Hydro-electricity systems convert the energy of falling water into electricity. There are a number of small hydro schemes on rivers and streams around New Zealand. There are also many more opportunities to use hydro energy to power remote farms and homes.
Small-scale hydro-electric facilities use a renewable energy source and don’t produce any greenhouse gases while operating.
Small scale hydro-electric facilities are generally classified into three sizes:
- Micro is up to 10kW
- Mini is between 10kW and 1000kW
- Small is between 1000kW and 10MW.
Most micro hydro systems for houses and buildings are less than 5kW, and in many cases less than 1kW.
Micro and small hydro systems use the force of running water to turn turbine blades, which spin a shaft connected to a generator. The generator uses magnetic fields to convert this rotational energy into electricity.
Micro hydro systems are usually "run of river", which means that they do not require water storage in the form of a dam or weir. Instead, a portion of the stream or river is usually temporarily diverted into a pipe system and on to the micro-hydro turbine and generator, before being returned to the stream.
Because they often do not require dams or significant storage, they have significantly less impact on the environment than large hydro schemes. If the micro or small hydro scheme does require a dam or other form of water storage, additional consenting requirements will be necessary.
Micro and small hydro systems are best suited to rural sites close to a source of flowing water. They can be set up wherever water falls from a higher lever to a lower level – such as a waterfall, hillside, stream, or where a reservoir discharges into a river.
The type of turbine required will depend on the head (the vertical fall) and the flow rate of the water. Pelton wheels are the type of turbine most commonly used for small scale domestic generation.
You should get expert advice to help you design and install your micro-hydro system.
The waterway needs to be suitable
Ideally you need a good year round flow of water. It needs to have an adequate drop in height over a small horizontal distance, and not be prone to severe flooding.
Compared with wind or solar, micro-hydro systems are more capable of providing a constant flow of electricity, as long as the water resource remains uninterrupted.
A resource consent may be required from the local regional council before anyone can take or use water for generating electricity.
You will need to allow for maintenance of mechanical, electrical and hydraulic equipment, although this may only involve a few hours a month. Intake screens need to be kept clear of silt and debris, and impoundment lakes may require de-silting every few years.
Costs will vary depending on your location and requirements. Each micro hydro system is designed to suit the specific features of the property. For a domestic-scale system with a basic layout you should expect to pay at least $10,000 to $15,000.
Despite the high capital cost, the running costs are low, resulting in ongoing savings. Micro hydro can be the most cost-effective microgeneration technology.
Factors influencing cost include:
- Size – larger systems are generally cheaper on a per kW basis
- Geography and geology – depending on your site, it might take a few days or a few weeks to install your system, so labour costs can vary
- Damming – if you need to build a dam to store water it will cost more
- Earth works and flood protection may be needed
- Length of water pipes and electrical cables
- Building and resource consents.
- Stand alone power systems - this provides more information on getting "off-grid"
- The Sustainable Electricity Association of New Zealand (SEANZ) is the industry organisation which promotes micro-scale renewable energy technologies
- Hydro energy in New Zealand
- Grid-connected systems.