Feasibility of Solar Powered Pumping Systems for Deep Tubewells in Pakistan

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Council May 2011 Natural Resources Division,

1 Feasibility of Solar Powered Pumping Systems for Deep Tubewells in Pakistan Dr. Shahid Ahmad and Irfan Ali Natural Resources Division Pakistan Agricultural Research Council May 2011 Natural Resources Division, Pakistan Agricultural 1 Research Council, Islamabad, Pakistan

2 Motivation Feasibility of Solar Powered Pumping Systems for Deep Tubewells in Pakistan Dr. Shahid Ahmad and Irfan Ali NRD-PARC (Natural Resources Division of Pakistan Agricultural Research Council) during late 2008 identified issues of water scarcity, rising tariff of electricity and increased prices of fossilfuel (diesel) for planning future research agenda. Extended load shedding, voltage fluctuations and power failures have forced farmers to shift to diesel prime-movers. But recently in 2011, the higher rise in diesel prices has forced farmers to ask for alternative sources of energy for pumping groundwater. Higher cost of pumping groundwater has affected profitability of irrigated agriculture. Hundreds of farmers contacted NRD and made queries regarding alternate energy sources. Solar and wind energy require higher capital investment and it is currently beyond the reach of farmers until these are linked with energy efficient pumps and drip irrigation. Drip irrigation is the only option where one can afford the use of solar energy for areas where shallow groundwater is available. For deep wells of Balochistan and other areas outside the Indus basin, deep well pumping is now uneconomical both with electric power and diesel fuel. Feasibility of solar powered pumping systems is required especially for deep wells in conjunction with drip irrigation. The current briefing is aimed to provide feasibility of capital cost of solar powered pumping systems for deep wells and options for cost-effective development of solar powered pumps in Pakistan. Currently, there are over 1.0 million diesel operated pumping systems in the country, as per Pakistan Agricultural Statistics, The farmers owning these systems even in shallow groundwater areas will face serious problem of cost-effectivity of pumping systems with rising prices of diesel fuel. Over deep tubewells in Balochistan are performing due to heavy subsidy on electric tariff. The provincial government is facing difficulty in providing subsidy and after the 18 th Amendment; the federal government may not be in a position to share 40% of the subsidy and WAPDA 30% of the subsidy. If 70% subsidy load is transferred to the province, it will not be possible for the provincial government to allocate this huge resource for the subsidy on electricity. Important to mention, that the amount of annual subsidy on electric tariff for tubewells is more than annual ADP of the province of Balochistan. The future option is to develop fractional tubewells linked with drip irrigation to keep the initial capital cost as low as possible. The past claims have been largely for very small discharge solar pumps designed for domestic water supply pumping shallow groundwater. Claims for low cost solar systems yet have to prove their worth for agricultural purposes. 1. Solar Powered Deep Well Pumping System Conventional Systems Conventional electric powered centrifugal pumps for deep wells are named as submersible pumps and the same are now being used with solar energy. The modern submersible pump is not energy efficient (Figure 1) compared from the world s energy efficient direct displacement pumps normally used for pumping oils. Two options have been developed for pumping groundwater using solar powered submersible pumps and are given as under: Option #1: 7 to 8 litres per second discharge which is equivalent to a 3 inch delivery tubewell flowing full and with pump setting depth of 250 feet 2

Option #2: 3 to 5 litres per second discharge which is equivalent to a 3 inch delivery tubewell flowing partially or full with 2.5 inch diameter pipe and with pump setting depth of 500 feet Figure 1.

3 Option #2: 3 to 5 litres per second discharge which is equivalent to a 3 inch delivery tubewell flowing partially or full with 2.5 inch diameter pipe and with pump setting depth of 500 feet Figure 1. Solar powered submersible pump (Courtesy: Vortex Engineering Services, Islamabad Pump Characteristics for Option #1 There is variation in discharge of solar powered pump unlike of the pump operating with electricity or diesel fuel. The large variation in discharge from 8 to 26 m 3 /hour is primarily due to variation in light intensity. The solar output is directly a function of light intensity as the photovoltaic cell operates on the principle of light intensity (Figure 2). Figure 2. Variations in discharge of solar pump at 250 feet pump setting (Courtesy: Vortex Engineering Services, Islamabad 3

4 Pump characteristics in terms of power input, discharge and pump setting depth are given in Figure 3. Changes in power availability affect the discharge. Figure 3. Pump characteristics in terms of power availability, discharge and pump setting depth (Courtesy: Vortex Engineering Services, Islamabad Figure 4. Relationship of current and voltage for the solar pump (Courtesy: Vortex Engineering Services, Islamabad 4

1.2. Pump Characteristics for Option #1 There is variation in discharge of solar powered pump unlike of the pump operating with electricity or diesel fuel.

