This study conducted a detailed technical analysis of small-scale solar–bio-hybrid power generation systems using Rankine (steam turbine) and Brayton (gas turbine) cycles. Thermodynamic models were developed to characterize the state of working fluid and select the most suitable solar collection technology for individual power generation systems. Net capacity factor of power generation and utilization efficiencies of solar and biogas energy were used as parameters to evaluate energy generation and conclude the preferred system configuration. The analysis concluded that the steam turbine system has better global efficiency (67.7%) than the gas turbine system (55.7%), while the gas turbine system has better electricity generation efficiency (27.0%) than that (5.6%) of the steam turbine system. The effects of different climates on the selection of suitable hybrid systems were also investigated to delineate suitability and feasibility of different hybrid systems. In addition, the method used in this study can also be applied to investigate and optimize other small-scale hybrid renewable energy generation systems.

Pineapple production around the world creates large amounts of wasted organic residue, mainly in the form of pineapple leaves. Current management practices consist of in situ decomposition or in situ burning, both of which cause the proliferation of flies and air pollution, respectively. The research conducted aims to develop a utilization process for this residue. Considering that pineapple leaves are rich in carbohydrates and other nutrients, a simple biological process involving a two-step procedure for juice production and ethanol fermentation has been developed to convert the leaves into renewable fuel and spent yeasts for animal feed. The liquid fraction extracted from the leaves is used as the nutrients to culture yeast, Kluyveromyces marxianus, for ethanol and yeast protein production. In Costa Rica, one of the major pineapple-producing countries in the world, the studied process can produce 92,708 and 64,859 tons of bioethanol and spent yeast per year, respectively, from its 44,500 hectares of pineapple plantation. This techno-economic analysis indicates that a regional biorefinery with the capacity to produce 50,000 metric tons per year of ethanol could have a short payback period of 4.72 years. The life cycle analysis further demonstrates the advantages of the studied biorefining concept over the current practice of open burning.