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Natural Gas Vehicles in Construction & Aggregate Fleets: What You Need to Know

If you are involved in the Construction & Aggregate (ConAgg) industry, it is very likely you have heard of Natural Gas Vehicles (NGVs). ConAgg fleets are increasingly turning to Compressed Natural Gas (CNG) and Liquefied Natural Gas (LNG) as an alternative to diesel fuel. Natural gas is a clean, abundant fuel that is less costly than petroleum fuels. The popularity of this option arises from a few key advantages, but it is important to understand the challenges of the transition as well. You will see this fuel increasingly more in the mines, on the roads, and delivering concrete to jobs around the country. Here is what you need to know.  

Argos recently took delivery of 40 CNG mixers. Image Credit: Oshkosh Corp.

Argos recently took delivery of 40 CNG mixers. Image Credit: Oshkosh Corp.

1. Natural Gas Will Lower Your Fuel Costs

Natural gas typically offers fuel savings of 40-60% compared to diesel fuel. Economics is the primary driver of this transition. Most ready-mix concrete trucks consume an average of 40 gallons of diesel fuel each day, or around 10,000 gallons annually. With diesel fuel currently averaging around  $3.60 per gallon, fuel savings of 50% yields annual savings of $18,000 for each truck. However, natural gas trucks tend to have lower fuel economy, so we will reduce this figure by 20% to $14,400 as an annual cost savings figure. If you operate a batch plant with 20 ready-trucks running on natural gas, your operation costs will be $288,000 lower than your competition, who is most likely using diesel fuel. If you are running sand & gravel trucks, the economics are even more attractive. Most aggregate trucks use closer to 20,000 gallons of fuel each year. The fuel savings with a fleet of 20 trucks (including the fuel economy hit) jumps all the way to $576,000. So the clear message here is take a close look at your fuel figures when beginning a natural gas evaluation. The more fuel you burn, the more likely it is that you are a good candidate. 

Tractors in the ConAgg industry can easily exceed 20,000 gallons per year in fuel consumption, making them ideal targets for natural gas.  Image Credit: Clean Energy 

Tractors in the ConAgg industry can easily exceed 20,000 gallons per year in fuel consumption, making them ideal targets for natural gas.  Image Credit: Clean Energy 

The final consideration of your cost savings estimate is going to be the incremental truck cost. Natural gas trucks carry an incremental cost between $30,000 - $70,000 depending on fuel storage specifications. The more fuel you carry, the more expensive the truck will be. Costs also vary widely between dealers, so make sure you shop around. It typically takes 2-3 years to recoup this additional investment before you can bank the fuel savings. Increasingly, states are implementing natural gas grant programs to buy-down this incremental cost. Colorado, for example, has up to $42,000 available for the purchase of a heavy duty CNG truck. Texas and Pennsylvania have similar programs. You can find all the incentives by state here. Most fleets are making the shift without truck incentives, but if they are available don't miss out. 

2. Natural Gas Trucks are Typically Heavier

Natural gas trucks often weigh more than diesel units do. We have previously written a detailed outline of the weight story and the difference between CNG and LNG. There are currently two Cummins engines available for concrete mixers and tractors, a 9L and a 12L. The vast majority of fleets opt for the larger, heavier 12L engine. For most applications, this is the right decision. However, you may want to look at the life cycle of the smaller engine as well. The smaller 9L is certainly no powerhouse, but there are numerous mixers in the field using this engine today. Why? Some fleets decide to use the smaller engine due to lower weight, specifically I mean weight that is lower that diesel trucks. A 9L powered mixer can often allow you to add as much as 1/2 yard of concrete to every delivery, which adds up quickly.  So while this engine may be small, if you run on flat terrain it is worth including in your evaluation. Combined with the fuel savings it may be very profitable to use a smaller engine and simply plan for a shorter truck life. 

