07 Alternative energy sources (bioconversion energy)

05•02579 Transmission of prices and price volatility in Australian electricity spot markets: a multivariate GARCH analysis Worthington, A. et al. Energy Economics, 2005, 27, (2), 337-350. This paper examines the transmission of spot electricity prices and price volatility among the five regional electricity markets in the Australian National Electricity Market: namely, New South Wales, Queensland, South Australia, the Snowy Mountains Hydroelectric Scheme and Victoria. A multivariate generalized autoregressive conditional heteroskedasticity model is used to identify the source and magnitude of price and price volatility spillovers. The results indicate the presence of positive own mean spillovers in only a small number of markets and no mean spillovers between any of the markets. This appears to be directly related to the physical transfer limitations of the present system of regional interconnection. Nevertheless, the large number of significant own-volatility and cross-volatility spillovers in all five markets indicates the presence of strong autoregressive conditional heteroskedasticity and generalized antoregressive conditional hetero- skedasticity effects. This indicates that shocks in some markets will affect price volatility in others. Finally, and contrary to evidence from studies in North American electricity markets, the results also indicate that Australian electricity spot prices are stationary.

05•02580 Village electrification technologies - an evaluation of photovoltaic cells and compact fluorescent lamps and their applicability in rural villages based on a Tanzanian case study Gullberg, M. et al. Energy Policy, 2005, 33, (10), 1287-1298. Electrification of remote sites in developing countries is often realized trough diesel generator sets and an electric distribution network. This was also the technology used in the village Urambo, where the first rural eiectrifieation co-operative in Tanzania was started in 1994. Climate change however calls for decreased fossil fuel combustion worldwide and new technologies have been further developed since the erection of the diesel generator sets in Urambo. It is therefore not obvious that electrification of other rural areas shall follow the Urambo example. In this article, the situation for 250 electricity consumers in Urambo will be demonstrated and the implications for them of introducing new technologies will be evaluated. Technology options regarded in the study are individual photovoltaic (PV) power systems and either incandescent lamps, tube lights or compact fluorescent lights (CFLs) supplied by diesel generation. The different options have been evaluated with respect to consumer costs and environmental impact. The results of the comparison show that PV generation is able to compete with diesel generation if combined with incandescent lamps, but not when tube lights or CFLs are used in the conventional supply system. It should be noted, however, that while the diesel option offer financially more attractive solutions, individual PV systems do not result in any CO2 emissions. Furthermore, PV systems normally have a higher reliability. However, since the diesel option is not only cheaper but also offers a wider range of energy services and facilitates, future connection to the national electric grid, the conclusion is that this is preferable before individual PV systems for communities similar to Urambo, if the consumers shall pay the full cost of the service.

07 ALTERNATIVE ENERGY SOURCES

Bioconversion energy

05/02581 A new approach for sizing stand alone photovoitaic systems based in neural networks Hontoria, H. et al. Solar Energy, 2005, 78, (2), 313-319. Several methods for sizing stand-alone photovoltaic (pv) systems has been developed. The more simplistic are called intuitive methods. They are a useful tool for a first approach in sizing stand-alone photovoltaic systems. Nevertheless they are very inaccurate. Analytical methods use equations to describe the pv system size as a function of reliability. These ones are more accurate than the previous ones but they are also not accurate enough for sizing of high reliability. In a third group there are methods that use system simulations. These ones are called numerical methods. Many of the analytical methods employ the concept of reliability of the system or the complementary term: loss of load probability (LOLP). In this paper an improvement for obtaining LOLP curves based on the neural network called Multi-

layer Perceptron (MLP) is presented. A unique MLP for many locations of Spain has been trained and after the training, the MLP is able to generate LOLP curves for any value and location.

