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Cuts into my solar power generation through. So its a trade-off. Interestingly enough, from an energy production perspective the solar panels on the roof result

Cuts into my solar power generation through. So its a trade-off. Interestingly enough, from an energy production perspective the solar panels on the roof result in more reduction in CO2 than the trees do.

jweir 8y ago
Can you prove that or back that up with some facts?
- spydum 8y ago
  I suspect this is because you generate power all year round, while a shade tree doesn’t help heat your house in winter..
- village-idiot 8y ago
  That’s pretty trivial to prove. Grid tied systems sell excess electricity back at bulk rates, at least in some states, which means that the solar panels are producing more electricity than the home needs for cooling. Thus such a house is actually spending negative carbon on cooling, since they’re providing green energy for their neighbors. A shade tree can reduce your need for electricity, but it can’t turn you into a net producer.
  - jweir 8y ago
    Depending on the tree(s), it could be consuming CO2 24 hours a day, year round, solar is just part of the day and only reaches capacity for a brief moment. I don't know the numbers to show the difference. That is why I asked for some facts which the OP seems to know.
    - TallGuyShort 8y ago
      Trees consume CO2 because it's part of photosynthesis, so that's actually on the same schedule as a solar panel's electricity production. At night they're actually continuing to release some of that CO2.
    - village-idiot 8y ago
      A single average fully grown tree can sequester about 88lbs of CO2 per year according to the Center for Urban Forest Research, which is part of the US Forest Service. The average electricity service in the US produces about 1lb of CO2 per kWh, meaning that your solar panel needs to reduce your consumption by only 88 kWh per year below what your shaded house cost would be to be a net positive over a shade tree.
      - VBprogrammer 8y ago
        Don't quote me on this but from memory a tree is able to sequester a lot more in the first couple of years than as a fully grown tree. Intuitively that makes sense.
        village-idiot 8y ago
        Yes, that is true. The carbon sequestration is greatest when the tree is turning CO2 into more tree (e.g. when it’s growing). This process largely stops as a tree hits maturity, and the CO2 is mostly returned when the tree burns or rots. I’m making the explicit assumption that a shade tree will probably be fully grown.
    - CydeWeys 8y ago
      Trees don't really continuously "consume" CO2 in this manner. The only CO2 removed by a tree is the carbon that ends up permanently Incorporated in the wood itself. And if you burn that wood, it's all released back into the air. Even if it just dies and decays, some of it ends up being released.
      - zitterbewegung 8y ago
        Yea, so to sequester the carbon either build something out of it or dump it into the ocean. Maybe build a boat?
        CydeWeys 8y ago
        Rather than sequestering all this carbon into wood and then trying to figure out what to do with the wood so that it doesn't decompose over time and release the CO2 back into the air, it'd make more sense to stop digging up lots of carbon from underground (where it's been stable for hundreds of millions of years in the form of coal and oil) and burning it to release the CO2 into the air. We already have amazing reserves of CO2, and we're digging them up and releasing them by burning them! Trees are just a tiny band-aid on top of this massive harm we're self-inflicting.
        zitterbewegung 8y ago
        Why can’t we do both ?
        CydeWeys 8y ago
        We can and should, but there's more impact to be had from ceasing to dig up the buried carbon and burning it. That's the equivalent of not punching holes in the hull, whereas planting trees is like bailing out the boat -- you'd rather it just didn't leak!
- ChuckMcM 8y ago
  I can tell you how I reason to it. According to many sources, but I will cite this one[1] a single tree converts about 50 lbs of CO2 in a year. There are three trees on my property, a city tree (planted by the city) and two Birch trees planed by the original developer. All are deciduous so lose leaves in the winter but we'll give them full credit anyway, so call it 150 lbs of CO2 a year. My rooftop solar system nominally puts out 5.2 kW of power under full sunlight, although efficiencies cut that down to around 4.8 kW net into the grid. I have over 10 years of data from the system, drilled down though it averages out to about 4.5 "solar hours" per day with an average daily output of about 22 kWH per day or about 8 MWH per year. The US Energy Information Association (EIA) tracks a number of statistics, but the one that is most relevant is the number of metric tons of CO2 per MWH per state. You can see California's number in this report : https://www.eia.gov/electricity/state/california/ https://www.eia.gov/electricity/state/california/ is 474 lbs per MWH. Using that number, my rooftop solar system "saves" (which is to say doesn't generate) about 3,792 lbs of CO2 a year. Which, is way more than the 150 lbs a year the trees are taking out of the air. This is why the 1.2T trees, or 160 per person, is such a large number. A family of four would need to plan 640 trees on their lot, which would remove 32,000 lbs of CO2, which is a lot. To match my solar panels I would need to plant an additional 76 trees. What you can take away from that is that solar panels in places where you can't put trees are a solid alternative. And planting trees rather than letting unused land sit idle as a field of grass is also a good plan. As a home owner, solar, even in places where it won't generate all your energy needs, will help cut CO2 emissions. [1] https://projects.ncsu.edu/project/treesofstrength/treefact.htm https://projects.ncsu.edu/project/treesofstrength/treefact.h...
  - yathern 8y ago
    Good reasoning! I agree with the basic premise - but I don't think you can ignore the CO2 cost to make a solar panel, vs to use one. A tree reduces CO2 as it's being 'built'. A solar panel requires many materials that are refined through various industrial processes - likely some of which produce CO2 - not withstanding the transportation CO2 cost. That all being said, I don't mean to disparage anyone who uses solar panels - and if you already have them (sunk cost) - less trees seems about right, to reduce carbon footprint.