3. You Will Need New Fueling Stations

A GE compression system located at a batch plant. Image Credit: GE Energy

A GE compression system located at a batch plant. Image Credit: GE Energy

Most fleets will require new fueling infrastructure at batch plants or along regular delivery routes. Fueling stations have continued to come down in cost the past few years, and now range from $500,000 to $1.2 million depending on size. You can certainly purchase and own a new fueling station, but most fuel providers are also willing to invest the capital for the station in return for fueling agreements. Low interest operating leases are also becoming common if you prefer a simply monthly payment for your station. You can also investigate public access stations in your operational areas that can accommodate heavy duty trucks. Natural gas is primarily a heavy-duty fuel and more and more truck stops are offering natural gas. You can research them here

An overnight fueling station developed for MMC.  Image Credit: Concrete Products

An overnight fueling station developed for MMC. Image Credit: Concrete Products

There are numerous on-site fueling technologies that are well suited to the ConAgg industry. Vehicles can be fueled quickly (fast-fill) or overnight (time-fill) -- we previously posted a description of CNG station options and how to get started on an evaluation. The NGV fueling industry has developed mobile stations as well as small modular stations that are a great fit for batch plant operations. There is a lot of information available on the station side, so I recommend you start by meeting with local fueling station providers such as Clean Energy, Trillium, and TruStar. Station providers can provide a host of other important services as well, such as bulk commodity buying, station operations and maintenance, extended warranties, safety plans, and even royalties for selling fuel to third parties on your property. 

4. You Can Use Natural Gas Programs to Improve Sustainability and Win Business

Natural gas is a very clean fuel that produces lower greenhouse gas emissions than diesel fuel . If you are seeking to improve your sustainability program, natural gas can help. Most natural gas programs are based on fossil fuel, but you can also run your trucks on Renewable Natural Gas (RNG). RNG is biogas harvested from landfills, wastewater treatment plants, and dairy farms. The gas is cleaned and re-injected into the pipelines where it can be nominated to any fleet or fueling operation around the country. This will generate Renewable Identification Numbers (RINs) nationwide and Low Carbon Fuel Standard (LCFS) credits if you are in California.  Both of these credits can potentially be monetized in different ways. Most importantly, if you are bidding on concrete jobs for LEED buildings or "green" construction projects, you can use CNG, LNG or RNG to increase you sustainability scores and help you win the deal. 

5. This is the Just the Beginning

Caterpillar recently introduced an LNG option for the 793,795, and 797 hauling trucks. Image Credit: Caterpillar

Caterpillar recently introduced an LNG option for the 793,795, and 797 hauling trucks. Image Credit: Caterpillar

If you think natural gas fueling is limited to trucks, think again. If an engine is big...it's going natural gas. This is the beginning of a VERY large fuel transition that is much broader than on-road vehicles. Caterpillar is already rolling out a variety of LNG systems for yellow iron in coal mines. They are starting with the largest units and working their way down in size. Many quarries and mines rely on rail to move their product to market. The first rail cars running on CNG and LNG are now on the tracks with the backing of GE, BNSF and Union Pacific. Future station programs will involve fueling yellow iron in the pits, railcars in one lane, and delivery trucks in the next.  

One final consideration that is now gaining traction is natural gas as an alternative for remote asphalt plants. Most of these plants are running on waste oil or diesel fuel, but they often come equipped to run on natural gas as well.  Both CNG and LNG can be trucked to remote or short term locations at a substantial savings. If you regularly see $500,000 fuel bills to run your asphalt plants, you may want to consider natural gas. New business operators, such as NGAdvantage, have developed CNG solutions targeted specifically at asphalt plants. Traditional LNG operators can compete for this business as well. 

NG Advantage can help you maximize profits by delivering CNG to remote plant locations. Image Credit: NGAdvantage

NG Advantage can help you maximize profits by delivering CNG to remote plant locations. Image Credit: NGAdvantage

The ConAgg inudstry is quickly transitioning to this new fuel. Don't make the mistake of ignoring an important change that can add profit to your bottom line. ConAgg is a highly competitive business where small differences can have a huge impact.  Don't allow yourself to lose business because competitors are bidding jobs at a lower cost due and marketing themselves as a green operator. Take action. Get educated, determine where natural gas might fit in your operation, and get moving on your first project. Feel free to reach out to me with any questions you may have on implementing natural gas fleet programs. 

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Three Technologies that will Transform the the Natural Gas Fueling Industry

Fueling a fleet of vehicles with natural gas as opposed to gasoline or diesel fuel is often considered an innovative concept. In reality, it is just good business. Using a clean, affordable, domestically-produced alternative fuel makes sense. However, it is important to realize that, compared to the diesel fueling industry, natural gas vehicle (NGV) fueling is still relatively new. It has only been in the last decade that Compressed Natural Gas (CNG) and Liquefied Natural Gas (LNG) have secured a solid foothold in the US fleet industry.  

