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Solar Water Pumps: Benefits, Options and Choosing Advice

Solar-powered water pumps for irrigation have become increasingly popular as agricultural activity largely occurs in the rural areas and away from the mainstream power grids. While individual consumers need alternative energy sources to reduce their electricity bills as well as environmental footprint, agricultural needs are even more critical. Let us discuss the benefits of solar water pumps in general and their particular efficacy in agriculture.

Developing the agricultural sector is of immense importance to the world economy. Research studies show that as of 2018, this sector was responsible for 4% of the GDP on average and its contribution went up to 25% in some of the developing nations. Therefore, it is vital that agricultural activities are not put at any risk because of climate change.

Solar Water Pumps for Remote Agriculture

The use of water pumps in agricultural irrigation

Water in agriculture

There can be no agricultural irrigation without water. Rainfed agriculture is only half as productive as irrigated agriculture per unit of land that is cultivated. Therefore, irrigated agriculture allows for better diversification of crops as well as increased production.

However, exploding population, climate change, and urbanization have become threats to the abundant availability of water, thereby impacting agricultural development. Since water usage in agriculture is so high, scientists are working on new technologies and techniques that will cut down this usage. With new technologies, it is estimated that 20-40% of that water could be diverted to other sectors in the next few decades.

This diversion or re-allocation can happen in two ways. The water can be moved physically by allocating the fresh water and groundwater resources to urban areas, and for industrial use. Water can also be moved virtually, by producing water-intensive foods and services that are usually in areas with plentiful water supply, and can be allocated to areas that face water scarcity.

Therefore, it is essential that the movement of water away from agriculture goes hand in hand with using water efficiently. Similarly, efficient water use and proper water delivery systems must be practiced in the agricultural sector. Solar-powered submersible water pumps will play a key role in achieving these goals.

What are fossil-fueled water pumps?

Water pumps need electricity to pump the water up into the pipes to irrigate fields. So it is, in the case of home use. There are many types of water pumps that use fossil fuels—centrifugal pumps, deep-well turbine pumps, submersible pumps, and propeller pumps. Every irrigation system needs the water pump to work efficiently based on the availability of the water source and the distribution of water, and the irrigation system in use. These pumps are powered by an electric motor. The maintenance of the pump will indicate how much electric power is used. Traditional electricity-driven pumps are generally fossil-fueled as they need to receive sufficient power to draw up the water.

The drawback of using fossil-fueled water pumps is that they get their electricity from fossil fuels thereby increasing the threat to the environment. Fossil fuels include coal, oil, and natural gas. Eighty-one percent of the energy in the United States is from these three resources. They are used for heating, transport, manufacturing, and electricity. However, these are not renewable resources and the impact on our environment continues to be critical to some people. The frozen wind farm in Texas in 2021 showed many people that relying on just one source of energy is unwise.

Drawbacks of fossil-fueled water pumps

  • Greenhouse gas emissions: Fossil fuels are known to cause high levels of greenhouse gas emissions and therefore, a threat to human life. Studies show that oil, natural gas, and coal cause higher death rates and greater levels of greenhouse gas emissions.
  • Impact on the economy: Fossil fuels increase air pollution. The direct and indirect air pollution costs have risen up to 3.3% of the global GDP. The cost to the individual consumer is also high. While fossil fuel prices may seem to be low, the hidden costs in environmental destruction are high.

Solar water pumps, on the other hand, relying on solar power for energy may be an effective solution for the future. Thus far, solar water pumps have been useful in remote areas that are off the grid, and where the cost of running the traditional AC power is too high. In these areas, solar water pumps have been useful in pumping water for irrigation needs.

What is a solar water pump system?

Affordable and easy access to water sources is constrained in many regions where agriculture plays a dominant role. People living in these areas have either the option to use a distant power grid or use fuel-powered pumps and draw the water from a nearby water source. Using a distant power grid can prove expensive because of the need for electrical power lines and utility bills. The same is true of gas and diesel-powered water pumps with their need for regular refueling and maintenance.

The solar water pump kit can be an ideal alternative in this situation because solar power is a renewable source of energy and is completely eco-friendly. A solar water pump also needs electricity, but it is provided by photovoltaic (PV) panels. This means that the pumping system has a solar panel array and it provides power to the electric motor enabling it to power up the water pump.

Solar-powered water pumps for irrigation can supply water to remote areas that are off the power grid. A solar water pump can be a stand-alone system depending on the PV panels that get their power supply during daylight hours.