- Robotbeat 8y ago
  It can be shown both bottom-up and top-down, but I prefer the bottom-up: Photosynthesis is usually an order of magnitude more efficient than photovoltaics: https://en.wikipedia.org/wiki/Photosynthetic_efficiency https://en.wikipedia.org/wiki/Photosynthetic_efficiency ...an individual leaf might be peak out at 3% efficient, but it is operating just a portion of the year (maybe about a third to a half at full performance) and also much light gets reflected, absorbed by branches, or misses the leaves entirely. Additionally, photovoltaics peak at 40% efficiency but get about 15-20% efficiency typically and can function the entire year (unless fully covered by snow). And they're displacing electricity produced primarily from fossil fuels which are burned at 30-40% efficiency. Now from a top-down perspective: forests (in this case calculated by replacing cropland with forests) are estimated to sequester about 2 to 10 tons of CO2 per acre per year. https://fas.org/sgp/crs/misc/R40562.pdf https://fas.org/sgp/crs/misc/R40562.pdf In principle, an acre of about 40% solar photovoltaic system with a 25% capacity factor could produce about 3.5GWh per year. But typically, about exactly one tenth that is done in practice: 0.35GWh/year/acre. Since you'd be displacing electricity from the US grid, which is currently about 420 grams of CO2 per kWh (based on my calculations of the most recent eia.gov figures, but you can find similar figures by Googling), that's equivalent to 147 metric tons of CO2 per acre per year for typical photovoltaics (and over 1000 metric tons per acre per year in the idealized case). This person's calculations reach similar conclusions: https://www.solarpowerrocks.com/environment/installing-solar-like-creating-small-mature-forest/ https://www.solarpowerrocks.com/environment/installing-solar... So absolutely, it's better to use solar panels than trees, at least until the grid is fully or nearly-fully saturated by solar. ...BUT once we fully clean the grid, trees have some advantages: 1) they efficiently suck CO2 out of the air and store it, not just produce the energy. That means you can actually draw-down CO2, producing negative emissions. 2) They're scalable. A tree is like a solar farm, CO2 direct air absorption system, and a chemical factory but can be planted as just a seed. It may not be "efficient", but being self-replicating and scalable is pretty powerful.
  - ncmncm 8y ago
    Your first paragraph contradicts the rest, I assume by accident.
ryanjshaw 8y ago
Trees come with a whole bunch of other issues. I have something like 40 trees ranging up to 20m tall. Cleaning up the leaves and branches is a year-round job. Collecting and removing the waste involves time, money and CO2 producing trucks. If not removed promptly, waste left up on my flat roof causes water damage after rains. Heavy storms make me nervous because I've once seen a set of healthy branches large enough to kill me snap right off (this was some time after the storm). Some of the trees also attract rats, which drives my dogs nuts at night and is then a source of anxiety given the high crime rate in our country. Trees along the perimeter of the property have damaged the boundary walls, and other trees have ruined sewerage lines. If you want to plant trees, make sure you understand the potential future costs associated with them.
- londons_explore 8y ago
  In addition, while planting a tree costs only a few dollars, cutting down a 100 ft high tree in an urban space can easily set you back thousands of dollars.
- jonnycomputer 8y ago
  I've had several trees fall this year, on or around my house. Wet year, and windy too. If they're near your house, you need to invest in making sure they're healthy trees! I'm thinking of planting new trees further back from the house, near the creek.
- Kluny 8y ago
  Why do you have a flat roof on a house that's surrounded by trees?
nashashmi 8y ago
So does that mean cut down the forest and put up solar?
- AnthonyMouse 8y ago
  Maybe put up solar in places there already isn't forest.
filesystemdude 8y ago
So, uh, generate the power somewhere other than on shady roofs? Seriously, I don't get the weird obsession with rooftop PV as if it's the only way to be green. PV is great, but, it doesn't work for every house. Personally, I have big oaks out front helping block passive solar windows in the summer, and the peak of my roof runs north-south so cell mounting would be tricky. That doesn't mean I can't get clean energy, it just means I buy it from a utility company, who are buying it from my neighbor's house where the orientation and canopy placement makes sense to do PV.
- hedora 8y ago
  I’d love to see better off-the-shelf solar purgolas, gazebos and other shade generating buildings like that (partial shade greenhouses, maybe?). The backside of solar panels are actually quite pretty, and provide shade + partial rain barriers. This would open up more avenues to passive cooling and also reduce the lock-step replacement of the house’s roof with solar panel installation .
  - wurst_case 8y ago
    This is a fantastic idea which I also recently had. Doing prelim research into how to turn something like this into a side business.
paulmd 8y ago
Shading your house will also cause the growth of moss and dump leaf litter everywhere, which will take off a significant chunk of your roof's lifespan (easily 5 years or more). So yeah you save $10/mo on your a/c bill and you spend that $20k to roof your house every 15 years instead of every 20 years. Let alone if you get a big storm and have some branches or a trunk come down and damage your house. Regardless of the environmental angle, having trees near your house is not worth it financially.
- A2017U1 8y ago
  While I agree with the sentiment of the GP, the reality is starkly different. Most people I know go to great lengths to remove trees near their house. Some insurance companies lower premiums for it. For any elevated property it adds a huge amount of value to kill a nice old established tree in the way of views.