An IMW compressor, gas dryer, and storage system at a garbage truck fueling station. Image Credit: James Orsulak 

An IMW compressor, gas dryer, and storage system at a garbage truck fueling station. Image Credit: James Orsulak 

Natural gas vehicle programs are driven by economics. Lower fuel costs = increased profit margins and a distinct competitive advantage, but it comes with a few headaches. Both CNG and LNG stations require a good deal of maintenance compared to traditional liquid petroleum stations.  A diesel station is a simple liquid storage tank with a fuel pump and a dispenser.  A CNG station, by comparison, involves an industrial compression system powered by an electric engine. This is a substantial uptick in complexity, risk, and ongoing maintenance costs. If your station only has  a single compressor, a major catastrophic failure can leave you without fuel for some time. On the vehicle side we have fuel storage challenges. CNG vehicle storage systems are cumbersome and often add weight to the vehicle. Luckily, we live in age of technological innovation and progress. These challenges have not gone unnoticed by fuel providers and technology partners, who have been quietly sinking money into research and development to solve these problems.  Below are some of the advances that will be coming soon to a fueling program near you. 

1. 3D printing

3D printing, also known as additive manufacturing, is quickly gaining traction in the industrial sector. 3D printing is the opposite of traditional manufacturing, which is subtractive. If you need a steel part, traditionally you would start with a block of steel and then cut the piece out of the block. So we would be subtracting steel to get to the finished part. Additive manufacturing is the opposite. It uses a computer-generated 3D model of the part and then "prints" the object by laying down tiny layers of metal. The metal is applied as a powder (from the print cartridges) and is then fused together using a laser.  3D printing can now be done in plastics, metals, and even carbon fiber. The only limitations at this point are the size of the object. You obviously need a printer that is larger than the object you are trying to print, as seen here. 

Large-scale 3D printers can now print objects in plastic, metal, concrete, and even carbon fiber   Image Credit: metalworkingmagazine.com

Large-scale 3D printers can now print objects in plastic, metal, concrete, and even carbon fiber  Image Credit: metalworkingmagazine.com

3D printing has two primary uses. The first is rapid prototyping. 3D printing allows you to quickly generate numerous designs and quickly test the results in the real world.  It reduces the time and cost of finding the right solution.  NGV up-fitters can use this to test out different fuel injectors, hose clamps, or nozzles. A compressor manufacturer like IMW or ANGI, can use this technology to test out different compressor components on the fly. The result is better machinery that can brought to market much faster.  

An infinite variety of metal components can now be made using a  3D printer    Image Credit: Solid Concepts

An infinite variety of metal components can now be made using a  3D printer   Image Credit: Solid Concepts

The second use of 3D printing is on-demand manufacturing. Most fleets and fuel providers who have an on-site natural gas fueling station stock a large inventory of critical parts.  Some parts, such as those from discontinued compressor brands, can be very difficult to find.  3D printing gives us the ability to address this issue. An onsite printer can enable fleets and station providers to simply print parts as needed instead of ordering them. They can download the 3D model of the file and have it printed the same day instead of waiting a week or more for shipping.  A large variety of parts used in station maintenance are relatively simple plastics or metals, and can now be created with a 3D printer.   This technology will allow us to create better station components more quickly, while also giving us the ability to maintain stations with lower inventory costs.

2. The Industrial Internet and Predictive Analytics

Your CNG station called. It will fail tomorrow at 5pm. We will go ahead and fix it now. Image Credit:  Stephen Bowler via Flickr

Your CNG station called. It will fail tomorrow at 5pm. We will go ahead and fix it now. Image Credit: Stephen Bowler via Flickr

