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MPhil in Engineering for Sustainable Development

global challenges, engineering solutions

Studying at Cambridge

Thanura Rabel

An Economic and Resilience Analysis of Hybrid Energy Systems using Optimisation Modelling.

Vanuatu, an archipelago nation located in the South Pacific relies on imported diesel for much of its electricity supply. This dispersed island group faces diseconomies of scale, volatile oil prices and lack of diversity in electricity sources. As a result, the consumers face some of the highest electricity prices in the world. The demand in Tanna Island is growing by 10% per annum and the authorities are increasing diesel consumption to cope. This cannot continue sustainably for a prolonged period. At the same, the Vanuatu Islands are particularly vulnerable to natural disasters. For this reason, a holistic attitude is required in infrastructure development, bringing resilience into the foreground. Hybrid energy systems, which combine indigenous energy resources have proven to be a successful alternative for diesel generation. Their autonomous nature also has potential to provide increased resilience which is geared towards reducing disaster impact.

A hybrid energy system (HES) was investigated for Tanna Island using optimisation tool HOMER, where the 2025 forecasted loads were simulated. A “Business as Usual” scenario was compared against the optimum HES using economic analysis and key indicators such as levelised cost of energy (LCOE). Furthermore, using a systems approach, the resilience of HESs were also investigated by identifying and isolating critical issues. Cyclone Pam was used as a case study. An assessment was then undertaken to understand how HESs can assist in the disaster response.
The analysis demonstrated that the LCOE of the optimum HES is 20% cheaper when compared with the “Business as Usual” ($0.35/kWh vs $0.43/kWh). A sensitivity analysis to grasp the uncertainty also confirmed that the optimum HES (solar, wind, diesel and battery) remains for most of the variations in input parameters such as price of diesel, discount rate, wind speed and lifetime of the components.

The research also revealed that a critical link in which energy infrastructure influences the resilience in the disaster response is through communication infrastructure. Exploiting the autonomous nature of HESs combined with pre-disaster management, resilience based design standards and early warning systems, it was determined that “islanding” the grid has potential to provide an uninterrupted electricity supply through similar hazards. It was recommended  that  an  “emergency”  network  connecting  HES  components  to  critical infrastructure can provide resilience in the event of disasters. This strategy may also prove useful in times where there are maintenance issues and faults.

Access to large capital is a key barrier in renewable technology deployment in Vanuatu. But a larger issue is the lack of evidence and data to contribute towards building a good business case. This research aims to help fill this information gap. It is also envisioned that this research will form evidence for wider application purposes. Scalability in the wider Pacific Islands is a key component as the energy landscape is similar to that of Vanuatu. Furthermore, scalability is also vital for off-grid application as many of Vanuatu’s citizens reside in highly rural environments where grid connected electricity is inaccessible.