Asian Resources Int'l Limited MHG-T2 manual Selecting a Site, Measuring Gross Head

SELECTING A SITE

PowerPal is designed for use in a wide range of locations. There are two critical factors that influence power output – head and flow. Head is the vertical distance between the turbine and the water source (forebay), measured in meters. Flow is the amount of water that passes through the turbine at any instant, measured in litres per second (l/sec).

See Page 17 for detailed head, flow rate and output data for the three T2 models.

Measuring Gross Head

The gross head is the vertical height from where the water flow enters the penstock down to the level of the turbine. It is shown in the System Diagram. To measure this, use a tape measure and a clinometer or spirit level etc. A less accurate but useful alternative is to make your own level from a transparent tube half-filled with water. Attach this to the top of a 1m long stick and then point this horizontally at a point further up the slope as though it were a spirit level. By going to that point and repeating the process the total gross head can be measured – see the drawing below.

10m

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Measuring Gross Head:

Walk up the slope from where you wish to place the turbine to where the water source is. Or, do the reverse: walk down the slope from the water source to locate the best site for the turbine.

Another method is to use an accurate pressure gauge and a length of hose. Run a water-filled hose from the forebay to the turbine site and attach the pressure gauge to the bottom end. The pressure gauge shows 1.422 psi / meter of head e.g. 11.4 psi for a head of 8m to 24.2 psi for a head of 17m.

This head should be between 15 and 21 meters for the MHG-T2 model. If it is smaller then the power output will be reduced. If it is larger then your power output will be increased. While increased power output appears desirable, if the head is too large then the rotor will turn too fast and reduce the life of the bearings unless the spear valve is used to reduce flow.

Do not attempt to exceed the recommended head height.

PowerPal™ T2 Turgo 5