WAVE ENERGY POWER PLANT
Installation along Indian East Coast

OE 430

OCEAN ENERGY

Prof. SANNASIRAJ

Team Members:

RITURAJ (NA06B019)

VIKAS VERMA (NA06B031)

RAVI KIRAN (NA06B018)

PRITHI PRASAD (NA06B017)

ROHIT DILIP (NA06B020)

TABLE OF CONTENTS

• Overview

• Indian Scenario

• Location Information

• Technology

• Advantages and Disadvantages

• Turbine selection

• Device layout

• Conclusion

• References

Overview of Wave Energy

A wave is a disturbance that propagates through space and time, usually with transference of energy. Waves travel and transfer energy from one point to another, often with little or no permanent displacement of the particles of the medium (that is, with little or no associated mass transport); instead there are oscillations around almost fixed locations. Wave power refers to the energy of ocean surface waves and the capture of that energy to do useful work — including electricity generation, desalination, and the pumping of water (into reservoirs). Wave power is a form of renewable energy. Though often co-mingled, wave power is distinct from tidal power and the steady gyre of ocean currents.

Since the late 1990s a number of small companies have tried to develop and commercialise a range of different wave energy technologies as a non-polluting source of energy, which has resulted in a number of full-size devices being deployed in the sea. In some countries, these initiatives have been accompanied by government-funded activities, as well as developments in international organisations such as the European Commission and the International Energy Agency. Wave energy can be considered as a concentrated form of solar energy, where winds generated by the differential heating of the earth pass over open bodies of water, transferring some of their energy to form waves. The amount of energy transferred and hence the size of the resulting waves depends on the wind speed, the length of time for which the wind blows and the distance over which it blows, i.e. Fetch. In this way, the original solar power levels of typically ~ 100 W/m2 can be transformed into waves with power levels of over 1 000 kW per metre of wave crest length. Waves lying within or close to the areas where they are generated (storm waves) produce a complex, irregular sea. These waves will continue to travel in the direction of their formation even after the wind dies down. In deep water, waves lose energy only slowly, so they can travel out of the storm areas with minimal loss of energy as regular, smooth waves or 'swell' and this can persist at great distances from the point of origin. Therefore, coasts with exposure to the prevailing wind direction and long fetches tend to have the most energetic wave climates, such as the western coasts of the Americas, Europe, Southern Africa and Australia.

Wave Power Plant consisting of following parts; main steel construction, sensor tanks fixed to main steel construction by means of joints, pumps, and mineral oil, hoses, non-return valves, throttle valves, pressure control valves, pressure regulators, potential hydraulic energy accumulators, hydro motor, alternator, voltage regulator, control panel, conductors. The wave energy plant costs are limited to its initial investment's amortization and maintenance costs. As there is no polluting agent in this plant, it is totally environmental, clear and unlimited energy.

Indian Scenario

Presently, the wave energy technology is not much efficient in India. The major sites include:

Vizinjham Power Plant:

The Indian Wave Energy Program started in 1983 at the Indian Institute of Technology, Madras. Early research led to the conclusion that the Oscillating Water Column (OWC) type of device was most suitable for Indian conditions and a 150 kW pilot plant was actually built and commissioned in October 1991 in the breakwater of the Vizinjham Fisheries Harbour near Trivandrum in Kerala.

In 1993 the National Institute of Ocean Technology was established within the IIT-M campus and it took over the wave energy program. NIOT continues research on wave energy as part of its overall mandate to exploit India's ocean resources. While an improved model was again installed at Vizinjham in April 1996, we don’t see details of much progress beyond that.

Location Information:

[pic]

Proposed Location Features:

• Location : 16*N ,80*E , Nizamapatnam , Andhra Pradesh , India, East Coast of India, Bay of Bengal

• Depth at which the Device is placed : 16m

• Distance from the shore : 100m(assuming sea bed slope of 1:6)

• Maximum Power Potential at this region = 10.9 KW/m

Wind & Wave features :

Wind Speed: 7m/s

High waves:

• Time period: 5 seconds

• Wavelength: 10.5m

• Celerity: 2.1m/s

• Wave height:2m

Low waves:

• Time period: 7.5 seconds

• Wavelength: 12m

• Celerity: 1.6m/s

• Wave Height:1.4m

POWER ESTIMATION:

Power estimation of the wave = γ H2C/8

Where, γ = ρ*g = 1.025(tonnes/m3) * 9.81(m/s2) = 10.055 tonnes / m2s2

High waves: Low waves:

H = wave height = 2m H = wave height = 1.4m

C = wave celerity = 2.1 m/s C = wave celerity = 1.6 m/s

PW = 10.60 KW/m PW = 3.9 KW/m

Technology used in Wave Energy Device :

The major techniques used for exploiting the energy of waves include:

a) Float or Pitching Device or Buoyant Moored Device

b) Oscillating Water Columns (OWC)

c) Hinged Contour Device

a) Float/Pitching/Buoyant Moored Device:

