07 Alternative energy sources (geothermal energy)

chlorine was water soluble and therefore most prohahly ionic species. At YOO‘C. X-60% of the chlorine was still left in the char. At 2tlO C less than 10% of chlorine had evaporated from the fuel, indicating that the chlorine is not associated with water. In addition, there was no significant difference in the chlorine release between biomass and synthetic waste, i.e. a mixture of organic and inorganic chlorides. The results contradict the initial hypothesis and therefore has new implications for the use of these fuels in combustion and gasification processes.

97104752 Remote sensing of carbonaceous aerosol produc- tion by African savanna biomass burning Liousse, C. ef al. J. Geophysical Res., 1997, 102, (D5), 5X95-591 I. The paper presents the estimated annual flux of total and black carbon aerosols emitted by savanna hiomass burning in Africa from satellite data and ground-hased measurements. Smoke plumes were identified using visible, near-la, and thermal IR derived information. In the savanna region, these structures could either decrease or increase the visible albedo of advanced very high resolution radiometer (AVHRR). A hypothesis is advanced claiming that variations of chemical composition and particulate size distribution may create such differences. The SS model simulated radiative transfer through smoke plumes and background atmosphere. Overall uncertainty of the derived aerosol optical depth was 7S%, mainly due to the choice in particulate composition and size distrihution aerosoluhle The affect of the aerosol mixture was also tested. Specific extinction cross sections were calculated using Mie theory applied to different representative aerosol models, allowing retrieval of aerosol columnar concentrations from aerosol optical depth values and integrated aerosol mass loadings in fire plumes. The atmospheric carbonaceous aerosol flux from savanna hurning in Africa was estimated to he 6.5 Tg C/year, which compares with that obtained from emission factor on-site measurements (13 ? 5 Tg C/year).

97104753 The role of biomass as an energy carrier of the future van der Burgt, M. J. Enerb3: W&d, February 1997, 246, 16-17. The article is written in response to a recent meeting to discuss the future of oil. The meeting concluded that production was likely to peak in 2030. then go into decline. The author discusses the role of renewable energy. especially biomass, as a replacement for oil.

97104754 Study of kinetics of gasification of biomass Wu, T. and Wen, W. Tona; Daxue Xuehm, Zirun Kexuehan, 1996, 24. (4) 433-438. (In Chinese) In a thermohalance reactor, chemical reaction kinetics of biomass gasification with carbon dioxide and steam at atmospheric pressure using six types of biomass-char was studied. The mean specific gasification rates were determined The apparent activation energy and the pro-exponential factor was evaluated for all the reactions.

97104755 Use of biomass for energy purposes in Poland in aspect of CO* emission reduction Rogulska, M. el al. Eionuws Energy Environ., Proc. Eur. Bioener~ Conf., 91/r, 1996, 3, 1771-1775. Edited by Chartier, P., Elsevier, Oxford, UK. One of the countries emitting the greatest quantities of greenhouse gases to the atmosphere is Poland. The substitution of fossil fuels with renewable energy sources constitutes one of the strategies to combat this problem. Biomass energy is especially promising. The potential of biomass resources, including combustible hiomass (mainly wood and straw) and liquid hiofuels (alcohol and rape oil esters). for possible to conversion for energy purposes in Poland were estimated in this paper. The assessment of biomass conversion technologies for energy purposes from different viewpoints was discussed and greenhouse gas mitigation potential was estimated.

97194756 Willow firing in retrofitted Irish peat power plants Van Den Broek, R. e/ u/. Biomass and Bioenergy, 1997, 12, (2), 75-90. In Ireland, concern over CO? emissions have caused renewed interest in hiomass electricity. A low-investment-cost option is the firing of locally grown willow in retrofitted Irish peat plants. Various options for such a biomass energy system were evaluated. All steps in the supply chain were integrated in a model and economically optimized. Retrofitting of existing peat plant was compared with building new biomass combustion and gasification plants. All conversion technologies considered are able to co- fire hiomass and peat. Short-term possibilities are given attention in this review. To reflect uncertainties, all costs were presented in ranges. Neither agricultural subsidies nor possible CO? taxes were included. The results reveal that in the lowest co\t estimate, willow firing in retrofitted Irish peat plants has ahout the same cost as peat firing. ($43/GJLHV and 7.4cikW h) and could therefore he a promising technology for CO2 emissions reduction in Ireland.

