Solar power as a source of electricity has been on a meteoric rise, and has crossed some encouraging milestone recently. Every way you look at it, solar is booming. This is driven primarily by the decrease in the cost of adding solar power, so let’s start there. The Berkley Lab has been tracking the cost of solar power in the US for years, so they are a reliable source of information. They get direct data from the actual price paid by consumers, and break down the cost of panels, the cost of installation, and all the “soft” costs that  are part of the industry. In 2009 the total cost of installing solar between $7 – 8.70 per watt. An average US residential home installs a 6-8 kW system, with the average increasing over the years. In 2025 the average size was 7.7 kW. Let’s use a 7 kW system, at $8 per watt, that’s $56,000 total installation cost. Today the average price of installed residential solar in the US is $3.6 per watt (but it is $3.0 if you pay upfront, $4.50 if you finance). So that same 7 kW system now costs $25,200. (If you pay for it outright, the cost drops to $21,000.) So over the last two decades the total const of installed residential solar has dropped by about 60%. This is without considering any tax breaks or incentives. The reason for the decrease is partly that solar panels themselves are cheaper, and they are more efficient, so a 7kW system requires fewer panels. Installation costs have decreased by about 50% over this time, largely due to economies of scale. However, the US still has higher soft costs for solar than many other industrialized nations, and this is mostly a matter of the regulatory system. So there is some regulatory efficiency to be gained. Solar companies themselves also have some possible efficiency gains. Fortunately, the net price for solar continues to go down, with another 50-60% decrease in total price possible even without further technology gains. Commercial and grid scale solar is even cheaper – with large non-residential installations down to $2.4 per watt. It is primarily for this reason that solar is now the most common new source of added grid capacity. Worldwide, wind and solar are responsible for 85% of new grid capacity, with solar making up 73%. Worldwide there is now about 3 TW of installed solar capacity. One TW was added in just the last two years, showing the exponential increase in solar installations. Solar now generates 9-10% of the world’s electricity. This is led mostly by China, which as 50% of the world’s installed solar. For a long time, while wind and solar were increasing rapidly, they were more than offset by the total increase in electricity demand. This is still much better than not installing renewable or low-carbon energy, but it meant that fossil fuel use was still increasing. For the first time, however, total electricity from fossil fuels decreased, by 0.2%, without being caused by an economic downturn (like COVID). This is a tiny decrease, but it is a potential milestone if we have truly turned a corner. Even better, this decrease is driven primarily by coal, which is the dirtiest form of energy. Natural gas plants are still increasing, because they are still necessary for peaker plants, and because of the increased demand of data centers. The rise of solar is helping push down demand for fossil fuel energy, but there are two other factors that will be critical to push them down further. The first is grid battery storage. Battery technology is also improving rapidly. The advent of cheaper sodium ion batteries (which also bypass the lithium bottleneck) is seeing battery grid storage rise considerably. More and more of those home solar installations include battery back up. There are also new innovations, such as plug and play home battery backup, where you can add storage capacity in a modular fashion without any installation costs – just plug them in. Regulations need to catch up to this technology, allowing them to be used for whole home backup, but for now they can be used for targeted backup, like for your refrigerator, or your work station. Grid storage has the capability of reducing reliance on natural gas plants. So does nuclear. We seem to be at the beginning of a revival of the nuclear power industry. This is necessary even if we wish to simply maintain the current percentage of nuclear on the grid, which will help keep fossil fuel use down. The bottom line is that the cost of solar has dropped precipitously, and so if you have not looked into it recently, you should take another look. The prices I gave above were for a fairly large home. The total price of the system scales with the size of the house, which is a marker for the financial resources of the owner. Let’s say you have a more modest house that only needs a 5 kW system. If you pay for it outright, the total cost would be $15,000. The federal tax incentive just ended on Jan. 1, 2026, which is unfortunate but is defensible due to the fact that the cost of solar has dropped so much. However, 30 states still have some incentive, which can save thousands of dollars. But that aside – $15,000 is very affordable. How much this would save depends on a lot of variables, but for an average home in the US it would be between $800 and $1,500 per year. That means the payback time is between 10 and 18 years. After that, you essentially have free electricity. The useful life expectancy of a new system is 25-30 years, roughly double the payback time. Most solar companies now bundle solar installation with batter backup systems. This allows for peak shaving, and backup during outages. There is potential money savings here as well (including every time you don’t loose a freezer full of food). Further, many states offer incentives for batteries as well, if you allow them to use your batteries for grid storage. A battery system can also keep your solar panels functioning during a power outage. The trend lines for solar and battery grid storage are pretty dramatic and there is every reason to predict that they will continue, as further incremental technology advances take place and economies of scale kick in. The post Solar Is Booming first appeared on NeuroLogica Blog.

