Hydroelectric systems

A small-scale hydroelectric system can be a cost-effective way to generate low carbon electricity for your business.

Plug into the power of running water

If you have access to the right stream or waterway, a small-scale hydroelectric system can be a cost-effective and reliable way to generate low carbon electricity for your business. Many small hydro schemes already exist on rivers and streams around New Zealand, and there are more opportunities to use water-driven generation for remote farms and businesses.

Small-scale hydroelectric systems are generally classified into three sizes:

  • micro-hydro - up to 5 kW, and often less than 1 kW
  • mini-hydro - between 5 kW and 20 kW
  • small commercial hydro - between 20 kW and 10 MW

How hydroelectricity works

Hydroelectricity systems use the force of running water to turn turbine blades, which spin a shaft connected to a generator. On rural sites they can be set up wherever water falls from a higher lever to a lower level, for example a waterfall, hillside, stream, or where a reservoir discharges into a river.

The type of turbine you need depends on the vertical distance the water falls and the rate the water flows. Pelton wheels are the type of turbine most commonly used for small scale domestic generation.

Micro-hydro systems are best suited to rural areas on streams or waterways that flow all year round. The more vertical distance (head) you have between the point where you take the water and where the turbine is located, the more electricity you can generate.

Small scale hydro systems don't usually need water storage. A portion of the stream or river is temporarily diverted through a pipe system to the micro-hydro turbine and generator. It's then returned to the same stream or river. This type of system has far less impact on the environment than large scale hydro schemes. If your small scale hydro scheme does need a dam or other form of water storage, you’ll need to get consent.

Sustainable Electricity Association of New Zealand (SEANZ)(external link)

 

Checklist for building a micro-hydro system

  • Get expert advice - to help you design and install your micro-hydro system.
  • Make sure the waterway is suitable - ideally it will have a good flow of water year round, and enough vertical drop over a small horizontal distance.
  • Ensure the water supply is reliable – with a constant volume of water flow, generation is more reliable than wind or solar.
  • Check out your rights to the water - you may need a resource consent from your regional council before using water to generate electricity.
  • Make allowances for maintenance - mechanical, electrical and hydraulic equipment may need monthly maintenance, if only for a few hours of maintenance a month. Intake screens need to be kept clear of silt and debris, and collection lakes may require de-silting every few years.

 

Cost depends on location and requirements

Each micro-hydro system is designed to suit the specific features of a property and factors including:

  • Size - larger systems are generally cheaper per kW.
  • Geography and geology - depending on your site, it might take a few days or a week to install your system.
  • Damming - if you need to build a dam to store water it will cost more.
  • Earth works and flood protection.
  • Length of water pipes and electrical cables.
  • Building and resource consents.

Micro-hydro can be extremely cost effective – low running costs mean you make ongoing savings.

How hydropower works(external link)