In most systems, a steel shaft connects the turbine to the generator. This shaft com pies the turbine with the generator so that rotation of the turbines runner translates into rotation within the generator, “The most efficient and reliable drive system involves a direct 1:1 coupling between the turbine and generator," notes New. But this is not possible for all sites. In some cases, especially when AC generators are used, it may be necessary to “adjust the transfer ratio so that both the turbine and generator run at their optimum (but different)
speeds," he adds. This is achieved through gears, chains, or belts, Belt systems are the most popular because they are the least expensive. Unfortunately, more complex drive systems increase the cost of a system and will invariably increase maintenance requirements.
For those who need lots of power intermittently (which is most of us) a battery system or a grid-connected system may be advisable.
Most microhydro systems use deep – cycle lead acid batteries. Never, never, never use automobile batteries. They cant handle the deep discharging. Batteries for renewable energy systems were covered at length in Chapter 8, but 111 point out one important fact here. As a general rule, microhydro systems require much smaller, and thus
much less expensive, battery banks than solar electric or wind electric systems* Thats because these systems only need to provide electricity for occasional heavy power usages and power surges* You’re not trying to store power for three to four days of cloudy weather, as in the case of a PV system, or windless days, in the case of a wind energy system* The battery bank is also smaller because of rapid recharge* That is, if the batteries are drawn down during the day, they’re usually recharged by evening* Occasional high output and rapid recharge not only means fewer batteries, it also means a longer battery life, for reasons explained in Chapter 8*