Photons come in a range, one would even say a spectrum, of energy levels. And yes, the higher energy photons have — more energy! But since one photon can only knock out one electron in a solar cell, no matter how much energy the photon has, it can only knock out that one electron. If only there was a way to harvest the additional energy that comes from those higher energy photons!

There is now possibly a way to free up more than one electron, by increasing the external quantum efficiency of the cell to go over 100%. The technique was discovered and reported in 2013, and since then has remained one of those “breakthrough” technologies that we don’t believe in until they happen. Technically, this may not be a true breakthrough level technology, since it would only increase solar cell energy production by single or low double digit percentage. But that is still a good thing.

The same team that reported this in 2013 has now demonstrated on the lab bench that they can do it. The earlier work also produced actual results, but using a form of solar cell that was very inefficient to begin with. So that’s like saying, “I can run faster than you” but only from a mile back from where you start.

From the press release from MIT, you can glean the details:

The key to splitting the energy of one photon into two electrons lies in a class of materials that possess “excited states” called excitons, Baldo says: In these excitonic materials, “these packets of energy propagate around like the electrons in a circuit,” but with quite different properties than electrons. “You can use them to change energy — you can cut them in half, you can combine them.” In this case, they were going through a process called singlet exciton fission, which is how the light’s energy gets split into two separate, independently moving packets of energy. The material first absorbs a photon, forming an exciton that rapidly undergoes fission into two excited states, each with half the energy of the original state.

But the tricky part was then coupling that energy over into the silicon, a material that is not excitonic. This coupling had never been accomplished before.

As an intermediate step, the team tried coupling the energy from the excitonic layer into a material called quantum dots. “They’re still excitonic, but they’re inorganic,” Baldo says. “That worked; it worked like a charm,” he says. By understanding the mechanism taking place in that material, he says, “we had no reason to think that silicon wouldn’t work.”

What that work showed, Van Voorhis says, is that the key to these energy transfers lies in the very surface of the material, not in its bulk. “So it was clear that the surface chemistry on silicon was going to be important. That was what was going to determine what kinds of surface states there were.” That focus on the surface chemistry may have been what allowed this team to succeed where others had not, he suggests.

The key was in a thin intermediate layer. “It turns out this tiny, tiny strip of material at the interface between these two systems [the silicon solar cell and the tetracene layer with its excitonic properties] ended up defining everything. It’s why other researchers couldn’t get this process to work, and why we finally did.” It was Einzinger “who finally cracked that nut,” he says, by using a layer of a material called hafnium oxynitride.

The layer is only a few atoms thick, or just 8 angstroms (ten-billionths of a meter), but it acted as a “nice bridge” for the excited states, Baldo says. That finally made it possible for the single high-energy photons to trigger the release of two electrons inside the silicon cell. That produces a doubling of the amount of energy produced by a given amount of sunlight in the blue and green part of the spectrum. Overall, that could produce an increase in the power produced by the solar cell — from a theoretical maximum of 29.1 percent, up to a maximum of about 35 percent.

Actual silicon cells are not yet at their maximum, and neither is the new material, so more development needs to be done, but the crucial step of coupling the two materials efficiently has now been proven. “We still need to optimize the silicon cells for this process,” Baldo says. For one thing, with the new system those cells can be thinner than current versions. Work also needs to be done on stabilizing the materials for durability. Overall, commercial applications are probably still a few years off, the team says.

Other approaches to improving the efficiency of solar cells tend to involve adding another kind of cell, such as a perovskite layer, over the silicon. Baldo says “they’re building one cell on top of another. Fundamentally, we’re making one cell — we’re kind of turbocharging the silicon cell. We’re adding more current into the silicon, as opposed to making two cells.”

The researchers have measured one special property of hafnium oxynitride that helps it transfer the excitonic energy. “We know that hafnium oxynitride generates additional charge at the interface, which reduces losses by a process called electric field passivation. If we can establish better control over this phenomenon, efficiencies may climb even higher.” Einzinger says. So far, no other material they’ve tested can match its properties.

