08-27-2018, 02:24 PM
quote:
Originally posted by Jeremy Lutes
"...environmental effects ... associated with the manufacturing of solar PV panels and the required batteries to make that technology compatible with a modern society..."
Yeah, let's talk about those.
https://www.ucsusa.org/clean_energy/our-...power.html
TLDR: "Most estimates of life-cycle emissions for photovoltaic systems are between 0.07 and 0.18 pounds of carbon dioxide equivalent per kWh"
and:
https://www.ucsusa.org/clean_energy/our-...nergy.html
TLDR: "Enhanced geothermal systems, which require energy to drill and pump water into hot rock reservoirs, have life-cycle global warming emission of approximately 0.2 pounds of carbon dioxide equivalent per kWh."
So, PV is slightly better. Yes, there are some hazardous chemicals used in PV cell manufacture. Can you claim that none are used in fabricating a geothermal plant ?
Now we have apples (PV non-baseload), oranges(PV baseload w/utility scale storage), pears (geothermal steam/binary baseload) and potatoes (Enhanced geothermal) in the mix. The Union of Concerned Scientists make no mention of battery storage (although they did note the much larger land-use impact for solar compared to wind...) which also has some CO2 and environmental impacts associated with mining and and refining of lead/lithium/vanadium/pick your battery poison for the utility scale storage.... And since we were talking about toxics associated with geothermal, a list of some of those used in PV manufacture include: "cadmium telluride, copper indium selenide, cadmium gallium (di)selenide, copper indium gallium (di)selenide, hexafluoroethane, lead, and polyvinyl fluoride. Additionally, silicon tetrachloride, a byproduct of producing crystalline silicon, is highly toxic."
These are pretty much essential to the fabrication of the PV systems; I can't think of too many that play as large a role in the fabrication of the bulk of the geothermal equipment - the electronics for the control systems undoubtedly would involve similar chemical processes for production of any electronic gear. But the bulk of the mass of a geothermal facility would be conventional steel refining.
And the numbers selected for Enhanced Geothermal aren't really relevant to Hawaii's geothermal - at least to the present date - since that technology hasn't been used in Hawaii and (as far as I am aware, hasn't been proven to be commercially viable) at current oil prices.
Possibly more relevant in terms of carbon footprint is that enhanced geothermal usually involves lower temperatures and more and deeper drilling than has been traditionally done in Hawaii so the CO2 footprint per MWe generated for enhanced geothermal would be substantially higher than the flash steam/binary that is used by PGV.