Delta Electronics and Spectrolab (the creators of the record 40.7% efficient concentrator solar cell) have teamed up and developed an assembly for the concentrator solar cells that will deliver an overall cell efficiency of 35%!
The concentrator-type solar cells require that the incoming light be focused on a smaller surface area. The actual solar cell receiving this concentrated light operates at an elevated temperature, and so the assembly that contains the solar cell and concentrating device (lenses, mirrors, whatever that may be) must be able to withstand these higher operating temperatures over time. With this announcement, Delta Electronics is basically saying that they have developed such an assembly, and now Spectrolab will evaluate it to make sure it meets the International Electrotechnical Commission standards, before moving into production.
35% efficiency is more than double the efficiency of current solar panels that we can buy off the shelf, and the concentrator design requires less light-converting materials for the same amount of area. Eventually, this assembly should drive the cost of solar cells per watt down even further. I can't wait!
You can read the full story here.
Friday, March 9, 2007
Thursday, March 8, 2007
Solar Cell Efficiencies Continue to Rise
Solar cells seem to have a bad reputation for operating at very low efficiencies. It's true that a standard silicon solar cell will convert somewhere around 16% of the visible light that hits its surface to electricity. This number is much higher than the efficiencies of solar cells of only a few years ago, however, and the trend of increasing solar cell efficiency is well-established and expected to continue.
The current record efficiency for a solar cell is 40.7% (see story here)! That number is almost unbelievable. These cells are multi-junction concentrator cells, and they may be a year or two from large-scale production, but the performance of all types of solar cells has been steadily increasing.
The potential for solar cells to increase in efficiency differentiates solar from other electricity generation methods. No other industry has such great potential for improvement. I may be mistaken, but I do not see similar trends in efficiency in coal, nuclear, natural gas, or other fossil-fuel based methods for creating electricity.
And because of the simplicity of the entire solar electricity generation process, an increase in conversion efficiency has a direct impact on the overall efficiency of the generation system. The two most significant effects are:
The importance of the second effect cannot be overstated. The limited supply of silicon available for solar cell production has kept prices high over the past few years. New silicon production capacity is being added, and the supply bottleneck will begin to open up over the next two to three years, but being able to get the same amount of power out of less raw material may drive the price of solar power down more quickly than any other development in the field.
To wrap it all up, here's a chart that should give all of us hope. It shows the efficiencies of a wide range of solar cells achieved in laboratory conditions over the last 30 years. Some types of cells have done better than others, and these lab-grade examples perform better than what we can get off the shelf for the next few years, but the trends and implications are clear.
This image comes from the National Renewable Energy Laboratory at http://www.nrel.gov/
Makes me feel all warm and fuzzy inside, you know?
The current record efficiency for a solar cell is 40.7% (see story here)! That number is almost unbelievable. These cells are multi-junction concentrator cells, and they may be a year or two from large-scale production, but the performance of all types of solar cells has been steadily increasing.
The potential for solar cells to increase in efficiency differentiates solar from other electricity generation methods. No other industry has such great potential for improvement. I may be mistaken, but I do not see similar trends in efficiency in coal, nuclear, natural gas, or other fossil-fuel based methods for creating electricity.
And because of the simplicity of the entire solar electricity generation process, an increase in conversion efficiency has a direct impact on the overall efficiency of the generation system. The two most significant effects are:
- A doubling of solar cell efficiency means that only 1/2 as much solar cell area is required to generate the same amount of electricity.
- A doubling of solar cell efficiency also means that only 1/2 as much silicon (or other light-converting material) is required.
The importance of the second effect cannot be overstated. The limited supply of silicon available for solar cell production has kept prices high over the past few years. New silicon production capacity is being added, and the supply bottleneck will begin to open up over the next two to three years, but being able to get the same amount of power out of less raw material may drive the price of solar power down more quickly than any other development in the field.