jweir 8y ago

Can you prove that or back that up with some facts?

spydum 8y ago
I suspect this is because you generate power all year round, while a shade tree doesn’t help heat your house in winter..
village-idiot 8y ago
That’s pretty trivial to prove. Grid tied systems sell excess electricity back at bulk rates, at least in some states, which means that the solar panels are producing more electricity than the home needs for cooling. Thus such a house is actually spending negative carbon on cooling, since they’re providing green energy for their neighbors. A shade tree can reduce your need for electricity, but it can’t turn you into a net producer.
- jweir 8y ago
  Depending on the tree(s), it could be consuming CO2 24 hours a day, year round, solar is just part of the day and only reaches capacity for a brief moment. I don't know the numbers to show the difference. That is why I asked for some facts which the OP seems to know.
  - TallGuyShort 8y ago
    Trees consume CO2 because it's part of photosynthesis, so that's actually on the same schedule as a solar panel's electricity production. At night they're actually continuing to release some of that CO2.
  - village-idiot 8y ago
    A single average fully grown tree can sequester about 88lbs of CO2 per year according to the Center for Urban Forest Research, which is part of the US Forest Service. The average electricity service in the US produces about 1lb of CO2 per kWh, meaning that your solar panel needs to reduce your consumption by only 88 kWh per year below what your shaded house cost would be to be a net positive over a shade tree.
    - VBprogrammer 8y ago
      Don't quote me on this but from memory a tree is able to sequester a lot more in the first couple of years than as a fully grown tree. Intuitively that makes sense.
      - village-idiot 8y ago
        Yes, that is true. The carbon sequestration is greatest when the tree is turning CO2 into more tree (e.g. when it’s growing). This process largely stops as a tree hits maturity, and the CO2 is mostly returned when the tree burns or rots. I’m making the explicit assumption that a shade tree will probably be fully grown.
  - CydeWeys 8y ago
    Trees don't really continuously "consume" CO2 in this manner. The only CO2 removed by a tree is the carbon that ends up permanently Incorporated in the wood itself. And if you burn that wood, it's all released back into the air. Even if it just dies and decays, some of it ends up being released.
    - zitterbewegung 8y ago
      Yea, so to sequester the carbon either build something out of it or dump it into the ocean. Maybe build a boat?
      - CydeWeys 8y ago
        Rather than sequestering all this carbon into wood and then trying to figure out what to do with the wood so that it doesn't decompose over time and release the CO2 back into the air, it'd make more sense to stop digging up lots of carbon from underground (where it's been stable for hundreds of millions of years in the form of coal and oil) and burning it to release the CO2 into the air. We already have amazing reserves of CO2, and we're digging them up and releasing them by burning them! Trees are just a tiny band-aid on top of this massive harm we're self-inflicting.
        zitterbewegung 8y ago
        Why can’t we do both ?
        CydeWeys 8y ago
        We can and should, but there's more impact to be had from ceasing to dig up the buried carbon and burning it. That's the equivalent of not punching holes in the hull, whereas planting trees is like bailing out the boat -- you'd rather it just didn't leak!
ChuckMcM 8y ago
I can tell you how I reason to it. According to many sources, but I will cite this one[1] a single tree converts about 50 lbs of CO2 in a year. There are three trees on my property, a city tree (planted by the city) and two Birch trees planed by the original developer. All are deciduous so lose leaves in the winter but we'll give them full credit anyway, so call it 150 lbs of CO2 a year. My rooftop solar system nominally puts out 5.2 kW of power under full sunlight, although efficiencies cut that down to around 4.8 kW net into the grid. I have over 10 years of data from the system, drilled down though it averages out to about 4.5 "solar hours" per day with an average daily output of about 22 kWH per day or