Vanadium Redox Flow Battery Characteristics And

Are vanadium redox flow batteries a good energy storage system?

There are many types of energy storage systems. Among them, one of the most interesting in the last decades has been vanadium redox flow batteries (VRFBs) because of their long lifetime and scalability. The performance of VRFBs is affected by many different parameters, including the electrolyte flow rate.

What is flow rate optimization in a vanadium redox flow battery?

Studies on flow rate optimization in the vanadium redox flow battery are rarely reported in literature. Ma et al. proposed a flow rate step-up strategy which maintains a constant flow rate throughout main operating state-of-charge (SOC) until stepping up the flow rate at the end of charge or discharge .

Do redox flow batteries have a flow factor control strategy?

Abstract: The optimization of vanadium redox flow batteries (VRFBs) is closely related to the flow rate control: a proper regulation of the electrolyte flow rate reduces losses and prolongs battery lifetime. To this end, a flow factor control strategy in VRFBs was proposed in the literature provided with numerical/experimental validations.

What is a redox flow battery?

This type of battery belongs to the family of redox flow batteries. Redox flow batteries differ from conventional batteries by having energy conversion systems separate from the chemical storage. 8 This makes it possible to modularize the design of these batteries, giving them flexibility and scalability.

Why is electrolyte flow control important for large-scale vanadium redox flow battery systems?

Apart from this, the electrolyte flow also plays a key role in removing any accumulated heat in the stack to avoid potential thermal precipitation in the positive half-cell. Therefore, a sophisticated flow control system is valuable for large-scale vanadium redox flow battery systems and is worthy of further investigation and development.

What is mass transport loss in all-vanadium redox flow batteries?

This mass transfer resistance thus contributes to voltage losses, referred to as mass transport losses or concentration overpotential, compared to the reversible potential of cell. In this paper, we derived analytical expressions for estimating the mass transport losses in all-vanadium redox flow batteries.

What is the difference between flow batteries and conventional batteries?

Energy storage is the main differing aspect separating flow batteries and conventional batteries. Flow batteries store energy in a liquid form (electrolyte) compared to being stored in an electrode in conventional batteries. Due to the energy being stored as electrolyte liquid it is easy to increase capacity through adding more fluid to the tank.

Are flow batteries better than lithium ion?

There's no such thing as a flow-battery Tesla. But the companies at the International Flow Battery Forum in Prague in late June were adamant that flow batteries are now cheaper, more reliable, and safer than lithium ion in a growing number of real-world stationary energy applications.

Are flow batteries cheaper than other batteries?

On charging, ions from one electrolyte move through the battery's membrane to the second electrolyte. At large scale, flow batteries are cheaper than other batteries over their lifetimes. Source: Saudi Aramco. Note: The comparison is of the lifetime cost of a 10 MW battery capable of supplying electricity for 4 h at a time.

What are the advantages and disadvantages of flow batteries?

One advantage of flow batteries is that they can also be immediately “recharged” by replacing the spent liquids in the tank with energised liquid. The volume of liquid electrolyte determines the battery energy capacity, with the surface area of the electrodes determining the battery power – so typically flow batteries are quite large and heavy!

Are redox flow batteries better than lithium ion batteries?

Redox flow batteries have a reputation of being second best. Less energy intensive and slower to charge and discharge than their lithium-ion cousins, they fail to meet the performance requirements of snazzy, mainstream applications, such as cars and cell phones. There's no such thing as a flow-battery Tesla.

Are vanadium redox flow batteries expensive?

Vanadium Redox Flow Batteries (VRFBs) are proven technologies that are known to be durable and long lasting. They are the work horses and long-haul trucks of the battery world compared to the sports car, like fast Lithium-Ion (Li-Ion) batteries. However, VRFBs have developed a reputation for being notoriously expensive.

What is a vanadium flow battery?

Vanadium flow batteries employ all-vanadium electrolytes that are stored in external tanks feeding stack cells through dedicated pumps. These batteries can possess near limitless capacity, which makes them instrumental both in grid-connected applications and in remote areas.

What is a single vanadium element battery?

Their single vanadium element system avoids capacity fading caused by crossover contamination in iron-chromium flow batteries (ICFBs) . Additionally, VRFBs use an aqueous electrolyte, eliminating the safety risks associated with bromine vapor corrosion in zinc-bromine flow batteries (ZBFBs) .

