1. Harnessing the Potential of
Ocean Thermal Energy
Conversion (OTEC) Application
Author: John O Nabena
Supervisor: Prof. John E Oakey
Cranfield University, College Road, Cranfield Bedfordshire, MK43 0AL.
Supervisor’s email: j.e.oakey@cranfield.ac.uk
www.cranfield.ac.uk/sas/subsea
1. Introduction: Overview of OTEC power generation
OTEC is a marine renewable energy that generates electricity by exploiting the natural temperature gradient existing between the sun-warmed
surface seawater and the colder deep seawater in tropical oceans. It is pertinent to know that the oceans can also be termed as the world’s largest
solar energy absorber because it can store more than 4000 times the total quantity of energy currently consumed in the world on a yearly basis .
Approximately 60 square kilometres of the tropical seas retain a large amount of solar radiation that is equivalent to the heat content of almost 250
billion barrels of oil when OTEC is fully exploited.
2. Aim
The aim of this thesis is to explore the possibilities of incorporating OTEC facilities as a key renewable energy for power generation in Africa (Nigeria)
and also maximise its vast economical benefits.
3. Objectives
● Identify electricity demand in the choice region
● Choice of possible locations for the power plant and how suitable are they
● Review of selected important technologies
4. Conditions for Commercial OTEC Location
● Temperature gradient of about 20° C
● Relative seawater depth of about 1000m
● Tropics between 20° North and 20° South like
Nigeria, Ghana, Togo, Kenya, Angola, Cameroun etc.
● Land based, Attached Platforms and Moored or free floating OTEC plant
5. Principle of Operation.
The closed-cycle OTEC system is the commonest and it uses a working fluid like
ammonia (low boiling point) which is pumped around the closed loop and it comprises
of three basic components: pump, turbo generator and heat exchanger – evaporator
and condenser. Other types includes; Open Cycle, Hybrid Cycle and Kalina Cycle
OTEC system.
. 7. Other Uses of OTEC Technology
● Fresh water production
● Aquaculture and Mari-culture
● Air conditioning and Refrigeration
● Coldwater Agriculture
● Fuel and Mineral extraction
S/N Solar PV Technologies Ocean Thermal Electro
Conversion Technology
1 Solar light energy. Solar heat energy.
2 Requires continuous
maintenance and changing
of panel alignment is
needed in multiple solar
energy collecting panels.
Maintenance here is easier
because an OTEC power plant is in
a shingle location and a good
planned maintenance system
(PMS) will suffice.
3 Direct and continuous
sunlight is needed to run
the system at optimal
efficiency and smoothly.
A direct/continuous sunlight is not
needed as the temperature
gradient between the surface and
ocean depth does not change
rapidly.
4 Its distribution is quite
difficult as batteries are
first needed to store the
energy then re-supplied.
Its distribution is easy as power
output is directly connected to a
main power grid for subsequent
sharing.
5 It stores energy in batteries
which makes it completely
battery independent with
large operational ground
area in sections
It supplies directly to the main
power grid and is confined to a
single large operational section
consisting of mainly a generator.
6 Life span is 20 to 25 years. Life expectancy is at least 30 years.
6. Discussion:
The choice of renewable energy for a developing nation like Nigeria is mainly to boost
its current insufficient power grid and that is why OTEC facilities can be installed in
the Southern part of Nigeria (areas engulfed by Gulf of Guinea – South Atlantic
Ocean) and Solar PV technology can be installed in the Northern parts of Nigeria on
a very large scale where the sun averagely shines about 9 hours of the day.
. 8. Conclusion:
In a bid to tackle the increasing demand of electricity in Africa (Nigeria) and its ever growing
population, renewable energy must be hugely invested in. OTEC has the capability to meet global
demand for environmentally friendly clean energy as well as producing potable water, food and
cooling technology.