Microhydro Systems

Microhydro Developments

Microhydro installations can be designed to minimise the damage that may eventuate from modifying the natural environment. Due to their relatively small size they are less likely to cause major problems to the surrounding natural systems, and provide a reliable, cost-effective, proven and robust solution to providing energy services to areas where there are suitable hydrological resources for the application. Microhydro installations are a successful and sustainable solution to a lack of energy in many regions of the world. This technology is suitable for integration in all types of systems, from centralised electricity grids to domestic stand-alone power supplies.

Benefits

Hydropower is available in a range of sizes from a few watts to over 10 GW. At the low end of the scale, small hydro can be divided into three categories: micro (less than 100 kW), mini (100 kW to <1 MW) and small (1 MW to <10 MW) (Parliament of Australia, 2001). This section focuses on microhydro systems, which are generally stand-alone systems, and are not generally connected to the electricity grid. However this is starting to change.

Most microhydro systems are "run of the river" systems, which allows the river flow to continue. This is preferable from an environmental point of view as seasonal river flow patterns downstream are not affected and there is no flooding of valleys upstream of the system (Harvey, 1993). The systems can be built locally at low cost, and the simplicity gives rise to better long-term reliability.

Micro-hydro systems are particularly suitable as remote area power supplies for rural and isolated communities, as an economic alternative to extending the electricity grid. The systems provide a source of cheap, independent and continuous power, without degrading the environment. In addition, the micro-hydro technology is mature, with numerous sizes and designs available for specific applications that are tried, tested and affordable.

Constraints

People should be aware of the practical limitations of hydro systems and the issues that they may encounter in installing a microhydro turbine. While large hydro power has benefits in terms of carbon dioxide emissions and air pollution, it also has significant negative environmental impacts. Hydro-electric power installations have a detrimental effect on river flows and water supplies. Large-scale hydro schemes result in the flooding of large areas of land, often leading to the displacement of people living in the area, and to negative impacts on local fauna and flora. Proposed hydro power projects often face pressure from environment and human rights groups concerned about the social and environmental impacts of the projects, e.g. the 18.2GW Three Gorges dam project in China, the 2.4GW Bakun project in Malaysia, and the 400MW Maheshwar project in India. To appreciate the extent of the human impacts of building large-scale hydro installations it is estimated that between 1.2 and 1.9 million people forcibly lost their homes, farmland and livelihoods to flooding due to the construction of the Three Gorges Dam in China.

However microhydro systems are generally of such small scale and of different design so that the vast majority of these issues are not applicable. This is due to there being no requirement for dam construction and therefore villages and forests are not flooded. Also there are many different system designs that provide sufficient flexibility to reduce the impact of installations on fragile and ecologically sensitive areas.

Another disadvantage of many types of microhydro systems is that water is not stored from rainy to dry season, which can cause issues in providing enough electricity in the dry season. In addition, the excess power generated is wasted unless an electrical storage system is installed, or a suitable ‘off-peak’ use is found. Alternatively if the electricity grid exists and it is possible to install a grid-connected system in your area, then this excess electricity production can be exported to the grid, via net metering. To assist in the installation of an appropriate system that meets your requirements, a feasibility study is essential. This is used to better understand the particular hydro resource that you have and to establish the minimum production in the dry season and to ensure the installation will not be washed away in times of heavy rainfall.

There are two main types of turbines used in micro-hydro systems, depending on the flow and the head, namely impulse turbines and reaction turbines. Typical impulse turbines are the Pelton wheel and the Turgo wheel, and these are generally used for medium to high-head applications. Reaction turbines are generally used at low (propeller turbine) or medium head (Francis turbine) (Fraenkel et al, 1991).

There are many details to supplying quality electrical energy from a micro-hydro system. In an instantaneous power demand system, the system provides 240V AC power to the load via a turbine that must be sufficiently large to meet the peak power demand. These systems require a large head and/or flow. In a storage system, the micro-hydro generator provides a constant DC charge to a battery system, which then supplies power to the load via an inverter. The battery system must be sized to the daily electrical demand. However, the turbine is significantly smaller than for an instantaneous demand system, and it operates at a constant power output.

As mentioned in the small hydro technology file, micro-hydro systems in Australia are not well documented. A number of small micro-hydro units are available for domestic remote area power supplies, tourist facilities, cathodic protection for pipe lines etc. An example of a typical micro-hydro system in Australia is a home system situated on the Jack River, high in the Eastern Strzelecki Ranges near Yarram in Gippsland, Victoria. The owner Leon Trembath receives year round power from 2 micro-hydro turbines. The capture pond is 2 by 1 metres, and flows through a 250mm diameter pipe to the turbines. The micro-hydro generators are 4-nozzle Platypus Power units with Turgo turbines. They generate around 450 watts each of DC electricity, which is fed into a 24 volt, 850 amp-hour battery bank. Since 1994 they have run flawlessly. With little maintenance and a capital cost of less than $18,000 it compares favourably with the $20,000 grid connection fee and ongoing utility bills (Your Home, 2005). However, suitable micro-hydro resources, in locations where they can be utilised, are limited in Australia (DPIE, 1997).

Costs

Currently (2006), the typical cost of a 5kW micro-hydro unit (excluding civil works) is around A$10,000 (Your Home, 2004). This unit cost varies somewhat but is a good indicator of the cost of the technology. However the capital works required for such installations can run into several thousands depending on the topography of the site and the amount of water required to pass through the system to provide sufficient output.

Links to Suppliers and Further Information

RISE Information Portal - Information regarding renewable energy resources, technologies, applications, systems designs and case studies.

APACE

The International Journal on Hydropower and Dams

International Energy Outlook 2008

World Energy Council - 2007 Survey of Energy Resources

International Association for Small Hydro

Tamar Designs, Australia

Platypus Power

Rainbow Power Company

Canyon Hydro - High Efficiency Hydro Systems to about 100 kW

Your Home Tech Manual - Microhydro Systems

Pelena Energy

Why Hydro Power?

References

Parliament of Australia, 2001. “Renewable energy used for electricity generation in Australia” (Online), http://www.aph.gov.au/library/pubs/rp/2000-01/01RP08.htm (Accessed 3 Decemeber 2008).

Your Home, 2004. “Home- Micro-hydro systems” (Online), http://www.greenhouse.gov.au/yourhome/technical/fs49.htm (Accessed 3 Decemeber 2008).

Your Home, 2005. “RAPS CASE STUDY – A micro-hydro powered home” (Online), http://www.greenhouse.gov.au/renewable/power/raps-cs3.html (Accessed 3 Decemeber 2008).

Department of Primary Industries and Energy (DPIE) 1997, Renewable energy industry- survey on present and future contribution to the Australian economy, Australian Government Publishing Service, Canberra.

Fraenkel et al 1991, Micro-hydro power- a guide for development workers, Intermediate Technology Publications, London.

Harvey, A. 1993, Micro-hydro design manual- a guide to small-scale water power schemes, Intermediate Technology Publications, London.

Tamar Designs 1998, "Hydro turbines- turbine selection" (Online), http://www.tamar.com.au/ (Accessed 3 Decemeber 2008).

World Energy Council 1994, New renewable energy resources, Kogan Page, London.