Microhydro is a great source of reliable electrical energy, but before you go out to buy a system, you should have a full understanding of its pros and cons. On the plus side, microhydro is probably the most cost-effective renewable energy system on the market. According to Scott Davis, it delivers "the best bang per buck.’’ Davis goes on to say, "Significant power can be generated with flows of two gallons per minute or from drops as small as two feet.’’ And, says Davis, "power can be delivered
in a cost-effective fashion a mile or more from where it is generated to where it is being used"
Microhydro, unlike almost all other renewable forms of energy (certainly wind and solar) often provides continuous power. That is to say, it provides electricity
day and night, night and day, 7 days a week, 365 days a year. Excess power can be stored in batteries or can be fed onto the utility grid, if its nearby. As Figure 10-12 shows, microhydro can do a much better job of meeting one’s needs. Solar and wind systems require either considerable
storage capacity or a connection to the electrical grid to supply continuous power. Microhydro sites owe their year-round performance in part to the fact that they can be easily winterized. Even though stream flows may slow down during the winter in snowy climates, small streams continue to offer reliable water flows because moving water doesn’t freeze very readily. Burying pipes underground below the frost line also helps to ensure a steady flow. Furthermore, notes Davis, microhydro can be integrated with pipelines delivering water to a house from a spring or stream located uphill from the building, small microhydro systems are inexpensive, too, costing from $2,000 to $10,000,
Yet another advantage of microhydro is that it is applicable to a variety of different conditions — from high head/low flow to low head/high flow and everything in between. The rule of thumb is, the more head, the less volume will be necessary to produce a given amount of power. The less head, the more volume you’ll need.
Like all systems, there are some disadvantages to microhydro systems. First off, very few suitable sites are available, say, in comparison to solar electric or wind energy sites. Second, microhydro systems require considerable knowledge. Third, not all sites that could be used for microhydro can be developed economically. Pipelines for a system, for instance, may be long and thus costly, Or they may be difficult to install. Fourth, diverting water from streams can alter flows and adversely affect living organisms that rely on the water. You need to exert extreme caution when installing a microhydro system. Be sure to consult with a qualified stream biologist. Fifth, microhydro systems may require permits from local government agencies, which can take time and may require a financial outlay on your part — notably, for engineering costs or the costs of a biologist to examine the site for potential impact. In British Columbia, one of my clients had two large streams flowing on either side of his property but could not tap into the flowing water because the province prohibits structures on streams to protect fish populations.
As with any system, you need to proceed carefully and cautiously — with as complete an understanding of the system as possible. If you are lucky enough to live by a stream or river and can legally tap into the power of the water running by your home, you could be graced with years of very inexpensive, clean, and renewable energy.