5 MW preproduction plant

The literature suggests that the next step is to build a demonstration plant of 5 MWe to establish life cycles of major components.

Much of the design work has already been completed.

See details: by Vega and Nihous, Pacific International entre for High Technology Research. Design of a 5 MWe OTEC Pre-commercial Plant

It will then be possible to construct 100 MWe floating plants. Design work by Sea Solar has begun on the 100 MW plant ship. Shown below is the Sea Solar Power 100 MW hybrid cycle OTEC . See brochure: 100 MW OTEC.

Sea Solar OTEC

Inputs:
227 m3/s at 27 ºC
142 m3/s at 4.4 ºC

Outputs:
100 MW electricity
120,000m3/day fr'sh water

Dimensions:
152 m long
47 m wide
61 m high
25,400 tons

Images adapted from Sea Solar Power.

Image source: NREL

The OTEC cycle using Rankine Cycle. Image source: Xenesys

Image source: Xenesys

Surface Condenser for Desalinated Water Production (1993-1998)
Image source: Hawaii Govt.

Image source: Stanford

Ocean Energy for Sustainable Townsville

Is Townsville positioned to become the leading international centre for the research, development and commercialisation of the ocean based renewable energy technology, OTEC?

OTEC (Ocean Thermal Energy Conversion) is an technology that has long been considered a potential source of low-cost, carbon-neutral, base-load electricity as well as bulk desalinated water.

Whle OTEC technology has been under development for over sixty years, the commercialisation of the technology has not yet been achieved.

As the global price of energy increases in step with concern for reducing greenhouse emissions, perhaps a valuable opportunity presents itself for Townsville to take the lead in forming an international consortium to complete the excellent work commenced by OTEC researchers and developers around the world.

Ocean Energy for Sustainable Townsville Townsville held its first OTEC workshop on 29 September, 2005. Sponsored by SEA O2 Sustainable Development and under the aegis of the Society for Sustainability and Environmental Engineering (a Society of Engineers Australia), the workshop considered the opportunities for Townsville to become an international centre for the development of OTEC technology, and the potential for OTEC to solve Townsville's energy and water needs. The key elements of the workshop were a presentation on the engineering and environmental aspects of OTEC by Dr Peter Ridd (pictured right) from James Cook University.

Special thanks to Townsville Port Authority for use of their excellent conference facilities.

Download OTEC Workshop Agenda

Minutes from OTEC workshop
Guy Lane as new chair of North Queensland Society for Sustainability and Environmental Engineering
Chair introduction how he came to know OTEC technology
review of agenda for evening
introduction to Dr Peter Ridd

Presentation by Peter Ridd
background, interest in renewable energy
OTEC interest in 1975/76 during energy crisis
global interest collapsed after oil prices fell
OTEC not well known renewable compared to solar, wind etc

overview of heat engines - OTEC is a very large heat engine
all engines need is a cold end and hot end, and take energy out of system
classic engines, rankine cycle (type of system needed for OTEC, as well as organic rankine cycle engine at use in the artesian basin - Birdsville)
use ammonia as working fluid - at right pressure, liquid phase or vapour
overview of rankine cycle
require 20 degrees celcius difference between hot and cold end
OTEC requires pipe down to depths - 500 to 700 m deep
the ocean is on average 4 km deep and cold about 4 degrees
there is a tiny bit of the ocean, the surface waters in the tropics where the water is warm
queensland coast - temperature outside shelf always over 24 degrees, and has cold water in depths
after 700m, rate of temp drops less steeply, 750m a good number
temp drops similar in all oceans
Townsville, at latitude 19, is at southern end of ocean temp range required for OTEC
karnot efficiency - limits efficiency of heat engines (differential between hot and cold end)
OTEC efficiency around 3-4%
other problems is power cable to mainland, moorings and permits, salt water environment
floating OTEC, or OTEC on continental shelf (or on land)
consideration of the figures for a 1,000MW plant

Frank Dallmyer , Wayne Hickey and Peter Chapman consider the potential opportunities for OTEC in Townsville.

