Low Cost, High Efficiency Tandem Silicon Solar Cells

Wladek Walukiewicz, Joel Ager, and Kin Man Yu of Berkeley Lab have developed high-efficiency solar cells that leverage the well-established design and manufacturing technology of silicon cells while delivering the performance previously achievable only by far more complex and expensive tandem solar cells.

Solar vs Coal, Land Area Comparison.

Thirty-eight years of Kentucky strip mining have, at one time or another, destroyed 1.5 Million Acres (6,070,284,633 m2) of land, and torn down 470 Mountains.

Let's roughly compare the land impact of Coal to the potential land impact of Solar, with this 1.5 Million Acres as a basis.


First, let's see how much Energy could be produced by all the Coal that was mined in Kentucky in 2007*. Answer: 553 Billion kWh.


Per Salon, 158 Million Tons of Coal were produced in Kentucky 2007. I know from previous calculations that a very efficient coal plant can produce around 3.5 MWh/Ton, so burning the entire 158 Million Tons of coal produced in Kentucky in 2007 gives, 158 Million Tons * 3.5 MWh/Ton = 553 Million MWh, or 553 Billion kWh.


Now lets look at how much Solar Energy is available to an equivalent area of Kentucky. Answer: 10,000 Billion kWh.


Take a look at the US Insolation Map and note that the State of Kentucky is almost entirely bright yellow. Look at the legend, and note the value of 4.5-5.0 kWh/m2/day for this color. This is the Average amount of Solar Energy striking a 1 m2 panel on some single Day of the year (Averaged over the whole Year). Let's take the low estimate, and get the total Solar Energy incoming onto a 1 m2 panel, over an entire year, by multiplying 4.5 kWh/m²/day * 365 days = 1642.5 kWh/m²**. Multiplying this by 6.07 * 10⁹ m² gives us the total Solar Energy Striking the mined area of Kentucky in 2007, or 10 * 10¹² kWh, or 10,000 Billion kWh.


So, how much of this Energy could actually be converted to Electricity using modern Solar Panels? Answer: 1,600 Billion kWh.


Of course, Photovoltaic Panels don't convert all of the Energy Striking them into Electricity. At this time, it would be fair to use 16% as a rough Average Conversion Efficiency***. So, if you were to cover that 1.5 Million Acres with Solar Panels, and each panel was 16% efficient at converting that light to Energy, that installation would produce 10,000 Billion kWh * .16 = 1,600 Billion kWh of electricity.


The Conclusion?


If you covered the 1.5 Million Acre area of Kentucky that has been affected by Strip Mining and Mountaintop Removal with Solar Panels like those commonly manufactured today, then you would produce 2.9 times the energy every year from that Installation than you would from mining the coal. In addition, unlike in coal mining, where once you've mined out an area, you have to move on to another, in the case of Solar, the Installation would produce Energy Year after Year from the same pieces of land. If you just wanted to produce the same amount of Energy as the 2007 Coal Production, you would only have to set up solar panels on 517 Thousand Acres of land. Of course, the Installation doesn't have to be all in one place, the Panels could be distributed among small Installations all across the State (2% of the total land area of Kentucky).

Note that this post does not attempt to address price. Those calculations are elsewhere, and ongoing. However, just in terms of land use, it becomes clear that the energy content of Coal could, in fact, be replaced by an Installation of Solar, while distrupting a Third of the land area of ongoing Coal Mining Operations.

Also note that this does not address the availability of Solar Panels. This will be addressed incrementally by a growing industry.



* Depends on numerous factors, including Coal Chemistry, and Power Plant Design. The values that I used assume very high Energy Content Coal, and highly efficient, state of the art, Power Plants.

** Note that this isn't quite correct, as the Insolation values on the map are not based on a panel laying flat on the ground, but are based on a panel tilted to the South. Within the scope of these calculations, though, this should be negligible.

*** Expect Conversion Efficiencies of low cost Crystalline Silicon Solar Panels to increase significantly within the next 3 years.

Conversions:
1.5 Million Acres = 6,070,284,633 m2
Kentucky total area = 104 658 829 550 m2 = 40409 mile2

For more information on "Insolation," see "A Note on Units of Energy and Insolation".

This article is followed by http://americansolareconomy.blogspot.com/2009/02/real-world-estimation-of-land-use-per.html, which estimates the Solar Output of 1.5 Million Acres of Kentucky Land, using real Land Use data from Sunpower Corporation.

Note on CEC Ratings for Modules.

Here's a list of CEC ratings from California.

Here's a description of "derating" of Energy Output. In other words, the panels aren't perfect, here's how to estimate actual output to AC from DC.

Bolivia nationalises BP Natural Gas Field.

News from the BBC.

