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Power - Photovoltaic - Water pumping - 0.123 kW - Off-grid / Canada
Case study assignment
A rural cattle farmer from just north of Kingston, Ontario, Canada has contacted your solar company in an effort to solve his livestock watering problem. He has 50 head of cattle in a remote field, far away from grid power. There is a shallow well in the field and currently he is supplying water by a gasoline powered generator which powers an AC pump. He has to make a daily trip to the remote field to run the pump, which uses up one hour of his time. The field is only used seasonally from the beginning of May until the end of September.
Site information
You recommend the use of a 12 V DC diaphragm pump. This pump will be powered by a solar photovoltaic (PV) system which comes as a complete package designed for easy installation on site. The batteries and charge controller are contained in a weather tight, insulated, and vented metal box. The box has a pole mounted to its side which holds a rack-mounted 123 W PV panel.
The suction head is 2 m, drawdown 3 m, and the discharge head is 1 m. At these parameters the pump will run at approximately 15% efficiency and can deliver 15 l/ min. of water. The pump will fill a 1,000 gallon stock water trough and will be turned on and off by a float switch installed in the trough.
Financial information
The farmer is prepared to pay for the system upfront, and he may be eligible for a 50% Ontario Wetland Habitat Fund rebate, as well as a 3.4% Ontario Provincial Sales Tax solar rebate. Base the financials on 2% inflation/fuel cost escalation. The package price for this specific pump is $2,060 and installation of the unit costs $400.
The PV system is seasonally operated so it requires 5 hours of time annually to start up in the spring and winterize in the fall. The pump requires rebuilding every 5 years at $50, and the batteries will be replaced every 10 years at a cost of $240. The PV pump package has a life expectancy of 25 years.
Currently, the farmer is spending 1 hour a day at $10/ hour plus the cost of running the gas generator/pump at $0.85 per litre. Assume 15% efficiency for this pump also. There is a one time initial cost of $1,200 for the conventional generator and pump.
Prepare a RETScreen study, documenting any assumptions you make, and determine the financial benefit to the farmer.
Solution
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
Teacher's notes
Results
Quantum Renewable Energy installed a photovoltaic powered livestock water pumping system for a rural cattle farm just north of Kingston, Ontario, Canada. The original shallow well was put in place with the idea of using a cattle "nose pump" by which the cattle mechanically pump water by using their noses. Due to the yearly turn around on the cattle, there was not a long enough time to teach the animals to perform the task, and as a result the pump did not work. The farmer was losing one precious hour a day running the generator-powered water pump.
The PV pump provides a reliable pumping source with a rapid payback when the farmer's time is accounted for. The renewable aspect of the system also agrees well with the farmer's personal values.
There are a number of different agencies offering incentives for alternative watering systems. The incentives range up to 50% of the total system costs.
System description
The actual system used consisted of one Unisolar 12 V - 64 W unbreakable module. The charge controller was an ASC 10 A - 12 VDC with low voltage disconnect output for the pump. Two 6 V Trojan T105 deep cycle batteries are wired in series to provide 220 Ah at 12 V. The low voltage disconnect is absolutely necessary to prevent the batteries from being overdrawn in the case of a malfunction or heavier than anticipated water load. A float switch mounted in the trough controls the on/off operation of the pump. The pump used is a Shurflo 2088 - 12 VDC which has a good reliability track record in the recreational vehicle and boating areas. The pump intake has a check valve to keep its prime and a mesh screen to help filter out grit. The pump discharges into a 15 foot length of ¾ inch poly pipe which is clamped securely to the top of the water trough. The entire box and well head are protected from the animals by a fenced enclosure.
Lessons learned
Livestock - Water pumping - Photovoltaic, Ontario, Canada - Photo 1
Livestock - Water pumping - Photovoltaic, Ontario, Canada - Photo 2
References
Case study assignment
A rural cattle farmer from just north of Kingston, Ontario, Canada has contacted your solar company in an effort to solve his livestock watering problem. He has 50 head of cattle in a remote field, far away from grid power. There is a shallow well in the field and currently he is supplying water by a gasoline powered generator which powers an AC pump. He has to make a daily trip to the remote field to run the pump, which uses up one hour of his time. The field is only used seasonally from the beginning of May until the end of September.
Site information
You recommend the use of a 12 V DC diaphragm pump. This pump will be powered by a solar photovoltaic (PV) system which comes as a complete package designed for easy installation on site. The batteries and charge controller are contained in a weather tight, insulated, and vented metal box. The box has a pole mounted to its side which holds a rack-mounted 123 W PV panel.
The suction head is 2 m, drawdown 3 m, and the discharge head is 1 m. At these parameters the pump will run at approximately 15% efficiency and can deliver 15 l/ min. of water. The pump will fill a 1,000 gallon stock water trough and will be turned on and off by a float switch installed in the trough.
