Hydro power has been a
useful source of power for many centuries and was, with wind, the
main power source prior to the industrial revolution. However,
the same constraints that limited its application then still apply
today, notably the need for access to a suitable flow of water; more
often than not, this does not coincide with the location of power
demand. One major benefit of this technology compared with
other renewable sources, however, is that it produces a much more
consistent output, which can be further enhanced by simple energy
storage (in the form of water). Indeed, at the micro power
level the small proportion of water off-take from a weir etc. is
often still well above the minimum flow requirements for the device
to maintain its designed power output, so that power output can be
two key parameters which determine the power output are the "head"
(that is the height difference between water inlet and outlet) and
the "flow" (volume of water); power output is directly proportional to both. In order to achieve an economically
viable installation, it is therefore necessary to have either a high
head or a high flow or, ideally, both.
The economics are determined by the
water resource as well as the local conditions which influence the
construction costs of the generation equipment and associated
infrastructure. Each site needs to be considered on its own
merits, which leads to high implementation costs and it is thus a
difficult technology for which to achieve economies of scale.
This is not helped by the complex legal and other processes which
must be complied with, prior to installation, further adding to the
investment risk as significant costs must be incurred with no
certainty of a successful outcome.
It can be seen from the above that it
is not easy to establish "typical" installation costs, but it is
unlikely that paybacks of less than 10 years can be achieved except
for the best locations.