Renewable sources of Energy

Renewable sources of Energy


NOTE:-Now-a-days pollution is a most dangerous problem in all our world.They affect our climate,health and envionment also. and if they increase at the same speed, our beautiful earth can be destroyed. 
so, its my pledge request to all of  you who read this blog.please use as much amount of renewable energy as you can instead of fossil fuel as i discussed below. and plant solar system in your homes and use so they can reduce the use of coal or other fossil fuel in power stations And save our earth and those people lifes which who have love you most.That's the reason to post this blog.I do our best to give entire information about renewable energy sources in this post.Thank you!



Now we start! 
Renewable sources of energy or non-conventional sources are those sources which are finds in nature means,which are endless or renewable.for example:-

1. Solar energy(sun light)
2. Bio-energy
3. Wind energy
4. Geo-thermal energy(energy which is place in earth crest in the form of heat)
5. Tidal energy
6. wave energy

Today we discuss about all the energies mentioned above.
As we all know, Now-a-days most of the power is generated by coal or other fossils fuels in power stations(almost 80% power generated by coal) which is very harmful to our environment and humankind.
That's why now-a-days all focus goes to renewable sources of energy which are pollution free and safe for environment.


Solar energy
solar energy is a radiation of sun light, when sun light falls on the photo-volataic cell or solar cell a power is generated that is called solar energy.

Photo-volataic cell or solar cell

solar cell is a device which converts sun light radiations or energy of light into electricity.The PV(photo-voltaic) effect was discovered in 1954, when scientists at Bell Telephone discovered that silicon (an element found in sand) created an electric charge when exposed to sunlight. Soon solar cells were being used to power space satellites and smaller items like calculators and watches.




Material used to make solar cell

Silicon 

Silicon is, by far, the most common material used in solar cells, representing approximately 90% of the modules sold today. It is also the second most abundant material on Earth (after oxygen) and the most common semiconductor used in computer chips. Crystalline silicon cells are made of silicon atoms connected to one another to form a crystal lattice. This lattice provides an organized structure that makes conversion of light into electricity more efficient.

Solar cells made out of silicon currently provide a combination of high efficiency, low cost, and long lifetime. Modules are expected to last for 25 years or more, still producing more than 80% of their original power after this time.

Principle of solar cell

Solar cells can be arranged into large groupings called arrays. These arrays, composed of many thousands of individual cells, can function as central electric power stations, converting sunlight into electrical energy for distribution to industrial, commercial, and residential users. Solar cells in much smaller configurations, commonly referred to as solar cell panels or simply solar panels, have been installed by homeowners on their rooftops to replace or augment their conventional electric supply. Solar cell panels also are used to provide electric power in many remote terrestrial locations where conventional electric power sources are either unavailable or prohibitively expensive to install. Because they have no moving parts that could need maintenance or fuels that would require replenishment, solar cells provide power for most space installations, from communications and weather satellites to space stations. (Solar power is insufficient for space probes sent to the outer planets of the solar system or into interstellar space, however, because of the diffusion of radiant energy with distance from the Sun.) Solar cells have also been used in consumer products, such as electronic toys, handheld calculators, and portable radios. Solar cells used in devices of this kind may utilize artificial light (e.g., from incandescent and fluorescent lamps) as well as sunlight.

Working

A solar cell is a sandwich of n-type silicon and p-type silicon . It generates electricity by using sunlight to make electrons hop across the junction between the different flavors of silicon:

1. When sunlight shines on the cell, photons (light particles) bombard the upper surface.
2. The photons (yellow blobs) carry their energy down through the cell.
3. The photons give up their energy to electrons (green blobs) in the lower, p-type layer.
4. The electrons use this energy to jump across the barrier into the upper, n-type layer and escape out into the circuit.
5. Flowing around the circuit, the electrons make the lamp light up

Application of solar energy

Concentrating Solar Power (CSP): Concentrating solar power (CSP) plants are utility-scale generators that produce electricity using mirrors or lenses to efficiently concentrate the sun’s energy. The four principal CSP technologies are parabolic troughs, dish-Stirling engine systems, central receivers, and concentrating photovoltaic systems (CPV). 

