Hybrid Solar Lighting

Carroll McCormick looks at how the EAGLE hybrid portable runway light uses sun and conventional power sources.

The great strength of solar-powered portable runway lights is the speed at which they can be deployed and their complete independence from conventional power sources.  However, this virtue has limitations in sustained high-intensity lighting applications where there is insufficient sunshine to recharge these lights’ batteries.
Sierra Nevada Corporation (SNC), headquartered in Sparks, Nevada, in the United States, has apparently solved this problem with the EAGLE, a portable solar airfield lighting solution it is officially bringing to market this March.  Like other such lights, the EAGLE system uses the sun to power their light emitting diode (LED) arrays and to recharge their internal batteries.  Uniquely for a commercial system, however, EAGLE lights can be quickly wired together and powered from any conventional power source, such as a portable generator or utility.
SNC is a global systems integrator and electronic systems provider.  It has seven business areas, including space systems, surveillance and electronic warfare instrumentation.  Its Communication, Navigation, Surveillance/Air Traffic Management business area has been involved in air traffic control for 15 years and airfield lighting for the military for four years.  For example, it is the prime contractor for the Mobile Tower System (MOTS) that provides air traffic services to military customers.  MOTS includes a system capable of providing medium-intensity lighting for a 5,000ft (1,524m) runway.  It can be operated solely by solar power, or with wired, auxiliary power.
The EAGLE system is SNC’s launch product of an independent, civilian commercial line of airfield lighting equipment; the company is in the process of putting the final processes into place.  “We developed this product line to meet Federal Aviation Administration (FAA) and International Civil Aviation Organisation (ICAO) requirements,” says Mike Davis, Programme Manager for SNC’s airfield lighting system product line.
Currently, the line consists of EAGLE lights and support equipment: The lights are fitted with LED optical heads that provide any aviation colour, such as white light for runway edge illumination, or the red/green heads required for threshold applications.  They are also night vision goggle (NVG) compatible.  SNC sells two different power cable lengths: 210ft (64m) cables for connecting the edge light to each other, and 12ft (3.66m) cables for connecting the threshold lights together.  Thus connected, the entire system is plugged into to an auxiliary charging system that converts alternating current power from generator or utility power to high-voltage direct current power for the lights.
The line also includes a hand-held remote control for operating the lights’ various functionalities.  Hardware can be installed in an air traffic control tower so controllers can adjust the intensity of the lights, turn on and off all sections of the lighting system, switch to NVG-compatible mode or perform battery and LED diagnostics testing during operations.  Pilots can also use their on-board aviation radios, in flight to turn the system on and off and control light intensities from as far away as ten nautical miles.
Since any number of runway edge and threshold lights can be purchased, along with optional power cables, if required, the EAGLE system is scalable to any runway length and width.  A complete runway lighting system can be brought into an airport, laid out in under 45 minutes and be put into operation with no delay.

Out of the box: an array of EAGLE runway edge and threshold lights. (All images - SNC)

The lights are immediately ready to provide over 40 hours of continuous operation without solar or auxiliary charge, 30 hours of which can be at the high intensity required for non-precision instrument flight rules (IFR) operations.
“Defence forces or a Civil Aviation Authority can go in to an airport and run these lights for 30 hours at an intensity that you would find at most commercial airports,” says Allister Wilmott, Director of ARC Aviation Renewables Corp, headquartered in Victoria, British Columbia, Canada.  “This is the first and most advanced technology in the market that meets FAA non-precision IFR lighting medium-intensity lighting standards, with a back-up cable system that can be activated at a moment’s notice to keep the batteries charged and sustain indefinite IFR lighting levels.”
Aviation Renewables is a specialist lighting and power consulting company with a focus on renewable technology solutions for the aviation industry, manufacturers and governments.  It is assisting SNC with the sales and marketing of its EAGLE system.
Normally, airport operators can expect the sun to begin recharging the EAGLE’s batteries long before they are discharged.  However, an airport might be located where there is a long period of little sunshine, perhaps at a high northern latitude and that may require operations demanding sustained maximum-intensity lighting for non-precision IFR operations.
Under this scenario, operators can connect the lights together with the power cables.  “Hooking up the auxiliary power system is about as difficult as hooking up a clothes dryer,” Davis explains.  “The system can hook into any kind of power in the world.”
An EAGLE system is so user-friendly and draws so little power that, for example, a system lighting a 10,000ft (3,048m) runway can be continuously charged from a 3kW gasoline-powered generator purchased from a local hardware store.  If there is a power interruption, the lights’ batteries simply take over.
 
Teaming Partner
SNC is teamed with Victoria, Australia-based Sealite Pty Ltd, which manufacturers a wide range of solar-powered LED products.  Sealite’s subsidiary Avlite Systems, which manufactures solar-powered aviation lighting equipment, is the contract manufacturer to SNC for the EAGLE.
The EAGLE combines the technology Avlite uses in its AV450 radio-controlled solar airfield light and SNC engineering that enables the lights to accept auxiliary power.  “Avlite lights do not come with auxiliary power systems.  SNC integrates auxiliary systems, including a high-voltage power supply, that can charge the internal battery,” Davis says.
Plug and power: solar-powered EAGLE lights, which meet Federal Aviation Administration non-precision Instrument Flight Rules medium-intensity lighting standards, can be linked with a back-up cable system.

