OCEAN ENERGY CONVERSION methods

Guided By:prof. JESNA MOHAMMED

Arshad babu. U M7B Roll No: 7457 TKMCE kollam

INTRODUCTION

What is Ocean Thermal Energy Conversion?

The oceans cover a little more than 70 percent of the Earth's surface. This makes them the world's largest solar energy collector and energy storage system.

On an average day, 60 million square kilometers (23 million square miles) of tropical seas absorb an amount of solar radiation equal in heat content to about 250 billion barrels of oil.

If less than one-tenth of one percent of this stored solar energy could be converted into electric power, it would supply more than 20 times the total amount of electricity consumed in the United States on any given

Achievements in OEC

1881-Arsonval,a French scientist first to propose tapping the thermal energy of the ocean

1881-Georges Claude built an experimental open cycle OTEC system System produced 22 kw electricity 1956-French researchers designed a 3 megawatt open OTEC unit at

Africa's west coast .It was too expensive and they quit the project 1979-The first 50 kw closed cycle OTEC demonstration plant went up

at Nelha known as “MINI OTEC” 1980-US Department of energy built “OTEC-1”

1981- japan demonstrated a shore based,100kw closed cycle plant Freon was the working fluid and Titanium shell and tube exchanger was used

1984-Solar energy research institute developed a vertical evaporator to convert warm sea water into low pressure steam for open cycle plants

March 2013-Saga University with various Japanese industries completed the installation of a new OTEC plantOkinawa Prefecture announced the start of the OTEC operation testing at Kume Island on April 15, 2013.

WORKING PRINCIPLE

Oceans layers of water have different temperatures to drive a power producing cycle.As long as the temperature between the warm surface water and the cold deep water differs by 20degree.Cel,an OTEC system can produce significant amount of power.

ELECTRICITY PRODUCTION CLOSED CYCLE OTEC SYSTEMS OPEN CYCLE OTEC SYSTEM HYBRID OTEC SYSTEM

WORKING PRINCIPLE

Oceans layers of water have different temperatures to drive a power producing cycle.As long as the temperature between the warm surface water and the cold deep water differs by 20degree.Cel,an OTEC system can produce significant amount of power.

ELECTRICITY PRODUCTION CLOSED CYCLE OTEC SYSTEMS OPEN CYCLE OTEC SYSTEM HYBRID OTEC SYSTEM

OPEN CYCLE OTEC SYSYTEM This system relies on a low-pressure environment to actually boil the ocean water and create steam. When warm ocean water moves into a low-pressure environment it will boil. The steam is almost pure water as the salts and other impurities are left behind. The steam then recirculates and condenses back to water. The warm sea water is flash evaporated in vacuum chamber at an absolute pressure of 2.4 kilopascals. Steam expands over a low pressure turbine and the generator produces the electricity

OPEN CYCLE OTEC

The open cycle plant needs very large size turbine because of large volume of steam at low pressure approximately at .002 bar. The average pump work is required in open cycle a the plant has to handle very large quantity of warm and cold water because of low water temperature difference

CLOSED CYCLE OTEC

Warm sea water vaporizes a working fluid, such as ammonia, flowing through a heat exchanger. The vapor expands at moderate pressures and turns a turbine coupled to a generator that produces electricity. The vapor is then condensed in another heat exchanger using cold sea water pumped from the oceans depths through a cold water pipe. The condensed working fluid is pumped back to the evaporator to repeat the cycle. The working fluid remains in a closed system and circulates continuously

CLOSED CYCLE OTEC

Advantages of Closed cycle OTEC

The size of the plant is lowered in closed cycle compared with open cycle because of high running pressure 9-16 bar.

Cost of energy generation is reduced in closed cycle.

Higher efficiency.

Corrosion on turbine and other parts is avoided.

As the secondary fluid boils at temperature available in hot water and doesn’t require vacuum pump.

Fabrication of steam turbine is easier than a large turbine used in open cycle.

HYBRID CYCLE OTEC

A hybrid cycle combines the features of both the closed-cycle and open-cycle systems. In a hybrid OTEC system, warm seawater enters a vacuum chamber where it is flash-evaporated into steam, which is similar to the open-cycle evaporation process. The steam vaporizes the working fluid of a closed-cycle loop on the other side of an ammonia vaporizer. The vaporized fluid then drives a turbine that produces electricity. The steam condenses within the heat exchanger and provides desalinated water

HYBRID OTEC SYSTEM

ADAVANTAGES

It is environmentally friendly. It can provide useful environment in areas bordering

on tropical seas. It can produce electricity without giving off any CO2,

and do it for a long period. The additional products i.e., food, potable water; air

conditioning; etc. which can readily be provided. Potable water production alone can reduce electrical

generating costs by up to one third, and is itself in very considerable demand in most areas where OTEC can operate.