Solar Thermal Electric Power Plants: Solar thermal energy involves harnessing solar power for practical applications from solar heating to electrical power generation. Solar thermal collectors, such as solar hot water panels, are commonly used to generate solar hot water for domestic and light industrial applications. This energy system is also used in architecture and building design to control heating and ventilation in both active solar and passive solar designs.

Solar Heating Systems: Solar hot water systems use sunlight to heat water. The systems are composed of solar thermal collectors and a storage tank, and they may be active, passive or batch systems.

Solar Lighting: Also known as daylighting, this is the use of natural light to provide illumination to offset energy use in electric lighting systems and reduce the cooling load on HVAC systems. Daylighting features include building orientation, window orientation, exterior shading, saw tooth roofs, clerestory windows, light shelves, skylights, and light tubes. Architectural trends increasingly recognize daylighting as a cornerstone of sustainable design.

Solar Cars: A solar car is an electric vehicle powered by energy obtained from solar panels on the surface of the car which convert the sun’s energy directly into electrical energy. Solar cars are not currently a practical form of transportation. Although they can operate for limited distances without sun, the solar cells are generally very fragile. Development teams have focused their efforts on optimizing the efficiency of the vehicle, but many have only enough room for one or two people.

Solar Power Satellite: A solar power satellite (SPS) is a proposed satellite built in high Earth orbit that uses microwave power transmission to beam solar power to a very large antenna on Earth where it can be used in place of conventional power sources. The advantage of placing the solar collectors in space is the unobstructed view of the sun, unaffected by the day/night cycle, weather, or seasons. However, the costs of construction are very high, and SPSs will not be able to compete with conventional sources unless low launch costs can be achieved or unless a space-based manufacturing industry develops and they can be built in orbit from off-earth materials.

Solar Updraft Tower: A solar updraft tower is a proposed type of renewable-energy power plant. Air is heated in a very large circular greenhouse-like structure, and the resulting convection causes the air to rise and escape through a tall tower. The moving air drives turbines, which produce electricity. There are no solar updraft towers in operation at present. A research prototype operated in Spain in the 1980s, and EnviroMission is proposing to construct a full-scale power station using this technology in Australia. 

Renewable Solar Power Systems with Regenerative Fuel Cell Systems: NASA has long recognized the unique advantages of regenerative fuel cell (RFC) systems to provide energy storage for solar power systems in space. RFC systems are uniquely qualified to provide the necessary energy storage for solar surface power systems on the moon or Mars during long periods of darkness, i.e. during the 14-day lunar night or the12-hour Martian night. The nature of the RFC and its inherent design flexibility enables it to effectively meet the requirements of space missions. And in the course of implementing the NASA RFC Program, researchers recognized that there are numerous applications in government, industry, transportation, and the military for RFC systems as well.

BIO-ENERGY

Bioenergy is the energy which is stored in biological matter or “biomass”.

This can be anything from plants to straw to slurry to food waste and even sewage.

How does biomass generate energy?

This depends on the type of biomass being used.

Dry, combustible feedstocks are burnt in boilers or furnaces, while wet feedstocks are put into sealed tanks, where they create biomethane gas as they rot.

This gas is captured throughout the rotting process and is then burnt.

Burning the biomass or biomethane produces heat which can be used to warm homes, shops and offices, or it can be used to drive steam turbines to generate electricity much in the same way as coal or gas fired power plants.

Bioenergy is a very flexible source of energy (it can be stored, and then turned up and down quickly to meet demand) which makes it a great backup for other renewable technologies, like wind turbines and solar panels, which depend on the weather to generate electricity.

Two main process to produce bio-gas 

•  Anaerobic digestion is a series of biological processes in which microorganisms break down biodegradable material in the absence of oxygen. One of the end products is biogas, which is combusted to generate electricity and heat, or can be processed into renewable natural gas and transportation fuels.Biogas plants may be single-farm units or centralized plants. In a centralized plant, animal manure from a number of farms and organic waste from food processing and other industries are transported to a plant. Energy crops (e.g. corn silage) may also be used as feedstock. At the plant, the biomass is treated in an anaerobic process, which generates biogas. The biogas may be used as fuel in an engine, which produces electricity and heat, or as fuel for vehicles. The digested biomass may be used as fertiliser in crop production. The biomass is received and stored in pre-storage tanks. Danish plants use continuous digestion in fully agitated digesters. This implies removing a quantity of digested biomass from the digesters and replacing it with a corresponding quantity of fresh biomass, typically several times a day. The digesters are heated to either 35 - 40 o C (mesophilic digestion) or 50 - 55 o C (thermophilic digestion)

