Among the renewable energy sources, ocean energy is encountering an increasing interest. Several technologies can be applied in order to convert the ocean energy into electric power: among these, ocean thermal energy conversion (OTEC) is an interesting technology in the equatorial and tropical belt, where the temperature difference between surface warm water and deep cold water allows one to implement a power cycle. Although the idea is very old (it was first proposed in the late nineteenth century), no commercial plant has ever been built. Nevertheless, a large number of studies are being conducted at the present time, and several prototypes are under construction. A few studies concern hybrid solar-ocean energy plants: in this case, the ocean thermal gradient, which is usually comprised in the range 20–25 °C in the favorable belt, can be increased during daytime, thanks to the solar contribution. This paper addresses topics that are crucial in order to make OTEC viable, and some technical solutions are suggested and evaluated. The closed cycle option is selected and implemented by means of an organic Rankine cycle (ORC) power plant, featuring multiple ORC modules in series on the warm water flow; with a three-level cycle, the performance is approximately 30% better if compared to the single-level cycle. In addition, the hybrid solar-OTEC plant is considered in order to investigate the obtainable performance during both day and night operation; this option could provide efficiency benefit, allowing one to almost triplicate the energy produced during daytime for the same prescribed water flow.

References

1.
Special Report on Renewable Energy Sources and Climate Change Mitigation
,”
IPCC
,
2011
, http://srren.ipcc-wg3.de/
2.
IEA
,
2009
, “
Ocean Energy: Global Technology Development Status
,” IEA-OES Document No. T0104.
3.
Bhuyan
,
G. S.
,
2008
, “
Harnessing the Power of the Oceans
,”
IEA Open Energy Technology Bulletin
, 52, available at: http://www.iea.org/impagr/cip/pdf/Issue52GBhuyanArticle.pdf
4.
Nihous
,
G. C.
,
2010
, “
Mapping Available Ocean Thermal Energy Conversion Resources Around the Main Hawaiian Islands With State-of-the-Art Tools
,”
J. Renewable Sustainable Energy
,
2
, p.
043104
.10.1063/1.3463051
5.
Vega
,
L. A.
,
2002
, “
Ocean Thermal Energy Conversion Primer
,”
Mar. Technol. Soc. J.
,
6
(
4
), pp.
25
35
.10.4031/002533202787908626
6.
Ravindran
,
M.
,
2000
, “
The Indian 1 MW Floating OTEC Plant—An Overview
,”
IOA Newsletter
,
11
(
2
), available at: http://www.clubdesargonautes.org/otec/vol/vol11-2-1.htm
7.
Kobayashi
,
H.
,
Jitsuhara
,
S.
, and
Uehara
,
H.
,
2001
, “
The Present Status and Features of OTEC and Recent Aspects of Thermal Energy Conversion Technologies
,”
24th Meeting of the UJNR Marine Facilities Panel
,
Honolulu, HI
, November 4–12.
8.
Renewable Energy Policy Network for the 21st Century,
2010
, “
Renewables 2010 Global Status Report
,” REN21, http://www.ren21.net/REN21Activities/Publications/GlobalStatusReport/GSR2010
9.
Leggio
,
S.
,
2011
, “
Stato dell'arte degli impianti OTEC
,” B.S. thesis, University of Milan,
Milan
, Italy (in Italian).
10.
Angelino
,
G.
, and
Colonna
,
P.
,
1998
, “
Multicomponent Working Fluids for Organic Rankine Cycles (ORCs)
,”
Energy
,
23
, pp.
449
463
.10.1016/S0360-5442(98)00009-7
11.
Bombarda
,
P.
,
Invernizzi
,
C.
, and
Pietra
C.
,
2010
, “
Heat Recovery From Diesel Engines: A Thermodynamic Comparison Between Kalina and ORC Cycles
,”
Appl. Thermal Eng.
,
30
, pp.
212
219
.10.1016/j.applthermaleng.2009.08.006
12.
Bejan
,
A.
, and
Kraus
,
A. D.
,
2003
,
Heat Transfer Handbook
,
Wiley
,
Hoboken, NJ
, Chap. 9.12.
