Off-Grid Wind Power

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OFF GRID WIND POWER
Most off-grid wind turbine systems use a lower voltage turbine to directly feed batteries. A battery based inverter ramps this up to 230V to power appliances, often at low efficiency because of the voltages involved. This is inefficient for two reasons - voltage losses, and lack of optimisation of turbine output.
 
Voltage Losses
Lower turbine voltages require higher currents to transmit the same amount of power. Using low voltage on wind turbines greater than 3 kW results in large cable sizes being needed, higher temperatures in the generator, less reliability, and reduced efficiency.
 
Optimising of Turbine Output
On a grid tie system, wind turbine output is optimised by modern inverters which are capable of gradually loading the power taken from the turbine as its speed increases (referred to as power point tracking). The relationship between power available, and revs, 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. This particularly affects low wind speed production, which is critical for continuity of supply in off-grid sites.
 
Systems up to 3 kW
For systems up to 3 kW, we can provide a 48V MPPT charge controller which takes voltages in the range of 48V to 200V DC from the wind turbine, and converts this into 48V output for the batteries, with full charge control functionality. This uses the MidNite Classic Charge Controller and has specifically been designed with our Kestrel range of Wind turbines
This system may be particularly cost effective where power supplied to an off-grid site is required at 48V DC only, i.e. no demand for 230V AC.
 
Wind Systems above 3 kW
For wind turbines above 3 kW, we use highly efficient Power One high voltage grid tied inverters which supply power to a synthetic grid.
To manage the battery charging process, we use a microprocessor based controller which is programmed to manage both inverters and to ensure prolonged battery life.
The controller can also provide data logging, can start up a backup generator when required, for remote sites we can provide SMS alarms or internet connectivity.
This system has the advantage of optimising output from the turbine. Any wind power consumed at time of use does not need to go through the battery and can be supplied at efficiencies of up to 96% directly from the grid tied inverter. This system also has the distinct advantage of being eligible for Feed-in Tariff Schemes, even if the installation is entirely off the grid, i.e. no utility connection.
 
Battery Charge Management
Our off-grid management systems will monitor voltage, battery temperature, and charge / discharge current. This is by far the best method of ensuring reliable battery life in off-grid systems.
 
Solar PV Integration
The controller can also be programmed to manage solar photovoltaic panels should they be incorporated into the system.
 
Generator Switch –on Time.
We have a system for testing battery voltage - vs. - current at various states of charge so our micro-processor can determine when a state of discharge of 50% or 80% has been reached.
 
Broad Range of Turbines Possible
Our off-grid solution is generic and can be used with any wind turbine system. It can be used to manage turbines up to 20Kw, with loads up to 36kw. Packages are based on turbine sizes up to 3 kW using 48V direct charging, or 5 kW, and 10 kW using multiple inverters above that level. Power output is in multiples of 3 kW. The system can work with either 24V DC or 48V DC.
 
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