Category Archives: Electric Grids and Transmission

A Tale of Two Energy Futures

Te Apiti wind farm in New Zealand.

The Te Apiti wind farm in New Zealand. About 80% of New Zealand’s electrical power is generated from renewables, making it an example for the world.

I often joke with Mr. X that “I can see the future”. Yes, I’m usually kidding, but the other day I was thinking about an article about energy that I had read, and the future did indeed seem to me to be as clear as a bell. To back up a bit here, the article is by John Mauldin, an economic analyst, and it is his take on low oil prices, entitled “Riding the Energy Wave to the Future“. It’s well worth reading, but if you want the quick summary, here’s my very-short paraphrasing—

Marked improvements in oil and gas production technology (especially fracking technology) are largely responsible for today’s low oil prices, and these improvement trends are likely to continue. As such, prices for oil and gas are likely to remain low. BUT, the same types of innovation are also causing prices to drop in the renewable energy field, especially solar and wind, and the prices there WILL DROP EVEN FASTER. The likely outcome of this, according to Mauldin, is that future energy prices are likely to be low across the board, and that natural gas will continue to eclipse coal and is likely to become a “bridge” fuel between fossil fuels and renewables.

Now, I think that Mauldin’s article is basically on the right track (I wrote about a closely related topic, grid parity, here).

(And now for an aside—this, as opposed to another article I read this week, that I won’t link to, that went on and on, seemingly supported by all the relevant statistics and graphs and written by someone with all the proper credentials, about how low oil prices are a sign that resources have run out and global growth is permanently slowing and will soon collapse. There are thinkers in the peak oil and similar movements who confidently swear that collapse is imminent every single year. Continue reading

Project Photos, Phase One

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The meter sockets. The one on the right is the “gross meter” to record solar input to the grid. So far my wiring has passed muster with only a few minor changes needed. A small change required here; the equipment ground in the solar meter can’t go straight to the ground rod.

Well, I think I’m roughly on track with the add-a-bunch-more-solar project (if you missed it, see post from the other week “And the Project Begins“). I gave myself a month to complete the conduit runs underground, and we finished that today; almost two-thirds of a mile of conduit. Green Mountain Power is still waiting on one easement from a neighbor (a pole on their property will need an additional stay), so they can’t pull the high voltage wire in yet. But, my part is done, so it’s on to the solar panels on the barn roof. Some photos of this portion–

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The conduit at the house end of the run from the barn to the house. The main breaker is at the barn, so this is secondary power coming in to a 100-amp subpanel. The conduit on the right is for internet, with 500-lb strength pull cord getting pulled through as it gets put together.

 

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All the dogs, having a good romp.

 

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The main trench to the road; 42-inches deep. The high-voltage line will get pulled through this conduit; 7,000 volts in a single large co-axial cable, to a transformer at the barn. For this portion of the run we put the communications/internet conduit one foot above this one as we backfilled.

 

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The goal– to get to this stake. A single pole goes here, near the road, before the run goes underground. The last few feet can’t be dug until the pole is set, and then it has to be backfilled immediately and tamped.

 

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The deep well for the transformer (cabinet visible behind the dirt pile), and the internet conduits stubbed up in the foreground. The internet run splits from the power run at both cabinets; communications cables must be at least five feet from the high-voltage cabinets.

 

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The view down the valley as we work. It’s been reasonably pleasant so far, but I’m definitely racing winter; a bit of snow the other evening was a reminder…

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The new 225-amp load center in the barn, with the solar feed coming in at the top, the grid power coming in from the left, and the feed to the house going out toward the bottom (not all of the cables are attached in this photo).

Anyway, last night I unpacked all the invertors and racking and other parts for the solar modules on the roof, and I’ll just call that part “Phase Two”. I’ve given myself a month to get that part in place; I’ll post pictures.