I often get questions like the one below: “I live part time in Japan. Everyone sees hydrogen powered generators, trains, trucks, etc regularly. High density population means it’s easy to get enough synergy to justify the infrastructure. So sad we aren’t doing more to utilize this great tech. Hydrogen combustion engines emerge as cheap alternative to fuel cells.” https://asia.nikkei.com/business/energy/hydrogen-combustion-engines-emerge-as-cheap-alternative-to-fuel-cells This is often how news about advances in hydrogen tech are framed. The problem is – the limitations with hydrogen technology have nothing to do with the tech itself, so tech advances are mostly irrelevant. Also, hydrogen combustion is not a better solution for most use cases then hydrogen fuel cells. Fuel cells use an electrochemical process to combine hydrogen and oxygen, producing electricity and water. They are about 60% efficient, produce no pollution, and have no moving parts. Hydrogen combustion operates more like a regular engine, but with hydrogen as the fuel. They are about 40% efficient, produce nitrogen oxides as pollution, and have moving parts that operate at high pressure and temperature. They can be, however, more powerful for heavy applications and are cheaper to build. For cars hydrogen combustion is a terrible idea. Maybe there is a use case for large generators, trains, and heavy trucks. Even there, however, there are current limitations that the technology of hydrogen engines or fuel cells do not address. 1 – Storage is a problem. They never figured out the storage problem, so just reverted to compressed hydrogen gas. There are efficiency, range, and safety issues with this. Plus, hydrogen is very leaky and destructive to infrastructure like pipes. 2 – Only about 1% of the world’s hydrogen production is green. Most of the rest is gray – essentially stripped from hydrocarbons. This is actually worse then just burning the hydrocarbons for fuel. If we do manage to ramp up green hydrogen production, it should be used first in industry, like steel production. Massive green hydrogen for transportation is a long way off. 3 – Even if we solve 1 and 2, hydrogen cars are less efficient than battery EV, and always will be (60% vs 80% efficient). This is just physics. Further, battery tech has simply advanced more quickly than hydrogen, and it continues to advance. Hydrogen lost this technology race. We may be able to fix the first issue with new materials, but until we do this is a major limitation. This is the main reason that the “coming hydrogen economy” promised back in the early 2000s never happened. There are three promising ways we may solve the second issue. The first is scalable green hydrogen production. If we had solar arrays or wind farms generating electricity to electrolyze water into hydrogen and oxygen, that could produce green hydrogen. The problem here is – we would be better off using that green energy for electricity. Round trip energy efficiency (electricity to hydrogen back to electricity) is only 30-40%. Better to use the electricity directly. Until we have decarbonized the energy infrastructure, don’t use green energy to make hydrogen for light transportation. Where there may be reasonable use is for hydrogen for heat-intensive industries, like steel, and for heavy vehicles like trains and ships. The second possible solution is if there turns out to be vast reservoirs of hydrogen under the ground we can tap into (so-called gold or white hydrogen). This remains to be seen, however. A third potential source is as a byproduct of nuclear reactors. Any reactor can make some hydrogen by radiolysis – splitting water by radiation. High temperature reactors can also make hydrogen through thermal methods. And any reactor can use their electricity for electrolysis, but this has the same issue as using renewable power. The third issue I think is just inherent to these processes. Battery EVs are likely to be always more efficient than hydrogen fuel cells. There may have been a window 20-30 years ago where hydrogen fuel cells could have leap-frogged BEV’s, but that window is now closed. Battery technology won, and also continues to steadily improve. Even if we make progress in hydrogen fuel cells or hydrogen combustion, we still have a hydrogen storage and transportation bottleneck. There have been advances here as well, but they come at a cost. Liquid Organic Hydrogen Carriers (LOHCs) can bind hydrogen to a fluid for easy storage and transportation, then heat the fluid to release the hydrogen. However, this has massive infrastructure and energy requirements, and would further reduce the energy efficiency of hydrogen. We have also engineered better storage tanks – Type IV tanks, which feature a seamless polymer liner fully wrapped in high-strength carbon fiber. This doubles the pressure under which hydrogen can be stored, doubling the range of hydrogen fuel cells. But it takes 12-15% of the energy stored in the hydrogen to compress it to these higher pressures. A hydrogen economy for transportation would have massive infrastructure needs, from production to pipelines, storage, and distribution, likely to take decades. This is all just to get us to a system that is less efficient than BEVs with similar range. Meanwhile there is already existing battery technology with twice the range of common BEVs today (silicone anode Li ion), or similar range at half the cost (Na ion). Solid state and lithium air batteries could potentially five times or more today’s energy density (1,500 vs 300 kWh). Meanwhile we are already near the theoretical limit of compressing hydrogen (700 bar). At 1000 bar hydrogen atoms repel each other and you get exponential energy requirements for further compression. If we are going to invest in infrastructure, those investments should go to fleshing out a fast-charging network for EVs and securing raw materials for making batteries. The post Hydrogen Tech first appeared on NeuroLogica Blog.

