APPLICATIONS -
The first commercial applications of the Nextek Technology were in Solar Powered, Grid Connected Lighting Systems.
In this example, the fluorescent lighting ballasts are DC compatible. This can be accomplished either by using our own 48VDC DC ballast or using any commercially available 277VAC ballast, approved for DC operation.
In most cases, an AC Ballast can be powered with DC. The DC power just 'skips over' the rectifier inside the ballast. We have approved several of these ballasts, and have received UL approval and letters from the manufacturers clarifying the 'full warranty' status when powered by DC.
With this configuration, Solar power from the photovoltaic panels passes through our gateway directly to the lighting system. This configuration is nearly 100% efficient and only succeptable to wire-losses and minimal losses through a diode in our gateway. Additional power, when needed, comes from the grid where any necessary AC power is rectified to DC. This system uses all available power from the cheapest source first, then supplements when needed from the grid.
The Old Way: A Traditional Solar System.
Solar Panels ---> Inverter ---> Rectifier in the Ballast ---> Lamps
AC Grid --->
Rectifier in the Ballast ---> Lamp
The Nextek Way
Solar Panels ---> Lamps
AC Grid --->
Rectifier in the Gateway ---> Lamp
In addition, traditional solar systems are subject to a law called "Anti-Islanding" which requires that all solar systems with thashut down, instantly, in the event of a grid failure. This is because traditional solar systems put AC into the grid, which would endanger line workers on a down grid. Solar systems in New Orleans after the hurricane were shut down.
The Nextek Technology is not subject to Anti-Islanding laws. This means that the lights stay on during a daytime power failure even if there are no batteries in the system. This system is ideal for retail stores that need to keep customers in the store during a brief power failure and for community centers that need long-term power in the event of grid failure.
Case Study: Distribution Warehouse,
Rochester, NY
June 15, 2004
Nextek Power Systems recently designed
and installed their high efficiency renewable energy lighting system at a Distribution
Center in Rochester, NY. This LEED™ gold rated facility is equipped with a
lighting system that utilizes DC fluorescent ballasts, roof-integrated solar
panels, occupancy sensors, and daylight sensors for the highest possible
efficiency. The building, including the innovative lighting design, was
designed by William McDonough and Partners of Charlottesville, VA.
The facility has 6,600 sq ft of office
space and 33,000 sq ft of warehouse. The
warehouse roof is equipped with skylights and 21kW of solar panels bonded to
the roof material (SR2001 amorphous panels by Solar Integrated Technologies). A
canopy in the office area is equipped with 2.1kW of Sharp panels.
Figure
1
- Sharp
Panels - Canopy
The power
from the solar panels is distributed in three ways:
2.2 kW is
dedicated to the lighting in the office,
11.5 kW powers
the lights in the warehouse,
11.5 kW is not
needed by the lighting system so it is inverted to AC and used elsewhere in the
building or sold back to the utility.
The entire system consists of 35
NPS-1000 smart power routers. These devices take all of the power from the
solar panels and send it directly to the lighting without significant losses.
Additional power, when needed at night or on cloudy days, is taken from the
grid.
In the office, 6 NPS-1000’s power 198 T-8, four foot fluorescent
lamps, illuminating most areas at 1.1 watts per square foot. Each of the fixtures
is equipped with one high efficiency DC ballast for every two lamps. Most of
the fixtures are controlled by a combination of manual switches, daylight
sensors, and occupancy sensors in 13 zones.
Figure
2
- Office
Lighting
In the warehouse area 29 NPS-1000’s power 158 6-lamp T-8 fixtures.
These fixtures have a low (2 lamps on), medium (4 lamps on), and high (all 6
lamps on) setting so that they can be dimmed by 3 daylight sensors and 30
occupancy sensors located throughout the area. The goal of the control architecture
is to maintain a lighting level of .74 watts per square foot, using daylight
when available, whenever the area is occupied.
Figure
3
- Warehouse
Lighting
The ‘logic’ of the lighting system is designed for optimum
efficiency. Sources of light and power and prioritized so that:
First, daylight from the skylights is used.
Second, if daylighting is not sufficient and the area is
occupied then power from the solar panels is added.
Third, if daylight and solar power is not enough then the
additional power required is taken from the grid.
Figure
4
- Daylight
and Occupancy Sensors (SensorSwitch)
A number of factors contribute to the value of this system.
- Using the electricity generated
by the solar panels to power the lighting eliminates significant inverter
losses and improved efficiency by as much as 20%.
- The low voltage control
capability of the DC ballasts enabled the innovative control system to be
installed easily, without additional AC wiring.
- Roof-Integrated solar panels
reduced installation costs and allow the cost of the roof to be recovered
using a 5-year accelerated depreciation formula.
Figure
5
- Occupancy
Sensors
The Red line shows the lighting
profile of the building without load shedding. Most of the lighting comes on at
3AM. All lights are turned on from 6AM to 6PM.
The Blue line shows the lighting
load with the occupancy and daylight sensors controlling the lighting.
Between March and Mid-June 2005
between 20% and 30% savings have been achieved due to the controls.
Figure
6
- Bar Chart
of kWh saved by controls
Note that
the savings are based on utility costs of $0.10/kWh. Savings are significantly
higher in areas where rates are higher. Usage reductions are during peak and
reduce demand charges where applicable.
In the chart below, power from the
DC solar system is shown, along with the net utility power consumed by the
lighting. Around noon, all of the power for the lighting is being supplied by
the solar. An important key here is that the efficiency of solar to lighting is
nearly 100%. Only minimal wiring losses are encountered when no grid power is
used.
Figure
7
- Power
Consumption by DC Lighting System
Figure
8
- Savings
with Controls and Solar DC Lighting
A The
Nextek Web-based Data Collection and Monitoring system provides a web-based
display of power generated, power used, weather, and more. Available through
the NextekPower.com website in a password protected directory, this system not
only displays performance data, but also identifies anomalies in the system
such as burned-out lamps, and sensors that are not operating properly. In June,
remote analysis identified a opportunity to improve the settings of the
occupancy sensors and will generate additional savings in coming months.
Info on Sharp Solar Panels
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