GHung wrote:Crystalline panels are basically silicon (glass) doped with small amounts of 'rare' metals.
Reliability? High in my experience. My first panels are in their 21st year of continuous use and still outputting full power. The performance of my balance-of-system stuff (charge controllers, inverters, etc,) has been stellar as well. The modular nature of the system (each array/controller combination is a stand-alone system) means if there's a failure, the whole system doesn't go down. I have four array/charge controller sub-systems. If one goes down, I'll still have about 75% production capacity until repairs can be made.
Intermittant? Of course. They don't produce unless the sun is shining (produce some on cloudy days). That's why off-grid folks have batteries. Intermittancy is something you can adapt to with a little effort. No big deal here. We also have a diesel generator that charges the batteries; rarely gets used. Off-grid inverters have an input for a generator and manage charging.
Limitations? Unless you have a very large system, you don't want big loads like electric heat, electric hot water, electric stove/oven, etc., though I know folks running smallish high-efficiency heat pumps. Paired with wood heat/ passive solar and solar hot water, along with propane cooking, we live quite well. We have an induction cooktop for when there's a surplus of PV production.
What we do have? Dishwasher, microwave, electric clothes washer (propane dryer and clothes line), lots of electronics, vacuum cleaners, power tools, lighting, toaster, food processors, dog dryers, lots of fans, a small AC unit for the bedroom, electric dehydrators, and lighting of course. Some usually gets used only on sunnier days. Managing surplus production becomes intuitive and can be automated. A lot of surplus gets dumped into our big hot water tank.
pstarr wrote:-snip-
Good. Get more panels. You're rich. And remember to buy plenty of batteries. I recommend molten-salt. They use them in space.
DesuMaiden wrote:-snip-
Are those rare metals rare earth metals?
pstarr wrote:I used to think Nantucket and Martha's Vineyard would be a good bug-out place. I was naive then.
KaiserJeep wrote:DesuMaiden wrote:-snip-
Are those rare metals rare earth metals?
Boron and Gallium are two "dopants" that get "infused" into Monocrystalline Silicon to make photocells. Neither is a "Rare Earth". Boron is a light metal made from Borate ores, and Gallium is a low melting point metal used to make thermometers that are less toxic than those made with Mercury. Very very minute amounts are used in silicon when "doping" semiconductor junctions.
Critical Resources and Material Flows during the Transformation of the German Energy Supply SystemWhen it comes to resource assessments, it is recognised that the overall resource utilisation of an energy system is generally considerably lower if it is based on renewable energies rather than on fossil fuels. The study shows that the geological availability of minerals does not generally represent a limiting factor in the planned expansion of renewable energies in Germany.
The assessment of being “critical” comprises the long-term availability of the raw materials identified, the supply situation, recyclability and the environmental conditions governing their extraction. The expansion of the silicon-based crystalline technology, which accounted for 97 per cent of new systems purchased in Germany in 2012, is non-critical in principle.
Advances in crystalline silicon solar cell technology for industrial mass productionStandard cells are produced using one of two different boron-doped p-type silicon substrates; monocrystalline and polycrystalline. The cells of each type are typically 125 mm (5 inches) or 156 mm (6 inches) square, respectively.
6oz Of Solar Cells High-Efficiency Mono-Crystalline Cells
DOPANT SPECIFICATION OF COMPENSATED SILICON FOR SOLAR CELLS OF EQUAL EFFICIENCY AND YIELD AS STANDARD SOLAR CELLSThe boron specification for standard p-type noncompensated multi crystalline silicon solar cells are typically 0.05-0.15 ppmw B.
Major countries in boron production from 2010 to 2013Turkey annual production of Boron: 3,000,000 metric tons
Yes, we use fossil fuels to create devices that can then supply energy for several decades without any further fossil fuel input. Instead of directly consuming the fossil fuel as a feedstock. Which enables us to greatly expand the amount of energy we get out of that initial investment of fossil fuel. The extra energy does not harm the biosphere nearly as much if we had to generate an equal amount of energy burning fossil fuels directly as a feedstock. Saves on pollution and stretches our dwindling supply of fossil fuels, a win/win. They can also be recycled at the end of their life at a fraction of the fossil fuel cost used to create it.sunweb wrote:The devices that are used to capture the sun and wind’s energy are an extension of the fossil fuel supply system. There is a massive infrastructure of mining, processing, manufacturing, fabricating, installation, transportation and the associated environmental assaults. There would be no sun or wind capturing devices with out this infrastructure.
If we have to use fossil fuels to manufacture renewable plants, doesn't it mean that renewables are useless?if we have to use fossil fuels to manufacture renewable plants, doesn't it mean that renewables are useless? Raugei's answer is a resounding "no". In fact, the EROEI of fossil fuels acts as a multiplier for the final EROEI of the whole process. It turns out that if we invest the energy of fossil fuels to build renewable plants we get an overall EROEI around 20 for a process that leads to photovoltaic plants and an even better one for wind plants. So, if we want to invest in our future, that's the way to go, until we gradually arrive to completely replace fossil fuels!
It seems that this argument is too often brought up to imply that, since PV development and deployment is currently (largely) underpinned by fossil energy, and hence PV is not (yet) a fully independent and truly 100% renewable energy technology, then "why bother" in the first place?
It is worth looking at the issue from another angle. Let us assume that the average EROI of the current mix of fossil fuels (which still represent our main sources of primary energy, globally) is some value X > 1. And let us also agree that we (as a society) need a large and ever-growing share of our energy budget in the form of electricity (to power our computers, telecommunications, trains, home appliances, etc).
Broadly speaking, we therefore have two options:
1) keep using all the oil (and other fossil fuels) directly as FEEDSTOCK fuel in conventional power plants. In so doing, we would get out roughly 1/3 of the INPUT energy as electricity (electricity production efficiency in conventional power plants being ~0.33). This would be the "quick and dirty" option, that maximizes the short-term (almost instantaneous, in fact) "bang for the buck".
2) Use the same amount of available oil (and other fossil fuels) as (direct and indirect) INPUT for the production of PV plants.
Building and deploying a modern crystalline silicon PV system requires approximately 3 GJ of primary energy per m2. What this means is that the c-Si PV system would provide an output of electricity roughly equal to 18/3 = 6 times its primary energy input, which corresponds about 6/0.33 = 18 times the amount of electricity that we would have obtained, had we burnt the fuel(s) as FEEDSTOCK in conventional power plants (option 1 above), instead of using them as INPUT for the PV plant.
A planned long-term investment might be advisable, for instance, aimed at bringing about a gradual transition. The latter is in fact what many have been advocating, often only to be met with rather negative ‘gloom and doom’ reactions by others on a number of prominent discussion forums. It seems as if, in the minds of the latter, the desire to show that ‘the emperor has no clothes’ (i.e. that PV and other renewables are not yet, and might never be in full, a real, completely independent and high-EROI alternative to fossil fuels) overrides all other considerations, and prevents them from realizing/admitting that, after all, it may still be reasonable and recommendable to try and push this slow transition forward.
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