhile with a greater rate of irradiance, the more energy will be achieved by PV panels. Therefore, there is a coincidence between the peak of required power for irrigation and peak of received solar energy. This fact is an important advantage of solar irrigation systems. 2.4. Conventional pumping system The conventional pumping system employed a gasolinepowered motor-pump to irrigate the paddy. Table 3 shows the considered pump’s characteristics (Robin Industrial Engines, 2012). This pumping system is an on-off system. It means the pump has to work during a required time interval, which in this case is four to six hours per day. The irrigation hours strongly depends on the stage of the rice growing. An energy review reveals that just the pumping system is the main energy consumer in this filed. Fig. 7 shows a schematic of the paddy, the natural reservoir, and the gasoline pumping system. 3. PVPS design In this section, some important aspect of the PV pumping system is discussed. The daily-average measured global solar irradiance, the tilt angle, PV panels sizing and the required pumping system are investigated. Fig. 8 illustrates a general schematic of the PVPS. 3.1. Solar irradiance Fig. 9 shows the albedometer which is used to record global irradiance in the Rasht synoptic meteorological stations (Guilan Meteorological Administration, 2012). The albedometer model is CMA6 which is constructed around two CMP6 pyranometer sensors manufactured by Kipp and Zonen, the Netherland. The spectral range of this device is from 285 to 2800 nm, sensitivity is 5 to 20 mv/W/m2 and its response time is less than 18 s. The crude pyraTable 2 Details of two state irrigation beginning.
Irrigation beginning time Irrigation period (days) Sum of ETc (mm) Sum of EFR (mm) Sum of DP (mm) Net water requirement (m3 =ha) Pump efficiency % Pumping head (m) Power requirement (W)
State 1
State 2
April 153 1074.1 115.8 834 17,923 0.6 3 132
May 153 1135.1 189.7 834 17,794 0.6 3 128
Table 3 Characteristics of a conventional pumping system (Robin Industrial Engines, 2012). Model
Robin EY15D
Continuous rated output (HP/rpm) Cooling system Lubrication/Lubricant
2.2/3000 (1.64 kW) Forced Air Cooling Splashing type/automobile oil class SC Automobile gasoline 280 (0.832 L/h) at continuous rated output 600
Fuel Fuel consumption ratio (g/HP h) Continuous delivered volumetric flow (L/min)
nometer data are analyzed with respect to other data like daily sunshine hours. These data represent the sum of direct, ground, and diffuse reflected irradiance in 2015. Fig. 10 presents the data of maximum and average daily global solar radiation. The highest values of 1060 and 441.7 W/m2 in maximum and average data are recorded in June 10 and July 30, respectively. Table 4 presents the monthly mean daily values of global solar irradiance in Rasht (Guilan Meteorological Administration, 2012). These data are compared with EU PVGIS data (European Commission Joint Research Center, 2012) which are calculated from satellite data for a period 1999 up to present in 30-min time-step. According to Table 4, the average peak sunny hours are equal to 6.08 kW h/m2/day and 6.17 kW h/m2/day for irrigation period began in April and May, respectively. As it was remarked earlier, there are some fully cloudy days in this region, so calculating the daily average clearness index is necessary. This parameter is defined as the ratio of the global solar irradiance at the surface falling on a horizontal plane by the corresponding extraterrestrial irradiation on a horizontal plane for the sometime period (Markvart and Castaner, 2003). Fig. 11 shows the values of mean monthly clearness index from 2010 to 2015 for Rasht city (Guilan Meteorological Administration, 2012). This data are compared with the Islam et al. (2009) data in Abu Dhabi. The results of the Islam et al. (2009) investigations are also reported in Table 5. According to the Table 5 and Fig. 10, though the annual scale between Rasht and Abu Dhabi (that has a strong potential for solar energy capture) is different, but in six months of irrigation period, mean monthly clearness index values are very close together. This average value of clearness index in irrigation months indicates that Guilan province is a good candidate for using PVPS system.
3.2. Solar panel tilt angle Tilt angle is one of the most important parameters in gaining solar energy by PV panels. It depends on the many parameters such as season, location, PV capacity, and climate. Kaldellis and Zafirakis (2012) investigated the optimum value of the tilt angle in nearAthen regions, experimentally. They reported that for summeronly applications the optimum tilt angle is 15° ± 2.5. AslSoleimani et al. (2001) worked on the optimum tilt angle experimentally for Tehran, the capital of Iran. Results show that a small tilt angle around 0°–5° is preferable in summers especially for irrigation pumping. Due to close latitude between Rasht and Tehran, in the present work the tilt angle is assumed to be around 5° ± 2.5. The tilt angle variation from 0° to 23°, showed a slight variation in energy achieved by PV panels, (less than 5%) AslSoleimani et al., 2001. Thus, the horizontal albedometer data are used for recording the solar irradiance.
