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Solar Water Pumping for Center Pivot Irrigation

 

Location: South Africa

Application: Irrigation 

Size: 50 hectars 

Installation: 2013

Problem: In a desert in Africa, a large pivot system with a radius of 479 meters is used to irrigate 50 hectares of desert. The fuelcosts of operating this system are very high and increasing. The irrigation system is needed to use otherwise dead landfor agricultural purpose. Water is being sup- plied through an artificial canal from the Nile. At this point, Alfalfa is grownas feeding hay and harvested eleven times each year with the harvest sea- son exceeding 300 days. Until 2013, a 135kW diesel generator ran 22 hours per day to power the system. Diesel is priced at USD 0.45. In 2013, the localgovernment temporarily scaled back fuel subsidies resulting in significantly higher prices for petrol, diesel and liquefiedpetroleum gas. Increasing fuel prices, supply difficulties and un- certainty of future developments meant an alternativepower source had to be found in this off-grid area.

SOLUTION: Following efficiency and feasibility analysis, AE Photonics Ma- roc designed and installed a solarpowered system using LORENTZ pumps to replace the diesel-powered generator and AC pumps. The pivot speed isautomatically controlled proportional to water flow. Also, all motors required to move the pivot now are solar powered. In eleven hours the pivot completes one 360 degree turn, providing the required 3,300 m³ of water per day for partialirrigation. At startup, the PV array located at the center of the system can be cleaned by the pivot itself. This not onlymeans no longer relying on fuel and being independent from future reductions in subsidies, but also greatly reduced carbon emissions.

Pivot Tower wheelpaths: 9 Tower

Irrigated Area: 50 ha

Solar Generator: 525 x 200WP 150KWP

Pivot: 479m

Pump systems: 3X psk2 21

Flow rate: 3,300 mday

Artificial canal: 3km

System components: The system has been designed with three parallel pumps. Water is pumped from an artificiallycreated canal into the pivot system, at a pressure of 2.5 bar. Each pump is connected to the PV modules via a PSk controller.

Benefits:

  • Placing the solar array at the center of the pivot can take care of clean- ing the PV modules, resulting in even higherefficiency of the system and less operating costs for main- tenance.
  • Solar water pumping systems re- quire no This removes the ener- gy bill plus the time and cost of fill- ing fueltanks and having costly fuel deliveries to remote areas. Also, cuts of subsidies are no longer an issue.
  • Solar pump systems have few mov- ing parts which makes maintenance unnecessary and gives them a long life.These elements give this solu- tion a good return on investment and a best quality/price ratio in comparison to conventional pump- ing systems, especially for systems in remote
  • Solar energy is a clean and inex- haustible energy Solar pro- vides a long term reliable supply of energywithout producing any emis- sions. Use of solar energy preserves the environment and has no impact on humanhealth.

Adjusting the pivot’s speed and, if used, the fertilizer pumps’ perfor- mance to the flow of water allows preciseirrigation and fertilization of the irrigation area, all on solar power only.

Calculation of the Energy Cost and Financial Analysis

Table 1 compares the cost of opera- tion of diesel and solar powered irriga- tion systems. The solar solution is signif-icantly cheaper over a five year period, with 50 % costs savings per m³ of wa- ter. Even without taking into account the resale value for the diesel genera- tor, the return of investment for the so- lar solution is only 3 years.

The solar solution also provides certain- ty for future planning, as subsidies on fossil fuels may be scaled back,where- as solar power is unlimited and free.

The solar solution provides the cheap- est and most fixed known cost over five years of ownership.

 

Table 1: Comparison of Energy Costs

For: daily water requirements: 3,300 m3 

Energy source

Diesel

PV

Efficiency

30 %

100 %

Fuel energy content

9.29 kWh/l

-

Fuel consumed

500 l

-

Cost per unit

0.45 USD/l

0 USD

Fuel cost per day

225 USD

0 USD

Fuel cost per month

6,750 USD

0 USD

Fuel cost per year (300 days)

67,500 USD

0 USD

5 year cost

 

Fuel cost

337,500 USD

0 USD

Cost of fuel deliveries / refilling

30,000 USD

0 USD

Engine servicing / replacement parts

31,250 USD

0 USD

Typical Initial cost1

25,000 USD

250,000 USD

Total costs

423,750 USD

250,000 USD

Costs per m3

0.08 USD

0.04 USD

Return on Investment: 3 years.

 


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