Ocean themal energy conversion

‘OTEC’

Presented By-Sandeep Kumar Tiwari12EEE42

ContentIntroductionDiscoveryWorking PrincipleTypesAdvancementsCost & EfficiencyOperating Plant in PresentAdvantagesDisadvantageFuture scopeConclusionReferences

INTRODUCTION• OTEC, Ocean Thermal Energy Conversion is an energy

technology that converts solar radiation to electric power. • OTEC utilizes the world’s largest solar radiation

collector.• The ocean contains enough energy power all of the

world’s electrical needs.• OTEC is a way to generate electricity using the

temperature difference of sea water at different depth.

DISCOVERY

In 1881 Jacques Arsene d'Arsonval, a French physicist, was the first to propose tapping the thermal energy of the ocean. In 1930 Arsonval built an experimental open cycle OTEC system at Matazas Bay, Cuba. The system produce 22 KW of electricity.

WORKING PRINCIPLEOTEC utilizes the ocean’s 20ºC natural thermal gradient between the warm surface water and the cold deep sea water(around 1 Km.) to drive a Rankine Cycle.

OTEC PROCESS

2. Fluid pump pressurizes and pushes working fluid to evaporator

1. Power input to pumps to start

process

3. Heat addition from the hot-water source used to evaporate the working fluid within the heat exchanger (Evaporator)

EVAPORATOR

CONDENSER

WARM SURFACE WATER 28 C

4. Expanding vapor drive the turbine, and electricity is created by a generator

5. Heat extraction from cold-water sink to condense the working fluid in the condenser.

TURBINE

GENERATOR

COLD DEEP WATER

5 C

WORKING FLUID(LIKE AMMONIA)

2. CLOSED CYCLE SYSTEMOR

ANDERSON CYCLE SYSTEM

Types1. OPEN CYCLE SYSTEM

ORCLAUDE CYCLE SYSTEM

3. Hybrid cycle

OPEN CYCLE SYSTEM Open-cycle OTEC uses the tropical

oceans' warm surface water to make electricity.

Warm seawater is pumped into a flash evaporator where pressure as low as 0.03 bar cause the water to boil at temperatures of 22ºC.

This steam expands through a low-pressure turbine connected to a generator to create power.

The steam then passes through a condenser using cold seawater from the depths of the ocean to condense the steam into desalinized water.

CLOSED CYCLE SYSYTEMA low boiling point liquid such

as ammonia or another type of refrigerant is used as the working fluid in a Rankine cycle.

The heat from warm seawater flowing through an evaporator vaporizes the working fluid. The vapour expands through a turbine, then flows into a condenser where cold seawater condenses it into a liquid.

HYBRID CYCLE SYSTEMA hybrid cycle is a combination of both closed and open

cycles where flash evaporator seawater is used as the closed cycle working fluid.

This is a cycle wherein, electricity is produced in first stage followed by water production in second stage.

STRUCURAL ADVANCEMENTSuper-Heater:-In the proposed design, a black metallic plate of

aluminum is installed on the OTEC plant, above the water surface .

This plate absorbs maximum solar radiation and gets heated up to a temperature of 43ºC. This heat is transferred to the evaporated working fluid by means of connecting rods.

Pre heater:-The outlet sea water from the evaporator is 12°C warmer than the working fluid coming out of the condenser. This fact is used to preheat the working fluid before it advances into the evaporator which compensates the heat loss from the heat exchangers.

It increases the working time of the OTEC plant. This preheating increases the efficiency from 3.07 to 3.11 %- a

useful increase.

COST & EFICIENCYOTEC has the potential to offer global amounts of

energy that are 10 to 100 times greater than other ocean energy options such as wave power.

OTEC plants can operate continuously providing a base load supply for an electrical power generation system.

OTEC systems were 1 to 3 % thermally efficient, below the theoretical maximum 6 and 7 %.

Using super heater and preheater efficiency is increases.

Net energy output increases up to 20.3%.Using super heater and preheater cost increases up to

21% .

Currently operating OTEC plantsIn 2011, Makai Ocean Engineering completed a

heat exchanger test facility at NELHA.In 2013, Saga University with various Japanese

industries completed the installation of a new OTEC plant.

World’s largest Ocean Thermal Energy Conversion Power Plant in Hawaii of 100kW added to U.S. grid in this year.

ADVANTAGESi. Eco- friendly.ii. Minimal maintenance costs compared to other power

production plants.iii. Provide air conditioning to buildings within the OTEC plantiv. Fresh water - first by-product is fresh water. A small 1 MW

OTEC is capable of producing some 4,500 cubic meters of fresh water per day, enough to supply a population of 20,000 with fresh water.

v. Open cycle OTEC systems can produce desalinated water which is very important in third-world countries

vi. Chilled soil agriculture cold seawater flowing through underground pipes, chills the surrounding soil. Thereby allowing many plants evolved in temperate to be grown in subtropics due to temp. difference in the plant roots in cool soil and plant leaves in warm air.

ADVANTAGESVii. Mineral Extraction : Now a days, in mining the ocean

for trace elements would be unprofitable as so much energy is required to pump the large volume of water needed and because of the expense involved in separating the minerals from seawater.

OTEC plants already pumping the water, the only remaining economic challenge is to minimize the cost of the extraction process.

DISADVANTAGESi. OTEC-produced electricity at present would cost more than

electricity generated from fossil fuels at their current costs.ii. OTEC plants must be located where a difference of about

20º C occurs year round. Ocean depths must be available fairly close to shore-based facilities for economic operation. Floating plant ships could provide more flexibility.

iii.No energy company will put money in this project because it only had been tested in a very small scale.

iv.Construction of OTEC plants and lying of pipes in coastal waters may cause localized damage to reefs and near-shore marine ecosystems.

FUTUREThe fossil fuels will in the near future be

consumed, so we had to find some alternative energy sources. OTEC is a source, which uses the renewable solar collector, the sea, instead of an artificial collector.

The problem is that this investment will be more expensive than the fossil fuels power plants, and it will take a long time before anyone will put some money in this project and outrival the now existing plants.

CONCLUSIONOcean thermal energy conversion is a potential source of

renewable energy that creates no emissions. It is fuel free, has a low environmental impact, can supply pure water for both drinking and agriculture, can supply refrigeration and cooling and can provide a coastal community with reliable energy.

Research working on mini OTEC plants in laboratories. It may happen that OTEC systems will one day become a feasible, efficient and renewable source of energy.

REFERENCESLuis A. Vega, Economics of Ocean Thermal

Energy, American Society of Civil Engineers,1992 .

Dr. Hans Krock, Preliminary Analysis of Polymer Heat Exchangers .

Maria Bechtel and Erik Netz, OTEC .Ruperi Mario, OTEC in Pacific Island.www.google.co.in Ocean thermal energy conversion –

Wikipedia.

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