Sizing your Turbine

Wind turbine sizing can depend on a few criteria, and it’s very important to look at this carefully so as not to use the incorrect turbine. Factors like the average wind speed of the site, the voltage and number of batteries in the system as well as determining the number of blades necessary are critical to ensure optimal performance from the turbine and is tackled in more detail below:

Here are 4 checklist items when sizing your turbine:

1. Average Wind Speed of Site

Understanding the average wind conditions at a customer’s site is vital in sizing a turbine. In general, the turbines have a rated speed at 39km/h – meaning if you use a 1000W (1 kW) turbine as an example, a good 39km/h wind will get you the 1000W (1 kW) of power. But if that customer’s average wind speed is 20km/h, they’re going to get half of what they are expecting, so setting the expectation upfront will be your best option. Getting the customer to understand the power output is very important, as that way you avoid the customer thinking they’ve been ripped off. In general, a site with winds averaging around 15 – 20km/h is considered to be decent enough winds to produce power to charge batteries.

A great tool to use is Weatherspark.com, select the town or city nearest your customer, the wind results are about two thirds down the page. You can adjust the settings to give you °C, m/s or km/h at the top of the page, we use m/s for the specifications on all the turbines.

2. Voltage of the Battery System

The voltages of turbines and their controllers are matched to the battery voltage, in the same way, you can’t fit a 24V battery into your car that uses a 12V battery. The voltages must match – ie., a 12V turbine can only work with a 12V controller and a 12V battery system. Currently, the standards are 12V, 24 V and 48V.

48V battery system = 48V turbine and visa versa.
The exception to the rule is a customised controller that uses a charging system called “Buck and boost” to take power from a 48V turbine to a 36V battery system. Currently limited to putting a 2000W 48V turbine onto a 36V battery bank.

3. Battery System Size

Most systems will have more than one battery connected to their renewable energy system. The more batteries in the system, the larger your turbine power supply will need to be.
For example:

- a 48V system with 4 X 200ah batteries, all connected in series to get 48V – you will get away with a 700W 48V turbine.
- a 48V system with 8 X 200ah batteries, would have two sets of 4 batteries connected in series to get 48V, then paralleled together, a 700W turbine would work here, but we recommend from 900W and up
- A 48V system with 12 X 200ah batteries, would have three sets of 4 batteries connected in series to get 48V, then paralleled together, from 1KW and up.

4. Deciding on the number of blades

Modern blades are aerodynamically designed to capture the maximum energy from the wind. Additional blade sets on turbines mean more surface area, weight and torque to keep the rotor spinning when the wind dies down. Choosing between 3, 5 or 6 blade systems can be tricky as there are a few things to consider.
So here again, you’ll need to look at the average wind speeds in your customer’s area. As a general rule of thumb, 3 blade turbines can be used in areas where the wind is more prevalent, whereas the 5 blades are more suited to areas with less wind as they give more constant power at less rpm. The exception being the LX-range, as they only come in 5 blades. The LX-range are high-performance turbines and engineered to run 5 blades only. The patented blades are properly engineered so noise is minimized and performance is maximized in the 5 blade configuration.

High wind speed areas – Have gale-force winds often (coastal or mountain areas): Choose the 3 blade option, it’s all you’ll need.
Low wind speed areas – If it’s seldom extremely windy, then go for the 5 or 6 blade options.

3 Blade turbines: Less torque but more rpm – (higher winds)
5 Blade turbines: More torque but less rpm (lower winds)