What are the components of a solar water pump system?

The main components of a solar-powered submersible water pump system are the solar PV array, the pump controller, and the pump.

Components of a Solar-Powered Water Pump

Solar PV Array

The photovoltaic panels form the power source. The solar panel is measured in watts of power it produces. Therefore, installing a solar panel will depend on the amount of power you need to pump water. Solar panels are better off with 20% more wattage than necessary as they can remove the need for any additional current boosters. The solar array consists of solar cells and the amount of power they can produce depends on the size of the panels, the number of the panels, and the materials of solar cells.

Water Pump

A water pump is a device that uses the power from the solar panel to move the water. It draws the water from the source and distributes it where necessary. Some pumps work better when using solar power. Pumps that draw less power are usually preferred. Positive-displacement pumps are chosen if the water source is a deep well. In such cases, the pump moves a fixed amount of water and in proportion to the amount of power they receive.

Water pumps work best when they produce a combination of pressure and flow of water for certain power input. Solar water pumps are rated on the voltage of electricity that they need from the power source. For instance, a large pump of 48 volts would need more power and can pump more water.  A few water pumps would also need float valves, switches, and filters.

Pump Controller

A pump controller is a device that gets installed between the water pump and the solar panel. It allows the water pump to switch on normally when there is less light. There are two functions for the controller. One is that it matches the input power available in the PV panels with the output power that is received by the pump. The second function is that it provides protection against a fluctuating voltage. The controller ensures that the system gets switched off when the voltage is either too low or too high ensuring that the water pump remains in good condition.

Other components

  • Tank storage: The tank’s storage capacity should ideally be enough to supply water for five to ten days if the water consumption is average. The storage, as well as the consumption, usually depends on the climate and the usage. But, having a little extra water stored in the tank allows for an unexpected increase in usage. The tank’s storage plumbing should work in such a way as to hold a reserve; therefore, the point of discharge must be a little higher than the bottom.
  • Battery storage: The batteries store the power provided by the solar panels during the day and ensure that the water pump can function even when there is little or no sunlight. The battery also keeps the power stable during the fluctuating power supply.
  • Charge controller: The solar charge controller is used to charge the battery or to run a DC supply.
  • Wiring: Wiring is essential for a solar water pump system, and connects the solar panels to the water pump. A combiner box may be used to make the wiring safe.
  • Circuit breakers: Circuit breakers may be installed to manually switch the water pump on or off if the water pump needs repairs or maintenance.
  • Pipes: Solar water pump systems will need appropriately sized pipes based on the output pressure that is required. Pipes can be of plastic, steel, or copper.

The classification of solar-powered water pumps

The different types of water pumps are solar submersible water pumps and solar surface water pumps.

Solar-Powered Submersible Water Pumps

Typically, a submersible water pump is of a cylindrical shape and is fit inside the well casing. A submersible solar water pump is ideal if the water source is deep as in the case of a well. They operate directly off the solar panel and the battery. The pump operates during the day and the water gets stored in the storage tank to be used when necessary. Submersible pumps will depend on the depth of the water source and the quantity of water you need.

In most cases, the wells need not be drilled beyond the edge of the water table. For agricultural needs, the wells can be shallower as against a deeper well if the need is for domestic water use. The submersible solar water pump will also need to be measured against the amount of power it can supply to push the water vertically.

Solar Surface Water Pumps

Solar surface water pumps are preferred when the water source is shallow such as a pond, lake, or wells that have water within twenty feet of the surface. The advantage of a surface water pump is that it can push water to a greater distance. The disadvantage being that may not be able to push water vertically as is the case of the submersible water pump. Solar surface pumps are less expensive than submersible ones.

Understand the pros and cons of solar-powered water pumps

Solar water pumps versus fossil-fueled water pumps

Fossil fuels as an energy source for water pump systems have been the traditional approach that involves the use of non-renewable resources such as oil, gas, and coal. These pollution-generating sources have increasingly become a threat to the well-being of society as well as the environment. They are more expensive in terms of the utility bills on electricity consumption.

The cost of fossil-fueled water pumps also varies depending on the distance from the power grid and the components needed to connect the water pump system to the power grid. Fossil-fueled water pumps produce more noise as well as air pollution and are likely to need high maintenance. They do not last long and would need the replacement of parts or the whole water pump system.

