The Bethlehem Hydro Project was initiated to generate renewable electricity from the constant flow of water which runs into the Ash River as a result of the Lesotho Highlands Water Project.
After completing the feasibility study and assisting with environmental approvals, Aurecon was appointed to undertake the detailed design and project management duties for two mini hydro stations, one at Merino and the other at Sol Plaatje.
At the Marino site an eight metre high mass concrete weir diverts water to a canal. Overcoming hydraulic and geotechnical challenges, Aurecon designed the diversion structure to achieved the required spillway length.
The layout of the power station for the Sol Plaatje Dam differed significantly from that conceptualised at the feasibility study stage, achieving increased efficiency and generation output. During the detailed design stage, the layouts were optimised to increase the generating head and minimise hydraulic head losses in the conveyance system. This was done in a cost-effective manner, improving the annual energy production for low additional capital costs. Also, due to unforeseen geological conditions, the layout at Merino was changed to minimise construction costs.
Deep excavations were undertaken to provide the required back pressure on the turbine blades and thus minimise the cavitation possibility as part load conditions. Blasting was not possible due to the frail geology.
An ingenious horseshoe type spillway was designed to cater for possible floods within a restricted space.
The project delivered a number of firsts for hydropower stations in South Africa including:
Combined, the hydro plants produce 37 000 MWh of clean energy annually, resulting in emissions being cut by approximately 34 000 tons of CO2.
The Bethlehem Hydro project was constructed to international standards and is considered a ground-breaking sustainable project.