The most discussed energy carriers of the future are electricity and hydrogen. But which is likely to win, or do they both have a future in glass manufacturing asks Rene Meuleman*?

The entire glass manufacturing industry will need to undergo the biggest technological change since its inception in order to comply with the Paris Agreement on climate change, and to meet the demand for carbon free manufactured products coming from its customers.

Being forced to move away from fossil fuel towards alternative energy sources will have a huge impact on technologies, operations and finances.

All stakeholders involved in the industry have a responsibility to make sure the industry survives, and in that respect, all options need to be investigated. Bearing in mind, that the ultimate objective is to find the most cost-effective and cost-efficient way of melting glass without emitting CO2.

Today, the most discussed energy carriers of the future are electricity and hydrogen.

But which is likely to win, or do they both have a future in glass manufacturing?

Hydrogen
Hydrogen in its pure form doesn’t exist and needs to be produced. There are several production methods available, but only water splitting by electrolysis or thermochemical cycles can produce so called ‘green hydrogen’.

The electrolysis process obviously needs green electricity to split water into hydrogen and oxygen. And even though large-scale hydrogen production based on electrolysis is feasible, it loses at least 20% of energy in the conversion.

Therefore, the question arises; why not use the electrical energy in the melting process in the first place?

Thermochemical water splitting methods can use heat powered by solar or nuclear energy without electricity as an intermediary. These thermochemical cycle processes are considered to be promising, but only for long-term, large-scale hydrogen production.

Be aware: hydrogen is an excellent and clean reductant that can be used in steel manufacturing.

However, in glass manufacturing it will only be used as a very inefficient (45% of energy at the most ends up in the glass) heat source, representing a huge waste of energy. In locations where hydrogen availability remains insufficient to fully supply the transportation, steel, cement and glass manufacturing industries, those who need it the most will pay for it. In this situation, automotive, steel and cement industries will be the main consumers, leaving little available for glass manufacturing.

As previously mentioned, at least another 20% of energy is lost in the conversion from electrical energy into hydrogen; therefore, only around 36% of the initial energy will end up in the glass melting process by using hydrogen combustion, compared to around 85% of electrical energy ending up in the process if an all-electric melting system is used.

Electricity
Since 1902, electric melting has developed into an established, efficient, high energy technology used by many glass manufacturers all over the world, specifically for tableware, borosilicate and insulation glass fibre manufacturing.

Also, most container glass furnaces are equipped with electrical furnace boosting, either to increase furnace pull, manage darker glass output or a combination of both. It is a common misunderstanding that large all-electric furnaces have never existed, when really, they have!

All-electric furnaces have been around for decades, the largest having mostly been decommissioned only due to commercial reasons.

Smaller versions remain in operation, new ones have been put into operation and there are perfectly viable arguments for that.

Smaller all-electric furnaces are more energy efficient by far, in comparison to smaller fossil fuel fired furnaces.

Furthermore, all-electric furnaces can consistently produce a much higher glass quality compared to fossil fuel fired furnaces. Emissions are much lower, and all-electric furnaces are easier to control.

Natural gas or other alternative fossil fuels might be cheaper than kWh’s, but considering the huge energy efficiency difference between fossil fuel fired and electric furnaces, together with what needs to be paid for CO2 and other fossil fuel related emission taxes and penalties, the break-even point is close.

Recently, the Netherlands Environmental Assessment Agency, focusing mainly on the established Dutch commodity glass manufacturing industry, rated electric melting with a technology readiness level (TRL) of 7, against hydrogen rated with a TRL of just 4.

Considering the high number of all-electric melters in operation, against the number of hydrogen fired melters of which there are very few, this seems to put electrical energy far in front of hydrogen.

Conclusion
Nobody should dismiss any possible future technology that might be able to contribute to CO2 free glass manufacturing, without having valid, objective and solid arguments.

It is already understood, with some limitations, that electric glass melting works either in an all-electric or hybrid design. It is an established technology and is very energy efficient even in larger furnaces.

More research needs to be done to overcome some specific concerns, like high cullet content, possible issues with reducing glasses and refractory wear in all-electric melting.

Perhaps multiple smaller all-electric furnaces running in parallel or each supplying only one IS-machine need to be considered, specifically in greenfield initiatives? Testing, prototyping, proof of concept and scaling up or scaling down can be done in most existing facilities.

Hydrogen fired furnaces will need much more R&D and testing, as there is obviously not much experience available to kick start such an initiative.

However, hydrogen can be considered in a hybrid furnace design in place of fossil fuel, where it is typically used for only 20% of the energy supply.

This will at least help to move towards the goal of 0% CO2 emissions from the heating system by 2050. Safety also needs to be considered.

What are the implications of having hydrogen, possibly in combination with oxygen in manufacturing facilities?

Perhaps the most important remaining questions are:

Where will the green energy come from and how can it be supplied to glass facilities?

Direct electrical heating is by far the most energy efficient method, but will the local electrical grid be able to support the amount of energy needed in the future?

Hydrogen can be stored, but only at the cost of losing another big portion of energy efficiency by cooling down close to 0°K or compressing it up to 600 bar. Will it still be cost efficient?

If opting for hydrogen combustion, would it be advantageous to have both hydrogen and oxygen available to prevent NOx emissions? Will the NG grid be able to support that?

What will it truly cost and can glass manufacturing survive?

It makes sense to figure out the answers to these types of questions first. As part of Schneider Electric, a globally recognized industry partner for energy and sustainability solutions, Eurotherm is able to help find answers and ways for glass manufacturers to move the industry into a green, prosperous future.

*Business Leader Global Glass,
Eurotherm by Schneider Electric,
Worthing, UK
www.eurotherm.com/industries/g...