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Can renewable energy sources power the world?
Can renewable energy sources power the world?

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9.4 Considerations and comparisons

The Hydropower Sustainability Assessment Protocol (HSAP, 2017), is the result of a collaboration by representatives of different sectors of the hydro industry, led by the International Hydropower Association (IHA).

Essentially a list of criteria that should be satisfied by any new hydroelectricity project, it is no doubt the response of the industry to many of the environmental issues discussed previously.

Environmental effects

Small-scale systems should have fewer deleterious effects than large systems, and in some respects this is evidently true – few people have been displaced from their homes by the installation of small 5 MW plants, whilst deaths from the collapse of dams across small streams seem rare. However, proponents of large-scale hydro claim dispute this ‘small is beautiful’ view – arguing that the efficiencies and the capacity factors of small-scale plants tend to be lower, and in some cases the ‘reservoir area’ per unit of output is greater.


It should not be forgotten that the choice may not be hydroelectricity or nothing, but hydroelectricity or some other form of power station. Despite the ‘penalties’ discussed previously, hydroelectricity scores relatively well in terms of many other criteria.

Its overall greenhouse gas emissions, including the construction of dams, are likely to be lower than those of rival fossil-fuelled generating systems. Current issues for hydropower include the question of methane emissions and the costing of long-term compensation for the people displaced by major new hydroelectric installations. Nevertheless, on the criteria discussed above, hydro appears amongst the least harmful sources of electricity.