What is a single cell vanadium redox flow battery (VRFB)?

A laboratory-scale single cell vanadium redox flow battery (VRFB) was constructed with an active area of 64 cm 2. The electrolyte was produced by dissolving vanadium pentoxide in sulphuric acid.

What is a vanadium redox flow battery?

Vanadium redox flow battery is one of the most promising devices for a large energy storage system to substitute the fossil fuel and nuclear energy with renewable energy. The VRFB is a complicated device that combines all the technologies of electrochemistry, mechanical engineering, polymer science, and materials science similar to the fuel cell.

What is the ideal electrolyte for vanadium batteries?

The ideal electrolyte for vanadium batteries needs to ensure the stability of high-concentration vanadium ions in different oxidation states over a wide temperature range. A key issue to be resolved is to improve the stability of V 5+ at high temperatures (50 °C) and V 3+ at low temperatures (−5 °C).

Can ion transport improve vanadium redox flow battery electrolytes?

Furthermore, research progress in other battery fields shows that optimizing electrolyte formulations [21, 22] and ion transport [23, 24] can significantly enhance energy density and cycling stability, providing valuable insights for improving vanadium redox flow battery electrolytes. Table 1.

What is a vanadium flow battery?

It can provide sustainable and reliable energy supply solutions, particularly for renewable energy sources such as solar and wind. Vanadium flow batteries consist of two tanks containing vanadium electrolyte, a pump system to circulate the electrolyte, and a fuel cell stack where the electrochemical reactions occur.

How do electrolytes work in vanadium flow batteries?

Electrolytes operate within vanadium flow batteries by facilitating ion transfer and enabling efficient energy storage and release during the charging and discharging processes. Vanadium flow batteries utilize vanadium ions in two different oxidation states, which allows for effective energy storage.

What are the advantages of using vanadium flow batteries for energy storage?

The key advantages of using vanadium flow batteries for energy storage include their longevity, scalability, safety, and efficiency. Longevity: Vanadium flow batteries have a long operational life, often exceeding 20 years. Scalability: These batteries can be easily scaled to accommodate various energy storage needs.

What factors contribute to the adoption of vanadium flow batteries?

Several factors contribute to the adoption of vanadium flow batteries, including the need for energy storage in renewable energy integration, reductions in energy costs, and technological advancements in battery components. The scalability of these systems also impacts their deployment.

What are vanadium redox flow batteries (VRFB)?

Interest in the advancement of energy storage methods have risen as energy production trends toward renewable energy sources. Vanadium redox flow batteries (VRFB) are one of the emerging energy storage techniques being developed with the purpose of effectively storing renewable energy.

How long do vanadium flow batteries last?

While vanadium flow batteries can cycle through charge and discharge many times, issues such as membrane degradation can shorten their effective life. A lifespan of around 10,000 cycles is common, unlike lithium-ion batteries, which can offer around 3,000 to 5,000 cycles.

What is the capacity of the world's largest vanadium flow battery?

It has a capacity of 175 MW/700 MWh. On December 5, 2024, Rongke Power (RKP) completed the installation of the world's largest vanadium flow battery . With a capacity of 175 MW and 700 MWh, this innovative energy storage system, located in Ushi, China, sets a new standard in long-duration energy storage solutions.

How long can a vanadium flow battery last?

Vanadium flow batteries provide continuous energy storage for up to 10+ hours, ideal for balancing renewable energy supply and demand. As per the company, they are highly recyclable and adaptable, and can support projects of all sizes, from utility-scale to commercial applications.

How much energy can a vanadium flow battery store?

A press release by the company states that the vanadium flow battery project has the ability to store and release 700MWh of energy. This system ensures extended energy storage capabilities for various applications. It is designed with scalability in mind, and is poised to support evolving energy demands with unmatched performance.

How does a vanadium flow battery work?

The key component of a vanadium flow battery is the stack, which consists of a series of cells that convert chemical energy into electrical energy. The cost of the stack is largely determined by its power density, which is the ratio of power output to stack volume. The higher the power density, the smaller and cheaper the stack.

Where is the Xinhua ushi ESS vanadium flow battery located?

The Xinhua Ushi ESS vanadium flow battery project - termed the world's largest - is located in Ushi, China.

