Conceptual design and preliminary analysis of a CSP-biomass organic Rankine cycle plant

Joseph Oyekale;Mario Petrollese;Vittorio Tola;Giorgio Cau

2018-01-01

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Abstract

Sequel to the obvious needs to realize sustainable energy systems in the 21st century, energy experts have been working assiduously to mitigate the fluctuating effects of renewable energy sources, thereby facilitating their dispatchability. One of the strategies currently being employed involves hybridizing two or more energy sources and/or systems. In furtherance of this, a concept has been formulated in this article, aimed at the design and preliminary analysis of a 630 kWe CSP-biomass hybrid plant. The system being proposed consists of linear Fresnel (LF) collectors and biomass furnace in parallel, supplying thermal energy input into organic Rankine cycle (ORC) plant. The solar field has been designed alongside a double-tank thermal energy storage (TES) system, using Therminol SP-I as heat transfer fluid (HTF) and sensible heat storage medium. Biomass furnace burning woody crops constantly supplies specified fraction of thermal energy into ORC, to ensure continuous operation of the system. Thus, with dual objectives of avoiding the start-up/shutdown intermittencies and increasing overall dispatchability of the hybrid renewable power plant, a design methodology has been presented, which adopts concepts that depart slightly from the conventional ones available in literature, in the sizing of solar field and TES tank. Considering thermal contributions from biomass furnace, the solar multiple (SM) needed to achieve full load operations of the power plant on a given design summer day was obtained as 1.47. Then, this SM value was used to simulate plant performance over one year, for preliminary energy and economic assessments of the proposed plant. Annual electrical energy production of the ORC was obtained as 2.77 GWh/year, of which solar energy contributes about 34%. The initial investment cost and annual costs were estimated at about 4 M€ and 181 k€/y respectively, leaving levelised cost of energy (LCOE) at about 187 €/MWh. Relative to existing plants within the same power range, it could be affirmed that the presented scheme and design methodology will enhance energy management in isolated and rural regions, especially where high solar irradiation and woody biomass are abundant.