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diy solar

The US government opens 22 million acres of federal lands to solar

MTM98290 said:
Centralization is the opposite of what being a good steward is about. These PUBLIC lands shouldn't be destroyed by this disgusting scheme.
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So elevate the panels and keep the public lands underneath full of meadows. No "destruction of public land."

Or better yet, do it over farms. Higher farm production AND the farmer can then sell the power to make more money.
 

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billvon said:
So elevate the panels and keep the public lands underneath full of meadows. No "destruction of public land."

Or better yet, do it over farms. Higher farm production AND the farmer can then sell the power to make more money.
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Most crops don't like shade. Animals would probably be fine but grass grows better in sunlight than shade and grazing animals eat grass.
 
Dave911 said:
Most crops don't like shade. Animals would probably be fine but grass grows better in sunlight than shade and grazing animals eat grass.
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In many areas, grass grows slightly better in partial shade than in either full shade or full sun, due to reduced water demands in full sun. Row spacing and bifacial panels will help with this.
 
billvon said:
Well, let's do the math.

Solar PV is now about 23% efficient and has an albedo of .3. That means that 23% of the energy falling on it is converted to electricity and 30% is reflected back out. That means that of the energy hitting the panel, 47% is wasted as heat. That gives an overall thermal efficiency of 32%. The average efficiency of a coal fired power plant is 33%. So if you replaced coal power plants with PV, the heat wasted per unit of energy generated would be a wash.

Of course that doesn't account for CO2 emissions, which tend to trap heat and do a lot of warming. PV wins there.

It also assumes that the land had an albedo of 100% before you put the solar panels there - but that's never true. So let's look at it from a total heat generated in a given area approach. Like I mentioned, solar panels have an albedo of about .3 and an EFFECTIVE albedo of .53. This is because the absorbed energy isn't all turned into heat; some is turned into electricity, and Maxwell says there's no free lunch - so that energy going away from the panels via the wires can't warm up the panel any more. Some other common albedos:

Fresh asphalt 0.04
Open ocean 0.06
Worn asphalt 0.12
Conifer forest 0.12
Tar roof 0.12
Deciduous forest 0.17
Bare soil 0.17
Tile roof 0.20
Green grass 0.25
Desert sand 0.40
New concrete 0.55
Ocean ice 0.50 to 0.70
Fresh snow 0.80
Aluminum 0.85

This means that if you replace forest, plain dirt, grass or desert with panels, the overall heat absorbed by the area goes down. And of course if you cover roads or roofs with panels the heat absorbed goes WAY down.

"But wait" you say. "I see more rising air over solar farms than over forests!" That's definitely true. Forests generate far more heat - but they are also transpiring water. And it requires a lot of heat to evaporate water, which is why forests are often cooler. The total heat absorbed is higher, but it's locally cooler.

And of course Maxwell still gets his say, and that heat is returned to the system when that water condenses in the form of clouds, rain, snow or dew.
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I don’t see calculations on how much heat the back side of the panels radiate toward the ground?
 
Dave911 said:
Most crops don't like shade. Animals would probably be fine but grass grows better in sunlight than shade and grazing animals eat grass.
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Water
In experiments testing evaporation levels under solar panels for shade resistant crops cucumbers and lettuce watered by irrigation in a California desert, a 14–29% savings in evaporation was found,[1] and similar research in the Arizona desert demonstrated water savings of 50% for certain crops
Source: https://en.wikipedia.org/wiki/Agrivoltaics
 
History keeps reminding me that taking water from where it has been and moving it to somewhere it is not has far reaching repercussions that were not factored in or anticipated.
Often, these repercussions cripple a productive area and the intended benefit ends up being temporary at best.
 
Imagine all the cheap "used" solar panels that will come up for sale when criminals realize they can drive out into remote areas and steal the panels.

This is another of the hair brained ideas the government comes up with.
 
HowlerMonkey said:
History keeps reminding me that taking water from where it has been and moving it to somewhere it is not has far reaching repercussions that were not factored in or anticipated.
Often, these repercussions cripple a productive area and the intended benefit ends up being temporary at best.
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Are you talking about human involvement? Or natural movement such as Lake Bonneville and it's great flood?
 
fromport said:
Water
In experiments testing evaporation levels under solar panels for shade resistant crops cucumbers and lettuce watered by irrigation in a California desert, a 14–29% savings in evaporation was found,[1] and similar research in the Arizona desert demonstrated water savings of 50% for certain crops
Source: https://en.wikipedia.org/wiki/Agrivoltaics
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But is growing crops in a desert an efficient use of water? When its already in short supply?
 
Finally someone is using their brains. This article is about putting solar panel structures over the existing aqueducts.

theconversation.com

First solar canal project is a win for water, energy, air and climate in California

Covering the state’s canals with solar panels would reduce evaporation of precious water and help meet renewable energy goals – all while saving money.
theconversation.com theconversation.com

They are now looking to put solar panel structures over the existing water canals / aqueducts. This is the type of green energy project that makes sense! 1) You’ve already have impacted the environment so you’re now concentrating/localizing the impacts to where humans are already present. 2) Covering even a small portion of the aqueducts reduces water lose due to solar evaporation. Thirsty people and plants now will have more available water. 3) Access to the power grid is close by. It’s easier access to the power grid because you don’t have to run miles of interconnections to reach the grid unlike those remote desert solar farms. This means less power loses too. 4) Easier access to maintain/ repair these systems. The access, roadways, etc are already in place.

This is GOOD environmental stewardship. Cover/use our existing areas like warehouses, parking lots, etc. first then use the untouched areas if absolutely needed. The only negative might be to those who fish these canals. They might loose some of their lures/gear to the structure. But they will get a bit of shade.
 
Woody said:
put solar panel structures over the existing water canals / aqueducts
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all good points,
on the other side of this, canals are wide, requiring steel structures to span them may be costly,
Will the water/vapour below the panles induce corrosion in the structure, or PV or wiring.
canals need occational cleaning - dredging - maintenance, will the PV and support structure will be in the way for these operations.
Will workers installing and maintaining PV over open water be at greater risk.
Some perhaps interesting or neutral impacts:
If we build PV arrays over the canals, does the combination of water and cover invite birds to nest, bee hives, bats, vegatation to grow up under the PV or other unintended consequences that may be good or bad (for the area or the PV array) that we should consider prior to building.
 
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