Motors
as generators for Micro-Hydro power - Nigel Smith This
is a guide to the use of induction motors for electricity generation
in remote locations. It is written as a practical handbook for engineers
and technicians involved in designing and installing small water
power schemes for isolated houses and communities. The manual arose
out of the practical experience of manufactures and installers of
induction generator units working in village locations in a number
of countries.
A
micro hydro plant is below 100kW. Improvements in small
turbine and generator technology mean that micro hydro schemes
are an attractive means of producing electricity. Useful power
may be produced from even a small stream. The likely range is
from a few hundred watts (possibly for use with batteries) for
domestic schemes, to a minimum 25kW for commercial schemes.
Hydro
power requires the source to be relatively close to the site
of power usage, or to a suitable grid connection. Hydro
systems can be connected to the main electricity grid, or as a
part of a stand-alone (off-grid) power system. In a grid
connected system, any electricity generated in excess of
consumption on site can be sold to electricity companies.
In
an off-grid hydro system, electricity can be supplied directly
to the devices powered, or via a battery bank and inverter set
up. Allowances should be made for any seasonal variations in
water flow, which can affect the amount of electricity
delivered to the system i.e. having a back up power system.
It
is possible for single households with a mains connection
located near a hydro source to install a micro hydro system.
They can go 'off the grid' entirely, or stay connected and
sell excess electricity to the grid. The capital cost is high,
but the prospect of zero or even negative electricity bills
may tempt you!
Provided
the resource is there, community hydro projects can also be a
viable proposition. Potentially, there are great benefits in
clubbing together to increase buying power or sharing
expertise - although the work involved should not be
underestimated.
Energy available in a body
of water depends on the amount of water flowing per second,
and the height (or head) that the water falls. The scheme's
actual output will depend on how efficiently it converts the
power of the water into electrical power (maximum efficiencies
of over 90% are possible, but for small systems 50% is more
realistic). Hydro electric systems are generally divided into
2 categories, low and high head.
This will depend on the
resource available and your energy needs. For houses with no
mains connection, but with access to a micro-hydro site, a
good hydro system can generate a steady, more reliable
electricity supply than other renewable technologies at a
lower cost. Total system costs can still be high, but often
less than the cost of a grid connection, and with no
electricity bills to follow. Note that in off-grid
applications the power is used for lighting and electrical
appliances, however space and water heating can be supplied
when available power exceeds demand.