It is important to address the fact that we need to find ways to heat production without emissions. Wind and solar technologies are useful, but their output varies on their availability plus they need external storage systems. However, recently researchers discovered a sustainable alternative for the same, firebricks. Researchers discovered the positive effects of firebricks for industrial process heat in 149 countries.
Yes, they solved the main issue of storing the energy at a cost less than 1/10th of the cost of the batteries. After performing computer simulations across 149 countries, firebricks turned out to be a remarkable tool for reducing transition costs for renewable energy.
Effects of Firebrick for Industrial Process Heat in 149 Countries
Objective of the study: To analyze the impact of firebricks usage for storing industrial process heat on the cost of energy and stability of power grids in 149 countries.
To achieve the goals by 2050, countries are aiming to generate heat and electricity by 100% WWS (wind, water, solar) sources.
Processes Adopted in the Study
Researchers have used electric resistance heating to electricity to heat the firebricks. This heat will remain stored until needed for industrial processes. The results observed are compared with simulations without firebricks.
Transitioning to clean energy sources needs to serve all four purposes. Electrification needs to be done in all energy sectors, including residential, commercial, industrial, and others. Solar and geothermal will be used to heat buildings and industries, which is why they will not be electrified To replace the current system, wind, water, solar (WWS) need to be combined with electric generators.
Heat and Industries: Temperature Required
Industries require varying temperatures and amounts of heat for various processes.
- Ordinary cement and lime production – 1,300–1,800° C
- Fused silica, glass, traditional iron, and steel production – 1,000–1,500° C
- Inorganic mineral production – 150–500° C
- Alcohol and basic chemical manufacturing – 100–300° C
- Paper, paperboard, and pulp mills – <100° C
However, grid electricity is not included in industrial processes by IEA but with steam turbines, it needs a temperature of >200° C and with thermophotovoltaic cells, this sector needs around 1,000–2,000° C.
Generally, large amounts of heat are produced by continuous combustion of coal, fossil fuel, oil, or biomass. It also includes running electric resistance furnaces and boilers which are electric arc, electron beams, and electric induction, but it also uses dielectric heaters and electric heat pumps.
Instead of high-cost BS and GHS to store electricity for continuous low-to-high-temperature industrial process heat, it is preferred to use variable WWS electricity. This can be used as and when available to store heat in firebricks.
The stored electricity can be converted to heat by connecting firebricks to metallic electric-resistance heaters or direct resistance heating (DRH) of firebricks. Firebrick heat storages are surrounded by another type of firebrick which is more insulating and then a layer of steel to reduce any further heat loss. Or there is a thick steel container surrounding the bricks.
Features of Heat-Storing Firebricks
- By arranging in a pattern that allows airflow through channels, firebricks can be used effectively.
- Firebricks are cost-effective as no heat exchanger is required and can be made from inexpensive heat-storage materials.
- They have specific heat and densities and thus can absorb a lot of energy with little increase in temperature.
- They have high melting points.
The processed heat is drawn from the firebricks when needed in either of the following methods.
- It is done by passing ambient or recycled low-to-high-temperature air through channels in the bricks. Through direct infrared radiation from red-hot bricks.
- Similar to refractory bricks, these also have good insulating properties and high melting points. A high melting point enables them to withstand high temperatures and prevent rapid heat loss.
Requirements of Ideal Firebricks Heat Storage
If used for insulation, firebricks must withstand high temperatures but with low thermal conductivities. Since silica has low thermal conductivity (0.3 W/m-K), it is generally used in insulating firebricks.
Alumina silicate is also used in common types of insulating firebricks (mostly alumina and sand). It is also included in calcium silicate bricks (preferably sand and limestone).
Applications of Firebricks
For a long time, humans have used firebricks for heat storage in heat regenerators to make glass and steel.
What are regenerators?
These are heat interchangers which receive heat from a high temperature flue gas. They then store the heat for 20–30 minutes and then use this heat to preheat the air for combustion.
Quick Fact – China was storing 10 MW of heat in firebricks for commercial complexes and district heating projects before 2018.
Recently it was reported that tallest buildings could turn into green energy storehouses with gravity.
Potential Firebrick Options
Another material similar to firebricks is refractory materials which were historically used for various purposes.
- In the early Bronze Age (4,000-3,000 BC) to line primitive kilns.
- During the Iron Age (1,500-500 BC), to make iron-making furnaces.
- Since the early 1600s, in crucibles for molten glass.
- Since the mid-1850s in steel-making furnaces.
Refractory bricks contain high percentages of alumina and silica. It also has traces of magnesia (MgO), calcium oxide (CaO), and iron oxide (Fe2O3). During 1800 in Chile, these were used to line copper smelters. However, today these low-cost options are also made with chromia or/and mullite (aluminum silicate mineral). But firebrick mixtures may also have zirconia (ZrO2), silicon carbide (SIC), and zircon (ZrSiO4).
