New Energy-Battery Bank

A visit through the various major components of the Wind Turbine system has us following the cables and wires to power storage. What will we learn here?

A recap of the various parts started with the hub, rotors and the nacelle with the direct drive generator and rectifier, wind physics , wind measurement tools and the wires and cables for delivery of the new energy power source. These are the outdoor components that can be seen (depending if wires are not buried) and may look mighty mysterious or fancy schmancy.

The load analysis, load growth and choice of the wind turbine with properly measured energy output along with the accompanying cables and wires. Combination of this information will now determine the battery bank size, necessary and critical for power storage. As the wind turbines rotate even in gentle winds, it is generating energy.

A Hybrid system is the use of both a PV (PhotoVoltaic) array and a wind turbine. The reasoning for this is to maintain a electrical power supply for the ‘days of autonomy’ referring to lack of sunlight or wind. Others will also add a diesel or gas generator for that extra sense of security.

Sizing the battery bank will require specific steps are taken to ensure there will be no disruption to maintaining the flow of electrical energy to your home. They are as follows;

Charging/Discharge

– Depth of Charge (DOD) , refers to the amount of charge capacity removed from a fully charged cell or battery. Ensure the batteries are charged regularly aka ‘cycling’ and if done when batteries are at 70% level it is known as shallow cycling.

– State of Charge (SOC), the available charge capacity remaining. Do not let your batteries drain to 20% minimum (manufacturer minimum recommendation) as regular charging will extend the life and performance of the battery bank.

Days of Autonomy

Preparation in the event for days of no wind resource will require that a ‘number of reserve’ days be calculated. Residential is given 3-5 days and commercial is given 7-14 days. Greater days of autonomy will result in lower DOD that’s allowed.

Temperature Correction

Necessary in colder temperature zones and data is available by each battery manufacturer with recommendations.

Slow Discharge Factor

Refers to the rate of discharge of a battery by how long it takes to completely charge. Used to compensate against the manufacturer’s rate as they use a 8-20 hour discharge rate. A alternative energy system will discharge a battery more slowly therefore the actual capacity is greater than the manufacturers data. Following equation is used to determine the rate factor;

Average Period of DISCHARGE (Hours) = Days of Autonomy X 24 hours per day/ % DOD

Battery Capacity

Calculate the Amp hours (Ah) capacity of the complete battery bank. Refer to the equations which are also used to determine load analysis ;

Parallel /Series

Using a Series wiring will build up voltage levels. Parallel wiring increases the current or power. A combination of Series/Parallel provides a increase in voltage and Ah capacity.

Other factors to keep in mind with battery banks are the following ;

– Electrolyte in the batteries may freeze when exposed to extreme cold and cause leakage due to cracks in the outer casing. Demographic temperatures can be found through using the RETScreen (TM) software . It is best to store batteries away from the home and in a well-insulated and airy enclosure.

– Batteries are used in various vehicles, automobiles and marine transport.

– Hyrdrometer, used to test strength of electrolyte in battery. Low specific gravity means high potential for near freezing temperature.

– Hydro Caps, used to catalyze and neutralize hydrogen gases and convert into water. Cap has a dessicant inside the removable part.

Home wind turbine systems prefer to use the ‘deep cycle’ batteries as they are built to withstand a DOD of up to 80% repeatedly. Not true deep-cycle but more economical for average sized wind systems and have a 5-10 year life span dependant on how deep and numerous the discharge cycles and should only be used for off-grid electrical energy systems. Read related here –> here and there.

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