Miroir cylindro-parabolique | EPFL Graph Search

Le miroir cylindro-parabolique est une des variantes du collecteur solaire thermique. Description Il est constitué d'un long miroir (généralement recouvert d'un plaquage en argent ou en aluminium poli), rectangulaire, en forme de cylindre parabolique et, complété par un tube à double enveloppe sous vide (tube Dewar) qui court sur toute sa longueur le long de la droite focale. Les rayons solaires sont reflétés par le miroir pour converger sur le tube Dewar. L'alignement des panneaux peut être :

statique selon un axe primaire nord-sud et pivotant dans le plan perpendiculaire correspondant, de façon à suivre un plan de la course elliptique du Soleil au cours de la journée.
alignée selon un axe est-ouest. Dans ce cas l'efficacité du collecteur est diminuée en proportion du décalage angulaire conjugué, mais cette configuration peut être choisie si l'on préfère supprimer le moteur de positionnement perpétuel (et sa maintenance). Dans cette configuration, on corrige l'orient

Preliminary Study of a Solar Trough/Tower Power Plant

Jorge López Moreno

The possibility of combining both the advantages of a solar tower thermal power plant and of a solar parabolic trough power plant could be interesting from an energetic point of view as well from an economic point of view. The preliminary study of this combination feasibility is the goal of this project. The study of the project viability consist first of all on the modeling of the trough system, the energy balance of the parabolic troughs will be established at first. Secondly, and choosing a perfect solar day simulating a day when the solar radiation is rather stable, with no cloudy periods along the day, the power available from the trough plant can be calculated. Once we have estimated the power that we can introduce into the cycle of the tower plant, the main issue consists on how and where it is better to use this energy in the cycle. Several possibilities seem to be interesting a priori, however a more detailed study of each one is to be done in order to get to the most economic and efficient layout. The work related to the tower thermal power plant will be done taking as starting point the master thesis of James Spelling, who did an incredible work in this field and whose work will be a valuable help to continue the research on the proposed concept in this project of combining two plants, tower and trough. The main advantage of the tower design compared to the parabolic trough design is the higher temperature. As it will be explained further, thermal energy at higher temperature can be converted more efficiently, the exergy efficiency is better. In terms of storage, the high temperature results in a cheaper and a more efficient storage system. Nevertheless, the set up of the field of heliostats is more complex than the set up of the parabolic trough lines even though the area for a trough plant must be previously flattened. The lower temperature level that entails an inconvenient itself for a parabolic trough power plant may become an advantage when combining both types of concentrating solar power plants. If the results are positive enough that it seems interesting to combine both types of power plants, another step forward will be done towards the use of the sun energy as a renewable source thus making it a more interesting choice for power generation. Sun potential has already shown as an important technology not only at the present time but also in the future. Commercial solar plants have already achieved levelized energy costs around 12-15 UScts/kWh, and the potential for cost reduction is expected to follow this trend even further, to costs as low as 5 UScts/kWh. In addition the taxes imposed for the non-green power should make even more interesting the use of concentrating solar power plants. The requirements of high beam normal radiation lead to a limited amount of suitable places where the implantation of this technology is possible. However many places exist on Earth where the conditions are perfectly adapted, we talk about regions such as United States (the country with more carbon dioxide emissions in the world), some regions in Mexico, North Africa, India, Australia, northeastern Brazil and some locations around the Mediterranean, especially in the south of Spain. The challenge is therefore set for a change in our energy production scheme.

2010

Thermo-economic optimisation of a tower/trough combination solar power plant

Jorge López Moreno

Today a crude oil barrel has five times the prize it had fifteen years ago, moreover, we have increased our global energy consumption by almost 40 percent since then and population growing rates are higher than ever before. In addition, recent tragic events in Fukushima nuclear power plant, Japan, earlier this year, have increased concerns even more about energetic schemes based on nuclear energy. This challenging energetic context requires rapid, economically feasible and reliable progress in the field of renewable energies. We have the great responsibility today of building the energetic scheme of tomorrow. Amongst renewable energies, thermal solar energy has already proven both reliable and competitive with adequate feed-in tariffs and offers some key advantages such as the possibility to store the energy as well as the good controllability of the transformed energy, which entails a great connectivity to the grid. The goal of this project is to perform a thermo-economic analysis and optimization of a solar thermal power plant combining both a tower and parabolic trough power plants and to find out whether or not the combination of these two (with different temperature levels) is advantageous from an energetic or an economic point of view. This idea is fairly innovative and no previous studies have been found on this particular research line. A new, detailed model has been developed for the trough power plant not only for the thermal side but also for the hydraulic and economical side. This model has been then combined with an existing model for the tower power plant. Afterwards, a performance analysis and a multi-objective optimization of the combination have been carried out. Energetic integration, modelling of the power cycles and multi objective optimization all have been performed using LENI tools to analyze and optimize energetic systems such as Energy Technologies and MOO. Trough – tower combination solar power plants present several advantages both from an energetic and economic perspective. Combination power plants feature important efficiency gains compared to either the tower or the trough power plant individually. This efficiency gain comes from the sake of combining both types of power plants, allowing better cycle efficiencies. Efficiency of these combined trough- tower power plants can reach 18.7% (solar to electricity) for certain combinations, with a levelised energy cost of 15 UScts/kWh. Other interesting combinations have been pointed out, for instance, an 80 MW combined power plant, with an efficiency of 16.9% and a levelised energy cost of 8.8 UScts/kWh which is fairly impressive compared to the current solar thermal power plants. Many different interesting combinations can be imagined, each one offering particular advantages. This project confirms that trough – tower combination, when properly integrated, result into more efficient, with a lower levelised energy cost with respect to tower schemes and larger power plants than either tower or trough schemes separately. This new possibility definitely contributes to make solar thermal power an even more promising and interesting technology.

2011

Preliminary Study of a Solar Trough/Tower Power Plant

Jorge López Moreno

2010

Thermo-economic optimisation of a tower/trough combination solar power plant

Jorge López Moreno

2011