Annual Report 2006 - Plataforma Solar de Almería

CONCENTRATING SOLAR SYSTEMS UNIT
3.2.1 DISTOR
Energy Storage for Direct Steam Solar Power Plants
Participants: DLR (D), CIEMAT-PSA (E), Sistemas de Calor (E), INASMET (E),
IBERINCO (E), DEFY Systemes (F), EPSILON Ingénierie (F), SGL Technologies
GMBH (D), FLAGSOL GMBH (D), Solucar (E), ZSW (D), Weizmann Institute of
Science (Il), and the Central Laboratory of Solar Energy and New Energy
Sources (Bulgaria).
Contact:
Javier León, javier.leon@psa.es
Total budget: 3 036 650€. Co-financed by the EC CE (Contract SES6-CT-
2004-503526)
Duration: February 2004 - September 2007
Motivation: Direct steam generation in the parabolic-trough collector absorber
tubes themselves is a very attractive cost-reducing option for electricity generation
with this type of solar collector. To make solar thermal power plants
more commercial, they must have heat storage systems that allow electricity
production to be disconnected from the hours of sunlight. Thermal storage
systems currently available for solar thermal power plants are based on materials
that increase in temperature (sensible heat) and are inappropriate for
direct steam generation solar systems. That is why a specific solar thermal
storage system must be developed for solar fields with direct steam generation.
Purpose: Development of a competitive thermal storage system suitable for
solar plants working with direct steam generation in parabolic-trough collectors.
Since most of the thermal energy in the steam is released when it condenses,
and this is a process that takes place at a constant temperature, the
appropriate storage system for this type of solar plants must be based on a
medium that is able to absorb heat at a constant temperature. This leads to
the need for a thermal storage system based on latent heat, using phasechange
materials. Several possible options are being studied for a storage
system using phase-change materials, and when the best option has been
selected, a prototype storage module with a rated power of 100 kWt and
200 kWh capacity will be built. This module is scheduled to be installed and
evaluated at the PSA in 2007.
Achievements 2006: In 2006, the PSA DISS plant interface necessary for connection
of the prototype phase-change storage module to be designed and
erected in the project was revised. Figure 3.1 below shows the new interface
design, which will make it possible to test storage charging and discharging
(labeled TES in the figure).
Although the storage prototype to be installed and evaluated in 2007 works
at 40 bar, the interface and its associated instrumentation have been designed
to work at pressures up to 100 bar. This will make it possible to evaluate
future storage models designed for higher operating temperatures (up to
310ºC).
In July 2006, a Collaboration Agreement for development of the data acquisition
and control software necessary for this test facility was signed with
the University of Malaga. The software developed will allow on-line internet
access to test data in real time so they can be quickly evaluated by the other
partners in the project without having to be physically present at the PSA.
One of the problems found in 2006 in the DISTOR project was the need to
install a steam condenser at the storage module outlet to get the proper bal-
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