Table 4, Qualitative comparison of the environmental performance of a linked-basins TPP at Fundys Shepody Bay (HB) and Cumberland Basin(LB), vis–vis the chosen standard of comparison, a single-basin, DE-TPP, Type Z, at Fundys 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-basins, SE, Fundy (HB and LB) |
Single Basin, DE at Fundy (LB) |
|
|
|
|
|
TPP parameters |
|
|
|
|
|
|
|
Mean, natural tidal range |
10.m |
10m |
|
|
|
|
|
Mean tidal range within high basin as % of natural tide |
34 % |
68 % |
Z |
Z |
|
|
Z |
Mean tidal range within low basin as % of natural tide |
36% |
68% |
Z |
Z |
|
|
Z |
Mean water level within high basin, compared to natural conditions |
+2.9m |
-0.12m |
|
Z |
|
Z |
|
Mean water level within low basin. compared to natural conditions |
-2.6 m |
-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 |
|
|
|
|
Z |
Maximum head across turbines |
6.96m |
4.62m |
|
|
Z |
|
|
Maximum water velocities through turbines |
15.6m/sec |
11.9m/sec |
|
|
Z |
|
|
Stagnant flow within high basin % of the time |
42% |
18% |
Z |
|
|
|
|
Stagnant flow within low basin.% of the time |
42% |
18% |
Z |
|
|
|
|
Simplicity of flow patterns |
See Fig. 5 |
|
Z |
|
|
|
|
Total scores for Iinked-Bs, SE-TPP |
|
|
0 |
0 |
1 |
1 |
0 |
Total scores for Type Z (DE) plant |
|
|
5 |
4 |
2 |
1 |
3 |
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 linked-Bs and Type Z and therefore does not affect a comparison between them.
DE = double-effect; SE = single effect; HB = high-basin; LB = low-basin Linked-Bs = linked-basins