Conception for a large scale irrigation project
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Based on the potential green projects in Saudi Arabia, under extreme conditions in the desert, constitutes the use of the LIUJIA Solar pump as a core component for a micro-drip irrigation system.
This system can be used to distribute water up to 240 young trees, for three years of growth. It can be easily relocated to a new area with the same processes taking effect. A large-scale program for up to one million young trees can be watered with multiple micro systems. Using identical components will allow feasibility, reliability, easy installation and maintenance in a dry, water shortage area for green landscaping.
The article also describes the conditions under high-temperature, sand and water in the desert that could create problems; the field test phase will provide solutions for any problems to be resolved for the system or components.
A. Project Description
The green project in Saudi Arabia is based on planting about 1 million trees in the desert. A large water storage area with a capacity of 3000m3 will supply a number of small mobile water tanks with one or more solar pumps, which further distribute water to the trees. The vertical height difference between water level in the mobile tanks and the water pipe will be up to 2 meters.
It is estimated that a plant requires 2 liters / day. The water supply should not be interrupted in any case as tree roots would only grow at the surface rather downwards, thus 1-3 hours per day is required for each tree.
After 3 years it is possible for the tree to survive without artificial irrigation, thus relocation of the solar irrigation system or an alternative usage is possible.
The ambient temperature can reach up to +70 - +80 ° C in the desert. Therefore all components need to be of highest quality to work consistently under these conditions and with minimal effort.
Exhibit 1: Canal of solar irrgation unit
Exhibit 2: One unit with eight canals
B. Usagee of the the LIUJIA Solar pump in the project
Under the above assumptions, the LIUJIA Solar pump type LJ1012-S with a 13W solar module or the LJ2012-D with 26W solar module is very suitable for this application. The expenditure for planning, installation and maintenance is comparably low.
1a. Since solar modules are influenced by technical factors, the standard test measurement for all solar conditions is at +25°C. However, if the ambient temperature increases by +10°C it will reduce the output voltage of the solar module by 1.0 volt. In this project we are assuming an extreme temperature e.g. +75°C, which means that the output voltage of the solar module is reduced by 5.0V. If output voltage of the 13W solar module at +25°C is 17.5V, then at +75°C it would only be 12.5V, which is too low to start the pump. A solar module of 22V output at +25°C would be required to operate the pump normally.
1b. An investigation needs to be conducted to analyze if the current cable insulation from solar module is of high heat resistance. Otherwise a cable with better insulation must be used.
1c.The solar module is made of aluminum and toughened glass and needs to be secured carefully to prevent movement and sand storm damage during severe weather conditions.
1d. Sand in water is a great threat to seamless functionality of the pump. If sand gets into the pump, it will clog the piston, which reduces or stops the movement of the pump. In this case the pump must be cleaned on site (approx. 20 minutes required for instructions see this link)
This can be easily avoided if a synthetic filter material is used, as it will stop sand from entering the pump. Also reduced water output can be often corrected by the instructions above. If the maximum output of 100 liters per hour is required, a large filter such as a filter bag should be used, which also can be utilized for a much longer time span than a very small filter.
2. 100 meters of horizontally laid water pipes, with 10mm internal diameters, will increase friction pressure by 0.1 bar (equal to 1 meter pumping height). For smaller water pipes, with internal diameters of 4mm, the friction will be even higher. Therefore each channel should have the same length in order to have a balanced pressure in each drip head.
2a. Conventional water supply pipes for irrigation are mostly made of PVC-based plastic that has only a temperature resistance of +60 ° C - +80 ° C. For this project it is recommended to use silicone tubes with a temperature resistance up to 180 ° C.
3. It is assumed that Saudi Arabia has 8 peak sun hours per day, which results in a daily output of 480 liters of water. Under the estimation that 0.5 bar are required for the distribution system to compensate any height differences and friction losses in the pipes, one pump could supply 240 plants daily with 2 liters water per plant.
4. It is proposed that water is diverted by a solar-powered water switch, which has one input and 8 outputs. The switch would turn on or off at different time intervals for each output. The switch would be computer controlled so the length of time and sequence of each channel can be selected randomly to get an average supply for each channel.
5. For example: Water is channeled regularly or randomly by the solar switch every hour from A1 to A8. In Fig.1 is connected to approximately 30 plants in a star shape by fine water pipes with drip heads A1-01 to A1-30. These drip heads provide 2 liters of water for each plant. This process would be the same for every section of the irrigation system.
6. The drip heads of A1 channel, which are connected to the fine water pipes, must be enhanced by a reflux valve. Without this reflux valve, air will flow into the channels at night when outside temperature is lower than in the channels, which causes blockage of some of the channels.
7. Thousands of units with identical components can be assembled together to form a large solar irrigation system. The total system is easy to develop, install and maintain, saving huge investment costs and men power.
There are details about the concept, which need to be explored further. For example the extreme temperatures in the desert might lead to evaporation and condensation. How does this influence the drip system?
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