Trevor Pryor

Novel wind/diesel/battery hybrid energy system

In most of the remote areas of Australia and in many other parts of the world, diesel generators are used to provide electrical power. Such systems are often characterised by either poor efficiency and high maintenance costs because of prolonged operation at low load levels, or intermittent power because the unit is only run during period of significant load. The addition of a battery bank and a power conditioner to produce a diesel-battery-inverter hybrid system has been identified as produccing a number of benefits. Such systems can be broadly classified according to their configuration as series, switched, or parallel hybrid systems. A new parallel hybrid energy system developed in Western Australia is described in this article. The heart of the system is a high quality sinewave inverter which can also be operated in reverse as a battery charger. The system can cope with loads ranging from zero (inverter only operation) to approximately three times the generator capacity (inverter and diesel operating in parallel) with excellent efficiency. The system is fully automatic, provides continuous power, and can readily incorporate input from wind or photovoltaic systems. This article also includes a description of a 5 kW wind generator charging a battery bank as part of the hybrid system, and an economic analysis indicates a favourable result for this hybrid system with payback period estimated to be the order of three years.

The relationship between global solar radiation and sunshine duration in Vietnam

Two approaches of the well-known modified Angstrom formula were developed from long term records of measured monthly mean daily global solar radiation and sunshine hour values obtained from 12 meteorological stations across Vietnam. These formulae were then used to estimate solar radiation for stations where only sunshine records were available. Three other commonly used correlations between solar irradiation and sunshine duration were also used and their results compared with those of two developed models. The procedure of measurement in Vietnamese weather stations was also indicated.

Field and laboratory studies of the stability of amorphous silicon solar cells and modules

If photovoltaic solar cells and modules are to be used as a major source of power generation it is important to have a good knowledge and understanding of their long-term performance under different climatic and operating conditions. A number of studies of the long-term performance of commercially available photovoltaic modules manufactured using different technologies have now been reported in the literature. These have shown clear differences in the seasonal and long term performance and stability of different solar cell techniques. In addition to general module engineering factors that result in a loss of performance in all modules some types of solar cells, such as those made from thin film amorphous silicon (a-Si:H), also suffer specific losses in performance due to fundamental material changes, such as photodegradation or the Staebler–Wronski effect (SWE). A field evaluation of the long term performance of state-of-the-art crystalline and amorphous silicon photovoltaic modules in Australian conditions is currently being undertaken at Murdoch University. The initial results from this monitoring program are reported. This paper also reports on laboratory and field studies being undertaken on the nature of the Staebler–Wronski effect in amorphous silicon solar cells and how the stability of these cells is affected by different operating conditions. Based on a mechanism for the SWE in a-Si:H solar cells developed as a result of our research we propose a number of possible ways to reduce the Staebler–Wronski effect in a-Si:H solar cells.

Investigation of capacitor-excited induction generators and permanent magnet alternators for small scale wind power generation

This paper examines two electric generator options for use in autonomous wind systems producing asynchronous electric power. The first makes use of a capacitor-excited squirrel-cage induction generator feeding a battery bank and an induction motor driven centrifugal pump. The second uses a permanent magnet alternator. Results obtained from field tests and laboratory experiments are included. A model to calculate the wind energy captured by a commercial 5 kW wind turbine, used in the field tests, is presented. This information is then used in a cost benefit analysis based on the present value method.

A user oriented simulation model for deep bed solar drying of rough rice

A computer model based on mass and energy balance has been developed which incorporates a range of solar flat plate air heating collector geometries and a drying model based on the thin layer drying principle. This model will be useful in understanding the extreme complexity of the drying process which is influenced by many design parameters. The developed model will also be helpful as a decision making tool in assessing suitable solar collector design options to meet the desired drying requirements. The collector and drying models have been tested separately for a wide range of operating conditions. A description of the models and their assumptions, together with some simulation results for rough rice drying are presented in this paper.

Feasibility of solar hot water systems in Vietnam

This study describes the prospects for solar hot water systems in Vietnam. Changes in domestic energy consumption, both in terms of quantity and patterns of usage, particularly the increase in electricity use for hot water systems, are expected. VIETSIM, a computer program for simulating solar hot water systems in Vietnam will be described. This program has been validated by comparing the results of this program with those from the well-known TRNSYS program and shown to be highly reliable. The feasibility of SHWS will be studied for both the domestic and commercial sectors. For the domestic sector, the feasibility of SHWS will be studied for medium size families in three locations, representing the main climatic types in this country. The optimum criteria for designing SHWS in this sector are also investigated. For the commercial sector, a case of a hotel/office building is analysed and it is shown that the application of SHWS is very feasible due to high electricity prices for the commercial sector. With the natural advantages of high solar intensity, the social advantages of having plentiful and cheap human resources, and an economic environment with high energy and capital inflation, the use of solar hot water systems in this country can be very favourable if the government has the correct policies to encourage this application.

A computer model to estimate solar radiation in Vietnam

The scarcity of hourly solar radiation data for locations in Vietnam presents difficulties in using simulation packages for assessing the potential of solar energy systems in that country. This paper describes a computer model to generate daily and hourly solar radiation sequences from monthly average daily radiation values, or monthly average daily sunshine hour data. The resulting model has been tested in a number of ways. The statistics of the real and generated sequences were compared. Also the two data sequences have been used in simulation packages and design program such as f-chart and the performance of solar hot water system for the two cases compared. The results of these comparisons are also reported in this paper.

Combining simulation techniques and design expertise in a renewable energy system design package, RESSAD

Computer simulation is an increasingly popular tool for determining the most suitable renewable energy system type, design and control for an isolated community or homestead. However for the user without any expertise in system design, the complicated process of system component and control selection using computer simulation takes on a trial and error approach. Our renewable energy system design package, RESSAD, has been developed to simulate a wide range of renewable power supply systems, and to go beyond system simulation, by combining design expertise with the simulation model. The knowledge of the system designer is incorporated into the package through a range of analysis tools that assist in the selection process, without removing or restricting individual choices. The system selection process is analysed from the early stages of renewable resource assessment to the final evaluation of the results from a simulation of the chosen system. The approach of the RESSAD package in this selection process is described and its use is illustrated by two case studies in Western Australia.

Demonstrating remote area power supply systems on the World Wide Web

One of the primary advantages of the internet is its ability to enable flexible, 24-h access to up-to-date information, irrespective of the geographic location of the user. It is thus rapidly becoming an important tool for the dissemination of information on a global scale. In order to take advantage of the increased accessibility available through the internet, the Murdoch University Energy Research Institute has developed an internet-based version of its physical renewable energy remote area power supply (RAPS) demonstration system. In this way, the physical site, which aims to inform the community about the cost, performance and reliability of renewable energy systems by enabling them to visit a practical operating RAPS system, is available to a much larger audience. The internet-based site, WebRAPS, contains a number of features including case studies of the three RAPS systems at the physical site, specifications of the components used in the systems and general information about the renewable energy system technologies. It also displays historical and real-time data from a monitoring system integrated with the largest of the physical RAPS systems. Visitors to the internet site are able to see how the RAPS system is operating, almost as well as if they were present at the physical site itself. This paper demonstrates the features of the WebRAPS site and discusses how it was developed.

Experiences with lead/acid battery management in remote-area power-supply (RAPS) systems

Battery management and general storage performance and cost remain major problems in remote-area power-supply (RAPS) systems utilizing renewable energy sources. A brief review of field experiences with lead/acid batteries is presented, together with results from battery tests carried out in the laboratory. It is recommended that further collaboration between battery manufacturers and system designers is established to develop improved storage systems for RAPS applications.