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GSE De-icing systems for roadways and runways:  White Paper  
 

 

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GSE De-icing systems for roadways and runways:  White Paper

 

Abstract:



GSE provides a variety of methods of horizontal surface ice mitigation  based upon pressure conversion to heat systems.    In this paper we will examine the mechanics of Gse roadway deicing, and compare these systems to traditional methods. We will also examine the cost structures from implementation to maintenance, and compare the relative effectiveness.   We will also examine the environmental impacts of traditional methods in comparison to GSE technologies.
 

Contents:


- Summary of current technologies
- Structural overview of GSE de-icing technologies
- Installation and maintenance of GSE systems
- Advantages of GSE de-icing technologies
- Summary & conclusions
- Literature Review
 
Summary of current technologies

The predominant ice mitigation technologies can  characterized as either dry or liquid chemical distribution methods.Salt Dome Roadway salting is the most most widespread method and consist of local salt storage and distribution via spreaders in anticipation of icing conditions.   Salting and other dry chemical distribution methods are ideal for de-icing large areas, but suffer fro a variety of growing environmental concerns.   The costs and effectiveness of dry chemical distribution vary with logistics, distribution infrastructure and effectiveness at various temperatures.

Liquid de-icing methods are increasingly popular around the world, but are largely limited to vehicles, bridges and other particularly vulnerable roadway features.  These methods share the same or similar logistic, infrastructure, environmental, distribution and effectiveness challenges of dry chemical distribution methods. Liquid systems require increased maintenance and start-up costs when compared to dry systems.  Liquid systems can generally be easily mated with sensor based control systems, which gives them an advantage over manual dry distribution methods.  The mating of liquid distribution systems with sensor based controllers provides the added advantage of greater efficiency in that distribution is based upon actual conditions as opposed to forecasts.   One primary limitation of many liquid distribution systems are the power distribution requirements of such systems.

Both liquid and dry distribution systems are sources of often widespread environmental damage.   In some population centers,  agricultural areas, and sensitive ecological areas the distribution of chemicals is strongly opposed by many direct and proxy stakeholders.

Several heating technologies are also undergoing trails around the globe.  The conductive concrete and other pavement heating methods are effective but limited by the need for grid or locally generated power.
 

GSE internals

Structural overview of GSE de-icing technologies



GSE devices are based upon our patent pending PEC (pressure energy collection) system.  For the purposes of de-icing GSE  R-SBC and R-SHC are roadway temporarily or  seasonally emplaced or permanently embedded devices  that convert  ambient atmosphere into compressed air.  Usually, air is first drawn from the surrounding area, although other sources of compressible gas are feasible, into large flexible bladder systems by the movement of heavy vehicles over the device.  The captured gas is then compressed by the weight of subsequent heavy vehicle traffic.   Gas compression generates two usable products, compressed air and heat. 

The compressed air can be converted into electricity, directed pressure, fluid movement, or it can be used to operate pneumatic devices, such as barriers or signage.   The heat product is captured via manifolds which connect to buried piping for the circulation of heated liquid.  The systems are also effective during low traffic whClosed loopen coupled with a geothermal heat sink.  The heat  sink will ensure that the de-icing liquid is always maintained above freezing.

Heated liquid can alternatively be shunted to other  uses when de-icing is not required.  Applications include ; municipal steam,  heat pumps, de-salination, etc.

 Installation and maintenance of GSE systems:R-SHC



GSE devices are engineered for many operational phases.  Retail products include R-SBC and RSBH models engineered to be attached to roadways for fixed durations ranging form a single work session to years.  These devices are attached to the roadbed with spikes and in some cases industrial adhesives.   The distribution systems for the compressed gas and the heated fluids can be comprised of shielded hoses.   These systems require no electricity or fuel, and are therefore  easy and extremely cost effective even for short term use in difficult locations.   Experienced crews can install de-icing, or fluid mitigation capabilities on a small bridge in an 2-4 hour period.
custom roadway compressor
Our custom lines are enginCustom roadway embedded compressor eered to client specifications and are incorporated directly into the roadway with extensive cut outs and underground piping.  These systems can be engineered to optimize  traffic flows by de-icing, speed control, barrier activation, or signage and lighting.  Custom engineered solutions are ideal for larger  bridges, cloverleaf systems, and high speed ramps.  Custom systems can be engineered with metal or rubberized vehicle interfaces.

