RO Plant Energy Consumption

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How can I calculate the specific energy consumption of my small scale RO system for brackish water desalination? 

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8 Answers

  1. Hi There

    This method is being used by most SWRO Plant Operator

    Specific Energy Consumption (S.P.C) = Energy Consumed (KwH) / Product Water Produced (m3/Day)

    Let Say you plant is producing 136MLD and the Total Energy consumed per Day for the Plant is 459 MWH

    So your Plant SPC should be - (459 x 1000) / (136 x 1000) = 3.375 kwh/m3

  2. Simple method

    Units requiring the power/energy are as below

    1. Feed water Pump
    2. High pressure Pump
    3. Disinfection unit (UV plant)
    4. Backwash /Chemical cleaning Pump

    Find out run hours of each unit in one day operation.

    Power can be calculated as below

    1. Pump power HP  
    2. Time run hour

    Power in KWH consumed HP of Pump*0.75*run hour

    This way one can calculate energy required for each unit. Summation of will give total energy requirement.

     

  3. Hi Reuben,
    In addition to calculating the specific energy consumption, one could measure the specific energy consumption from energy input and water output data. To do this you would need to install an energy meter at the mains electricity incomer to the RO plant - ideally to record actual energy input over a day or two. Alternately you could measure the power drawn using a clamp on power meter over a few minutes of normal plant operations. Use this power value to multiply with time over which the water output has been measured.

    Specific energy consumption would be in terms of kWh of energy input per litre of treated water output. 

  4. Your leading RO vendors such as Desalitech use sophisticated software to model and identify the optimum membrane to use for your specific brackish water. The software then predicts what chemicals and the amounts you will need to use for ph adjustment, antiscaling, etc, and then models the guaranteed water recovery and the energy use per Kgals. Leading RO vendors will then stand behind those numbers. 

    1 Comment

    1. @ALL Thanks for the answers . I really appreciate your efforts

  6. There are quite some papers that talk about energy consumption per cubic meter of water desalinated by RO membranes, for fresh water, brackish and sea water. Try the paper "State-of-the-art of reverse osmosis desalination", from that one you can follow the references and eventually find papers with formulas for calculating your energy consumption according to your operational flows and pressures. Success

  7. Hello Rueben

    According to the whole design, specifications of all electrical consumers, which are mostly feed, high pressure and transfer pumps, will be defined baded of which yoy can inquire from manufacturers and the more acurate power will be defined. You can also estimate other consumers like air conditioning, lighting etc.

  8. Hi Reuben

    There are many tools in the internet to calculate the power consumption, another way to calculate the power consumption of a RO unit is also available in the commercially available software from membrane manufacturers, or there is always the option of making out your own excel table and input the values of the motors this later is my prefer method.

    I hope this helps.

    Luis Inarejo