SD500SP and SD700SP - Pumping Using Energy from the Sun

It is a natural fit – with expertise in both AC motor control and utility scale solar inverters it seems the perfect solution to tie both technologies together – enter the SD500SP and SD700SP solar pumping systems.

Everyday the sun beams down huge amounts of energy just waiting for us to capture. For many pumping applications this energy can be collected and put to use – either as “standalone” or “island” application where the only energy used is solar, or alternatively, the solar can be the primary energy source and topped up by the mains or generator connection, or vice versa. This is referred to as a “hybrid” system.

The SD500SP is great for low power “standalone” systems where there is no connection to the grid. A suitably sized PV array is connected to the VSD. An onboard Solar Pumping MPPT PLC manages the operation of the control system and ensures that the system is pumping at optimum for the given solar conditions. The PLC will turn the pump on and off automatically. Perfect for those little stock water pumps in the middle of nowhere with no electrical supply close by. It can also be used as a “hybrid” system by connecting both PV panels and connection to the mains.

The SD700SP can be operated in both a “standalone” mode or in “hybrid” mode. The SD700SP uses a modified version of the standard SD700 hardware which has expanded to accommodate higher voltages and currents in the DC bus. The solar management software is written into the SD700SP firmware and is accessible thru the SD700SP display. “Standalone” operation is as per the SD500. “Hybrid” allows parallel energy sources to the VSD – one from the PV field, the second from the mains or a generator. This makes it ideal for systems where continuous controlled pumping is required but the expense of kWh purchased from the grid or diesel generator can be reduced by the addition of the solar energy. If using a generator, the generating equipment can be started and stopped via the SD700SP controls.

Don’t be fooled into thinking that designing a solar pump system is just banging a couple of solar panels directly into the DC bus connection of your VSD. Solar pumping in its simplest configuration is far more complex than that. Provision must be given to sizing of the PV solar array, the appropriate string voltage, the appropriate power rating, and operating conditions in all thermal environments. It is very easy to inadvertently end up with a system that has insufficient voltage to run reliably – remembering peak generation is only for a very short period each day – or to provision for the fact that the PV panels will generate high voltage in cold sunny conditions which can lead to a voltage high enough to damage the VSD DC bus capacitors. This can be a very common occurrence in places with cold, sunny winters, like Central Otago. A good system design will take all these factors into consideration.

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