Solar, Wind Renewable Energy

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Rianne said:
Wow! And we have the Mojave Desert with a bunch of useless sand.
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Well, there's plenty of land, but it takes money to build these huge solar plants.

And add to that the cost of the batteries too.


Experts estimate that in the near future, photovoltaic plants with a total capacity of around 60 million MW will be needed to supply the entire world with cost-effective electricity. That's 70 times more than all the existing solar capacity so far.
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Here is a neat short video about solar panel heat buildup and degraded efficiency, and one proposed solution. Heat is the real degrader of solar panels and this promises to extend the life of the panel and also harvest what you can of the heat. My installation may take advantage of this, and I can store the heat in heat mass storage in the basement/crawlspace.
I can also make an exchanger and push the excess back into my geothermal ground loops, and get some return benefit at the shoulder of the heating season. My brother's geothermal system does that.
https://youtu.be/Ow0BHlSZg5M
 
^^^ I watched the video.

There are a few more YouTube videos on the same idea of heating the air passing under the PV panels.

In cold climates, it makes sense to make the most of the sun energy hitting your roof. But when it is even colder and with a lot of snow, it will be difficult to have the system sealed against water intrusion.

It's not cold where I am to bother with collecting additional energy from the panels in the form of extra heat. The complexity and additional maintenance is not worth it.

Regarding the heat causing reduced PV efficiencies, I see this too well with my system. Its production is best in early summer, when the sun is high enough for a good angle and the day is sufficiently long but the ambient air is not too hot. In August when the air is 120F in midday, I have clocked the surface of the panels at 170F! I don't know yet about the shortened life of the panels under this extreme heat.

Panels on the roof are usually mounted with a few inches of clearance to provide ventilation for cooling. I wonder how hot Tesla solar tiles get, as they are flush-mounted to the roof sheathing and there's no air circulation underneath.
 
I figure on collecting the heat when it makes sense, and actively cooling the backs of the panels when it does not. The increase in efficiency will pay for itself.
 
I just went out to measure the temperature of my panels. Ambient air: 97F (36C). Top surface of panel: 147F (64C). Bottom surface of panel: 157F (69C).

That the bottom surface (facing down) is hotter than the top surface facing the sun was quite unexpected. But thinking about it, I guess it makes sense. The top of the panel is the glass over the PV cells. It is the PV cells that absorb the solar heat. The heat is more readily transmitted through the thin silicon cells down to the white vinyl backing than back up through the thicker glass.

To cool the backside of the panels, people have tried attaching a heatsink with an embedded water loop. This adds quite a bit of cost.

How about just forced air cooling? Here's a researcher who tried that at a university in Cartagena, Spain. He was able to cool the panel down 15C (59F), and increased the power generation by 3-5%. Of course, we have to deduct out the power to run the fan.

See photo below.

For the full article: https://www.hindawi.com/journals/ijp/2013/830968/

So, if you can use the collected heat, it's great. Else, just to improve the panel efficiency, it's not worth it. Longer life of the panels due to lower temperatures is a separate factor.


1-s2.0-S2214157X19305416-gr5.jpg
 
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Yeah, sue the energy companies...

Add the car companies too, like we all didn't buy cars to drive around in?

And gee, my house gets cold in the winter...

Yeah sue 'em all!

But we have seen the enemy and it is us.
 
NW-Bound said:
....

How about just forced air cooling? Here's a researcher who tried that at a university in Cartagena, Spain. He was able to cool the panel down 15C (59F), and increased the power generation by 3-5%. Of course, we have to deduct out the power to run the fan.
...
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A little off-topic, but...

NW-Bound, you are among the last people on Earth I would have expected to make the above mistake!

OK, this is a bit of an assumption on my part, but given the context (Spain), and the problem, I'll assume that cooling the panel down 15C was a relative reduction (since AFAIK there isn't much degradation of solar panels @ 15C). So probably more like a reduction from 65C to 50C, in that range? In that case, a 15C reduction (delta) is a delta of (149-122=27) 27F.

Just having some fun here, I know we don't proofread every post to such a degree (oooo - no pun intended, I only caught that as I re-read my own post). But it just stuck with me, as I saw that same error in a publication today, and I recall seeing it in our family's World Book Encyclopedia when I must have been in 8th grade, they reported a 1 degree C delta as 33.8 degrees F, and I knew something was not right.

