Commissioning of a hybrid solar power station to supply an irrigation system via SD700SP

Zamora 2 March, 2017

The unstoppable evolution of renewable energy, together with increases in fuel prices, is encouraging many users to obtain their energy supplies from alternative sources. Isolated pumping stations provide an ideal opportunity to convert to photovoltaic energy, as there is normally more than enough space to install the solar panels required.

The example that concerns us here is a station designed to irrigate several fields of crops via a 60 kW pump, powered exclusively by electricity from a diesel generator set. It consumes as much as 40,000 liters (over 10,500 US gallons) of fuel per growing season, which considerably affects agricultural production costs.

Given this situation, the customer decided to install an array of solar panels with a view to minimizing fuel consumption, but without reducing current performance.

The challenge faced by Power Electronics was to create a system capable of peak performance throughout the day, while minimizing diesel costs.

The problem lay in the type of installation which, as a hydraulic network, prioritizes constant pressure in the tubes over the quantity of water being pumped. This requirement for constant operation meant that a purely solar powered system would not be feasible, as changing amounts of sunlight prevent such continuity. We therefore had to consider a hybrid solution, in which the diesel generator kicks in to provide support whenever levels of solar radiation are low.

The corresponding hybrid solution developed by Power Electronics has two inputs: one AC and one DC. The design of this system prioritizes the supply of energy from the solar panels. Whenever the sunlight fades, the SD700SP unit starts up the diesel generator in order to keep system pressure within its pre-programmed parameters. The system returns to its default state as soon as the solar panels recover their power capacity.

All this is made possible by the versatility of the SD700SP and its exclusive Dynamic Maximum Power Point Tracker (or MPPt) algorithm, which allows the system to predict the performance of the solar panels and establish an optimum activation point based on the power available at any given moment. With this information at its disposal, the SD700SP can decide whether it is really necessary to start up the diesel generator or, on the contrary, if it just needs to regulate the system enough to deal with the drop in solar power without reducing pressure in the hydraulic network. The SD700SP also comes equipped with a wide range of pumping system features (startup of auxiliary pumps, hydraulic protection measures, smooth stop/start transition, etc.) inherited from the SD700, which has proved itself over many years as being able to adapt to any type of installation, while running under the most demanding of operating conditions.

After six months of operation, the customer expressed his maximum satisfaction, after having cut fuel consumption by around 90%, thereby reducing the investment payback period by more than had been expected. The project has also provided valuable experience for the installation of similar systems elsewhere.

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