Types of Biogas Storage Systems

Selection of an appropriate biogas storage system makes a significant contribution to the efficiency and safety of a biogas plant. There are two basic reasons for storing biogas: storage for later on-site usage and storage before and/or after transportation to off-site distribution points or systems. A biogas storage system also compensates fluctuations in the production and consumption of biogas as well as temperature-related changes in volume.

There are two broad categories of biogas storage systems: Internal Biogas Storage Tanks are integrated into the anaerobic digester while External Biogas Holders are separated from the digester forming autonomous components of a biogas plant.

The simplest and least expensive storage systems for on-site applications and intermediate storage of biogas are low-pressure systems. The energy, safety, and scrubbing requirements of medium- and high-pressure storage systems make them costly and high-maintenance options for non-commercial use. Such extra costs can be best justified for biomethane or bio-CNG, which has a higher heat content and is therefore a more valuable fuel than biogas.

Low-Pressure Biogas Storage

Floating biogas holders on the digester form a low-pressure storage option for biogas systems. These systems typically operate at pressures below 2 psi. Floating gas holders can be made of steel, fiberglass, or a flexible fabric. A separate tank may be used with a floating gas holder for the storage of the digestate and also storage of the raw biogas. A major advantage of a digester with an integral gas storage component is the reduced capital cost of the system.

The least expensive and most trouble-free gas holder is the flexible inflatable fabric top, as it does not react with the H2S in the biogas and is integral to the digester. These types of covers are often used with plug-flow and complete-mix digesters.

Flexible membrane materials commonly used for these gas holders include high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low density polyethylene (LLDPE), and chlorosulfonated polyethylene covered polyester. Thicknesses for cover materials typically vary from 0.5 to 2.5 millimeters.

Medium-Pressure Biogas Storage

Biogas can also be stored at medium pressure between 2 and 200 psi. To prevent corrosion of the tank components and to ensure safe operation, the biogas must first be cleaned by removing H2S. Next, the cleaned biogas must be slightly compressed prior to storage in tanks.

High-Pressure Biogas Storage

The typical composition of raw biogas does not meet the minimum CNG fuel specifications. In particular, the CO2 and sulfur content in raw biogas is too high for it to be used as vehicle fuel without additional processing. Biogas that has been upgraded to biomethane by removing the H2S, moisture, and CO2 can be used as a vehicular fuel.

Biomethane is less corrosive than biogas, apart from being more valuable as a fuel. Since production of such fuel typically exceeds immediate on-site demand, the biomethane must be stored for future use, usually either as compressed biomethane (CBM) or liquefied biomethane (LBM).

Two of the main advantages of LBM are that it can be transported relatively easily and it can be dispensed to either LNG vehicles or CNG vehicles. Liquid biomethane is transported in the same manner as LNG, that is, via insulated tanker trucks designed for transportation of cryogenic liquids.

Biomethane can be stored as CBM to save space. The gas is stored in steel cylinders such as those typically used for storage of other commercial gases. Storage facilities must be adequately fitted with safety devices such as rupture disks and pressure relief valves.

The cost of compressing gas to high pressures between 2,000 and 5,000 psi is much greater than the cost of compressing gas for medium-pressure storage. Because of these high costs, the biogas is typically upgraded to biomethane prior to compression.

Applications of Epoxy Resin in Clean Energy Sector

Epoxy resin is a kind of reactive prepolymer and polymer that contains epoxide groups. It is important to note that epoxy resin is different from other polyester resins in terms of curing. Unlike other resins, instead of using a catalyst as a curing agent, it is cured by an agent known as the hardener. It possesses many desirable properties such as high tensile strength, high adhesive strength, high corrosion resistance, and excellent moisture & chemical resistance. It is also resistant to fatigue, has a long shelf life, and has good electrical and insulating properties. The ability of epoxy resins to be used in various combinations and reinforcements makes it the foundation of a plethora of industries, including clean energy systems.