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Fig. 7. A schematic of the paddy, the natural reservoir, and the gasoline pumping system.
Fig. 8. A general schematic of the PVPS.
Fig. 9. Two view of Rasht metrological albedometer.
Fig. 10. Data of daily maximum and average global irradiance, 2015.
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Using Eq. (6) and according to the suggested centrifugal pump specifications, panel area for satisfy two states of irrigation periods is calculated about 2.7 m2.
Table 4 Monthly mean daily of global solar irradiance. Month
January February March April May June July August September October November December
Global solar irradiance, kW h/m2/day Present study (Guilan Meteorological Administration, 2012)
EU PVGIS data (European Commission Joint Research Center, 2012)
2.52 2.73 4.72 4.69 5.58 7.10 6.69 6.37 5.10 3.84 2.58 2.12
2.05 2.71 3.69 4.97 6.28 7.04 6.76 5.99 4.66 3.32 2.16 1.84
3.5. Storage system designing It is common in designing PV systems to store excessive energy into the some batteries. The excessive energy is stored in the battery to provide electricity for cloudy day’s irrigation. Indeed, there will be some cloudy days during the irrigation period. So to overcome the loss of sunshine, the paddy should be irrigated by the battery storage. The storage demand can be determined by following expression (Zobaa and Bansal, 2011):
SD ¼ ðTDL NNSDÞ=gcoulomb
3.3. PV power station sizing Estimation the size of the PV panel area is related to the continuous power that is needed in the pumping system. In Eq. (6) the relation among panel area (m2), continuous power (W), peak solar radiation (W/m2) and selected PV panel’s efficiency is given (Kelley et al., 2010):
APV ¼ PP =ðIP gA Þ
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ð6Þ
In this study the LG220P1C is used for solar panel. The specifications of the selected panel are provided in Table 6.
ð7Þ
where SD is the storage demand (Wh), TDL is the total daily load and equal to 1.2 times of total daily energy (Wh), NNSD is the number of no sunny days and gcoulomb is the coulomb efficiency which is usually taken as 0.8 (Zobaa and Bansal, 2011). Fig. 12 shows the number of the consecutive no sunny days from 2010 to 2015 (Guilan Meteorological Administration, 2012). According to Fig. 12, five years average of this parameter varied from 1.33 for June to 5.5 for January. In this investigation this parameter is intended 4 days consecutive for irrigation period. The battery storage demand (SD) for two irrigation states began in April and May is calculated equal to 4815 (W h) and 4739 (W h), repectively. Table 8 shows the selected battery details (Trojan Battery Company, 2013). As stated before, there should be enough land in the field to put the PVPS facilities like PV modules, battery, inverter and other equipment on it.
3.4. Motor-pump system 4. Economic analysis The motor pump unit in the PVPS is a centrifugal AC motor pump unit. Its characteristic is shown in Table 7 (PEDROLLO Distribution Ltd, 2016). Selected pump is determined according to the power requirement and pumping head. This pumping system is widely used in irrigation applications.
The lifecycle costs of both conventional pumping system and PVPS are studied in this section. This method is widely used to compare the renewable system versus conventional ones (Kelley et al., 2010; Cloutier and Rowley, 2011; Senol, 2012). All prices
Fig. 11. Values of clearness Index: monthly average values from 2010 to 2015.
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Table 5 Comparison of clearness index between Rasht and Abu Dhabi from 2010–2015.
