Free Online Tool

Desalination Energy Requirement Calculator

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<div class="derc82m5-header">
    <h2>Desalination Energy Requirement Calculator</h2>
    <p>Estimate the energy required to desalinate seawater using a reverse osmosis system.</p>
  </div>

<div class="derc82m5-grid">
    <div class="derc82m5-card">
      <h3>Input Values</h3>

<div class="derc82m5-field">
        <label for="derc82m5_pressure">Pressure Required P</label>
        <div class="derc82m5-input-row">
          <input id="derc82m5_pressure" type="number" step="any" value="5.5" placeholder="Enter pressure">
          <select id="derc82m5_pressure_unit">
            <option value="mpa">MPa</option>
            <option value="pa">Pa</option>
            <option value="kpa">kPa</option>
            <option value="bar">bar</option>
            <option value="psi">psi</option>
          </select>
        </div>
      </div>

<div class="derc82m5-field">
        <label for="derc82m5_volume">Volume of Water V</label>
        <div class="derc82m5-input-row">
          <input id="derc82m5_volume" type="number" step="any" value="10" placeholder="Enter volume">
          <select id="derc82m5_volume_unit">
            <option value="m3">m³</option>
            <option value="l">L</option>
            <option value="ml">mL</option>
            <option value="gal">US gal</option>
            <option value="ft3">ft³</option>
          </select>
        </div>
      </div>

<div class="derc82m5-field">
        <label for="derc82m5_efficiency">System Efficiency η</label>
        <div class="derc82m5-input-row">
          <input id="derc82m5_efficiency" type="number" step="any" value="55" placeholder="Enter efficiency">
          <select id="derc82m5_efficiency_unit">
            <option value="percent">%</option>
            <option value="decimal">decimal</option>
          </select>
        </div>
      </div>

<button class="derc82m5-btn derc82m5-calc-btn" type="button" onclick="derc82m5Calculate()">
        Calculate Energy Requirement
      </button>

<div class="derc82m5-card" id="derc82m5_result_card">
      <h3>Result</h3>

<div class="derc82m5-result-box">
        <div class="derc82m5-result-label">Energy Requirement, E</div>
        <div class="derc82m5-result-value" id="derc82m5_main_result">27.7778</div>
        <div class="derc82m5-result-unit">kWh</div>
      </div>

<div class="derc82m5-result-row">
        <span>Specific Energy</span>
        <strong id="derc82m5_specific_energy">2.77778 kWh/m³</strong>
      </div>

<div class="derc82m5-result-row">
        <span>Energy in MJ</span>
        <strong id="derc82m5_mj">100 MJ</strong>
      </div>

<div class="derc82m5-result-row">
        <span>Energy in Wh</span>
        <strong id="derc82m5_wh">27777.8 Wh</strong>
      </div>

<div class="derc82m5-note" id="derc82m5_summary">
        Using RO energy formula: E = (P × V) / η, converted from Joules to kWh.
      </div>

<div class="derc82m5-actions">
        <button class="derc82m5-btn derc82m5-copy-btn" type="button" onclick="derc82m5CopyResult()">Copy Result</button>
        <button class="derc82m5-btn derc82m5-print-btn" type="button" onclick="derc82m5PrintResult()">Print</button>
      </div>
    </div>
  </div>

<div class="derc82m5-table-wrap">
    <h3>Unit Conversion & Result Breakdown</h3>
    <table>
      <thead>
        <tr>
          <th>Item</th>
          <th>Converted Value</th>
          <th>Used In Formula</th>
        </tr>
      </thead>
      <tbody id="derc82m5_breakdown">
        <tr>
          <td data-label="Item">Pressure P</td>
          <td data-label="Converted Value">5,500,000 Pa</td>
          <td data-label="Used In Formula">P</td>
        </tr>
        <tr>
          <td data-label="Item">Volume V</td>
          <td data-label="Converted Value">10 m³</td>
          <td data-label="Used In Formula">P × V</td>
        </tr>
        <tr>
          <td data-label="Item">Efficiency η</td>
          <td data-label="Converted Value">0.55</td>
          <td data-label="Used In Formula">Denominator</td>
        </tr>
        <tr>
          <td data-label="Item">Energy</td>
          <td data-label="Converted Value">27.7778 kWh</td>
          <td data-label="Used In Formula">(P × V) / η / 3,600,000</td>
        </tr>
      </tbody>
    </table>
  </div>

