Power Sharing: The Basics of Distributed Generation

[peristaltor]

Very few news or opinion pieces concerning the future of our electrical grid seem nowadays to lack a nice picture or two like those above and below these words.



What makes these two technologies possible, however, often eludes the corresponding press pieces, perhaps because even the reporters writing the stories fail to appreciate the beauty and promise of distributed generation.

To understand what is possible, it is first important to understand how the grid delivers electricity to users today. Head over to this animated page put together by the California Energy Commission. In the animation, the power flows from the central power plant, through high-tension power lines to a receiving station, through distribution substations, substations, and finally reaches the commercial and residential consumers. This seems simple enough. Most everyone has been to the mountains and witnessed how rain and snow flow into creeks and rivers to downstream consumers and lakes and seas. Applying this familiar downward flow model to electricity helps most everyone understand how the grid must work, right?

Well, sort of. Power does indeed flow from power plants to your computer at home. It is not impelled there like water tumbling down a mountain stream, though, by gravity. Rather, the power plant creates a positive build-up of electrons which seeks a place to go. Think of a water main fed by an elevated water tower branching to smaller and smaller pipes, finally pouring from your garden hose at 60 psi (pounds of pressure per square inch, the most common). Have you ever wondered what would happen if you connected your garden hose to a pump and forced water at a slightly higher pressure into the garden nozzle? Very likely. . . not much. If you flushed your toilet or ran your kitchen sink, however, there's a good chance the water from that outside pump would find its way up your pipes to those outlets.

Which leads me to solar panels and wind turbines. Prep the power coming from these and other electrical generators properly, and the power from them runs up the power line. How far up that line it travels depends only on the location of the closest operating electrical device.

For a moment, head back to that animation. Note the last home on the residential power line, the last little icon to get a pair of blue dots of power.

Now imagine smaller dots leaving that home. . . and on the way out perhaps making the last home's power meter spin backwards.

Power flowing from homes and businesses toward the nearest electrical user: That's distributed generation.

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Before I dive into DG, let me apologize to those who might already know about the DG phenomenon. I'm treating this post as a primer. Why? Simple. Live Journal has millions of active users. . . yet check out this screenshot:



The only reason I am not all alone in listing this interest lies in the fact that the home_effinomic community also lists the interest. It's not a large community at all. I should know. I started it. Other synonyms of "distributed generation" prove almost as empty. "Distributed energy" is an interest unique to me. As I write this entry, only two others on all of LJ list "distributed power." Based on this evidence, I'm writing today in primer mode, sharing what non-expert knowledge I've gleaned over the years as simply as I can.

Next, let me introduce and define a few basic terms.

Renewable Energy Source: A device or process that converts one energy source (ie. sunshine or wind) without needing additional fuels. Though this definition might seem obvious, there are a few promising technologies that force interesting considerations. I'll hopefully discuss these considerations late.

Grid Intertie: Any device or configuration that allows electrical power to flow into the grid. Solar panels and wind turbines, for example, often produce low-voltage direct current electricity that must be modified before it is connected to the alternating current of the grid. This modification (most often performed by an inverter) and connection comprises the grid intertie.

Cogeneration: Simultaneously generating two or more forms of energy, usually heat and electricity. Consider an automobile's engine that burns fuel to produce rotational power (torque) and captures some of the waste heat to warm the passenger compartment and defrost the windows.

For the most part, these three definitions will get us through the bread-and-butter of DG, allowing us to later delve into the meat and potatoes.

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We'll start with the first two definitions and apply them to the typical grid-connected house. Let's start with a house owned by a good friend of mine. He and his family live in Northern California. Recently he installed 5 Kilowatts worth of solar panels on his garage roof. These panels turn the sun's rays into a maximum of five thousand watts of direct current electricity; the inverter converts the power and ties it into the grid, feeding the power to whatever nearby hungry electrical load happens to be on, most likely in his house or in the neighborhood. He hasn't yet given me a run-down on how much power the panels are producing, but noted that since he installed the system last January they seem to have offset 3/5th of his household load. He should see more of an offset as the summer progresses; if he and the family manage to reduce the amount of grid power they consume, they might very well manage to see a monthly bill with credits rather than an amount due!

