SCIENTIFIC SOLAR FARMING :Automated micro irrigation

SCIENTIFIC SOLAR FARMING

 Atul Kulkarni

Introduction

In recent decade increased emissions of GHGs into the atmosphere have a great effect on the Earth’s climate and have several consequences on agriculture due to changes in the geosphere and biosphere. One of the important consequences is variation in total rainfall and its seasonal variation which is critical for agricultural crops particularly in areas of rain fed agriculture which occupies greater proportion of agriculture land in India. In India nearly 65-70% of people are in rural areas and agriculture is the largest supporter of livelihoods to many of these people and thus climate change affects these rural farmers.

There can be multiple stresses on crops such as scarcity of availability of water resources, loss of bio-diversity and degradation of natural resources such as soil erosion, salinisation of irrigated areas, dry land degradation from overgrazing, over-extraction of ground water (FAO, 2003).

Impacts of climate change on irrigation water requirements are large. Since the temperature rises, evaporation of water will be more and water needed for crop irrigation will be more (IPCC AR4)

Current practices in irrigation

Presently, agriculture does not rely on primitive practices like cloud reading, age-old irrigation and sowing practices. Science has captured the minds of agriculturists like any other.

The major breakthrough happened when we no longer needed manual irrigation and they were effectively replaced with authentic pump sets, sprinklers, drippings etc. Electricity transformed the lives of millions of Indians and it had lots of positive impacts. Primarily in agriculture, it increased productivity, reduced manual labour and saved time.

The Green Revolution first looked like a savoir, increasing productivity by 200-300%. It was a radical concept of successfully utilizing fertilizers and insecticides. But all Indian agriculturists weren’t fortunate enough to exploit this idea. Post 50 years this irony still remains. The main reason for this was that many farmers didn’t have access to electricity and majority didn’t even have electricity to even light a bulb. Three-phase voltage was a distant dream. According to statistics from Eleventh Five Year plan, 40-50% of the agriculturists don’t have access to continuous electricity.

The immediate solution which felt appropriate was the installation of DG’s which run on motor spirit or gas oil. The spiralling crude prices meant no DG’s for the poor agriculturists. Farmers committed suicide, sold their lands or just went on with the manual irrigation. The result was high food Inflation and other such effects which affected the agriculture economy of India.

Automated Solar Irrigation

Automated Solar Irrigation is an innovation to address the above mentioned issues. It involves two phases. Phase-1 covers automatic plant irrigation and second phase deals with a solar driven motor. The motor used by our automatic plant irrigator to water the soil is driven by pure solar energy which makes it highly efficient and conservative.

This particular idea was designed and implemented in our engineering project where a complete working model was designed. Basically, it consisted of solar panels, for voltage, and electronic circuitry. These panels were coupled with high power pumps to irrigate the fields. The automation part is in the circuitry which is powered by the solar panels. Going by field surveys, we found that for a 10 acre plot required 5000+ watts of solar panel. The radiation from the sun reaches the earth’s upper atmosphere at a rate of 1366 W/m2. While travelling through the earth’s atmosphere 6% of the incoming radiation is reflected and 16% is absorbed resulting in peak irradiance of the equator of 1020 W/m2. General atmospheric conditions such as clouds, dust, pollutants further reduce radiation by 20% through reflection and 3% through absorption. Atmospheric conditions not only reduce the quantity of radiation reaching the earth’s surface but also affect the quality of radiation by diffusing the incoming light and altering its spectrum. For example, in South India, the average radiation at ground level over an entire year was between 120-350 W/m2 i.e. 3-9 kW/m2/day. This represents the available power and not the delivered power. Presently, photovoltaic panels convert about 15-20% of the incident light into electricity. A 2m * 1m dimension solar panel, on an average sunny day in Belgaum, will give around 40-60 W/m2.

A solar panel is nothing but a flat solar thermal collector. An array of photovoltaic solar cells used to generate electricity. An assortment of solar thermal panels which are connected in parallel or series based on requirement. The strategic placing of these solar panels is very important.

This model irrigates agricultural fields regularly not requiring any observation. The circuit comprises of sensor parts built using op-amp IC LM324. Op-amp’s are configured here as a comparator. Copper sensors are used for conduction measurement where two stiff copper wires are inserted in the soil to sense the whether the Soil is wet or dry.

Figure 1: Schematic Diagram of a Conductivity Sensor

The Microprocessor is used to control the whole system. It monitors the sensors and when more than two sensors sense the dry condition then the microprocessor will switch on the motor and it will switch off the motor when all the sensors are in wet and thus enabling automatic sensing process. The microcontroller does the above job after it receives the signals from the sensors, and these signals operate under the control of software which is stored in ROM.

All the power required for this setup is given by solar panels. A self explanatory circuit is given below.