The paper is in Nature: Sensitization of silicon by singlet exciton fission in tetracene, 2019, by Einzinger et al, (Nature 571, 90-94(2019)

Corporate clean energy buying surged to new record in 2018

Corporations purchased 13.4 gigawatts of clean power through long-term contracts, more than doubling 2017’s total, helped by demand from new industries and previously untrodden markets

Scenery conflict (I’ll just add, that solar panels replacing some nice vistas is better than post-apocalyptic landscapes replacing some nice vistas): Rhode Island town grapples with how to promote solar and protect rural views

Similarly, Massive Wisconsin solar proposal splits farmers and clean energy fans

And … Oregon adopts strict rules for solar panel farms on high-value farm soil

And for those who want to pay more but perhaps have something cool: RGS Energy Revives Dow’s Solar Roof, Claiming Better Efficiency and Lower Costs

Also in Wisconsin, there are hearings underway inconsideration of a 300 MW solar farm covering 2,500 acres. In Wisconsin, summer capacity is 16,967 MW. Wisconsin has 54,314 square miles of land, and 2,500 acres is just under 4 square miles. Wisconsin could meet its summer capacity needs by producing 0.31 MW per square mile. The proposed plant will run at 75 MW per square mile. Wisconsin could produce all of its summer capacity (ignoring time of day and storage issues of course) with about 227 square miles of solar panel, which would be less than a half of a percent of the state’s land area. If my calculations are right.

Let’s say we quadruple our electricity needs mainly because we electrify everything. That means that Wisconsin could probably make all the electricity it needs by covering about 1,000 square miles with solar panels, which would be about half the land area of the physically largest 100 cities in the state. So, go figure that out.

Across large parts of the midwest, the “Midwest Solarize Programs” have helped just under 500 residential homes get a total of 3.8 MW rooftop capacity in 2018.

There is a solar plant under review in Michigan that will rate at 239 MW on 1,245 acres. That’s a much higher rate of production compared to the above cited Wisconsin plant, because the panels will track the sun. (This tells us that the largest 100 Wisconsin cities can get back some of their land if they use this technology).

A recent survey shows that one in nine Americans are considering buying an electric vehicle. That’s not bad, but not good enough. But once the ball gets rolling….

Here’s the elevator speech version: Minnesota residents get around five thousand dollars cash (over several years), monetary incentives to upgrade all their energy using devices from furnaces to cars, some 80,000 new, high paying jobs, and in the end, the state is essentially fossil fuel free.

About half of that fossil fuel free goal comes directly from

the plan itself, the other half from the economy and markets passing various tipping points that this plan will hasten. The time scale for the plan is roughly 10 years, but giving the plan a careful reading I suspect some goals will be reached much more quickly. This means that once the plan takes off, Minnesotans will have an incentive to hold their elected officials accountable for holding the course for at least a decade.

The central theme of the plan is to use a revenue-neutral carbon price, which is widely seen by experts as the best approach for cleaning up our energy supply. The simple version of the carbon price works like this: Releasing carbon is saddled with a cost, way up (or early) in the supply chain. So you don’t pay a gas tax or any kind of energy tax, but somewhere up the line the big players are being charged for producing energy reliant on the release of fossil carbon. They, of course, have the option of producing electricity from wind and solar.

The campaign notes, “Rebecca’s Minnesota-Powered Plan doesn’t raise taxes a single penny. It levies a carbon price on fossil fuel companies, and pays 100% of the revenue back to Minnesota residents, so we can take charge of our own energy.”

That money is then distributed to any citizen who wants it (of course they will all want it), evenly, across the board. So, in theory, your cost of living is a little higher if dirty energy producers are in your own personal supply chain, but lower if they are not, and in any event, you are paid off to not care. The point is, if you personally eschew fossil carbon releasing products or energy sources, you get the payoff and someone else is paying for it. That would apply to both individuals and companies, because companies can often make those choices. For example, a school bus company would be more likely to replace an old dirty bus with an electric bus rather than a propane bus. (Just yesterday, an electric bus set a record, going over 1,000 miles on a single charge! Electricity is some pretty powerful magic.)

The Otto plan has a twist. While 75% of the carbon price is distributed evenly and directly to all citizens, 25% is distributed as refundable tax credits intended to cover 30% of the cost of clean energy improvements that use Minnesota companies. This may include solar panels, heat pumps for heating and cooling, insulation, new lighting, etc. New or used electric cars count. So it all goes back to the people, but some of it is directed to support the energy transition for individuals and families.