Financial information
The farmer is prepared to pay for the system upfront, and he may be eligible for a 50% Ontario Wetland Habitat Fund rebate, as well as a 3.4% Ontario Provincial Sales Tax solar rebate. Base the financials on 2% inflation/fuel cost escalation. The package price for this specific pump is $2,060 and installation of the unit costs $400.
The PV system is seasonally operated so it requires 5 hours of time annually to start up in the spring and winterize in the fall. The pump requires rebuilding every 5 years at $50, and the batteries will be replaced every 10 years at a cost of $240. The PV pump package has a life expectancy of 25 years.
Currently, the farmer is spending 1 hour a day at $10/ hour plus the cost of running the gas generator/pump at $0.85 per litre. Assume 15% efficiency for this pump also. There is a one time initial cost of $1,200 for the conventional generator and pump.
Prepare a RETScreen study, documenting any assumptions you make, and determine the financial benefit to the farmer.
Solution
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
Teacher's notes
- Assume that the farmer must provide water 7 days a week for the entire 5 month season. The current situation takes the farmer 1 hour a day @ $10/ hour for 5 months = $1,530 annually.
- No debt ratio is used since the total cost is paid up front by the farmer.
- The incremental cost of the PV system is calculated as the cost of the PV pump system minus the cost of the gas powered option. i.e. $2,460-$1,200 = $1,260.
- A potential 50% Wetland Habitat Fund was left out for these calculations, since the rebate is not guaranteed and the farmer needed a worst case financial picture.
- Method 1 analysis does not have entries for the periodic costs of pump rebuilding and battery replacement as outlined in the financial description of this assignment, however, Method 2 will let you enter this information in the Cost Analysis worksheet.
- Use 13,000 kJ/kWh heat rate for the gas generator engine.
- Using grid supplied power is not a feasible option for the foreseeable future.
- A battery based PV system does contain a few more components than a direct solar to pump system and therefore costs more. However, the battery based PV system is more easily expanded than a direct PV to pump system. For instance both an electric fence and pond aerator can be added to this system by adding 2 more batteries.
Results
Quantum Renewable Energy installed a photovoltaic powered livestock water pumping system for a rural cattle farm just north of Kingston, Ontario, Canada. The original shallow well was put in place with the idea of using a cattle "nose pump" by which the cattle mechanically pump water by using their noses. Due to the yearly turn around on the cattle, there was not a long enough time to teach the animals to perform the task, and as a result the pump did not work. The farmer was losing one precious hour a day running the generator-powered water pump.
The PV pump provides a reliable pumping source with a rapid payback when the farmer's time is accounted for. The renewable aspect of the system also agrees well with the farmer's personal values.
There are a number of different agencies offering incentives for alternative watering systems. The incentives range up to 50% of the total system costs.
System description
The actual system used consisted of one Unisolar 12 V - 64 W unbreakable module. The charge controller was an ASC 10 A - 12 VDC with low voltage disconnect output for the pump. Two 6 V Trojan T105 deep cycle batteries are wired in series to provide 220 Ah at 12 V. The low voltage disconnect is absolutely necessary to prevent the batteries from being overdrawn in the case of a malfunction or heavier than anticipated water load. A float switch mounted in the trough controls the on/off operation of the pump. The pump used is a Shurflo 2088 - 12 VDC which has a good reliability track record in the recreational vehicle and boating areas. The pump intake has a check valve to keep its prime and a mesh screen to help filter out grit. The pump discharges into a 15 foot length of ¾ inch poly pipe which is clamped securely to the top of the water trough. The entire box and well head are protected from the animals by a fenced enclosure.
Lessons learned
- A farmer's time is very valuable, so even a watering system with a cost of $3,000 can have a significant and rapid payback. A livestock watering system can encounter very severe weather as well as the wrath of a curious bull, so the system must be weather tight, durable and protected in an enclosure.
- Seasonal PV systems are easy to design due to the abundance of predictable solar resource available during the season of use. Winter operated solar watering systems are also possible but they require much more design with respect to freeze protection and solar resource and load matching.
- With the new Clean Water Act (Feb. 2006) now in place in Ontario, watering of livestock from open sources will eventually be restricted. There are seldom any options other than a solar powered pump. There will be a growing need for alternative livestock watering methods to provide for these situations.
Livestock - Water pumping - Photovoltaic, Ontario, Canada - Photo 1
Livestock - Water pumping - Photovoltaic, Ontario, Canada - Photo 2
References
- Kilborn, Ian, "Personal Communication," Quantum Renewable Energy, 2007.
- Rooney, Rick, "Personal Communication," Quantum Renewable Energy, 2007.
