PNG, LPG and CNG which Gas is Better Cooking and Gas Conversion Guides

Author: Dr. Sharad Pachpute (PhD., IIT Delhi)

Selection of Natural Gas for Cooking

• The choice between CNG (Compressed Natural Gas), PNG (Piped Natural Gas), and LPG (Liquified Petroleum Gas) for cooking depends on several factors, including availability, cost, safety, and environmental considerations.
• When selecting a gas for cooking, there are several options available, each with its own advantages and considerations.
• The most common types of gas used for cooking are Natural Gas (including Piped Natural Gas or PNG) and Liquefied Petroleum Gas (LPG). Here’s a comparison to help you make an informed decision:

Natural Gas (Piped Natural Gas – PNG)

• PNG stands for piped natural gas, which is a pollution-free fuel that is supplied directly through pipes. 
• PNG is mainly methane (CH4) with a small percentage of other higher hydrocarbons.
• Advantages:
  • Continuous Supply: PNG is supplied through pipelines, ensuring a continuous and uninterrupted gas supply.
  • Convenience: No need for manual refills or handling of gas cylinders, as gas is delivered directly to the kitchen.
  • Cost-Effective: Can be more cost-effective in the long run, especially in areas with well-developed PNG infrastructure.
  • Cleaner Burning: Natural gas is a cleaner-burning fuel compared to other fossil fuels, resulting in lower emissions.
• Considerations:
  • Availability: PNG availability depends on the infrastructure in your area. Not all locations may have access to PNG.
  • Installation: Installation of PNG pipelines and meters may require upfront costs and professional assistance.

Liquefied Petroleum Gas (LPG):

• Advantages:
  • Portable: LPG is stored in cylinders, making it portable and suitable for areas without PNG infrastructure.
  • Availability: Widely available and can be used in locations where PNG is not accessible.
  • Immediate Installation: No need for infrastructure development; installation involves placing and connecting gas cylinders.
• Considerations:
  • Refills: Regular refills are required as gas cylinders have limited capacity.
  • Handling: Handling of gas cylinders involves manual labor and transportation, which can be inconvenient.
  • Safety: Proper storage and handling practices are essential to prevent accidents or gas leaks.
• When deciding between PNG and LPG for cooking, consider factors such as availability, convenience, cost, environmental impact, and safety.
• If PNG is available in your area and meets your requirements, it can offer a convenient and cost-effective solution with fewer logistical challenges compared to LPG.
• However, if PNG is not available or if portability is a priority, LPG may be a suitable alternative.
• It’s advisable to consult with gas providers or experts to assess the best option based on your specific needs and circumstances.

CNG (Compressed Natural Gas)

• Advantages:
  • It is a cleaner-burning fuel compared to LPG, producing fewer greenhouse gas emissions.
  • CNG is generally more cost-effective than LPG in areas where it is readily available.
  • It is safer than LPG because CNG is lighter than air and disperses quickly if leaked.
• Considerations:
  • Availability can be limited, as not all areas have CNG infrastructure in place for residential use.
  • Initial setup costs, including installing CNG pipelines and appliances, can be higher.

PNG (Piped Natural Gas)

• Advantages:
  • Continuous and uninterrupted gas supply as it’s delivered through pipelines.
  • Convenient and eliminates the need for manual cylinder refills.
  • Cost-effective in the long run for areas with established PNG infrastructure.
• Considerations:
  • Availability is limited to areas with PNG pipelines, which may not cover all regions.
  • Initial installation costs and connection fees may apply.

Steps to Convert LPG to PNG

• Converting from LPG (liquefied petroleum gas) to PNG (piped natural gas) typically involves connecting your property to an existing natural gas pipeline network.
• Here’s a general guide to help you understand the process:

1. Check Availability:
   • First, ensure that piped natural gas (PNG) is available in your area.
   • Not all regions have access to natural gas pipelines, so check with your local gas utility company.
2. Contact the Gas Utility Company:
   • Get in touch with the gas utility company that serves your area.
   • They can provide information about the availability of PNG
   • The process of connection, and any permits or approvals required.
3. Site Assessment:
   • The gas utility company will conduct a site assessment to determine the feasibility of connecting your property to the natural gas pipeline network.
   • They will consider factors such as proximity to gas mains, property layout, and safety considerations.
4. Obtain Necessary Approvals:
   • Depending on local regulations, you may need to obtain permits or approvals from relevant authorities before proceeding with the conversion.
   • This could include building permits, environmental clearances, or safety certifications.