<div class="derc82m5-info-grid">
    <div class="derc82m5-info-card">
      <h3>Formula Used</h3>
      <p>This calculator estimates reverse osmosis desalination energy using:</p>
      <div class="derc82m5-formula">E = (P × V) / η</div>
      <p>
        Since P × V gives energy in Joules when pressure is in Pa and volume is in m³,
        the calculator converts Joules to kWh using:
      </p>
      <div class="derc82m5-formula">E(kWh) = (P × V) / (η × 3,600,000)</div>
    </div>

<div class="derc82m5-info-card">
      <h3>How to Use</h3>
      <ul>
        <li>Enter the pressure required for the reverse osmosis process.</li>
        <li>Enter the volume of seawater to be desalinated.</li>
        <li>Enter system efficiency as percent or decimal.</li>
        <li>Click “Calculate Energy Requirement” to get energy in kWh.</li>
      </ul>
    </div>
  </div>

function derc82m5GetNumber(id) {
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function derc82m5GetValue(id) {
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function derc82m5Format(num) {
        if (!isFinite(num)) return "—";
        var abs = Math.abs(num);
        if ((abs > 0 && abs < 0.0001) || abs >= 1000000) {
          return num.toExponential(6).replace(/.?0+e/, "e");
        }
        return Number(num.toFixed(6)).toString();
      }

function derc82m5PressureToPa(value, unit) {
        var factors = {
          pa: 1,
          kpa: 1000,
          mpa: 1000000,
          bar: 100000,
          psi: 6894.757293
        };
        return value * (factors[unit] || 1);
      }

function derc82m5VolumeToM3(value, unit) {
        var factors = {
          m3: 1,
          l: 0.001,
          ml: 0.000001,
          gal: 0.003785411784,
          ft3: 0.028316846592
        };
        return value * (factors[unit] || 1);
      }

function derc82m5EfficiencyToDecimal(value, unit) {
        if (unit === "percent") return value / 100;
        return value;
      }

function derc82m5ShowError(message) {
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function derc82m5ClearError() {
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window.derc82m5Calculate = function () {
        var pressureInput = derc82m5GetNumber("derc82m5_pressure");
        var volumeInput = derc82m5GetNumber("derc82m5_volume");
        var efficiencyInput = derc82m5GetNumber("derc82m5_efficiency");

if (!isFinite(pressureInput) || !isFinite(volumeInput) || !isFinite(efficiencyInput)) {
          derc82m5ShowError("Please enter valid numeric values in all fields.");
          return;
        }

if (pressureInput <= 0 || volumeInput <= 0 || efficiencyInput <= 0) {
          derc82m5ShowError("Pressure, volume, and efficiency must be greater than zero.");
          return;
        }

derc82m5ClearError();

var pressurePa = derc82m5PressureToPa(
          pressureInput,
          derc82m5GetValue("derc82m5_pressure_unit")
        );

var volumeM3 = derc82m5VolumeToM3(
          volumeInput,
          derc82m5GetValue("derc82m5_volume_unit")
        );

var efficiency = derc82m5EfficiencyToDecimal(
          efficiencyInput,
          derc82m5GetValue("derc82m5_efficiency_unit")
        );

if (efficiency <= 0 || efficiency > 1) {
          derc82m5ShowError("Efficiency must be between 0 and 1, or between 0% and 100%.");
          return;
        }

var rawEnergyJ = pressurePa * volumeM3;
        var adjustedEnergyJ = rawEnergyJ / efficiency;
        var energyKWh = adjustedEnergyJ / 3600000;
        var energyWh = energyKWh * 1000;
        var energyMJ = adjustedEnergyJ / 1000000;
        var specificEnergy = energyKWh / volumeM3;