In Isaac Asimov’s The Caves of Steel he imagines a future in which most of humanity lives in gigantic cities, extending many levels underground. This leaves the majority of the Earth’s surface for industrial farming, necessary to feed all those densely populated cities. If you take a similar strategy, however, and keep the population at sustainable numbers, this could maximize land for natural ecosystems and also minimize the environmental footprint of the average person. So if we are going to plan our civilization around environmental sustainability we would not necessarily need Asimovian megacities, but we could concentrate the population in cities and in densely developed areas around cities, and leave large stretches of land in between undeveloped. This is far better than endless suburban sprawl. But of course, we are not starting from scratch, and our current layout was not planned by some central committee but evolved organically. Pragmatically, the question we need to ask is – where do we go from here. Cities are growing dynamic things, so we can use city development to move in a certain desirable direction, even if we can’t tear it all down and start anew. This means it is important to study what the best city planning and development would be going forward. When most people think of city planning to reduce the carbon emissions of transportation, the first thing that comes to mind is planning city centers so that they are walkable/bikeable and to provide public transportation, in order to minimize reliance on fossil-fuel burning cars. This also has the advantage of reducing city traffic, which can be a nightmare. However, a recent study suggests that, while important, this may be of secondary concern with respect to impact on CO2 emissions. For many cities, especially those with a single concentrated hub (as opposed to multicentric cities, like LA), the most impactful strategy might be the densification of a ring surrounding the city center. The range of this ring depends on the city, but is something like 10-20 km for a typical large city, but can extend to 40 km. Increased density can be accomplished with infill development, as many such zones are only moderately developed leaving lots of room for densification. The idea is that the workplaces will be concentrated in the city center, and the workers will live in the ring around the city center, minimizing their commute distance. This could have a significant impact on the average commute distance that people have and therefore their transportation carbon footprint. This approach would work better for some cities than others, depending on geography. This plan could also maximize the impact of public transport, like buses and trains, dedicated to bringing people back and forth from this densified ring to the city center. One of the major findings of the study, which used gps data to track 10 million “mobility data points”, is that there are many interdependent variables at work. It is not as simple as just densifying a certain distance from a city center. Road planning, public transportation, carpooling, and working from home are also important variables that affect each other. Essentially, what this study does is provide additional information to city planners, using an AI model to help individual planning to each city in order to minimize average commute distance. The authors acknowledge that there is still a lot of research to do in this area. The one variable that is always the most difficult to predict is human behavior. For example, we cannot simply build more roads to accommodate increased traffic, because more roads creates “induced demand” and may actually worsen traffic. In this case we need to deal with the fact that many people move out into the suburbs, increasing their commute, because they want to. It’s nice there. At the same time there is a “build it and they will come” phenomenon – people will buy or rent houses that exist. Since we are having a housing shortage, we have an opportunity to decide where to build the millions of homes we need to meet demands. Generally speaking, however, it is a good idea not to assume that people will do what you want them to do, and to provide multiple options for different people with different desires and in different situations. At the same time, when dealing with these big environmental issues, it is not necessary for every single person to do the same thing. We just need to move some people toward behavior associated with lower emissions, by making certain choices more desirable or easier. The effects of behavior and infrastructure on CO2 emissions are cumulative – in both directions, good and bad. I also think generally we should not expect most people to make big sacrifices to achieve our collective goals, not for moral reasons but for practical reasons. But I also think we should not always put the burden on the individual to make the sacrifice. It’s better to look for the win-wins, to make the system work for people rather than making people work for the system, and to provide the infrastructure and opportunity for people to make choices that are good for them and good collectively, in this case for the environment. With all that in mind, what would I like to see in terms of minimizing the carbon footprint of transportation? First, I would love more walkable cities with less traffic, and with convenient low-cost transportation options. More convenient and cost effect transportation options into city centers would also be nice. Where I live the best option I have is to drive to the nearest train station and then pay ridiculous prices for a train ticket. If the family is taking a day-trip to the city, it could literally cost hundreds of dollars. Also, as this study indicates, careful city planning to minimize commute distance could have a significant impact. There is a confluence of issues here. In the US we lack overall housing, we also lack mid-level housing in terms of costs.  