To wrap it all up, here's a chart that should give all of us hope. It shows the efficiencies of a wide range of solar cells achieved in laboratory conditions over the last 30 years. Some types of cells have done better than others, and these lab-grade examples perform better than what we can get off the shelf for the next few years, but the trends and implications are clear.
This image comes from the National Renewable Energy Laboratory at http://www.nrel.gov/Makes me feel all warm and fuzzy inside, you know?
Tuesday, March 6, 2007
Is There Enough Room For All Those Solar Panels?
One criticism of solar cells is that they supposedly cannot generate a large enough amount of electricity in a small area--sort of an energy density problem.
Now, I'm a huge fan of solar cells, and I think they are basically going to save the world. But lately I've been thinking--What if we would have to cover a ridiculously large area with solar panels to generate all of the electricity we need?
To get a better handle on the size required, I decided to try and run a few numbers. The question: How much area covered by solar panels does it take to generate the same amount of electricity produced by a typical coal fired power plant?
I would estimate that a typical coal power plant, including the cooling towers, piles of coal, and whatever else, would take up between 2,000 and 3,000 acres. This page from Progress Energy describes a new nuclear plant that will have a 3,000 acre footprint for the entire complex, and a coal plant should take up a comparable amount of space.
I also have made some assumptions about the space required for solar cells, the amount of insolation at a typical site, and the efficiency of the installed solar cells. The basic assumptions are then:
3000 acres * 4,047 m^2 / acre = 12,141,000 m^2
50% * 12,141,000 m^2 = 6,070,500 m^2 of area effectively covered by solar panels
6 kWh / m^2 / day * 6,070,500 m^2 = 36,423000 kWh / day of insolation on our solar panels
36,423,000 kWh / day * 16% = 5,827,680 kWh = 5,828 MWh of electricity produced each day
Whereas the power plant, operating 90% of the time at peak capacity, would produce:
1,000 MW * 90% * 24 / day = 21,600 MWh of electricity each day
And for comparison:
21,600 MWh / 5,828 MWh = 3.7
Hmm. At first glance that may not seem very encouraging. It would take 3.7 times as much area to produce the same amount of electricity from solar panels as from a coal fired plant. But there are a few more things to consider.
First, we're not taking into account all of the space required for mining the coal, storing the coal off site before transportation, transporting the coal to the plant, and dumping any waste left over from the plant's operation. I realize that silicon must also be mined and processed to produce solar cells, but that process takes place on a much, much smaller scale (perhaps we should look at those numbers in a future posting).
The 3.7 number is just a very rough estimate, and it can be brought closer to or even below 1 by adjusting the area required for the actual entire operation of a coal fired plant. Basically, though, if you wanted to offset the roughly 20,000 billion kWh of electricity that the world produces each year, you would need to cover:
20,000 billion kWh / ( 16% * 6 kWh / m^2 / day * 365 ) = 22,000 square miles
with solar panels. Whew! That's a lot, but consider this:
I apologize for the length of this post, but I got wrapped up in the calculations. At the end of it all, though, it seems clear that world is not going to run out of room before we are able to convert completely to solar power. The numbers I have used are very conservative, and solar cell efficiencies are constantly improving, shifting the balance more and more in solar's favor.
To see just how much solar cell efficiencies are improving, read my next post.
Now, I'm a huge fan of solar cells, and I think they are basically going to save the world. But lately I've been thinking--What if we would have to cover a ridiculously large area with solar panels to generate all of the electricity we need?
To get a better handle on the size required, I decided to try and run a few numbers. The question: How much area covered by solar panels does it take to generate the same amount of electricity produced by a typical coal fired power plant?
I would estimate that a typical coal power plant, including the cooling towers, piles of coal, and whatever else, would take up between 2,000 and 3,000 acres. This page from Progress Energy describes a new nuclear plant that will have a 3,000 acre footprint for the entire complex, and a coal plant should take up a comparable amount of space.