 

And the Project Begins…

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After ten years off-grid, in comes the power…

Ok, a post about the project here. We built our house ten years ago, and have powered it ever since with wind and solar. Almost. During the short, cloudy days of November and December, and other times when we get a string of stormy days, we sometimes need to run a gas-powered backup generator. For years I’ve thought about adding enough solar to completely free us from the generator and fossil fuels, but in an off-grid setup the system becomes more and more inefficient as you add more panels, because you’re adding generation that you might only need to use 5% of the time. The other 95% of the time, all that potential power goes unused (for more about this inefficiency, see my post “Not Sexy” ). But, we were very close to net-zero despite the generator use, and I wasn’t quite sure how to change the system in a way that would make economic sense.

Then we got the electric cars. Which we love. And then I started wondering about powering not just the house with solar, but the cars, too. Suddenly, the thought of tying to the grid for more efficiency began to seem like a practical path forward. Then, I realized that a number of renewable energy rebates and incentives are set to expire at the end of this year, so it seemed like a good time to push ahead with the entire grid-tie, add-more-solar plan.

So, that plan, now underway, is to bring in the grid power in from the road, underground, to the barn. Then, I’ll reverse the cable run that currently takes power from the house to the barn, and use it to bring power the other way, from the barn to the house (the barn is between the house and the road). Then, I’ll add 10,000 watts of panels to the barn roof, and grid-tie them with Enphase micro-inverters. The current PV system, with the inverter in the basement, will stay largely intact, but will become a fairly robust PV and battery backup system for those times every year when the grid power goes down.

That’s the very short version, anyway. Oh, and then we’ll replace the propane hot water heater with a new, highly efficient electric heat pump water heater, which will virtually eliminate the propane bill.

If all goes well, monthly cash flow should about even out. We’ll pay for the home-improvement loan, but we’ll be able to mostly quit buying propane (we’ll still keep the propane range-top, for now), we won’t have to buy fuel for the generator, and we can charge the cars here and save the money that we normally reimburse my wife’s place of work. On the practical side, I can also quit fueling and maintaining the generator, and can quit climbing up on the scaffolding next to the barn all winter to rake the snow off the solar panels.

Then, after fifteen years the system should be paid for. After that—virtually free utilities and transportation energy, for decades.

That’s the rough outline, anyway. There’s actually a lot more to it, but I’ll discuss the details as they come along. Until then, I’ve got plenty to do…

 

Grid Parity

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A graph put together by Deutsche Bank—solar is likely to be cheaper than grid power in the relatively near future. Other forecasts vary a bit, but all tell this same basic story.

If you aren’t familiar with the term “grid parity”, then perhaps you need to be, because it might change your life. Here’s the simple version—electricity created by solar panels is, in most cases, more expensive today than what most Americans pay for grid power, even when calculated out over the life of a photovoltaic system. But, prices for conventionally-produced grid power are slowly rising, and prices for solar are steadily dropping. At some point in the relatively near future, solar power is going to be the same price as grid power—“grid parity”. And after that? Solar will be cheaper, and this likelihood has some large implications. I recently heard Alec Guettel, co-founder of Sungevity, Inc, say that “Solar has won, but the world just doesn’t know it yet”. I think he might be right.

Now, it’s a bit hard to truly pin down “grid parity”, because, like everything else, it’s complicated. Not every region of the country will get to grid parity at the same time; a number of factors affect when those two lines in the graph above will cross. Key among them—the price of grid-power in a particular location, how sunny it tends to be there, how much it costs to get solar installed (those that can do it themselves might save enough to be at grid parity now…), whether or not the system is financed (and at what interest rate), whether the electric company offers time-of-use pricing, and whether there are subsidies or tax credits available. Sunnier locales with relatively high utility rates will hit grid parity first (or have already). In the U.S., places like Hawaii, southern California, and Arizona are already at or very near grid parity even without tax credits. In the slightly-less-sunny Northeast, the federal 30% income-tax credit on solar installations, or third-party ownership models, like those offered by Sun Common and others, make solar pay here, too, in many cases.