5 1.2. Pump Characteristics for Option #1 There is variation in discharge of solar powered pump unlike of the pump operating with electricity or diesel fuel. The large variation in discharge varying from 1.2 to 8.7 m 3 /hour is primarily due to variation in light intensity. The solar output is directly a function of light intensity as the photovoltaic cell operates on the principle of light intensity (Figure 5). Figure 5. Variations in discharge of solar pump at 500 feet pump setting (Courtesy: Vortex Engineering Services, Islamabad Pump characteristics in terms of power input, discharge and pump setting depth are given in Figure 6. Changes in power availability affect the discharge. Figure 6. Pump characteristics in terms of power availability, discharge and pump setting depth (Courtesy: Vortex Engineering Services, Islamabad 5

6 Pump characteristics in terms of power input, discharge and pump setting depth are given in Figure 7. Changes in power availability affect the discharge. Figure 7. Relationship of current and voltage for the solar pump (Courtesy: Vortex Engineering Services, Islamabad Prices of Solar Pump The prices of these two options were collected from two reputable firms in the country providing imported systems. The prices of solar powered pumping systems can t be generalized or verified as the suppliers are asking for price without rationalization based on power and water discharge. The details of the prices for pumps for the two options as quoted by the firms are presented as under: Prices of Solar Pump by EBR Energy Pakistan Pvt. Limited Option # 1 Pump Discharge = 147 m 3 /day = 6.9 lps Pump Setting Depth = 250 ft Price (million Rs.) = 5.9 Option # 2 Pump Discharge = 70 m 3 /day = 3.3 lps Pump Setting Depth = 500 ft Price (million Rs.) = 6.9 6

7 Prices of Solar Pump by Vertex Engineering & Services Option # 1 Pump Discharge = 176 m 3 /day = 8.3 lps Pump Setting Depth = 250 ft Price (million Rs.) = 6.3 Option # 2 Pump Discharge = 101 m 3 /day = 4.7 lps Pump Setting Depth = 500 ft Price (million Rs.) = Cost Effectivity of Solar Pumps for Deep Wells Feasibility Scenarios The analysis of cost of solar powered submersible pumping systems for deep wells indicated that cost of these pumps will be between Rs. 6 to 7 million for: Pump discharge of 7-8 litres per second and pump setting depth at 250 feet; or Pump discharge of 3-5 litres per second and pump setting depth of 500 feet. The pump setting depth of 500 feet is common in Balochistan as drilling is being done almost over 1000 feet. This shows that maximum discharge will be equivalent to 3 inch tubewell. This is a high cost pumping system and outside the reach of the farmers and government is also not in a position to provide subsidy at so high level. Therefore, traditional solar powered pumping systems are not suitable for surface irrigation at all. The only possibility for demonstration and economic evaluation is to install a pump of 1.5 litre per second discharge at pump setting depth of 500 feet. This pump will provide 3 litres per second at 250 ft pump setting depth. The cost of this pump is expected to be around Rs. 2.5 million as a complete unit. At 250 ft pump setting depth the pump will provide drip irrigation to an orchard of 10 acres with 300 plants per acre. Whereas the pump of almost similar cost, at 500 feet pump setting depth, will provide drip irrigation to 5 acres of orchards with 300 deciduous plants in environments of Balochistan s highlands. The plants include apples, cherry, peaches, plum, etc. For almonds and olives the orchards area will increase due to low water requirement of these plants. 2. Jack Pump World s Energy Efficient Pump for Deep Wells 2.1. The Technology The weight balancing Jack Pump is the latest technology in lifting oil, gas or deep waters using solar power. In fact, the term lift does not truly apply, in that it does not "lift" fluid like the conventional pump. Looking at how the pump cycles with the standard rod pump and compare it with the new technology of the down-stroke pump. In the down stroke pump, there is a tubular barrel with a sealing plunger, which is slightly longer than the barrel. With the start of the up stroke, the traveling valve on the plunger is closed. The standing valve opens and fluid fills the barrel as the plunger rises. With the start of the down stroke the standing valve closes and the travelling valve opens. As the barrel is being filled with the plunger, the fluid is being displaced from the barrel through the plunger into the tubing string, which pressures up, opening the check valve on the flow line, pushing fluid to the tank. Instead of using horsepower to lift fluid, it uses the weight of the rods to displace it. On the next up stroke the fluid in the tubing is static (no fluid from the barrel is being added to the tubing) all it does to load the barrel. Load on the up stroke 7

and displace on the down stroke. The difference between the Down Stroke Pump and a standard pump is not when the standing and travelling valves open and close, those are the same.