You may have heard of the Internet of Things (IoT). This is the practice of embedding tiny data-collecting sensors in everyday items such as your refrigerator or door lock. When we apply this concept to industrial applications, we call it the industrial internet.  General Electric, Cisco, Google, and a host of other tech giants are pioneering ways to collect, track, analyze and store data from almost any type of machine.  Compressors and LNG liquefaction equipment are perfect candidates for this technology, and many fuel providers are already incorporating this into their operations. So what can it do?  Imagine a compressor that can talk to station technicians in real-time, sending pressure, heat, and fill data by the minute. In a dual compressor setup, one machine can communicate with the other to optimize running hours and wear-and-tear on critical parts. Machines can actually stop catastrophic failures before they happen. Instead of a complete failure -- the system shuts down, informs the operations team, and tells them what parts are needed. The result will be cost savings and vast improvements in uptime. Future stations will be intelligent enough to optimize for temperature, electricity demand, and gas quality without guidance from their human caretakers. We are only limited by our imagination. GE's long term vision is for machines that will eventually be able to perform self-repair, a technology that is science fiction by today's standards, but will one day become reality. Ultimately big data is good data, and natural gas fueling stations are now generating huge amounts of it. The end result will be vastly improved station operations and reduced costs. A plus for fleets and consumers who are filling up with natural gas.

3. Adsorbed Natural Gas Storage Systems 

Activated carbon is commonly used as the enabling technology for adsorbed natural gas systems.   Image Credit: Wikipedia

Activated carbon is commonly used as the enabling technology for adsorbed natural gas systems.  Image Credit: Wikipedia

If you have followed the NGV industry for a few years, you have likely heard of Adsorbed Natural Gas (ANG) storage systems.  ANG is often referred to as the "holy grail" of gaseous fuel storage systems.  The basic idea is to store natural gas in a carbon honeycomb structure and eliminate the need for high pressure storage cylinders.  As the gas impacts the system, it is adsorbed into the material where it can be stored at a very low pressure in a solid form. This means we no longer need to use high pressure cylinders to store the fuel onboard the vehicle. This reduces weight and allows the storage to be custom molded into a huge variety of shapes and sizes. The real beauty of an ANG system is this: it is backwards compatible. ANG systems do not require the 3,600 pounds per square inch (psi) pressure needed for today's CNG vehicles, but...they can still use it.  An ANG-equipped vehicle can still use the existing CNG network to fill up. While it is true they could dramatically lower the required pressures for an onsite station, they would not be stranded by adopting the new technology -- an important advantage.  ANG systems can also be fueled using LNG. The LNG is simply vaporized and then adsorbed into the system. This gives the technology a clear, forward-looking advantage. Fuel providers could adapt in-step vs. having to retrofit all their existing stations. This would be a true game changer. Here is the latest: a company called BlackPak was awarded $4.6 million last March to further develop ANG technology.  The first commercial installations of ANG systems were installed in May by EnerG2 in the NW natural utility fleet. We will be following the demonstration tests closely!

The NGV industry is still maturing, meaning it is ripe for technological disruption. Keep an eye on these emerging innovations (and others) as they continue to play a role in shaping this growing industry. Don't be afraid to ask your fuel providers what they are working on behind the curtain so you can understand how it will benefit you and your fleet operation. 

CNG vs. LNG for Heavy Duty Trucks: Which One is Right for Your Fleet?

Speaking to fleets and truck dealers on a regular basis, it has become clear there is a large amount of confusion as to which form of natural gas is superior. Both Compressed Natural Gas (CNG) and Liquefied Natural Gas (LNG) are worthy fuels if you are need to improve your profitability and increase your competitive advantage by moving to a lower cost fuel. I will spoil the surprise by telling you upfront that neither of one of these is superior to the other. They are simply different, and different fleet operations have different priorities. Most natural gas fuel providers have only invested in one technology or the other. For example, Trillium specializes in CNG stations, and will tell you CNG is vastly superior. If you talk to Shell, they will likely pitch you on the benefits of LNG.  People sell what they know, and very few fueling companies in the industry (with the exception of Clean Energy) do both.  This creates a good amount of confusion for fleets trying to determine the best fit.  So what should you do? Simply evaluate your fleet priorities based on the information below and you can quickly decipher which fuel is best suited your needs. 

