http://environmentalprogress.org/big-news/2017/6/21/are-we-headed-for-a-solar-waste-crisisSolar panels create 300 times more toxic waste per unit of energy than do nuclear power plants.
Okay, fair enough. Now, how does the article define "toxic waste" then?
The study defines as toxic waste the spent fuel assemblies from nuclear plants and the solar panels themselves, which contain similar heavy metals and toxins as other electronics, such as computers and smartphones.
e.g. they're equating spent nuclear fuel rods with the
entire mass of the "solar panels themselves", not the quantity of heavy metals contained therein. It's just noted that they
contain heavy metals, but the heavy metals aren't what they're weighing. Solar panels actually consist of less than 0.1% heavy metals, e.g. they're out by a factor of 3000, and that's going off their own numbers.
EDIT e.g. I looked up their footnotes and found that they used this panel as their basis
http://static.trinasolar.com/sites/default/files/PS-M-0474%20A%20Datasheet_Duomax_PEG5.XX_US_Feb_2017_A.pdfand
EP estimated that a typical 1 GW nuclear reactor produces 27 tonnes of waste annually.
1GW of nuclear would make 365*24 = 8760 GWh per year. So, it makes 27,000 kg of nuclear waste for each 8760 GWh produced. e.g. the rate of waste for nuclear according to their study is 3 kg of waste per 1 GWh.
Ok, lets see how much power the cited panels should make and how much they weigh. Each panel is 24 kg, and there are 60 panels. The whole system is rated as a 270 Watt system.
Google states that a 1000 Watt system will make ~500 KWh per year. So 270 W * 500/1000 = 135 KWh per year. But, let's also assume that by 25 years the panels have worn out, e.g. they're at zero% left, which means we halve the average output, meaning ~70 KWh per year. This means over 25 years it make 1750 KWh, or 1.75 GWh. Dividing the weight by the amount of energy produced and we get 822 tons of solar panels for each GWh produced, which is right on top of their "300 times" figure. e.g. what they're classifying as "toxic waste" here is obviously the
entire mass of the solar panels.
But here's the big "but". I had to make a big
error to get the figure to work out like theirs: I needed to assume that the 24 kg was per-cell, not per-panel. If you take that assumption out, then the weight of the entire panel goes down by a factor of 60. Meaning their entire math only works out if you make a huge math error, inflating the weight of the panels by a factor of 60, while also assuming that the panels degrade quickly and/or have a very low conversion rate of power.
Running some
proper maths, a 23.5 kg panel consisting of 60 cells generates 270 Watts. Assuming 1% deterioration per year and that they're replaced at 25 years, then you have ~90% power, and the conversion factor that 1 KW of capacity generates about 500 KWh per year. Meaning you expect 270 * 500/1000 * 0.90 * 25 = 3037 KWh ( e.g. 3 GWh) of power for a 25 year lifespan panel weighing 23.5 kg. The
total kg per GWh is therefore about 8 kg, not 800. And then, if you want to calculate the "toxic" part, you actually need to divide by 3000, meaning about 3 grams of toxic materials per GWh vs the 3 kg of the same for a nuclear plant,
plus the stuff that comes out of nuclear plants is
worse. Meaning that they were probably out by an actual factor of
300,000, not 3000