The Crescent Dunes Concentrated Solar Power plant 200 miles northwest of Las Vegas in Tonopah is now coming online. Unlike photovoltaic, CSP solar plants can store energy and thus generate power at night. 10,347 tracking mirrors, each about the size of a billboard, reflect the sun’s heat to the Crescent Dunes central tower to heat molten salt which powers turbines. The molten salt can also be stored and used to power the turbines for ten hours at full load at night. Thus, so long as the sun has shone that day in the Nevada desert, which it usually has, Crescent Dunes can produce electricity at night.
The Tonopah plant is next-gen CSP. Dry cooling technology minimizes water use, since the water is in a closed system, converted to steam then back to water over and over. Other CSP plants can store power, however none can do it as for as long as Crescent Dunes. This could be a game changer.
The facility still isn’t fully operational, but Painter said it is now in the final stages of startup. By early next year, he expects it to be delivering full power to NV Energy, which has agreed to buy the plant’s entire load at 13.5 cents per kilowatt hour — roughly twice the cost of power from a natural-gas fueled plant — for 25 years.
“We’re stepping through territory that’s never been stepped through,” Painter said. “We’re just being very cautious of how we bring it online.”
Solar Reserve, based in Santa Monica, explains how their molten salt system works.
Molten salt is circulated through highly specialized piping in the receiver (heat exchanger) during the day, and held in storage tanks at night – requiring no fossil fuels.
The tanks store the salt at atmospheric pressure.
Use of molten salt for both heat transfer and thermal energy storage minimizes number of storage tanks and salt volumes needed.
Molten salt is stored at 1050F until electricity is needed – day or night, whether or not the sun is shining.
As electricity is needed, molten salt is dispatched from the hot tank through a heat exchanger to create super-heated steam which then powers a conventional steam turbine.
The molten salt never needs replacing or topping up for the entire 30+ year life of the plant.
Heat loss is only 1F per day.
The salt, an environmentally friendly mixture of sodium nitrate and potassium nitrate, is able to be utilized as high grade fertilizer when the plant is eventually decommissioned.
Ripasso Energy concentrated solar power focuses the heat of the sun to highly efficient, zero-emissions Stirling engines. A test site in the Kalahari desert has reliably produced energy for four years and achieved a world record solar-to-grid electricity conversion of 32% and, big added bonus, uses no water, a major concern in deserts. By contrast, traditional solar PV has achieved about 15% usable grid power, while other forms of concentrated solar use water to power steam turbines.
The technology works by using the mirrors as giant lenses that focus the sun’s energy to a tiny hot point, which in turn drives a zero-emission Stirling engine.
The Stirling engine was developed by Reverend Robert Stirling in Edinburgh in 1816 as an alternative to the steam engine. It uses alternate heating and cooling of an enclosed gas to drive pistons, which turn a flywheel.
Ripasso says competing with the ever-dropping costs of solar PV is crucial. Their biggest challenge was getting funding from skeptical banks, so they secured private funding instead. Solar power like this would be an ideal way to power desalination plants on the coasts in deserts, as well as homes.
Concentrating solar power creates electricity by using the heat of the sun. The heat generally is focused to a central tower or stored in tubes next to parabolic troughs, then used to power turbines, creating electricity. Solar PV is way cheaper than CSP. However CSP has a huge advantage that makes it competitive. Excess heat can be stored in molten salt, then used to generate power when the sun isn’t shining or at night. Specifically, CSP can be used as backup power for solar PV when the sun is setting and demand is generally at its highest.
A ginormous CSP plant in Tunisia will generate 2.5 GW, equal to that big coal and nuclear power plants, when built and send the power to Britain via high-voltage DC cable. The builders say the cost will be competitive although Bloomberg New Energy disagrees.
Contrary to Nur Energie’s estimations, Bloomberg New Energy Finance calculates that most solar thermal plants would need a power-purchase agreement in excess of $200 per megawatt-hour to be commercially viable.
