Post #1936: What if this is as good as it gets?

Source: Data are from U.S. DOE, Sources: U.S. Energy Information Administration, Form EIA-860, Annual Electric Generator Report. U.S. Energy Information Administration, Form EIA-861, Annual Electric Power Industry Report. U.S. Energy Information Administration, Form EIA-923, Power Plant Operations Report and predecessor forms.

When technology produces big leaps in energy efficiency, it’s pretty easy to make meaningful reductions in your carbon footprint. Just buy newer stuff.

But as a long-term observer of this issue, it seems to me that technology-driven gains in energy efficiency are hitting their limits. There are a lot of important areas — cars, fridges, lighting, and even electrical generation itself — where any further reductions in carbon footprint look a lot more difficult.

What I’m trying to say is, looks like technology has already grabbed the low-hanging fruit.

I’m not going to belabor the societal implications of this. For me, this means that once I’m driving an EV and living in a house with an efficient heat pump and LED lights, there are no more easy reductions in my household carbon emissions. Nor are there likely to be, for the foreseeable future. Lifestyle changes, yes. Effortless reductions in emissions, no.

Maybe this is as good as it gets.

The fridge as canary in the coal mine.

In my last post, I was struck by how little progress has been made in refrigerator efficiency over the past 20 years. If I take my original graph of typical fridge energy use, through 2014 or so:

Source: Appliance Standards Awareness Project. Annotations in red are mine.

And I now simplify it, and append the proposed U.S. D.O.E. standard for 2030, to scale, it looks like this:

So, for fridges, it really isn’t my imagination. There were huge gains in fridge efficiency in the decades following the original Carter-administration/energy crisis push. But the pace of change has slowed. And, in fact, I see that the industry has characterized this proposed regulation as reducing energy use 10% to 15%, below current standards.

We’re no longer in an era when replacing an fridge more-or-less guarantees a significant improvement in operating efficiency and operating cost savings. Instead, looking back at the proposed regulation (here), assuming I’ve done the math right, it looks like the operating cost savings, for the typical fridge, for the typical consumer, might amount to $5 per year.

In other words, to an approximation, the efficiency difference between the fridge you might be able to buy in 2030, and the fridge you can buy today, will be more-or-less rounding error.

The upshot is that here in America, buying mainstream appliances, keeping the same size and features as you now have, you are not going to be able to reduce the energy use of your home refrigerator.

The fridge you can buy today? In terms of efficiency, that’s just about as good as it gets, for the foreseeable future.

Cars?

Improvements in traditional gas-engine vehicle efficiency have been slow-to-nonexistent for the past three decades. Modest improvements in design and materials of a traditional (“Otto-cycle”) gas car resulted in incremental increases in gas mileage.

Here’s the Toyota Corolla, four-cylinder, four-speed automatic transmission, from 1985 to 2020, per fueleconomy.gov.

Better, but hardly revolutionary. And hardly enough to make a dent in the global warming potential of cars.

Instead, the great leaps forward in car efficiency came from two revolutionary ideas.

The first was the introduction of Atkinson-cycle engines (powering hybrids), compare to the standard (“Otto-cycle”) engines in non-hybrid cars. Here’s how Toyota Corolla (top line) stacked up against the Toyota Prius (bottom line), 2005-2020:

With that single change, you could go almost twice as far on a gallon of gas. And while the Prius was the innovator there, you will find that all the high-MPG hybrids offered for sale in the U.S. now use Atkinson-cycle engines. It has simply become the way to get the best mileage out of gasoline, period.

Source: Post #1613, How the Prius Does its Thing

But note that improvements of the Prius itself, over time, were modest. The big bang-for-the-buck was replacing the inefficient Otto-cycle engine with the more efficient Atkinson-cycle (or Miller-cycle) engine. That change allows you to extract much more energy out of a given charge of gasoline. But once you’ve made that switch to an Atkinson-cycle gas engine, further gains are minimal. Where an Otto-cycle engine might top 20% efficiency, you might be able to get 40% efficiency out of an Atkinson-cycle engine. But there’s no way to get more than that. You’ve topped out.