1. Introduction to CNG & LNG

Let's start with the basics. CNG and LNG are the same fuel, but stored in a different physical form on board your truck. CNG is a gaseous fuel that is lighter than air. CNG stations tap into the local gas utility lines and compress the gas up to 3,600 pounds per square inch (psi).  It is then dispensed into vehicles and stored in a high pressure storage cylinder that looks like this:

On tractor units, the CNG tanks are typically mounted on the frame rails, behind the cab, or a combination of the two, as seen below:

A Freightliner Cascadia powered by a 12L Cummins engine and equipped with an Agility Fuel Systems CNG storage system mounted behind the cab and on the frame rails

A Freightliner Cascadia powered by a 12L Cummins engine and equipped with an Agility Fuel Systems CNG storage system mounted behind the cab and on the frame rails

LNG is the same fuel, but it is stored in a cryogenic form.  At approximately -260 F, natural gas turns into a colorless, odorless liquid fuel. It is produced at an industrial processing facility and then trucked to the fueling station where it is stored as a liquid.  It is dispensed into vehicles at as a cryogenic liquid. 

2. Fuel Cost

CNG is almost always going to be less expensive than LNG. This is primarily due to the lack of transportation costs to get the fuel to the station. The CNG distribution system is already in place via our nation's natural gas pipeline system. This is not the case with LNG. LNG must be trucked into the station and is therefore more costly.  Costs can vary depending on where you are getting the fuel (onsite vs. retail station).  In general, you can expect to pay around $2.20 for a Diesel Gallon Equivalent (DGE) of CNG and closer to $2.50 for a DGE of LNG. Both fuels provide significant savings compared to diesel fuel, but CNG is typically going to be even more affordable.

3. Fueling Experience: Heat of Compression vs. Boil Off

The fueling experience is a bit different with each fuel. CNG is very similar to fueling with gasoline and diesel fuel.  It requires no special protective gear and minimal training.  There are two types of CNG stations, time-fill and fast-fill.  You can read about those in detail in our previous CNG station blog post here. CNG stations designed for trucking applications tend to be fast-fill, and they have a unique problem known as heat of compression. Heat of compression means that compressed gas shot into the fuel tanks at a high rate gets very hot. The CNG tanks account for this heat by allowing room in the fuel tanks for the gas to expand as it cools. This means if you are carrying 100 DGEs of fuel, you will likely only get about 80 usable gallons of fuel onto the vehicle. The problem is worse on a hot day and less noticeable in cold weather. This leads to a need to increase your fuel storage on-board the vehicle.  I will discuss the impacts of that below in the weight section. 

LNG is cryogenic liquid and therefore requires a bit more training as well as protective eye wear and gloves (see below). This may be a consideration if your fleet already has dedicated fueling personnel. This is not rocket science, it's just basic safety. Keep in mind diesel fuel is also highly toxic -- we are just used to diesel as a fuel because it is so prevalent. No fuel is safe enough enough to bathe in, except maybe solar.  

LNG is not compressed, and therefore it has no issues with heat of compression. Instead, it gets it own special issue -- boil off.  LNG is stored at -260 F and has a natural tendency to heat up.  As it heats up, it begins to boil in the tank and will eventually vent off. If you leave a fully fueled LNG vehicle in Las Vegas in the summer for two weeks, you will lose about 5% of your fuel.  In practice this is rarely a major problem. You don't normally fuel your trucks so you can leave them idle for two weeks. Your fleet is your workhorse, and if you're reading this article, you probably use your workhorses for a specific job.  If you a fueling your truck every day or two, you will not notice any major boil off issues. 

4. Fuel Economy

Regardless of how you are storing the fuel (CNG vs. LNG) , once the fuel hits the engine, it is a gaseous fuel. Speaking specifically about the current Cummins 12 L gas engine, fuel economy is going to be a bit lower when compared to a current diesel engine.  On a DGE basis, you can expect to see a 5-20% loss in fuel economy with natural gas in general. This is true with both CNG and LNG trucks. This impacts the final economics of the program, but it is typically not a deal killer.  As always, transmission choice, driver training, gearing, etc. will heavily impact the final fuel economy. You need to monitor drivers and attempt to improve this in the same way you do with you diesel fleet. You don't get a free pass just to ignore these details just because you are now using an alternative fuel. 

5. Weight, Range & Incremental Truck Price

The primary driver of the choice between CNG and LNG comes down to weight and range. You can simplify this entire evaluation by asking yourself this one question:

How sensitive is your operation to weight and how far do you need to go before refueling?  

