Micro hydro generation
Many small hydro schemes already exist on rivers and streams around New Zealand, and there are many more opportunities to use water-driven generation to provide electricity to remote farms and homes.
Micro hydro electricity
Distributed (or small-scale) hydro-electric facilities are generally classified into three sizes:
- Micro-hydro is up to 5 kW (kilowatts)
- Mini-hydro is between 5 and 20 kW
- Small commercial hydro is between 20 kW and 10MW (megawatts).
Most micro hydro systems for houses and buildings are less than 5kW, and in many cases less than 1kW.
On this page:
How hydro-electric generation works
How hydro-electric generation works
Hydro-electricity systems convert the energy of moving water into electricity. Small-scale hydro systems don't usually require water storage in the form of a dam or weir. Instead, a portion of a stream or river is temporarily diverted into a pipe system and to the micro-hydro turbine and generator. It's then returned to its source. Because of this these types of system have far less impact on the environment than large scale hydro schemes.
If small-scale hydro schemes do need a dam or other form of water storage they also require additional consents.
Micro and small-scale hydro systems use the force of running water to turn turbine blades, which spin a shaft connected to a generator. These systems are best suited to rural sites, and 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.
Building a micro hydro scheme
Before you build a micro hydro generator:
- Seek expert advice to help you design and install your micro hydro system
- Ensure the waterway is suitable. Ideally it will have a good year round flow of water and an adequate drop in height over a small horizontal distance.
- Establish that the water supply is reliable. Compared with wind or solar generation, micro hydro systems are more capable of providing a constant flow of electricity - as long as the water resource remains uninterrupted
- Check out your rights to the water. A resource consent may be required from your regional council before using water for generating electricity
- Make allowances for maintenance of mechanical, electrical and hydraulic equipment. This may only involve a few hours a month. Intake screens need to be kept clear of silt and debris, and collection lakes may require de-silting every few years.
Costs of micro hydro
Costs will vary depending on location and your requirements (see below). 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 initial capital cost, running costs are low, resulting in ongoing savings. Micro hydro can be the most cost-effective micro-generation technology.
Factors influencing cost:
- 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
- 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.
Case studies
Marlborough luxury lodge goes for hydro power - case study
More information
- Download the Small Hydro Fact Sheet for more detailed information on how small hydro schemes work and how to assess the suitability of your river or stream.
- Download the Stand Alone Power Systems Fact Sheet for 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. You will find further helpful information at the SEANZ website.
- Efficiency first - by reducing your energy requirements, you'll reduce the amount (and cost) of generation you'll need.
- Stand alone power systems (SAPS) are off-grid electricity generation systems that may include photovoltaics, micro wind turbines or micro hydro, batteries and a back-up generator
- Grid-connected systems are electricity generation systems that may include photovoltaics, micro wind turbines or micro hydro. They are connected to the local electricity network, and can export excess electricity, or use mains electricity as a backup
- Choosing energy options explains what you should consider when deciding on the best generating options for your location
- Micro wind energy refers to the use of small wind turbines typically less than 10 kW
- Micro-generation is one form of distributed generation, which refers to local electricity generation connected to lines networks, rather than the national grid.
- More about use New Zealand's use of renewable energy.