The second revolution in car efficiency was the modern electric vehicle. You can quibble over exactly what the US EPA “MPGe” figures mean, but here in Virginia, they are, purely by coincidence, an excellent indicator of carbon footprint. When a car says 100 MPGe on electricity, it produces about half as much C02 emissions per mile as one that gets 50 MPG on gasoline.

Above, these are all cars about the size of a Prius (the Hyundai is somewhat larger), and each of them gets about twice the mileage of a Prius. So even as the Prius doubled the MPGs of a Corolla, these new EVs in effect double the mileage of a Prius.

But, as with the Prius, the big improvement was in switching from gas to electric. Gains over time, in electric car efficiency, are minimal. Like so, for the Leaf (top) and Bolt (bottom), over time (left-to-right):

There’s a good reason for that: These cars are about as efficient as they are ever going to get. Batteries may get better, perhaps. But electric motors have been around a long time. And while there may be some tweaks left to do, there are no more “leaps” in efficiency to be had. Even including the inefficiencies associated with moving electricity into and out of batteries, these vehicles are probably 70% efficient overall. There really is not much upside potential left.

The electric vehicle you can buy today? That’s just about as efficient as cars are going to get, for the foreseeable future.

Any reader who whines “but what about Hydrogen” should memorize the phrase “Hydrogen is little more than transformed electricity.” Hydrogen cars ARE electric cars, where the battery is replaced by a hydrogen-powered fuel cell. They are just ridiculously inefficient electric cars, owing to the losses involved in converting electricity to hydrogen to electricity..

As a thought experiment, unplug my electric car, and instead of using 1 KWH to travel (say) four miles, take that 1 KWH and use it to make hydrogen. The energy value of the resulting hydrogen will be, at best, 0.66 KWH or so. Now run that hydrogen through a typical car-sized fuel cell to generate electricity . The energy value of the resulting electricity will be, at best, around 0.33 KWH or so. Now use that 0.33 KWH to power my car. And now explain to me why that was, somehow, a smart thing to do.

Hydrogen might have made some practical sense 30 years ago. Then, the limits on batteries meant that EVs had pitiful range, and low efficiency. If that’s the competition, then running your car on a a tank full of hydrogen didn’t look half bad. But three decades of slow advancement in battery technology have completely changed the picture. They have rendered hydrogen-powered cars obsolete. Hydrogen is a zombie technology. Dead, yet it refuses to die.

The grid

All of which leads me back to the grid, and commercial electrical generation. If I travel in an EV, and heat/cool my house with a (ground-source) heat pump, then for me, if the individual technologies have matured, it’s all about the carbon-intensiveness of the grid.

Virginia, like many states, has a long-term goal, set in law, of having a carbon-free grid. I believe ours is set for sometime in the 2040s or so.

And, as shown above, we’ve made great progress. C02 per KWH has fallen by roughly half, over the past couple of decades.

Which looks great until you figure out how we managed to do that. So far, virtually all of that improvement comes from substituting natural gas for coal.

And so, I’m betting that progress on de-carbonizing our electrical generation will follow the same pattern. We’ve already done all the easy stuff. Operationally, the only difference between a gas-fired generator and a coal-fired generator is that gas-fired plants are easier to start up and shut down. And there are no ashes to be hauled.

Nobody seems to have any plans for new nuclear plants on the horizon. Certainly not here in Virginia.

Which means that from here on out, reducing the carbon-intensiveness of the grid means substituting intermittent renewables for gas-fired generation. And that’s just a whole different magnitude of difficulty, compared to decommissioning one type of fossil-fuel-fired plant (coal) and commissioning a different type (natural gas).

At the end of the day, I think this is going to be deja fridge all over again. Absent some true as-yet-to-be-conceived miracle of technology, the de-carbonization we have already witnessed may be the bulk of all the de-carbonization that ever occurs.

Any reader who whines “but what about rooftop Solar” should memorize the phrase “Any grid-connected solar array is exactly as dirty as the grid it’s connected to.” A homeowner’s rooftop solar makes the entire grid a tiny bit cleaner. But, in effect, everybody on the grid consumes the exact same electricity. Explaining that one is going to require its own separate post, I think. Grid-connected rooftop solar is unambiguously good. But the electricity consumed in by the solar array owner is the same as everybody else’s electricity.