Building energy resilience in Western Cape wastewater treatment works

This case study describes the implementation of a hybrid solar PV and battery energy storage system (BESS) at the Hartenbos wastewater treatment works (WWTW) in the Western Cape. The project aims to ensure continuous operation during loadshedding, reduce municipal peak demand, and lower reliance on diesel backup.

• Wastewater treatment works (WWTWs) and water supply are significant energy consumers, representing approximately 17% of total municipal electricity consumption. Because of this, these facilities are high-impact targets for renewable energy (RE) and energy efficiency (EE) interventions to reduce costs, emissions, and the impact of loadshedding.
• The Hartenbos WWTW system consists of a hybrid microgrid installed on a 3.5-hectare site. Technical specifications include 4,536 solar modules with an installed capacity of 2.112 MVA, a battery energy storage system (BESS) of approximately 4.5 MWh (specifically between 4,512–4,586 kWh), a 3.2 MVA PV inverter station, a 2.75 MVA BESS inverter capacity, and a new 11 kV substation. The system also includes a 1.6 MVA integrated generator farm for tertiary backup and is designed for future expansion up to 5 MVA.
• The project was delivered between 2024 and 2025, reaching practical completion in September 2025 and officially launching in November 2025. The reported cost of the project ranges from R100 million to R120 million (with one specific range cited as R100 to R112 million), covering the substation, BESS, PV installation, controls, and civil works.
• The microgrid enables the Hartenbos WWTW to maintain operations during Stage 6 loadshedding by automatically islanding from the Eskom supply. Additional benefits include reduced diesel consumption, lower bulk electricity charges through peak demand reduction, and the ability to export surplus power to the municipal grid.
• Beyond solar and storage, the document identifies several other opportunities to improve energy resilience and efficiency at WWTWs, including the use of variable-speed drives, high-efficiency pumps and blowers, SCADA upgrades for process optimisation, hydropower turbines on gravity pipelines, and biogas recovery with combined heat and power (CHP) where sludge volumes permit.

APA

GreenCape (n.d.). Building energy resilience in Western Cape wastewater treatment works. https://greencape.co.za/wp-content/uploads/2026/03/GEER-Energy-resilience-at-WWTWs-case-study-DIGITAL.pdf

Chicago

GreenCape. Building energy resilience in Western Cape wastewater treatment works. n.d. https://greencape.co.za/wp-content/uploads/2026/03/GEER-Energy-resilience-at-WWTWs-case-study-DIGITAL.pdf.

Wikipedia

{{cite report |author=GreenCape |title=Building energy resilience in Western Cape wastewater treatment works |url=https://greencape.co.za/wp-content/uploads/2026/03/GEER-Energy-resilience-at-WWTWs-case-study-DIGITAL.pdf |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{greencapendbuilding, author = {{GreenCape}}, title = {{Building energy resilience in Western Cape wastewater treatment works}}, institution = {GreenCape}, url = {https://greencape.co.za/wp-content/uploads/2026/03/GEER-Energy-resilience-at-WWTWs-case-study-DIGITAL.pdf}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }