Off-Grid Power Manager for Wind or Solar Hybrid Systems
Most off-grid wind turbine systems require a lower voltage turbine to directly feed batteries, usually at 48-56V. A battery based inverter ramps this up to 230V to power appliances, often at low efficiency because of the voltages involved. We can supply the inverters and other components for this system, but for wind turbines, this is inefficient for two reasons – lack of optimisation of turbine output and voltage losses.
Optimising of Turbine Output – On a grid tie system, wind turbine output is optimised by inverters capable of gradually loading the power taken from the turbine as the rotor speed increases (referred to as power point tracking). The relationship between power available and RPM is a curve which can be programmed into the inverter.
Most battery based systems operate much more crudely. When the turbine voltage is below battery voltage, no power will be generated. Once it gets above battery voltage, the batteries control the voltage and loading of the turbine in a manner that cannot be controlled, resulting in reduced output from the blades which are not operating at their optimum speed.
Voltage Losses – Lower turbine voltages require higher currents to transmit the same amount of power. Using low voltage results in larger cable sizes being needed, higher temperatures in the generator, less reliability, and reduced efficiency.
Voltsys developed a unique solution which allows power point tracking, at the same time allowing battery charging to be optimised. Using our microprocessor based controller and interfaces, we are able to manage battery charging to extend useful battery life, including temperature compensated battery management.
The controller can also provide data logging onto a standard SD card, can start up a backup generator when required, and for remote sites can provide SMS alarms or internet connectivity.
Solar PV Integration – The controller has been programmed to manage solar photovoltaic panels should they be required as part of the system.
Diesel Generator Start-up – Most systems switch on the backup generator at a pre-determined voltage (usually 47V). We have a system for more accurately assessing the state of charge to prevent over use of the generator and/or excess battery drain.
Broad Range of Turbines Possible
The off-grid solution is generic and can be used with any wind turbine system, eliminating the need for turbine companies to produce a separate turbine for low voltage systems. Using multiple inverters, it can be used to manage turbines up to 20Kw, with loads up to 36kw. The system can work with either 24V DC or 48V DC.
Battery Packs – We need to design battery packs to match the requirements of the system, and each system is then custom designed with variables programmed into the controller.
Off-grid solutions are a specialised area requiring a number of unique components which we can supply. These include DC cabling, DC circuit breakers, custom made controllers, AGM wet cell batteries and dump loads (to prevent over-charging of batteries).