Many GSE devices can also be controlled via automated sensors, including; RADAR, LIDAR, and various sensors including temperature, humidity, or pressure.



Advantages of GSE de-icing technologies:



GSE de-icing technologies provide a number of important advantages of traditional methods. The primary advantage is the robust  no fuel engineering of GSE systems.  No other de-icing methods is more environmentally friendly, or reliable.  GSE systems do not require fuel or electrical grid connections.  GSE traffic driven de-icing systems are naturally demand driven, and are therefore environmentally inert if there is no traffic.   The deployment of demand driven de-icing systems can provide wide ranging  savings from operations, maintenance, and administration.  Although demand driven systems are ideal for bridges and overpasses, which are particularly vulnerable to icing, the low operational costs make GSE solutions cost effective for larger areas, such as ramps and parking lots.  Environmental activists will not oppose GSE systems which virtually eliminate chemical distribution.

GSE de-icing systems can also provide additional  community resources, such as hot water, compressed air, speed control, and vehicle exhaust mitigation and are therefore valuable to adjacent communities year round.
 

Summary & conclusions:

GSE demand driven de-icing solutions are ideally suited for a variety of roadway de-icing applications.   GSE systems provide numerous advantages over traditional dry or liquid de-icing methods.  The significant environmental, operational  and administrative advantages of GSE de-icing systems  vastly out weight the 25% increased in initial construction cost.



Literature Reviews:


Conductive Concrete:
 
Over the past 10 years, an innovative material called “conductive concrete” has been developed and evaluated
for bridge-deck deicing. Conductive concrete is a cementitious mixture containing electrically conductive
components to enable conduction of electricity. Because of its electrical resistance and impedance, a thin conductive
concrete overlay can generate enough heat to pre-vent ice formation on a bridge deck when connected to
a power source.

The original conductive concrete mix was developed at the University of Nebraska and later modifi ed at Western
Michigan University (WMU). The mix was implemented in a bridge-deck deicing application. Conductive concrete
is currently being investigated at WMU for other applications such as electromagnetic shielding and cathodic
protection of reinforcement.

The first generation of conductive concrete was developed in 1998 utilizing steel fi bers and steel shavings. The
main objective was to develop a conductive concrete mix to achieve high electrical conductivity and high mechanical
strength. Christopher Tuan, a professor of civil engineering at the University of Nebraska at Lincoln, and I evaluated the mechanical and electrical properties of the
mix in accordance with the ASTM and AASHTO specifications. The compressive strength, fl exural strength,
freeze-thaw resistance, permeability, shrinkage, thermal conductivity and electric resistivity of the mixture have
been determined. Laboratory testing and results showed that a thin conductive concrete overlay
on a bridge deck may become a very cost-effective deicing method.

In 2001, Tuan and I developed a conductive concrete mix utilizing carbon powder and steel fi ber. The carbon powder was used to replace
the steel shavings that were used during the early development of the conductive concrete mix. The mixture has a compressive strength of
4,500 psi and provides an average thermal power density of 55 W/sq ft with a heating rate of 0.25°F/min in
a winter environment. This mix was couples for deicing monitoring during winter storms. A microprocessor based
controller system was installed to monitor the slab temperature and current and to maintain the slab
temperature below 55°F and above 35°F.

The conductive concrete deicing system has shown excellent deicing
performance during the past five years. The average energy consumption
is 2,821 kW/hr, and the average unit cost is $0.07 per sq ft during the five
years of operation.
Road Salting Operations

The current view from the state of Michigan in the USA;

In the 21 counties in which the MDOT maintains the state trunk lines, operations are run from 30 locations; in the remaining 62 counties, trunk-lines are maintained by contractors to the MDOT. Road salt is the predominant deicing chemical used by the MDOT; sand is the abrasive exclusively used.  Calcium chloride and CMA also are used, but in far smaller volume than road salt; these chemicals and sand are discussed below. The MDOT uses 260 trucks to plow snow and to spread the deicers and sand. To predict and monitor road conditions, various sophisticated technologies are used, including pavement condition sensors that monitor surface temperatures, moisture, and chemical concentrations on road surfaces. Deicing materials are used to a much higher degree in the four county metropolitan Detroit district than in the rest of the state; this is not only because of the area’s large number of roadways, but also because many are below ground level.