Here’s an example of a form of grid-parity that pertains to my post the other week about commercial solar installations (post: “Rooftops Please”). Even here in slightly-less-sunny Vermont, a combination of federal tax credits, accelerated depreciation, the value of Renewable Energy Credits (RECs) and a form of time-of-use pricing offered by Green Mountain Power make large-scale solar arrays, like those in open fields like I was discussing the other week, pay off. (GMP offers a 6-cent premium on each Kwh of electricity from grid-tied solar installations, an “adder”, paid because solar is produced at or near peak demand on sunny days, when wholesale electricity on the spot market is expensive). In these situations, grid parity has been more than reached, which is why you see these installations springing up all over the place—somebody’s making some money.

And, virtually everywhere, if you are able to install solar yourself, on a roof that you already own, you are likely already at grid parity. In my case, building a house that was 1500 feet from the power lines, solar made sense even ten years ago due to the cost of the bringing in the power lines, which is why we’ve been off-grid all of this time. (Though that’s set to change; I’m about to dramatically expand our solar production to run the EV’s on solar power, which will entail grid-tying. More about this project in a future post.)

Now, about those implications—some thinkers worry that grid parity will result in a death-spiral for utility companies, as more and more customers abandon the utilities and put up their own systems, which would raise the cost of transmission for the remaining customers, and thus rates, resulting in still more customers pulling the plug. I don’t actually think this is likely—grid-tied systems are actually quite a bit more efficient than off-grid ones (see my post, “Not Sexy” ). In addition, large urban areas and manufacturing facilities will always rely on the surrounding countryside for renewable power, which will entail a grid. Rather, I think the most likely implications are actually good for the planet—it’s likely that solar power will truly boom in the coming years as it gets cheaper and cheaper, and we will actually begin to fully transition to an economy powered by clean, renewable power. That’s some truly good news. As for personal implications—keep your eyes open out there, because you might be able to install solar and come out way ahead, and it might be sooner than you think.

Graph credit: Deutsche Bank

The Real Reason Why EV’s Matter

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An example of one of the many new EVs on the market; a screenshot from Organic Transit’s webpage, about the ELF. According to the company, the ELF gets the equivalent of 1800 mpg.

I was at this year’s Solarfest this past weekend, and helped present two workshops about electric vehicles. The first one was a panel discussion hosted by Drive Electric Vermont, and the second was a presentation I did, entitled “Electric Vehicles: Beyond the Basics”. I think that my thesis, so to speak, is worth thinking about, so I thought I’d recap the presentation here as a blog post.

The quite-short-version, starting with some basics—

1) Whereas a few years ago there were essentially four mainstream production EV’s, (the Volt, Leaf, Tesla Model S, and the plug-in Prius) there are now about twenty, with many more on the way. The biggest recent news is perhaps BMW’s i3, a $40,000 car that is the most efficient in its class, partly due to its lightweight carbon-fiber cabin. The car has gotten extremely high customer-satisfaction ratings, and has been successful enough that Tesla just announced last week that is would be putting together a “Model 3” that will be quite similar. And, EV’s now encompass far more than just cars. There are electric motorcycles, electric pickup trucks, buses, bikes, scooters, school buses, tractor-trailer trucks, and more.

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Zero Motorcycles, perhaps the leader in electric motorcycles.

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Bus-maker Proterra already has buses operation in several U.S. cities, including Reno, NV. With “One-fifth the fuel expense and one-third the maintenance”, these more-expensive buses can pay for themselves in two to five years.

EV owners’ customer satisfaction has been quite high; the Volt and the Tesla Model S have led Consumer Reports’ rating for the last three years.

2) Adoption rates have been brisk, though not quite as brisk as some predicted in years past. The number of EV’s on the road has roughly doubled each year since 2010, and that trend is expected to continue into the foreseeable future. There are currently about 250,000 EVs on the road today in the U.S., and about 500,000 worldwide. To keep those numbers in perspective, though, EV’s currently make up less than 1% of the cars being sold.

