Residential solar panels get all of the press for a simple reason — everyone gets sunlight. But there’s an equally green method of power generation that doesn’t get as much attention: the water wheel generator. If you happen to live on a rural plot of land that features a river or stream, you might be able to partially power your home with hydroelectric power.
Thinking of building your own mini Hoover Dam in your backyard? Here’s what you should know before you get started.
How A Water Wheel Generator Works
Water wheel generators essentially work the same way as wind turbines, but they use flowing water instead of blowing wind. The water passes through the water wheel, causing it to spin. The axle of the wheel is connected to a dynamo that turns that kinetic energy into electricity that your home can use.
Types Of Water Wheels
There are several different types of water wheels, but you’ll usually find one of three powering a residential home. Which one you choose will depend on your water source, how complicated you want your water wheel generator to be, and your energy needs.
The undershot wheel is the simplest and oldest type of wheel. Like the name implies, it works simply by allowing water to flow under the wheel. It’s not very efficient at turning water flow into energy, but its ease of construction and use makes it the most popular.
In a breastshot wheel, water hits the wheel around its center. These wheels are more efficient than undershot wheels because they partially use the power of gravity to move.
Overshot wheels use water flowing from the top of the wheel. While this system is more complicated to build, it is much more efficient. Since gravity pulls the water all the way down the length of the wheel, it’s able to make the most of every drop. This means that an overshot wheel can generate a substantial amount of power if it uses a waterway that isn’t very fast or powerful.
From an engineering standpoint, overshot wheels are one of the most complicated to build. They often require the construction of a dam, millpond, and waterways.
How Much Water Can It Generate?
Power generation depends on several factors, including the power of the stream and the size of your wheel or turbine.
To get a rough estimate, you can use this formula: 0.004 x Q x V x H x C = kilowatts generated.
Here’s a breakdown of what that formula means:
- “V” is velocity of the water stream per second
- “Q” is the weight of the water (volume per second x capacity of the buckets)
- “H” is the height difference between the head race (where the water enters the wheel) and the trail race (where the water exits the wheel)
- “C” is the efficiency constant
The efficiency constant refers to how efficiently your wheel turns water into energy. In the 18th century, English engineer John Smeaton calculated that undershot water wheels are about 22%efficient, while overshot water wheels are 63%efficient. If you’re unsure about your efficiency constant, you can get an approximate figure by making “C” equal 50%.
Building The Water Wheel
If you’re good with tools and have a DIY streak, you can build your own. You can buy plans, but you can also build your wheel using freely available online plans. You can buy the hardware you need at any hardware store, and the kinetic dynamo can be purchased online.
If you’re lucky, there might happen to be a water wheel craftsman in your area. For example, Spencer Boyd of waterwheelplace.com lives outside of the metropolitan area of Atlanta, Georgia and constructs custom-made water wheels. You can even get one shipped to you.
However, you can also hire a local handyman who is skilled with wood to build one for you. Asking someone who’s never built a water wheel is always a bit of a gamble, but since they’re simply built of wood, someone who is experienced with construction should be able to do a good job.