I also have made some assumptions about the space required for solar cells, the amount of insolation at a typical site, and the efficiency of the installed solar cells. The basic assumptions are then:
- 300 acres required for typical coal fired power plant
- 1,000 MW of capacity for a typical coal fired power plant
- 6 kWh / m^2 / day of insolation
- 16% solar cell efficiency
- 50% of area effectively covered by solar panels (they will need some empty space around them so that they could be directed toward the sun throughout the day, but this number is probably very high)
3000 acres * 4,047 m^2 / acre = 12,141,000 m^2
50% * 12,141,000 m^2 = 6,070,500 m^2 of area effectively covered by solar panels
6 kWh / m^2 / day * 6,070,500 m^2 = 36,423000 kWh / day of insolation on our solar panels
36,423,000 kWh / day * 16% = 5,827,680 kWh = 5,828 MWh of electricity produced each day
Whereas the power plant, operating 90% of the time at peak capacity, would produce:
1,000 MW * 90% * 24 / day = 21,600 MWh of electricity each day
And for comparison:
21,600 MWh / 5,828 MWh = 3.7
Hmm. At first glance that may not seem very encouraging. It would take 3.7 times as much area to produce the same amount of electricity from solar panels as from a coal fired plant. But there are a few more things to consider.
First, we're not taking into account all of the space required for mining the coal, storing the coal off site before transportation, transporting the coal to the plant, and dumping any waste left over from the plant's operation. I realize that silicon must also be mined and processed to produce solar cells, but that process takes place on a much, much smaller scale (perhaps we should look at those numbers in a future posting).
The 3.7 number is just a very rough estimate, and it can be brought closer to or even below 1 by adjusting the area required for the actual entire operation of a coal fired plant. Basically, though, if you wanted to offset the roughly 20,000 billion kWh of electricity that the world produces each year, you would need to cover:
20,000 billion kWh / ( 16% * 6 kWh / m^2 / day * 365 ) = 22,000 square miles
with solar panels. Whew! That's a lot, but consider this:
- The US alone has about 350,000 square miles of paved roads (10% of the 3.5 million square miles of US land)
- As much as 75,000,000 detached homes * 2000 square feet of roof / detached home = 5400 square miles of detached rooftops in the US!
I apologize for the length of this post, but I got wrapped up in the calculations. At the end of it all, though, it seems clear that world is not going to run out of room before we are able to convert completely to solar power. The numbers I have used are very conservative, and solar cell efficiencies are constantly improving, shifting the balance more and more in solar's favor.
To see just how much solar cell efficiencies are improving, read my next post.
The Beginning
A few words about why I've started this blog, and what I expect it to become.
The motivation for writing this blog is mostly selfish. I've become more and more interested in new developments in energy, and how new technologies and policies may help us avoid destroying our planet. The problem is, I often forget where I have read something, or what exactly an article said, so I need an easy way to organize all of the information my small, lazy brain can't seem to remember.
Second, I really don't want to see more drought, more extreme storms, more famine, etc. in our near future because we fail to use what's available to us to keep these things from happening. So, I have a selfish desire to try and get information out about the things I think will change our lives, so that maybe they will have a better chance of actually working.
Lastly, things like solar cells, ultracapacitors, and electric cars are just cool, and I believe that these are just a few of the things that will totally change our planet, and our lives, over the next few years.
The motivation for writing this blog is mostly selfish. I've become more and more interested in new developments in energy, and how new technologies and policies may help us avoid destroying our planet. The problem is, I often forget where I have read something, or what exactly an article said, so I need an easy way to organize all of the information my small, lazy brain can't seem to remember.
Second, I really don't want to see more drought, more extreme storms, more famine, etc. in our near future because we fail to use what's available to us to keep these things from happening. So, I have a selfish desire to try and get information out about the things I think will change our lives, so that maybe they will have a better chance of actually working.
Lastly, things like solar cells, ultracapacitors, and electric cars are just cool, and I believe that these are just a few of the things that will totally change our planet, and our lives, over the next few years.
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