Small Scale Hydro Power is an important energy source with multiple advantages over other forms of renewable energy, and if designed and installed correctly, has very few environmental risks. As the potential energy of flowing water is readily available, small scale hydro power systems can exploit this free energy providing a low cost and reliable source of “green electricity”.

Generally, all you need for a “small scale hydro power” system is a stream or a river with enough water running through it at the right volume or pressure that can feed a water turbine connected to a generator that will supply power your home. Just as you can with a solar energy or a wind energy renewable system, you can also design a small hydro energy system that is either grid connected, grid connected with battery backup or stand alone.

But what do we mean by a “small scale hydro” system. Small scale hydro power systems are scaled down versions of the much larger hydro generating stations we see using big dams and reservoirs to supply power to millions of people. Depending upon the physical size, head height and electrical power generating capacity, small hydroelectric schemes can be categorised into small, mini and micro scale hydro schemes as follows:

• Small Scale Hydro Power: is a scheme that generates electrical power of between 100kW (kilo-watts) and 1MW (mega-watts) feeding this generated power directly into the utility grid or as part of a large stand alone scheme powering more than one household.
• Mini Scale Hydro Power: is a scheme that generates power between 5kW and 100 kW, feeding it directly into the utility grid or as part of a battery charging or AC powered stand alone system.
• Micro Scale Hydro Power: is usually the classification given to a small home made run-of-river type scheme that use DC generator designs to produce electrical power between a few hundred watts up to 5kW as part of a battery charging stand alone system.

Small scale hydro power systems, as well as Mini Hydro Systems or Micro Hydro Systems, can be designed by using either waterwheels or impulse type hydro turbines. The generation potential of a particular site will depend upon the amount of flow of the water, the available head which in turn is dependant upon the site conditions and location and the rainfall characteristics of the site.

If there is sufficient head and flow, small hydro power plants can be driven directly from a river or stream, called a “run-of-river” system built into or at the side of a river or a stream without the need to dam, divert or change the flow of water in any way. Making them the cheapest solution for generating power.

In a run-of-river hydro scheme, the flow of the water is not altered, so its minimum flow rate needs to be the same or higher than that of the proposed turbine output power ensuring maximum efficiency. The result is that the costs involved for a run-of-river scheme are much lower and have less environmental impact than other small scale hydro plants. The disadvantage is that the water flow rate is variable throughout the year and the system is unable to store the waters energy.

The development of a small scale hydro power electrical schemes which uses a small dam or weir, water storage reservoir (impoundment) or requires a diversion of the rivers water flow through tunnels or canals, requires far more water usage in total as well as more complex civil and ground engineering works to match the site elevation not to mention the environmental impact that’s proportional to the size of the scheme.

However, a reservoir impoundment system or high head system has a much higher electrical generating potential than that of a much smaller run-of-river scheme due to the increased volume and velocity of the usable water, compensating for the larger capital investment, but costs can be kept down with simple design and practical, easily-constructed civil and mechanical works.