Not good news for Fossils. International Companies will face increased risk of such events when they invest in production capacity in Developing Nations.

PDF on Carbon Sequestration

Carnegie Mellon

An Idea to take up-front cash on long term debt via Solar.

Based on Amendments to the Bailout Bill that Passed in November, there's a 30% Tax Credit for Solar Energy Installation Costs.

Let's see. If you borrow the cost of a Solar Project to be payed back over some number of years, you'll get 30% back all at once around tax-time (if you payed out the equivalent in taxes that year). If you don't owe on taxes, there's still the possibility that the 30% credit will become fully refundable under the upcoming stimulus package.

Do you think that some folks wouldn't like 30% upfront on a long-term loan, particularly on a loan for a product that will pay itself off in the long term?* These guys need all the upfront money they can get, and you can bet that this 30% will look appealing to many. It's like a money machine. Watch Solar Equipment Demand take off over the course of this year.

*Depending on circumstances.

CNBC is a total joke.

Kudlow is an elitist ass, for one thing.

Cramer and many others have been pushing the "bad bank" idea very hard today, which immediately makes me think that it's probably a very bad idea as far as public policy is concerned.

Fast money is entertaining, and I'd say is the best of the bunch, at least there's some free debate.

In any case, for real business news, got to Bloomberg.

What a Market this could be.

Forget Large-scale Energy Production for a moment. Turn your eyes from the rooftops, fields, and deserts where you could put PV or Concentrating Solar. For a moment, look around your house and think of all of the possibilities for very Small-scale Solar.

Somebody at Yahoo joked about giving someone a Solar Powered Flashlight, as if, I suppose, you waited until you needed it before you decided to try and charge it up. Thinking about it, though, who wouldn't want a solar powered flashlight for an emergency (with LED lighting). I have a flashlight sitting at my desk, and for the few hours of actual emergency light it's provided, I've changed the batteries numerous times (my Son likes to play with it). Rather than going hit and miss with a flashlight that may or may not have charge in its batteries for an emergency, why not have a flashlight that is constantly charging, as long as light is present?

Another example that's come up is based on the smoke detector that is currently sitting on my kitchen counter. The Smoke Detector is dependent on the tiniest flow of charge to trigger the alarm, and yet, they come with batteries that just might not be there when you need them. The smallest solar chip or thin-film coating could keep a very small battery charged up for a very very long time.

The list goes on. Remote Controls, MP3 Players, Cell Phones, Game Controllers, ... remote devices in general. Sure, depending on your amount of time talking on the phone, or listening to music, you might need a way to plug in the device to give the batteries a boost, but it seems to me that if you could bake a durable thin film onto the surface, you'd be set for rather a much longer time between charges, at the very least.


BTW: Googling "solar flashlight" does turn up solar flashlights. On the other hand, I just did a bunch of calculations, and I have a hard time believing that the quality of these things, based on today's common batteries, solar collectors, and manufacturing scale, is terribly high. It will take some time, and some good combinations of technological advancement before quality solar remote items become commonplace.

General Comment - 1/19/2009

I haven't been posting much here, though I've still been reading a heck of alot of news, and doing alot of thinking. Other things have been busy, though, and putting words together takes alot of time. As usual, I've been throwing stuff at the Yahoo Board, but those are typically just snippets, and not at a state of preparedness that I'd typically put here.

I'll try to manage a few posts tonight, in part from recent comments on Yahoo.

On another topic, I did do some updating of code at http://AmericanSolarEconomy.com, have set up RSS Feeds off of my semi-automated news reader / link import system, and have linked them to this blog (see left hand side bar) along with some other relevant blogs. If you know of good RSS Feeds that should be added to this sidebar, let me know!

A Note on Units of Energy and Insolation.

This post is in reference to my use of units like "Watt*1Year," or "Watt*25Years," etc, in posts such as This, This, and This, and might just be useful in laying out some of the basic math behind Solar Energy Output. Feel free to critique.


In Physics, Power is described in Watts. Energy is described by Power * Time. Typically when we think Electrical Energy, we think in terms of Kilowatt*Hours, but the actual units used for Time are arbitrary, it's just a matter of the increment of time over which you are considering the flow of Power.

The Quantity of Energy streaming down on the planet can be measured in terms of its Insolation. The problem that I'm seeing out there is that it's not firmly decided what units we should be using for Solar Insolation, and there is little way to translate at a glance quantities from one choice of Unit to the next. Now, maybe there's a reason that somebody would want to use "kW·h/(m²·day)" or "kWh/kWp•y" for practical applications to Solar Energy, but the rationale certainly escapes me. What I do know is that a Solar Module is rated in Watts Peak (W_p), which is the Power Generated when the Panel is exposed to an Insolation of 1000W/m². So, to match this, I want my units to be comparable to W/m².