Applications of Epoxy Resins

Because of the versatile properties of epoxy resins, it is used widely in adhesives, potting, encapsulating electronics, and printed circuit boards. It is also used in the form of matrices for composites in the aerospace industries. Epoxy composite laminates are commonly used for repairing both composite as well as steel structures in marine applications.

Due to its high reactivity, epoxy resin is preferred in repairing boats that have been damaged by impact. Its low shrinking properties and ease of fabrication make it well suited for many tooling applications such as metal-shaping molds, vacuum-forming molds, jigs, patterns etc.

Use of Epoxy Resins in Clean Energy

A variety of industries have been actively trying to find a path that’s moving towards a society that puts less load on the the environment and also contributes towards reducing the carbon footprint. The accelerated use of epoxy resins in generating renewable energy has lead to a rise in its production demand. This is why the epoxy resin market is projected to witness a high demand and growth rate by 2022. Here are some of the sectors contributing to the production of clean energy and how they utilize epoxy resin for their functioning:

  • Solar Energy

The harnessing of solar energy dates back to 700 B.C, when people used a magnifying glass to focus the sun’s rays to produce fire. Today solar power is a vigorously developing energy source around the globe. It not only caters to the rising energy requirements but also the need to protect the environment from the exploitation of exhaustible energy resources.

A piece of average solar equipment endures intense environmental conditions such as scorching heat, UV radiations, bitter cold,  pouring rain, hail, storms, and turbulent winds. To withstand such conditions, the sealing and mounting application of epoxy resins increase the environmental tolerance of the solar equipment.

With their high mechanical strength, impressive dimensional stability and excellent adhesion properties, they are used to protect the solar panels from a wide range of temperatures. Epoxies are cheap, less labor-intensive and easy to apply.

  • Wind Energy

The global wind industry has quickly emerged as one of the largest sources of renewable energy around the world. The wind energy in the U.S. alone grew by 9% in 2017 and today is the largest source for generating clean energy in the country. With such a tremendous demand for wind power, the need for fabricating bigger and better wind turbine blades is also rising. The industry is in a dearth of long-lasting blades, that endure the harsh climatic conditions and wear tear and are able to collect more wind energy at a time.

Sealing and mounting application of epoxy resins increase the environmental tolerance of the solar equipment

Epoxy thermosets are used for making the blades more durable because of their high tensile strength and high creep resistance. Mixing of epoxy resins with various toughening agents and using them on the blades have shown positive results towards making the blades corrosion resistant and fatigue-proof.

  • Hydropower

Hydropower is an essential source of renewable and clean energy. As the hydropower industry is developing rapidly, the solution for protecting the hydropower concrete surfaces against low temperatures and lashing water flow has also been looked into.

As a solution to this issue, epoxy mortar, a mixture of epoxy resins, binder, solvent, mineral fillers, and some additives has proven to be the most effective material used for surface protection. Owing to the properties like non-permeability, adhesive strength, anti-erosive nature, and non-abrasiveness, epoxy mortar paste has been used as a repairing paste in the hydropower industry.

Over the last few decades, epoxy resins have contributed immensely in the maintenance and protection of clean energy sources, helping them to become more efficient and productive.

Final Thoughts

While many argue that factors like a relatively high cost when compared to petroleum-based resins and conventional cement-mortar alternatives has affected the epoxy resin market growth, the fact remains that epoxy resin never fails to deliver top-notch and unmatchable results in the areas of application.

Different Types of Thermocouples

Thermocouples are sensors used to measure temperatures. These devices consist of different metals to form two wire legs forming a junction. Manufacturers weld together these two wire legs to make sure the connection is stable. Thermocouple junctions are used to check for changes in temperatures. There are different types of thermocouples available in the market, and these models have distinct characteristics and features.