about 8 MWH per year. The US Energy Information Association (EIA) tracks a number of statistics, but the one that is most relevant is the number of metric tons of CO2 per MWH per state. You can see California's number in this report : https://www.eia.gov/electricity/state/california/ https://www.eia.gov/electricity/state/california/ is 474 lbs per MWH. Using that number, my rooftop solar system "saves" (which is to say doesn't generate) about 3,792 lbs of CO2 a year. Which, is way more than the 150 lbs a year the trees are taking out of the air. This is why the 1.2T trees, or 160 per person, is such a large number. A family of four would need to plan 640 trees on their lot, which would remove 32,000 lbs of CO2, which is a lot. To match my solar panels I would need to plant an additional 76 trees. What you can take away from that is that solar panels in places where you can't put trees are a solid alternative. And planting trees rather than letting unused land sit idle as a field of grass is also a good plan. As a home owner, solar, even in places where it won't generate all your energy needs, will help cut CO2 emissions. [1] https://projects.ncsu.edu/project/treesofstrength/treefact.htm https://projects.ncsu.edu/project/treesofstrength/treefact.h...
- yathern 8y ago
  Good reasoning! I agree with the basic premise - but I don't think you can ignore the CO2 cost to make a solar panel, vs to use one. A tree reduces CO2 as it's being 'built'. A solar panel requires many materials that are refined through various industrial processes - likely some of which produce CO2 - not withstanding the transportation CO2 cost. That all being said, I don't mean to disparage anyone who uses solar panels - and if you already have them (sunk cost) - less trees seems about right, to reduce carbon footprint.
Robotbeat 8y ago
It can be shown both bottom-up and top-down, but I prefer the bottom-up: Photosynthesis is usually an order of magnitude more efficient than photovoltaics: https://en.wikipedia.org/wiki/Photosynthetic_efficiency https://en.wikipedia.org/wiki/Photosynthetic_efficiency ...an individual leaf might be peak out at 3% efficient, but it is operating just a portion of the year (maybe about a third to a half at full performance) and also much light gets reflected, absorbed by branches, or misses the leaves entirely. Additionally, photovoltaics peak at 40% efficiency but get about 15-20% efficiency typically and can function the entire year (unless fully covered by snow). And they're displacing electricity produced primarily from fossil fuels which are burned at 30-40% efficiency. Now from a top-down perspective: forests (in this case calculated by replacing cropland with forests) are estimated to sequester about 2 to 10 tons of CO2 per acre per year. https://fas.org/sgp/crs/misc/R40562.pdf https://fas.org/sgp/crs/misc/R40562.pdf In principle, an acre of about 40% solar photovoltaic system with a 25% capacity factor could produce about 3.5GWh per year. But typically, about exactly one tenth that is done in practice: 0.35GWh/year/acre. Since you'd be displacing electricity from the US grid, which is currently about 420 grams of CO2 per kWh (based on my calculations of the most recent eia.gov figures, but you can find similar figures by Googling), that's equivalent to 147 metric tons of CO2 per acre per year for typical photovoltaics (and over 1000 metric tons per acre per year in the idealized case). This person's calculations reach similar conclusions: https://www.solarpowerrocks.com/environment/installing-solar-like-creating-small-mature-forest/ https://www.solarpowerrocks.com/environment/installing-solar... So absolutely, it's better to use solar panels than trees, at least until the grid is fully or nearly-fully saturated by solar. ...BUT once we fully clean the grid, trees have some advantages: 1) they efficiently suck CO2 out of the air and store it, not just produce the energy. That means you can actually draw-down CO2, producing negative emissions. 2) They're scalable. A tree is like a solar farm, CO2 direct air absorption system, and a chemical factory but can be planted as just a seed. It may not be "efficient", but being self-replicating and scalable is pretty powerful.
- ncmncm 8y ago
  Your first paragraph contradicts the rest, I assume by accident.

