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DC Electrical Balance of Plant

Over a hundred years ago, with the United States on the brink of Electrification two of the greatest minds in the history of electrical engineering were dueling over an often “taken for granted” characteristic of electricity. The story of Edison and Tesla; DC and AC; General Electric and Westinghouse is an interesting foundation from which modern electrical systems evolved. In the long run Tesla’s AC current was adopted. One of the more appealing characteristics of Alternating Current (AC) is that the losses in the conductors are significantly less as compared to Direct Current (DC)since AC can easily be transformed to higher voltages.
Here is an easier way to think about it. In industry, sizing pipe for water or heated air or transportation of fluid in general is a complex process. Many times minimizing losses means making a pipe larger allowing for more flow. DC works the same way. In order to minimize the losses in the line thicker conductors are used. Thicker in this case generally means more material, more copper, and more expensive.
Well if we settled the debate regarding AC and DC, why bring it up again? Photovoltaics, by process, produce DC power. This means that before utilization in a house or building the DC power must go through an inverter turning it into AC power. DC safety and regulations specifically pertaining to the components used with photovoltaic systems may be intimidating for some electricians who have spent the majority of their careers working with AC standards.
After running through some of the NEC standards for the DC portion of the electrical system, the various derating factors and allowances are fairly complex. One of the answers that the solar industry is providing for this potential barrier of installation is back of the panel inverters or micro inverters. With this piece of technology most of the DC aspect can be cut out, losses in the line and cost of balance of plant can be minimized as well.
In the meantime, PV will have to go on with the potentially complex installation regulations. Tesla’s ideas may have been ideal for machines and distribution, but to this day we are dealing with DC’s struggle to provide its share of power.

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