Why is Rongke Power a global leader in vanadium flow batteries?

With this achievement, Rongke Power reaffirms its position as a global leader in vanadium flow battery technology. The project also serves as a model for future installations worldwide, proving that vanadium flow batteries are a viable option for large-scale energy management. Follow us on social networks and don't miss any of our publications!

Are vanadium redox flow battery electrolytes stable at high temperatures?

Insufficient thermal stability of vanadium redox flow battery (VRFB) electrolytes at elevated temperatures (>40 °C) remains a challenge in the development and commercialization of this technology, which otherwise presents a broad range of technological advantages for the long-term storage of intermittent renewable energy.

What is a vanadium flow battery?

A schematic of a vanadium flow battery is depicted in Figure 1, in which two external tanks are used to carry vanadium ions in their various oxidation states (V 2+, V 3+, VO 2+, and VO 2+) with one redox pair present in each tank.

What is the temperature range of a vanadium flow battery?

Xi J, Jiang B, Yu L, Liu L (2017) Membrane evaluation for vanadium flow batteries in a temperature range of −20–50 °C. J Membrane Sci 522:45–55 Ye Q, Shan TX, Cheng P (2017) Thermally induced evolution of dissolved gas in water flowing through a carbon felt sample. Int J Heat Mass Transf 108:2451–2461

How stable is a vanadium electrolyte?

The stability of the vanadium electrolyte is also highly dependent on the temperature. Temperatures above 40 °C in the positive electrolyte and below 10 °C in the negative electrolyte commonly induce formation of solid V 2 O 5 and VSO 4 precipitates, respectively. [ 2]

Why does the concentration of vanadium vary during battery operation?

This dependence is of critical importance during battery operation; since the SOC of the solution for each half-cell electrolyte could be changed, the vanadium concentrations may differ accordingly because of the ionic diffusion processes across the membrane and thus the solution conductivities vary.

Can vanadium flow batteries avoid cross-contamination?

Authors to whom correspondence should be addressed. These authors contributed equally to this work. The vanadium flow batteries that employ the vanadium element as active couples for both half-cells, thus avoiding cross-contamination, are promising large-scale energy storage devices.

Are zinc-based flow batteries good for distributed energy storage?

Among the above-mentioned flow batteries, the zinc-based flow batteries that leverage the plating-stripping process of the zinc redox couples in the anode are very promising for distributed energy storage because of their attractive features of high safety, high energy density, and low cost .

Are Zn-FB batteries a good choice for long-duration energy storage (LDEs)?

Unlike that conventional flow batteries operate on the basis of liquid-liquid conversions, the Zn anode in Zn-FBs adopts a solid-liquid conversion reaction, presenting challenges such as dendrite formation, poor reversibility, and low areal capacity, limiting its long-duration energy storage (LDES) applications.

What are zinc-bromine flow batteries?

Among the above-mentioned zinc-based flow batteries, the zinc-bromine flow batteries are one of the few batteries in which the anolyte and catholyte are completely consistent. This avoids the cross-contamination of the electrolyte and makes the regeneration of electrolytes simple.

Are flow batteries a safe and effective energy storage technology?

The electricity produced from renewables is volatile and intermittent, which is one of the big obstacles for their widespread applications. Energy storage technology, flow battery technologies in particular, is a safe and effective approach to address this issue .

What are the different types of flow batteries?

Currently, the flow battery can be divided into traditional flow batteries such as vanadium flow batteries, zinc-based flow batteries, and iron-chromium flow batteries, and new flow battery systems such as organic-based flow batteries, which hold great promise for energy storage applications.

What are the different types of zinc-based flow batteries?

Since the 1970s, various types of zinc-based flow batteries based on different positive redox couples, e.g., Br - /Br 2, Fe (CN) 64- /Fe (CN) 63- and Ni (OH) 2 /NiOOH , have been proposed and developed, with different characteristics, challenges, maturity and prospects.

Are low-temperature rechargeable batteries possible?

Consequently, dendrite-free Li deposition was achieved, Li anodes were cycled in a stable manner over a wide temperature range, from −60 °C to 45 °C, and Li metal battery cells showed long cycle lives at −15 °C with a recharge time of 45 min. Our findings open up a promising avenue in the development of low-temperature rechargeable batteries.

Are low-temperature lithium batteries safe?

