Wind Turbines – Grid-Tie With Battery Backup Vs Direct Grid-Tie Application

Eleanor Hanson

In a world of economic instability with rising energy cost and depletion of fossil fuels; many individuals seek the use of alternative energy sources, utilizing the “free” renewable sources, as advocated by individuals like T. Boone Pickens and future President Barrack Obama.

When contemplating the use of a grid-tied alternative energy source with the goals of greatest utility with minimal expense, the application of a hybrid Wind/Solar system with battery based backup satisfies both aims better than the direct grid-tie, battery less solutions currently available on the market. This is accomplished through three main points: efficiency, situational utility, and cost-benefit analysis.

First, we must fully understand the operational differences between the two options. Our hybrid Wind/Solar, battery based grid tie application involves utilizing the natural renewable resources of the wind and sun at a low voltage range, rectifies the current obtained in the charge controller, and then charges batteries that the inverter can pull from to feed back to the grid. Conversely, a direct grid tie wind turbine will feed into a resistance load and then pumps a very high voltage into the inverter to supply back to the grid. In summation, a direct grid tie unit will operate at very high voltages and feeds directly into the inverter, while a battery based system such as ours, operates at low voltages keeping the batteries fully charged for the inverter to draw from.

While many view the direct grid tie system as more simple than the battery based, after careful examination of the pros and cons, the simplicity is a moot point. Realize that the direct connect grid tie system must maintain a very high voltage range between 300v-600v. If the power generation of the direct grid-tie system does not fall in this range, the grid will not be receiving any power for buy-back. Conversely, a battery backed grid-tie system is much more efficient. By using the batteries as a draw source for the inverter, constant flow can be achieved to the grid. During low wind, or high wind, low voltage, or high voltage, a battery backed grid-tie system can constantly be selling power back to the power grid for buy back while the alternative can not.

When examining the situational utility of the two present grid-tie options, the battery backed grid-tie application satisfies a greater utility. First, only the battery backed system can provide energy independence for remote sites. Many customers choose to explore the hybrid solution, combining wind power and solar panels. In a direct grid-tie application, the customer would need two inverters, one for each power source. A battery backed grid-tie system would accumulate all of the energy sources into the batteries for a single inverter to draw from. Also, in the case of grid-failure, only the battery backed grid-tie system would function. If the grid failed, so would a direct grid-tie system. The direct grid-tie inverter is relatively new on the market and there are many issues that must be fully tested to function properly in order to achieve higher efficiency and avoid catastrophic problems.

The final determining factor comes down to mere cost-benefit analysis. Arguably, if the same end result can be achieved by both systems, why is it logical to pay much more for the direct grid-tie application? A battery backed grid-tie system is far less expensive than a direct grid-tie system.

After covering the above stated issues, it is an easy choice to opt for the battery backed grid-tie application. In review, the battery backed grid-tie system allows for a much greater utility and flexibility at a much lower cost to the customer than a direct grid-tie system.

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