This report investigates the feasibility of investing in a hybrid renewable energy system to power a faecal sludge treatment plant used for emergency responses. The work was conducted as a case study in Imvepi, Uganda, where a pilot of a faecal sludge treatment plant for 5 000 people was constructed. The plant is currently running on a diesel generator resulting in high fuel cost and high CO₂ emissions. The aim was to analyse economic and environmental impact of implementing an optimised hybrid energy system using photovoltaic (PV) panels, with or without battery storage (lead acid and lithium-ion). A load profile for the plant was measured at site and used in HOMER Pro simulations software to analyse different system configurations and optimising the net present cost (NPC).

The results showed that it is possible to run the plant with just a PV-system with battery storage. The required PV area can fit as a roof over the sludge drying beds, which anyway need to be covered from rain. This hybrid energy system could save 15 300 litres of diesel fuel per year resulting in a CO₂ emissions reduction of 40 000 kg annually and a levelized cost of energy (LCOE) of 0.20$/kWh. 

A sensitive analysis examined how diesel price, PV-efficiency, load demand, geographical location and PV-tilt angle affect the system. The results indicate that the hybrid energy system can be scaled approximately according to the load demand, and that the NPC are increasing with increased latitude. When changing location from Uganda to Bangladesh and Ukraine, the optimal hybrid energy system needs a diesel generator as backup. For Bangladesh LCOE became 0,25$/kWh and in Ukraine 0.32$/kWh.

A general sized hybrid energy system, valid independent of location, was suggested. The suggested optimal hybrid energy system for the faecal sludge treatment plan is: 52.4 kW PV-system (8°tilt towards south), 25.6 kW inverter, 28 kW diesel generator and 28 kW lithium-ion battery storage giving a renewable energy fraction of 71-93% (depending on location). This comes with an investment of 94 000$ and a payoff between 3.8-5.3 years (depending on location).