Archive | Solar power

California Duck Curve. Too much renewables during day, not enough at night

California Duck Power curve

About 6% of San Diego CA power comes from rooftop solar. Even this relatively small amount of solar power creates serious problems on the grid. Once solar hits 15%, the problems get more pronounced. This is not just blather from utilities resisting change. When it gets dark, utilities have to ramp up other types of power quickly, something which not trivial. The Duck Curve for California for 2015 is moderate, as shown in the image. As more rooftop solar is installed, the curve becomes more pronounced.

More solar is produced during the day when people aren’t home. This production vanishes when they come home, as night falls, precisely when more power is needed. Also, the glut of production during the day can cause prices to be actually less than zero as well as creating grid problems, since the grid must always be in perfect balance between supply and demand.

As in most locales, solar output in California peaks in the naturally sunny middle of the day. But lots of people are at work and there isn’t much demand on the system. SDG&E’s system peaks closer in the evening, when people get home from work and the sun goes down. The drop in solar production almost perfectly coincides with the utility’s daily ramp up to peak demand.

The San Diego utility says solar rooftop users only pay about half of what their solar costs the company. This is probably at least partly true, made worse by a convoluted state-mandated rate structure. Time-of-use rates probably make more sense. Users would pay more for power on a baking hot summer afternoon than on a moderate Spring night. The ability to store power for a few hours would help enormously, however doing so is expensive. Other solutions though, are available now.

Avery imagines a world where your house pre-cools during the off-peak, where your electric water heater delivers demand response during the peak, and your electric vehicle charges based on price signals.

“All these things today are reality. They can happen right now,” he said.

Tesla plans solar-powered home battery storage

Tesla, perhaps to distract from lackluster car sales, just announced plans for battery packs powered by solar panels for residential homes. This is not a new idea. Off-grid homes as well as grid-connected homes with solar panels already have batteries to store energy. So really, why is this news, except that Tesla announced it with great fanfare and says the batteries will look elegant. The amount of hype emanating from Tesla has always made me a bit suspicious.

Working with SolarCity (of which Musk is Chairman) to power the batteries with solar energy just makes the whole endeavor sound like a fantastically Earth-friendly project.

Um, no. Batteries by definition are not earth-friendly at all. They require mining, often in impoverished areas where workers are exploited, use noxious chemicals, and are difficult to dispose of. So don’t go hugging trees quite yet because of the not really green at all Tesla home battery. Is it better than powering your home with coal power? Absolutely. But it’s not green. Batteries probably never can be.

Another problem is the utilities, some of whom are dinosaurs that don’t want to lose revenue because people install solar.

Unregulated batteries to power homes attached to solar panels that keep the battery charged mean some annoyed executives at utilities, especially if the battery’s storage is large enough that it wouldn’t even need much in the way of the electric grid to supplement the solar panels. Not that you’ll ever hear it spelled out so bluntly. Tesla has said that utilities are partners, not enemies, but arguably that just depends on where you look.

Smart utilities, like Green Mountain Energy in Vermont, are leading the move towards home solar. And yes, home batteries do need some regulation. For example, they must never ever send power grid into the grid during a blackout to prevent electric shock to linemen fixing, say, downed power lines, who aren’t expecting power to be coming upstream to them.

Stored power from home solar is a great idea. Let’s hope it becomes ubiquitous soon. For that to happen, the grid will need to be rejiggered to handle distributed energy  flowing from many places to many places rather than the centralized system we have now.

Distributed generation increases electrical grid security

Power Lines

A few well-placed attacks could paralyze the existing US electrical grid, says former FERC Commissioner Jon Wellinghof. The best way to defend against such attacks, he says, is with distributed generation, not bigger walls and increased security. This is precisely where renewable energy, especially rooftop solar, can help.

Wellinghoff believes the true answer to grid security is to fundamentally realign the system from one that relies on a few nodes (probably less than a dozen), which are all critical for the grid to operate, to a national system of ‘distributed grids’; hundreds of smaller ones, which of course could be attacked individually through conventional or nuclear or cyber means, but none of which could topple the entire system if it went down.

