Readily available raw materials in most countries, chemical inertness, almost unlimited recyclability, durability, transparency, light reflectance and cleanliness – these are among the properties of glass that have encouraged its myriad uses.
The glass industry maintains a long-term global growth rate of around 4% per annum, partly driven by the trend for architects and vehicle designers to continuously increase the glass content of their creations.
Glass manufacturing now faces the combined challenges of gearing up to meet rapid demand growth from emerging new products and developing energy resources compatible with environmental and cost pressures that increase daily.
Product range & market growth
Approximately 140 million tonnes of glass will be produced in 2009 for use in the manufacture of a vast array of modern products.
Around half of this tonnage will go into glass containers, a third into the production of flat products including architectural products, furniture and automotive windows and the remaining sixth into all other products ranging from fine handmade glassware, optical lenses and laboratory equipment, to lighting products, glass fibre products for insulation and structural reinforcement, optical fibres and display products for electronic applications and television screens.
The demand for innovative functional glass materials, developed to add value to high volume products, is growing faster than that of basic glass. Insulating Glass Units combine solar control coatings with self-cleaning properties and are an excellent example now used for about 80% of all new glazing in North America, Germany and other European countries.
The long-term growth in glass output of 4% can be expected to moderate to around 3.2%, resulting in an estimated 2015 total of about 170 million tonnes.
The embodied energy of glass is significantly lower than that of commonly used materials like PVC, synthetic rubber and aluminium, but it is considered an energy intensive industry because energy needs account for up to 20% of total production costs.
Around 80% of this energy is sourced from fossil fuels, with the remainder made up by electricity and the resulting high volumes of carbon dioxide emissions proving to be a major environmental threat affecting climate change.
Over the past 50 years cost competition has motivated intensive efforts to improve the specific energy consumption to levels barely one third of the average in 1960, which also reduces emissions. Much of this progress can be attributed to the introduction of oxygen-fuel (oxy-fuel) burners that significantly affect the fuel efficiency of melting furnaces.
Replacing air that contains 78% of inert nitrogen with oxygen eliminates the massive source of sensible heat loss through the flue gas; the emission of toxic nitrogen oxides is also reduced by oxy-fuel technology and the glass industry today consumes around 12,000 tonnes per day of oxygen worldwide.
New demand for solar glass
The glass industry has introduced products that have the potential to reduce global emissions of carbon dioxide by reducing energy losses from buildings, but it is poised to contribute more directly to the manufacture of photovoltaic (PV) solar absorption panels.
These units are being deployed in large solar farms and on the rooftops of large retail stores, to generate electricity for both commercial and residential use.
Starting in the 1970s, PV modules were made from crystalline silicon using similar technology to semiconductors. The high cost of their production means that power generated using coal or natural gas is still cheaper and this limits their market potential.
Today however, thin-film PV technologies based on the use of amorphous silicon and other semiconductor materials have drastically lowered the cost of PV modules – bringing the cost of electricity produced via PV much closer to parity with the cost of grid power.
When parity is reached the potential demand for PV modules is expected to grow very rapidly, given the worldwide cost and environmental pressures impacting on the established electricity producers.
Representing less than 0.1% of total global glass production in 2007, projections based on the expected growth of PV technology indicate that the market for low-iron solar float glass will grow to exceed 1% by 2012 and become a major market segment by 2015. The volumes estimated would require over 20 dedicated glass lines in 2012 and over 100 by 2025.
Apart from the potential demand for oxygen in new float lines, the PV industry also requires many other speciality gases including silane, ammonia, phosphorus oxychloride, hydrogen, nitrogen and nitrogen trifluoride, which support the fabrication of thin film devices.
Latent potential for strength
Glass sheets of various qualities are a vital component in the manufacture of both crystalline and amorphous silicon PV panels and industry experts predict a compound annual growth rate of 30-40% for this market.
The global consumption of solar glass in 2007 totalled less than 0.1% of global glass production and primary glass manufacturers are justifiably wary of hasty investment based on market hype.
However several key factors are driving the demand for PV capacity:
* Government subsidies with Germany and Spain leading the way
* Security concerns over energy resources in many countries
* Soaring oil and natural gas prices
* Environmental imperatives to cut greenhouse gas emissions
* Burgeoning demand for energy in developing economies
Glass has been the preferred material for many housewares for 3500 years and the range of applications for glass is still expanding, while many substitutes have come and gone.
The favourable properties that explain its popularity do not include strength, for despite the immensely strong chemical bond formed between oxygen and silicon atoms in the structure of glass (confirmed by laboratory tests on pristine samples at 13.8 kN per square millimetre) glassware is very brittle and easily broken.
Is this fragile nature enforcing something of a glass ceiling for applications then?
The design strength of common glass products is only 0.05% of this value. It is understood that fractures in glass originate from surface flaws that concentrate the effective stress, causing the flaw to undergo subcritical crack growth until failure is imminent.
It is widely recognised that if the strength of glass could be increased by a factor of 20 or 50, then the opportunities to use glass for new applications would be enormous.