• Biogas fermentation is a series of processes where microorganisms break down biodegradable materials (usually in the absence of oxygen), thus it is often attributed as anaerobic digestion. The break-down of these biodegradable materials (such as biomass) will produce simpler molecules, where some of these products are in the form of bio-gas. The detailed mechanism of how biogas fermentation occurs depends on the microorganisms involved, as well as types of feedstock (biomass) used and operating conditions (temperature, pH, etc). In general, we can describe the mechanism into four key biological and chemical stages: hydrolysis, acidogenesis, acetogenesis, methanogenesis, which is described in Fig. 1. (click to enlarge figure)
  
  Fig.1. Biological and chemical stages of biogas fermentation processes. The exact chemical species produced at each stage depend considerably upon the kinds of microorganisms used as well as processing conditions.
  
  
  As shown in Fig. 1, polymeric form of organics such as carbohydrate, protein, lipid, cellulose are degraded into their constitutive monomers by many kinds of microorganisms. The monomers are then converted mainly into organic acids (such as butyric acid, propionic acid) by the action of acid producing microorganisms. Next step is the conversion of these organic acids into acetic acids as well as hydrogen. Finally, methane can be recovered by the methane-producing bacteria. Since some of the hydrogen produced cannot be converted, the final product of biogas usually contains methane (CH₄) and hydrogen (H₂). These methane and H₂ (which are the main constituents of biogas), after desulphurization and deodorization, can later be used in the combustion system or fed to the fuel cell system to generate electricity. This is how we obtain energy from the biogas fermentation method.

  Wind energy

Wind energy is the converting of wind power to electrical power through the use of windmills or turbines.

Application of wind energy: 1- Mechanical Application: mainly (water pumping) Multi-blade windmill used for water pumping  
2- Electricity generation: Wind turbines vary in size and type. They are commercially available for electricity generation. Size of wind turbines (400 Watt-5 MW) 
How do wind turbines make electricity? 
The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity. 
Wind turbine types: 
1- Vertical axis wind  turbine
  Advantages 
Vertical wind turbines are easier to maintain because most of their moving parts are located near the ground. This is due to the vertical wind turbine’s shape. The airfoils or rotor blades are connected by arms to a shaft that sits on a bearing and drives a generator below, usually by first connecting to a gearbox. As the rotor blades are vertical, a yaw device is not needed, reducing the need for this bearing and its cost. Vertical wind turbines have a higher airfoil pitch angle, giving improved aerodynamics while decreasing drag at low and high pressures.
 Disadvantages 
There may be a height limitation to how tall a vertical wind turbine can be built and how much swept area it can have. Most VAWTS need to be installed on a relatively flat piece of land and some sites could be too steep for them while available to HAWTs. VAWTs that use guy wires to hold it in place create serious problems for the bottom bearing as all the weight of the rotor is on it and the guy wires increase downward thrust in wind gusts. Solving this problem requires a superstructure to hold in place the top bearing that also can share the weight of the rotor.
 Horizontal axis wind turbine (HAWT): Advantages 
 In the horizontal wind turbine, the blades are to the side of the turbine's centre of gravity, helping stability. They have the ability to wing warp, which gives the turbine blades the best angle of attack. Allowing the angle of attack to be remotely adjusted gives greater control, so the turbine collects the maximum amount of wind energy for the time of day and season. The blades also have the ability to pitch the rotor blades in a storm, to minimize damage. Tall towers allow access to stronger wind in sites with wind sheer. In some wind sheer sites, every ten meters up, the wind speed can increase by 20% and the power output by 34%. Tall towers also allow placement on uneven land or in offshore locations. These can be placed in forests above the treeline. Most are self-starting. The horizontal wind turbines can be cheaper because of higher production volume, larger sizes and, in general, higher capacity factors and efficiencies. 
Disadvantages 
 HAWTs have difficulty operating in near ground, turbulent winds because their yaw and blade bearings need smoother, more laminar wind flows. The tall towers and long blades (up to 180 feet long) are difficult to transport on sea and land. Transportation can now account for 20% of equipment costs. Tall HAWTs are difficult to install, needing very tall and expensive cranes and skilled operators. The supply of HAWTs is less than demand and between 2004 and 2006, turbine prices increased up to 60%. At the end of 2006, all major manufacturers were booked up with orders through 2008. The Federal Aviation Administration (USA) has raised concerns about tall HAWTs' effects on radar in proximity to air force bases. Height can be a safety hazard for low-altitude aircraft. Offshore towers can be a navigation problem. Downwind variants suffer from fatigue and structural failure caused by turbulence.
 Inside Wind 