(http://www.michigan.gov/documents/ch2-deice_51438_7.pdf)

***************************************


HOW IT WORKS; Black Ice, Wise Bridge: Repelling the Foe Before It Forms

By JEFFREY SELINGO

Published: December 13, 2001



THE eight-lane bridge that spans the Mississippi River on Interstate 35 near downtown Minneapolis was a notorious spot for car accidents in the winter. Moisture from the river and the bridge's high elevation quickly combined to form black ice, and more than 100 accidents in the late 1990's were attributed to the roadway's treacherous surface.

State transportation officials stepped up their efforts to keep the bridge clear of ice, sending out trucks just to salt the structure itself and not adjacent roadways, but the problem continued. ''It was a mess,'' said Cory Johnson, a maintenance engineer with the Minnesota Department of Transportation. ''We couldn't treat it fast enough, especially during rush hour, when there was stop-and-go traffic. We were at a loss about what to do.''

In 1999 the state installed an automated de-icing system on the bridge. The system aims to stay ahead of the weather by spraying the bridge surface with anti-icing chemicals before ice forms. Accidents on the bridge have dropped nearly 70 percent since the system was installed, Mr. Johnson said. Last winter alone, it prevented 21 accidents, state officials estimated. About 60 similar automated de-icing systems have been installed on bridges in North America, most of them in Canada, said Jerry R. Waldman, general manager of the American branch of the Swiss company Boschung, one of the manufacturers of the technology. As roadside signs attest, bridges tend to freeze before roadways do because cold air passes above and below the span.

The de-icing technology uses sensors about the size of hockey pucks that are embedded in the bridge deck, and a small weather station at one end of the structure. One set of sensors monitor whether the bridge is wet or dry, another measures the pavement temperature, and a third is cooled to 3.6 degrees below the temperature of the surrounding roadway. Frost or ice forms on the cooled sensor before it does on the bridge deck itself, so the cooled sensor can act as a trigger for the sprayers.

The sprayers, also embedded in the bridge deck, spread a liquid chemical about a foot above the road's surface. Unlike road salt, this chemical is intended to prevent freezing, not to melt existing ice. A computer regulates the amount of chemical sprayed, relying on information from the other sensors and the weather station, so that less is applied for frost and more for snow, Mr. Waldman said.  ''Most drivers don't even notice when the system is working,'' he said. The road sensors have some drawbacks, Mr. Waldman said. For instance, they may fail to detect heavy snow when flakes melt before reaching the roadway. At such times, the system can be activated from its weather station, which identifies the type and rate of precipitation when it passes through a light beam. When the system is triggered, road crews are notified by a central computer or with a message on their beepers, alerting them that dangerous conditions may soon appear on adjacent roadways.

Pennsylvania has placed the de-icing system on six bridges in the state, and a seventh is to be installed in January. Requests are pending to put the mechanism on 10 other bridges, said Gary Hoffman, chief engineer with the state's Department of Transportation, which spends 18 percent of its $1.1 billion maintenance budget on coping with winter weather. ''Usually, when you implement a new technology, it's hard to convince those out in the field,'' he said. ''This is one of the few things that sold itself.''  The state was the first in the nation to install the system. Mr. Hoffman discovered the technology while on a worldwide winter maintenance tour sponsored by the Federal Highway Administration in the mid-1990's. It has been used in parts of Europe for more than 20 years.

The automated features of the de-icing technology are what most appealed to Pennsylvania officials. The bridges where the system was placed are all heavily traveled, have a history of accidents and are far from maintenance facilities. ''We wanted a fail-safe system that didn't require someone having to monitor a remote site and make a decision to trigger the system,'' Mr. Hoffman said. (The only human intervention required is refilling the tank that holds the de-icing chemical.)

Since the automated system uses less of the de-icing chemicals than trucks would in spraying, the technology has allowed the state to use magnesium chloride, which is more expensive, on the bridges. It is less corrosive to the roads and passing cars than sodium chloride, which is used throughout the rest of the state, Mr. Hoffman said.

