An open source software tool for modeling and designing wind electric systems with direct battery connection
WindSYS is a modeling tool for wind electric systems with direct connection to battery. Providing an easy to use interface, it simulates a system consisting of a small wind turbine with rotor diameter from 1.2m to 4.2m which is connected to a 24 or 48 Volt battery bank. It provides information about the mechanical and electrical behavior of the system and determines the maximum annual energy production by optimizing the AC cable run selection as well as the AFPM generator’s airgap.
In order to calculate the power delivered to the batteries, the wind system is modeled and its operation is simulated for a range of cable resistance values and a range of rotational speeds. The mathematical description of the aerodymanic curves, which relate the rotational speed of the blades, the wind speed and the aerodynamic power absorbed by the generator, are determined from the characteristics of the generator, environmental variables and wind power absorption modeling. Correlating the mechanical power of the generator with the aerodynamic power, the overall system behavior is defined, thus specifying maximum annual energy production at a specific cable resistance value.
Taking into account the distance between the wind generator installation and the battery bank as well as the cable cost, an optimal cable diameter can be determined for a given distance with values between 10m and 150m, attempting a weighed compromise between the two criteria, maximum annual energy production and cable cost. WindSys also provides the capability for a custom cable diameter to be selected, simulating a wind system installation and providing comparative information for the electrical and mechanical behavior of the system.
Finally, WindSys can combine the above functions and visualize through 3D graphs the operation of the system, as far as maximum annual energy production, cable cost and cable sizes are concerned, for a range of generator airgaps, distances and cable sizes, enabling a feature full system overview, useful for both scientific and installation purposes.
The results of the simulation’s validation, which has been feasible through a series of experiments both at the NTUA small wind turbine test site and at the NTUA lab facilities, are also presented as part of the tool.