3) Charging infrastructure has grown at an extremely rapid pace, from less than 2,000 public charging stations in the U.S. in 2011, to well over 20,000 today, with many more coming into service daily. This has included a huge rise in the number of DC fast chargers, which can charge a vehicle like a Leaf to about 80% in about 30 minutes. A year ago Vermont had zero of these fast chargers, but today we have six, with more on the way. Further advances in charging technology are also on the way, one being inductive charging, which can charge an EV without a direct connection to the vehicle. As demonstrated by a bus system in operation in Seoul, South Korea, inductive charging systems can also be embedded in roadways and function while the vehicles driving above it are in motion.

4) Most EV’s are powered by lithium-ion batteries, and the price for these batteries has fallen dramatically in the past five years, from well over $1,000 per kwh, to about $500 per kwh today. Prices are expected to continue to drop, partly due to Tesla’s new “Gigafactory”, currently under construction. Tesla’s founder, Elon Musk, has predicted Li-ion battery prices in the $250/kwh range by 2015. (Nissan just announced $270/kwh prices for replacement Leaf battery packs.) Combined with economies of scale as EV production increases, I suspect that EV’s will approach outright cost-parity with gas-mobiles in the decade to come. Research is currently proceeding apace on all manner of battery technology, and these advancements have the potential to disrupt power companies, as well as automobile markets.

5) No battery lasts forever, but indications so far seem to show that EV batteries are exceeding expectations. Battery longevity is strongly influenced by many factors, such as average battery temperature, charging and discharge rates, depth-of-discharge, and the average state-of-charge during storage, and some of these are factors that owners can control. When the capacity of EV battery packs does drop below what is considered usable (typically considered to be 70% of its original capacity), power companies have working prototypes of grid-storage options that utilize used EV battery packs. Then, when EV batteries finally do reach the end of their useful life, virtually 100% of the materials in them can be recycled. Today the market value of lithium is such that it is not currently recovered, though the nickel and cadmium and other metals are. I suspect that this will change in years to come, though world reserves of lithium are quite ample, with the bulk of them in the “ABC Triangle”, an area in Argentina, Bolivia, and Chile. (See article “The Lithium Battery Recycling Challenge”).

6) It is becoming easier and easier to build net-zero homes (post- “Net-Zero is Possible”), but what’s really exciting is that it’s now quite possible to build a home that produces enough power for both the house AND for electric-powered transportation. In fact, I currently know of at least three houses that fall into this category. With building and transportation together making up nearly 90% of U.S. energy use, this is truly an exciting development. And since PV panels operate with DC electricity, as do EV batteries, companies like Honda are working on equipment that allows EVs to charge with DC from PV panels, which avoids the conversion losses incurred by inverters.

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Structures that produce most or all of the energy they require are now quite common. Leslie Science Center Nature House, Ann Arbor, MI.

7) EV’s have a huge potential role with regard to how sustainable power grids will function in the future. This is sometimes called “Vehicle-to-grid”, or “V2G”. A starting point for this is charging equipment that allows power from an EV to go in two directions, either into the vehicle to charge the battery, or out of the vehicle to power the house or grid. Several companies, including Nissan, already have such products on the market. With such a connection, an EV can serve as backup power during a power outage. Then, when this technology is coupled with smart meters, EV’s can serve a key role in reducing generation costs for power companies. In times of peak demand, a power company could remotely stop EV’s from charging, in order to lower peak demand, or, conversely, turn on chargers to soak up excess generation during off-peak hours. Power companies will likely pay customers for the right to control their chargers and EVs in this way, and several pilot projects are already underway. V2G capability also opens up the possibility that EV owners can charge their cars with cheap off-peak power, and sell this power back to the grid during hours of peak-demand.

8) Now, a bit of an aside, but I’ll come back to EV’s in just a bit—as we get higher and higher penetration rates of renewable power into the grid in the years to come, the nature of electricity pricing will steadily change. In the 1970’s it was thought that nuclear power would make electricity “too cheap to meter”. That did not happen, but it has indeed happened recently due to solar. Germany, with its huge amount of solar and wind production, has already seen wholesale electricity prices on sunny days dip into the negative. As these power production curves shift, it will present challenges to power companies. A visual of these upcoming changes was recently released by California ISO (ISO’s, or “Independent System Operators”, are groups that manage grid-power in particular regions), in the now-infamous “duck graph”—

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The infamous California ISO “duck graph”. Shaded areas represent steadily increasing amounts of solar generation.