The Types of Thermocouples

The manufacturing of a thermocouple requires producers to classify units with distinct color codes. Manufacturers classify these codes in either ANSI/ASTM E230 OR IEC60584. The thermocouples, their calibrations, and their color designations (in ANSI/ASTM E320) are:

  • Type K: Yellow (+) / Red (-)
  • Type T: Blue (+) / Red (-)
  • Type N: Orange (+) / Red (-)
  • Type S: Black (+) / Red (-)
  • Type C: N/A
  • Type J: White (+) / Red (-)
  • Type E: Purple (+) / Red (-)
  • Type R: Black (+) / Red (-)
  • Type B: Black (+) / Red (-)

Conversely, here are the thermocouples once more and their calibrations, but with their IEC 60584 color designations:

  • Type K: Green (+) / White (-)
  • Type T: Brown (+) / White (-)
  • Type N: Rose (+) / White (-)
  • Type S: Orange (+) / White (-)
  • Type C: N/A
  • Type J: Black (+) / White (-)
  • Type E: Purple (+) / White (-)
  • Type R: Orange (+) / White (-)
  • Type B: Orange (+) / White (-)

Thermocouple Temperature Range

Aside from the color codes, thermocouple types have specific melting points and continuous maximum temperatures. For example, the thermocouple Type B with a platinum 30% rhodium (+) composition may have a temperature range of 2,500 to 3,100 degrees Fahrenheit. Conversely, a platinum 6% rhodium (-) composition of the same thermocouple type may yield a similar temperature range.

Another example is a thermocouple type E with a chromel (+) composition. For this model, you may use it for handling temperature ranges of 200 to 1,650 degrees Fahrenheit. Still, consider the environment before using specific thermocouple types.

Uses of Thermocouples

Different thermocouple types may have diverse uses. Hospital thermometers, automotive technologies, and machines handling renewable energies might use thermocouples to help users detect changes in temperatures. Here are a few thermocouple types and their uses:

  • Type J

This thermocouple type may have an iron and Constantan leg. Various organizations in different industries find this model to be helpful in several operations. For example, it may be useful in reducing, oxidizing, and vacuuming atmospheres. Type J models may have durable constructions. Thus, these units may not require sensitive handling when installing them in other machines or industrial environments.

  • Type K

This thermocouple has a Chromel and Alumel composition for its wire legs. Consider using this type to oxidize or inert atmospheres with temperatures of up to 2,300 Fahrenheit. Companies may use this thermocouple model thanks to its relatively accurate and stable readings even at high temperatures.

  • Type N

Type N thermocouples may be akin to better Type K models. This type has a Nicrosil and Nisil composition for its wire legs. It also has a similar temperature range as the Type K. However, type N models might have better resistance than its type K counterparts thanks to its temperature cycling features. Furthermore, its hysteresis and green rot allow type N models to be more cost-effective units than type Ks.

  • Type T

A copper and Constantan composition reside in the wire legs of type T thermocouples. Like the type J models, type Ts help users reduce, oxidize, vacuum, and inert atmospheres. Still, this thermocouple class has excellent resistance against corrosion in several atmospheres. It may also offer high-stability readings at sub-zero temperatures.

  • Type E

For this thermocouple, it has one Chromel and one Constantan leg. Like the type T thermocouple, it may also be resistant to corrosion in various atmospheres. However, there’s one characteristic that may put type E thermocouples better than other models: Type Es may have the highest EMF per degree in comparison with different thermocouple types. Nonetheless, it might not be resistant to sulfurous environments.

  • Type C

Environments that have sweltering temperatures may use type C thermocouples. This model has a tungsten and rhenium composition for its wire legs. Organizations may use this thermocouple type in extremely high-temperature environments of up to 4,200 degrees Fahrenheit. While it can withstand high temperatures, this thermocouple may have a brittle construction. Proceed with caution when handling it as one false move might break the device.


Always consider the right thermocouple type when you want to read temperatures accurately in specific environments. For instance, consider the right thermocouple when reading temperature levels in automotive technologies and their hot engines. These devices may also activate gas shut-off modules aside from reading temperatures. Take time in researching the right model for the job to avoid complications.