Tidal force on a floating object has two elements:

1) Horizontal force: This is a one-directional force creates by tidal flow/current.

2) Vertical force: Is a bidirectional force creates by tidal waves with gravity.

Tidal horizontal force (and with others external any kind of wind forces) on a floating object can be opposed by anchor it properly (by using minimum four horizontal/ long-distance anchors) so that the vertical force remains almost the same. This vertical force is useful and it can be very much useful as easily increase this vertical force by “Archimedes Principle” (by increasing the size of the object). This bidirectional vertical force is very much suitable for pumping purposes. By installing pump protected by RCC structure, using the vertical upward force of the wave on an anchored floating object continuously sufficient water pumping possible for hydropower station and or desalination.

CALCULATION

Consider a piston cylinder, diameter Dc = 10 m. and     cylinder height ≥ maximum wave height. So the cross section area of cylinder

Ac = π*(Dc)2/4 = π*(10)2/4 m2 = 78.54 m2 …………………...….(1)

Let, wave heightis 3 m. So the piston can move 3 m.        

i.e. active length of cylinder Hc = 3 m.

If the piston is connected with a floating object then due to a tidal wave the amount of wáter will pump is

Q = Ac*Hc per wave = 78.54 X 3 m3/wave = 235.62 m3/wave

If the wave period is 10 seconds,[2]

Then Q = 235.62 m3/10 sec = 23.56 m3/sec ……………….(2)

Consider a floating ship of displacement tonnage 10,000.

(i.e. total weight of the ship is 10,000 ton).

According to Archimedes’ principle buoyant force (vertical upward force) on the floating ship due to the tidal wave is ≥10,000 ton force, i.e. VF ≥ 10,000 ton force.

Let, VF = 10000 ton force

=  98067.1kN……………………………………...(3)

If this force acting on the piston then, Pumping pressure

Ppump= Force/Area = VF/AC

               = 98067.1/78.54 kN/m2  [by eqn (1) & (3)]

             = 1248.63 kN/m2

As measured by a U-tube manometer, 1kN/m2 pressure can create a water head 0.102 m.[3]

Then for Pumping pressure Ppump=1248.63 kN/m2, water head

Hhead = 1248.63*0.102 m = 127m,

Consider head loss 13 m, then waterfall height

H = 127-13 = 114m.  ………………………..………….(4)

From formula to calculate hydropower, Generating power (Pgen) [4]

Pgen = Q*ρ*g*H*η watt, ……….(5)

Where,             Q = flow rate in m3/sec. [=23.56 m3/sec         eqn (2)]

                        ρ = water density in kg/m3    (sea water 1020 kg/m3)[5]

                        g = acceleration of gravity in m/sec2      (9.81m/sec2)

                        H = water fall height in meter. [=127m          eqn (4)]

                        η = global efficiency ratio.          {let here 0.8}     (Usually between 0.7 and 0.9)

Then eqn (5), Generating power

Pgen = 23.56*1020*9.81*(114)*0.8 watt,

               = 21,500,954 watt

               = 21.5 MW

Reservoir size:

We have,       Q = 23.56 m3/sec,

For 30 min backup operation, Water required will be:

VoL = 23.56*60*30 m3 = 42,408 m3

If reservoir depth is 3 m then

Reservoir area = 42,408/3 m2 = 14,136 m2,

For square shape area,

Reservoir length = width = √14,136 m = 119 m.

CONCLUTION

Hence, we can conclude that to generate 21.5 MW electricity from tidal wave we have to anchor a ship (total weight 10,000 ton) on the ocean wave height 3 m, need to be build a 119m*119m*3m size reservoir from (127-3) = 120 m above the sea level, have to be install a pump under the anchored ship of cylinder diameter 10 m, cylinder height ≥ maximum wave height in the installation area and a 21.5 MW water turbine generator.

The Earth is a watery place. About 71 percent of the Earth's surface is water-covered, and the oceans hold about 96.5 percent of all Earth's water. Considering the open space available in the ocean, we can easily install required numbers of ships to achieve the 100% renewable energy. Anchored big ships on the big wave can take a big role for the solution of future energy.

This is a very easy technique to harness energy from ocean tidal energy as already running some small projects. Capacity can be increased as required by increasing the size of the object and pump very easily. Expensive waterproof devices are not required for this easy technique.

Compare to the existing hydropower stations dam, big reservoir, big catchment area not required so cost effective. And so no need to think about the related problems like obstruct fish migration, changing natural water temperatures, water chemistry, river flow characteristics, silt loads, affect on ecology, physical characteristics of the river, negative effects on native plants, on animals in & around the river, problems on important natural areas, agricultural land, archeological sites, relocation of people etc.

Advantages:

#Zero emission, #Low cost renewable energy, #Very safe.

#Reject ships can be used as a floating object so that form a ship city.

# Very simple pumping operation so that  pump can be design for all size of wave

#Continuous pumping so no need a big reservoir for hydro power station and or desalination.

#Economic. #Easy technology. #Reliable #Unlimited. #Sufficient surface water can avoid lifting underground water.

***This anchored object method can be used directly in the river for irrigation purpose.