13.
Goto
,
S.
,
Motoshima
,
Y.
,
Sugi
,
T.
,
Yasunaga
,
T.
,
Ikegami
,
Y.
, and
Nakamura
,
M.
,
2011
, “
Construction of Simulation Model for OTEC Plant Using Uehara Cycle
,”
Electr. Eng. Jpn.
,
176
(
2
), pp.
1
13
.10.1002/eej.21138
14.
Hjartarson
,
H.
,
Maack
,
R.
, and
Johannesson
,
S.
,
2005
, “
Húsavik Energy Multiple Use of Geothermal Energy
,”
GHC Bull.
,
26
(
2
), pp.
7
13
.
15.
Herzberger
,
P.
,
Kolbel
,
T.
, and
Munch
,
W.
,
2009
, “
Geothermal Resources in the German Basins
,”
GRC Trans.
,
33
, pp.
395
398
.
16.
Bharathan
,
D.
,
2011
, “
Staging Rankine Cycles Using Ammonia for OTEC Power Production
,” U.S. National Renewable Energy Laboratory (NREL), Technical Report No. NREL/TP-5500-49121.
17.
Zhang
,
H.
,
Wang
,
Y.
,
Peng
,
J.
, and
Sun
,
W.
,
2009
, “
The Design and Control on Intelligent Underwater Cleaning Robot for Power Plant Condenser
,”
Int. J., Model., Identif. Control
,
7
(
4
), pp.
392
397
.10.1504/IJMIC.2009.027895
18.
Uehara
,
H.
, and
Ikegami
,
Y.
,
1990
, “
Optimization of a Closed Cycle OTEC System
,”
ASME J. Sol. Energy Eng.
,
112
, pp.
247
256
.10.1115/1.2929931
19.
Moore
,
F. P.
, and
Martin
,
L. L.
,
2008
, “
A Nonlinear Nonconvex Minimum Total Heat Transfer Area Formulation for Ocean Thermal Energy Conversion (OTEC) Systems
,”
Appl. Thermal Eng.
,
28
, pp.
1015
1021
.10.1016/j.applthermaleng.2007.06.039
20.
Yeh
,
R.
,
Su
,
T.
, and
Yang
,
M.
,
2005
, “
Maximum Output of an OTEC Power Plant
,”
Ocean Eng.
,
32
, pp.
685
700
.10.1016/j.oceaneng.2004.08.011
21.
Sharqawy
,
M. H.
,
Lienhard
,
J. H.
, and
Syed
,
M. Z.
,
2010
, “
Thermophysical Properties of Seawater: A Review of Existing Correlation and Data
,”
Desalination Water Treat.
,
16
, pp.
354
380
.10.5004/dwt.2010.1079
22.
Yamada
,
N.
,
Hoshi
,
A.
, and
Ikegami
Y.
,
2009
,
Performance Simulation of Solar-Boosted Ocean Thermal Energy Conversion Plant
,”
Renewable Energy
,
34
(
7
), pp.
1752
1758
.10.1016/j.renene.2008.12.028
23.
Aspen Plus, Version 2006.5, AspenTech, Burlington, MA.
24.
Thome
,
J. R.
,
2004
,
Engineering Databook III
,
Wolverine Tube Inc.
, Decatur, AL, Chap. 7, available at: http://www.wlv.com/products/thermal-management-databooks.html
25.
Thome
,
J. R.
,
2004
,
Engineering Databook III
,
Wolverine Tube Inc.
, Decatur, AL, Chap. 9, available at: http://www.wlv.com/products/thermal-management-databooks.html
26.
Incropera
,
F. P.
, and
De Witt
,
D. P.
,
1990
,
Fundamentals of Heat and Mass Transfer
,
Wìley
,
New York
, Chap. 8.
27.
Wang
,
T.
,
Ding
,
L.
,
Gu
,
C.
, and
Yang
,
B.
,
2008
, “
Performance Analysis and Improvement for CC-OTEC System
,”
J. Mech. Sci. Technol.
,
22
, pp.
1977
1983
.10.1007/s12206-008-0742-9
You do not currently have access to this content.