A Series of Presentation to Class By Mr. Allah Dad Khan Agriculture Free Lance Consultant and Adviser KPK Pakistan

3. Energies Sources
(Tidal Energy History )
A
Presentation
By
Mr. Allah Dad Khan
Agriculture Free Lance
Consultant and Adviser KPK
Pakistan

4. History of Tidal Power
The history of tidal power stretches into antiquity. The earliest
evidence of the use of the oceans’ tides for power conversion
dates back to about 900 A.D., but it is likely that there were
predecessors lost in the anonymity of prehistory. Early tidal
power plants utilized naturally-occurring tidal basins by building
a barrage (dam) across the opening of the basin and allowing
the basin to fill on the rising tide, impounding the water as the
tide fell, and then releasing the impounded water through a
waterwheel, paddlewheeel or similar energy-conversion device.
The power was typically used for grinding grains into flour.
Power was available for about two to three hours, usually twice
a day.[i] In Hayle, England, tidal power was used to “dredge” a
shipping channel by flushing it regularly with a pulse of stored
tidally-impounded water

5. Existing Tidal Power Plants
The power requirements of the industrialized world dwarf
the output of the early tidal barrages and it was not until
the 1960’s that the first commercial-scale modern-era tidal
power plant was built, near St. Malo, France. The hydro
mechanical devices such as the paddlewheel and the
overshot waterwheel have given way to highly-efficient
bulb-type hydroelectric turbine/generator sets. The tidal
barrage at St. Malo uses twenty-four 10-megawatt low-
head bulb-type turbine generator sets. Installed in 1965,
the barrage has been functioning without missing a tide for
more than 37 years.The second commercial-scale tidal
barrage wa

6. Existing Tidal Power Plants
s put in service at Annapolis Royale, Nova Scotia, Canada
in 1982 in order to demonstrate the functioning of the
STRAFLO turbine, invented by Escher-Wyss of
Switzerland and manufactured by GE in Canada. This 16-
megawatt turbine had some difficulties with clogging seals
necessitating two forced outages, but has been functioning
without interruption since its early days. There are
approximately 10 small barrages scattered throughout the
world, but they are not intended for commercial power
generation. For example, there is a 200 kw tidal barrage on
the River Tawe in Swansea Bay, Wales that operates the
gates of a lock. China has several tidal barrages of 400 kw
and less in size.

7. Existing Tidal Power Plants
Numerous studies have been conducted for large-scale
tidal barrages in a variety of locations,[iii] but the grandest
proposal of all is the 8640-Megawatt Severn Tidal Barrage
(“STB”) proposal. A broad range of studies was conducted
from 1974 to 1987 on this proposal to dam the Severn
Estuary between Wales and England. The tidal range in
the Severn is upwards to 40 feet in places and the
potential power from a barrage could provide 12% of the
United Kingdom’s requirements. Major engineering
consultancies, large construction companies, several
universities, and the U.K. Government’s Department of
Trade and Industry combined to fund and conduct the 13
years of studies costing almost $100 million.

8. Existing Tidal Power Plants
 The STB proposal was shelved in 1987 due to “economic
problems,” but the proposal likely would have met with
fierce opposition from a broad array of environmental
groups and local inhabitants. The STB and other large-
scale tidal barrages suffer from four types of
environmental problems:
 · Barrages block navigation
 A barrage is a dam across a tidally-affected inlet or
estuary and blocks the egress to the ocean. Locks can be
installed, as they are in France, or not, as in Canada. The
lock allows some traffic, but it is a slow and costly
alternative to free access to the ocean.

9. Barrages impede fish migration
Anadromous fish spawn in fresh water and outmigrate to
salt water, then return after three or four years to spawn
and die, ineffably drawn to the exact location of their birth.
Fish are, therefore, instinctively obliged to pass through
the turbines of an intervening barrage at least twice. Some
fish actually pass through the turbines multiple times
during one outmigration or one return. The mortality rate
for fish passing through the low-head turbine is about 6%.
Fish ladders are sometimes provided as an alternative
means of bypassing the dam, but the mortality rate of fish
ladders is slightly higher than that of passing through the
turbines and most fish avoid them.

10. Barrages change the size and location of the
intertidal zone
The intertidal zone is the area that is alternatively wet
and dry during the tidal cycles. The wet/dry habitat is
unique and only certain types of plants and creatures
thrive there. A barrage re-times the tidal cycle and
changes the water levels, thereby “moving” the wet/dry
intertidal zone, obliging the plant and animal life to
adapt or “move” to the new location. The humans
living around the headpond of the tidal barrage in
Annapolis Royale, Canada, have limited the
functioning of the barrage so as to maintain water
levels that are nearly normal, but at a cost of about
50% of the potential output of the 16-megawatt unit.

11. Barrages change the tidal regime downstream
Canada’s Bay of Fundy has the largest tidal ranges in the world
and has been the subject of numerous studies of proposed tidal
power plant installations. Huge barrages have been proposed
and one of the major concerns was the fact that coastal process
modeling conjectured that the highest tides downstream of the
barrage might be raised as much as 9 inches as far away as
Boston, more than 800 miles. This finding was controversial,
but, even the possibility of such an impact was seen as sufficient
to draw lawsuits from every property owner with a flooded
basement from Nova Scotia to Cape Cod. Similarly, the Severn
Estuary is the outbound pathway for much of the waste created
in central England and southern Wales and the proposed
barrage would make a 1300 square mile head pond and impede
that flushing action, thereby forming the world’s most offensive
body of water.

12. Economic Problems of Barrages
The aforementioned environmental problems of tidal
barrages have created opposition from environmental
groups and local inhabitants, requiring either (1) costly
efforts to overcome the objections through further
studies or (2) abandonment of the proposals. The
barrage also suffers from high capital costs and a
relatively low load factor (environmental
considerations limit generation to single-effect ebb
tide-only generation) of about 28%.