Technical paper by Julia Kövi
In July/August 2019, clever off-grid photovoltaic pumping systems are emerging in Gambia, Africa through the collaboration of the GWE (German Water and Energy Group) with Fuji Electric Europe GmbH. The technical equipment is already on the way for the first 30 systems for clean drinking water. Among this: the frequency inverters especially designed for this application Frenic-Ace by Fuji Electric.
On the GWE premises there is a test system. Here, experts developed the solar panels with the correspondingly equipped inverters for the operation of a pumping system for series production, in order to go into operation soon on-site in Africa 1:1. The area of application in Gambia is challenging because once the rainy season is over, the dry seasons prevail in the tropical climate. The densely populated areas of western Gambia are entirely dependent on the groundwater for industrial and domestic use. It does not look great for nationwide energy supply. There is however one thing that there is an abundance of here: sun. The solution is therefore clear. Off-grid, solar-operated pumping systems, which ensure the clean and self-sufficient production of drinking water.
In 2018 GWE and Fuji Electric began collaborating. Fuji Electric is a manufacturer of sophisticated drive technology and high-performance inverters, with its European headquarters in Germany (Offenbach) and the parent company in Japan (Tokyo). Among the main areas of application for the inverter are pumps. With the Fuji Electric inverters, electrical drives (pumps included) can be operated with optimal speed so that energy consumption and operational costs are kept to a minimum. GWE is a developer of integrated applications for well construction and geothermal energy. As a company of Bauer Resources GmbH, it can rely on a worldwide network and over the last few years has already implemented a few thousand projects in this area. “In GWE we have a strong partner on our side; they are enabling the application of our inverters there where they are required most urgently”, said Heiko Loder, Graduate Engineer for Fuji Electric Europe GmbH. GWE provides a stable framework with their system solutions made up of solar modules, submersible pumps and water towers. The Frenic-Ace inverter by Fuji Electric is used here as the heart and interface of the connection. A special IP54 housing makes the Frenic-Ace resistant to external influences. The housing, like the inverter itself, originates from Fuji Electric, and was specially designed and assembled for GWE.
Independent of any power supply (off-grid), this system works entirely self-sufficiently and cleanly on renewable energy. No exhaust gases due to the combustion of diesel or other fossil fuels, subsequently no air pollution. Resources remain protected. Instead of this, due to self-supply, costs are significantly reduced and controlled. The system works quietly and automatically, reliably and with a long service life. The solar-pumping-fed production of water is therefore frequently also used for agricultural irrigation.
“The Frenic-Ace is particularly suitable for this application as it supplies the required specifications. Our standard software for inverters can be adapted if required. For GWE we coordinated them precisely to the project’s conditions”, explained Loder. Dry-run protection, energy-saving mode, optimised integrated MPPT controller (Maximum Power Point Tracking) and a precise water-tank fill level detection are among the totally relevant and important functions. Frenic-Ace recognises sudden system changes: e.g. if the intensity of the solar radiation is restricted by the clouds then the system immediately reacts. The start criteria are determined by the real-life system conditions on-site and the stop criteria are selectable dependent on the frequency or performance. Two PID controllers ensure a fast and smooth operation. You can select between grid and generator circuit for maintenance and back-up operation, this means that the system can be fed via a generator in an emergency alongside the off-grid operation (solar operation).
An advantage to the complete system is the IoT monitoring via smart system. Particularly important at locations where it is unlikely that an engineer would be available quickly. An ongoing inspection of the system can be ensured via remote maintenance. Through this the pump system’s data is transferred via the inverter directly to the mobile end user via laptop, smartphone or tablet, etc. Generally, Frenic-Ace is simple and low-maintenance to set up.
GWE and Fuji Electric will be using the Frenic-Ace with a performance class of 4 kW, 3-phase 400 V in this project for self-sufficient photovoltaic pumping irrigation. However, larger versions of up to 280 kW could be implemented. On the other hand, it is likewise possible to select a “smaller” inverter with a lower voltage, e.g. for less or smaller solar panels. Dependent on the pump selection, the Frenic-Ace version can also be selected in a 3-phase 200 V version and thereby be adapted economically to the framework conditions. And if it is not about the off-grid solution but about a grid-operated pump control, the Frenic-Ace-H, a Frenic-Ace variant can serve this purpose.
The current 30 systems in Gambia are only the start of the project. Other systems in countries such as the Ivory Coast, Burkina Faso, etc. are also in planning.