Small hydro goes full circle

By Philippa Martin-King

When people think of renewable energy, they often overlook the power of water and its capacity to generate electricity. Yet hydropower is one of the oldest forms both of mechanical and electrical power. Starting in waterwheel-powered mills, water turbines were subsequently developed during the industrial revolution to provide mechanical power to factories. Once electrical generators were invented, it took only a few years to couple them to hydro turbines to produce hydro-electric power, and soon they were used to supply electricity to remote communities. All of these installations were small hydro. In the 20th century larger hydro schemes were built to supply the higher demands of networks and large scale industry. As the economies of scale increased, so mega projects such as the Grand Coulee, Itaipu and the Three Gorges developed, and small hydro took a back seat to its big brother. However it was found that these large hydro projects had significant social, economic and ecological consequences, although these are ameliorated by modern schemes. Small hydro projects are now experiencing a resurgence because they are much less invasive.

The Laxey wheel is the largest in the world The Laxey wheel is the largest in the world

The huge capacity of hydropower

Hydropower has the capacity to generate more electricity than all other renewables combined. The turbine-generators used now are so refined that their combined efficiency can occasionally exceed 95 %, roughly twice that of any other form of electricity generation. (Only cogeneration-plants using waste energy in the form of hot water for district heating can exceed this, and not all of the energy produced is electrical.)

Currently hydropower produces roughly 20 % of global installed electrical power capacity, measured in GW (gigawatt). In terms of energy production that corresponds to 17 % of the world’s total electrical energy measured in GWh (gigawatt hour), and 72 % of all installed renewable electrical energy. Hydropower constitutes over 50 % of the electricity supply in at least 63 countries in the world.

Smaller is less noticeable

Today numerous countries already have large hydropower installations, but if many of the larger economic sites have already been exploited, there are a multitude of lesser sites suitable for small hydro projects that have yet to be developed. While they can be connected to larger grids, they can also be used for rural electrification projects that do not require vast and robust electrical distribution networks.

Fewer environmental difficulties

Many of the environmental difficulties experienced with large hydro do not present a problem for small hydro projects. They can be designed with little or no storage capacity as "run of the river projects". These do not have reservoirs that silt up, nor do they prevent nutrients travelling downstream. They can incorporate fish passes to enable migration to occur so that fish can return to their spawning places. They do not require any resettlement of local populations or flooding of land for reservoirs and their environmental impact is minimal. Because the civil engineering works are comparatively small scale, these projects can be constructed in as little as 12-18 months, resulting in a fast payback on investment.

IEC TC 4 for every size of hydro

IEC TC 4: Hydraulic Turbines, was established nearly 100 years ago, less than a decade after the IEC was founded. The Technical Committee has produced many International Standards and Technical Reports for equipment for all sizes of hydraulic rotating machinery. TC 4, realizing that small hydro has its own special requirements, produced, for example, IEC 61116, Equipment guide for small hydro. This provides background information and checklists of requirements and so ensures that developers are aware of all the issues involved in writing comprehensive specifications.

At the end of 2010, TC 4 produced IEC 62006, Hydraulic machines – Acceptance tests of small hydroelectric installations. Other publications on testing and commissioning large hydro systems exist, but these are not always applicable or economically viable for small hydro projects. The new International Standard has taken the relevant parts of these publications and rewritten them specifically from the viewpoint of small hydro systems, adding some extra new material. IEC 62006 provides an appropriate level of performance testing for small hydro projects and deals with the types of turbine specific to them but overlooked by other International Standards. It groups together the relevant rules for safety and performance testing during commissioning and start-up; trial operation and reliability tests; cavitation, noise and vibration guarantees, in a single publication. For many small hydro projects IEC 62006 can be used per se, without further reference to multiple other standards.

Hydroelectricity was first used to power mills Hydroelectricity was first used to power mills
The Laxey wheel is the largest in the world The Laxey wheel is the largest in the world
Water-powered mill. Water-powered mill.