Following is a map of US Annual Insolation in kW/m²*.



By taking the given values in terms of kWh/m²/day, converting from KiloWatts to Watts, and multiplying each by 1day/24h to cancel out the elements of time, we get the Annual Average Power, in W/m². Once we know this Annual Average Power, then by dividing it by the 1000W/m² rated Peak Power used by the Photovoltaic Industry, we get a very useful percentage.

Example: Looking at the map, let's take a spot on one of the bright yellow areas, like is found in most of Virginia. The legend shows an Insolation Value of 4.5-5kWh/m²/day. Converting to Watts, and taking the range's lowest value of 4500Wh/m²/day, multiplying by 1day/24h, and canceling out the hours and days, gives 187.5W/m².

So, now that we have the average Rated Insolation for the location, then we divide this number by 1000W/m² in order to get the Actual Insolation as a percentage of Rated Peak Insolation, in this case, for Virginia, at 18.75%.

I've run this calculation for the various brackets in the map legend, and have added these percentages to the graphic. The spreadsheet is here.

Lets say that you want to know roughly how much actual Energy some Solar Installation will produce over a year. You just take the Peak Power rating of the Installation, and multiply by the Percentage that was calculated above, and then multiply by 1Year in order to get the Energy produced on average over that Year.

Example: You want to know how much Energy is going to be produced over the year by a 5kW_p Installation in Virginia where the expected average Insolation is 18.75% as calculated, above. Simply take the Peak Rated Power of the Installation, and multiply by the Percentage and 1Year, in this case, 5kW*18.75%*1Year = 937W*1Year.

This is the Average Energy Produced over a Year for this Installation, even though it's not in the usual units. To convert to kWh, just convert the Year to Hours using the factor of 8760Hours/Year and 1kW/1000W to get 8208kWh.


Now let's say that you want to make a comparison in Cost per Watt between a Solar Installation and a Coal Plant, or a Natural Gas Turbine, or any other conventional Electrical Generator running at a Constant Output over the year. Just remember that the total Energy Produced by a constant generator over a year, in W*1Year (or kW*1Year, or GW*1Year), is roughly it's Rated Output * 1Year, so a 100MW Coal Plant should produce in the area of 100MW*1Year in Energy over the year. We could convert this to kWh just like was done above for the Solar Installation, but there's no need to do so if we're just using it for comparisons-sake.


* This map measures Insolation assuming optimally angled panels, so for flat-roof installations, particularly at higher Latitudes, will over-estimate output. For a European Map and Insolation Values that assume flat placement of Panels, see Lightbucket.

A little bit of Light Activism...

Dear Lowes Representative,

Please pass this email up the line.

I'm a long-time Customer of Lowes. I notice, however, that you have no items under the keywords "Solar Inverter," no items under "Solar Module," and only four items under "Solar Panel."

I completely understand your not stocking these items in all of your stores, but online availability only makes sense, considering the potential future growth in this market*.

I also notice that you have no books on Solar, or Energy Efficiency in your bookshelves. This kind of information will be in increasing demand in the near-term, and should be available ASAP!

Thanks,
D P


* As of 1/1/09, a 30% investment tax credit with no cap has gone into effect for purchases of Solar Systems, and by the end of January, the Federal Government will have passed a bill with particular stimulus of the Solar Industry in mind.

Lowes stands to benefit by these programs, and likewise, Lowes Customers across the country will benefit by access to Solar Equipment from a trusted and convenient Vendor.

Neat Trick with a Prius - Backup Residential Power.

A Prius can power your home.

Great News from Congress, Markey to take Energy and Air Quality Subcommittee Chairmanship.

Rep Markey possible to take Energy and Air Quality Subcommittee Chairmanship...

This is great news! Boucher is from Virginia, which is a Coal State. He'll have over the Telecommunications and the Internet Subcommittee, while Markey from MA will be very influencial in Climate Change / Energy Policy.

I've seen Markey talk about Energy, and he's a Solar Warrior. This is good.

Happy New Year part 1. Tax Credits are Effective Today!

Here's a short article on the Credits.

Here's a good article on Inverters by the same author

I'm starting to think that a good way for to go for a self-starter, or one with limited funds upfront, would be to buy an Inverter, and a minimal number of Panels ASAP. This would make the home Solar-Ready, with the inverter reflecting the greatest single-item cost, and would allow for expansion in production over time.

I'm going to go to the Bank soon, and start looking into financing. They WANT to lend money, but they want to lend money safely. What's a safer bet these days than lending money on a system with a potential immediate payback of 30% in Tax Credits, which not only adds real value to the home, and provides for immediate and long term payback in in the form of free electricity.