However, the low-temperature Li metal batteries suffer from dendrite formation and dead Li resulting from uneven Li behaviors of flux with huge desolvation/diffusion barriers, thus leading to short lifespan and safety concern.

Are aqueous redox flow batteries safe at low temperatures?

Provided by the Springer Nature SharedIt content-sharing initiative Operating aqueous redox flow batteries (ARFBs) at low temperatures is prohibited by limited solubility of redox-active materials, freezing electrolytes and sluggish reaction kinetics.

Are lithium-based batteries stable at low temperatures?

Stable operation of rechargeable lithium-based batteries at low temperatures is important for cold-climate applications, but is plagued by dendritic Li plating and unstable solid–electrolyte interphase (SEI). Here, we report on high-performance Li metal batteries under low-temperature and high-rate-charging conditions.

How to improve low-temperature performance of lithium ion battery?

Then, the rational strategies for improving the low-temperature performance of LIB are discussed from four aspects: the research and optimization of electrolyte, the modification and exploitation of electrode materials, the development of new types of battery system as well as the design of Battery Thermal Management System (BTMS).

How do high-performance Li metal batteries perform under low-temperature and high-rate-charging conditions?

Here, we report on high-performance Li metal batteries under low-temperature and high-rate-charging conditions. The high performance is achieved by using a self-assembled monolayer of electrochemically active molecules on current collectors that regulates the nanostructure and composition of the SEI and deposition morphology of Li metal anodes.

Are vanadium redox flow batteries sustainable?

In the pursuit of sustainable and reliable energy storage solutions, Vanadium Redox Flow Batteries offer a compelling combination of safety, longevity, and recyclability - key attributes of any truly environmentally friendly and long-duration energy storage technology.

When were vanadium flow batteries invented?

In the 1980s, the University of New South Wales in Australia started to develop vanadium flow batteries (VFBs). Soon after, Zn-based RFBs were widely reported to be in use due to the high adaptability of Zn-metal anodes to aqueous systems, with Zn/Br2 systems being among the first to be reported.

What is a vanadium redox flow battery (VRFB)?

In contrast, technologies like vanadium redox flow batteries (VRFBs) rely on reusable liquid electrolytes and recyclable hardware, enabling a more robust and predictable pathway toward circular energy storage.

How long do flow batteries last?

Valuation of Long-Duration Storage: Flow batteries are ideally suited for longer duration (8+ hours) applications; however, existing wholesale electricity market rules assign minimal incremental value to longer durations.

Why do flow battery developers need a longer duration system?

Flow battery developers must balance meeting current market needs while trying to develop longer duration systems because most of their income will come from the shorter discharge durations. Currently, adding additional energy capacity just adds to the cost of the system.

Do flow batteries degrade?

That arrangement addresses the two major challenges with flow batteries. First, vanadium doesn't degrade. “If you put 100 grams of vanadium into your battery and you come back in 100 years, you should be able to recover 100 grams of that vanadium—as long as the battery doesn't have some sort of a physical leak,” says Brushett.

Where are flow battery companies located?

However, the current commercial flow batteries are mainly all-vanadium and zinc-based flow batteries. World-renowned flow battery companies are located in Austria, the United States, Canada and other countries. Below are the top 10 flow battery companies in the world article for your reference. Established: 1986 Location: Wiener Neudorf, Austria

What are flow batteries used for?

Flow batteries help create a more stable grid and reduce grid congestion and fill renewable energy production shortfalls for asset owners. Global R&D is fueling the development of flow battery chemistry by significantly enabling higher energy density electrodes and also extending flow battery applications.

Who is the best flow battery manufacturer in China?

One of the top 10 flow battery manufacturers in China, HBIS has researched and prepared high-purity and high-performance vanadium redox flow battery electrolyte with low impurity content, high product stability and low production cost, and has developed more than 10 mature processes.

Who makes flow battery chips?

Major Flow Battery Chip companies include: Sumitomo Electric Industries, Ltd. Sumitomo Electric Industries, Ltd., a world-class manufacturer of optical fiber cables and electric wires. The company operates through five business segments—Automotive, Electronics, Info communications, Environment and Energy, Industrial Materials, and Others.

What are flow battery chemistries?