Proponents of renewable power delight in this graph, seeing steadily decreasing peak energy prices and less fossil-fuel use, whereas Continue reading

For Those With Shady Yards…

The Community Solar array in Rutland, VT.

The 150 kw Community Solar array in Rutland, VT.

The other day I, when I wrote about how it’s “Not So Complicated” for individuals to install solar arrays to power their homes and vehicles, I’m sure there were some readers out there who raised their eyebrows. Some of them must have thought that it can’t be quite as easy as I made it out to be. In some cases it is exactly that easy, but there are exceptions, because there are instances where it would be difficult or impossible to make a solar PV system work. A few of these situations come to mind right away—people who rent, instead of owning their home, or, people that own condominiums. Or, a house on the north side of a big hill (or the south side in the southern hemisphere), or a house with huge trees that shade the roof but that are too beautiful to cut down, or a house with a roof design that doesn’t lend itself well to the installation of solar panels. But, innovation to the rescue—there are new projects coming online that solve these very problems.

In fact, I drive past one of them nearly every day (picture above). It’s called a “CSA”, or “Community Solar Array”, and it was just recently built by NRG, in conjunction with Green Mountain Power (more info at NRG’s Community Solar page). The idea is fairly simple—people who want solar power but choose not to install it on their property can buy a “share” of a large array that is located nearby, and the power that is produced is tied to their house via net-metering. The financial arrangements vary from project to project, but the customer typically either buys a portion of the array outright, or leases a portion of it for a given period of time. In the array above, fifty GMP customers share the power, through a variety of lease options.

So, do you have a roof shaded by beautiful trees? Or do you rent? In more and more locations you can do solar anyway, though your “personal array” might be three blocks away and right next to 49 others. Hopefully, eventually, that option will be available to every utility customer, everywhere.

Not Sexy

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Off-grid or grid-tied—that is the question. La Bastilla Ecolodge, Nicaragua. Hmmm, there’s no ice there…

Something’s become more and more apparent to me lately as I ponder our off-grid setup—being grid-tied is inherently more efficient than being off-grid. I know, nothing too sexy here with this technical point, but it’s an important realization, and it has implications for the larger systems that nations need to be working toward.

In my case, as I add generation to approach net-zero, each additional kilowatt of capacity will be needed less and less. Some numbers to illustrate—we are off-grid, and have about 3 kw of solar PV installed in two large arrays. On a sunny day in the summer, when the days are long and the sun is high, the system can produce over 20 kwh’s of power. We tend to use about 7 kwh a day, which means that in the summer we’re often making about three times the amount that we use or can effectively store. The batteries tend to be full by 10:30 in the morning on such days, and then the panels do very little for the rest of the day. In December, however, it’s quite the opposite, with much shorter days and a lower sun angle. At that time of year we only average about 4 or 5 kwh’s of generation each day, which is a bit shy of what we need, and so we run the gas-powered generator off and on, especially in November and December. Usually by mid-January the skies are clearer and the days start lengthening a bit, and we start breaking even again, and continue that way for the next ten months.

So, our house is close to net-zero, but I’d like to completely eliminate those hours where we need to run the gas-powered generator. If I added 2 more kw’s of PV capacity, I’d probably get really close. BUT—that investment (probably $4,000 if I did it myself) would only be needed for about two months a year. Thus, for about 80% of the year it would just sit there essentially unused, which would equate to hundreds of kwh’s of uncollected, and therefore lost, power. In short, the closer I approach being fully net-zero in the off-grid setup, the less efficient the total system becomes. Needless to say, this isn’t good—in addition to the expense, everything has environmental costs when produced, even technology that we need more of like solar PV, so it seems like it would be a case of not using our resources wisely.

