How to Build Your Own Small-Scale Hydropower System
Building your own small-scale hydropower system can provide clean, renewable electricity for your home or community. With some planning and effort, you can harness the power of flowing water to generate electricity in an efficient and eco-friendly way.
Assessing the Hydropower Potential of Your Site
The first step is to evaluate whether your property has the potential for producing hydropower. Ideal sites have the following characteristics:
- A perennial stream or river with a dependable flow rate year-round. Seasonal streams may not provide enough flow in drier months.
- A vertical drop (head) of at least 2 meters from the water intake to the turbine. More head equals more power potential.
- Sufficient water flow rate. As a general rule, 1 cubic foot per second can produce roughly 1 kilowatt of electricity.
Ideally, you’ll want a site with at least 2 meters of head and 2-3 cubic feet per second of flow. Use maps, surveys, flow rate measurements and head calculations to quantify your site’s potential. Consulting with hydrology experts can also be very helpful.
Selecting a Turbine
There are two main types of turbines appropriate for small DIY hydropower systems:
Impulse turbines are driven by the velocity of water. Common impulse turbine designs include Pelton wheels and crossflow turbines.
Pelton wheel – Utilizes cup-like buckets attached to the wheel’s rim to capture water from one or more jets. Best for high heads (over 30 meters) and low flow rates.
Crossflow turbine – Also known as a Banki turbine. Water passes through a rectangular channel and contacts the angled blades twice. Good efficiency even for low heads (2 meters) and higher flow rates.
Reaction turbines generate power using the combined action of pressure and moving water. Common reaction turbine types are Francis turbines and propeller turbines.
Francis turbine – Water enters radially and contacts runner blades inside a spiral chamber. Good efficiency across a wide range of heads (5-250 meters) and flow rates. More complex design.
Propeller turbine – Modelled after ship propellers. Excellent for low heads (less than 10 meters) and higher flows. Very simple to construct.
Match the turbine design to the site head and flow rate. Impulse turbines are generally preferred for small DIY systems. I chose a crossflow turbine for my site with its low head and moderate flow rate.
Calculating Power Output
The two key factors determining power output are flow rate and head. This basic formula gives a rough estimate of potential power:
Power (kW) = Head (m) x Flow Rate (m3/s) x 0.1
For example, my site has:
- Head: 2.5 meters
- Flow Rate: 0.7 cubic meters per second
Power Potential = 2.5 x 0.7 x 0.1 = 0.175 kW or 175 Watts
The real output may be lower, around 60-70% efficiency. But this gives me a reasonable power production target.
The intake structure directs water from the stream into the supply pipeline leading to the turbine. Key intake design factors include:
- Submerged design to allow water to enter smoothly
- Coarse screening to filter out debris
- Flow control gate to regulate flow rate
- Waterproof sealed construction
I built my intake from concrete block inside a metal cage gabion filled with rock. The intake connects to a 15cm PVC pipe with a control valve and screen filter.
Pipeline and Penstock
The pipeline (also called a penstock) carries water from the intake to the turbine. The pipeline should be sized based on the expected flow rate. Important considerations include:
- 10-15% larger than calculated minimum diameter
- Watertight connections between segments
- Buried or anchored to prevent movement
- Gradual downhill slope with no low points
PVC and HDPE pipes are optimal materials. I used 100mm PVC pipe and situated my penstock along a ditch contour to eliminate low points.
Powerhouse and Turbine Installation
The powerhouse structure shelters the turbine and generator equipment. My small powerhouse was constructed from concrete block with the following features:
- House turbine near tailrace outlet for good water flow
- Access hatch large enough to maintain turbine
- Water-sealed entry points for penstock and tailrace
- Concrete foundation to stabilize equipment
I enlisted help to fabricate a custom crossflow turbine runner matched to my site parameters. The intake, penstock and powerhouse were sized to accommodate the turbine design flow rate.
Electrical System Components
Transforming the mechanical power into electricity requires several electrical system components:
- Generator – Converts rotational energy into electrical energy. Permanent magnet alternators are common for DIY systems.
- Controller – Regulates generator voltage and current output.
- Inverter – Converts generator power into grid-compatible AC electricity.
- Batteries – Provide energy storage for off-grid systems.
- Disconnects and wiring – Safety equipment and connections.
I used a 0-750W permanent magnet alternator, so the other electrical components were sized accordingly. Grid-tied systems require special synchronization inverters.
Monitoring Your System
To check your hydropower system health and productivity, install monitoring equipment:
- Flow meter – Measures water flow rate into the turbine. Helps identify any pipeline blockages.
- Pressure gauge – Monitors penstock intake pressure. Alerts you to drops that may indicate leaks.
- Volt meter – Checks generator and inverter voltages. Useful for diagnosing electrical issues.
- Production meter – Records kilowatt-hours generated. Verify the system is producing as much as expected.
I use a digital production meter connected to my control panel to monitor daily and monthly output. I also keep logs of flow rates and pressures.
Expect to perform regular maintenance tasks:
- Inspect intake screen – Clear any collected debris
- Check pipes and joints – Repair minor leaks before they worsen
- Verify turbine spin – Address any unexpected friction
- Check electrical connections – Tighten loose terminals
- Test pressures and flows – Diagnose variations from baseline
- Log power output – Track long-term performance
I do a short inspection most days and more thorough maintenance checks monthly. Keeping debris cleared from the intake screen is critical.
Building a small-scale hydropower system takes research, careful planning and hard work. But with a good site and proper system design, you can successfully harness the renewable power of water for decades to come. Pay attention to regular upkeep and your homemade hydropower plant will provide clean, low-cost electricity for years.