05/02582 Behaviour of gaseous chlorine and alkali metals during biomass thermal utilisation Wei, X. et al. Fuel, 2005, 84, (7-8), 841-848. The behaviour of gaseous chlorine and alkali metals of three sorts of biomass (Danish straw, Swedish wood, and sewage sludge) in combustion or gasification is investigated by the chemical equilibrium calculating tool. The ranges of temperature, air-to-fuel ratio, and pressure are varied widely in the calculations (T = 400-1800 K, l = 0- 1.8, and P = 0.1-2.0 MPa). Results show that the air excess coefficient only has less significant influence on the release of gaseous chlorine and potassium or sodium during combustion. However, in biomass gasification, the influence of the air excess coefficient is very significant. Increasing air excess coefficient enhances the release of HCI(g), KOH(g), or NaOH(g) as well as it reduces the formation of KCI(g), NaCl(g), K(g), or Na(g). In biomass combustion or straw and sludge gasification, increasing pressure enhances the release of HCI(g) and reduces the amount of KCI(g), NaCl(g), KCI(g), or NaOH(g) at high temperatures. However, during wood gasification, the pressure enhances the formation of KOH(g) and KCI(g) and reduces the release of K(g) and HCI(g) at high temperatures. During wood and sewage sludge pyrolysis, nitrogen addition enhances the formation of KCN(g) and NaCN(g) and reduces the release of K(g) and Na(g). Kaolin addition in straw combustion may enhance the formation of potassium aluminosilicate in ash and significantly reduces the release of KCI(g) and KOH(g) and increases the formation of HCI(g).

05/02583 Biodiesel production from high FFA rubber seed oil Ramadhas, A. S. et al. Fuel, 2005, 84, (4), 335 340. Currently, most of the biodiesel is produced from the refined/edible type oils using methanol and an alkaline catalyst. However, large amount of non-edible type oils and fats are available. The difficulty with alkaline-esterification of these oils is that they often contain large amounts of free fatty acids (FFA). These free fatty acids quickly react with the alkaline catalyst to produce soaps that inhibit the separation of the ester and glycerin. A two-step transesterification process is developed to convert the high FFA oils to its mono-esters. The first step, acid catalysed esterification reduces the FFA content of the oil to less than 2%. The second step, alkaline catalysed transesterification process converts the products of the first step to its mono-esters and glycerol. The major factors affect the conversion efficiency of the process such as molar ratio, amount of catalyst, reaction temperature and reaction duration is analysed. The two-step esterification pro- cedure converts rubber seed oil to its methyl esters. The viscosity of biodiesel oil is nearer to that of diesel and the calorific value is about 14% less than that of diesel. The important properties of biodiesel such as specific gravity, flash point, cloud point and pour point are found out and compared with that of diesel. This study supports the production of biodiesel from unrefined rubber seed oil as a viable alternative to the diesel fuel.

05•02584 Diesel emissions from biofuels derived from Spanish potential vegetable oils Lapuerta, M. et al. Fuel, 2005, 84, (6), 773-780. Methyl esters obtained from the most interesting Spanish oleaginous crops for energy use - sunflower and Cynara cardunculus - were both used as diesel fuels, pure and in 25% blends with a commercial fuel which was also used pure. A stationary engine test bed, together with the instrumentation for chemical and morphological analysis, allowed to study the effect of these fuels on the engine emissions, soluble organic fraction of the particulate matter, origin of adsorbed hydrocarbons, sulphate content, particle nmnber per unit filter surface, and mean particle diameter. Both the consideration of the thermo- chemical properties of the tested fuels and the computations of a chemical equilibrium model were helpful for the results analysis. These results proved that the use of these vegetable esters provides a significant reduction on particulate emissions, mainly due to reduced soot and sulphate formation. On the contrary, no increases in NO,. emissions nor reductions on mean particle size were found.

05•02585 Effect of swirling flow on fluidized bed drying of wheat grains (3zbey, M. and S6ylemez, M. S. Energy Conversion and Management, 2005, 46, (9-10), 1495-1512. In this paper, batch drying of wheat grains in a fluidized bed dryer, which had a swirling flow field in its drying medium, was experimentally investigated. In the experiments, a laboratory scaled fluidized bed type dryer was used. The effects of the swirling flow field on the drying performance were investigated by using an axial guide vane type swirl generator. The effects of the mass flow rate and temperature of the air

378 Fuel and Energy Abstracts November 2005