Grid-Tie energy systems cut power bills by using renewable energy to power homes and businesses instead of completely relying on a utility company's grid-supplied electricity.

Renewable energy is most often supplied by a solar array, or an assembly of solar panels, and less often by a wind turbine or micro-hydro turbine. All systems require installation including wiring connections and some degree of maintenance. None can store energy on their own.

A grid-tie system can be battery-less or have a back-up bank of batteries to store energy until needed. A battery grid-tie system can sell power back to the grid. With a battery-less system, once the grid-supplied power goes out due to a storm, damage to the power lines, or utility malfunction, the user has no power for normal loads such as lights, furnace fans, or refrigerators, loads which could be powered by batteries for a limited amount of time. Battery back-up will maintain comfort and circuits powering important loads.

There is a difference in cost between a battery-less grid-tie system and one with battery back-up. A battery-less system requires an inverter and a solar array or other renewable power source. In addition to these two components, a battery grid-tie system requires several batteries, a charge controller for efficient battery recharging, breaker panels, circuit breakers, and enclosures to house the components. Each system will have installation expenses. A grid-tie system with battery back-up adds as little as 12% cost over a stand-alone grid-tie system.

Is the availability of battery power worth the extra expense when the grid goes down?

Each user must answer this question independently. Consider: If your power goes out, do you want to be wandering around your home using flashlights and candles when a battery bank could provide power and the security that comes with it for days on end? Or power a refrigerator to prevent food spoilage?

Energy loses some efficiency as it moves from its source to the loads it powers. These losses are based on the distance traveled, the size of wires the current travels on, the loads themselves, resistance, and, in the case of grid-tie battery-backup systems, the batteries. Batteries lose some of their charge simply due to the nature of their chemical electrolyte solution, which allows some current to pass through even when there is no draw from a load. Normal recharging keeps this drain to a minimum and maintains battery reliability.

OutBack Power Systems' Grid-Interactive PS1 combines all the needed power conversion components for a renewable energy system in one ready-to-install package. With OutBack's GTFX and GVFX Series Inverter/Chargers and MX60 Charge Controller, the battery bank (which is not supplied by OutBack, but readily available through renewable energy dealers and installers) is recharged automatically. Depending on the battery type and manufacturer's recommendations, a user could have almost no maintenance tasks.

Properly maintained batteries can comfortably last ten years before requiring replacement.

According to the U.S. Department of Energy, the typical American household consumes about 10,000 kilowatt (kWh) hours per year. OutBack recommends a 48-volt Group 31 battery bank for the PS1 which provides approximately 4 kWh* of back-up electricity in the event grid-supplied power goes out.

How does this translate into working power for a homeowner?

A 100-watt light bulb continuously on consumes one kWh of electricity every ten hours. Modern refrigerators can consume as little as one kWh a day. With most power outages only lasting a few hours, the PS1's battery bank can keep your vital loads running until grid-supplied power is available again.

*based on 80% depth of discharge

BATTERIES

A battery is made of metal plates surrounded by a solution of water and sulfuric acid. Chemical reactions with the metals produce an electrical current. Batteries are fully charged during manufacturing. This stored electricity in the form of direct current (DC) energy can be used when grid-supplied power is not available.

Batteries are not 100% efficient, but maintained batteries are a highly reliable source of energy. OutBack Power Systems recommends sealed AGM batteries for the Grid-Interactive PS1. Sealed AGM batteries essentially require no maintenance other than occasional recharging, which is done automatically by the PS1.

A battery grid-tie system offers all the benefits of selling electricity back to the local utility and the advantages of back-up power when that same utility is down. This is the best of both worlds for renewable energy users.

OutBack Power Systems, Inc. is a global designer and manufacturer of cutting edge power conversion solutions that provide reliable electric power for renewable energy, mobile and back-up power applications. With decades of power conversion design and equipment installation experience, we share a passion and vision for a new era of power conversion equipment performance, ease-of-use, and standardization.