     
5. Installation of Gas Meter and Piping:
   • Gas Meter Installation: The gas utility company will install a gas meter on your property to measure your natural gas usage.
   • Piping Installation: If your property is not already equipped with natural gas piping, the gas utility company will install underground pipes to connect your property to the gas main.

     

6. Safety Considerations: Ensure that all safety precautions are followed during installation. This may include pressure testing of gas lines, installation of safety valves, and compliance with building codes and standards.
7. Appliance Conversion or Installation: If you have existing LPG appliances, they may need to be converted to work with natural

LPG (Liquified Petroleum Gas):

• Advantages:
  • LPG is widely available and can be used in areas without access to natural gas pipelines.
  • It provides a consistent and reliable energy source for cooking.
  • LPG appliances are generally more affordable and widely available.
• Considerations:
  • It produces more carbon emissions compared to CNG.
  • LPG is heavier than air and can accumulate in poorly ventilated areas if there’s a leak, posing a fire or explosion risk if not handled properly.

Comparison of cost for CNG, PNG, LPG

• The cost comparison between CNG (Compressed Natural Gas), PNG (Piped Natural Gas), and LPG (liquid petroleum Gas) can vary significantly depending on several factors such as location, infrastructure availability, market rates, and government subsidies.
• Here’s a general overview of the cost comparison for these natural gas options:
• As of September 2023, piped natural gas (PNG) is priced at ₹51 per unit in Thiruvananthapuram, and customers can save 15-25% on costs compared to LPG cylinders.
• For example, CUGL charges ₹57.00 per SCM in Kanpur, Bareilly, Unnao, and Jhansi. In April 2023,

CNG (Compressed Natural Gas):

• Cost Factors:
  • CNG prices are typically lower compared to LPG in areas where CNG infrastructure is well-established.
  • Pricing may vary based on regional gas prices, transportation costs, taxes, and subsidies.
• Cost Comparison:
  • CNG is often considered more cost-effective for cooking compared to LPG where CNG refueling stations or pipelines are readily available.
  • However, initial setup costs for installing CNG-compatible appliances and infrastructure may be higher.

PNG (Piped Natural Gas):

• Cost Factors:
  • PNG prices are usually competitive and may be lower than LPG in areas with established PNG infrastructure.
  • Costs can vary based on local distribution charges, connection fees, usage rates, and government policies.
• Cost Comparison:
  • PNG is generally cost-effective for cooking where pipelines are available, as it eliminates the need for manual cylinder refills and offers continuous supply.
  • Initial installation costs and connection fees may apply but can be offset by long-term savings.

LPG (Liquified Petroleum Gas):

• Cost Factors:
  • LPG prices can fluctuate based on global oil prices, transportation costs, taxes, and subsidies.
  • Pricing may vary between branded and non-branded LPG suppliers.
• Cost Comparison:
  • LPG is widely available and can be used in areas without natural gas infrastructure, but it may be relatively more expensive compared to CNG and PNG in some regions.
  • The cost includes cylinder refilling charges, delivery charges, and possibly higher fuel costs per unit compared to CNG and PNG.

Overall Cost Comparison:

• CNG and PNG are often considered more cost-effective options for cooking where infrastructure is available, offering competitive pricing and potential long-term savings.
• LPG is a reliable choice for areas without CNG or PNG infrastructure but may incur higher costs, especially if there are frequent price fluctuations in the global oil market.
• Piped Natural Gas (PNG) is around three percent (3%) costlier compared to subsidised Liquefied Petroleum Gas (LPG) as per the data Business Standard analysis.
• This is despite the recent 8%  lower in natural gas prices to 4.66 per Million British thermal units (MMBtu) by the government, which pulled down the price of PNG.
• Before the reduction, PNG was around  5% more expensive than subsidized LPG.
•  Compressed Natural Gas (CNG) has around 25-30 %  cheaper than diesel after the reduction in natural gas
  • Domestic CNG price (Rs/scm) : 38.15 or 61 Rs / KG
  • CNG Heating value: 9,500 Kcal/scm