Typical flow battery chemistries include all-vanadium, iron-chromium, zinc-bromine, etc. However, the current commercial flow batteries are mainly all-vanadium and zinc-based flow batteries. World-renowned flow battery companies are located in Austria, the United States, Canada and other countries.

Who is Yinfeng new energy in flow battery manufacturers in China?

Yinfeng New Energy in flow battery manufacturers in China focuses on the R&D, manufacturing and commercial application of new high-power and large-capacity energy storage products - vanadium redox battery energy storage systems.

Are zinc-bromine flow batteries suitable for large-scale energy storage?

Zinc-bromine flow batteries (ZBFBs) offer great potential for large-scale energy storage owing to the inherent high energy density and low cost. However, practical applications of this technology are hindered by low power density and short cycle life, mainly due to large polarization and non-uniform zinc deposition.

What is the energy density of zinc-bromine and Zn-vanadium batteries?

The energy densities for zinc-bromine and Zn-vanadium battery are 282 and 56 Wh/L catholyte, respectively (fig. S14). Since we used single-side flow batteries here, which only flow the anolyte, the high discharge of depth was achieved in all AZFB systems (fig. S17).

What is a zinc-based flow battery?

The history of zinc-based flow batteries is longer than that of the vanadium flow battery but has only a handful of demonstration systems. The currently available demo and application for zinc-based flow batteries are zinc-bromine flow batteries, alkaline zinc-iron flow batteries, and alkaline zinc-nickel flow batteries.

Are zinc-based flow batteries good for distributed energy storage?

Among the above-mentioned flow batteries, the zinc-based flow batteries that leverage the plating-stripping process of the zinc redox couples in the anode are very promising for distributed energy storage because of their attractive features of high safety, high energy density, and low cost .

What are zinc-bromine flow batteries?

In particular, zinc-bromine flow batteries (ZBFBs) have attracted considerable interest due to the high theoretical energy density of up to 440 Wh kg −1 and use of low-cost and abundant active materials [10, 11].

What is the power density of a zbfb battery?

The ZBFB delivers a peak power density of 1.363 W cm −2 at room temperature. The ZBFB stably runs over 1200 cycles (∼710 h) at 200 mA cm −2 and 60 mAh cm −2. Zinc-bromine flow batteries (ZBFBs) offer great potential for large-scale energy storage owing to the inherent high energy density and low cost.

Can vanadium batteries replace lithium batteries?

China is rich in vanadium resources, and it is feasible to use vanadium batteries to replace lithium batteries in some areas, but the energy density of vanadium battery is not as good as lithium battery, and it occupies a large area, which makes it only suitable for large-scale energy storage projects.

How much does a vanadium battery cost?

Some vanadium batteries already provide complete energy storage systems for $500 per kilowatt hour, a figure that will fall below $300 per kilowatt hour in less than a year. That is a full five years before the gigafactory hits its stride. By 2020, those energy storage systems will be produced for $150 a kwh. Then there is scaling.

What is the difference between a lithium and a vanadium battery?

Lithium batteries decay and lose capacity over time, while vanadium batteries discharge at 100% throughout their entire lifetime. To account for this capacity loss, lithium batteries often have to be oversized at the time of installation, adding to the costs involved, but with a vanadium battery, the capacity you purchase is the capacity you need.

Are vanadium flow batteries safe?

Indeed, vanadium flow batteries offer the highest level of safety compared to any other battery technology on the market today. Vanadium flow batteries operate at a wider range of temperatures than lithium, so they can be installed both indoors and outdoors. In addition, vanadium flow batteries store energy in tanks, rather than cells.

Which is better vanadium redox flow battery or lithium ion battery?

Among them, vanadium redox flow battery is more favored by researchers because of its good battery performance. This article will compare the deference between vanadium redox flow battery vs lithium ion battery. What is vanadium redox flow battery?

What is a vanadium flow battery?

In fact, vanadium batteries are known for having the easiest end-of-life processing. Combine this with the fact that lithium batteries need to be replaced more often and lose capacity over time, a vanadium flow battery is a greener alternative to lithium that creates far less waste.

What is all vanadium redox flow battery (VRFB)?

The all vanadium redox flow battery (VRFB) is an electrochemical energy storage system invented by Maria Skyllas-Kazacos in 1984. It consists of two electrochemical half cells, separated by an ion exchange membrane (Fig. 13.4). 13.4. Overview of a vanadium redox flow battery.

