WattElse has been invited by the Nature and Forest Department of Nivelles and the non-profit organisation Dyle Environnement to study the technical and economic feasibility of installing renewable energy production units to supply a water pumping system for water basins of the former sugar factory of Genappe.

A remarkable biodiversity

Since the closure of the sugar refinery, the site has been reassigned to a nature reserve. Indeed, it counts the presence of many old settling ponds which were used by the old sugar factory to treat the residues of the production of sugar. The presence of these basins and wetlands has contributed to the development of a remarkable biodiversity in this area. However, the relief of the site and the dry climatic conditions result in the drying of most basins during all or part of the year. Therefore, the site managers would like to set up a pumping system to supply water to the upper basins of the site from the downstream basin in order to develop mudflats, rich in biodiversity.

The design of the pumping system

The first part of the mission consisted of sizing of the pumping system. To do this, we determined the route of the pipes to connect the lower basin to the two upper basins. In total, 755 m of pipeline will have to be installed of which 150 m buried. After determining the route, we evaluated the head losses to overcome the difference in height between the lower basin and the upper basins and calculate the optimal diameter of the piping to be installed. Third, we analysed existing pumping systems capable of pumping between 50 m³ per our and 100,000 m³ per year. For this type of application, 2 solutions are available on the market: submerged and surface pumps. Following our analysis, the installation of two submerged pumps of 8 kW was favored for their lower cost, their good frost resistance and the fact that it is not necessary to install a pipeline between the source and pump.

Toward energy autonomy

The second part of the mission aimed to study the possibility of ensuring the operation of pumps by renewable energies. Three options were modelled: solar panels, small wind and the installation of a hydroelectric turbine. These different options have been compared to the conventional connection solution to the power grid.

In terms of solar potential, an optimum of 24 kWp of photovoltaic installation was determined. The energy produced by the installation would be self-consumed at the site by at least 96%, the balance not being valued. The installation, placed on the ground, would be equipped with a system of anti-vandalism.

At the level of the small wind turbine, a vertical axis wind turbine could also provide the electricity needed to operate the system. An optimal power of 22 kW was determined and the height of the mast would culminate at 24m. The energy produced by this wind turbine would cover the energy needs of the pumps mainly during the winter. This solution also involves the installation of an electrical cable between the highest point of the site (location of the wind turbine) and the lower basin.

The hydroelectric option was quickly discarded because the vertical drop and the flow observed on the rivers near the site are not enough to operate a hydroelectric turbine.

What next ?

The realisation of this study has allowed the Department of Nature and Forestry (DNF) to obtain a comparative analysis of different renewable technologies with their advantages and disadvantages.

The solar system is advantageous in most criteria. Indeed, it has a life of 25 years which is enough for this project. In addition, it stands out from other renewable solutions by its cost (26% of the investment profitable in 6 years), low maintenance costs given the absence of wear parts and its limited environmental impact since its installation does not require the use of concrete or the artificialisation of the soil.

At present, the DNF will take steps to find financing to cover the costs associated with the pumping and photovoltaic power generation system estimated at € 157,000.

We wish them much success in carrying out their project.