Comparison of Heating Values or CNG, PNG, LPG

• The heating value of a fuel refers to the amount of heat energy released when a specific quantity of the fuel is burned completely.
• This value is typically measured in British Thermal Units (BTUs) per cubic foot or Megajoules per cubic meter.
• Here’s a comparison of the heating values for CNG (Compressed Natural Gas), PNG (Piped Natural Gas), and LPG (Liquified Petroleum Gas):
  • CNG (Compressed Natural Gas):
    • Heating Value: Approximately 1,030 BTUs per cubic foot or 38.6 Megajoules per cubic meter.
    • CNG primarily consists of methane, which has a high heating value and is considered a clean-burning fuel.
  • PNG (Piped Natural Gas):
    • Heating Value: Similar to CNG, approximately 1,030 BTUs per cubic foot or 38.6 Megajoules per cubic meter.
    • PNG is also composed mainly of methane and has a comparable heating value to CNG.
  • LPG (Liquified Petroleum Gas):
    • Heating Value: Higher than CNG and PNG, approximately 2,500 to 2,800 BTUs per cubic foot or 93.2 to 104.5 Megajoules per cubic meter.
    • LPG consists of propane or butane, which have higher energy content per unit volume compared to methane.

Comparison of Heating Values:

• LPG has a higher heating value per unit volume compared to CNG and PNG. This means that LPG can generate more heat energy when burned, making it more efficient in terms of heat output.
• CNG and PNG, while having lower heating values than LPG, are still efficient and clean-burning fuels suitable for various applications, including cooking and heating.

Considerations:

• Despite the higher heating value of LPG, factors such as cost, availability, infrastructure, safety, and environmental considerations also play a crucial role in choosing the most suitable natural gas option for cooking.
• CNG and PNG are often preferred for their lower emissions, cost-effectiveness (where infrastructure is available), and safety features, while LPG is commonly used in areas without natural gas pipelines or for portable applications.

Scope of CFD for  Efficient Gas Burner Design

• Computational Fluid Dynamics (CFD) is a powerful tool for designing and optimizing gas burners.
• CFD significantly expands the capabilities of engineers in designing gas burners by providing detailed insights into flow dynamics, combustion behavior, heat transfer, and emissions, leading to more efficient and environmentally friendly burner designs.
• You can estimate the gas flow rate for your applications.
• Here’s how CFD can be utilized in this context:

1. Flow Analysis:
   • CFD allows engineers to simulate the flow of gases within a burner system.
   • This includes understanding how the fuel and air mix, how they move through the burner assembly, and how they behave within the combustion chamber.
   • By analyzing these flows, engineers can optimize the design for better mixing, reduced pressure losses, and improved combustion efficiency
2. Burner FLame Modeling:
   • CFD can simulate the combustion process itself, including chemical reactions and pollutant formation.
   • Engineers can study parameters like flame temperature, residence time, and species concentrations to optimize combustion for desired outcomes such as maximum heat release, reduced emissions, or specific flame characteristics..
3. Emission Prediction:
   • CFD can predict emissions such as nitrogen oxides (NOx), carbon monoxide (CO), and unburned hydrocarbons.
   • By modeling combustion chemistry and flow dynamics, engineers can assess the impact of different burner configurations and operating conditions on emissions. This information is valuable for meeting regulatory requirements and designing environmentally friendly burner systems.
4. Burner Design Optimization:
   • One of the key benefits of using CFD for gas burner design is the ability to iterate rapidly through different design configurations.
   • Engineers can simulate various design alternatives, and evaluate their performance metrics (e.g., efficiency, emissions, temperature profiles)
   • Identify optimal designs without the need for extensive physical prototyping.

• The following figure shows the CFD modeling of LPG gas burner for design of new gas burner

Summary

• The choice between CNG and LPG for domestic cooking depends on factors such as availability, cost, safety considerations, and environmental preferences.
• Users often consider the local infrastructure, cost-effectiveness, safety regulations, and environmental impact when making this decision.
• When selecting a natural gas option for cooking, it’s essential to evaluate not only the heating value but also the overall suitability based on your specific needs and circumstances
• It’s essential to check local gas prices, subsidies, and infrastructure availability to determine the most cost-effective natural gas option for cooking in your specific location.