Table 6, Qualitative comparison of the environmental performance of a hypothetical linked-basins TPP of the flow-through type, as described in this section vis–vis the chosen standard of comparison, a single-basin, double-effect TPP, Type Z, at Fundy s Cumberland Basin. The tabulation shows which of the two types scores highest for optimum environmental performance.
Environmental effects |
|
|
A |
B |
C |
E |
F |
Type of TPP |
Linked-Bs, SE, flow through type at an imaginary site |
Single-basin, DE, at Fundy Cumberland Basin. Tyoe Z |
|
|
|
|
Size of linked-bs too small to affect tidal regimes |
TPP parameters |
|
|
|
|
|
|
|
Mean, natural tidal range |
5.64 m |
10.0 m |
|
|
|
|
|
Mean tidal range within hign basin as % of natural tide |
49% |
68 % |
Z |
Z |
|
|
|
Mean tidal range within low basin as % of natural tide |
46% |
68 % |
Z |
Z |
|
|
|
Mean water level within high basin, compared to natural conditions |
+1.28m |
-0.12m |
|
Z |
|
Z |
|
Mean water level within low basin compared to natural conditions |
-1.02m |
-0.12m |
|
Z |
|
Linked-Bs |
|
Number of passes through turbines for a fish going in-and-out of TPP |
1 |
2 |
|
|
Linked-Bs |
|
|
Plant operation at or close to the rhythm of the natural tide |
no |
yes |
|
|
|
|
|
Maximum head across turbines |
3.68m |
4.62m |
|
|
Linked Bs |
|
|
Maximum water velocities through turbines |
11.47m/sec |
11.9m/sec |
|
|
Linked-Bs |
|
|
Stagnant flow within high basin % of the time |
35% |
18 % |
Z |
|
|
|
|
Stagnant flow within low basin % of the time |
35 % |
18 % |
Z |
|
|
|
|
Simplicity and effectiveness of flow patterns |
See Fig. 6 |
|
linked Bs |
|
|
|
|
Total scores for Linked-Bs, SE plant, through-type layout |
|
|
10 |
0 |
3 |
1 |
|
Total scores for Type Z, DE |
|
|
4 |
4 |
0 |
1 |
|
NOTE: Re D, Sea-mammal survival: TPPs should be designed and operated to keep sea mammals away from the hydraulic turbines. This applies equally to both types B and Z and therefore does not affect a comparison between the two.
DE = double-effect; SE = single effect; HB = high-basin; LB = low-basin Linked-Bs = linked-basins