Anyone living in a remote area without an existing connection to the national grid faces potentially expensive solutions to their power requirements. Previous articles have looked at solar and wind options, and the likely costs involved relative to bringing in a line from the nearest existing power pole. There is another possibility, which can offer a viable alternative in some cases: a micro-hydro system.
The obvious need is for a permanent water supply, with enough fall/flow to operate the turbine efficiently and generate adequate power for your needs. The power output required for houses and farm outbuildings is usually up to 5kW, as for solar and wind sources. For larger requirements, a mini-hydro system can provide 5-20kW, while small commercial hydro systems lie in the 20kW-10MW range.
All hydro generation systems, regardless of output, rely on the force of running water to turn turbine blades. These spin the shaft, which is connected to the generator. Unlike large-scale commercial hydro generation, farm-based micro-hydro systems don't need a storage dam. Water is merely diverted into a pipe system and then returned to the same watercourse. Such systems can be set up wherever water falls from a higher level to a lower one, so if you have a hilly site with a permanent stream, or a waterfall, your property may be ideally suited to this kind of power generation. The key word here is "permanent": while a hydro system can be one of the most reliable sources of electricity, compared to fluctuations in available sunlight or wind levels, it fails completely if your water source runs dry.
One advantage of micro-hydro systems is that although maintenance is needed for the mechanical, hydraulic and electrical components, the demands are not great and may generally involve just a few hours a month of routine debris and silt clearing. In addition, although the initial installation costs are, as with all alternative power systems, quite high (probably $15,000 upwards), the ongoing running costs are low – some sources claim that micro-hydro can be the most cost-effective method of power generation. As with other alternative power systems, if you generate power surplus to your requirements and do have a connection to the national grid, you can sell power back to the system.
The basic components of any micro-hydro system comprise a water intake system, a filter to remove debris, a penstock to transfer water to the turbine, the turbine itself, an alternator to produce AC current, a rectifier to generate DC current if the power is being stored in a battery system, cabling to transfer the electricity from the generator to either the point of use or battery storage, a water outlet or tailrace system to return the water back to the source, and a spillway or bypass system to deal with excess water flow or to allow you to shut the system down for maintenance. For more details about the component parts and how they function, see this site which also provides simple calculation systems for determining potential generation from your particular water source.
It is also important to consider the legalities around installing micro-hydro systems – there is always the potential to inflict environmental damage by interfering with water flows in streams and rivers, and you will need consent from the appropriate authorities before proceeding. You may, for example, be required to provide fish ladders if your system includes a dam or weir, and there will be maximum levels of flow diversion related to the minimum seasonal flow rate of the water source. You may need resource consent from your local regional council to take water for generation purposes, so check this before proceeding with your design and installation. Some basic background on legal requirements, along with general principles for micro-hydro systems, can be found at this site, which also contains further general links to resource consents and legal restrictions on DIY electrical work.
There are a number of sources available online which provide specific case histories of micro-hydro installation, looking at practical details and costs. EECA has an on-farm technical guide which gives some background information, and for those interested in more specific details, an ME thesis from the University of Canterbury is available online, discussing in depth the design of systems to cope with commonly encountered hill country operating conditions, with heads ranging from 30 to 150m and flows ranging between 10 and 30 litres per second.
There are a number of suppliers of components for micro-hydro systems in New Zealand. One which also has links to measuring head and flow for your site can be found here, and a video of a specific installation procedure can be located on this YouTube site. For systems which will handle heads as low as 5m, this site and this one may be helpful, and if you need quick access to a list of suppliers of alternative power systems, including hydro, in New Zealand, try here.
If your land has a permanent water source, with adequate year-round flow and head, a micro-hydro system may be a cost-effective, viable option for your power requirements, and may even be a source of a small potential income if you are able to feed excess generation back into the national grid. Before proceeding, be careful to check legal obligations surrounding the use of water in your region, and investigate as many suppliers as possible, so that you get the best system for your particular conditions.