We need more condos, row houses, and multi-family units – something between an apartment and a large house sitting on a half-acre. These are exactly the kinds of homes that could be built to densify key regions around city centers. We could essentially address three problems at once. Meanwhile, we need to continue to convert from fossil fuel burning to electric vehicles. These are more energy efficient and have a much lower carbon footprint over their lifetime. They are also now cheaper to own and have much less maintenance. Having shorter average commute distances would also make EVs, even those with modest ranges, more convenient. We are already past the technological tipping point in terms of the features of EVs themselves. The big issue is that we need to continue to build out the EV public charging infrastructure. They need to be ubiquitous. I also think that we need to make a big push for working from home. This happened during COVID and I was hoping that everyone would realize the benefits and the trend would continue. However, once the pandemic was over some businesses snapped back to their old policies, and mostly with no good reason. We did make good progress, but not as much as we should have. We should be doing everything we can to maximize working from home. If the average worker worked from home 2 days a week, that would reduce commuting by 40%. This massively reduces traffic and CO2 emissions. Increasingly many people’s jobs involve lots of time sitting in front of a computer. There is no reason for them to commute to an office to do that. Schedule meetings on one or two days a week. In fact, in my experience, many work places have too many meetings. Most of what needs to be accomplished can happen in virtual time, then you can have one meeting to review everything. Obviously this has to be individualized to the workplace, but there are many businesses where there are lots of opportunities to reorganize workflow so that many people can work from home much of the time. Further – working from home increases productivity. The same is true of the 4 day work week – it maintains or increases productivity. This is because of the same principle I discussed above – people are not machines that will just do what you tell them (short of oppressive environments). People work more efficiently when they are in a better mood, and have a better work-life balance. Most of these things are win-wins. People do not want to spend large amounts of their life stuck in traffic, sitting in a car that is spewing out pollution. So give them other options, make commutes shorter, let people work fewer days and many days (or all days) from home. Provide cheap public transportation. And when they do have to drive, EVs are a superior option for many people, and we should do what we can to make it the best option for as many people as possible. The post City Planning and CO2 Emissions first appeared on NeuroLogica Blog.

I came across a few news items that I could possibly write about today and couldn’t decide which to cover, so I will write about all of them, since they all relate to renewable energy. The first is a new study comparing direct air capture (DAC) to installing new wind and solar. This is a direct comparison between these two options, to see which provides the most bang for the buck. DAC involves taking CO2 directly out of the atmosphere in order to mitigate carbon release through burning fossil fuels. If this technology were sufficiently efficient it could be hugely useful in reducing future climate change. This is the only approach that can potentially have a negative carbon footprint, actually reducing the amount of CO2 in the atmosphere. Other technologies simply reduce the amount released. This negative carbon factor is highly attractive since it could theoretically zero out our carbon release and even take us back in time to an atmosphere with less CO2. Right now, it should be noted, we are not only continuing to release massive amounts of CO2 into the atmosphere, the amount continues to increase. In 2025 the world emitted 38.1 billion tonnes, of carbon, a 1.1% increase over 2024. But there are problems with DAC – it is currently not very efficient and is not scalable enough to have enough of an impact. Also, the efficiency of DAC depends heavily on how you power it – if you connect it to the grid and there is some fossil fuel energy on that grid, you may actually increase CO2 rather than decreasing it. Ideally DAC would be powered entirely by low carbon energy sources. This is why critics of DAC argue that it simply makes no sense to deploy this technology before we have decarbonized the energy sector, which we should do first. In the current study they ask a critical question – if we directly compare DAC to deploying wind and solar, which provides the greater reduction in energy pollution per dollar spent. They also considered both the environmental and health impacts. They further considered three scenarios – current DAC