The energy consumption of a watermaker

This is almost entirely caused by the high pressure pump. The required power is closely related to the volume flow of seawater and the corresponding pressure. Here, systems without energy recovery can only differ in the design of the delivery rate in relation to the membrane surface and small differences in the efficiency of the motor and pump.

However, the relationship between the volume flow of seawater and the amount of fresh water produced is not linear. Pumping more seawater through the system increases the amount of fresh water, but to a lesser extent. Ergo, the energy efficiency related to the amount of fresh water produced decreases as the volume flow of seawater increases.

Why not simply reduce the amount of seawater to increase energy efficiency?

There are also negative effects if the volume flow is chosen too small. Along the membrane, in the direction of flow, the salinity of the seawater increases because water is removed from the solution. Due to the non-linear relationship between the volume flow of sea water and fresh water, this effect increases as the volume flow decreases.

This results in two adverse effects.

1. The quality of the product water in terms of salinity decreases slightly. No problem when new and in good conditions, but you have less buffer to maintain the quantity and quality of fresh water as the membrane gets older or other negative influencing factors (cold water).

2. The membrane requires a minimum volume flow to flush out the retained salt. This minimum depends on the operating conditions of the system. A system that is supposed to run around the clock for years, for example, requires a much higher volume flow of seawater than is the case with conventional systems for boats. The discontinuous operation allows a reduction to a certain extent. However, if the amount of seawater is too low, the lifespan of the membrane suffers.

Are there other ways to increase efficiency?

With the conventional watermaker, the operating pressure is set at a needle valve. The needle valve represents a flow resistance where a large part of the energy put into the water by the high-pressure pump is lost.

In order to reduce energy consumption further than is possible with conventional watermakers, some of this otherwise wasted wastewater energy must be recovered. The so-called energy transfer principle has become established among watermakers for yachts to achieve this. Here, energy from wastewater that is no longer needed is used to increase the pressure on the inlet side.

Clark Pump Watermaker

Instead of a conventional high-pressure pump, a so-called Clark pump is used here. With this previously patented pump design, the pressure on the wastewater side is used directly to increase the pressure on the inlet side. This requires a pump body that is specifically tailored to the respective product and contains various pistons and valves. This is the one disadvantage of the energy-saving systems with Clark pumps - in the event of a malfunction, troubleshooting is much more difficult for the layperson because it is not immediately obvious where there may be a defect.


If you compare different conventional systems in terms of the specified amount of fresh water and energy consumption, remember that magic cannot be achieved without energy recovery. Our systems are designed to ensure worry-free operation over a long period of time. In conventional systems, we give this a higher weight than to maximize the last bit of energy consumption without unnecessarily increasing it. Anyone who values ​​minimal energy consumption more highly is best advised to go with a system with energy recovery.