The device floats on or just below the surface of the water and is moored to the sea floor. A wave power machine needs to resist the motion of the waves in order to generate power: part of the machine needs to move while another part remains still. In this type of device, the mooring is static and is arranged in such a way that the waves motion will move only one part of the machine. Electricity is generated from the bobbing or pitching action of a floating object which can be mounted to a floating raft or to a device fixed on the ocean floor.

b) Oscillating Water Column:

An oscillating water column is a partially submerged, hollow structure that is installed in the ocean. It is open to the sea below the water line, enclosing a column of air on top of a column of water. Waves cause the water column to rise and fall, which in turn compresses and depresses the air column. This trapped air is allowed to flow to and from the atmosphere via a Wells turbine, which has the ability to rotate in the same direction regardless of the direction of the airflow. The rotation of the turbine is used to generate electricity.

c) Hinged Device:

Here, the resistance to the waves is created by the alternate motion of the waves, which raises and lowers different sections of the machine relative to each other, pushing hydraulic fluid through hydraulic pumps to generate electricity. A hinged contour device is able to operate at greater depths than the buoyant moored device. These shoreline devices, also called "tapered channel" systems, rely on a shore-mounted structure to channel and concentrate the waves, driving them into an elevated reservoir. Water flow out of this reservoir is used to generate electricity, using standard hydropower technologies.

Turbine Selection:

We have used Oscillating Water Column method for harnessing energy from the waves. In India, a lot of research work has been performed and this technique has been comprehended to a great extent. The advantage of using this technique is that a lot of data is available corresponding to different wave conditions. In this analysis, we have used the data from the research work involved in setting up of Vizingham wave power plant and Indian near shore OWC plant (Circa).

The OWC is a linear device (with respect to wave height) but with frequency dependent characteristics. The linked guide vane (LGV) impulse turbine has a non-linear pressure / flow characteristic. As the turbine serves as a damping for the caisson, the overall plant efficiency would not be necessarily be the turbine configuration with the highest efficiency. The problem is thus to choose a configuration that maximizes the overall energy capture from wave to wire. In this work we initially predict the efficiency of the OWC based on model studies of the caisson. The turbine generator is then modelled. Model studies and practical measurements have shown the efficiency of an OWC to be greater than 90% at an optimum damping and when designed to match the incident excitation frequency. At higher power levels, the efficiency of an electrical generator can also be in excess of 90% over a wide range of inputs. Thus, the component with the lowest efficiency spanning the input range is the turbine.

They are of three conceptual classes –

1. Bidirectional turbines with stalling behaviour 2. Bidirectional turbines without stalling 3. Unidirectional turbines

The performance of OWC largely depends on the variability of the waves in that region. The variation is observed both on a seasonal and daily basis. For example, in India, the incident wave power can be as high as 30 KW/m during the monsoons and reduce to about 4 KW/m during December. Hence in order to make the plant functional throughout the year, we have to implement technology which can exploit either kind of waves.

Based on the various data collected and the recent developments in the technology of turbines, we have used unidirectional fixed vane turbine. The salient features of the turbines are:

• It offers wide range of speeds of operation, so the problem of stalling is avoided to an extent. • It has higher efficiency than the bidirectional guided turbines (Well’s) for both low and high pneumatic power. • It has high instantaneous efficiency over a large range. • The presence of fixed vanes ensures less stress over the turbine compared to linked vanes • Simple technology ensures more effectiveness.

The only disadvantage is the presence of valves which open and close to frequently because the time period of waves is in seconds, thus hindering the durability of the equipment. The cross section of the turbine is as follows:

[pic]

Calculation of efficiency

Efficiency:

The efficiency of an OWC based plant is given by η=ηOWC x ηt x ηe

where,

ηOWC is the efficiency of the OWC

ηt is the turbine efficiency

ηe is the electrical generator efficiency

OWC efficiency is related to the capture factor. The capture factor is the ratio of pneumatic power to the incident wave power. The value of capture factor for a particular turbine corresponding to given wave power is directly read from the following graph:

[pic]

Case 1. HIGH WAVES

Considering the average wave height = 2m

Time period = 5 seconds

Span of collection of incident waves = 30(front) +60(sideways)

= 90m

Incident wave energy = 10.6KW/m

Incident wave energy on front face =(10.6 x 20) =212 KW

Assuming reflection coefficient as 0.6,

Wave energy potential of reflected waves = 10.6X (0.6)2

= 3.816KW/m

Total incident wave energy =2 12 + (3.186 X 40)

= 339.4KW

(Here we have neglected the effect of head on waves on the pistons placed sideways)

From the graph Capture Factor for 2m unidirectional FGV at 339.4 KW = 0.815

Hence,

ηOWC = 0.815

Pneumatic Power = 0.815 x 339.4

= 276.6 KW

Turbine efficiency is defined as the ratio of output power of the turbine to the available pneumatic power. This value is also obtained from the following graph for different kinds of turbines:

[pic]

Output Turbine Power of 2m FGV Turbine for Pneumatic Power of 276.6 KW= 162KW

Hence, ηt = 162/276.6

= 0.58

Assuming ηe =0.8 (taking into account all the power losses),

Net output power = 0.8 X 162 KW

= 129.6 KW

Based on this calculation we select a generator in the output range 100-150 KW.

