• Energy Research

Since Portugal became a member of the then European Common Market-ECE, back in January 1986, much of the traditional agricultural activity in the mountainous territory of the inland of northern and central Portugal was abandoned, because it became uneconomic. This land was mostly transformed into forest and shrublands, representing more than 65% of the Portuguese territory. This change in land use resulted in bigger amounts of wood and biomass by products and residues spread over large parts of the territory that, together with hotter summers, increased the risk of dangerous wildfires that became a major socio–economic issue in the country as a whole. In this paper, we analyze the evolution of the disposal of biomass forest residues and the production of the “electricity from biomass” in Portugal, the technical aspects related to the biomass based power stations already in operation, and also the important logistical operations involved and their wider socio-economic impacts. The results obtained in this analysis point out to several steps to be taken in the future to promote the efficiency of this system, as a powerful tool to obtain a more environmentally sustainable and economically profitable forest in Portugal. Proceedings of the 27th European Biomass Conference and Exhibition, 27-30 May 2019, Lisbon, Portugal, pp. 1565-1570

This study explores the techno-economic potential of rice residues as a bioenergy resource to meet Ghana's energy demands. Major rice growing regions of Ghana have 70-90% of residues available for bioenergy production. To ensure cost-effective biomass logistics, a thorough cost analysis was made for two bioenergy routes. Logistics costs for a 5 MWe straw combustion plant were 39.01, 47.52 and 47.89 USD/t for Northern, Ashanti and Volta regions respectively. Logistics cost for a 0.25 MWe husk gasification plant (with roundtrip distance 10 km) was 2.64 USD/t in all regions. Capital cost (66-72%) contributes significantly to total logistics costs of straw, however for husk logistics, staff (40%) and operation and maintenance costs (46%) dominate. Baling is the major processing logistic cost for straw, contributing to 46-48% of total costs. Scale of straw unit does not have a large impact on logistic costs. Transport distance of husks has considerable impact on logistic costs.

Abstract The aim of this study is to optimise a Portuguese industrial three integrated process system, by studying the effect of some operational and atmospheric conditions on the system. For this main goal it was built a dynamic model, which includes the cogeneration system, the plate heat exchangers and the salt production unit. The cogeneration system was modelled and analysed in GateCycle 5.34.0.r . and the interface variables were used as input of the dynamic model of the remaining integrated process. This model was developed and exploited through gPROMS 2.3 . Some particular issues (start-up, scheduling and atmospheric conditions) were investigated to forecast the performance of the integrated system. The best start-up conditions were established. Several atmospheric conditions were studied and the minimum number of ponds required for each situation was calculated. The scheduling of the evaporation ponds in operation was also investigated to enhance the salt production and to optimise the salt harvesting. The process simulation indicated that it is better to work with the corresponding minimum number of ponds, having a “turbo” pond that receives a larger quantity of heated brine. The efficiency of the cogeneration system (thermal plus electric power divided by natural gas consumption) was approximately 92%. However, the global process efficiency (accounting for energy losses in the evaporation step of the salt production process) was in the range of 70–80%, depending on the atmospheric and operational conditions considered.