“We have taken Avlite’s base product and improved the options, power supplies and alternative power schemes for our commercial line,” adds Tom Colby, Product Line Manager for Mobile Towers and Airfield Lights with SNC.
Since SNC and Avlite are partnered, customers purchasing an EAGLE system can, at the same time, order other solar-powered airfield lighting products, such as taxiway edge lights and wind cone illumination that Avlite manufactures.
For example, Wilmott notes: “SNC, with assistance from Aviation Renewables, is currently putting together a runway edge, threshold, taxiway, distance-to-go, directional signage and LED-based Precision Approach Path Indicator (PAPI) lighting system, all to be powered by solar, battery and cable.”
Aviation Renewables represents additional companies that provide conventional and renewable based lighting equipment such as, Laser Guidance Inc, based in Redmond, Washington, USA, which manufactures LED visible/infrared solar-powered PAPI/APAPI equipment.  This hardware can also be powered by solar/fuel-cell hybrid, generator, or utility power.
 
The Technology
EAGLE is designed for flexible and secure operation.  The lexan light housings are highly impact resistant and the lights are waterproof to the International Protection Rating IP68 code.  This means that the lights are dust tight and can operate in water deeper than 3ft (1m).
Each light’s LED array draws just 4.2kW of power, compared to 45kW for an incandescent, medium-intensity runway edge light.  It will operate for 30 hours at high intensity until the battery is drawn down to one-half capacity.  Under normal operation it will warn the operator to shut down to protect the battery life, but operators can, if necessary, choose to extend the operating time.  Under normal solar or auxiliary powering conditions the batteries recharge continually.
The lights are operated by an encrypted radio frequency hand-held controller that can be used anywhere on the airfield.  Redundant control can be had through the cabling system.  Each light has a receiver/transmitter, which keeps them in synch.  Fault detection capabilities allow detection of LED failures, cable power faults and weak batteries.
The EAGLE has several operating modes such as programmable lighting groups, dusk to dawn operation, adjustable intensity and sequence flashing.
Close up: Light Emitting Diodes in this red/green threshold light head consume a fraction of the power of a conventional light, and last far longer.

At the time of writing, the EAGLE was being prepared for testing by Intertek to the FAA L861 photometric and chromaticity requirements.  This company provides performance evaluations for all types of airport lighting products to, for example, FAA, ICAO, NATO and military specifications.  Photometry refers to the measurement of light in terms of brightness to the human eye, including luminosity or visual sensitivity.  Chromaticity, roughly-speaking, refers to the colour of the light.
Once the EAGLE passes the Intertek test, Colby explains: “An airfield manager wanting to replace an airfield lighting system at a non-Part 139 or visual flight rules airport, including those with non-precision IFR landing systems, can come to SNC for a solution.  We will be able to configure and provide runway, taxiway and threshold lights capable of FAA lighting intensities − an entire airfield lighting system which operates from solar, battery and high-voltage cables.  If it is connected to cables, it will provide FAA photometric intensities indefinitely without the need for solar recharging.  There is currently no portable, solar-powered light that met the L861 photometric requirement for runway edge and threshold lights.”
Due to the stringent requirements for permanent airfield lighting at Part 139 commercial airports, solar-powered lights are currently only regarded as suitable for contingency lighting or for areas with no access to conventional power such as temporary, emergency, taxiways, secondary runways and construction lighting.  Some commercial airports do stock solar-powered lights to replace runway edge lights or taxiway edge lights for use during power failures or if they are broken by snow removal equipment.
More work has to be done with the FAA and industry stakeholders before solar-powered lighting systems can be sold to Part 139 commercial airports for regular use, according to Wilmott.  However, certification for such use is probably just a matter of time.
Industry and users, such as the US military, are keen for the FAA to develop standards for permanently installed solar-powered lights.  Even leaving aside the advantage of free solar power, airports have been switching to LED lights for several years: they appreciate that LED operating costs are a fraction of that of incandescent lights, and that maintenance costs are lower.
As for free power and hybrid systems, airports located in sunny climates might need auxiliary power for only 5% of the year.  For the other 95% of the year, day or night, the lights can operate on solar at no cost.
For now, however, SNC is betting that there is a healthy global market for the contingency use of hybrid systems.  Last November, for example, Avlite received an order for its AV420 solar runway edge lights from the Civil Aviation Authority of a sub-Saharan African country for its international airport.  The airport was having reliability issues with its conventional runway lighting system and required a short-term emergency solution that could also serve as a long-term back-up solution.  The solar-powered lights will be used during a planned refit of the airport conventional lighting system.
SNC believes that there is a market for permanent installations of its EAGLE systems at airports with little commercial traffic.  Precedents have already been set: In 2006, for example, the Bahamas Civil Aviation Department made a C$2.6-million (US$2.4m) supply agreement to Carmanah Technologies Corporation in Victoria, Canada to supply solar-powered LED airfield lighting systems to 16 Family Island airports.
“Aviation Renewables is working with international and regional airports in the Middle East, Caribbean, Asia and South America that receive commercial traffic,” Wilmott says.  “There are many airports where power is expensive, no infrastructure is in place, or conventional systems are reaching the end of their useful lives.  Here, EAGLE hybrid systems would be ideal.”