If our house was grid-tied (which it never has been, due to the potential expense, because we’re something like 1,500 feet from the power lines), the story would be dramatically different. All those hundreds of kwh’s that I currently am forced to waste would flow into the grid, which would enable to power company to generate less. At other times, when our demand exceeded our production, I would draw these “banked” hours back from the grid. This is actually another of those win/win/win situations. It would be more efficient—it would keep my solar production from being wasted, the losses incurred by transforming power to and from a chemical state in the batteries would be avoided, and when generation is required, it would be done by the power company’s much-more-efficient stationary natural gas plants, or by grid-scale wind or hydro.

Yet another win/win---power companies on both the Canadian and U.S. sides of Niagara Falls generate 4.4 gigawatts of hydroelectric power, without destroying the beauty of the falls.

Yet another win/win situation—power companies on both the Canadian and U.S. sides of Niagara Falls use the river to generate 4.4 gigawatts of hydroelectric power, without destroying the beauty of the falls. This is the equivalent of about four nuclear power plants.

The power company benefits as well—peak solar hours often overlap with peak grid demand, so grid-tied solar inputs tend to reduce peak demand on the grid. The opposite tends to be true when grid-tied homes are pulling from the grid, say, in the middle of the night to charge EV’s, during times of very low demand. The net effect is that grid-tied systems help level the grid. Many power companies, like Green Mountain Power (GMP) here in Vermont, seem to be embracing distributed generation for another reason—taking the long view, they seem to recognize that the role of power companies is and will be changing, away from the old idea of generating power and distributing it in one direction for a single price, and to the model of the power company as a manager of a complex grid that buys power from many sources and distributes it, as needed, in all directions, perhaps with time-of-use (TOU) pricing. (See earlier post “Cloudy Day Pause” for more about how grids might function in the future.)

Remarkably, being grid-tied would probably be a better choice even if I had to use a power company, like some in the Midwest, that rely nearly 100% on coal. Being grid-tied does not change the total amount of fossil fuel that is burned—the companies burn less when grid-tied homes are feeding power in, and then burn more later, when such homes are pulling power out.

Now, while being grid-tied is more efficient when viewed system-wide, what would happen if everyone was grid-tied, in a future situation where fossil fuels might be nearly totally phased out? It’s easy enough to see how the grid can work as a virtual (and unlimited) “battery” for a small proportion of customers, but where is the upper limit? The short version—we’re not quite sure. One thing is for sure, though—U.S. power companies are nowhere close to this limit. In Vermont the electric utilities are currently allowed by law to have up to 4% of their generation from grid-tied systems, but that number was established somewhat arbitrarily in years past, and the legislature is currently expected to soon raise it to 15%, a move that is being welcomed by most of the power companies. A better case study of high RE penetration would be the situation in Germany, though it’s complicated enough that the topic really warrants its own post. Short version—their solar feed-in is around 35% on sunny days, and due to vagaries in the international coal market (coal has become cheaper due to plentiful supplies of natural gas in the U.S.) it has caused disruption in the business models of German power companies, which has had economic costs and, as of yet, fewer than expected CO2 reductions (see Economist article, “How to Lose Half a Trillion Euros“. I personally think The Economist is quite one-sided in this article, but that, again, would probably be a whole other post.) Eventually grids worldwide will need to move toward 100% RE generation as we phase out fossil fuels, and much of this will be distributed generation from point sources. But, 1) we’re not even close enough to worry about it now, at least in the U.S., and 2) power companies will change their business models over time. Indeed, companies like GMP have already started. Fortunately, moving to a smarter grid isn’t an all-or-nothing propostion, but rather evolutionary change over time. (Again, previous post “Cloudy Day Pause” discusses some of this in more detail).

So, back to where I started—it isn’t sexy, but the higher efficiency of grid-tied systems is an important point as we work out our workable vision of the future. We’ll eventually need a smart, flexible grid that efficiently connects renewable generation from million of sources to millions of destinations. In the much shorter term for me, tying to the grid might be the easiest, if not the cheapest, way to achieve net-zero. Much to ponder…

Top image by La Bastilla Ecolodge/Creative Commons at http://www.flickr.com/photos/75904527@N05/6789926688/in/photolist-bm19Dw-bHQZjr-hgdJBV-bBhSJ4, image has been cropped.
Niagara Falls image credit: pierdelune / 123RF Stock Photo

Cloudy Day Pause

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Gray days to deal with.

