Which of the following scenarios is an example of cogeneration?

Cummins Newsroom: Education

Compared to diesel and gasoline vehicles, natural gas engine vehicles pollute less, have a smaller carbon footprint, and use a fuel that doesn’t present any risk of soil or water contamination. Surely, these environmental benefits of natural gas engines must come at a cost premium, right?

For many applications, the opposite is true. A natural gas truck is more expensive than a diesel truck, but fleet operators who switch to natural gas vehicles generally experience economic benefits in the long run, in addition to enhancing the sustainability profile of their business.

Cost savings through low, stable natural gas fuel prices

The first source of savings is the fuel itself. In the United States, natural gas retail prices are, on average, significantly lower than the retail price of both gasoline and diesel. This has been true for the past 20 years. The price of natural gas is also stable and disconnected from the price of petroleum fuels. For companies operating who do not have the option to adjust the price of their services to reflect rising fuel prices, the stability of natural gas prices is a major benefit. Public transit authorities, for example, cannot easily increase the price of bus tickets. Operating natural gas buses helps them avoid experiencing financial hardships every time the price of diesel or gasoline goes up.

As of the end of 2021, the average retail price of diesel in the United States was $3.10 per gallon gasoline equivalent; in comparison, the price of compressed natural gas (CNG) was $2.33 per gallon gasoline equivalent. At these prices, a truck that uses 10,000 gallons of fuel per year would save $7,700 each year by running on CNG.

Reduced maintenance costs with natural gas engines

Fuel cost savings are only one part of the equation. Natural gas vehicles also require less maintenance than diesel vehicles equipped with aftertreatment systems. This is significant due to the complexity of the aftertreatment systems required to meet current emissions standards, particularly in the United States. These systems require a lot of preventative maintenance, such as changing filters. Adding up the cost of repairs, consumables, maintenance and downtime for maintenance, maintaining a modern aftertreatment system can cost several thousand dollars per year. With natural gas vehicles, which have much simpler aftertreatment systems, these costs are almost entirely eliminated.

These maintenance aspects are important considerations while evaluating when to switch to natural gas engines.

Incentives could also offer economic benefits for natural gas engines

Abundant government incentives are also available for businesses who want to invest in natural gas vehicles. In the United States, almost every state provides incentives, ranging from high occupancy vehicle (HOV) lane use and parking privileges, to grants designed to fund fueling infrastructure projects, to discounts on natural gas purchases. At the federal level, substantial tax credits are available. For example, a tax credit of $0.50 per gallon gasoline equivalent has been available throughout 2021 for CNG and liquified natural gas (LNG) use. This amounts to an effective reduction of more than 20%, or $5,000 per year for a vehicle which uses 10,000 gallons of fuel per year. (The credit expired in 2021, but extension bills for 2022 are in the legislative pipeline.)

Driver and operational savings associated with natural gas engines

There are other soft savings associated with operating natural gas vehicles. For example, operators of CNG vehicles who choose to install a “time-fill” fueling system on their premises can save labor hours. “Time-fill” systems slowly fill CNG tanks overnight. At the end of the day, drivers park their vehicle at a fueling point, connect a fuel nozzle to the vehicle and go home. Compared to waiting for their turn at the gas pump, and then waiting several minutes to fill their tank, drivers save time, and their company saves money. Drivers and mechanics also report they enjoy working with natural gas engines compared to diesel engines. They are quieter, cleaner, and don’t cause anyone to leave work smelling of diesel fuel. In some cases, these quality-of-life improvements can lead to lower staff turnover, and thus lower costs associated with training and recruitment.

Businesses whose operations allow them to see savings across these cost categories can quickly recoup the initial investment in natural gas vehicles. Switching to natural gas vehicles may not be for everyone, but for many businesses, investing in natural gas vehicles is a smart financial move.

If these benefits sound interesting to you, don’t forget to also check our answers to frequently asked questions about natural gas engines. These answers cover topics such as cost, practicality, and feasibility of integrating natural gas into commercial fleets.

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Cummins Newsroom: Education

It can be difficult to grasp the role natural gas engines play when it comes to reducing transportation emissions and making the trucking industry more sustainable. Natural gas is a fossil fuel, just like diesel and gasoline, so there are some misconceptions about the environmental benefits it can provide, particularly when compared to emerging alternative powertrain options like hydrogen fuel cell or battery electric vehicles (BEV). Both fuel cell and BEV vehicles are often referred to as “zero emission” options. While it’s true they don’t produce any tail pipe emissions, that only tells part of the sustainability story.

What makes natural gas an environmentally friendly fuel?

