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The following is an excerpt from a case study from the Energy Alternatives Microhydro Online Course.
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 Ch1 - Welcome to Microhydro
 Ch2 - Getting the service you want
 Ch3 - Determining your power potential
 Ch4 - About battery-charging systems
 Ch5 - About AC systems
 Ch6 - Plumbing
 Ch7 - Case studies
  •
  •
  •
 Ch8 - Regulations and incentives

CASE STUDY: A Simple Battery Charging System

The Problem:

A family of five living in an off-grid house wanted lights, music and modern conveniences, about a level 3 on the Capacity and Consumption self-rating scales.  One challenge of their location was winter freezing, where plumbing is routinely buried up to 6 feet deep.  They were hoping to avoid the bother, expense and permanence of such a “civil engineering” project.  An advantage to their site was lots of water, the creek flowed at hundreds of US gpm, even at  low water. 

The Solution:

Turbine 4-inch Turgo “Stream Engine” from Energy Systems and Designs
Pipe length and material 600 feet of 2-inch poly
Water volume available  lots – hundreds of gpm
Head   100 feet
Static pressure 43 psi
Net pressure 15 psi
flow rate   100 US gpm
Jet size 1 inch
Power output  150 kWhrs/month (208 continuous watts)
Capacity rating 3
Consumption rating 3

The major construction consideration for microhydro in cold climates is the protection of the pipe from freezing temperature. Burying below the frost line is the usual method, giving excellent mechanical protection as well. However, in rugged terrain, this can be a formidable task.

Two-inch poly is terribly rugged.  Here, the owner laid the pipe right in the creek bed to protect from freezing. 

This is not usually recommended, as holes can become abraded into the pipe over time as it rubs against the rocks.  However, this system has run for a few of winters without problem, so there you go.

A pressure gauge shows that there is about 15 psi, when the water is flowing. Since the owner told us that a one-inch jet is used, the water flow is about 100 US gpm through the Stream Engine. The system delivers over 200 continuous watts to the batteries, a few hundred feet up the steep slope.

This illustrates that electrical generation can be both pretty casual and quite powerful. Actually, this system has a jet that is too big for the length of the pipe used. More water is being used than is strictly necessary, meaning that the pressure is lower than it could be. However, since there is lots of water in the creek, and lots of power in the batteries for the loads that are being used, it just wasn'’t worth resizing the jet, says the owner. Casual.


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