RO Plant Energy Consumption

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How can I calculate the cost of the power for a reverse osmosis plant generated by a diesel generator? 

How can I best reduce the RO energy consumption and achieve the most economical energy efficiency?

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9 Answers

  1. I need the ​formula to ​calculate the ​cost of power (​Kilowatt hour) ​per thousand ​Imperial ​Gallons via a ​diesel ​generator. ​

    The generator ​is a 60KW which ​consumes 3.8 ​gallons/hour. ​ ​

    The facility ​power is 19.9 ​KWHr. ​

  2. If you want to reduce consumption and the plant production needed if higher than 1,800 m3 day we have a new technology Deep Desalination that only consume 1,8kwh/m3 http://www.ades.tv/en/products/low-energy-desalination/id/259

  3. Hi,

     The RO operational energy will depend on the incoming water salinity, RO recovery ratio etc. For example, the energy cost can be totally different if the feed water is a fresh water rather than a sea water. Even for a sea water RO, the recovery ratio will also control the energy consumption. 

  4. Typically in RO plants for desalination may b upto,10kWh of energy might b needed for every cu. M of freshwater.

    Submerged RO systems r proposed.

    If seawater depths off shore permit,hydrostatic pressure can b used,since a major fraction of RO plant energy used t pressurised feedwater.

    Integrated with wave energy devices,or other renewable energy sources r becoming popular.

    Egyptian solar,and Norwegian or Australian wind energy uses reported.

    Operating pressure depends on salinity.Could be up to 70 or more bars for seawater.As low as 20 forbrackish.

    Higher recovery ratios above 30 percent could foul up membranes faster and increase operational costs.

  5. Keep it simple. High Service diesel pumps with direct drive units are great. Membrane filter trains with one diesel for each filter train. Use Bahamas Power and Light Company for raw water. SWRO process is 32,000 mg/L TDS to less than 500 mg/L TDS. Stand-by generators should be two 500 KW or two 750 KW or two 1,000 KW. Ten day fuel supply of #2 diesel or more. Keep diesel clean. 100 hours between filter changes. Do not run out of fuel filters. Generators running at 1,800 RPM 24 hours per day do not do well on  dirty fuel. Always have # 30 Wt. oil for diesels or less. Based on air temp. Many times operators have said generators down 5 quarts and correct amount is five gallons. Always if you have funds and space a 20,000 US Gallon tank is great. Good luck.    

  7. Dear Antone,

    Good question,

    Electricity consumption depends on raw water quality (individual ions concentration) Reverse osmosis system design (system recovery rate, number of stages, type of membranes, etc.) and operating conditions (water temperature). 

    You can use Reverse osmosis design simulator to estimate electricity consumption. It is not an accurate result but will give you a very good idea, and making some tries in different conditions will precise the results. No electricity consumption result from another system will be exactly the same as yours. The reasons are that:  they don't have same water quality, same pumping equipment’s and same type of system (in term of design) as yours.

    Some roughly idea

    The theoretical absolute minimum amount of  energy  required by natural osmosis to desalinate average seawater is approximately 1 kilowatt-hour per cubic meter (kwh/m3) of water produced, or 3.8 kilowatt-hours per thousand gallons (kwh/kgal).

    1. The RO process consumes 2.9 kWh/m3 to 3.2 kWh/m3for normal water
    2. 2.2 kWh per cubic meter to 6.3 kWh per cubic meter in desalination,
    3. For large plant The total consumption is 3.6 kWh/m3,

    The power consumption also depends upon membrane condition

     

     

  8. Antone

    In short, it depends on the salinity of the raw water, the efficiency of the RO plant, cost of Diesel etc. You can probably work on 4 kWh/m3 desalinated water and R3/kWh. Thus, direct energy cost is about R12/m3. All other costs (antiscalant, chlorine, smbs, GAC, ex capital amortisation) can be R7/m3. All of this based on assumed raw water quality, very high level.

    We (www.alveo.co.za) build containerised RO systems with integrated Solar power supply for the African market. Maybe that is a better option than Diesel?

  9. Hello Antone, The diesel generator will be supplying other users but it should be able to take the measured power produced by this (and back up machines) and divide this by the cost of fuel, maintenance, depreciation and any other costs associated with the running of this machine. This will give you a cost / kWhr. By measuring the power consumed by the equipment in the RO plant over a measured production of final product water you can derive the kWhr/m3 and cost/m3