(A “refundable credit” is a tax credit that you still get even if you did not pay enough taxes to use it, so people of any income will be able to access the clean energy benefits.)

The conservatively estimated potential cash gain for a typical Minnesota family is laid out in this table from the Otto campaign:

That is for one year. As the plan matures, a decade down the line, we can assume the carbon price component will diminish, but the household payback for being off fossil fuels will increase, and, guess what? The plant gets to live and your children don’t have to live in as much of a dystopian future!

The clean energy technologies that will need to be deployed mostly already exist, and most of them can be processed and supplied right here in Minnesota. Indeed installing PV panels and car chargers, or efficient heat pump based furnaces, etc. is the kind of job that can not be outsourced to some other country, because your house is here so the work gets done here! It is estimated that some 80,000 long term high paying jobs will be generated from this infrastructure redo. That will in turn increase revenues to the state and quite likely, will spell surpluses, some of which are likely to be tax rebates or other sorts of payoffs to the citizens of the state.

A quick word about the Coal-Car Myth. Some will read about this plan and say, “yeah, but … if I drive an electric car and stuff, that electricity is even worser because it is made with dirty coal and stuff.” (Yes, I make the Coal-Car Mythers sound a bit dull because, at this point, you’d have to be a bit dull to still be thinking this). First, know this: There are circumstances under which burning coal to make electricity to charge a car will be more efficient than running a gasoline car. To conceptualize this, imagine two engineering teams in a competition. One is to make an energy plant using coal, the other is to use an energy plant using only 6 cylinder Ford motors. The winner builds the plant that is more efficient. The team using the thousands of internal combustion engines will lose. Second, know this: It is simply not the case that all of our electricity comes from coal, and every week there is less and less of it coming from coal. Electric cars have the promise, by the way, of outlasting internal combustion cars on average. So, over perhaps half the lifespan of a given electric car, what might have been a tiny increase in efficiency for a small number of electric cars (the rest start out way more than tiny) will become a great efficiency. It is time to switch to electric cars in Minnesota.

You can expect opposition to this plan from the likes of the Koch brothers, who are currently spending just shy of a billion dollars a year, that we know of, to keep fossil fuel systems on line and stop the clean energy transition. I asked Rebecca Otto what she expected in terms of push back. She told me, “Investing in clean energy means investing in our communities and taking charge of our own energy, instead of subsidizing big oil. Hence, big oil will be the stumbling block, as this will affect their bottom line over time.”

I asked Rebecca why this is something that needs to be handled by the states, rather than at the national level. She told me, “The crippling dysfunction in Washington is persistent and we need to act now. Oil companies are spending billions of dollars to rig the system against clean energy solutions. We need to break their stranglehold on our democracy and put people, not oil companies back in charge.”

She also noted that “we also have a moral imperative to do something and the federal government has become paralyzed by big oil propaganda and political spending. The states could become laboratories to begin to tackle climate change. And whoever does is going to reap the economic benefits from the job creation. These jobs pay 42% higher than the state’s average wage.”

Economists say the carbon price is the best way to make the energy transition happen. Regular Minnesotans benefit the most, the Minnesota economy benefits, and the environment benefits. This is a good plan. I endorse it.

This plan, which you should read all about here, has also been endorsed by the famous and widely respected meteorologist Paul Douglas, by Bill McKibben of 350.org, St Thomas scientist and energy expert John Abraham, and by climate scientist Michael Mann.

I’ve got more to say about this plan and related topics, so stay tuned.

Here’s a video of Rebecca Otto discussing energy from the roof of her solar paneled home, with her windmill generating electricity in the background. Apparently, she walks the walk!

Another post on the plan:

Powering Minnesota to prosperity through energy leadership
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*You may have seen recent research suggesting that we have more time than previously estimated to get our duck in a row with clean energy. That research was misrepresented in the press. A statement made by one of the authors clarifies: “..to likely meet the Paris goal, emission reductions would need to begin immediately and reach zero in less than 40 years’ time.”

A solar plant is a way of making the use of solar more full time. Instead of just producing electricity by sunlight, perhaps storing some in batteries, it uses sunlight to produce heat, which is then used to run a turbine all day and all night, and across periods of cloudiness (which are rare in the case of this particular plant’s location).