Mr. X thinks my vision of a future without nuclear power is “too hard” (“Needed: The Hard Path“). I was all set to write a post arguing about it, but something that’s not too uncommon here has given me pause—a dark and cloudy day. This is because a big part of the entire argument of whether we need nuclear power hinges, for most people, on whether or not we can make enough power from renewable sources. And THAT entire argument hinges on the question of intermittency, which is what the cloudy day reminded me of. Solar arrays can make plenty of power on a sunny day, and wind turbines can make plenty of power on a windy day, but what about all those other times? If we depended entirely on wind and solar and hydroelectric, what would we do on short winter days when the entire East coast might be having a cloudy and windless day? Or worse, a week of such days? If the energy constraints in such a system were dramatic, or if such a system was too difficult to build, it might result in that path that would be “too hard”.

So, Mr. X had a variety of points, but his main ones, including whether or not I was being consistent in my thinking, hinge around this “too hard” piece. In general, there are two broad lines of thinking here-

Line-of-thinking #1—We will need nuclear power as we move toward carbon-free sources, because wind and solar and other renewable sources are intermittent, and we will need nuclear power for baseload power. Or, related, we will need nuclear power as a transitional power source, until we build out enough wind and solar and/or develop grid-scale storage capacity.

Line-of-thinking #2—We can indeed switch over to renewable power, and the intermittency problems can be solved, and the money we would have had to spend developing safer “Gen IV” nuclear power would have been better spent on developing the truly safe and sustainable renewable system that we will need for the long term.

So, who is right? Could we make the system work with just renewable power? After some contemplation, I’ve decided that we probably can, though I admit that it will be difficult, as it will involve some fundamental changes. Some factors that make me lean in this direction—

— I think we need to undergo a paradigm shift with regard to how people expect their electricity to be delivered; the new systems will not just mimic the old. Customers today expect electricity to be generated by the utility and made continually available, in any amount, at a set rate. The system of the future might function dramatically differently from this, with the utility companies buying power from thousands or tens of thousands of producers, aggregating that power, and then making it available at a continually varying spot price. Consumers will be able to monitor this price via smart meters, and will be able to use this information to shift their demand.  And, they will indeed shift their demand, because prices might vary dramatically. (And, because the generation is so dispersed, it will help moderate demands on transmission infrastructure.) This change alone would go a long way toward solving the intermittency problem—we might someday see tremendous electricity consumption during sunny hours, as people choose that time when power is plentiful (and cheap) to charge their EV’s, heat or cool their homes, run their water heaters, run their air conditioners, or, factories choose that time to conduct energy-intensive operations.

— Wind and solar complement each other really well. Germany is a good example of this—the country has 32 gw of installed solar, and about 30 gw of wind. Their solar peaks in spring and summer months, when daily solar production is about eight times higher than in December and January. But wind production is nearly the exact opposite, and the seasonal fluctuations largely balance out. (For a visual of this, see pages 13,14, and 16 of this presentation. It takes half a minute or so to load this page, but worth the wait.) Other factors also help, such as the fact that daily demand peaks in most systems during midday hours, and seasonally during the summer, exactly when solar production peaks.

Kaprun hydro-electric dam, Salzburg, Austria.

Kaprun hydroelectric dam, Salzburg, Austria.

— Hydroelectric power could be held back during the day, when solar power is at its maximum, and used during nighttime hours. In many locations it can even be held back seasonally, if required. Pumped-storage systems are used in similar ways; filled when power is cheap, then used for generation when power is expensive. Other forms of utility-scale storage are being developed at a rapid rate, from compressed air storage in abandoned mines, to grid-scale liquid-metal batteries, to ideas about lifting whole mountains (TEDx Talk here), or putting together used EV battery packs in stationary locations for grid-scale battery storage. In all storage situations, the higher the difference between low and high electricity rates, the more profitable the storage—another prime situation where market-forces will help to solve a problem.