Wellinghof focuses on substations as being particularly vulnerable, and they are. However, another area of concern is ginormous transmission towers sited in remote areas, as often happens in the American West. Presumably taking down a couple of those towers would create chaos. However, those towers generally come from huge power plants so again, distributed energy lessens the threat because power can be generated everywhere.

Distributed generation is about moving power generation to within the load centers as opposed to power sources being remotely located from the load centers. This breaks up the centralized node architecture currently in place and disperses the generation across the grid forming micro and sub-regional grids. So if there is an attack on a node it won’t take down that whole area of the grid because there would be those sub-regional and micro-grids that could island themselves within those areas.

If everyone had solar panels on their respective roofs then we could adequately disperse power generation in such a way that it makes nodes practically irrelevant. It is easy to hack into a node and cause it to malfunction but it is basically impossible to hack 10 million solar power systems.

Ivanpah solar power plant generating way less power than expected



The Ivanpah concentrated solar power plant in the California Mojave desert near Primm Nevada is not producing nearly as much electricity as predicted. Natural gas, not the heat of the sun, is being used more than originally projected to power the turbines. CSP works by reflecting the heat of the sun from heliostat mirrors to a central tower to run the turbines. Ivanpah has produced a mere 25% of expected electricity since December 2013 when it began production, a dismal result indeed.

The scale of Ivanpah is much larger than any other CSP plant. The plant operator says the weather wasn’t as sunny as expected. This seems a bogus excuse. Was there really 75% less sunshine than projected?

[Second quarter] sales totaled 133,807 MWh and at an average price of $167.85/MWh that generated $22.46 million in revenue.

That relatively small output, combined with the project’s $2 billion price tag, could no doubt hurt all three Ivanpah owners

Increasingly, CSP is having trouble competing with solar PV. If Ivanpah continues to under-perform, then future CSP plants may not get funded. . Ivanpah was funded by NRG Energy, Google, and BrightSource Energy primarily by using a $1.6 billion federal loan guarantee. If Ivanpah continues to falter and the federal government get stuck with the loan, it’ll seriously affect renewable energy funding going forward.

Another sign of the plant’s early operating woes: In March, the owners sought permission (PDF) to use 60 percent more natural gas in auxiliary boilers than was allowed under the plant’s certification, a request that was approved in August.

Using much more natural gas to produce energy rather than using solar heat as planned could, if it continues, might make Ivanpah not able to qualify as being renewable energy under the California plan for 33% in-state renewable energy by 2020. Plus, it’ll make foes of renewable energy chortle with laughter.

Some CSP plants store excess heat in underground molten salt caverns and thus can product energy when the sun isn’t shining. Inexplicably, Ivanpah doesn’t do this, a decision probably made to save money. In retrospect, this seems short-sighted and may imperil the entire project.

Mandalay Bay in Vegas now has 20 acres of rooftop solar


The Mandalay Bay casino and convention center in Vegas is ginormous. MGM Resorts, who owns it, has installed 21,324 photovoltaic panels on twenty acres of convention center roof. Yes, twenty acres… The 6.4 MW system will provide 20% of power for the center, with an additional 2 MW coming when the convention center is expanded. Well done, MGM.

How big is Mandalay Bay? The main hotel is upscale. Delano, an even-more upscale hotel, is in a separate building. A super-upscale Four Seasons occupies five floors of the main hotel. The casino is 135,000 sq ft, The convention center is 1,000,000 sq ft. An events center has 12,000 seats. There are 30+ restaurants, shopping malls, multiple bars and other venues. Plus, Mandalay Bay connects to Luxor (semi-upscale) and Excalibur (low-end),  which are also owned by MGM.

The project is being done in partnership with NRG Energy. Once it is complete, Mandalay Bay will buy from NRG the solar energy through a Power Purchase Agreement at prices below the peak rates on the traditional NV Energy electrical grid (Based in New Jersey, NRG is also a major partner in the Ivanpah solar plant that opened earlier this year near Primm, Nev.).