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Grid-Tied vs. Off-Grid Systems   arrow

Off-Grid Renewable Energy Systems

A solar array or wind turbine used to power a home or business that does not have access to utility-provided electricity is termed an ‘off-grid’ system. Solar panels or wind turbines provide power to a battery bank (series of batteries wired together) that store power for use when the sun isn’t shining or wind isn’t blowing. The battery bank is enclosed in a box to prevent gas escape or any potential battery acid spills. The bank is controlled by a charge controller that prevents over-charging of batteries and low voltage cutoff when batteries are trying to operate at too low of a charge (shortening battery life).

Batteries typically used in off-grid renewable energy systems are lead-acid batteries (liquid vented and sealed) and alkaline batteries (nickel-cadmium and nickel-iron). Most renewable energy systems utilize lead-acid batteries (similar to those used in recreational vehicles, golf carts or marine applications) that are designed to handle frequent charging and discharging. Automotive batteries would not handle this ‘deep-cycling’ demanded of household electrical systems, as they are designed for large loads for short periods of time, with recharging happening quickly from the vehicle’s alternator. More recently, lithium-ion batteries have gained a foothold in the battery market since they are more energy dense, more resilient to excessive discharging and extreme temperatures, and have longer lifetimes than lead-acid batteries.

Grid-Tied Renewable Energy Systems

Solar or wind systems that are connected to an existing electrical utility are called ‘grid-tied’ systems. Grid-tied systems do not need to have batteries for storing energy. Instead, during periods of excess solar or wind electricity generation, the electric meter turns backwards. When electrical demands are greater than electricity generated by the solar array or wind turbine, the power grid supplies this demand. The customer only pays for electricity used beyond what is generated in a given month (net metering = total energy used – renewable energy generated). The grid serves as the energy storage for the solar array or wind turbine. One drawback to this type of system is that electricity is not available if the grid power is interrupted.

Grid-tied systems can incorporate a battery-backup system for critical electrical loads. These grid-tied, battery backup systems will provide power for backed-up electrical loads, but not for the general home or business in the event of a power failure. These types of systems can use a battery charger that can recharge the batteries from the power grid once the grid power is restored. This type of system may be useful in areas where grid power failure is frequent or reliable power is critical (vaccination storage, for example).

Last updated: October 5, 2017 at 16:55 pm