ryanjshaw 8y ago

Trees come with a whole bunch of other issues. I have something like 40 trees ranging up to 20m tall. Cleaning up the leaves and branches is a year-round job. Collecting and removing the waste involves time, money and CO2 producing trucks. If not removed promptly, waste left up on my flat roof causes water damage after rains. Heavy storms make me nervous because I've once seen a set of healthy branches large enough to kill me snap right off (this was some time after the storm). Some of the trees also attract rats, which drives my dogs nuts at night and is then a source of anxiety given the high crime rate in our country. Trees along the perimeter of the property have damaged the boundary walls, and other trees have ruined sewerage lines. If you want to plant trees, make sure you understand the potential future costs associated with them.

londons_explore 8y ago
In addition, while planting a tree costs only a few dollars, cutting down a 100 ft high tree in an urban space can easily set you back thousands of dollars.
jonnycomputer 8y ago
I've had several trees fall this year, on or around my house. Wet year, and windy too. If they're near your house, you need to invest in making sure they're healthy trees! I'm thinking of planting new trees further back from the house, near the creek.
Kluny 8y ago
Why do you have a flat roof on a house that's surrounded by trees?

nashashmi 8y ago

So does that mean cut down the forest and put up solar?

AnthonyMouse 8y ago
Maybe put up solar in places there already isn't forest.

filesystemdude 8y ago

So, uh, generate the power somewhere other than on shady roofs? Seriously, I don't get the weird obsession with rooftop PV as if it's the only way to be green. PV is great, but, it doesn't work for every house. Personally, I have big oaks out front helping block passive solar windows in the summer, and the peak of my roof runs north-south so cell mounting would be tricky. That doesn't mean I can't get clean energy, it just means I buy it from a utility company, who are buying it from my neighbor's house where the orientation and canopy placement makes sense to do PV.

hedora 8y ago
I’d love to see better off-the-shelf solar purgolas, gazebos and other shade generating buildings like that (partial shade greenhouses, maybe?). The backside of solar panels are actually quite pretty, and provide shade + partial rain barriers. This would open up more avenues to passive cooling and also reduce the lock-step replacement of the house’s roof with solar panel installation .
- wurst_case 8y ago
  This is a fantastic idea which I also recently had. Doing prelim research into how to turn something like this into a side business.

paulmd 8y ago

Shading your house will also cause the growth of moss and dump leaf litter everywhere, which will take off a significant chunk of your roof's lifespan (easily 5 years or more). So yeah you save $10/mo on your a/c bill and you spend that $20k to roof your house every 15 years instead of every 20 years. Let alone if you get a big storm and have some branches or a trunk come down and damage your house. Regardless of the environmental angle, having trees near your house is not worth it financially.

A2017U1 8y ago
While I agree with the sentiment of the GP, the reality is starkly different. Most people I know go to great lengths to remove trees near their house. Some insurance companies lower premiums for it. For any elevated property it adds a huge amount of value to kill a nice old established tree in the way of views.