What is the typical embodied energy of a solar photovoltaic panel?

Question

What is the typical embodied energy of a solar photovoltaic panel, in terms of nominal power output or panel area? The ideal answer would be in kWh/W_P, but kWh/m² would also be acceptable.

I understand there is probably a range of answers to this question, so here are some simplifying assumptions:

• If the manufacturing process is more efficient for larger panels, then the answer for large panels (best case scenario) is preferred.
• If the manufacturing process has become more efficient over time, then an answer for the most modern and efficient process (best case scenario) is prefered.
• If different manufacture technologies (monocrystal, polycrystal, thin film) have different amounts of embodied energy, then the lowest answer (best case scenario) is preferred.

Answer 1

According to the Wikipedia article on EROI, 585 kWh/m² is a median value for the embodied energy of a photovoltaic panel, rated based on surface area.

The "energy invested" critically depends on technology, methodology, and system boundary assumptions, resulting in a range from a maximum of 2000 kWh/m² of module area down to a minimum of 300 kWh/m² with a median value of 585 kWh/m² according to a meta-study. ^[9]

Assuming a panel efficiency of 20% (typical of commercially available panels) and solar irradiance of 1000 W/m², 1.0 m² of panel would have a peak power output (W_P) of about 200 W/m². Or stated differently, it would take about 50 cm² of panel to deliver 1 Watt, and manufacturing that panel would use about 2.9 kWh of energy.

So as a rough back-of-the-napkin calculation, the embodied energy of a solar panel, normalized for peak power output, is about 2.9 kWh/W_P.

Answer 2

Energy payback in 1-6 years

Taking manufacturing variables into account basically gives you a range of time from 1.25 - 6.5 years based on 5 sunny days out of seven and an average of 6-8 hours of sun per day.

But in reality none of this matters, here’s why...

Fossil fuels never reach energy payback

Electricity as a commodity has been in use for over a century, it isn’t going away in our lifetime. A better question is, “What’s the best way to produce it?”

If you look at the embodied energy of a coal plant, or even a modern high efficiency natural gas generator, how long does it take to earn back their embodied energy? The answer is they never do. We forget, or more accurately ignore the fact that once you build a coal plant, or gas fired turbine, you then have to feed it fuel the rest of its life which it converts to electricity at a rate somewhere less than 100%. So they keep digging themselves a deeper and deeper embodied energy hole they can never crawl out of.

At least the solar panel, water wheel and wind turbine can one day get even. This is why renewable energy as a whole is better for us environmentally and economically than any form of fossil based fuel source.

Answer 3

If the "embodied energy" of photo-voltaic tech is ~585kWh/m^2 and it generates ~0.2 kW/m^2 then; the answer to the question seems to be that the photo-voltaic tech will need to run for:

~(585kWh/m^2)/(0.2kW/m^2) hours = 2925 hours to generate it's embodied energy; yes ?

Answer 4

Typical period would be 2 years for embodied energy payback, using a nominal 200 peak watt per square meter and 600 kWh embodied energy.

Sunny regions have over 5 peak solar hours per day and more typical locations are around 4 hours. 200 W x 4 h = 0.8 kWh per day generation - Then 600 kWh / 0.8 kWh/day is 750 days or 2 years. Panels are rated for 25 years and can exceed that. So 25 years of free energy is likely (after embodied energy payback). I agree with others who say it doesn't matter, this embodied energy question and the question of ensuring we will recycle solar panels are red herrings. Panels can and must be recycled and societies will have to embrace that - solar PV is an astoundingly good invention that is improving incrementally. Perhaps it's more astounding that rooftop PV is not already the default standard for new construction energy systems. The world is still largely ignorant of the tremendous environmental and economic benefit of switching to household PV. Household is the best approach because the end users receive the economic benefit of the system - why cede that to energy utilities? Getting off fossil fuels is also key to global stability. Notice that many of the bad actor/dictatorship nations are the world's oil and gas barons. Every individual who embraces solar PV is one more step towards disenfranchising the tyrants. Wind energy is of course also laudable in that regard.