You may have seen this article about a couple who’ve been ordered by a California court to cut down their redwood trees because their neighbor built a solar panel thus they’re in violation of California’s Solar Shade Control Act.
What I wonder about is a statement in the article from Kurt Newick who sells solar panels
It seems that he’s overstating the amount of CO2 that a solar panel can save, as well as understating the amount of carbon a tree absorbs (especially a redwood). Especially when you consider that the trees provide shade and therefore lessen the amount of AC needed
The only cite I can find about the amount of CO2 a tree sequesters is from this page,which states a figure about 3 times the figure from Mr. Newick, though granted they’re talking about a mature tree vs. an average tree. It occurs to me though that a large tree contains tons of carbon and that both figures may be understated.
So, what’s the true benefit of solar panels vs. trees?
Even if we assume that hydro and nuclear accounts for 25% of California’s electricity then we’d have 1.5pounds of carbon per kilowatt day, or 9lbs of carbon/day then the solar panel saves 3285 lbs of carbon/year or about 65 times one tree’s savings in carbon (assuming about 50 lbs/year, not the 14lbs cited in the Mercury News article). That’s an amazing difference.
This article says that these Redwoods were planted from 1997-1999 and are now 20-40 feet high after roughly 10 years. Surely these trees weigh several tons.
Yeah, but how much of that is carbon? Remember, cells are mostly water.
Anyway, here’s an on-line calculator. I typed in 100cm for a circumference and got 215 kg of carbon. Note: redwoods get very tall while they are still very skinny.
But if they cut the tree down they’ll have to build something with the lumber, or else all of the carbon will be released as the wood decomposes. At 5 pounds per day it would take a long time to overcome the carbon deficit created by the composting of tons of redwood.
I’d be very surprised if the numbers for solar panels quoted in the OP include the lifetime emissions/offsets of solar panels.
I suspect that if you look at all of the emissions from assembling, transporting and installing (and ultimately disposing of) the solar panels, you would have quite a different score. Lifetime emissions from any tree would be substantially smaller.
BTW, this is a local story for me, so I’m quite familiar with it. The folks with the trees didn’t actually cut them down-- they trimmed the “offending” branches back to the trunk, leaving some branches on the bottom and the top. Looks kind of silly, but I guess they were trying to make a point.
Do solar panels have a usable lifespan, or are they relatively immortal? Do they have parts that wear from constant exposure to and collection of UV radiation?
The point is the Sun is good for trees, and redwoods are a very long-lived species of tree. Do solar panels share that same lifespan?
If they’re on a house, they wouldn’t, because the house would be razed before the tree expired, if left alone.
Well, if you’re unwilling to enforce existing laws, then you shouldn’t be a judge. This wasn’t just some random call, there actually is a law in CA that covered this situation. The legislature is looking at changing it, though, so that whichever was there first has precedent.
This shouldn’t be a “trees vs. PV” argument. I like trees as well (maybe more) than the next guy.
However, If one is going to make the argument that it makes more sense to spare a tree, because it will sequester more CO2 than a PV array will save, then I think one should be prepared to lose.
Most sources give the energy-payback time for a solar panel to be two years. If an array has a lifetime of 25 years (the standard warranty), then in 23 years a 1KW array will save 100,000 lbs of CO2 (50 tons), which is certainly more than a single tree will. Besides, trees are only short-term carbon sinks. We need to keep the CO2 out of the atmosphere to begin with.
Yes, that site is interesting but that calculator only gives you how much of the weight carbon, not how much the tree weighs as a whole which is what I was wondering. In your example the tree has 215kg of carbon (Amount of carbon dioxide CO[sub]2[/sub]-e 787 kg), but how much weight does the tree have in total? Key Lime Guy answered this question for me.
Yep, it makes sense to me. It’s another way of expressing the lifetime impacts/benefits of trees vs. solar panels. Solar panels are pretty long-lived, but they do have an enormous impact during their construction (i.e. extracting, distributing and assembling the materials).
If we assume the solar panel sprung into being the way the tree did, without producing any emissions along the way, the solar panel is obviously better. Is that a reasonable assumption?
The whole issue of carbon fixing seems something of a red herring to me. Otherwise, you have a situation where the supporting evidence for solar panels gets worse as things get better. The calculations all assume carbon fixing for trees versus carbon emission savings for solar panels; if solar panels aren’t replacing power that requires carbon emissions to generate, the argument fails.
If we assume the original source of power is hydro electric, whose output is determined by the source of the water driving the turbines, then it doesn’t fail. Any excess power would be sold off to another utility, eventually reaching one that uses fossil fuels. I believe nuclear power plants also have a fairly fixed output, but coal-based plants can be demand-driven.