document.getElementById("derc82m5_main_result").textContent = derc82m5Format(energyKWh);
        document.getElementById("derc82m5_specific_energy").textContent = derc82m5Format(specificEnergy) + " kWh/m³";
        document.getElementById("derc82m5_mj").textContent = derc82m5Format(energyMJ) + " MJ";
        document.getElementById("derc82m5_wh").textContent = derc82m5Format(energyWh) + " Wh";

document.getElementById("derc82m5_summary").textContent =
          "E = (" + derc82m5Format(pressurePa) + " × " + derc82m5Format(volumeM3) +
          ") / (" + derc82m5Format(efficiency) + " × 3,600,000) = " +
          derc82m5Format(energyKWh) + " kWh";

document.getElementById("derc82m5_breakdown").innerHTML =
          '<tr>' +
            '<td data-label="Item">Pressure P</td>' +
            '<td data-label="Converted Value">' + derc82m5Format(pressurePa) + ' Pa</td>' +
            '<td data-label="Used In Formula">Required RO process pressure</td>' +
          '</tr>' +
          '<tr>' +
            '<td data-label="Item">Volume V</td>' +
            '<td data-label="Converted Value">' + derc82m5Format(volumeM3) + ' m³</td>' +
            '<td data-label="Used In Formula">Water volume to be desalinated</td>' +
          '</tr>' +
          '<tr>' +
            '<td data-label="Item">Efficiency η</td>' +
            '<td data-label="Converted Value">' + derc82m5Format(efficiency) + '</td>' +
            '<td data-label="Used In Formula">System efficiency denominator</td>' +
          '</tr>' +
          '<tr>' +
            '<td data-label="Item">Raw Energy P × V</td>' +
            '<td data-label="Converted Value">' + derc82m5Format(rawEnergyJ) + ' J</td>' +
            '<td data-label="Used In Formula">Energy before efficiency adjustment</td>' +
          '</tr>' +
          '<tr>' +
            '<td data-label="Item">Adjusted Energy</td>' +
            '<td data-label="Converted Value">' + derc82m5Format(adjustedEnergyJ) + ' J</td>' +
            '<td data-label="Used In Formula">(P × V) / η</td>' +
          '</tr>' +
          '<tr>' +
            '<td data-label="Item">Energy Requirement E</td>' +
            '<td data-label="Converted Value">' + derc82m5Format(energyKWh) + ' kWh</td>' +
            '<td data-label="Used In Formula">(P × V) / (η × 3,600,000)</td>' +
          '</tr>' +
          '<tr>' +
            '<td data-label="Item">Specific Energy</td>' +
            '<td data-label="Converted Value">' + derc82m5Format(specificEnergy) + ' kWh/m³</td>' +
            '<td data-label="Used In Formula">Energy per cubic meter</td>' +
          '</tr>';

derc82m5LastResultText =
          "Desalination Energy Requirement Calculator Resultn" +
          "Formula: E(kWh) = (P × V) / (η × 3,600,000)nn" +
          "Pressure P = " + derc82m5Format(pressurePa) + " Pan" +
          "Volume V = " + derc82m5Format(volumeM3) + " m³n" +
          "Efficiency η = " + derc82m5Format(efficiency) + "nn" +
          "Energy = " + derc82m5Format(energyKWh) + " kWhn" +
          "Specific Energy = " + derc82m5Format(specificEnergy) + " kWh/m³n" +
          "Energy = " + derc82m5Format(energyMJ) + " MJn" +
          "Energy = " + derc82m5Format(energyWh) + " Wh";
      };

window.derc82m5CopyResult = function () {
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var textToCopy = derc82m5LastResultText || document.getElementById("derc82m5_summary").textContent;

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window.derc82m5PrintResult = function () {
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var resultCard = document.getElementById("derc82m5_result_card").innerHTML;
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var printWindow = window.open("", "_blank");
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          'button{display:none;}' +
          'table{width:100%;border-collapse:collapse;margin-top:14px;}' +
          'th,td{border:1px solid #c8f4f7;padding:10px;text-align:left;}' +
          'th{background:#dffafd;color:#075c68;}' +
          '</style></head><body>' +
          '<h2>Desalination Energy Requirement Calculator Result</h2>' +
          resultCard +
          breakdown +
          '</body></html>'
        );

printWindow.document.close();
        printWindow.focus();
        printWindow.print();
      };