Glossary Anemometer: Measures the wind speed and transmits wind speed data to the controller.
 Blades: Most turbines have either two or three blades. Wind blowing over the blades causes the blades to "lift" and rotate. Brake: A disc brake which can be applied mechanically, electrically, or hydraulically to stop the rotor in emergencies.
 Controller: The controller starts up the machine at wind speeds of about 8 to 16 miles per hour (mph) and shuts off the machine at about 65 mph. Turbines cannot operate at wind speeds above about 65 mph because their generators could overheat. 
Gear box: Gears connect the low-speed shaft to the high-speed shaft and increase the rotational speeds from about 30 to 60 rotations per minute (rpm) to about 1200 to 1500 rpm, the rotational speed required by most generators to produce electricity. The gear box is a costly (and heavy) part of the wind turbine and engineers are exploring "direct-drive" generators that operate at lower rotational speeds and don't need gear boxes. 
Generator: Usually an off-the-shelf induction generator that produces 60-cycle AC electricity. High-speed shaft: Drives the generator. 
Low-speed shaft: The rotor turns the low-speed shaft at about 30 to 60 rotations per minute. 
Nacelle: The rotor attaches to the nacelle, which sits atop the tower and includes the gear box, low- and high-speed shafts, generator, controller, and brake. A cover protects the components inside the nacelle. Some nacelles are large enough for a technician to stand inside while working. 
Pitch: Blades are turned, or pitched, out of the wind to keep the rotor from turning in winds that are too high or too low to produce electricity.
 Rotor: The blades and the hub together are called the rotor. 
Tower: Towers are made from tubular steel (shown here) or steel lattice. Because wind speed increases with height, taller towers enable turbines to capture more energy and generate more electricity.
 Wind direction: This is an "upwind" turbine, so-called because it operates facing into the wind. Other turbines are designed to run "downwind", facing away from the wind. Wind vane: Measures wind direction and communicates with the yaw drive to orient the turbine properly with respect to the wind. 
Yaw drive: Upwind turbines face into the wind; the yaw drive is used to keep the rotor facing into the wind as the wind direction changes. Downwind turbines don't require a yaw drive, the wind blows the rotor downwind.
 Yaw motor: Powers the yaw drive. 

The benefits of wind energy 
Wind energy is an ideal renewable energy because: 

1.  It is a pollution-free, infinitely sustainable form of energy. 
2. It doesn’t require fuel. 
3.  It doesn’t create greenhouse gasses. 
4. It doesn’t produce toxic or radioactive waste. Wind Energy & the Environment Wind is a clean fuel; wind power plants (also called wind farms) produce no air or water pollution because no fuel is burned to generate electricity.

 Drawbacks of Wind Machines
 The most serious environmental drawbacks to wind machines may be their negative effect on wild bird populations and the visual impact on the landscape. To some, the glistening blades of windmills on the horizon are an eyesore; to others, they're a beautiful alternative to conventional power plants

Geo-thermal energy

Geothermal energy-the heat of the Earth—is a clean, renewable resource that provides energy in the all around the world. 

What is geothermal energy? 

Heat has been radiating from the center of the Earth for some 4.5 billion years. At 6437.4 km (4,000 miles) deep, the center of the Earth hovers around the same temperatures as the sun's surface, 9932°F (5,500°C) (Figure 1). Scientists estimate that 42 million megawatts (MW) of power flow from the Earth’s interior, primarily by conduction Geothermal energy is a renewable resource.1 One of its biggest advantages is that it is constantly available. The constant flow of heat from the Earth ensures an inexhaustible and essentially limitless supply of energy for billions of years to come. 