Rasht Station (Guilan Meteorological Administration, 2012)
2010 2011 2012 2013 2014 2015
Abu Dhabi (Islam et al., 2009)
Six months irrigation period
Annual
0.57 0.54 0.56 0.55 0.57 0.56
0.5 0.48 0.49 0.49 0.48 0.5
0.59
0.58
Table 6 PV Module characteristics (LG Electronics Company, 2016). PV Model
LG220P1C
Area (m2) Efficiency Pmax (W) Voltage in maximum power (Volt) Current in maximum power (A) Open circuit voltage (V) Short circuit current (A)
1.46 13.7 220 28.9 7.62 36.1 8.21
Table 7 Selected pump’s details. Type
Centrifugal pump HFm 50B
Factory Nominal power (W) Inlet diameter(in) Outlet diameter(in) Maximum volumetric flow rate (L/min) Maximum pumping head (m)
PEDROLLO 370 1.5 1.5 300 10
Table 8 Details of the selected battery (Trojan Battery Company, 2013). Model number
L16RE-B
Company Voltage (V) Amperage (20 h) (A h) Weight (kg) Chemistry
Trojan 6 370 54 Flooded
cant and worker’s payment for periodically checking. The motor pump unit is assumed to work for 10 years. After that it should be replaced with a new one. The fuel price for this pumping system is calculated based on no-subsidy price and according to one irrigation period with average working time of 5 h per day. Transition cost is all of costs for transference gasoline from gasoline station to the rice field. The one liter of gasoline is assumed to be constant and equal to 0.25 US dollar. Table 9 shows the details of the conventional system costs. 4.2. PV pumping system In the PV pumping system major costs, consist of the centrifugal pump, wiring, electronics, battery, and the installation. Repair and maintenance costs include equipment replacement, worker’s payment, security issues and salvage prices. The main electrical equipment, such as inverter assumed to work for 9 years. In addition the motor pump unit will work for 10 years because of working under a very humid situation. The battery storage will work for 10 years, too. Table 9 shows the prices for PVPS per year. 4.3. Lifecycle cost method
are converted to US dollar for simplification. It is obvious that if the lifecycle costs of PVPS are lower than the conventional system, the PVPS is economically feasible.
Lifecycle cost method uses the present worth factor (PWF) for comparison of the price of equipment during different years, and is defined by Eq. (8) Messenger and Ventre, 2003: n
PWF ¼ ð1 þ i=1 þ dÞ 4.1. Gasoline pumping system In Conventional pumping system, the major costs include motor-pump unit and installation of system. Repair and maintenance costs include equipment replacement such as oil filter, lubri-
ð8Þ
where i is the inflation rate, d is the discount rate and n is the number of years. Eq. (9) shows the present worth by assuming that, x = 1 + i/1 + d (Messenger and Ventre, 2003):
PW ¼ PWF:A0 ¼ xn A0
Fig. 12. Data for number of average consecutive no sunny days from 2010 to 2015.
ð9Þ
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M. Niajalili et al. / Solar Energy 150 (2017) 546–557 Table 9 Lifecycle costs of two pumping system. PVPS costs (US Dollar)
Conventional costs (US Dollar)
Major Costs
Panels Centrifugal Pump Battery Inverter and other electronics Installation
650 200 1400 450
Repair and Maintenance Costs
Cleaner labor plus security (per year) Electronic replacement plus maintenance (per year)
300
300 100
Oil filter, fuel filter, Lubricant oil replacement (per year) Maintenance labor (per year)
300
Fuel & transition cost Annual R and M plus Fuel costs
450 950
200
100
Annual R and M costs
400
Average discount rate Average inflation rate Total lifecycle cost
Gasoline Pump Installation
200
13% 13.75% 19766
Total lifecycle cost
30890
where A0 is the price of equipments in the present year. In the next step for accounting the fuel cost and other annual costs that is purchased at the outset of the year, used the cumulative present worth factor (CPWF) which is shown in Eq. (10) Messenger and Ventre, 2003.
CPWF ¼ ðð1 xn Þ=ð1 xÞÞ
ð10Þ
Then for accounting the annual cost that supply is purchased at the end of lifetime, used the cumulative present worth factor at the end of year (ECPWF) which is shows in Eq. (11) Messenger and Ventre, 2003:
ECPWF ¼ xðCPWFÞ
ð11Þ
In this paper, the annual fuel requirement cost and other annual costs for gasoline pumping system are assumed to be purchased at the beginning of the year. In the other hand, the PVPS annual cost is purchased at the end of the year. Hence, the net annual cost for PVPS (ACPnet) and gasoline pumping system (ACGnet) are expressed as follow:
ACPnet ¼ ECPWF ACP
ð12Þ
ACGnet ¼ CPWF ACG
ð13Þ
In this analysis, the average inflation rate per year assumed constant and equal to 13.75% (Cetral Bank of The Islamic Republic of Iran, 2016. The life time of both systems are considered to be equal, about 25 years. The average discount rate assumed to be around 13% (Melli Bank of The Islamic Republic of Iran, 2016; Maskan Bank of The Islamic Republic of Iran, 2016). A US dollar considered to be equal to 3500 Iranian Rials in this study. The price of common facility in both systems such as pipes is not included. Costs are divided into three parts: major costs, repair and maintenance, and fuel. Data is obtained from local people and construction companies by a query.