Lets start with CNG. CNG cylinders are very safe and very strong due to their pressure requirements, but these attributes come with one downside: weight. Despite numerous advances in material sciences, CNG fuel systems continue to add significant weight to the truck when compared to a traditional diesel vehicle. You get to delete the Diesel Particulate Filter (DPF) and the Diesel Emission Fluid (DEF) system on the truck (which your maintenance team will love).  However, if you add 80 DGEs of CNG storage, you can expect to add at least 1,000 lbs of weight.  

Work closely with you dealer and the fuel tank manufacturer to get the exact weight difference between the diesel and CNG platform.  If your trucks have a shorter route and you only need 60 DGEs of fuel to get through the day, this may not be a major issue. If that is the case, then CNG is most likely the best fit. This is also good time to right-size your fuel storage spec. Most fleets these days carry WAY too much fuel.  I think this is a basic driver / range anxiety concern. Are you burning 50 gallons / day and carrying 100? Why? Don't carry fuel you don't need. You obviously want a buffer, but be realistic. Take this opportunity to actually determine the correct fuel storage spec.  You will need to make sure you account for the heat of compression factor we discussed above. If you are burning 50 gallons a day and will be using a fast-fill CNG station, a spec of 70-80 DGEs is very reasonable. 

This leads us to the final factor: incremental truck cost.  Natural gas trucks carry a premium over diesel units. The vast majority of the incremental cost of a CNG truck is due to the fuel tanks. They are expensive. A 100 DGE fuel storage system can easily add $70,000 to the truck price.  So again, make sure you have the right fuel spec nailed down.  If you have shorter routes, and right-size the fuel storage spec, you should see a payback period somewhere between 2-3 years.  Conversely, if you need 1,000 miles of range before refueling, you CAN do this with CNG, but is it cost effective? There are CNG storage systems well above 200 DGE available now.  But this will obviously add a lot of weight and a LOT of cost.  So if you find yourself looking at that option, it may be time to shift over to an LNG evaluation. 

LNG storage tanks are essentially highly insulated diesel tanks.  Fully loaded, they will weigh less than a comparable CNG system. They will also cost less in higher storage specs. For example, a 100 DGE storage system might be a $70,000 premium with CNG, but only $40,000 with an LNG system.  So you get the same basic range, with a lower incremental cost and a lower weight penalty. This may be worth the slightly higher fuel price of LNG. If you are extremely weight sensitive AND you have a long range route, LNG is worth a look. This why you see rail, mining, and marine vessels all going to LNG. They all have extreme range requirements and are incredibly sensitive to weight limits.   

Summary & Resources

I know this is a lot of information, but don't make it too complicated. Trucking firms and logistics providers no longer have the option of simply ignoring this transition. If you competition reduces their fuel cost by 40% and you do not, you lose and they win. Period.

If you have shorter routes and are not ultra weight sensitive, CNG is most likely going to be a better fit. Trash trucks, for example, are almost always CNG because they typically have short routes. CNG works well in this application and quickly improves profitability.  If you are running long routes and max out the weight each and every time, LNG needs to be in your evaluation. A good example might be a sand and gravel hauler running a 700 mile round trip before refueling. This is probably a good fit for LNG. I recommend starting with a CNG evaluation and determining if you would need to run additional routes to move the same amount of product.  If you do, then take a look at LNG and see if you can do it without additional routes.  Put your dealers to work for you and have them work up costs and weight comparisons on both options. Then put your fuel partners to work and take a look at fueling locations already available + onsite fueling options. You can typically justify a new fueling location with 25 trucks phased in over five years.   

For payback, below are links to both a simple payback on the incremental truck cost, as well as a much more advanced calculator that allows you to input the weight of the tractor and trailer.

Simple Payback Calculator

Advanced Payback Calculator 

The Alt Fuels Data Center is a great resource that can show you station locations, as well as financial incentives that may be available in your State. For example, Colorado has a $20,000 tax credit for heavy trucks natural gas trucks, as well as a grant that can supply an additional $22,000 per truck. ($42,000 per unit!)  They also have a 1,000 lb weight exemption for natural gas trucks, making CNG a VERY attractive option. Many other States such as Texas and Pennsylvania also have vehicle incentives currently available for natural gas truck purchases.  

