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Isolated pumping systems

The "Pumping Systems" in PVsyst only concern "isolated" pumping systems, which work according to the sun's availability, without electrical storage. Such a system consists of one (or several) pump, a PV array and a controller/power conditioning unit  (very exceptionally a booster battery).

The implementation of such systems involves a detailed definition of the hydraulic circuit  (kind of system like deep well, pumping from a lake or equivalent, or pressurization system) and user's needs, the Head (as function of the flowrate and possible other parameters), the water needs, and a tank storage. Some other constraints may be taken into account (maximum drawdown in a deep well, tank full, etc).

The running mode according to the sun's availability implies that the pump will operate at a power imposed by the maximum power of the PV array at a given time. As the head is imposed by external conditions (level difference, head loss in the pipes, drawdown in a deep well, etc.), the resulting flow rate will be directly related to the instantaneous power availability.

Therefore the simulation needs a complete model of the pump behavior, giving the resulting flowrate in any conditions of power and head. The Operating point, depending on the Total Head variations according to the flowrate (pipes head losses, drawdown level) will be evaluated by successive approximations.

The main advantage of isolated Pumping systems is the absence of a battery, and the associated maintenance costs (replacement, etc). The storage is indeed performed by the accumulation of water in the tank. However this requires a pump able to operate in a wide range of powers.

Conventional pumping systems

The conventional pumping systems, fed by a grid electrical system (or eventually a big stand-alone system like a village mini-grid) will  operate at the specified voltage of the grid. The operating power will be fixed, it is supposed to be available at any time. The system will operate in "ON/OFF" mode, according to the user's needs and control system. An intelligent strategy of energy management may favor the pumping  during the daylight hours, when the sun is available.  

Such systems are not implemented explicitly in PVsyst. The pumping system should be considered as a load in the same way as any other load. PVsyst doesn't propose an evaluation of the pumped water, nor any other parameter / result concerning the hydraulic part.

Therefore a pumping system as defined in PVsyst cannot be associated to any other PV system, even a stand-alone system. It should really stay independent of any other power system.