Manuel Romero

Performance Analysis of Direct Steam Generation-Central Receiver Systems

This work presents a comparative study between direct steam generation central receiver solar power plants working at live steam conditions similar to those found in commercial plants. PS10 and PS20 by Abengoa Solar use a single-receiver, producing saturated steam, whereas Sierra SunTower by e-Solar and Ivanpah Solar Electric Generating System (ISEGS) by BrightSource use dual-receiver technology producing superheated steam.The system analysis includes individual studies for each subsystem: solar field, receiver and Rankine power block; as well as the overall-analysis of a 66.7 MWth plant. PS10 working conditions were analysed with and without intermediate reheat step. It was assumed that Sierra SunTower-configuration has non-reheat turbine and Ivanpah-cycle includes an intermediate reheat step. The reheat process in PS10 configuration was performed using a fraction of live steam coming from the receiver; while for Ivanpah-configuration exhaust steam from high pressure turbine stage was sent back to the superheated steam section of the dual-receiver. These concepts make possible to avoid hybridisation and assure special regimes (such as Spanish feed-in tariff).The analysis of the heliostat field for dual-receiver concepts reveals that the aiming strategy on the absorbers has not relevant influence on optical performances. However, receiver efficiency decreased from 91.9%, working with saturated steam, to 87.86–84.14% working with superheated steam related to operating temperatures and heat exchange surface area. This study reveals that the improvement achieved in the power block under Ivanpah configuration was able to compensate higher thermal losses at the receiver, increasing net power production by 25.5% compared with saturated steam conditions.© 2012 ASME

Preliminary Analysis of a 100-kWth Mini-Tower Solar Field With an Integrated Optical Waveguide Receiver for Solar Chemistry

Solar-driven thermochemical hydrogen production, CO2 abatement technologies and production of solar fuels and chemicals in general, are candidates in the near future to be scaled-up at solar thermal concentrating facilities in the framework of demonstration projects. Chemical demonstrators undoubtedly will be more demanding in terms of temperature and solar flux than current applications oriented to electricity production. Some of the more promising H2 production technologies are already in the position to scaling reactors up to the 1-MWth level. Demonstration scale useful to develop new solar chemistry processes usually considers input thermal powers between 100 kWth and 1,000 kWth . In this range, the best option is making use of mini-towers with heliostat fields. Then, the challenge is to efficiently introduce high fluxes (above 2,000 kW/m2 ) with a small field of heliostats in solar chemical reactors (usually requiring high temperatures, above 1,000 °C, and high pressures). In order to overcome it, some authors have proposed the use of light waveguides collecting systems for directing concentrated solar light towards a reactor cavity (1, 2, and 3). This solution makes possible the use of a large variety of reactor geometries and to guarantee the reactor tightness even working at high pressures. However it becomes the critical component of the plant design since it largely governs the facility efficiency and configuration due to its optical properties. This work presents the design of a 100-kWth demonstration plant placed in Mostoles, Spain (40° 20′ N, 3° 52′ W) with the concepts mentioned above, in which the light waveguide system is formed by a set of units that are composed by a secondary concentrator and a bundle of optical fibers. This study has paid special attention to optical performances of the facility by analyzing the coupling between solar heliostats field layout and the solar receiver composed by light waveguides. In addition, the paper provides information on sizing, efficiencies and expected investment cost based on light waveguides specifications.Copyright