Friday, July 14, 2017


In the USA –
“Glass manufacturing accounted for 1% of total industrial energy use in EIA's most recent survey of the manufacturing sector. Overall fuel use is dominated by natural gas (73%) and electricity (24%), with the remaining share (3%) from several other fuels. Natural gas use at glass manufacturing facilities in 2010 was 146 trillion Btu, about 143 billion cubic feet. 

If we convert the natural gas to kWh, we get:
143 billion cubic feet Natural Gas  =  41,909,163,034.63 kWh

Annual output, 1,301 GWh (125 MW avg. power). Website Topaz Solar Farm is a 550-megawatt (MW) photovoltaic power station in San Luis Obispo ...
Construction cost‎: ‎$2.4 billion
Construction began‎: ‎2011
Annual output‎: ‎1,301 GWh; (125 MW avg. power)
Capacity factor‎: ‎24.4% (2014-2015)

From above:
143 billion cubic feet Natural Gas  = 41,909,163,034.63 kWh
The Annual output of Topaz Solar Farm is:
1,301 GWh  = 1301000000 kWh
It would take 32 of these installations to replace the energy
used for just the glass made in the USA in the year 2010. 
That would be 288,000,000 solar panels.
10 Mahattans
Almost 46,000 Football fields.

The sun shines during the day and not every day.
So of course the energy would need to be stored because glass factories run 24/7 365 days/year for up to 18 years.

The USA is only a part of the glass manufacturer globally.

Even though flat glass accounts only about 16% of the global glass industry, most information on market structure focus on this segment. The global market for flat glass in 2010 was approximately 56 million tonnes. This is dominated by Europe, China and North America, which together account for around three-quarters of global demand for flat glass. Of total global market demand in 2010, it is estimated that 33 million tonnes was for high quality float glass, 1 million tonnes for sheet glass and 2 million tonnes for rolled glass. The remaining 20 million tonnes reflects demand for lower quality float, produced mainly in China. The significance of China as a market for glass has been increasing rapidly since the early 1990s as the country has become more open to foreign investment and the economy has expanded. In the early 1990s China accounted for about one fifth of world glass demand, but now accounts for 51%.

.  .  .  the energy intensity of continuous glass furnaces in Europe and the United States were reported as 4-10 GJ/t of container glass and 5-8.5 GJ/t of flat glass.

Each week, between 350 and 400 float glass lines
around the world yield about 1,000,000 tons of glass.

The Float Glass Process
The dominant method of making flat glass is the float-glass process. First, after mixing the raw ingredients in the batch house, they are fed into the furnace and melted at 1550 °C.   [2822F]
Thereafter, the melted glass flows onto the top of a bath filled with molten tin at 1050 °C. [1922F]  The atmosphere in the bath is a mix of nitrogen and hydrogen that prevents the oxidation of the tin. Because tin has a higher density than glass, the glass spreads out on top of the tin, giving it a smooth, even surface. Some tin incorporates into the surface of the glass in contact with the bath, this side of the glass is referred to the tin side, as opposed to the air side. Next, the glass passes into the annealing lehr, a long oven with a temperature gradient, where the glass is slowly cooled to 40 °C to prevent it from cracking [14]. It is also possible to apply a coating (anti-reflection, TCO, etc.) either within the tin bath or just after the tin bath via chemical vapor
deposition. Finally, the glass is inspected for defects, coated with Lucite separating media to prevent scratches when the glass is packed and shipped, and cut to the required size.


How Glass Is Made

Float plants normally are sited near a silica source, and often near a customers facility, to minimize transportation costs, which can be 15% of total costs. Also, they often are built in areas with low electricity costs, since the float process is energy-intensive; a plant uses 14 million therms (410 million kilowatt hours) of energy per year.

Most photovoltaic modules use glass. Crystalline-silicon technologies use glass cover
plates to provide structural strength to the module and to encapsulate the cells. Thin-film solar technologies also often use glass as the substrate (or superstrate) on which the device is built [3]. In fact, for the majority of solar modules in production, glass is the single largest component by mass and in double glass thin-film PV, and it comprises 97% of the module.

It is important to understand that this is not the only high temperature process required for an industrial world.  See chart below. 


  1. It would be extremely interesting to know the relevant figures for container glass - beer bottles, etc .. as these can be REUSED (shock horror) .. I try to explain to my students - that the energy contained in a glass pop bottle is often 1000x that contained in the contents! . and then we throw it away...

    1. Almost all glass can be reused. It still requires mechanical crushing and the extreme heats plus the collecting and transporting. My goal was to show that the extreme heat requirements usually provided via natural gas would require massive amounts of panels. And still not be adequate for 24/7 operation.

  2. Other major industrial processes are also continuous. The extensive infrastructure and associated material logistics are all designed around continuous production, so converting to a daily sun driven batch process is nigh impossible. I know of no technology that can store thermal heat at these temperatures. Even if it existed, it would exact a high conversion inefficiency.

    Another good compilation of evidence that is out there, just being ignored.