1. Graphite (pure low-grade solid carbon)
It is another potential option and can be heated to 2,400° C. However, this technology has various challenges to keep them cost-effective. The major challenge is the slow vaporization of graphite, then it has limited heat transfer ability as it uses radiant heating, because for many applications it may require additional heat transfer.
Firebricks’ temperature is not the same as the temperature of the material heated. As the temperature of materials depends on specific masses and heat of other firebricks and materials along with heat loss between the two.
For example: Suppose graphite firebricks are supplying 1500° C heat to a material. Here, the graphite needs to be heated to 1800-2000° C for both property and heat loss of the materials.
Methods Involved in Firebricks for Industrial Process Heat Study
The study effects of firebricks for industrial process heat in 149 countries involves 3 types of models as mentioned below.
Method #1 Spreadsheet Model
It is used to estimate 2050 Business as Usual (BAU) and wind, water, and solar (WWS) energy demand based on the current BAU demand. It is also used to calculate the nameplate capacities needed for WWS generators to meet 2050 WWS demand.
Method #2 global weather-climate-air pollution
Results from the spreadsheet model are fed into GATOR-GCMOM which is a global weather-climate-air pollution model. This model forecasts solar and wind electricity supply along with solar heat and wave electricity supply. It also forecasts building cooling and heating needs globally every 30 seconds for several years.
These predictions for solar, air, and wind temperatures along with input from generator nameplate capacity in the spreadsheet model.
Method #3 LOADMATCH
Output from GATOR-GCMOM is fed into LOADMATCH. This matches demand with supply, storage and response to demand for every 30 seconds for multiple years. LOADMATCH simulations are run for 3 years, from 2050 to 2052 with a 30-second time step.
Comparison of Simulations : 2 sets of simulations are compared: one with firebricks (firebrick case) and the other with no firebricks (base case). LOADMATCH simulations are carried out in 29 regions covering 149 countries.
Observations
In all 29 regions, grid stability was observed in the firebrick case, similar to the base case. Some of the key differences between both methods (base and firebrick) are mentioned in the table below. The firebricks decreased storage capacity requirements, and the variations observed are as follows:
Parameter | Percent difference = 100% × (a − b)/b |
Battery storage capacity | 14.5% |
Green hydrogen storage fuel cell size | 3.9% |
Hydrogen tank size | 18.3% |
Hydrogen production needed for grid electricity | 31.4% |
Underground thermal energy maximum discharge rate | 1% |
Underground thermal energy storage capacity | 27.3% |
Onshore wind nameplate capacity | 1.2% |
Offshore wind nameplate capacity | 0.54% |
Utility PV nameplate capacity | 0.54% |
CSP nameplate capacity | 0.84% |
Cross Reference – Supplementary Material: Effects of Firebricks for Industrial Process Heat
Overall, maximum discharge rates and capacities for storage increased by adding firebricks. But on electric storage and low-temperature heat storage, the effect was the opposite. Simply speaking, adding firebricks increased the maximum discharge rate for all storage types but decreased the maximum capacity for the same.
The carbon footprint of a house in Japan is 38 tons, a study finds, which is interesting. I wonder what the carbon footprint of my house is!
Cost Reduction with Firebricks
In all 149 countries assessed, the firebrick case needed 14.5% less (32.2 TWh instead of 37.7 TWh) battery storage capacity than the base case. The considerable reduction in the cost of firebrick storage in comparison to battery storage is the main reason for lower energy costs in the firebrick case.
The figure below indicates the benefits of reducing the capacities of electricity and low-temperature heat storage and generators with firebricks. It also reduces transition capital costs of 149 countries to WWS from $58.24 to $56.97 trillion (2020 USD) to $1.27 trillion (2.2%).
However, a decrease in capital costs was observed in all regions, except Canada and Iceland. This is because they already have an abundant and regular supply of hydropower and wind resources and do not require a firebrick approach (but it was still installed during the process).
Moreover, there was a decrease in the Levelized Cost of Energy (LCOE) by 0.15 ¢/kWh (1.7%) and annual energy cost by $119 billion/year (1.78%) across 149 countries.
Lower LCOE costs were possible by reducing costs related to the grid: grid hydrogen, underground thermal-energy storage, battery, and electricity generation costs.
On the other hand, firebrick storage capacity increases from 0TWh to 32.1 TWh. Although the firebrick storage capacity is 5.8 times greater than the reduced battery storage capacity, its cost per kWh is 1/10th of battery storage. It clearly indicates that replacing batteries with firebricks will reduce costs.