Fig 2: Circuit for Solar Irrigation

The Microprocessor works based on the assembly language coded. The model was a 1 m * 1 m * 0.25 m soil box. Four copper probes were placed at strategic locations. A 65 W solar panel was used for pilot project. It generated 20V, 3A current when placed under direct sunlight.

The model used an Atmel AT89C2051 MP which is a high performance CMOS 8 bit processor that provides cost effective and flexible solutions to many embedded control applications. It is a low voltage device that comes with 2K bytes of flash programmable and erasable read and writes memory. It is manufactured using Atmel’s high density memory technology and is compatible with industry standard MCS-51 instruction chip. Based on our coding and operational requirement, microprocessor will get a signal in the form of current whether to ON or OFF the motor. A basic plug-in plug-out controller is used. That means there isn’t any flow control valve involved. However this concept can be used for advanced requirements. A pump is activated on receiving a signal from the relay.

Solar engine works as follows, the solar cell starts charging the capacitor and the voltage rises. As soon as the capacitor reaches around 2.7 V the 1381 turns pin 1 high and turns the 3904 ON. When the 3904 pin turns on, it brings the base of the 3906 low which turns the 3906 ON. With the 3906 ON current is supplied to the base of the 3904 which keeps it ON. Now current can flow through the motor and it starts running. When the voltage gets down to 0.7V the transistors turn OFF and the process is repeated.

Another important feature is that, two diodes are connected in reverse bias across the negative terminal of the panel. This incorporation does not feature in many solar circuit connections as this was our own enhancement. This is mainly used to avoid reverse currents and peak inverse voltage from the batteries connected which would damage the solar panel. We used a 12V rechargeable battery too. It can be directly interfaced with the panel. It will be charged by the panel itself.

Details of Pilot project

Consider a 1 acre plot in Suttagatti village near Belgaum, which receives considerable sunlight throughout the year. A solar panel should be mounted at 45 degrees with respect to the land level. Also, all the panels need not be kept at one place. They are mounted at a fair height above a piece of land of the entire plot. Then a solar panel of the required capacity are then fixed. Small areas will require smaller panels as they will be driving smaller pumps. This will save running cable cost and also loss of current. Submersible pumps can also be used. Permanent rechargeable batteries or high capacitive devices are used to store solar energy when pumps are not being run. These batteries can also be used if sunlight is low or during night.

A solar tracking device is installed to capture maximum sunlight. A solar tracking device is the one, which effectively rotates the panel based on the sun’s position. A handful of LDR’s are placed around the panel. LDR will show a voltage drop as its resistance decreases if more light falls on any particular resistor. A rotary motor is duly attached to the circuitry. Based on the input of the LDR, the motor rotates such that the solar panel gets face-to-face contact with the Sun. The position is determined by particular resistor which will give a drop. Thus the maximum productivity of the solar panel can be harnessed by following these innovative techniques. This system can irrigate any area with any type of farming or crop cycles. Since solar power is used, it would reduce irrigations costs to zero if done systematically.

This also leads to emission Reductions due to electricity saving in water pumping resulting from automated irrigation of farms, emission reduction due to usage of solar energy and emission reductions due to reduced use of agri-equipment & machineries. The total emission reduction per year per acre of land is estimated to be approximately 85 tCO2e/yr/acre.

Our focus is increase the livelihood of farmers, increase food productivity, increase nutritional value of food and reduce GHG emissions

Ecological Benefits

Help in improve agricultural productivity and food security.
Reduce the Green House Gases – GHGs and mitigate Global Warming

Social Benefits

Provides better livelihood opportunities for farmers who form large sections if society in rural. Improving social standard of farmers and brings in increased awareness and environment consciousness and benefits of naturally grown food under this technique.

Conclusion

In conclusion we re-emphasize that the negative impact of climate change in Agriculture can be taken care by innovations such as one presented here- automated solar irrigation and thus illustrate one of the techniques to mitigate climate change. The bottom line of any innovative technique/technology – should be socially, culturally acceptable, environmentally sustainable and should be economically viable. Even a great technology will not work if these are not taken care. This project takes these into consideration and one of the innovative techniques is presented in this paper.

References

  1. Pachauri, R. K., and Reisinger, A. (eds.) (2007), Climate Change 2007: Synthesis Report. Contribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, IPCC, Geneva, Switzerland, http://www.ipcc.ch/publications_and_data/ar4/syr/en/spm.html.

  2. FAO, 2003: Impact of climate change on food security and implications for sustainable food production committee on world food security. Conference Twentyninth Session, 12 to 16 May, Food and Agriculture Organization of the United Nations, Rome.

  3. FAO, 2000 : ‘Two essays on climate change and agriculture’

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