In the end of third quartile of 2020, 98.9% Indonesia’s national electrification ratio has been reached. The obstruction of 100% electrification is occurring in remotes areas. It is caused by demographical factors, including small population and incomes, accompanied by geographic and economic restriction on installing conventional power plant. To overcome this problem, gravitational water vortex turbine power plant can be an alternative to generate electricity even in most remotes area since it offers low cost in operating and maintenance as well as easy to manufacture compared to other type renewable energy power plant. It can generate electricity up to 5 kW capacities with low head and flow rate. In order to optimize the turbine performance, a study arranged to evaluate the effect of blade size and depth onto efficiency of the turbine. The study conducted numerically using Ansys Fluent within assumption of 1.03 m head and 0.16 m3/s flow rate. There are nine configurations in this study with varying rotor size of 200 mm, 350 mm, 500 mm and turbine depth of 270 mm, 340 mm, 410 mm. Result of study leads to conclusion that largest size and upper top position give highest performance of the turbine.
Keywords: numerical study; renewable energy; gravitational vortex; hydro turbine; depth-rotor ratio; efficiency