Energy saving tips for pumpsets

One of the largest single users of energy is agriculture, and within this field, the energy used for irrigation is quite significant. Approximate estimates indicate that ground water pumping requires more than 16x109 kwh of electricity and about 2,000 million liters of diesel oil annually.

The requirement of energy for pumping groundwater, can be reduced if the power for this purpose is used most efficiently, which implies designing an efficient well assembly and having an efficient pumping unit and using the pumped water in the most efficient manner in the field.

A preliminary analysis of energy used in irrigation suggests that 30 to 50 % of the total energy used could be saved through improved technology. i.e. more efficient valves pumps, proper design and construction of well and by better use of the water that is applied. Improper selection of pump, prime mover and well assembly, inadequate maintenance and faulty operation of the unit and other factors also contribute to the low efficiency of the system.

Causes of Low Efficiencies

• Undersized Pipes - If pipes of smaller diameter are used, the initial cost will be less but the frictional head loss and the operational cost will be more. On the other hand, if pipes of larger diameter are used, the initial cost will be more but the frictional head loss and thereby the operational cost will be less. The optimum diameter of the pipe will have minimum total cost i.e. the initial and the operational cost. The farmers, while selecting the pipe size, give consideration to the initial cost only without bothering about the extra operational cost which they have to pay every year by way of increased energy bill. It is a general practice that with 100x100 mm pump, the suction and delivery pipes of 100 mm diameter are used. The velocities in the suction and delivery pipes should generally be lower than that at the entry and exit of the pump.
• High Delivery Point - Large number of pumping units have extra-ordinary high delivery point. This is especially true for diesel units. Excessive height of delivery pipe causes extra energy consumption.
• Poor Fittings - The fittings provided by most of the farmers are very poor resulting in large losses and leakage. Head losses in a poor quality foot valves are high. Similarly the head loss in the sharp bends are also high. The farmers are mostly ignorant about the operational quality of the components.
• Inefficient Pumps - Field study has indicated that average efficiency of the pumps operated by electric Motors is 47% and about two third of the pumps are operating at efficiencies less than 50%. Similarly the average efficiency of the pumps with diesel engines is 56% and more than half have efficiency less than 60%. Some of the pumps are operating at efficiencies less than the optimum efficiency because the units are not operating in the high efficiency range of Q and H. This is due to improper selection of pumps and mismatching prime movers and due to inferior quality of the pumps being marketed. The selection of the pumps should be governed by the characteristic curves i.e. the efficiencies in the various ranges of Q and H valves. At the normal operating condition, the efficiency should be maximum.
• Faulty Prime Movers - The prime movers of the pumps should be of proper size. Generally farmers go in for higher capacity motors and diesel engines. Generally the foundations and the belt transmissions are in poor shape. The farmers should be properly guided to choose the suitable sized prime mover, provide proper foundation and belt transmission, and to select the pump so as to take advantage of high efficiency of the pump.

Energy conservation tips while using irrigation pumpsets

• Select right type of pumpsets
• The various pumps sets available in the market require different quantities of diesel for pumping water. Therefore, it is important to choose an ISI mark pump. There is a potential of about 25% to 35% improvement in the efficiency of these pump sets.
• The pump you select should be suitable for your well and your water requirements. It is not necessary that the pump that is good for your neighboring farm is good for you too. If you give the following information to an expert, he will be able to help you choose the right pump:
• The depth of your well.
• The area of your field.
• You should also select the right engine which makes the pump run at the right seed. For this, consult an expert. The engine you use should have sufficient horsepower (H.P.) to operate the pump. The expert can calculate the amount of power needed for your engine. It is always better and beneficial to go in for a well-known and good quality engine. Look for the ISI mark of quality on the engine.
• To ensure a high level of operational efficiency of your diesel powered engine, ensure the following:
• Engine should not emit too much smoke.
• Use the correct grade of lubricant recommended by the manufacturer.
• Engine should be fitted with an oil filter.
• Engine should have an air filter which should be cleaned regularly.
• Engine jacket cooling water should be warm.
• Foot valves -
• Farmers can save about 10% to 30% diesel by simply using a foot-valve with larger area of openings than the one with narrow area of openings.
• An efficient low friction ISI mark foot-valve, though slightly costlier, pays back fast the extra cost by saving a lot of diesel.
• The larger valve helps to save electricity / diesel because less fuel and power is needed to draw water from the well.
• Pipeline
• A rigid PVC pipeline, with bigger diameter saves energy.
• More diesel is required to pump water through small diameter pipes because it offers higher friction. If the pipe is bigger than the pump flange size, a reducer must be used.
• How a 20% decrease in diameter increases the friction 3 times: If, in place of 100mm (4”) pipe, an 80mm (3”) pipe is used, the loss due to friction for drawing the same quantity of water will be three times more, which will cause higher fuel consumption.
• Also pipes made of rigid PVC cause lower frictional loss as compared to pipes made of conventional galvanized iron. Such pipes thus help save fuel.
• The fewer the no. of bends and fittings in a pipe, more the electricity saves.
• The pipeline arrangement that has many bends and unnecessary fittings cause higher diesel consumption. Each bend in an 80mm (3”) diameter Pipeline leads to as much friction loss as an additional pipe length of 3 meters. Therefore, the fewer the number of bends and fittings in a pipe, the more the saving of diesel.
• Sharp bends and L-joints in the pipe can lead upto 70% more frictional loss than standard bends.
• Use good quality PVC suction pipe to save energy and save electricity up to 20 %.
• Transmission
• Do not use belts that are old and worn out. Such belts can slip or snap anytime, causing loss in the transmission of power and hence increased fuel consumption.
• Check points for efficient transmission
• Reduce the number of joints in the belt.
• Check and adjust belt tension frequently.
• Check alignment of the pump with the engine.
• A farmer can save 15 litres of diesel every month simply by reducing the pipe height by 2 m. The pump works more efficiently when it is not more than 10 feet above the water level of the well.
• Apply oil and grease to pump set regularly as recommended by the manufacture.
• To improve the power factor and voltage use ISI marked shunt capacitor of right capacity with motor. This will also save the electricity.
• Switch off the light of well in the day time.

Source : Petroleum Conservation Research Association

Related Resources

1. NREDCAP