Putting it another way, this kind of plant solves the problem that clean energy tends to be intermittent. Putting it still another way, this kind of plant reduces the need to store electricity that may be overproduced or produced irregularly by photovoltaic solar or wind plants.

But the reporting of this story sadly demonstrates counterproductive lousy anti-clean energy commentary delivered in an envelope of crap reporting (because the reporter did not understand the story enough to ask the right questions). Here is a quote from the story in The Guardian

<blockquoteWasim Saman, professor of sustainable ernergy engineering at the University of South Australia, said solar thermal was a more economical way of storing energy than using batteries.

“The significance of solar thermal generation lies in its ability to provide energy virtually on demand,” he said.

But Dr Matthew Stocks, a research fellow in the research school of engineering at the Australian National University, said solar thermal also had limits.

“One of the big challenges for solar thermal as a storage tool is that it can only store heat. If there is an excess of electricity in the system because the wind is blowing strong, it cannot efficiently use it to store electrical power to shift the energy to times of shortage, unlike batteries and pumped hydro,” he said..

No. Investing in this kind of plant is a move to reduce the problem of storage.

Show me an article about a new nuclear power plant, an upgrade to a coal plant, or a new natural gas plant, that mentions that these technologies are not batteries. This is nothing other than a senseless contrary opinion pulled out of the nether regions of a reporter’s notebook. The search for false balance continues even at the Guardian, which really should know better.

This corresponds to shifts in the amount of electricity produced by these various sources, as indicated in the Department of Energy graph shown above.

The biggest states for this job growth are California followed distantly by Massachusetts, Nevada, New York, New Jersey, Texas, Arizona, Florida, and North Carolina.

Given current trends inside the beltway, I expect the Department of Energy to make this report disappear so 2017 US Energy and Jobs Report_0.

I wrote it up here on 10,000 Birds, where I write a monthly installment on birds and stuff: Solar Plant Stopped Killing Birds: One Weird Trick!

Although Nevada is one of the sunniest places in the world, there has recently been a dark cloud hovering over the rooftop solar industry in the state. Just before Christmas, Nevada’s public utility commission (PUC) gave the state’s only power company, NV Energy, permission to charge higher rates and fees to solar panel users – a move that immediately shattered the rooftop solar industry’s business model.

In addition to the new monthly fee, … customers … will get less back from the utility for energy their solar panels capture and feed into the main power grid. Whereas previously they received full retail value for their surplus electricity, soon NV Energy will only pay a third of that price for exported electricity.

Now, if you live in one of the sunniest states in the US, it is no longer worth it to put solar panels on your roof.

This is part of a national fight over solar energy. In some states, nefarious forces are working toward making it a bad idea to put solar panels on your home or business. In other states, forces for the good are working to make home or business rooftop solar a good idea.

There is a larger scale political divide in this country, with Republicans, Libertarians, and Tea Partiers (overlapping groups) on one side and Democrats and environmentalists on the other. The former is against shifting to clean energy and addressing global climate disruption. The latter is working towards shifting away from fossil fuels and addressing climate disruption.

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Current and recommended books on climate change.
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But a big part of this makes no sense. Those solar panels you may choose, as in individual or small business owner, to put on your roof constitute your way of utilizing your sun. Yes, that sun that falls on your house is not the property of the government, or big corporations, or politicians bought and paid for by big corporations. That is your sunlight, and THE GOVERNMENT SHOULD NOT INTERFERE WITH YOUR USE OF IT TO POWER YOUR OWN HOME.

Public utilities are there to serve the public, and you are part of the public. Those entities, and the state government agencies that regulate them, should not be conspiring to take away your volts. Your Freedom Volts. They should not be stopping you from installing your solar panels … your Patriot Panels … on your own roof.

So why have the Libertarians and their kin not been fighting this? Why have self described “Patriots” not taken up arms, figuratively one would hope, against the nefarious forces that seek to control YOUR access to your OWN ENERGY?

I suspect that eventually they will. Among those who do put up solar panels there must be some who do so to for their own sensible financial reasons. There must be some people who benefit from rooftop solar who are not Democrats or environmentalists, but rather, sensible Republicans or Libertarians who are in it for the FREEDOM, the financial savings, and also, just because it is cool to make your own energy. Perhaps we will see the KINDLING OF FREEDOM among these self sufficient patriots. Perhaps we will see a demand from the right, not just the left, to LEAVE OUR FREEDOM VOLTS ALONE!

