Solar Powered Smart Irrigation System

What is it about?

This system consists of a water pump and an automatic water flow system, controlled by a moisture sensor. Moisture sensor is used to measure moisture level in the soil and according to the obtained information, water pump is turned on or off. In addition to this, sensors for air humidity and temperature can also be installed. It is all powered by solar cells which are able to turn the energy from solar radiation into electricity.
To increase voltage output, solar cells are wired in series; to increase amperage output, solar cells are wired in parallel. A solar module is combination of solar cells wired together in series and parallel with the purpose of generating a specific current and voltage at a given level of irradiance. A solar array is composed of two or more solar modules.

Solar power is directly proportional to the level of irradiance available and there is a continual variation in its level due to changes in the level of irradiance available throughout the day.
The efficiency of this system can be increased with the tracking mechanism that is powered and controlled by two small independent solar modules. When both tracking modules are equally sun lighted, the electricity produced by them flows between the two modules and the main solar array remains stationary. When one of the modules is shaded, the electricity produced by the module remaining in sunlight flows to the tracking motor which turns the array until both tracking modules are again in equal sunlight. This way main solar array receives maximum of sun’s radiation.

With advancements in technology, the systems can be made more user-friendly. You can control the motor pump from a remote location using your mobile phone.



How it was before and why is it important?

It is very important to provide water for the crops, in order to make their growth more effective. Therefore the irrigation system is used in case of long periods without rain and deficiency of water in certain areas.

In the agricultural fields, it is difficult to control water pumps manually. Before, there should have always been someone to stay close to the fields and turn the pumps on and off. With the implementation of auto irrigation system, this process was greatly facilitated. It turns the water pumps automatically on and off according to the information it receives from the sensors.

In many countries in the world, the absence of electricity is the main issue and the solar power can be utilized to power the irrigation system. Solar cells are incorporated in the system in order to make it less expensive, cleaner and more efficient.

In many countries in the world the lack of water is big problem as well, and the resources are quite limited. By using the soil moisture sensor, system turns on water pumps only when the level of moisture drops below the certain preset value, so the water savings are significant.

Advantages:

  1. It makes irrigation possible in remote areas
  2. Is environment friendly
  3. No grid connection required
  4. No electricity bills to be paid
  5. No fuel required
  6. Is durable, requiring minimal maintenance


How can it be built?

The actual components and hardware requirement depend on the type of irrigation system, such as surface irrigation where water is moved across the surface of agricultural lands, localized irrigation like spray or drip or trickle system where water is applied to each plant or adjacent to it, and sprinkler irrigation where water is piped to one or more central locations within the field and distributed by overhead high-pressure sprinklers or guns.

The water is often pumped from a bore-well or stream into a storage tank or directly into the field. The solar-powered irrigation system has four main parts: moisture sensor, water pump, pump controller and solar panel.

Moisture sensor

Moisture sensor is used for the measurement of moisture in soil. There are many moisture sensors available in market, but they all work on the same principle of resistance change. Basically, moisture sensor is a metallic strip, and its resistance changes according to moisture level in soil. If moisture is high, resistance will be low and if moisture in soil is low, resistance will be high. Microcontroller is used to measure the change in resistance of moisture sensor. This change in resistance is used to turn on or off dc water pump with the help of the relay interfacing with the microcontroller.
Water pump

The pump has a motor running on electricity generated by the solar panel. DC motors are mostly used for small to medium applications. Most DC pumps run at 24 volts rather than 12 volts. Power of a motor is specified in either watts or horsepower (HP).

Solar pumps fall into two major categories, surface and submersible:
- Surface pump – it is usually installed above the water level which requires a suction lift. It is used to get discharge from an open well, pond or river where high flow and small head (height to which the water needs to be lifted to) are required.
- Submersible pump - this pump is basically a hermetically sealed motor. The whole assembly of submersible pump is submerged in the water to be pumped up. It is generally used for pumping water from small-bore wells, and is designed to fit inside the drilled bore. The well may be anywhere from a few meters to 550 m deep. But the deeper the well, the more powerful and expensive would be the system. Submersible pumps have the ability to lift water to a greater height. So these pumps are also used for water transfer applications from a canal to storage tanks or from an underground storage tank to an overhead tank.

Before buying a pump one should know the depth at which water is available, daily water requirement and type of irrigation system to be installed. You may also need to know the water flow rate and the total head of the pump.
Here is an example of how to use the performance graph of 1.5HP motor pump. To interpret the graph and the table, let us say input power from the solar array 400 watts and it is needed to lift the water to a height of 40 meters at a flow rate of 12 liters per minute. As per the graph below, one would need a 1.5HP pump-set with pressure of 56.88psi or 392 kilopascals (392kPa).




Pump controller 
There are two types of pump controllers: inverter and variable frequency drive (VFD). If an AC solar pump is used, an inverter becomes necessary to change the DC from the solar panels into AC.

The solar panel and inverter must be sized accordingly to accommodate the inrush characteristic of an AC motor.
Many solar DC pumps require a special controller if they are to be powered directly by solar modules (without batteries). The controller or linear current booster enables the pump to start and run in low light conditions during a cloudy day, or early morning and evening. With a battery power source, the controller may not be required at all for a DC pump.

A special controller may also be employed for converting 12-volt battery power to higher voltage to run the pump at top speed. The DC pumps are available from 12V to 48V with their initial torque varying from 12A to 96A.



Solar panel

The pumps are fitted with motors that receive energy from solar arrays. The nominal power of a solar module is expressed in peak wattage (Wp). The wattage of solar panels depends on the requirement and the motors used.
Detailed process of making the solar panel and connecting it to a water pump can be found here: http://www.instructables.com/id/Solar-Water-Pump/?ALLSTEPS
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