Renewable Energy Solutions

What is a horsepower?–How the Carthaginians manufactured
horsepower–All that goes up must come down–How the sun lifts
water up for us to use–Water the ideal power for generating
electricity–The weir–Table for estimating flow of streams, with a
weir–Another method of measuring–Figuring water horsepower–The
size of the wheel–What head is required–Quantity of water
necessary.

If a man were off in the woods and needed a horsepower of energy to
work for him, he could generate it by lifting 550 pounds of stone or
wood, or whatnot, one foot off the ground, and letting it fall back in
the space of one second. As a man possesses capacity for work equal to
one-fifth horsepower, it would take him five seconds to do the work of
lifting the weight up that the weight itself accomplished in falling
down. All that goes up must come down; and by a nice balance of
physical laws, a falling body hits the ground with precisely the same
force as is required to lift it to the height from which it falls.

The Carthaginians, and other ancients (who were deep in the woods as
regards mechanical knowledge) had their slaves carry huge stones to
the top of the city wall; and the stones were placed in convenient
positions to be tipped over on the heads of any besieging army that
happened along. Thus by concentrating the energy of many slaves in one
batch of stones, the warriors of that day were enabled to deliver
“horsepower” in one mass where it would do the most good. The farmer
who makes use of the energy of falling water to generate electricity
for light, heat, and power does the same thing–he makes use of the
capacity for work stored in water in being lifted to a certain height.
As in the case of the gasoline engine, which burns 14 pounds of air
for every pound of gasoline, the engineer of the water-power plant
does not have to concern himself with the question of how this
natural source of energy happened to be in a handy place for him to
make use of it.

The sun, shining on the ocean, and turning water into vapor by its
heat has already lifted it up for him. This vapor floating in the air
and blown about by winds, becomes chilled from one cause or another,
gives up its heat, turns back into water, and falls as rain. This
rain, falling on land five, ten, a hundred, a thousand, or ten
thousand feet above the sea level, begins to run back to the sea,
picking out the easiest road and cutting a channel that we call a
brook, a stream, or a river. Our farm lands are covered to an average
depth of about three feet a year with water, every gallon of which has
stored in it the energy expended by the heat of the sun in lifting it
to the height where it is found.

The farmer, prospecting on his land for water-power, locates a spot on
a stream which he calls Supply; and another spot a few feet down hill
near the same stream, which he calls Power. Every gallon of water that
falls between these two points, and is made to escape through the
revolving blades of a water wheel is capable of work in terms of
foot-pounds–an amount of work that is directly proportional to the
_quantity_ of water, and to the _distance_ in feet which it falls to
reach the wheel–_pounds_ and _feet_.

Next We will Look At the Efficient Water Wheel