— Roofs everywhere need solar panels, even if they don’t have optimum orientations. Panels facing east and west on rooftops (and not just south) spread solar production more evenly across the course of the day (…though in the Southern Hemisphere they put solar on the northern sides of their roofs).

— The larger the geographic area that is tied together by a smart grid, the easier it is to balance power and loads. Over large areas, solar insolation averages out, as does wind production. DC transmission lines are capable of delivering power for well over 1,000 miles, and such transmission corridors could link the production from the windiest areas in the Midwest and offshore to urban centers where it would be needed, and from the sunniest parts of the country to the less-sunny (see post “This is Interesting…“). Continue reading

This is Interesting…

Power lines--not pretty but necessary.

Power lines–not pretty but necessary.

(slightly technical post)

From time to time I have mentioned DC power transmission lines in my posts, and I was discussing this with Mr. X. We both had a very similar question—why is it that AC power transmission won out over DC, back in the 1880s, and yet today there is this new push to use DC for long-distance transmission? We both had a vague idea, and turns out we were both right, but I read more about it, and the details are quite interesting.

Short version—back in the 19th century, Thomas Edison was pushing for the development of a DC grid system, and George Westinghouse and Nikola Tesla were pushing for an AC grid system. Due to one basic fact, the AC system won out over time—it was easier to transform AC current into high voltages, and high voltages suffer exponentially lower losses during long-distance transmission. A simple transformer with a different number of windings on the two sides will step AC current up or down quite efficiently, but to change DC from one voltage to another essentially required the DC current to power an electric motor, the output of which drove another generator which was wound to produce DC output at a different voltage. Losses were higher, and these DC systems, with their moving parts, had much higher maintenance costs. So the AC systems won out, and became standard the world over. Simply put, systems needed high voltages for transmission, and much lower voltages for actual use for power or light, and this was only practical at the time with alternating current.

In all actuality, though, once DC current has been stepped up to those higher voltages, it is actually the more efficient of the two for long distance transmission. This is due to two basic characteristics of AC transmission that cause losses. The first is something called the “skin effect”, whereby the outer surface of an AC conductor actually carries the bulk of the current. The effect is significant with higher currents and voltages and larger wires. As you increase wire size, the mass of the wire goes up faster than the surface area, so you get less and less actual capacity gain with bigger wires. Doubling the weight of an AC conductor does not double its current carrying capacity. (They can get around this by using braided wires, but they aren’t practical for lines that are hundreds or thousands of miles in length). The second problem with alternating current is that every time a current is introduced into a wire, it creates a magnetic field. That magnetic field has to be “charged up” as the power begins. Unfortunately with AC, the power “begins” sixty or more times each second. These losses are called capacitance losses, and get worse as the conductors get closer together. In undersea cables, where the conductors are housed essentially side by side, these losses are so high that AC transmission almost doesn’t work, and most undersea transmission cables are built to use DC. But even with overhead line systems capacitance losses are present, and limit the effective range that AC power can be transmitted. In general, it can be transmitted for hundreds of miles, but not thousands.

Fortunately, much has changed since the 19th century—today it is quite possible to change AC to DC, and vice versa, and to transform DC power into different voltages; mechanical devices are no longer required. Long distance, high voltage DC (HVDC) transmission corridors have already been built; there are several in the U.S., quite a few in Europe, and the longest two in the world, both well over 1,000 miles in length, in China and Brazil.

This modern capability is important, because in the sustainable world that we need to move toward electrical power is going to be far more prominent than it is today. Most renewable power systems generate electricity, be they solar, or wind, or hydroelectric. And much of this power generation is NOT produced where it’s needed. (Just one example—the windiest parts of the U.S., the Great Plains, are not where the big cities tend to be.) So, in the future we will use more electricity as we phase out fossil fuels, increasing amounts of that electricity will be from renewable generation, and it will need to be moved long distances. Thus the need for DC transmission.

Image credit: aarrows / 123RF Stock Photo