Power Distribution:

[pic]

For the 2m unidirectional turbine, we have wire efficiency of 0.48

Hence, power transferred to grid = 0.48 X 129.6KW

= 62.2KW

Generator chosen:

Perkins Generator 80KW~140KW

Engine Model no: 1006TG1A

Net efficiency:

Generation Efficiency:

η=ηOWC x ηt x ηe

= 0.815 X 0.58 X 0.8

= 0.3786 Wire efficiency (ηwire )= 0.4

The capacity of the plant in high amplitude wave condition is 129.6KW and it transmits 51.6 KW

Case 2. LOW WAVES

Low wave conditions:

The average low wave height in the region = 1.4m

Time period = 7.5 seconds

Span of collection of incident waves = 30(front) +60(sideways)

= 90m

Incident wave energy = 3.9KW/m

Incident wave energy on front face = (3.9 x 20) =78 KW

Assuming reflection coefficient as 0.6,

Wave energy potential of reflected waves = 3.9 X (0.6)2

= 1.41KW/m

Total incident wave energy =78 + (1.41 X 40)

= 134 KW

From the graph Capture Factor for 2m unidirectional FGV at 134 KW = 0.82

Available Pneumatic Power = 0.82 X 134

=109.8KW

Output turbine power of 2m FGV turbine for pneumatic power of 109.8 KW = 68KW

Hence, ηt =68/109.8

=0.61

Assuming ηe =0.8 (taking into account all the power losses),

Net output power =0.8 X 68 KW

=54.4 KW

Based on this calculation we select a generator in the output range 40-80 KW.

Generation Efficiency:

η = ηOWC x ηt x ηe

= 0.82 X 0.61 X 0.8

= 0.400

Wire Efficiency:

Wire efficiency (ηwire ) = 0.48

Power transmitted =26.112 KW

The capacity of the plant in low amplitude wave condition is 54.4KW and it transmits 26.112 KW

Generator Used:

Guardian Elite 70

Type : Commercial

Model No : QT070,QT07068

Wattage Rating : 70kW - Natural gas, 70 kW - Liquid propane

Fuel : Natural Gas, Liquid Propane

Sound Rating : 71 dB at 23 feet with full load

Lowest Price Found : $ 14,500.00

Power Output : 70 KW

Device Layout

The top view of the device is as given below:

[pic]

The dimension of air column piston is shown below:

The whole energy operation is divided into two stages:

1. Intake stroke 2. Exhaust stroke

1. Intake stroke: The air comes in and drives the turbine and then leaves through the valves. The piston is under the effect of troughs.

[pic]

Diaphragm

2. Exhaust stroke: The piston is under the effect of crests and diaphragm gets compressed. The air enters the chamber, drives the turbine and then leaves through the valves.

[pic]

Diaphragm

Salient Features:

• The floating power plant system is designed for offshore. Since the power in the offshore waves is greater than low depth onshore waves, it can deliver considerable greater energy. • The system can install anywhere there is sufficient waves are present because of it is independent of the nature of the site. • It probably will not case any impact on the nature. • The system can be constructed in an onshore factory and easily be transport to the ideal sites by a simple pulling boat. • Whole of the metallic- corrosive parts of the system like turbine, pistons etc. are completely separated from the direct contact of the sea water. • Any tidal rising of water or any other means of rising of the sea level will affect the system because of it just floats on the sea surface. • The platform is moored to the sea bed and has ballast compartments so as to vary its draft depending on the wave height situations.

Difficulties:

• Violent cyclonic wind and there by the giant waves may cause stability problems.

• Perfect anchoring of the system

• Depth of the sea.

CONCLUSION:

Wave energy is an immature technology and therefore there are only few prototype devices installed worldwide, some of which indicate quite high probability of fabricating such plants at suitable places all over the world in coming years.

There are a number of ideas and designs for wave energy devices, many of which will be uneconomic and some of which will not work reliably. Care should be taken to identify at an early stage those devices which have poor prospects, in order to make the least use of the limited funds that can be expected for the development of wave energy. There are a few technologies that are ready to be deployed and which show considerable promise. These devices will require some support in order to realize their full potential and, several governments are providing this. If this situation continues, then within 5 to 10 years' time, wave energy could start to make a significant contribution to energy supply and the provision of potable water.

In India, by analyzing the information collected from various sources and the journals published by various established authors, we have concluded that, Nizamapatnam (Andhra Pradesh) is the best suitable sight for erecting such a device. The wave energy plant envisages an environment friendly approach with no pollution. To summarize, the calculated efficiency of the wave power plant at the proposed site is 37.86% for high waves and 40% for low waves.

|Condition |Energy produced |Efficiency (%) |
|High wave |51.6 KW |37.86 |
|Low wave |26.112 KW |40 |

References

• http://www.engin.umich.edu/dept/name/research/projects/wave_device • http://www.sciencedirect.com/science • http://indicview.blogspot.com/2007/04/small-wave-power-plant-in-maharashtra.html • http://www.worldenergy.org/