This compares to just under $100 per megawatt-hour for PV “in a similar sunny location,” Chase said. “The only reason anyone would give you that premium is if you were supplying power that matched the demand of the grid you were feeding into better than PV does.”
And that is exactly what CSP does, it provides large amounts of power precisely at the time when solar PV can no longer do so. And this is the only reason it remains viable competition.
This is particularly the case in markets such as South Africa, where there is a need to meet evening demand peaks that PV cannot handle. South African regulators have approved at least half a dozen CSP plants with storage.
BLS explains how CSP works.
Although there are several different CSP technologies, they all involve reflecting sunlight onto a focal point that contains a heat-transfer material. The heat-transfer material, usually synthetic oil or molten salt, is collected in a heat storage unit and eventually used to create steam that powers conventional generators. One advantage of CSP is that at night or on extremely cloudy days, the conventional generators can be run on natural gas or petroleum, allowing the plant to continue to generate power when the sun is not shining.
That’s right. CSP is not completely renewable. The turbines can run off carbon fuel too. However, they are still way greener that say, a coal plant.
Electricity is expensive in Philippines, compounded by growing shortages. The government has responded by leasing more power, paying big customers to generate their own power (probably by diesel), yet these seem stopgap measures. With so many islands, distributed energy via rooftop solar could help substantially.
The power profile of the three major island groups is quite different. Visayas and Mindanao get half their power from renewable sources, geothermal and hydro respectively, while Luzon relies heavily on coal. Yet new growth for all three will mainly be coal. (Big hydro is controversial, some think big dams are so damaging they shouldn’t be classified as renewable. Yet, the power does indeed come from a non-carbon source.)
The three main island regions of Luzon, Visayas, and Mindanao each have distinct generation profiles. In the northern part of the country, Luzon’s capacity is mainly powered by fossil fuels, with anticipated capacity additions of more than 500 MW, most of which will be coal-fired. Visayas, in central Philippines, currently relies heavily on its geothermal resources, but has plans to add 300 MW of coal capacity by 2017. In the south, Mindanao relies heavily on its hydropower resources, with plans for both additional hydropower capacity and additional coal-fired generation to increase system reliability.
Their Secretary of Energy says rooftop solar actually cheaper than coal.
“As a simple example, the cost of electricity from a coal plant can run up to P5.50 per kilowatt hour, plus P6.50 for distribution and transmission, which amounts to P12.00. If you install solar panels on your rooftop, you will only spend P9.00 per kilowatt hour for generation and no cost for distribution or transmission. This already saves you up to P3 per kilowatt hour.”
Let’s hope Philippines makes a big push towards rooftop solar.
Renewable energy, especially solar and wind, gets lots of attention, yet it still a tiny part of total power generation worldwide.
Large-scale solar PV grew a startling 40% in 2014, from 21.7 to 35.9 GW, an increase of 14.2 GW in just one year. The US has the most capacity at 9.3 GW, followed by China at 8.5. While this is certainly impressive growth, solar PV is still, globally speaking, a minor player.
In 2012, worldwide installed electricity was 5549 GW, the last year the US Energy Information Agency has data for. Thus, 35 GW is 0.06 of that total, less than 1%. The real percentage would be even smaller than that, since installed electrical has increased since 2012.
The World Coal Association, certainly not an unbiased source, says 41% of world power is generated from coal with the US at 45%.
California is a leader is renewable energy. This image, which is updated daily (PDF), shows how renewables in California are still a relatively small part of the mix. Renewable energy spikes during the day due to solar, then quickly drops off. ‘Imports’ is power coming in from other states. ‘Thermal’ is power from something being burned, specifically coal and natural gas. So, at the daylight peak, renewable energy in California is about 22% of total energy generated. This is impressive (and growing). However most other states (and countries) lag way behind this. this.
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, 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.
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.
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.
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.).