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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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