Improving ROI in Solar PV with NEXTEK's Direct Coupling Technology

Nextek has experimentally verified the substantial improvement in efficiency of a solar PV system equipped with a Nextek Power Module. Nextek's Direct Coupling technology eliminates the DC to AC inverter which is required in standard solar PV systems and which results in losses of power produced by the Solar array and less power available to loads. With the Nextek Power Module, the same number of solar cells produces more power or fewer solar cells are required to produce the same amount of power. Either way Nextek customers realize a dramatic acceleration of the payback of PV-powered building applications.

Two identical sets of solar arrays and electric loads were setup side-by-side. One set was connected with a best-selling high quality inverter and one set was connected with Nextek's Direct Coupling technology. Both solar PV systems were carefully monitored by making measurements using acurately calibrated true-power meters to read both instantaneous and integrated (accumulated) watt-hours. The object was to measure the amount of effective solar PV array energy reaching the loads through the two systems under the same solar irradiation conditions. A series of tests were performed so that a variety of weather conditions could be taken into consideration.

The viability of Solar PV systems using Nextek's technology is manifest because most commercial and industrial building lighting loads are intrinsically DC by virtue of the use of electronic ballast and converters built into all standard electronic ballast are required to convert the AC back to DC. In other Solar PV systems an inverter is required to invert the photovoltaically produced DC to AC (60 Hz ). Energy is always lost due to the inherent inefficiency of inverters. In conditions of lower solar irradiation such as clouds, the early morning and late afternoon sun there is not enough solar electric to operate an inverter and the solar power is totally wasted.

The advantage of Nextek Solar PV system technology over standard practices is that the Nextek power module directly couples the photovoltaic DC source to the building lighting load. With the Nextek system all available PV is first absorbed into the load, with the remaining power requirement supplemented by the Nextek power module's high efficiency AC to DC converter. Solar energy and building AC are continuously blended to provide a highly regulated power source to the load. By eliminating the need for an inverter the Nextek approach dramatically reduces intervening losses when the sun is shining and in conditions of lower solar irradiation the solar power is still fully utilized.

The following graphs illustrate the dramatic benefits of eliminating inversion losses with the Nextek system and ability to collect and deliver PV energy to the load when compared to an inverter based system. In summary, these graphs exhibit Nextek's effectiveness in displacing far more grid power than conventional practice.

DISCLAIMER: These tests were conducted by Nextek's Engineering Research division at Nextek's facility, and were not conducted by an independent test firm. Data was collected under a variety of weather conditions using calibrated power meters for gathering both instantaneous and integrated (accumulated) watt-hours.

Solar watt/hrs Collected - Daily Totals
Date       Inverter   Nextek   Conditions             Improvement      %
8/29/01    1375         3511        50% cloudy              2136                   155
9/05/01    2543         5761        50% cloudy 1/2 day  3218                   127
9/07/01    3375         5970        clear                        2595                    77
9/26/01    3163         5421        clear                        2258                    71
9/27/01    1416         3608        cloudy 1/2 day         2192                   155
10/02/01  3093         5375         clear                       2282                    74
10/03/01  2649         4893         20% cloudy             2244                    85
10/04/01  2720         5017         10% cloudy             2297                    84
10/05/01  2728         5036         10% cloudy             2308                    85

Totals over 9 days
            Inverter   Nextek      Conditions             Improvement      %
               23062       44592         18.33% cloudy        21530                  93


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