where a1 ¼ 0.6, a2 ¼ 0.2, a3 ¼ 0.2 are weight factors representing
the expected percentage of operational time at each off-design
loading. Values given were choosen such that a direct comparision
may be made with data presented by Singh [2], although these
may be changed to reflect conditions at a given site.
The performance of the designed micro-hydro turbine unit with
incorporated inlet flow control is compared to performance results
of a similar traditional PAT unit presented by Singh [2]. The traditional
PAT tested by Singh [2] had undergone numerous stages of
optimisation including impeller blade tip rounding and tapered
ring inserts, resulting in an increased peak efficiency of 83.4%, while
the designed micro-hydro turbine runner had not undergone any
modifications. Even so, the improved performance at off-design
conditions has essentially made up for a 4.4% disparity in peak efficiency
with WAEs of 76.8% and 76.9% for the new micro-hydro
turbine and the optimised PAT, respectively. This is further illustrated
in Fig. 7.