Energy from oceans

MAHIDA HIRENKUMAR RANJITSINH

Mechanical Engineering Department

[email protected]

68.18% of the Earth is covered by the Oceans (361 million square kilometers) So they represent a rather large storage reservoir of the solar input.

These Oceans are constantly being heated by the sun.

Solar energy absorbed by oceans is = (4000 x humanity annual consumption)

Less than 1 % of this energy would satisfy all needs.

Estimated that if 0.1% of the renewable energy available from within the ocean was converted into electrical energy, it would satisfy the present world demand more than 5 times over.

Ocean Thermal energy Conversion (OTEC)

Tidal Energy

Wave Energy

Hydrological Cycle. (Evaporation by Solar Heating)

First attempt in 1880’s

Jacques D’Arsonval proposed the idea of converting differences in water temperature in to electric energy.

George Cloud installed first OTEC plant in 1930 in Cuba.

It had generated 22kw of electricity with low pressure steam turbine, however it did not produce a net power.

Thermodynamic Principle of “PRIME MOVER”.

It does not require any type of minerals/ materials to produce energy.

Surface (Warm) seawater is flash evaporated in a vacuum chamber resulting low-pressure steam drives turbine-generator.

Cold seawater condenses steam after it has passed through the turbine & produces fresh water.

Because of the need in the open cycle to harness the energy in low pressure steam, extremely large turbine are required.

More deareators must be used to remove the gases dissolved in the sea water unless one is willing to accept large losses in efficiency

Warm (surface) seawater and Cold(deep) seawater used to vaporize and condense a working fluid , such as ammonia ,freon or propen which drives a turbine-generator in a closed loop producing kWh.

It requires very large size Heat Exchangers.

The operating pressure is much higher than of the water, being roughly 10 bar at the boiler, and their specific volumes are much lower, being comparable to those of steam in conventional plants.

Hence much smaller and less costly turbines are required.

The temperature difference in the boiler and condenser must be kept as low as possible to allow for maximum possible temperature difference across the turbine, which also contributes to the large surfaces of these units.

Plate type heat exchanger instead of shell and tube type.

Due to formulation of bio fouling, corrosion referred to a fouling and will tend to inhibit heat transfer through it.

This cycle is an attempt to combine the best features and avoid the worst features of the open and closed cycles.

Sea water is first flash evaporated to steam, as in open cycle and heat in the resulting steam is then transferred to ammonia as in the conventional closed cycle.

Closed cycle to be most economical in cost and to require least power.

Closed cycle is favoured for the future development in expectation of higher efficiency but does not yet have the advantage of having been put in practice.

Due to the lack of experience that puts ocean thermal difference development at a disadvantage and leads to emphasis on wind power.

Japan plans to lead the way in actual development like materials, fouling problems and design.

The sources of temperature difference for this system are endless.

The ocean currents are not going to stop any time soon.

Works 100% coal and oil free.

Only makes sense to implement.

Must use a liquid with a low boiling temperature

Propane (under the right pressure)

Uses the warm surface water heated by the Sun to boil the propane

Colder denser water at the bottom of the basin to condense the propane

OTEC project cell established at IIT, Madras and has completed the feasibility study for establishments of a 1 MW OTEC plant in Lakshdeep Island.

Preliminary Oceanographic studies of both the island have seen large lagoons on the western side.

A hydrographic survey of the proposed site was undertaken by National Hydrographic Office, Dehradun. The preliminary assessment of survey indicates the availability of suitable conditions for establishment of OTEC plant.

Tide is a periodic rise and fall of the water level of sea which are carried by the action of the sun and moon on the water of the earth.

It has been estimated that about a billion KW of tidal power is dissipated by friction and eddies alone. This is slightly less than the economically exploitable power potential of all the rivers of the world.

First attempt in the 11th century in Great Britain and later in France and Spain.

The main feature of the tidal cycle is the difference in the elevations at the high tide and low tide.

During the power generation process the power is generated at both the times i.e. high tide and low tide.

The first tidal power plant was commissioned by General De Gaulle at La Rance in 1966.

The average tidal range is 8.4 m and the maximum is 13-5 m. Effective basin area 22

Square km and basin volume 184000000 m3.

It has used single basin and submerged reversible propeller type turbine generators that could generate power with the water flowing in either direction through the Bulb turbine runner.

Installed capacity is 240 MW.

Maximum utilization of stored hydraulic potential energy is 18%, which may be increased to 24% in future by addition of 80 MW more generating capacity.

Presently 2 power plants are operating in the world . (France & USSR)

The Proxigean Spring

Tide is a rare, unusually

high tide.

•This very high tide occurs

when the moon is both

unusually close

to the Earth (at its closest

perigee, called the

proxigee) and in the

New Moon phase (when the

Moon is between the Sun

and the Earth).

•The proxigean spring tide

occurs at most once every

1.5 years.

•Neap tides are especially weak tides.

They occur when the gravitational forces

of the Moon and the Sun are perpendicular

to one another (with respect to the Earth).

Neap tides occur during quarter moons.

Tides are produced mainly by the gravitational acceleration of the moon and the sun on the water of solid earth and the oceans.

70% of the tide producing force is due to the moon and 30% to the sun.

The power house

The dam or Barrage to form pool or Basin.

Sluice ways from the basins to the sea and vice versa.

Turbines:

The Bulb Group turbines.

Rim Type Turbines.

The power generation from tides involves flow between an artificially developed basin and the sea.

However in order to have more or less continuous generation, this basin scheme can be elaborated by having two or more basins.

Following type of arrangements are possible.

(1) Single Basin Arrangement.

(2) Double Basin Arrangement.

Generate power only intermittently.

The generation of power can be achieved in a single basin arrangement either as a

(1) Single Ebb(flow back of tide) Cycle system.

(2) Single Tide Cycle system

(3) Double cycle system.

Thank You