Micro Hydro Power (MHP) - Pros and Cons

Micro Hydro Pros - Advantages

It only takes a small amount of flow (as little as few litres per minute) or a drop as low as 1 m to generate electricity with micro hydro. Electricity can be delivered as far as 1 km away to the location where it is being used. If planned carefully and well adapted to the environmental conditions, micro hydropower schemes produce a continuous and predictable supply of electrical energy in comparison to other small-scale renewable technologies. The peak energy season is during the winter months when large quantities of electricity are required. MHP is considered to function as a ‘run-of-river’ system, meaning that the water passing through the generator is directed back into the stream with relatively little impact on the surrounding ecology. In comparison to large hydropower, MHP thus only has a little negative environmental impact. Negative socio-economic impacts are even insignificant in comparison. Further advantages include low distribution and running costs (requires no fuel and only low maintenance) as well as local implemenation and management. Moreover, hydropower is a durable and robust technology; systems typically last for 50 years or more without major new investments.

Negative environmental and socio-economic impacts of large hydropower that do not apply to micro hydropower

The construction of large dams and associated civil structures can for example result in an alternation of water quantity in downstream areas, affecting long-practiced farming practices such as flood-dependant recession agriculture. Water quality and biodiversity can be decreased by increased erosion and thus sedimentation due to deforestation due to construction work and resettlement. Large hydropower plants’ reservoirs produce a significant amount of greenhouse gases such as carbon dioxides and methane, in some cases emissions are found to be higher than from plants running from fossil fuels. This is because, due to the initial flooding of the reservoir, a large amount of carbon tied in vegetation is released when the plants rot. Methane, on the other hand, builds up due to the anoxic decomposition of organic matter on the reservoirs’ bottom Resettlement programs associated with the construction of large dams also have a variety of socio-economic impacts. People are often relocated to less suitable areas (steep terrain or less fertile soils) which does not only increase land degradation but also puts them at high impoverishment risk. A further critical aspect associated with large hydropower projects is that costs and benefits do not necessarily accrue to the same group of people: local communities often have to bear high losses but do not benefit from the electricity supplied.

Furthermore, MHP can be considered a cost effective energy solution. Building a small-scale hydro-power system can cost from $1,000 - $20,000, depending on site electricity requirements and location. Maintenance fees are relatively small in comparison to other technologies. Due to the low-cost versatility and longevity of MHP, developing countries can manufacture and implement the technology to help supply much needed electricity to small communities and villages. If the MHP plant produces a large amount of excess energy, some power companies might buy back electricity overflow. Furthermore,it is possible to supplement the micro hydropower with intake from the power grid.

Micro Hydro Cons - Disadvantages

There are, however, a number of disadvantages that need to be taken into account. MHP plants require certain site conditions and are thus not suitable for any location. In order to take full advantage of the electrical potential of small streams, a suitable site is needed. Factors to consider are: distance from the power source to the location where energy is required, stream size (including flow rate, output and drop), and a balance of system components — inverter, batteries, controller, transmission line and pipelines. Limited technical know-how especially in resource-rich locations might impede hydropower development.

Furthermore, the size and flow of small streams may restrict future site expansion as the power demand increases.

As MHP plants require no reservoir, electricity generation is highly dependant on an constantly sufficient river discharge. In many locations stream size will fluctuate seasonally. During the summer months there will likely be less flow and therefore less power output. Advanced planning and research will be needed to ensure adequate energy requirements are met.

Finally, environmental impacts need to be taken into account. The ecological impact of small-scale hydro is minimal; however the low-level environmental effects must be taken into consideration before construction begins. Stream water will be diverted away from a portion of the stream, and proper caution must be exercised to ensure there will be no damaging impact on the local ecology or civil infrastructure. 

Further reading

For more information on pros and cons of large hydropower and dams in general, see World Commission on Dams.