Saturday, October 6, 2012

Components: Turbines

The towering water wheel driving the old mill’s grinding stones creates a romantic image, but it is too slow and ponderous to efficiently convert water power to electric power. For example, a 5 foot diameter wheel that is 16" wide will generate only 300 watts or less. A compact turbine and generator is a better choice unless you are renovating an old mill site. Hydroelectric plants are available in capacities ranging from 1/2 KW to 12 KW.

A reaction turbine, either the Francis type or propeller wheel type, is turned by a mass of water falling through a duct encasing a wheel. Reaction-type generators are good choices if you have ample water supply but a low head. A reaction wheel is subject to greater friction losses than an impulse wheel; however, it has greater flexibility in installation.

An impulse (Pelton) turbine turns by the velocity of a jet of water striking the turbine’s wheel cups and can operate on as little as 1.5 cfm of water. In order to be most effective, a head of at least 50’ is required.

The type of facility you wish to provide with electrical service will largely determine whether you use an Alternating or Direct-Current generator. Lights and the universal motors that operate small appliances and tools will operate on DC. Larger motors, TV’s and many appliances require AC to operate. Alternating Current may be transmitted greater distances and on smaller wires than is possible with Direct Current; however, an AC installation does require an extra investment in governing equipment.

Direct Current generators are usually less expensive than AC generators but they do require expensive inverters to convert to AC. The potential of storing DC in batteries during low-usage periods and at times of uneven water flow is a compensation of such a system.

No comments:

Post a Comment