Like diesel engines, natural gas engines are internal combustion engines. They all release some level of greenhouse gas (GHG) emissions, but for the same number of miles driven, a natural gas vehicle usually results in a lower overall amount of GHGs and particulate matter like carbon dioxide (CO2) and nitrogen oxides (NOx), while delivering similar power and performance.

One way to compare the overall greenhouse gas and carbon intensity of fuels such as natural gas, renewable natural gas, and diesel, and vehicles is to look at a metric called well-to-wheel emissions. Well-to-wheel emissions include the total GHG emissions generated from the use of the fuel and the production and transportation or generation of the fuel.

Natural gas engines lower GHG emissions

When looking at the total well-to-wheel impact of compressed natural gas (CNG) and diesel, CNG delivers GHG reductions somewhere in the range of 13% – 17%. The CO2 numbers are even better, with an average reduction of 25% or more.

Cummins’ GHG Emissions Calculator provides an analysis of the well-to-wheels emissions of medium and heavy-duty vehicles based on the typical fuels available in North America. The GHG Emissions Calculator is based on detailed lifecycle models developed by researchers at the Argonne National Laboratory. In most medium and heavy-duty applications, a natural gas engine can result in well-to-wheel greenhouse gas emissions lower than an equivalent diesel engine. For example, a transit bus equipped with Cummins’ L9N natural gas engine can result in about 6% less greenhouse gas emissions than the same truck equipped with a diesel engine. If the natural gas bus replaces an older diesel bus, greenhouse emissions reductions can be even greater—13% or more.

Environmental sustainability and renewable natural gas

The sustainability impact of natural gas really shines when you factor in renewable natural gas (RNG). Renewable natural gas is manufactured primarily using methane that comes from the decomposition of organic waste. This can include landfill gas or methane captured from wastewater treatment facilities or agricultural waste.

Using RNG brings the total carbon intensity score down, because RNG is made with methane that would have otherwise been off gassed. Capturing those gases prevents them from entering the atmosphere and reduces the total well-to-wheel score significantly. It can even drop the carbon intensity to below zero depending on the RNG feedstock. Renewable natural gas is functionally identical to natural gas obtained from fossil resources. Blending fossil natural gas with even small quantities of RNG can result in immediate environmental benefits. And every year RNG becomes a bigger percentage of all CNG being used in North America, contributing towards the role natural gas to play in our renewable future.

Reducing criteria air emissions with natural gas engines

Reduced greenhouse gas emissions are only part of the equation. Natural gas vehicles also help to reduce air pollution. More accurately, natural gas vehicles cause less air pollution without the need for complicated aftertreatment systems designed to scrub pollutants from a vehicle’s exhaust. Natural gas engines are certified at near zero low NOx levels (0.02g/bhp-hr) and release minimal amounts of harmful volatile organic compounds (VOCs) like benzene. When a large fleet replaces older diesel vehicles with natural gas engines, these benefits can have an immediate positive local impact on air quality. This is one of the reasons why natural gas vehicles are especially popular in urban areas, and why transit buses and refuse trucks are among the most common examples of natural gas engines on trucks and buses.

No environmentally harmful spills

From an environmental standpoint, compressed natural gas has one additional advantage over petroleum fuels. Unlike oil and oil distillates such as diesel and gasoline, natural gas is, well, a gas. This means that if a leak occurs, any natural gas that escapes will almost instantly dissipate in the atmosphere. Leaking natural gas into the air is not without environmental impact. But it is always preferable to spilling liquid hydrocarbons, which can lead to ground and water contamination. Countless gas stations all over the world, leaky underground gasoline tanks at countless gas stations have caused significant soil contamination. With natural gas, this is not a problem.

Natural gas, in summary, may not be the only solution to man-made pollution in the transportation sector, but it has a role to play when it comes to reducing emissions now without major disrupts to current business models. Hydrogen engine powered vehicles, for example, have little to no emissions, but from an economic standpoint, they are still more expensive to operate. Until hydrogen becomes more affordable and more available, natural gas solutions are a great way to achieve immediate environmental progress. There are other benefits of natural gas engines in transportation, particularly when it comes to financial benefits of natural gas engines.

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Cummins Newsroom: Education

What are "well to wheel" emissions? We answer your questions about a topic that's on everyone's radar as the world continues its march to a zero emissions future. 

The first phases of greenhouse gas regulations for commercial vehicles focused on tailpipe emissions, and this perspective brought the industry many efficiency improvements. With the advent of low to zero carbon fuels and new power sources, like battery electric powertrains that get their energy from charging via the electric grid, differences in GHG emissions are more difficult to assess. 

What is well to wheel efficiency and emissions? 

Regulators targeting reductions in GHG emission realized that both the amount of fuel or energy source, and GHG emissions associated with the production, processing, distribution, and use of the fuel, needed to be quantified. This was the advent of well to wheel comparison. 