Before the system was installed, each snowstorm would result in law enforcement investigations of nearly a dozen car crashes on one bridge in western Pennsylvania. Since the system's installation more than two years ago, only one accident on the bridge has been attributed to the winter weather.  The system's price differs depending on the structure. Installing the technology on that 1,900-foot bridge over the Mississippi, for instance, cost Minnesota about $537,000. Because of the hefty cost, Mr. Waldman said, the technology will probably not be installed on roadways other than bridges. But a miniature weather station similar to the one on the bridges is used elsewhere. Pennsylvania has installed 75 of the stations on roads so that road crews can monitor conditions in a particular area. Drivers also have access to the information over the Internet at 208.9.196.31/site/site.nsf/mainpage.

''It's not as quick and easy as the automated system,'' Mr. Hoffman said, ''but it's still effective and a lot more widespread.''  Chart: ''A Wary Roadway'' Although they are called bridge de-icers, they are really meant to keep ice from forming in the first place. They can be vital because those ''Bridge Freezes Before Roadway'' signs are correct: the cold air circulating above and below bridges means that ice forms faster on spans. The devices are part weather station, part sprinkler, collecting data on road conditions and turning on a spray of magnesium chloride when they sense danger. PUMP STATION A de-icing chemical, magnesium chloride, is pumped from a tank set nearby through sprinkler heads mounted flush with the bridge surface. The amount sprayed is adjusted according to weather conditions. SLIPPERY STATES Different weather conditions create different kinds of hazards. The most common kind of ice forms when wet patches freeze as the temperature drops. Black ice forms when rain falls on a road surface that is colder than the freezing point. Snow can turn to ice as it is compacted by traffic. Slippery frost is formed when warm mist moves over a cold road. A station set near one end of a bridge collects weather data. It can send a warning when freezing conditions are developing. SPRAYERS Mounted flush with the pavement, they shoot streams of deicer about a foot above the road. SENSORS Embedded in the roadway, they are cooled slightly so that frost will form on them shortly before it does on the road surface. (Source: Boschung America) Drawing (Frank O'Connell/The New York Times)

        *************************

For the vast majority of Americans and Canadians, the new decade began under several feet of snow, icy roads and difficult travel conditions. It's a not-so-subtle reminder of the need to maintain open travel ways — roads and bridges, airport taxiways and runways — in frigid temperatures. Let's take a look at various methods to break the ice — or prevent the ice — that can make winter travel less of a slippery proposition.

To de-ice or anti-ice?

Anti-icing is aimed at preventing ice from forming while de-icing is designed to remove ice after it begins to accumulate. De-icing removes frozen contaminants: snow, ice, slush and frost that are already bonded or formed to a surface. Methods of de-icing include mechanical processes (scraping, pushing); heat application; use of dry or liquid chemicals that lower the freezing point of water; or a combination of these techniques.   De-icing fluids can be applied over thin ice or snow pack but are best used early in a storm at their full strength as an anti-icer. There is no need for them to be diluted or heated.

Dry chemicals are best applied at the beginning of a storm and directly over ice or snow-pack to break the bonding effect of the frozen precipitation to the pavement. Dry chemicals may be pre-wetted with brine or other liquids to help them stick to the paved surfaces and to start melting ice more quickly. Once the ice or snow-pack is loose after de-icing, mechanical means are usually recommended to remove it to prevent re-freezing or re-bonding as the de-icer is diluted by melting ice or snow.  The effectiveness of de-icers depends on surface temperature, application rate, the amount of moisture or water present, and the applied concentration. When choosing a de-icer, it is important to review the certification, the effectiveness and how the de-icer works. Also, consider where it will be used: Is there an environmental or corrosion concern? The non-chloride de-icers are safer.

Solid de-icers are generally applied after snow and ice have fallen and bonded to the surface. Solids penetrate through the accumulated pack to the pavement as the de-icer alters its form from solid to liquid. Some solids like anhydrous sodium acetate actually give off heat (exothermic reaction) as they dissolve.  Solid de-icers are available as either pellets or granules. Pelleted de-icers are harder, less dusty and tend to spread more evenly. Pellets and granules stick to the surface and have less bounce during application when applied on wet or light-snow-covered surfaces.

