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Small Scale Hydro Electric Power

By: Dr Gareth Evans - Updated: 2 Sep 2012 | comments*Discuss
 
Small Scale Hydro Electric Power

Improvements in small power generating technology have begun to make hydro electric power look an increasingly attractive option for relatively small-scale projects.

Like the more familiar large hydro electric power plants which have been in operation for many years around the world, small scale systems use moving water to drive a turbine, which then generates electricity.

However, unlike its big relatives, which often have a major impact on the local environment by building dams and large diversion works, there is almost no interference to the waterway needed for small hydro electric power schemes, making the whole idea far more eco-friendly.

How Does It Work?

The basic principle is remarkably simple and well-known – water diverted from a river or stream flows through the turbine, turning it – and it then turns a generator to generate electricity. Aside of the efficiency of the generator itself, how much power can be produced depends on how far the water falls – called the “head” – how quickly it flows and its volume.

According to the Low Carbon Buildings Programme – a scheme which offers grant support for a range of renewable and micro-generation technologies – even a small stream can produce useful amounts of power. The likely output ranges from a few hundred watts for domestic schemes, to a minimum of 25kW for larger projects.

Advantages of Hydro Electric Power

Small-scale hydro electric power can claim to be one of the most reliable and cost-effective ways to generate clean electricity and offers a few advantages over wind, wave and solar photovoltaic approaches.

It has the best energy efficiency, typically between 70 and 90 per cent and has a high capacity factor – a measure of how much electricity it actually does produce compared with its maximum possible output. This is an important consideration for renewable energy, since there are time when although a system could produce electricity, there is nothing to drive it.

With water flow relatively constant and predictable, small-scale hydro electric power has a capacity factor of around 50 per cent, compared with 15 to 20 per cent for solar, and around 30 per cent for wind – which both rely on energy sources which can vary from minute to minute. The necessary equipment itself also has a relatively long lifespan and is generally robust in use.

Community Power

For areas with a good available water resource, community hydro electric projects can be a real possibility. However, it is important to remember that the capital costs are high and this approach to generation is only really appropriate if there is a suitable site close to where the power is going to be used or alternatively near to a grid connection.

On the plus-side, once everything is in place, the energy is effectively free and if the site is connected to the grid rather than providing stand-alone power, it can be possible to sell any surplus generated to the electricity supply company.

Never-the-less, taking on a hydro electric project on this sort of scale is likely to demand a considerable amount of time and effort from everyone involved – although the results can be well worth it in the long run. Fortunately Britain is home to a number of good manufacturers and experienced consultants, so there are plenty of people to turn to for sound advice along the way.

Obviously, any project will need to obtain a series of approvals and permissions before it can go ahead, so there are a range of people who will need to be consulted right from the outset.

These include the relevant local authority planning department, the Environment Agency (in England and Wales) or SEPA (in Scotland), the appropriate statutory environmental body – Natural England/Scottish Natural Heritage/ Countryside Commission for Wales – and any local fishing organisations. Depending on the site ownership, it might be necessary to include the land-owner and your regional electricity company too, if you’re looking to make a grid connection.

The costs of installing a small-scale hydro electric power scheme are highly dependent on the site, but according to UK Energy Saving, as a general guide you need to allow £4000 per kW up to 10kW with the per KW price becoming proportionally less for larger projects.

Despite the high initial cost and the work involved in steering the project to fruition, once installed, the latest generation of hydro electric micro-turbines offer the promise of clean, green energy for free. With conventional electric prices rising year-on-year, small wonder that this approach is beginning to look attractive.

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