Geothermal Energy

97104757 Study of possible optimisation criteria for geother- mal power plants Desideri, U. and Bidini. G. Errcr~ Corri~crs. Mgrnr. 1997, 3X. (15-17). IhXl-1691. Geothermal power usage, a renewable energv. could become a more widespread should low temperature liquid-dominated geothermal sources he exploited. Improvements in the performance of geothermal cycles are possible by using closed Rankine and Kalina cycles, whose working fluid may he either a pure substance or a two-component mixture. In this paper three configurations of the Rankinc cycle are examined and compared to conventional single and dual flash steam power plants. The Kalina cycle system no. 12 has also heen studied. Results indicate a potential for performance optimization by modification of the main parameters, such as turhine inlet pressure and type of fluid.

Solar Energy

97104750 Advanced fabrication technologies of integrated- type structure for a-Si solar cells Kiyama, S. et al. Solur Enerb? Marerinb mtd So/or Cell,. lYY7, 4X. ( l-4). 373-38 I. A new fabrication technology for a low-cost integrated-type a-Si solar cell is advanced. Integrated-type cells provide many advantage\ and have been industrialized with a laser patterning method. However. a higher throughput and more efficient patterning method was required for applying a-Si solar cells to a power generating system. Plasma CVM (Chemical Vaporization Machining) was initially applied to advanced patterning because of its high speed and selectivity. In this method. a plasma generated under high pressure localizes near the wire electrode and concentrates reactive radicals. As a result, an etching rate of more than I //m/s was achieved and selective patterning of a 200 /lm-wide a-Si layer in I \ multt- line patterning was also developed for large-area modules.

97104759 Analysis of MPPT characteristics in photovoltaic power system Kawamura, T. et al. Solar Enerp Materiulr and Solur Cells, 1997, 47. ( I-4). 1.5-165. The power conditioner with the function of Maximum Power Point Tracking (MPPT) hy ‘mountain climbing method’ through computer simulations is described. The generated power on the constant voltage control is compared to the one on MPPT with the load matching correction factor (Kpm). This simulation uses the following parameters: the rate of the voltage AV on changing the operating point and of the voltage AI’, on checking the maximum point. As a result, the influence of these parameters on Kpm is showed and it is made clear that we should decide the MPPT parameters with care.

97104760 An analysis of time-dependent spatial distribution of output power from very many PV power systems installed on a nation-wide scale in Japan Murata, A. and Otani. K. S&r ErrerD Materinls urld Solar Cells, 1907, 47. (l-4) 197-202. It is essential to achieve geographical diversity of electric power output for a more rational basis for the promotion of photovoltaic power generation systems diffusion on a large scale. A set of regression formulae was developed to evaluate hourly global irradiance at about eight hundred Japanese sites and the regional distribution of hourly AC electricity output was estimated for many PV systems, based on the assumption that grid- connected 3 kW PV power generation systems are installed on all the roofs of detached houses in principal towns. The smoothing effect of PV output power fluctuation was examined in conjunction with the interconnection capacity hetwcen power grids.

97104761 Annual exergy evaluation on photovoltaic-thermal hybrid collector Fujisawa, T. and Tani, T. Solur Ene~ Mntentrls nml Sohr C~l1.s. 1997. 47. (I-4) 135-148. A photovoltaic-thermal hybrid collector. consisting of a liquid heating flat- plate solar collector with mono-Si PV cells on substrate of non-selective aluminium absorber plate, was designed and constructed. The collector area was I.3 x 0.5 m. Concepts based on the exergy theory were adopted in order to evaluate the thermal and the electrical energy. Annual evaluation based on exergy indicates the PVfT collector can produce higher output density than a unit PV module or liquid heating flat-plate solar collector.

412 Fuel and Energy Abstracts November 1997