Giovanni Manente

Hybrid Solar-Geothermal Power Generation to Increase the Energy Production from a Binary Geothermal Plant

This article examines how hybridization using solar thermal energy can increase the power output of a geothermal binary power plant that is operating on geothermal fluid conditions that fall short of design values in temperature and flow rate. The power cycle consists of a subcritical organic Rankine cycle using industrial grade isobutane as the working fluid. Each of the power plant units includes two expanders, a vaporizer, a preheater and air-cooled condensers. Aspen Plus was used to model the plant; the model was validated and adjusted by comparing its predictions to data collected during the first year of operation. The model was then run to determine the best strategy for distributing the available geothermal fluid between the two units to optimize the plant for the existing degraded geofluid conditions. Two solar-geothermal hybrid designs were evaluated to assess their ability to increase the power output and the annual energy production relative to the geothermal-only case.Copyright

Dynamic Modeling of the Microalgae Cultivation Phase for Energy Production in Open Raceway Ponds and Flat Panel Photobioreactors

A dynamic model of microalgae cultivation phase is presented in this work. Two cultivation technologies are taken into account: the open raceway pond and the flat panel photobioreactor. For each technology, the model is able to evaluate the microalgae areal and volumetric productivity and the energy production and consumption. Differently from the most common existing models in literature, which deal with a specific part of the overall cultivation process, the model presented here includes all physical and chemical quantities that mostly affect microalgae growth: the equation of the specific growth rate for the microalgae is influenced by CO2 and nutrients concentration in the water, light intensity, temperature of the water in the reactor and by the microalgae species being considered. All these input parameters can be tuned to obtain reliable predictions. A comparison with experimental data taken from the literature shows that the predictions are consistent, slightly overestimating the productivity in case of closed photobioreactor. The results obtained by the simulation runs are consistent with those found in literature, being the areal productivity for the open raceway pond between 50 and 70 t/(ha*year) in Southern Spain (Sevilla) and Brazil (Petrolina) and between 250 and 350 t/(ha*year) for the flat panel photobioreactor in the same locations.

Energy Integration in the cement industry

Cement production is an energy intensive industrial process that requires heat to be supplied at high temperature levels under the constraints of gas-solid heat exchange phenomena and the kinetics of chemical reactions. In this paper, the use of Pinch Analysis and Process Integration techniques to optimize the energy efficiency of the cement production will be explored. The aim is to use process modeling to characterize cooling and heating requirements of the process, focusing on the gas-solid heat exchanges while including waste fuel utilization. The heat cascade model is adapted to account for gas-solid and gas-gas heat recovery used to calculate the heat recovery in the process. A mixed integer linear programming problem is solved to calculate the integration of the available heat; this model optimizes the heat recovery and the energy conversion efficiency considering different fuels, heat recovery options and process operating conditions.