Interesting thread, and I appreciate your contributions!

-ERD50
 
RobbieB said:
Yeah, sue the energy companies...

Add the car companies too, like we all didn't buy cars to drive around in?

And gee, my house gets cold in the winter...

Yeah sue 'em all!

But we have seen the enemy and it is us.
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But, but, but instead of giving us 4-banger cars, they tempted us with big-bored V8s. Now, there's not enough gasoline.

And instead of building a smaller home with extra insulation, they use the money to make the house a mini mansion, which is costly to cool in the summer and to warm in the winter. Now, there's not enough electricity.

And they build showers with so many spraying heads, it's like Niagara Falls when you take a shower. Water's squirting every which way. Now, there's not enough water.

These greedy bastards will just have to pay. That will teach them. Look how the car makers claim to be green with EVs, but trip over each other to promote cars that do 0-60 mph in milliseconds or something like that. And these EVs suck up as much as 350 kW to supercharge. Good grief!

Do they ever learn? Sue them all, I say.
 
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Yup, better call Saul.

I've got the solar on the roof, car gets 24 mpg and house is 1400 sq-ft.

But I did buy a boat with twin diesels that gets less than 2 mpg. Last time I looked it still had 400 gallons in the tanks. But, I'll pay at the pump in a few months.

Welcome to the dark side - :)
 
And you have not sued the boat maker? Better go find a good lawyer. Sue everyone's pants off.
 
Yeah! Wouldn't 1 engine be enough? With a bow thruster? Idiots.
 
My plan is to build the array with an air channel behind each row of panels, and use a small computer to control the air dampers. If my heat storage mass does not need the heat, then dump it out.
 
NW-Bound said:
Here's a photo of a section of the Bhadla Solar Park in India. Its peak production is 2245 MW, in the same caliber as the Hoover Dam output. It is spread out over 17 square miles!

bhada-1.jpg
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Well, Lake Mead is pretty big too... :)
Yeah, it does provide energy storage, but Hoover Dam isn't a run of river hydro generation station either. ;)
 
ERD50 said:
A little off-topic, but...

NW-Bound, you are among the last people on Earth I would have expected to make the above mistake!

OK, this is a bit of an assumption on my part, but given the context (Spain), and the problem, I'll assume that cooling the panel down 15C was a relative reduction (since AFAIK there isn't much degradation of solar panels @ 15C). So probably more like a reduction from 65C to 50C, in that range? In that case, a 15C reduction (delta) is a delta of (149-122=27) 27F.

Just having some fun here, I know we don't proofread every post to such a degree (oooo - no pun intended, I only caught that as I re-read my own post). But it just stuck with me, as I saw that same error in a publication today, and I recall seeing it in our family's World Book Encyclopedia when I must have been in 8th grade, they reported a 1 degree C delta as 33.8 degrees F, and I knew something was not right.

Interesting thread, and I appreciate your contributions!

-ERD50
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Yes, I made a mistake. The 15C temperature drop is the delta (27F or 15*1.8), due to the forced air cooling. The panel temperature was not at 15C or 59F.

And in my earlier post about my own panels, I wrote that today my panels were at 157F, while the ambient air was 97F. In the ultimate case, the forced air cooling would cool the panel down to the ambient, which means a delta of 60F. The Spanish experiment shows a temperature delta of 15C or 27F, which is quite reasonable.

And by the way, to the 1st approximation, cooling the panel down 60F will bring the same efficiency improvement, whether you are cooling it from 160F to 100F, or from 100F down to 40F.

Yes, solar panels work best in the cold winter air. However, the problem in the winter is that you usually don't have the same sunlight intensity as you do in the summer. And of course the day is also shorter in the winter.

And here's another thing most people do not know. The voltage output of a PV panel rises as the temperature is lowered. Failure to allow for this will cause equipment damage.

Say, you wire 3 panels rated at 50V in series to a charge controller that allows a maximum voltage of 150V. It's all well until a cold morning when the panels put out 55V each, and the voltage of the string reaches 165V and exceeds the limit of the charge controller.
 
