Solar Water Pumping System Design

Solar Water Pumping System:-

Solar water pumping system is a combination of electrical tools which are connected together as per system requirement and use to extract water from inside the earth surface. the main equipment in the solar water pumping system are Solar PV Module, CC or S type hot deep galvanized ionized (HDGI) solar PV module support (solar module mounting structure),AC wire,DC wire,variable frequency driver,AC or DC submersible pump etc. In this context i want to said that solar water pumping system are suitable all those areas where electricity grid available like urban areas and also where electrical grid is not available like rural,villages and remote areas.

Why Solar Water Pumping System:-

If we talk about ancient times, at that time the source of irrigation tools are used to be river, pond, lake well etc. To get water from all these resources, used to be dhekuli, bucket wheel and wind powered windmills etc. The efficiency of all these resources was very low and the entire day time was spent in it.

After that, human make many changes in irrigation system. The changes are like that electrical motors, diesel engines etc.But these resources are also not the source of sustainable energy.Because all of these sources is also harnessed from conventional energy resources.

After all of the above, humans turned towards solar energy which is a source of sustainable energy.Solar energy is the source of renewable energy. Renewable energy sources are sources of energy that is constantly replenished through natural processes. These resources are often also referred to as alternative or renewable energy, mainly because they are a fuel option that can replace conventional non-renewable fossil fuels. Fossil fuels, like oil and coal, produce energy when they are burned, but their supply is limited because they don’t naturally replenish on a short enough timescale for humans to use.

Renewable Energy is the source of clean energy with versatile feature in favor of environment and human being . It is non-exhaustible type source of energy.

Renewable energies are ways to generate energy from unlimited natural resources. These resources are either available with no time limit or replenish more quickly than the rate at which they are consumed.

Our Indian Government is also focused on the solar energy sector, and promote various type solar energy systems like solar on grid system, solar off grid system and solar water pumping systems. For the encouragement of solar water pumping systems Indian government launch PM-KUSUM scheme (Pradhan Mantri Kisan Urja Suraksha evam Utthaan Mahabhiyan). Under this, solar pumps are installed or old pumps and farming other electric devices are connected to solar energy. An agency has been authorized in every state for financial assistance under the scheme. Applicants have to contact their state agency only.

☛ For more information regards PM-KUSUM scheme - Click Here

Design of PV powered DC Pump

A PV powered DC pump can be used for pumping out drinking water or for irrigation purpose. If water is required for night time ,then there are two options. One is the electrical energy stored in the batteries during the day time which is used to drive the pump in the night time.And second option is that need for the battery storage can be completely eliminated, if, instead of storing electricity in batteries for non-sunshine hours applications, water itself can be stored in tanks which is shown in below figure.Due to this reason, water pumping system is one of the most attractive applications of solar PV power.

In this case, the system can again be very simple wherein the DC motor is directly connected to the PV module.If the amount of water to be pumped is not a parameter then design of the solar PV powered DC pump system is very trivial.

One has to simply match the power and voltage rating of the pump and that of the PV module.If this is done,whenever sun will the shine, the pump will run and you will get some water out, mostly. In many cases, this design will work if the designer has seen the pumps at different power ratings in operation and has some idea of the amount of water discharge, well depth and pump rating.

The description of the operation of the PV powered DC system and discussion on consideration for various design parameter ( inclusion of MPPT circuit, cost versus performance, etc.) applied to PV powered DC pump as well. At this point, it is important to note that AC motors of various power capacities are also readily available in the market and one can design a PV powers AC pump.

In above case, the DC motor is replaced by an AC motor, and an inverter circuit ( DC to AC converter ) is inserted between the solar PV module and the motor. The inverter circuit's power rating should match with that of the motor and the PV panels.

Solar PV water pumping system design for Specified Daily Water Requirement:-

The over all design can be divide in to 5 steps, which is given below:

Determine the amount of water required on daily basis.
Determine the total dynamic head (TDH) for water pumping.
Determine the hydraulic energy required per day to pump the required amount of water.
Determine the solar radiation available at given location (1000 watt per meter squire).
Determine the size and number of solar PV modules required, which motor to use, and the motor rating taking in to account the motor efficiency and other losses.

Now

We are going to design Solar Water pumping system, which is required to draw 50,000 Liter of water every day from a depth of 10 m.

Amount of water to be pumped per day = 50,000 liter or 50 metric cube
Acceleration due to gravity = g = 9.8 m/s²
^{Solar PV module used = 150 Wp}
^{Operating factor = 0.75 ( PV panels, in general, do not operate at their rated peak power}
^{Pump efficiency = 30% or 0.30 (Its typically between 0.25 to 0.40)}
^{Mismatch factor = 0.85 ( PV panels usually do not operate at maximum power point, should be 1 if MPPT circuit is used)}
Water density = 1000 kg/m³
Total vertical lift = 12 m

5m elevation

5m standing water level

2m draw down

Step.1 Determine the total daily water requirement

Daily water requirement = 50,000 Ltr

Or 50 m³/day

Step.2 Determine the total dynamic head

Total vertical lift = 12 m

Friction losses = 5% of the total vertical lift

= 12 X 0.05 =0.6 m

Total dynamic head = 12+0.6 = 12.6 m

Step.3 Determine the hydraulic energy required / day

Hydraulic energy required to raise water level

= Mass X g X TDH

=Density X Volume X g X TDH

=1000 Kg/m³ X 50 m³/ay X 9.8 m/s² X 12.6 ( Multiplied by 1/3600 to convert seconds in hours.

= 857.5 WH/day

Step.4 Determine solar radiation data

= 6hrs / day (peak of 1000 w/m² equivalent), actual day length is longer

Step.5 Determine the number of PV panels and pump size

Total wattage of PV panel = total hydraulic energy / No. of peak sun shine hrs.

= 1,715÷6

= 285.83 W

Considering system losses= Total PV panel wattage ÷ pump efficiency X mismatch factor

= 285.83 ÷ 0.3 X 0.85

= 1,120.90 W

Consider operating factor for PV module

= Total PV panel wattage after losses ÷ Operating factor

= 1,120.90 ÷ 0.75

= 1,494.53 W

Number of solar PV panels required of 200 Wp each

= 1,494.53 ÷ 150

= 9.96 approx. 10 Module

Motor Rating of The Motor = 1,494.53 ÷ 746

= 2HP motor

If the MPPT circuit is to be used in the design, we should also specify its power rating. The MPPT circuit normally uses a DC to DC power converter.

Power rating of DC to DC power converter =typically 30% higher than the motor rating

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Author Description

Solar Energy Tak