Solar-powered water pumps, on the other hand, are eco-friendly because they use solar power which is a renewable energy source. They are stand-alone systems and require lower maintenance. They have a long lifespan and the average costs of usage are low. The table below shows the basic advantages and disadvantages of solar-powered pumps and fossil-fuelled water pumps.

Using Solar Pump for Irrigation

Factors to consider when choosing a solar water pump

A pump helps in increasing the energy of the water vertically or horizontally to regions in need of water. Solar water pumps are inexpensive in the long term and they are eco-friendly. There are many factors to consider when choosing a solar-powered water pump for irrigation.

Desired Flow Rate

Flow rate is the time a water pump takes to pump the required quantity of water, which is measured in gallons per minute. Depending on where you need the solar pump to be installed and the distance from the water source, you may choose one that is able to pump more than 650 gallons of water per minute. For domestic use, a solar pump that can pump around 55 gallons of water per minute should suffice.

Size of the Inlet

Generally, pumps have an inlet size between one and six inches. The bigger the size of the inlet valve, the greater will be the volume of water that can be pumped out.

Head and Pressure

Head, in this case, means the amount of water that can be pumped to the longest distance vertically. This affects the flow rate because if you need the pump to suction water from a deep well where the water source is below 60 meters, and your pump has a maximum head of 60 meters, the flow rate will be slow or even zero. Therefore, the solar pump you choose will need to have a maximum head that is higher than the distance in height you need the water to flow.

Total Dynamic Head (TDH)

Given a particular size of the solar array and the total dynamic head (TDH), water pumps can be measured on the number of gallons per minute they can supply. The number of gallons required per day will be a deciding factor on the size of the solar water pump.

Before designing a water pumping system, it is essential to determine the TDH. TDH has three components: pressure head, elevation head, and friction head loss.

  • Pressure Head: It refers to the amount of water pressure available at the pipe’s outlet. It can either be an open pipe or hose reaching into the water storage tank. In some cases, there may not be an indication of the pressure head, and it can be set to zero. In others, indicating a specific pressure head, it can be multiplied at the outlet in PSI by the pressure of one column of water that is 2.31 ft/psi. For example, if the outlet PSI is 20, it would be multiplied by 2.31 resulting in 46.2 ft of TDH.
  • Elevation Head: It is the distance between the water source and the height of the water being pumped to reach the water storage tank. It is the vertical distance when it defies gravity to reach the tank.
  • Friction Loss: In order to calculate the TDH, it is important to calculate friction losses. Once the length of the pipe through which the water has to flow is determined, and including the pipe sections at different angles, size of the pipe, material of the pipe, flow rate, and the number of valves, it becomes easy to calculate the amount of friction head loss in ft of the given head.

The total TDH is calculated by adding the numbers derived in calculations of the pressure head, elevation head, and the friction loss, i.e.,

Pressure Head (ft) + Elevation Head (ft) + Friction Loss (ft)

Other factors to consider include your water needs. If you need water supply during the nights or during cloudy or rainy days, you may need a booster to create the required water pressure. In such circumstances, you may also need a battery to store the solar power so that water can still be available.

How much does a solar water pump cost? Is it worth the investment?

The cost of a solar-powered water pump system depends on the parameters (flow rate, TDH, etc.) of the pump, then the size of the solar PV array required, and other components we want to integrate into the system.

The price range of solar water pumps can be anywhere between $2,000 and $5,000 for the solar panel array and the solar water pump kit. It includes a pump. It will help to understand the way in which the water output is related to the cost. There are also different models that vary in the amount of output and based on the number of solar panels.

The above costs are an approximation only and there are more expensive options also available in the market. The cost of a solar-powered water pump will also depend on the source of the water. Surface water pumps will be cheaper as they need less energy to draw water from the source, as in the case of drawing water from a pond or lake. Solar-powered water pump for irrigation is one such example. Solar-powered submersible water pumps will be more expensive as the water has to be drawn out from a greater depth, as in the case of deep wells.

Solar water pumps serve several purposes

Solar water pumps are competitive since they do not involve extensions of power lines to reach the power grid. With a lifespan of over twenty years, solar water pump systems have an advantage over fossil-fueled water pumps. Solar-powered water pumps are also energy efficient and suitable for regions that are either too far from the power grids or too expensive to connect with.

Some of the best applications of solar water pump systems include irrigation and drinking water for livestock. They are most effective in supplying water from surface water or groundwater and distributing the water stored in their storage tanks. The advantages of a longer lifespan and cost savings cannot be overstated, which makes the investment justifiable for home use as well as agricultural irrigation.

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