Evaluation of energy consumption in the electric center pivot machines

Lopez S. M. , Mujica C. A. , Brown  M. O. and Castellanos C. L. Evaluation of energy consumption in the electric center pivot machines in the enterprise ‘s various crops Cuba ,Ciego de Avila.

Journal Agricultural Technical Sciences V. 21 no.4 San Jose de las Lajas October – December . 2012, Cuba.

Consumption of electricity in the pivot machines is determined by means of the variations of the operation  point between the characteristic curves of the pumps and the driving curve to determine the influence of the same respect to energy consumption and from this propose energy production indicators . Irrigation campaigns of 2006 to 2011 were considered in 5 pivot machines for 5 crops. The results showed that the groundwater levels ranged from 3 to 10 meters by varying the operating point of the pump 5 to 10 % of the design flow . There was an electricity consumption with low crop productivity, poor product management and operation of irrigation systems in some years. There is also a high power consumption not directly associated with the production process 5629 Kwh . , due to water loss in the towers, joints and sprinklers.

METHODS

The research was conducted in the Mixed Crops Enterprise ” The Cuba ” where are located the 5 electric central pivot machines. The area belongs to CA- hydrologic  sector 1-8 of the northern basin in the province of Ciego de Ávila . The center pivot machines analyzed  are in: Villa Corrales, Marichal Finca, La Piña, La Naranja, Lango Lopez. The hydraulic characteristics of this technology are : flow rates of 48-75 L / s , pressures 32-51 mca , Model Caprari pumps, installed pump power ( 34-104 kW. ) .

The most important crops that were irrigated during the study period ranging from year 2006 to 2011 was the cultivation of potatoes , beans, corn , sweet potato, guava. The analysis of monthly trends of static well levels was taken from surveys conducted by the Provincial Enterprise Utilization of Water Resources of Ciego de Ávila .

The procedure used to determine the consumption of water and energy in the center pivot machines, was based on the hydraulic characteristics and operation of the irrigation system considering as variables, the volume of water extracted per crops , changes in water level in the sector and the power of the pump according to the variations in the operating point .

RESULTS AND DISCUSSION

The investigation showed that the variation of the optimum operating point of the pump in the 5 machines ranged between 5 and 10% of design flow rate of the pump, causing a decrease in pump power existed when the static level declines and increased power of the pump when there was a sharp increase in the static water level in the well.  These changes in flow provoque variations in the Total water requirements applied to the crop and changes in energy consumption behavior of the system  and coincides with ( Tarjuelo , 2007).

Water is one of the fundamental elements in plants to increase their production and yields, but poor management of the irrigation system causes decrease yields, there are anomalies in the years 2006, 2007 and 2009 due to a high water consumption , resulting  the same in aquifer overexploitation causing an increase in electric power , and there is a proportionality in midle of 2009.

The correlation between the consumption of electric energy in terms of crop yields in irrigation systems has a coefficient of determination R2 = 0.8604 for a linear equation with a high power consumption not directly associated with production level 5629 kWh  product  of work in vacuum and water losses in the towers, seams, joints and sprinklers. Even persist center pivot machines with low crop yields and high water consumption rate .

After a general energy analysis for the 5 pivot machines, five energy production indicators are defined as follows: water consumption per produced tonne m3 / t, energy consumption per cubic meter of water ( Kwh./m3 ), energy consumption per unit area ( Kwh / ha . ) energy consumption per ton produced (Kwh / t ) fuel consumption per unit area ( L / ha). It should be noted that the gauge height ranged from 53-73 meters and influence energy indicators . The above results agree with those obtained by Blanco and Piña ( 2005) , Perez et al. (2009) and Camacho et al. (2010).

CONCLUSIONS

Groundwater levels in hydrogeological sector in the Mixed Crops Enterprise The Cuba ranged from 3 to 10 meters varying the operating point of the pump 5 to 10% of design flow .

There was an electricity over consumption with low crop productivity product to poor management and operation of irrigation systems in the years 2006, 2007 and 2009. There is a high power consumption not associated directly to the production level of 5 629 Kwh, due to loss of water in the towers, joints, downspouts and sprinklers.

Five new energy indicators for crop production analyzed in electric center pivot machines are deducted.

http://scielo.sld.cu/scielo.php?pid=S2071-00542012000400007&script=sci_arttext

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