Welcome to the Glass Age

115 as more renewable electricity becomes available, hydrogen will become affordable. But why consider hydrogen? If electricity is used directly, the furnace melting efficiency is much higher than via the hydrogen route. An advantage of hydrogen is the possibility of storage for long periods, allowing long-distance transportation and creation of a buffer against supply hiccoughs. Storing electricity for similar times is simply not efficient. Unused batteries slowly lose power while storing sufficient energy would require huge batteries. Different storage options are shown in Figure 7.5; some, such as hydro power have been created but are not universally applicable, mountains and water reservoirs, as in Norway or Austria being necessary. Energy storage today is facilitated by methane which can be stored for millennia in caves with appropriate geology [10]. All-electric melting Electric melting has been a proven technology for over a century so why not convert all furnaces to all-electric melting? Mainly because electricity typically costs three times that for natural gas /kWh. While electric melters are twice as thermally efficiency, they are more expensive to operate. Another obstacle remains. Most electric melters are producing less than 80 TPD. Only a handful in the entire world melt more than 100 TPD; and only two have produced 200 TPD —both were stopped due to production issues. All-electric melters greater than 200 TPD, have diameters so large that maintaining a well distributed insulating batch blanket across the melt surface is difficult although a key requirement for keeping the furnace operational. Should the batch cover disappear, the furnace loses heat from the top, the glass cools, melt quality and pull rate fall and production deteriorates. There is also limited long-term experience at that size of producing reduced colored glasses or melting with high cullet levels. Figure 7.5. Showing the capacity and discharge times for different storage technologies. Source: RMIT.