From a renewable resource captured, converted and made available through a grid intertie, let's look at cogeneration, less common but no less exciting. Let's say you run a municipal swimming pool. The pool uses natural gas for heat already. Why not replace the standard natural gas pool heater with a high-heat exhaust engine? A YMCA pool in California did just that, running a Capstone Microturbine power supply system. The microturbine is essentially a small jet engine that can burn just about anything, including natural gas. Whenever the turbine runs to heat the pool, the rotational power of the turbine also runs a small generator tied into the grid. The Y uses just the same amount of natural gas as they did before, but now becomes a power producer every time there's water to warm, thereby offsetting their significant electrical bills!



That's just one way of achieving cogen. I recently learned about another I find even more exciting. Instead of running an engine to generate electricity and capturing the exhaust heat, why not just convert the exhaust heat almost directly into electricity? The Baxi Ecogen on-demand water heater does just that, using a power-generating Stirling engine to produce electricity every time hot water is produced. Why is this more exciting than the microturbines, you ask? Simple. I doubt I -- or just about anyone else I know -- will ever find a place in the home for a microturbine; but we all need and use hot water.

I'll throw just one more cogen example into the mix. Right now, the hybrid drive Toyota Prius is all the transportation rage. One gets the advantages of an electric drive -- high efficiency, regenerative braking that recaptures energy usually lost -- along with the universality of a gasoline engine. Don't fool yourself, though: the Prius is not an electric vehicle. It is a one hundred percent pure gasoline powered car. The electric drive components all derive their power from the gasoline engine. As an accurate rule of thumb, remember: If you can't plug it in, it ain't electric. Looming on the horizon, though, is a simple yet radical improvement to the Prius' design: the plug-in hybrid. Need to travel just a few miles? Do so in electric mode, then plug the car in afterwards. Need to drive farther? Go as far as you can on the battery power, then allow the gasoline engine to take over for the rest.

Though no plug-in hybrid is currently available (and may never be in the United States), the current fuels crisis might just prompt an automaker to ignore the pleadings of their legal department and take a chance. This possibility opens yet another exciting possibility in improving the electrical grid, one few even contemplate. I'll talk a bit about that later.

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Now, let's hear energy expert Matthew Simmons note a couple of faults in today's electrical grid in an interview he gave just four days after the August, 2003 East Coast blackout commonly referred to as Black Thursday:

Simmons: On a large scale what happened was deregulation. Deregulation destroyed excess capacity. Under deregulation, excess capacity was labeled as "massive glut" and removed from the system to cut costs and increase profits. Experience has taught us that weather is the chief culprit in events like this. The system needs to be designed for a 100-year cyclical event of peak demand. If you don't prepare for this, you are asking for a massive blackout. New plants generally aren't built unless they are mandated, and free markets don't make investments that give one percent returns. There was also no investment in new transmission lines.

Underlying all this is the fact that we have no idea how to store electricity. And every aspect of carrying capacity, from generators, to transmission lines, to the lines to and inside your house, has a rated capacity of x. When you exceed x, the lines melt. That's why we have fuse boxes and why power grids shut down. So we have now created a vicious cyclicality that progresses over time. (Emphasis mine.)

