The increased interest in solar thermal systems using steam as a working medium either for power generation or process heat applications gave rise to a growing demand for latent heat storage units. Essential for the development of cost-effective latent heat storage systems is the achievement of a sufficient power level in spite of the characteristic low thermal diffusivities of latent heat storage materials. The sandwich concept using fins made either from graphite or aluminum has been identified as the most promising option for latent heat storage systems. The feasibility of this approach has been demonstrated by three prototypes using graphite and one prototype using aluminum fins. The prototype with aluminum fins was filled with sodium nitrate and was operated for more than 4000 h without degradation of power. The volume specific average power density is in the range $10–25 kW/m3$, so it is proven that the major problem of phase change material (PCM) storage of low heat transfer rates has been overcome and high-temperature PCM storage with large capacity factor is possible.

1.
Zarza
,
E.
,
Valenzuela
,
L.
,
León
,
J.
,
Hennecke
,
K.
,
Eck
,
M.
,
Weyers
,
H. D.
-
, and
Eickhoff
,
M.
, 2004, “
Direct Steam Generation in Parabolic Troughs: Final Results and Conclusions of the DISS Project
,”
Energy
0360-5442,
29
, pp.
635
644
.
2.
Janz
,
G. J.
,
Allen
,
C. B.
,
Bansal
,
N. P.
,
Murphy
,
R. M.
, and
Tomkins
,
R. P.
, 1979, “
Physical Properties Data Compilation Relevant to Energy Storage II. Molten Salts: Data on Single and Multi-Component Salt Systems
,” NSRDS-National Standard Reference Data System.