The cold seawater is rich in nutrients and can be utilized for water plants or for aquaculture used to increase the production.

The thermal resource of the ocean ensures that the power source is available day or night, and with only modest variation from summer to winter.

DISADVANTAGES

The power cost is more.

The construction and pipe length affects the marine ecosystem.

The closed cycle OTEC can cause the pollution, if intermediate chemicals leak into the ocean.

Heat exchangers (Evaporator & Condenser) must be made of highly conductive materials, which increase their capital cost.

APPLICATIONS OF OTEC SYSTEM

A closed cycle OTEC plant can also act as chemical treatment plant.

The enclosing area can be used for aquaculture and maricultue.

The deep sea coldwater is rich in nutrient and can be used for various applications.

Desalinated water, which can be used for irrigation and human consumption

ENVIRONMENTAL IMPACT

The marine environment gets affected by these plants through water heating.

The release of toxic chemical and entrapment of small sea organism in intake pipes is common.

Thermal layer of seawater near the plants get disturbed because of the discharge of low and high water at intermediate level.

The marine life gets affected because of change in pH and dissolved Oxygen.

TIDAL ENERGYThe periodic rise and fall of water level of sea which are carried by the action of the sun and moon on water of the earth is called “tide”. The large scale up and down movement of sea water represents an unlimited source of energy.

The main feature of the tidal cycle is the difference in water surface elevations at the high tide and at the low tide. If the differential head could be utilized in operating a hydraulic turbine, the tidal energy could be converted into electrical energy by means of an attached generator.

A Tidal power plant mainly consists of the following:1. A barrage with gates and sluices2. One or more basins3. A power house

A barrage is a barrier constructed across the sea to create a basin for storing water. The barrage has to withstand the pressure exerted by the water head and also should resist the shock of the waves.

A basin is the area where water is retained by the barrage. Low head reversible water turbine are installed in the barrage separating the sea from the basin.-

ADVANTAGES  It is inexhaustible source of energy No problem of pollution The cost of power generation is quite low High output can be obtained compared to solar or wind energy 

DISADVANTAGES  Capital cost is very high As the head is not constant, variable output is obtained As the head is low, large amount of water is necessary for the

turbine It will not operate when the available head is less than 0.5m 

WAVE ENERGY

Wave power refers to the capture of (ocean) wave energy to do useful work including electricity generation, desalination, and filling a reservoir with water

Wave Power is renewable energy and is a form of solar energy transferred to water by the wind

Upto 2 terawatts (1 terawatt = 1 trillion watts) Initial solar power level of 100 W/m2 is concentrated to an

average wave power level of 70 kW per meter of crest length

This rises to 170 kW per meter of crest length during winter and to more than 1MW per meter during storms.

Carry energy in the form of potential energy which is characterized by height and wave length which define energy parameters Energy extracted from the Ocean waves is called Wave Energy in the form of, – Potential Energy (pressure fluctuations below free surface) Kinetic Energy (energy from free surface)

OSCILLATING WATER COLUMNThese devices generate electricity from the wave driven rise and falloff water in cylindricalshaft.The rising and falling water column drives air into and out of the top of the shaft, powering an air driven turbine

FLOATS OR PITCHING DEVICESThese devices produces electricity from the bobbing or pitching of a floating object. The object can be mounted to a floating raft or to a device fixed on the ocean floor

FOCUSING DEVICES

These shoreline devices also called tapered channel systems, rely on a shore mounted structure to channel and concentrate waves, driving them into an elevated reservoir.

OSCILLATING WATER COLUMN

TAPERED CHANNEL WAVE POWER

ENVIRONMENTAL EFFECTS

Over head power lines are required to transport the power We can alter ocean surface currents Effects some of the marine organisms Effects on shipping and navigation For this reason ,warning lights and clearly marked channels

to ensure the safe navigation around converters are essential

OTEC New developments

COMPARATIVE TABLE OF DIFFERENT SEA ENERGY RESOURCES

REFFERENCES

NON-CONVENTIONAL ENERGY RESOURCES by S.K.DUBEY

Engineeringpapers.blogspot.com

www.matlabcodes.com Electrical Power Research Institute, Ocean Energy pro- gram,

Assessment reports, 2004 – 2006 (http://oceanenergy.epri.com/)

Thank you