So we have no way to store ac grid power, and have all but reached the limit of the grid's transmission capacity. Bad news on hot days, as Simmons noted, since in hot conditions the companies running the transmission lines must reduce the amount of power flowing through them. The situation, though, gets worse:

A second major reason is that decisions were made in the 1990s that all new generating plants were to be gas fired. We've had a natural gas summit this year and, as you know, I have been talking for some time about the natural gas cliff we are experiencing. Many thought that this winter would be deadly, and I have to say that it's just a miracle that we have replenished our gas stocks going into the cold months. This winter could have been a major disaster. We've seen a price collapse in natural gas to the five to eight dollar range (per thousand cubic feet) and the only reason that happened was throughout almost the entire summer there were only a handful of days when the temperature rose above eighty degrees anywhere. That was miraculous. It allowed us to prepare for the winter but we shouldn't be optimistic. One good hurricane that disrupts production, one blazing heat wave, one freezing winter after that and we're out of solutions. (Emphasis, again, mine.)

So, according to Simmons our excess electrical generating capacity is directly tied to the availability of natural gas. Great. That means whenever it gets either hot or cold outside, natural gas is burned in amounts that stresses the supply chain. A few years back we had natural gas brownouts, a bit of a wake-up call for many. The solution? To increase the capacity of the delivery pipelines. That solved the regional supply issue at the end of smaller diameter pipelines, but what of the supply itself? That situation is growing grave, as Simmons noted. To repeat, "One good hurricane that disrupts production, one blazing heat wave, one freezing winter after that and we're out of solutions."

Out of solutions. Under the current regime of production-to-consumer, Simmons is absolutely right. Let's see, though, what happens when we implement distributed generation on even a slightly larger scale.

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Every time you turn on a light or run some hot water, you use power. Let's say, though, that 5% of the homes in your electrical utility's service area have installed a small solar system. Let's further say the average output on a sunny day from each system works out to 2 Kilowatts, two thousand watts of power per household the utility no longer has to provide when the sun shines.

That isn't much. My electric water heater draws 4,500 watts when it kicks on, 6,500 watts if we use an especially egregious amount of hot water at a time, say, when we have out of town guests lining up for morning showers. And that's just the hot water. What of the microwave (1,500 watts), the stove, oven and clothes dryer? I've been trying for a while now to determine how much power those last three use, but to no avail. Just judging by the size of the electrical elements, all three make the hot water heater look positively wimpy; I guess it's a good thing those appliances are used only a fraction of the time the water heater is. And in terms of average electrical draws in the typical household, the nearly constantly operating refridgerator puts the act of cooling food in a close second with the water heater.

Still, 2 Kw. Per house. It's a start.

Next, let's replace some of those natural gas and electric water heaters with the new-fangled Baxi Ecogen I mentioned earlier. For those replacing a natural gas heater, all that has changed is the efficiency; one of the biggest losses in a tank type heater's operation is the line loss, the amount of pipe the water has to heat before hot water arrives at the spigot. In our house, for example, we have to run one and a half gallons of water through the bathtub spigot before the water is hot enough to use for a shower. With a tankless heater system, we would likely have to install two Ecogens, one on each side of the house. It would be cheaper than relocating the bathroom with a remodel.

So, along with our modest photovoltaic system, every time we turn the H handles, we pump up to 1,000 watts of power into the grid. I usually take a five minute shower. That's five minutes of 1,000 watt power I'm delivering to my appliances and to those run by my neighbors. More importantly, since I replaced an electric water heater, the benefit compounds: It's up to 6,500 watts my house is not drawing from the grid, for a total offset of 7,500 watts!

Next, let's say I bought a plug-in hybrid with a substantial battery pack. It's parked at the curb, plug inserted, either drawing power for the pack or, if fully charged, just sitting there. One concern many voice is how much stress a significant number of charging cars will put on an already maxed grid. It's a fair question, but one that has a solution. For the next bit of cogen magic, I'd like to introduce everyone to the concept of Vehicle to Grid, or V2G:

Electric-drive vehicles, whether powered by batteries, fuel cells, or gasoline hybrids, have within them the energy source and power electronics capable of producing the 60 Hz AC electricity that powers our homes and offices. When connections are added to allow this electricity to flow from cars to power lines, we call it "vehicle to grid" power, or V2G. Cars pack a lot of power. One typical electric-drive vehicle can put out over 10kW, the average draw of 10 houses. The key to realizing economic value from V2G is precise timing of its grid power production to fit within driving requirments while meeting the time-critical power "dispatch" of the electric distribution system. (Emphasis mine, yet again.)