Liquid de-icers are generally used as “anti-icers.” The choice of the right chemical for anti-icing applications is dependent upon a number of factors, including the area's climate, chemical availability as well as environmental concerns. A fundamental characteristic of anti-icing chemicals is the ability to reduce the freezing point when added to water.  Anti-icing on roadways prevents ice and snow from adhering to the pavement, thus allowing easier removal by mechanical methods (snowplows). Brine or wetted salt is usually applied shortly before a snowstorm arrives. If performed properly, anti-icing can significantly reduce the amount of salt required to clear snow from a roadway.

Generally, anti-icing techniques are more efficient than de-icing because less energy is needed — therefore, less chemical is used — to prevent a bond from forming than to break it. Anti-icing can be applied before a storm hits or early in the storm. Maintenance costs are lower, and there is a reduced environmental impact. Unfortunately, anti-icing measures alone are not enough to keep the paths of commerce and education open. A balance of anti-icing and de-icing methods is necessary. Understanding when and how to apply the appropriate chemicals for greatest effect comes by observing and measuring the combination of environment, chemical, application and result. This scientific approach is evident every winter day as we drive to work or board a plane to take us to sunnier and warmer climes.

***************************************

GLYCOL AND GLYCOL/POTASSIUM ACETATE
Because of environmental reasons, these liquids are being phased out as runway de-icers. Glycol is used primarily today as a wing de-icer. At heavy-use airports, it is collected in holding tanks or ponds so it is not released into the environment.

UREA
This farm fertilizer is not airport grade (technical grade), nor is it certified to FAA AMS 1431B. Its performance is poor and works best in temperatures above 20° F. Urea is environmentally unacceptable by the EPA and banned from U.S. Air Force bases. It does not store well and the cost has escalated dramatically. It is about as destructive to concrete as rock salt.

POTASSIUM FORMATE
This non-toxic salt of formic acid forms water solutions with a high density and a low freezing point. Potassium formate decomposes in the environment resulting in carbon oxides, water and other more stable potassium salts. Potassium formate is available as a 50 percent solution in water.

SODIUM FORMATE SOLID
The granular form works in low temperatures, is dusty and imported to the United States.

POTASSIUM ACETATE LIQUID
This low-freezing-point liquid is the choice of U.S. and Canadian airports. Potassium acetate is used by airports throughout the world on runways, taxiways and peripheral roads and bridges. Potassium acetate has largely replaced glycols at airports. It is a safer and far more environmentally friendly alternative to ethylene glycol and is preferred over propylene glycol at most airport facilities. It may also be used as an aircraft lavatory antifreeze.

POTASSIUM ACETATE-BASED (KAC) LIQUID E36
It is recommended by the EPA as alternative de-icer/anti-icer to glycol and urea and is used in most major airports in the United States, Canada and Europe. Liquid is a 50% solution and is applied at 0.25 to 1.5 gallons per 1,000 square feet. Used by most airports worldwide, it is effective to -20° F, works quicker than urea and glycols (only 5-10 minutes); and is less slippery than glycols. Performance is enhanced with thin ice, warmer temperatures and fractured ice.

ANHYDROUS SODIUM ACETATE SOLID (NAAC)
This sodium acetate-based solid runway de-icer meets FAA-approved specifications for use by commercial airports and military bases. Benefits are low corrosion, effective performance, minimum dust, less compaction in storage, even spread patterns, low toxicity and biodegradabilty. Also used on parking structures and bridges where chloride de-icers should be avoided.

POTASSIUM ACETATE/BIO-BASED (SUSTERRA™) NEW LIQUID BX36
The propanediol provides low conductivity and less ASR expansion. (ASR is the abbreviation for a naturally occurring phenomenon called alkali-silica reaction. Commonly defined, it is the expansive deterioration of concrete due to a chemical reaction involving concrete aggregate and cement paste.)

SODIUM ACETATE/BIO-BASED (SUSTERRA) NEW PROPANEDIOL (PDO)
Liquid NX360 offers low conductivity and lower freeze point. XT360 is bio-based (Susterra).



SOURCE: De-ice or Anti-ice? What's an Airport to Do? was presented at the 2009 NIGP Annual Forum by Tony Myhra, Cryotech Deicing Technology.



Read more: http://govpro.com/mag/ice-removal-strategies-201002-03/index1.html#ixzz1mekY4J53






  


     
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