Technical note

Power use of electrochemical descaling

Electrolyser, side-stream pump and auxiliaries. An estimation structure and the five site inputs needed for a real figure.

First, which power?

Before asking "how many kWh", ask "which part of the plant". A side-stream electrochemical system draws power in at least three places: the electrolytic power supply, the side-stream pump, and controls and cooling. Quoting only the electrolyser looks flattering; adding the pump gives the number that actually shows up on the customer's meter. There is no single kWh figure per unit — only a figure for this system, this side-stream ratio and this duty cycle.

1. What the consumption is made of

First, the power supply: DC voltage times current, times operating hours. Voltage and current vary with water quality and deposit condition; they are not constants. Second, the side-stream pump: flow times head converted to shaft power, divided by pump and motor efficiency, times running hours. Third, controls, cooling and trace heating — usually the smallest share, but not zero.

2. You can estimate it yourself with this structure

Annual kWh = (electrolyser power × electrolyser hours) + (pump shaft power ÷ efficiency × pump hours) + (auxiliary load × hours). The two site-specific inputs are the side-stream ratio and the operating strategy: what percentage of main circulating flow is treated, and whether the unit runs continuously or only when water quality demands it — those two decide the order of magnitude.

3. Three common mistakes

One: quoting the electrolyser and ignoring the pump — the number looks good, and the meter disagrees on day one. Two: calculating a full year at rated load, when the unit actually spends most of its time at part load, so annual consumption is overstated. Three: ignoring the tariff structure. Where peak and off-peak prices differ sharply, shifting run hours to off-peak cuts the bill, provided the site allows intermittent operation.

4. Three ways to reduce it

Modulate current density to water quality instead of running flat out; optimise the side-stream ratio — more treated flow is not automatically better, enough to hold the scale-forming ions in check is what matters; and optimise the operating strategy together with blowdown and cycles of concentration. Often "treat a little less, blow down a little more" beats "treat at full load" on total cost. All three depend on the site water balance; none of them should be guessed.

5. Four inputs for a calculation sheet

Total circulating flow, planned side-stream ratio, target cycles of concentration, make-up water analysis (calcium hardness, alkalinity, chloride, TDS) — plus your electricity price. With those five we calculate annual kWh and annual cost, with assumptions, boundaries and uncertainty stated. If data is missing, we say which item is missing and how much it moves the answer; we do not pass estimates off as measurements.