Annual Average End-Use Demand BAU and WWS 2050
As per the estimated energy demand in 2050, firebricks tend to increase the lower annual energy cost differences between firebricks and base cases. Lower capital costs combined with firebricks contribute to a 3.2% decrease which is from 5.9 to 5.7 years showing higher differences in 149 countries’ energy cost payback time. This is in the case when there is a 100% transition to WWS.
Moreover, in 2 regions, Southeast Asia and New Zealand, the payback time decreases by more than a year. Using firebricks also reduces the land required for electricity generators. The difference noted was a reduction of 2,700 km2 (0.43%) in 149 countries.
The Only Drawback of Firebricks in Industrial Heating Processes
With so many advantages, the only con noted here is the low number of job opportunities created with it. Estimated, ∼0.51% (118,000) fewer jobs were created since there were reductions in electricity and low-temperature heat storage capacities along with the needed generator nameplate capacities in firebrick vs base cases.
How to Store Solar Energy Without Batteries and firebricks, let’s find out!
Case Studies: Firebricks for Industrial Process Heat
A report published in 2019 researched by Daniel C. Stack et al. mentions the performance of firebrick resistance-heated energy storage. The team conducted computer simulations with firebricks and stored electricity at high-temperature heat of about 1000-1700° C.
They arranged firebricks in a specific and protected pattern. When heat was required, bricks were moved to a cold air stream and then used for industrial operations or to produce electricity using a steam turbine. Through this, researchers concluded that within hours they can charge and discharge the firebricks. They also suggested that systems with 100s to 1000s megawatt-hours capacity can be used daily.
Metallic alloy and ceramic electric resistance heaters were used to convert electricity into heat energy. They connected bricks (magnesia, silicon carbide, or alumina) to the heaters.
Observations:
Silicon carbide and molybdenum disilicide heaters reached the highest temperatures. But even heat distribution to the center of the brick array was difficult for them.
For temperatures up to 1100° C, these heaters are suitable but once the temperature reaches 1500° C and crosses it, they start deteriorating. This mainly happens because their outer protective coating gives way to oxygen diffusion.
Suggestions
To heat firebricks, researchers suggested using direct resistance heating (DRH). Electrically conductive firebricks are heated with electric current and their temperature rises up to 1800° C. These firebricks contain chromia (a conductive metal oxide) doped with magnesium or nickel oxide, allowing them to attain high temperatures.
Advantages of DRH
- Since firebricks are heating elements themselves, DRH proves to be advantageous with no temperature drop between heating the element and firebricks.
- Also, DRH is not affected by current, frequency, or voltage.
- It does not require expensive power electronics.
- It is suitable for direct connection to a photovoltaic array.
Researchers estimated the price of a 250-MWh alumina firebrick system with external heating in 2018 was approximately $10.75/kWh-thermal-storage. This includes the following ratios:
- Insulation (1.6%)
- Containment vessel (7.2%)
- Firebricks (18.4%)
- Transformer (52.2%)
- Blower (11.9%)
- Metallic heater wire (8.7%)
To begin with, the price of firebricks was around $2.12/kWh, however, magnesium oxide would have been cost-effective at $1.87/kWh and silicon carbide cost around $7.18/kWh. But in comparison, the cost of batteries was $250-$500/kWh which is around 10 times more than the cost of thermal storage per kWh.
Case Studies
2021
According to data from 2021, electricity accounted for just 20.6% of the total demanded power in 149 countries’ end-use sectors. The rest contributions were from tides or wave energy 0.0043%, geothermal 0.33%, solar 3.63%, wind 6.54%, and 15.5% hydro.
In 2021-2022, around 47 countries generated more than 50% of demanded electricity with WWS and seven countries generated 99.8-100% electricity with WWS.
Until now hydropower has dominated WWS generation but solar and wind are taking up the market. In case, if the major part of electricity in the world is generated by WWS then around 90% of it would be generated by WWS.
2022
Around 17% of global CO2 emissions in 2022 were from industrial heat combustion. Also, 8.38% was from chemical reactions during the manufacturing stage of steel, cement and other products.
Conclusion
With this, researchers concluded that the effects of firebricks for industrial process heat in 149 countries are positive and they are a useful tool for storing industrial process heat and transitioning to clean energy. Firebricks can store high temperatures of heat for industrial processes and lower the cost of renewable energy. There are some uncertainties about their performance like the daily loss rate of heat. But even with a 5% daily heat loss rate, firebricks still are a cost-effective option.
Even though firebricks do not address industrial emissions, but their emissions from heat production can be reduced to a large extent. Thus, policies and incentives are required to address climate change, energy security, and air pollution to promote sustainable potential solutions.
Source: Effects of firebricks for industrial process heat
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