What is a vanadium redox battery (VRB)?

The vanadium redox battery (VRB), also known as the vanadium flow battery (VFB) or vanadium redox flow battery (VRFB), is a type of rechargeable flow battery. It employs vanadium ions as charge carriers.

Can a vanadium redox flow battery be used as an electrocatalyst?

Yuke Su, in Journal of Power Sources, 2021 The vanadium redox flow battery (VRFB) is promising for large-scale energy storage, but commercial electrodes, such as graphite felt (GF), suffer from poor electrochemical activity caused by sluggish kinetics and high polarization, leading to a need for high performance and cost-effective electrocatalysts.

What is a redox flow battery?

Although there are many different flow battery chemistries, vanadium redox flow batteries (VRFBs) are the most widely deployed type of flow battery because of decades of research, development, and testing. VRFBs use electrolyte solutions with vanadium ions in four different oxidation states to carry charge as Figure 2 shows.

What are vanadium redox batteries used for?

For several reasons, including their relative bulkiness, vanadium batteries are typically used for grid energy storage, i.e., attached to power plants/electrical grids. Numerous companies and organizations are involved in funding and developing vanadium redox batteries. Pissoort mentioned the possibility of VRFBs in the 1930s.

How important is safety advice for a vanadium flow battery?

As the global installed energy capacity of vanadium flow battery systems increases, it becomes increasingly important to have tailored standards offering specific safety advice.

What is liquid flow battery energy storage system?

The establishment of liquid flow battery energy storage system is mainly to meet the needs of large power grid and provide a theoretical basis for the distribution network of large-scale liquid flow battery energy storage system.

Can flow battery energy storage system be used for large power grid?

is introduced, and the topology structure of the bidirectional DC converter and the energy storage converter is analyzed. Secondly, the influence of single battery on energy storage system is analyzed, and a simulation model of flow battery energy storage system suitable for large power grid simulation is summarized.

How a liquid flow energy storage system works?

The energy of the liquid flow energy storage system is stored in the electrolyte tank, and chemical energy is converted into electric energy in the reactor in the form of ion-exchange membrane, which has the characteristics of convenient placement and easy reuse,,, .

What is a redox flow battery?

Redox flow batteries (RFBs) or flow batteries (FBs)—the two names are interchangeable in most cases—are an innovative technology that offers a bidirectional energy storage system by using redox active energy carriers dissolved in liquid electrolytes.

Does a liquid flow battery energy storage system consider transient characteristics?

In the literature, a higher-order mathematical model of the liquid flow battery energy storage system was established, which did not consider the transient characteristics of the liquid flow battery, but only studied the static and dynamic characteristics of the battery.

What is a Technology Strategy assessment on flow batteries?

This technology strategy assessment on flow batteries, released as part of the Long-Duration Storage Shot, contains the findings from the Storage Innovations (SI) 2030 strategic initiative.

Why is graphite felt a good electrode material?

Graphite felt (GF) has become main electrode material due to its low cost, good stability, and strong corrosion resistance . However, its poor hydrophilicity and insufficient active sites result in slow redox kinetics and restrict the battery efficiency, , .

What are sigracell® carbon and graphite felts used for?

SIGRACELL® carbon and graphite felts offer ideal properties for an efficient charge exchange in high-temperature batteries like redox flow batteries.

What size battery felt do you supply?

We supply battery felts in standard sizes up to 1350 mm (53") in width in 25 m (82 ft) rolls. Beyond that, we produce carbon and graphite felts in customer- specific dimensions. The entire in-house value chain ensures the quality of SIGRACELL ® battery felts from SGL Carbon and thus contributes to optimizing battery performance.

Are gf@fe-n/s-CNF batteries efficient?

At 200 mA cm −2, energy efficiency and voltage efficiency of the battery using GF@Fe-N/S-CNFs are 9.7 % and 10.6 % higher than those of blank battery, and efficiency displays no decay during 350 charge–discharge cycles at 150 mA cm −2. This study improves poor stability on the electrode and insufficient active sites for carbon-based catalysts.

Why do we use felts for anodes & cathodes?

Our felts are used for anodes as well as cathodes. Thanks to a unique combination of electrical conductivity, electrochemical stability, high porosity and good elasticity, they facilitate an efficient charge exchange between the electrolyte and the bipolar plate.