When it comes to the transition to clean energy, we can do this the easy way, or we can do this the hard way. The easy way is to encourage the picking of low hanging fruit, such as solar panels on flat spots, at the same time we work towards tackling some of the more expensive projects that require more up front investment but that will eventually pay off. The hard way, of course, is the total collapse of civilization. Most imaginable post apocalyptic worlds don’t use to much fossil fuel!

And, whether the hard way or the easy way is the most likely path at any moment in time is often a matter of what is happening on the state level. Here are a few examples of what is going on right now around the US.

In Maryland, a state commission is calling for the state to pledge slashing greenhouse gas emissions 40% by 2030. That sounds like a large amount, but it is actually a modest and easily attainable goal. They should probably be going for more.

The goal — which if passed into law would be one of the most ambitious set so far by a state — drew unanimous support of the 26-member panel, which includes lawmakers, environmentalists, representatives of business and labor, and top officials in the Hogan administration.

The recommendation is likely to lead to legislation in the General Assembly, which must decide next year whether to stick with the goal it set in 2009 of reducing climate-warming emissions 25 percent by 2020.

Meanwhile, Texas and California are leading the nation in carbon emissions. The overall pattern of carbon emissions by state (using two year old data because for some reason those who keep track of these things haven’t discovered twitter and spreadsheets) is largely a matter of population size and similar factors.

But while we might expect California to be high on the list, Texas is way way higher, to the point one wonders what they are up to down in the Lone Star State.

Data released this week by the administration shows each state’s energy-related carbon dioxide emissions between 1990 and 2013. Texas doesn’t just top the list, its emissions — 641 million metric tons of carbon dioxide — are almost double those of California, the nation’s second largest carbon emitter, which spewed 353 million metric tons of carbon dioxide into the atmosphere.

On a per-capita basis, Wyoming leads all the other states in greenhouse gas pollution.

In New Mexico, Santa Fe has an interesting program in mind. There, The Heath Foundation, a private 501c(3) representing the community interests of Jim Heath, has a plan. Here’s part of it:

HeathSUN will provide a complete rooftop photovoltaic solar system for homeowners in Santa Fe County at no charge to the customer. HeathSUN owns and maintains each rooftop solar system, and the ancillary metering and control equipment, and there’s no lien on the house.

Under HeathSUN’s set-up, customers will continue to have access to electricity from PNM when needed. For solar energy from the rooftop system, the customer pays HeathSUN 80 percent of the going PNM rate, so the solar power’s cost would rise and fall with how much PNM is charging. The customer gets separate bills from HeathSUN and PNM.

In a new twist, HeathSUN says there will be no “net metering” in this model, meaning no HeathSUN solar power would flow through a PNM meter, the standard way to provide a seamless household electrical system. When someone turns on an appliance in a HeathSUN house, technology in the home’s own electrical control box decides whether to pull from the rooftop solar system or from PNM…

In Hawaii, there is a plan to charge up some big batteries with a big solar array, for use to meet evening/nighttime demands.

The nation’s leading residential installer is building the project near Lihu’e on Kaua’i’s southeast corner. The project includes a 13 MW photovoltaic solar array, but is unique in that it includes its own solution to the intermittency problem that solar power faces.

The power generated by the PV cells will be used solely to charge a 13 MW battery array capable of providing 52 MWh to customers of Kauai Island Utility Cooperative (KIUC), the island’s sole electricity provider. That means the solar cells will charge the batteries during the height of the day, and the batteries will discharge the stored power to customers during the evening peak between 5 p.m. and 10 p.m.

“Anyone that’s been out to Kauai will notice that they have a lot of solar on the island and really don’t have any appetite at all for solar at midday,” Rudd said. “If anything, they were already in a bit of a curtailment state during certain days. So, they love solar, they want more because it’s cheaper than what they otherwise would realize, but they don’t need it during the day.”

New York State is working out the details of how to deploy meters to allow the grid to become smart.

There is a big waste-to-energy project in the works in Oregon.

And that is a sampling of the news that came across my desk just today.