As we continue to look at alternative energy sources for the home, we get to the fourth musketeer: hydro power. Unlike access to solar, wind, and geothermal, hydro power isn’t as easy to come by. However, if you happen to have a river or stream running through your property that features a drop in elevation, you may well be able to tap its inherent energy. Folks who live on a boat or a floating home have unlimited power right underneath them so long as the current is solid.
Using water to generate electricity can be accomplished in a couple of different ways, but there are two main considerations that determine whether or not it will work — the vertical drop and the flow of the river or stream. Also, you need to check with local governance to ensure that plugging into the water source is allowed. As long as you aren’t diverting or damming the tributary in such a way that damages the surrounding ecosytem, chances are fairly good that you’re safe.
The drop, measured in feet, is calculated along a course – from the highest point of the stream to the lowest – that will readily accept a diversion pipe. You can use a laser, transit, or water level to get the job done. Sadly, flat streams don’t do much in the way of power generating.
The stream’s flow is measured in gallons per minute (GPM). Perhaps the simplest method of calculation is to time how long it takes to fill a five-gallon bucket. Another, more complicated formula can be found in The Residential Hydro Power Book by Keith Ritter.
Two main residential hydro systems dominate the market. Pelton wheel turbines and submersible propeller fit different scenarios and provide different outcomes. If yours is a low-flow stream, the pelton wheel power generator is the way to go. Here, water channels through a pipe into a series of cups which, in turn, spin a wheel that powers a turbine that generates the electricity. Phew! With a cost falling either side of $1,000, pelton wheels can provide as much as 36 KWh of energy a day.
For a fast-running tributary that runs between six and nine miles per hour, a submersible propeller model might be a better choice so long as you have at least one foot of water depth. The best part of a propeller system is that no modifications need be made to the river. The price is roughly the same as the pelton wheel, but the output is lower – topping out around 2.5 Kwh a day. Propeller-style systems are great for the aforementioned water-dwelling residents.
Historically, hydro power systems have been off-grid installations. However, like solar and wind, they can be tied to your existing electrical grid as an eco add-on. Unlike solar and wind (but akin to geothermal), hydro earns bonus points for being a continuous source of power… unless, of course, the creek runs dry. It is also, generally speaking, the more economical choice in the realm of alternative energy, especially once the state and federal tax incentives are factored in.