Well to wheel is the most complete and accurate way to evaluate efficiency and emissions, considering the entire energy consumption and all greenhouse gas emissions of the complete life cycle of an energy source.

Well-to-wheel vs tank-to-wheel emissions

While well to wheel emissions consider the GHG emissions generated during the entire lifecycle of a fuel, the term tank-to-wheel is a subset of well to wheel, referring to the use of a power source during operation only. These are the tailpipe emissions that were once the cornerstone of regulation and assessment but can no longer tell the whole emissions story.

For example, the bar chart shows tank to wheel and well to wheel annual GHG for the line-Haul truck application. From a tank to wheel perspective, the BEV powertrain has zero emissions, and would be considered better than most ICE options fueled by diesel. Running on a renewable biofuel shows no benefits with this measure. The lower bar of the hybrid configuration shows that efficiency improvements provide GHG emissions reductions, as well.

The comparison between the powertrain options looks different when compared on a well to wheel basis. Here, the important factor is that there are GHG emissions associated with producing, transporting and distributing, and using each of these fuels.

First, notice that the ICE bar is taller. This increased height accounts for petroleum extraction, transportation, refining and distribution. With these additional considerations, the BEV bars are now non-zero. For example, if ‘average electricity’ from across the US were used to power the truck, the GHG emissions from ICE with diesel is actually lower than BEV. If greener electricity from California were used, BEV shows reduced GHG emissions over a fossil fueled diesel engine but are still non-zero.

The benefits of running on a renewable fuel (Biofuel) are much clearer when considered on a well to wheel basis. In our example, biofuels provide the highest reduction in GHG emissions, but the height of the hybrid diesel bar is similar to that of BEV in California. This indicates that higher performance ICE-based powertrains can provide substantial GHG benefits.

Technologies to lower well-to-wheel emissions 

When it comes to lowering GHG, it’s not a matter of which technology is better — but rather which is more suitable to a specific set of conditions and needs. We have to consider range, weight, downtime, performance requirements, customer economics, and related infrastructure to provide the best options for the market. This is why a company like Cummins is working to develop and improve multiple technologies for myriad applications.

Advanced diesel engines provide significantly improved fuel economy and feature after-treatment systems, resulting in a reduction of GHG. You can find advanced-diesel engines in many applications ranging from line-haul and regional-haul trucking to construction and agriculture applications.

Fuel-agnostic engine platforms can offer customers the option to select the right fuel to get the job done with minimal to no output of GHG emissions for a specific situation.

Low- and zero-carbon fuels can be used as an alternative to traditional fossil fuels in many applications. These fuels show a marked reduction in GHG in many different sections of the well to wheel lifecycle. Renewable diesel, for example, merely returns carbon to the atmosphere—the same carbon atoms that the source plants used from the atmosphere. Some of these fuels, such as renewable natural gas (RNG), can even deliver sub-zero emissions.

New power technologies such as battery, fuel cell and hydrogen produce no carbon dioxide while in use, but well to wheel emissions help to show us the full picture of their best and most useful applications.

Beyond ‘well to wheel’: other lifecycle considerations 

Well to wheel emissions analysis gave manufacturers and regulators a more holistic view of the fuel lifecycle, but new technologies have brought further considerations even outside this purview.

Raw material extraction and battery production can result in significantly more GHG emissions than the production and use of internal combustion engines. Batteries that power electric vehicles will, eventually, reach the end of their life, and both recycling and “second life” options are being explored and refined.  

As technology becomes more and more advanced, these “cradle to grave” considerations may replace well to wheel as the driving force toward a zero emissions future.

Cummins Newsroom: Education

The centralized power grid may fail but your standby power system should not. With the changing climate and an outdated centralized power grid, the importance of emergency power systems continues to grow. This in turn has increased the need for a highly reliable standby power systems solution. 

Join Cummins Power Generation’s free upcoming webcast with Consulting-Specifying Engineer on February 17th for a comprehensive overview of fundamental control features needed to parallel generator sets together and with the electrical grid. Traditional switchgear paralleling is reviewed and compared with the integrated paralleling controls that use distributed logic architecture to help you specify a reliable paralleling system. This course can be attributed to continuous learning credits as attendees qualify for a Certificate of Completion.

This informative seminar will be led by our Global Technical Advisor, Hassan Obeid. Hassan has been with Cummins since 2007 in a variety of roles encompassing power systems design engineering, project engineering and application engineering. His passion for solving a wide range of complex technical problems led him to design several crucial power systems components such as switchgears, controls, paralleling, transfer switches, generator sets and digital solutions for a variety of power system applications. 

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