Applications of geothermal energy

Depending on the depth of the borehole, one differentiates between two types of geothermal energy:

• Geothermal energy near the surface
  
  Up to 400 meters deep.
  For heat and cold production.

• Deep geothermal energy
  
  From a depth of 400 meters.
  For heating purposes or for electricity generation.

Geothermal energy near the surface

In geothermal energy applications, geothermal energy from up to 400 meters deep and temperatures around 25 ° C is used to heat and cool buildings and plants. Due to the still relatively low temperature, the heat energy from these depths is usually not used directly, but is raised to the required temperature level by means of heat pumps.

The same Geothermal energy system, which heats in winter, can also cool the building in summer. The subsoil can thus also be used directly as a source for climatic climates, which saves an expensive cooling production in air-conditioning systems.

Near-surface geothermal energy has proved to be an environmental-friendly alternative to fossil fuels for single and multi-family houses and is already widespread. Typical systems of near-surface geothermal energy are earth collectors, geothermal heat exchangers, groundwater fountains and geothermal heat probes.

Deep geothermal energy

Deep geothermal energy is opposed to the use of geothermal energy in other dimensions. Deep geothermal energy begins at a depth of 400 meters and below. Not only warmer springs are excavated at greater depths, boreholes of up to 7 km depth are drilled. The systems operated therewith are also significantly larger and more powerful.

With geothermal energy from deep geothermal energy, heating networks are fed and whole city areas are supplied with heating. If the temperature level is high enough, a geothermal power plant can also generate electricity. And, of course, baths can also be supplied with hot thermal water. Geothermal energy is not dependent on weather influences and can supply heat and electricity almost continuously throughout the year.

Deep geothermal energy can therefore be used as follows:

• Heat supply
  Local and long-distance heating of large public and commercial and industrial buildings, as well as of larger settlements and districts.
  But also to heat greenhouses for vegetable cultivation.
• Power generation
  Geothermically generated electricity is available around the clock and could be used as a base load for the power supply. For efficiency reasons, electricity is generated by means of deep geothermal energy in cogeneration of heat and power.

 Tidal energy

   Tidal power, also called tidal energy, is a form of hydropower that converts the energy of tides into useful forms of power – mainly electricity.

Although not yet widely used, tidal power has potential for future electricity generation. Tides are more predictable than wind energy and solar power. Among sources of renewable energy, tidal power has traditionally suffered from relatively high cost and limited availability of sites with sufficiently high tidal ranges or flow velocities, thus constricting its total availability. However, many recent technological developments and improvements, both in design (e.g. dynamic tidal power, tidal lagoons) and turbine technology (e.g. new axial turbines, cross flow turbines), indicate that the total availability of tidal power may be much higher than previously assumed, and that economic and environmental costs may be brought down to competitive levels. Tidal energy is a renewable energy source.

Tidal Energy Generators

There are currently three different ways to get tidal energy: tidal streams, barrages, and tidal lagoons.

For most tidal energy generators, turbines are placed in tidal streams. A tidal stream is a fast-flowing body of water created by tides. A turbine is a machine that takes energy from a flow of fluid. That fluid can be air (wind) or liquid (water). Because water is much more dense than air, tidal energy is more powerful than wind energy. Unlike wind, tides are predictable and stable. Where tidal generators are used, they produce a steady, reliable stream of electricity.

Placing turbines in tidal streams is complex, because the machines are large and disrupt the tide they are trying to harness. The environmental impact could be severe, depending on the size of the turbine and the site of the tidal stream. Turbines are most effective in shallow water. This produces more energy and allows ships to navigate around the turbines. A tidal generator’s turbine blades also turn slowly, which helps marine life avoid getting caught in the system.

History

The world’s first tidal power station was constructed in 2007 at Strangford Lough in Northern Ireland. The turbines are placed in a narrow strait between the Strangford Lough inlet and the Irish Sea. The tide can move at 4 meters (13 feet) per second across the strait.

Advantages of Tidal Energy

1. Renewable

Tidal Energy is a renewable energy source. This energy source is a result of the gravitational fields from both the sun and the moon, combined with the earth’s rotation around its axis, resulting in high and low tides.