Group Discussion
risk assessment - thousands of litres of ammonia, size of structure would be much greater than what is currently on reef (pontoons), more like the size of an oil rig
consideration of environmental risks
1. installation esp. pipes and moorings 2. operation eg. water discharges 3. accidents (eg spill of ammonia)
ammonia should evaporate quickly from the sea surface if spilt
structure not necessarily the killer, but nutrients on the reef (community interest)
effect of nutrient on fishing (esp game fishing- black marlin, off Cairns) building into development discharge at equivalent ocean temp
what lives in the ocean 750 metres below sea level?
Giant squid? Billfish?
life of structure, and maintenance costs
20-30 year life - same as a ship
cf. power station life of 50 years
What about using waste discharge from power plants and industry to create the heat differential for power production - less flow, but already flow rate, or temp differential between rivers and ocean
hybrid scheme - heat water using the sun and use cold water
what about using cold water to cool surface water - as a potential solution to coral bleaching
GL- describes discussions with Sea Solar about fully funded plant 100 MW - just needs needs power purchase agreement
Unlike most renewables, OTEC runs 24h a day and thus could be used as base load power
120ML of freshwater a day
what about using the system to use with cooling water of coal power stations, like at mt isa
use this as proof of system - eg 10MW
Cooktown needs 40 MW and has its own grid
need energy demand, Cooktown and Cairns would not use up 100MW
possibility of putting an OTEC plant on shore and running the pipe to the shelf
consideration of the size of the water pipes?
10 metres diameter
the recent water pipe laying process between Pallaranda and Magnetic Island
8 km pipe costs many millions of dollars and was only 30cm diameter
Solomon islands - only want 50MW, prove system at smaller scale

reviewed history of OTEC, Sea Solar, Indian and Taiwanese proposal
Potential to have Sea Solar President in Townsville to discuss suitability of Townsville as a base for Pacific OTEC
use discharge plume as artificial reef, other uses for OTEC platform
could you circulate ammonia rather than sea water - yes, but need same flow rate
OTEC would not be supported in NQ because of costs - needs large proponent, security of investment and returns, cost of contractors - salt water environment, infrastructure costs, (cable costs around $8000/m), transmission loss - no more than 5km from generation site, cannot run AC cable for very long, need to convert to DC, cost of energy going down with deregulation of energy market

Tasmania, DC cable for around 250km, to keep loss down
build onshore, big plastic pipe, 20-30MW, may get up (pacific island ideal)
what takes less energy to transmit - electricity or water
heat water with solar, and use difference between bay water and heated solar water - go down south
ratio between hot and cold water required roughly equal (1.5:1)
what is running costs? Peter Ridd says he thinks it would be relatively high
cost of installed power cheaper - maybe OTEC comes later when RECs, or carbon trading mechanism becomes established
demand in pacific island, where they have to import fuels
talk finished at 6:30pm

Outcomes of the OTEC Workshop

The workshop provided a thorough consideration of the OTEC technology, its application to Townsville and North Queensland and the opportunities for an OTEC base in TOwnsville with focus on the South Pacific Islands.

Townsville an unlikely location for OTEC plants because distance between land and the continental shelf would make costs of transporting power to shore prohibitive, plus, Townsville has more easily exploitable energy sources close to hand, ie gas fired power stations.

Cooktown and North, OTEC would make more sense as the shelf is much narrower and energy sources not so apparent.

Smaller plants could play an important role in the sustainable development of the South Pacific Islands.

Rigorous environmental management would necessarily be mandated and a view that the risks could be managed.

Operation impacts on coral reefs of particular concern.

Costs of OTEC water and power are unknown and a missing factor from the conversations.

Townsville identified as a very suitable location for base of OTEC considerations for the South Pacific because of

There is sufficient interest amongst members of the group to form an informal OTEC working group.

Agreement for Chair to make a CD of all the available OTEC information and make available for the workshop participants and others.

Workshop co-ordination, minutes and photography by Damien Sweeney.

OTEC Internet Resources

Schematic of OTEC system
Image source: WEC

A vision for Townsville's Energy Future might include an ocean energy farm of 100 OTEC plants located 100 km offshore each producing 100 MW of base load power with a subsea cable feeding into the mains grid near Townsville. We call this vision one hundred by three.

Additional uses of OTEC Infrastructure
Around the world, OTC plants have been considered for a range of uses adittional to producing electricity. An assessment of the potential opportunities associated with offshore OTEC plants might include: