The Nextek Way

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 susceptible 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

System Overview

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. 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-1000s 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. In the warehouse area 29 NPS-1000s 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. 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. 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%.
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• The low voltage control capability of the DC ballasts enabled the innovative control system to be installed easily, without additional AC wiring.
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• Roof-Integrated solar panels reduced installation costs and allow the cost of the roof to be recovered using a 5-year accelerated depreciation formula.

Performance Occupancy and Daylight 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. 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.

Performance of the Nextek Gateway for Power

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.

Monitoring Web Based

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.