8 and displace on the down stroke. The difference between the Down Stroke Pump and a standard pump is not when the standing and travelling valves open and close, those are the same. The key is when the fluid in the tubing is static (on the down stroke with a conventional pump and on the up stroke with a Down Stroke Pump) and what you are doing the work with, horsepower or rod weight. These pumps are basically designed for pumping oil from thousands of feet. Therefore, technology is globally tested for extremely deeper depths. The discharge of oil is much lower than agricultural wells. Therefore, the challenge was how to increase the discharge of Jack Pump for agricultural purposes Benefits of Jack Pump Technology The Jack Pump is the world s most energy efficient pump. Some of the benefits of the weight balancing Jack Pump are: Reduced horsepower requirements due to direct displacement of pumping groundwater and weight balancing. Lower electric and diesel consumption costs Higher pump efficiencies Can handle solids much better than a conventional pump. Better run times. Reduced rod failures. Can be made as weight balancing pump to further reduce energy requirement Modification of Jack Pump for Water Pumping Renewable energy is a potential source of energy for pumping water (domestic and stockwater) in areas where electricity is not available and supply of quality diesel fuel is also a major concern. Wind and solar energy can be used for pumping groundwater. An alternate system covering solar, wind and diesel operated prime-movers has been developed by WRRI-NARC using Jack pump during , which is energy efficient pump (Figure 8). Low cost wind mills can be used for direct pumping of water in areas having sufficient wind. Windmills are now locally manufactured and can provide a cost-effective mean of pumping groundwater to a depth of 150 feet (Figure 9). Figure 8. Jack Pump with alternate energy sources at WRRI, NARC 8

9 Figure 9. Windmill water pumping system (Coutesy: Marine Pvt. Ltd. Karachi) 3. Way Forward The way forward is to introduce solar powered drip irrigation systems for small farmers having orchards of 5-10 acres. The submercible pump should be energy efficient having efficiency of 80% or more. These systems are now available in the market. The point for consideration is that the ultimate solution is to develop technology of Jack Pump, the direct displacement pump with weight balancing facility to pump larger quantities of water from deeper depths using alternate energy sources solar, diesel, electric, etc. The energy requirement is extremely low for this pump but its local manufacturing by a reputable firm is essential. PARC has tested this technology and found feasible for any available source of energy diesel, electric, solar, wind, etc. In fact, hybrid systems have to be developed because in certain days sunlight and wind might not be available therefore, electric or diesel fuel can be used. Initially these pumps are recommended initially for electric and diesel fuel and ultimately for solar. These pumps are economical with electric and diesel fuel. Although the technology was developed a decade ago, but the energy pricing is now such that there is now demand for an energy efficient pump. The development of technology is dependent on the demand. In the beginning, these pumps can be imported but for cost-effective installation idigenous development is essential. Jack pump is basicall an oil pump and pumping from deeper depths is well established in teh world. Only problem is that discharge has to be increased for agricultural purposes and pump is not suitable for shallow depths. PARC research was focussed on increasing discharge and testing for shallow depths. The pump tested at NARC is designed to pump litres per second at a shallow depth of 20 feet with 1 hp solar or electric prime mover and 3 hp of diesel engine. With traditional pumps atleast 8 hp diesel engine is required to pump litres per second or 0.56 cusecs, which is a medium size pump and commonly used in Punjab by small faremers. 9

10 Research Briefings Volume (3), No (18), 2010 The NRD Research Briefings is a Series of Issues, which are being prepared and circulated to the policy and decision makers, research and development experts, NGOs and private sector in the country with an objective to synthesize and disseminate the research outputs related to natural resources management research conducted by the establishments of the Natural Resources Division of PARC. The NRD Research Briefings was started during February 2009 to present outputs of studies undertaken by the Natural Resources Division of PARC and its research establishments including the MARC-Gilgit, AZRC- Quetta, AZRIs at D. I. Khan, Bahawalpur and Umerkot and national research institutes at NARC. The comments and suggestions can be sent at the following address: dr_shahidahmad2001@yahoo.com Phone No. (Office): ; Cell Numbers: Address: Pakistan Agricultural Research Council, P.O. Box 1031, Islamabad. The scientists and engineers of NRD and its establishments interested to get their papers published in these Briefings can send their files through . Reference: Ahmad, S. and I. Ali Feasibility of Solar Powered Pumping Systems for Deep Tubewells in Pakistan. Vol. (3), No. (18), NRD, PARC, Islamabad, Pakistan.

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