Alt Fuels Data Center Fueling Locations

Alt Fuels Data Center Incentives By State

If you need help during these evaluations don't hesitate to contact me. I am happy to help answer any questions you may have. 

Ready for an On-site CNG Station? Five Questions to Get you Started.

You have decided it's time to add an on-site Compressed Natural Gas (CNG) fueling station. Good choice. The United States is awash in abundant natural gas. The affordable, domestic and low carbon fuel is quickly replacing diesel and gasoline in fleet operations around the country. The choices and information available can be overwhelming. I have been involved in more than 30 CNG installations and here is my advice -- keep it simple. You can quickly prepare yourself to meet with potential vendors and partners by using the following questions to develop a CNG station development checklist. 

1. Who is going to use the station and how much fuel do they need?

This is the first question to consider when beginning a CNG evaluation. What types of vehicles are going to use the fueling station? How much fuel (approximately) will each vehicle need?  

Most stations sell fuel either in Gasoline Gallon Equivalents (GGEs) or Diesel Gallon Equivalents (DGE).  Each of these units is equal in energy content to their liquid petroleum counterparts. You do not need to go beyond these metrics. Gas compressors are rated in Standard Cubic Feet per Minute (SCFM), and SCFM can be translated into GGE or DGE production capacity.  You can simplify the picture by keeping all capacity ratings in GGEs or DGEs.  Any station designer will be well versed on either one of these metrics. I recommend using the one that is most common to your customer base.  If the users are primarily pumping gasoline today, use GGEs.  If they are a heavy duty fleet using diesel every day, use DGEs.  A few examples have been included below. 

25 CNG pickup trucks x 8 GGE / Day = 200 GGE / Day

20 CNG Trash Trucks x 35 DGE / Day = 700 DGE / Day

50 Heavy tractors x 80 DGE / Day = 4,000 DGE / Day 

Answering this question is at the heart of a CNG station's size. There are numerous compressor options on the market, each with a different capacity. Knowing the fuel requirement will allow you to craft your station specifications for vendor proposals. You want to size the station for what you anticipate the demand will be in year five of the program.  Stations can always be upgraded, but obviously there is a cost in doing so. You will want to strike a balance between the station capacity and capital costs.  

2. When will the vehicles fuel?

The next step in your evaluation is to determine WHEN the vehicles will fuel. CNG stations can be designed in one of three ways: fast-fill, time-fill or a combination of the two. Fast-fill stations dispense fuel between 5-20 gallons per minute, similar to gasoline and diesel stations.  Most public access CNG stations are designed to fast-fill vehicles. If a fast-fill design makes sense, take a look at the peak fueling hours and determine how quickly each vehicle will need to fuel to keep your customers happy.  In the pickup truck example above, you will need a system that produces 200 GGE / day.  If all of these vehicles will show up after work between 5pm - 7pm, then the station needs to produce at least 1.6 GGEs per minute to ensure this will work (200 GGEs / 120 minutes = 1.6 GGEs / minute). Faster fueling times are certainly an option, but this gives you an idea of the minimum requirement. 

Fast-Fill CNG Station 

Fast-Fill CNG Station 

The second design is an overnight time-fill station. These stations are typically used when a fleet returns to a central base each night and the vehicles are parked overnight. Time-fill stations are attractive due to lower equipment costs. You can spread the fueling capacity over a larger window of time to reduce the size (and therefore cost) of the compression system. With a time-fill system you will look at the number of hours the vehicles have to fuel vs. minutes.  In our trash truck example above, we need 700 DGEs of fuel each day.  If the vehicles are parked and idle for eight hours, we can simply divide 700 DGEs by eight hours to get 87.5 DGEs per hour as our station specification.  

Republic Services Time-Fill CNG Station 

Republic Services Time-Fill CNG Station 

The final design is a combination station. Combo-stations typically have a secured private time-fill area and a separate fast-fill dispenser as well. Combination stations are a good fit if you have your own fleet of vehicles parked overnight, but you also want to retail fuel to third parties. You can do both while keeping your own fueling operations separated and secured. Once you evaluate when the fueling will occur and what design type is most appropriate, you can move to the next question.  