technology, significant advances in DAC technology, and a massive breakthrough in technology. They also did their analysis for the entire US and for different regions. What they found was that deploying renewable energy was more cost effective for every region of the country under the current technology and significant advances scenarios. In the massive breakthrough scenario the results were mixed by regions, with a slight net advantage country-wide to DAC. In my opinion this just adds to the conclusion that we should first decarbonize the grid with a combination of low carbon energy sources, including maximizing wind and solar while maintaining or even expanding our nuclear infrastructure, and only then invest in significant DAC. We can continue to research DAC in the meantime, and then deploy only when it gets significantly more efficient, in order to offset industries that are difficult to decarbonize. There are a couple of solar power updates worth discussing as well. The first is that we are getting very close to commercializing tandem silicon and perovskite solar cells. Silicon is the current standard, with most commercial panels at 22-23% efficiency, with high-end panels at about 26%. This is pushing up against the theoretical limit for silicon (32%), and many experts think we will not get much closer to this theoretical limit because of some unavoidable sources of energy loss. This is where perovskite comes in – this is widely considered to be the next material to replace silicon in high efficiency solar cells. But even better, silicon and perovskite absorb light at different frequencies, so when you combine them in tandem you get even higher efficiencies. The current record is produce by LONGi (a Chinese solar panel company), with a commercial tandem panel with verified 34.6% efficiency. They plan to make these panels available in 2027-2028. Also, the theoretical upper limit of efficiency of this tandem design is 43%. However, perovskite still has a longevity problem. For these tandem panels the silicon component lasts 20-25 years with minimal efficiency loss. The perovskite, however, only lasts 10-12 years. This is insufficient for residential use, but still useful for grid-scale projects. With large projects it is cost effective to pay for the higher end panels, and replacing them with even better panels in 10 years is not a bad investment anyway. But home owners don’t want to do this. However, there is a great deal of research into extending the lifespan of perovskite panels (for example). Another Chinese company, GLC, has announced a tandem solar cell with a 25 year warranty, and with an efficiency of 26%. We are quickly heading for panels with both efficiencies in the mid 30s and a lifespan of 25 years. The availability of relatively cheap and highly efficient solar panels has also given rise to a new industry – plug-in solar (also called balcony solar). These are stand-alone panels you simply plug into a regular outlet, which can both accept and deliver energy. That’s really it. You have to mount it somewhere, but most people do not put it on their roof but rather on a stand or attached to their balcony or similar structure. This is useful for renters, apartments, mobile homes, remote locations like cabins, or even to supplement existing rooftop installations. In general you will recoup the cost of the panel in reduced energy bills in seven years, while the panel itself should last for 30 years. These are already very popular in Germany where they have been used for a decade without any safety issues. Utilities companies in the US have been trying to slow their adoption, arguing that they present safety issues. For example, if they are sending current to the grid they could endanger utility workers. However, this is likely a diversionary tactic to slow the adoption of a competing technology. Units are already designed not to send energy to the grid when there is a power outage. The safety record in Germany is pretty solid evidence that they can be used safely. For most users plug-in solar would not power their entire home, but would shave money off their energy bill and reduce their carbon footprint. The great thing about plug-in solar is that there are no issues with grid stability since most users will be simply reducing their baseload demand, not producing excess energy that has to go to the grid. But because they can be widely distributed, these small reductions in grid energy demand can be significant. This could be a useful supplement to grid-scale and rooftop solar. And of course they can be especially useful when paired with home battery backup, or even just an EV. With recent events in the Mideast, including national average gas prices at $4.45 per gallon and electricity costs up 7.4% over last year, it seems like a good time to push for energy technologies that are not reliant on a vulnerable infrastructure partly in unstable parts of the world. These events also highlight that we can never achieve true energy independence simply by producing more oil, as oil prices are set as a global commodity. Solar, however, can be true energy independence, harvested right where it is used. Of course, this raises an entirely different discussion about maintaining domestic renewable energy technology and raw material supply chains. This is why invested in the technology of tomorrow rather than doubling down on fossil fuels is so critical. The post Some Renewable Energy Updates first appeared on NeuroLogica Blog.