Meaning the flow of power can go from this:



To this:



Check this page out for a Quicktime movie demonstrating the concept. Next, let's note that the demonstration in the movie used a battery-only electric car, not a hybrid. Adding the gasoline or diesel power plant means the electric power deliverable to the grid is limited only by the amount of fuel in the tank. From AC Propulsion, the folks who developed the concept and sell equipment to make it happen, here's a quick summary:

As cars and light trucks begin a transition to electric propulsion, powered by batteries, engines, or fuel cells, there is potential for a synergistic connection between such vehicles and the electric power grid. The aggregate power rating of the US vehicle fleet is much larger than the total US generating capacity. If even a small fraction of vehicles could be harnessed as generating assets, benefits would accrue both to the electric power grid and to the vehicle owners. The potential exists for the economic value generated to significantly offset the costs of electric, hybrid, and fuel cell vehicles.

Let's get back to the blackout. Rather than just being a drain on the grid, every car plugged in could be an asset in times of extreme load, either cutting back on their charging rate or actually providing a burst of power to bolster the load. This would require a wireless market system. The car owners would input their needs, such as how much power in the battery pack or gas tank they need to get home, how much it costs in fuel to generate a kilowatt/hour of power, the current price of fuel and the rate at which they are willing to sell the power. In times of high demand, the power company would wirelessly put out a call: "We'll pay your account $X per kilowatt that all cars in (some) area can provide for the next hour." All cars that are willing and authorized by their owners to provide the power will answer the call, exactly like a trading floor at the stock market. If the utility needs more power, they raise the amount until the market price of power at that moment is reached.


The system would work like this,
only automated.

It may surprise some to learn that this is exactly how the grid works today. The utility puts out a call not to plugged-in cars, but to power plants large and small. If you haven't already, do see Enron: The Smartest Guys In The Room, and learn how Enron's manipulations of the power market led to all the problems.

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With the promise distributed generation supposedly offers, why isn't everyone doing it?

Excellent question. The answer comes in two parts.

First, the technology to make small-scale DG both effective and safe is fairly new. Only thirty years ago, not many inverters on the market could safely convert solar panel output to grid power, and those that were available were expensive. Those that wanted to feed homebrewed power back to the grid had to manually watch a variety of factors to make sure the power didn't damage the grid or create unsafe situations. Microprocessors that do this automatically have fallen in price and risen in efficiency, making grid intertie possible and affordable for just about all.

This emergence has caught many by surprise, which leads us to our second barrier to universal adoption: Money.

Let's go way up the page and return to my friend from Los Gatos and his new solar installation. He wrote me with some answers to questions I had about his system:

Yes, PG&E (Pacific Gas & Electric, his power utility) does pay us back, just do not (yet) know the rate. It is pretty much always sending power back between 9 AM and 5 PM. . . . There is some kind of end of year settlement, but it does not roll over and credits must be used or lost...again not sure on that. I think in a couple of months we are going to see a big dif.

Let's translate a bit of that. The "settlement" he referred to was the yearly tally of what their house used and how much solar power they provided. If in a month they provided more power than they used, they get not cash, but "credits," meaning they must keep track of the power use. You see, most all households that have a solar system are limited. They must never provide more than, say, 1.5 times the amount of power they use. If they do, they automatically become a utility and are regulated under very different rules. If my friend loses credits, the amount they can provide next year is reduced, meaning they could very well be put into the utility category if they're not careful. Some households actually have hot tub parties at the end of the year to make sure they waste enough power to keep their current limits. It seems counter-productive, but that's what happens under the rules.