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From the conclusions in the article you posted above.
For the same aspect ratio and under the same high irradiance conditions, the electrical power of a panel cooled by forced convection is higher than that obtained by natural convection. Improvements up to 15% in electrical power and decrease of panel temperature of about 15°C have been reported.
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15% is significant and I think it can pay for its own cooling.
 
skyking1 said:
From the conclusions in the article you posted above.

15% is significant and I think it can pay for its own cooling.
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Hmmm... The 15% higher power is what the author said somebody else has claimed. But his own experiment yielded less.


For a given value of the aspect ratio, the electrical power of a PV panel cooled by forced convection is 3–5% higher than by natural convection and it increases, as expected, when the forced velocity inside the air duct is higher. The electrical improvement is due to the decrease of PV panel temperature, being of  10–16°C.
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I think whoever reported the 15% improvement got it because his baseline was so poor. Say, if your baseline panel is flush-mounted on a roof with no ventilation to trap a lot of heat, then forced air cooling will help a bunch. But if your baseline panel has some decent natural convection cooling, then you will get a smaller improvement.
 
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NW-Bound said:
........

Yes, solar panels work best in the cold winter air. However, the problem in the winter is that you usually don't have the same sunlight intensity as you do in the summer. And of course the day is also shorter in the winter.

And here's another thing most people do not know. The voltage output of a PV panel rises as the temperature is lowered. Failure to allow for this will cause equipment damage.

Say, you wire 3 panels rated at 50V in series to a charge controller that allows a maximum voltage of 150V. It's all well until a cold morning when the panels put out 55V each, and the voltage of the string reaches 165V and exceeds the limit of the charge controller.
Click to expand...


I have seen that at my camp running on solar panels. Summer time the panels' output is around 150-170 volt into MPPT charger. I have a 220v baseboard electric heater wired with switch, off in summer, to the output of the solar panels to so when voltage goes up, the the heater absobrs some of it. For next winter I will add one more heater. It gives the cabin some heat. Still the overvoltage protection will disconnect the solar charger on a very cold bright sunny day.
 
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NW-Bound said:
.... And by the way, to the 1st approximation, cooling the panel down 60F will bring the same efficiency improvement, whether you are cooling it from 160F to 100F, or from 100F down to 40F. ...
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Interesting, I was not aware of that, I visualized a very non-linear curve with temperature.

-ERD50
 
NW-Bound said:
But, but, but instead of giving us 4-banger cars, they tempted us with big-bored V8s. Now, there's not enough gasoline.
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I know you were somewhat tongue in cheek, but realistically, whether we burn through our fossil fuels in 200 years or 250 years (or whatever) the result will be virtually the same in two respects 1) Readily available FFs will be all but gone and 2) global warming will be virtually the same - just sooner or later by a few years. Thus my suggestion that we learn to deal with the effects of global warming before they all become manifest. Not an expert, so I could be wrong. I was once, so YMMV.
 
Koolau said:
I know you were somewhat tongue in cheek, but realistically, whether we burn through our fossil fuels in 200 years or 250 years (or whatever) the result will be virtually the same in two respects 1) Readily available FFs will be all but gone and 2) global warming will be virtually the same - just sooner or later by a few years. Thus my suggestion that we learn to deal with the effects of global warming before they all become manifest. Not an expert, so I could be wrong. I was once, so YMMV.
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+1

Some warming is coming despite even the best efforts, whether we like it or not. In my area we may get more precipitation but due to warming there will be more rain and less snow. Alas, the snow pack is a big part of our reservoir system.

Some are starting to point out that we should be planning on building more reservoirs and finding ways to recharge the underground aquifers because in 50 years we won't be able to depend on a big snow pack melting slowly in the Spring and Summer to supply us with a constant supply of water. Alas, our political leaders can't or won't think that far ahead.
 
mpeirce said:
Deserts aren’t wastelands really.

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Yes, I apologize for calling the Mojave Desert useless sand. I'm thinking about a carbon sink benefit. In Illinois, we have vast corn/bean farming. If farmed correctly, this land could be a carbon sink. Forests, rain forests, and prairies are carbon sinks. Desserts, not so much but the dessert has a huge range of plants and animals.

This brings up a question. Do solar panels on land and soil prevent natural growth and block carbon sink benefits? If solar panels were placed in the dessert would they negatively effect life on the dessert?
 
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