3. What is the gas pressure at the location?

A CNG station is powered by a gas compressor. That compressor will tap into the local utility gas line in the street, which is (typically) going to be at a pressure between 5 - 60 pounds per square inch (psi).  The compressor will take that pressure all the way up to 3,600 psi, which is the pressure rating of most CNG vehicles. One of the most important factors the station designers will need is the inlet gas pressure. To obtain this, you can call the local natural gas utility, ask for the builders' call line, give them the address, and ask them what the maximum gas inlet pressure would be for a CNG station.  

4. Do you need redundancy?

CNG stations with multiple compressors that can supply fuel even when a single unit is offline are considered redundant. This means if a compressor is taken offline for maintenance or has a failure of some form, the station can still supply fuel to vehicles.  The primary consideration for redundancy is what will happen to your customers if the station is down for a few hours?  If there are other stations nearby, it may be advisable to install a single compressor.

If the station is a sole fueling outpost for mission critical fleet vehicles, redundancy may be a better choice.  It is important to look at what each of the compressors can handle (e.g. how many GGEs per minute or hour they can produce).  Station redundancy is summarized as a percentage.  A 100 percent redundant station can still meet the exact fueling requirements even with an entire compressor offline.  A 50 percent redundant station can still provide fuel, but only at half the capacity...and so on. If a station design has two small compressors that need to run 23 hours a day to meet your fuel requirement, this is not a redundant station (or a good solution).  One unit cannot handle the job alone, and if both units are running all day, they will fail regularly. A 100 percent redundant design also has the added benefit of a longer life cycle because the compressors can be alternated. This means each machine racks up fewer running hours each day and will therefore last longer. 

5. How will you maintain the station?

One of the greatest misconceptions in the CNG fueling industry is that stations are easy and simple to maintain. This is simply not true. A station needs love and care just like any major mechanical investment.  Properly maintained, a CNG station can easily see 25 years of life or more. Improperly maintained machinery will quickly become a nightmare. A vendor who tells you it is easy and you can do it yourself with minimal training is looking for a quick buck. These are "turn and burn" station installers. Avoid them. A CNG station has a variety of systems and parts that will require both regular and preventative maintenance, as well as scheduled overhauls and intermittent emergency repairs. Most compressors come with a warranty to cover the system for at least a year, but it is prudent to have a plan in place by the time you open the station. 

There are typically three options you can consider to maintain the station. The first is to get trained and certified to do it yourself.  If you or members of your staff are experienced with high pressure gas systems, this may be an option. Most manufacturers offer training programs to get certified with specific compressors. However, this is typically expensive and will require the overhead (salary, benefits, insurance, etc.) necessary to keep someone on staff to handle preventative maintenance and repairs on a regular basis. Many oil and gas companies maintain their own stations because they have extensive expertise with compression systems. 

The second option is a traditional time and materials program. Several vendors offer programs that include monthly inspections and preventative maintenance. They will also be available for emergency repairs. You will typically pay a monthly fee for the regular inspections, and then sign off on each purchase order for time and materials as needed. If you keep capital on-hand for ongoing facility and site repairs, then this type of pay-as-you-go maintenance plan may be a good fit.  

The final option is referred to as an Operations & Maintenance (O&M) plan. This is typically a no-risk maintenance option where you pay an all-inclusive fee for a vendor to take on financial risks and costs associated with the station. The vendor will install remote monitoring (typically a broadband connection) at the station. This will give them access to do remote diagnostics and restarts. It will also allow them to respond to station outages in real time.  Remote monitoring eliminates the need for a phone call or email from a customer telling them the site is down. They will handle all preventative maintenance, repairs and even full replacements if necessary. O&M programs are typically charged by the gallon. Industry costs range from $0.15 to $0.50 per gallon for most O&M programs and will vary based on the station and the fuel throughput.  In return, most vendors will ask for minimum volume guarantee to ensure they have an opportunity to recoup their costs and make a profit. This option is attractive as it can be built directly into your fuel price and is easily forecasted. It also removes the burden of unforeseen repair costs and late night repair calls. 

With this information in hand, you can easily draft a solicitation for equipment and installation of your CNG station. Answering these questions will prepare you to easily evaluate different equipment options, construction costs, and maintenance offerings. If you need a list of station vendors to get you started, I recommend the NGV America business directory, which can be found here. Good luck!