Treasurer Scott Morrison's display of a lump of coal in Parliament last week could have benefited from more details. Assuming it weighed one kilogram, he could have explained that when burnt in a power station, it would produce two to 2.5 kilowatt hours of electricity, about 2.5 kilograms of carbon dioxide and up to seven grams each of sulphur dioxide and various oxides of nitrogen. It would also produce about 50 grams of fly ash and a few micrograms of heavy metals, including mercury, and some radioactive materials.
Alternatively, if Mr Morrison had displayed one kilo of silicon, he could have explained that it could make about two square metres of solar panels and, at 20 per cent efficiency, with an average five hours of full sun a day, after two days they would have made more electricity than his piece of coal. Then he could have pointed out that modern solar panels are guaranteed for up to 30 years, by which time they would have generated about 2000 kWh of electricity, or about 1000 times as much as his coal lump.
'This letter to the editor by Rory McGuire understates the case for solar panels on two counts, assuming his calculations are predicated on solar radiation inputs to Sydney's Observatory Hill with an average daily input of 16.5 MJ/ m2 ( 4.6 kWh). His statement that 2 m2 of solar panels will produce 2.5 kWh from 2 days with full sun for 5 hours is based on the principle of the lowest common denominator.. 2 days each with 5 hours of full sun applies for winter conditions in June/July whereas average daily solar input for any other season will suffice in exceeding a daily power generation of 2.5 kWh.
Long term power generation from the panels over 30 years amounts to 20,000 kWh based on Sydney's average daily input of solar radiation and hence this is equivalent to 10000 times as much as a lump of coal, I suspect a typographical error has crept into the calculation of the superior performance of solar generators over coal.
My overview is still to to congratulate Mr McGuire on a telling chemistry lesson, even if conservative estimates apply.
March 3rd, 2017'
Thank you, Frank, for considering this matter further