Development and application of a computerised design tool for remote area power supply systems

Good design of renewable energy electrical systems is essential to the acceptance of this new technology for widespread use. The systems need to be convincing to consumers in terms of performance reliability and cost-effectiveness, when compared to the traditional options of grid extension or a diesel generator. Essential to the selection of a good design is a thorough design approach. The purpose behind this work was to develop a software package that could guide the user in the design process for renewable power systems. The software, known as RESSAD (Renewable Energy System Simulation And Design), had at its core a simulation model, known as RESIM (Renewable Energy SEMulation). The model predicts the performance of renewable standalone and renewable diesel hybrid systems. A system simulation model can be easily misused if there is not a good understanding of the site’s renewable resources and load trends, prior to any simulation, and if the implications of simulation results are not understood. Therefore, to enhance the usefulness of RESIM, a range of design tools were developed for use prior to, and after the simulation. The design tools provide a series of steps that lead to the selection of an initial system design. Industry experience was utilised to establish guiding principles for sound, economical system design. These principles were offered to the user in the form of conclusions on the renewable resource and its relationship to the load, and recommendations for both the system type and the size of components. A broad user group was envisaged for this software, and so the software is user-friendly for the inexperienced designer, while still offering some sophisticated control features. The software also had to be reliable in its predictions and suggestions. This leads to a compromise between model complexity, to ensure sufficient accuracy, and user-friendliness, which entails a minimum number of input data, that are readily available. Validation of RESIM was carried out to establish the level of accuracy that could be achieved with the model. Monitored data from both renewable standalone and hybrid systems were used in the validation process and a comparison was made with another simulation program, PVFORM, in order to further assess the PV model incorporated in RESIM. A need was identified for more reliable monitored data for such validation purposes. Case studies were conducted to test the usefulness of the software, including the design tools. Renewable systems were sized and simulated for three different load ranges at seven Australian locations and the most economical designs were investigated with further simulations. The conclusions from these studies supported this approach in system design, and showed the need for further work to identify design principles, especially for the larger systems meeting loads over 20kWh/day. Economic indicators, such as the net present cost, are the final outcome from the software and viewed as the key determinants of final system design. The validation process indicated the simulation accuracy of RESIM for renewable hybrid systems ranged from 2.5 to 15.5% for diesel operating hours per day and 6.1 to 8.7% for daily fuel consumption. Applying the worst errors to these parameters in the case studies produced errors in the net present cost of 8% for diesel/ inverter systems and under 2.5% for small renewable hybrid systems