(136b) Energy Storage Layouts for Concentrated Solar Plants – A Comparison of Process Control

Energy Storage Layouts for Concentrated Solar Plants ? A comparison of
Process Control

Flavio Manenti^1,*, Zohreh Ravaghi-Ardebili¹, Giovanni
Manenti²

¹Politecnico di Milano, Dipartimento di Chimica,
Materiali e Ingegneria Chimica ?Giulio Natta?, Piazza Leonardo da Vinci 32,
20133 Milano

²FBM Hudson Italiana SpA, R&D Dept.,
Via Valtrighe 5, 24030 Terno d'Isola (BG), Italy

Energy storage is a major process design and
control issue in concentrated solar plants. The intrinsic discontinuous nature
of solar energy forces to install units able to store energy under favourable
conditions, then to release energy during night or unfavourable conditions.
Accordingly, smoothed operations and continuous energy production can be
guaranteed. Several technologies are today available for storage; tanks of molten
salts, steam accumulators, high thermal capacity solids are among the most
important.

Regardless the technology adopted for storage,
the plant layout plays a key role in the process performance and control
philosophy. Control of storage unit and steam generation station under steep
load changes, as during sunrise and clouds passage, depends appreciably on
layout. Storage devices can be installed either on the main process stream or
be part of a secondary circuit linked to the main one; devices can be arranged either
in series or in parallel and, again, devices of different type can be grouped. Fig.
1 shows different layouts for the specific case of molten salts.

This work deals with the comparison of process
control for different storage layouts based on molten salts.  Results coming from process simulations of
unsteady loads are reported and a general discussion on operability and
controllability is done. For this purpose, the different layouts have been
modelled by means of a commercial process simulator (Fig. 2), where specific
fluid properties and units have been implemented. Same investigating approach
can be adopted for storage systems based on different technologies.