It is this difference in potential energy that is the source of power generation from tidal energy, whether we are talking about stream generators, tidal barrages or more the more recent technology, dynamic tidal power (DTP).

So, why is tidal energy renewable? Compared to fossil fuels or nuclear reserves, the gravitational fields from the sun and the moon, as well as the earth’s rotation around its axis won’t cease to exist any time soon.

 2. Green

Tidal power is an environmentally friendly energy source. In addition to being a renewable energy, it does not emit any climate gases and does not take up a lot of space.

However, there are currently very few examples from real tidal power plants and their effects on the enviroment. An important task is therefore to study and assess these things.

 3. Predictable

Tidal currents are highly predictable. High and low tide develop with well-known cycles, making it easier to construct the system with right dimensions, since we already know what kind of powers the equipment will be exposed to.

Because of this, even though the turbines that are being used (tidal stream generators that is) are very similar to wind turbines, both the physical size and the installed capacity has entirely other limitations.

 4. Effective at Low Speeds

Water has 1000 times higher density than air, which makes it possible to generate electricity at low speeds. Calculations show that power can be generated even at 1m/s (equivalent to a little over 3ft/s).

 5. Long Lifespans

We have no reason to believe that tidal power plants are not long lived. This ultimately reduces the cost these power plants can sell their electricity, making tidal energy more cost-competitive. The tidal barrage power plant La Rance was opened already in 1966 and still generates large amounts of electricity.

Disadvantages of Tidal Energy

1. Environmental Effects

As previously mentioned, the effects tidal power plants have on the environment are not completely determined yet. We know that these power plants generate green electricity

Tidal barrages relies on manipulation on ocean levels and therefore potentially have the environmental effects on the environment similar to those of hydroelectric dams. Technological solutions that will resolve some of these issues are currently being developed.

 2. Close to Land

Tidal power plants needs to be constructed close to land. This is also an area where technological solutions are being worked on. Hopefully in a few years we can exploit weaker tidal currents, at locations further out in the sea.

 3. Expensive

It is important to realize that the methods for generating electricity from tidal energy is a relatively are relatively new technologies. It is projected that tidal power will be commercially profitable within 2020 with better technology and larger scales.

Wave energy

 wave energy is a energy which generate from the ocean waves. by using wave energy converter.

wave energy converter

Vast and reliable, wave power has long been considered as one of the most promising renewable energy sources. Wave Energy Converters (WECs) convert wave power into electricity. Although attempts to utilize this resource date back to at least 1890, wave power is currently not widely employed (Miller, 2004^[1]). The plethora of innovational ideas for wave power conversion have been invented in the last three decades, resulting in thousands of patents over recent years. At present, a number of different wave energy concepts are being investigated by companies and academic research groups around the world. Although many working designs have been developed and tested through modelling and wave tank-tests, only a few concepts have progressed to sea testing. Rapidly decreasing costs however, should enable wave plants to compete favorably with conventional power plants in the near future

Advantages of Wave Energy

1. Renewable: The best thing about wave energy is that it will never run out. There will always be waves crashing upon the shores of nations, near the populated coastal regions. The waves flow back from the shore, but they always return. Unlike fossil fuels, which are running out, in some places in the world, just as quickly as people can discover them. Unlike ethanol, a corn product, waves are not limited by a season. They require no input from man to make their power, and they can always be counted on.

2. Environment Friendly: Also unlike fossil fuels, creating power from waves creates no harmful byproducts such as gas, waste, and pollution. The energy from waves can be taken directly into electricity-producing machinery and used to power generators and power plants nearby. In today’s energy-powered world, a source of clean energy is hard to come by.

3. Abundant and Widely Available :Another benefit to using this energy is its nearness to places that can use it. Lots of big cities and harbors are next to the ocean and can harness the power of the waves for their use. Coastal cities tend to be well-populated, so lots of people can get use from wave energy plants.

4. Variety of Ways To Harness : A final benefit is that there are a variety of ways to gather it. Current gathering methods range from installed power plant with hydro turbines to seafaring vessels equipped with massive structures that are laid into the sea to gather the wave energy.

