Electric Water Pumping using a Wind Generator
One of the major technologies that allowed settling of the West was the invention of the
windmill for pumping water. Whenever the wind blew strong enough, water was
pumped to a tank for use and storage. Those windmills have been largely been replaced
with electric motors, either run off the grid or a local generator.
With the ever increasing cost of grid electricity (mostly from non-renewable sources), the
use of renewable energy in the form of wind power is becoming a viable alternative,
especially in rural areas for domestic, farm, or ranch well pumps. There are some basic
concerns that need to be addressed before installing a system.
Given the intent is to continue to use the existing pump and motor, once must size the
wind generator appropriately. Although pumps and motors are both rated in horsepower,
the horsepower of the motor is approximately twice that of the driven pump (e.g., most
pumps are around 50% efficiency), so one must make sure one knows the horsepower of
the motor. Starting current is of concern, so one should still tie the output of the wind
generator to the grid; much less costly to pay the grid for the short term starting current
than to build a significantly larger wind generator to supply the starting current. The
efficiency of the transmission lines, inverters, transformers, etc. is around 80%. Of
course, the wind rarely blows at the optimal speed for maximum output, so one must
consider the expected output of the wind generator, not the theoretical maximum for an
entire day.
The wind generator should be a grid-tie system not using batteries for back-up or storage.
Even in rural areas, the grid has high reliability so there is no need to waste efficiency on
a battery storage system. Preferably a “net-metering” scheme can be used (at least to
cover annual electricity usage), but a buy-sell contract can work (requires a special
meter). In buy-sell, one buys at the standard rate, but sells at “avoided-cost”. Even if
using net-metering for privat