Why all the Byzantine regulation? In a nutshell PG&E was not formed as a conduit for moving solar power, but as a business. They provide the power, you pay for it. If you provide power to them, they must pay you what they charge. They are required to do this by law. They are not required, however, to make your installation profitable. They are required by the bylaws governing PG&E, however, to make PG&E profitable.

In fact, two weeks after my friend sent me the above email, he sent an update with this link and a note informing me he was pushed to the E6 rate.

From the linked site:

PG&E is a utility. A business. I don’t have a problem with them trying to stay profitable, but don’t outright lie about how the new “solar friendly” E6 schedule is better for solar customers than the E7 schedule you’re dropping. They don’t overtly say that exact sentence, they just imply it exceedingly CONVINCINGLY the general public who has no idea (I’ve studied power rates for hours and even I’M fuzzy…), that it’s in their best interest. It’s not.

It’s designed to save them money from the growing number of solar installations that are going down because of the juicey California Solar Initiative. I wish they’d just tell it like it is.

This new E6 rate essentially limits the amount PG&E have to pay per kilowatt/hour, meaning the time my friend need to make any return on his financial investment just increased. In fact, it probably doubled. Quite simply, he feels he did the right thing and got screwed.

Browsing through the Solar Power Rocks website, in fact, shows in great detail why more people aren't jumping on the photovoltaic bandwagon. Each state has its own set of regulations. Each utility in each state has the right to interpret those regulations. An installation in one area might return an investment; in another, it might be illegal even to think about a solar grid intertie. Such a Balkanized situation discourages businesses to invest.

It gets worse. Solar isn't the only DG option. I heard a story on Morning Edition the other day which described a company capturing waste heat from an industrial process known as coking, and using that heat to run a power plant. It seems a no-brainer, using otherwise lost heat for something useful. Denmark gets half of its electricity from such reclamations. Why don't more in the US do this?

In many areas, according to the story, it's illegal.

That's right. Laws have been drafted to protect power companies from competition, never mind that the competition proves a benefit to the economy, the electrical grid and to society at large.

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So what do we do? Where do we go from here?

Really, there's no need to embrace individual technologies like the Ecogen. More importantly, we need to consider how to modify economic policies and make DG not just a goal, but for individuals running businesses and homes a profitable goal. The technologies will follow the money.

For example, Germany has a simple program to encourage solar installations. Through a national program funded by taxes on conventional fuels, the government pays solar power installers the equivalent of $.50 per KwHr for their power for 20 years. The program was established (IIRC) in 1999, and was designed to get the country to 20% solar by 2020. It has worked far better than anyone could have projected; currently the country might just reach 30% by that target year.

By contrast, in California my friend gets bumped to the E6 rate. Here in Washington, the solar incentive program expires in 2014. It might be renewed, and it might not.

Denmark has a wind incentive program, and is now the world's largest wind turbine producing country. By contrast, the US wind incentives were cancelled four times in a ten year period, essentially crushing the US dominance in the field.

At one time, California seemed a promised land, with new electric cars being tested on the road. The drivers loved them. The waiting list to get one proved extensive. Only half of the people who applied for these cars -- and were approved to get them -- actually got them. A few years later, we saw this:



The leases for (in this pictured case) the GM EV-1 cars were cancelled without hope of renewal. The cars were loaded onto trucks and driven to the Arizona desert, where they were crushed. Like the waste heat from a coking plant, like the energy from the roof of some guy's garage, the EV-1 and other promising technologies proved too promising. . . promising to negatively affect the bottom line for someone with a lot to lose.

We will see little progress -- if any -- until regulators start to regulate not with an eye to protecting the profits of individual players in the energy market, but to protecting the freedom of the market itself. That way, we can all contribute to the mix of electricity in ways that make the grid more robust, thus making it more reliant and useful for everyone.


X-Posted to home_effinomic.