5. Easily Predictable : The biggest advantages of wave power as against most of the other alternative energy sources is that it is easily predictable and can be used to calculate the amount that it can produce. The wave energy is consistent and proves much better than other sources which are dependent on wind or sun exposure.

6. Less Dependency on Foreign Oil Cos : Dependence on foreign companies for fossil fuels can be reduced if energy from wave power can be extracted up to its maximum. Not only it will help to curb air pollution but can also provide green jobs to millions of people.

7. No Damage to Land : Unlike fossil fuels which cause massive damage to land as they can leave large holes while extracting energy from them , wave power does not cause any damage to earth. It is safe, clean and one of the preferred method to extract energy from ocean.

Disadvantage

1. Suitable to Certain Locations : The biggest disadvantage to getting your energy from the waves is location. Only power plants and towns near the ocean will benefit directly from it. Because of its source, wave energy is not a viable power source for everyone. Landlocked nations and cities far from the sea have to find alternate sources of power, so wave energy is not the clean energy solution for everyone.

2. Effect on marine Ecosystem : As clean as wave energy is, it still creates hazards for some of the creatures near it. Large machines have to be put near and in the water to gather energy from the waves. These machines disturb the seafloor, change the habitat of near-shore creatures (like crabs and starfish) and create noise that disturbs the sea life around them. There is also a danger of toxic chemicals that are used on wave energy platforms spilling and polluting the water near them.

3. Source of Disturbance for Private and Commercial Vessels : Another downside is that it disturbs commercial and private vessels. Power plants that gather wave energy have to be placed by the coastline to do their job, and they have to be near cities and other populated areas to be of much use to anybody. But these are places that are major thoroughfares for cargo ships, cruise ships, recreational vehicles and beach goers. All of these people and vessels will be disrupted by the installation of a wave energy gathering source. This means that government officials and private companies that want to invest in wave energy sources have to take into account and consider the needs of those they may be disturbing.

4. Wavelength : Wind power is highly dependent on wavelength i.e. wave speed, wave length, wavelength and water density. They require a consistent flow of powerful waves to generate significant amount of wave power. Some areas experience unreliable wave behavior and it becomes unpredictable to forecast accurate wave power and therefore cannot be trusted as reliable energy source.

5. Weak Performance in Rough Weather : The performance of wave power drops significantly during rough weather. They must withstand rough weather.

Wave power formula

In deep water where the water depth is larger than half the wavelength, the wave energy flux is

with P the wave energy flux per unit of wave-crest length, H_m0 the significant wave height, T_e the wave energy period, ρ the water density and g the acceleration by gravity. The above formula states that wave power is proportional to the wave energy period and to the square of the wave height. When the significant wave height is given in metres, and the wave period in seconds, the result is the wave power in kilowatts (kW) per metre of wavefront length.

Example: Consider moderate ocean swells, in deep water, a few km off a coastline, with a wave height of 3 m and a wave energy period of 8 seconds. Using the formula to solve for power, we get

meaning there are 36 kilowatts of power potential per meter of wave crest.

In major storms, the largest waves offshore are about 15 meters high and have a period of about 15 seconds. According to the above formula, such waves carry about 1.7 MW of power across each metre of wavefront.

An effective wave power device captures as much as possible of the wave energy flux. As a result, the waves will be of lower height in the region behind the wave power device.

Wave energy and wave-energy flux

In a sea state, the average(mean) energy density per unit area of gravity waves on the water surface is proportional to the wave height squared, according to linear wave theory:

 

where E is the mean wave energy density per unit horizontal area (J/m²), the sum of kinetic and potential energy density per unit horizontal area. The potential energy density is equal to the kinetic energy,^[4] both contributing half to the wave energy density E, as can be expected from the equipartition theorem. In ocean waves, surface tension effects are negligible for wavelengths above a few decimetres.

As the waves propagate, their energy is transported. The energy transport velocity is the group velocity. As a result, the wave energy flux, through a vertical plane of unit width perpendicular to the wave propagation direction, is equal to:

with c_g the group velocity (m/s). Due to the dispersion relation for water waves under the action of gravity, the group velocity depends on the wavelength λ, or equivalently, on the wave period T. Further, the dispersion relation is a function of the water depth h. As a result, the group velocity behaves differently in the limits of deep and shallow water, and at intermediate depths