Energy Constraint and Adaptability: Focus on Renewable Energy on Small Islands
Thesis DisciplineMechanical Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Renewable energy integration into diesel generation systems for remote island communities is a rapidly growing energy engineering field. Fuel supply issues are becoming more common and the disruption, instability and panic caused by fuel shortages results in inefficient and unreliable power supplies for remote island communities. This thesis develops an energy engineering approach for meeting renewable energy development, supply security, cost and sustainability objectives.
The approach involves adapting proven energy engineering techniques including energy auditing, energy system modelling with basic cost analysis and demand side management. The novel aspect of this research is the development of critical load engineering in the system design, and informing this with an assessment of essentiality of energy services during the audit phase. This approach was prompted by experiences with previous fuel shortages and long term sustainability policy drivers.
The methodology uses the most essential electric loads as the requirement for sizing the renewable energy capacity in the hybrid system. This approach is revolutionary because communication with the customers about availability and the need to shed non-essential loads helps to both meet cost and security requirements and to reduce levels of panic and uncertainty when fuel supply issues arise.
A sustainable power generation system is a system that provides continuity of supply for electrical appliances that are considered by the residents to be essential and for which adaptability and resilience of behaviour were key design priorities over growth. The sustainable electrical energy supply should match the critical (essential) load and should have the ability to continue without major disruptions to the daily lives of the people in these communities. Essential energy end uses were identified through energy audits and surveys. The electric power system is designed so that renewable energy sources alone can meet that “essential” demand with a plant that is both economically and technically feasible. Diesel generators were supplemented to meet the short fall in meeting the unconstrained electric demand. This is to design a system that is generally competitive with the present conventional power generation. This method should be particularly suitable for handling the complexities of a modern-day energy system in terms of planning a sizable sustainable energy and electricity system, either based on wholly sustainable sources or integrating sustainable sources of energy into a conventional generation system. The final hybrid system chosen after numerous simulations for the case study (Fenfushi island in the Maldives) community has the minimum renewable energy sources to meet the essential load but uses diesel to supplement the present load. A variety of design parameters such as PV size, wind turbine sizes and numbers and battery capacity have been considered. The minimum renewable energy sources to supply the essential loads of the community were simulated with diesel generators to find the optimal supply mix for the present load (typical unconstrained demand). The final outcome has the following characteristics: NPC and COE were $1,532,340 and $0.37/kWh respectively, lower than any diesel-only systems that could supply the demand. The total annual electricity production is 386,444 units (kWh), of which 9.61% is excess electricity and the annual operating cost is $68,688. Compared to the diesel-only systems there is a fuel savings of 77,021 litres of diesel per year, which is a 66.5 % reduction. An annual carbon dioxide emission reduction of 202,824 kg was achieved, which is a reduction of 66.5%. An annual renewable energy contribution of 70% would be achieved, 34% of which would be from PV arrays and 36% from wind turbines. The selected system shows that even with 30 percent power supply from diesel generators, still the highest NPC is on diesel generation for a life of over 25 years.