Thermodynamic analysis, optimization and validation of the OTEC power cycle. The research consists of modelling and experimental verification of the main operating parameters using advanced software and a small-scale research and demonstration prototype of an OTEC power plant.
One of the crucial components in the thermodynamic cycle of OTEC being studied are the heat exchangers. Large heat exchangers are required to transfer heat from the seawater to the working fluid, both for evaporation and condensation.
At the same time, they have to fulfil high expectations with regard to mechanical strength, weight, size, fouling, corrosion and costs. The main objective of this research is to analyze and develop the most suitable heat exchanger design for OTEC. The majority of the OTEC resource is best accessible using offshore floating structures. Key technical challenges under investigation are the dynamic behaviour of the floating structure and the cold water pipe, its interface and the power cable.
These offshore systems require detailed research to find technical feasible solutions supported by analytical methods and hydrodynamic modeling of mooring - riser - floating structure configurations. UK companies and people interested in this technology do read on, because although the processes may not be suitable for direct electricity generation, indirectly, companies such as BG Group , BP and Shell can exploit existing offshore infrastructure, which includes existing oil and gas rigs located in the warm parts of the world, upgrade for OTEC technology, and supply hydrogen, the next generation fuel, for cars and household boilers to be used all round the world.
OTEC is not like wind power or solar power which are intermittent , because the technology can operate on a basis.
This means that every day, the oceans on our planet absorb solar energy equivalent to billion barrels of oil, and if we could convert 0. OTEC Ocean Thermal Energy Conversion works by using the temperature gradients found in large bodies of water, where the temperature of water found on the surface is significantly higher than the cold water found deeper down.
The largest water temperature gradients exist in tropical oceanic regions, because not only do you have the very warm water, but you also have oceanic depth to make use of cold water currents. These fluids have a low boiling temperature, which when turned into gas, moves the steam into pressurised shafts that are then used to drive turbines. The turbines then drive the generator, which converts mechanical energy into electrical energy. You may now know this part from the heat Rankin Cycle, which underpins electricity generation for current processes such as biomass , nuclear and fossil fuels.
A long pipe accessing the very cold water from the depth of the ocean is used to cool and liquefy the gas back into working fluid, so the process can start again. However, as the resource, which is ocean water, is abundant, an OTEC power station can harness much of the energy it produces by counting on the large volumes of hot and cold water it requires to operate which goes some way to counteract the lack of efficiency problem.
This is when pipework takes in deep water, which is cold. It then harnesses this cold water for district air-conditioning as opposed to using lots of electricity and chemicals seen in current systems. The extensive difference in temperatures found between seawater and air in coastal arctic regions can be exploited using a similar technique to OTEC.
Where ammonia or propane is used in OTEC systems, liquid butane has to be used in arctic locations due to its lower boiling point. Although this technique is in its infancy, the fact that it requires half the amount of seawater extraction pipes compared with the OTEC system makes it potentially less expensive and therefore a more efficient concept. OTEC technology was pioneered in the late 19th century, but it has only been recent technological advances in heat exchangers that have made the technology a viable commercial source of energy.
Sunlight is free and renewable every morning. And scientists estimate that OTEC has the potential to generate billions of watts of electricity. Yet only a few, mainly experimental, plants have been built. One of the problems that restrict OTEC is that the necessary thermal gradient is found at sea, but the power it can generate is needed on land.
In this activity, you will examine some of the issues involved in this dilemma by comparing onshore and offshore OTEC facilities. Examine and compare the two diagrams of OTEC facilities. You can click on each diagram to see a larger image. Once you understand how each of the OTECs work, answer the questions below. OTEC plants built on ships at sea sit right on top of the thermal gradient but face challenges in transmitting the power they produce to shore. OTEC is often hailed as environmentally friendly power, because it is "clean" and renewable.
Describe some of the potential ecologic benefits of this energy source. Last but not least, the cold water can be used in building air-conditioning systems.
You must be logged in to post a comment. The vast baseload OTEC resource could help many tropical and subtropical remote regions to become more energy self-sufficient.
Synergetic products Fresh Water : The first by-product is fresh water. A small hybrid 1 MW OTEC is capable of producing some 4, cubic meters of fresh water per day, enough to supply a population of 20, with fresh water. OTEC-produced fresh water compares very favourably with standard desalination plants, in terms of both quality and production costs.
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