ARE WATER WHEELS A RURAL COST-EFFECTIVE ENERGY TECHNOLOGY?
Palavras-chave:Water pumping, Low flow, Low pressure-head
Water wheels are an economically viable alternative to electrical water pumping in rural areas. This study constructed and analyzed a small-flow water wheel with a low pressure head, built from materials that are easily accessible and inexpensive. The flow rate was measured under different elevation conditions (1–7.5 m) and perimeter blade velocities (0.5–3.0 m s-1). Energy efficiency was estimated, and two equations were proposed to describe the relationship between flow rate, trough velocity, and pressure head. The initial start-up cost of the equipment is approximately 50% of the minimum wage in Brazil. The attractiveness of the initial investment in relation to the pumping capacity is equivalent to that of photovoltaic systems. In places where the river velocity is approximately 1.5 m s-1, the water wheel can irrigate an area of 200 m², while raising water to 22 m of pressure head. The equipment has a low initial cost and low efficiency in terms of energy transformation; however, it is a promising water pumping technology at small elevations with watercourses moving approximately 1.5 m.s-1.