Fig. 13. Pumping power and PV area versus field area.
varies according to the required irrigation power and for this case the PV panel area should be 2.7 m2. This PV panel area dictates the farmer to select two pieces suggested PV panels (see Table 6) which can provide the maximum power up to 0.44 kW. As depicted before in Fig. 2, the average monthly temperature does not exceed 25.2 °C in hot months, which is an advantage of Guilan weather that makes it possible to get the maximum efficiency from selected PV.Table 10 shows the details of the solar design parameters in irrigation period in this study. According to Table 10, selected centrifugal pump and battery storage require two pieces selected PV panel and four pieces suggested batteries. Also according to Table 9, the total lifecycle cost for gasoline pumping system is around 1.56 times of the PVPS.
5. Results and discussion In this section, results are presented for both technical and economical aspects of the PVPS feasibility in Guilan province in Iran. Fig. 13 presents the required pumping power for paddy and the panel area according to the paddy area specifications. It is evident that as the area is increased, pumping system needs more power to handle the necessary irrigation water. For the case study, a 5000 m2 paddy, by assumed the selected centrifugal pump, the required pumping power is 0.37 kW. In addition the PV panel area
Table 10 Solar design parameter for irrigation period. Power requirement (W) Average peak sunny hours Panel area (m2) Battery capacity (W h) Field area (m2) Number of panel requirement (pieces) Number of battery requirement (pieces)
370 6.08 2.7 7559 5000 2 4
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ments. The authors also thank the Rice Research Institute of Iran for their valuable information about rice cultivation and water usage.
References
Fig. 14. Data of lifecycle cost estimation.
Fig. 14 shows the investigation of the lifecycle cost analysis for both PVPS and conventional pumping system. According to Fig. 14, the initial cost of the PVPS is about 7 times of the conventional pumping system. This is the main impediment in using PVPS in the paddies for irrigation. As it can be seen, after around 9 years the total costs of both systems would be equal. Therefore using PVPS is economically feasible and logical. Also Fig. 14 indicates that at the end of the 25 years irrigation period, the final costs of the conventional pumping are 1.56 times of the PVPS. It is worth to mention that, there should be enough land in the field to put the panel area on it. For this case study, the required area is assumed to replace with the conventional system. In the studied case, the paddy’s area is 0.5 ha and the required PV panel area is 2.7 m2, so certainly covering just 0.05% of paddy’s total area with PV panel, cannot have tangible effects on the rice production. This fact is also meaningful for larger paddies. 6. Conclusion Enough available water and solar irradiance are two important parameters for having a viable PVPS. The North of Iran, especially Guilan province, has a good potential to experience the sustainable and clean solar energy. Having enough precipitation, monthly mean solar irradiance of 5.92kW h/m2/day and the six year average clearness index of about 0.56, make Guilan a perfect place to employ solar irrigation. The main barrier is the relatively large initial outlay, although the lifecycle cost comparison with the gasoline pumping system shows the lower costs of the PV pumping systems. For the considered case study, a 5000-m2 rice paddy, the required PV modules area is calculated equal to 2.7-m2 to power a selected centrifugal pump system of 0.37 kW. Also, the economical comparison between PVPS and gasoline pumping system in 25 years period of irrigation reveals that in spite of high initial costs of the PVPS, it will reach to the conventional gasoline pumping system costs just in 9 years. Moreover, it is found that at the end of mentioned irrigation period, the final costs of the conventional pumping system would be equal to 1.56 times of the PVPS which implies the PVPS merriness for irrigation in Guilan province. Acknowledgement The authors would like to acknowledge Guilan Meteorological Administration for giving the crude data and their useful com-
Al-Karaghouli, A., Al-Sabounchi, A.M., 2000. A PV pumping system. Appl. Energy 65, 145–151
M. Niajalili et al. / Solar Energy 150 (2017) 546–557 Plusquellec, H., 1996. Guilan, a successful irrigation project in Iran. Irrigat. Drain. Syst. 10, 95–107
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Trojan Battery Company, 2013. Available in: