GE creates ‘sunrotor’ system to store, generate clean energy

GE 希望利用 CO2 廢氣配合太陽能來發電

Eric Chan , @erichankc  https://chinese.engadget.com/2016/03/10/co2-solar-batteries-general-electric

有兩個問題纏繞著環境科學家多個世紀，一是如何把太陽能電力儲存；二是如何處理因為燃燒碳而產生的 CO2。通用電氣（GE）的科學家想到了一個一石二鳥的方法，就是利用 CO2 作為巨型電池來儲存多餘電力。做法類似在加州的 Ivanpah 太陽能發電廠，利用鏡子集中反射太陽熱力至中央的鹽（GE 未有指出是哪種類的鹽）。同時，CO2 將會在地下儲存，把多餘的能源以固體乾冰的狀態儲存。 當在用電量高峰的時候，電廠就能利用燒熱的晶體把固態的 CO2 加熱至「超臨界（supercritical）」的狀態。這些介乎氣態與固態之間的 CO2 就能用作推動渦輪機發機。下圖所示的 Sunrotor 原型模型，在 GE 把它正式建造出來後，據稱將能為 100,000 戶家庭提供電力。

這設計還能為燃氣發電廠減少熱散、提升效率。GE 的資深工程師 Stephen Sanborn 的說法，系統可提升一倍的產量，並把現在每生產 1 兆瓦時電力的成本由 250 美元減至 100 美元。能這樣大幅降低成本，是因為他們不再是「製造」能源，而是從太陽或渦輪的排氣中提取能源，並把它們儲存和轉化使用。除此之外，新系統的能源轉換率更比燃氣的 61% 提高至 68%。

可是因為這套系統非常複雜，而且需要冷藏、熱傳導、能源儲存和化學工程方面的專才，幸好 GE 內部也集齊了相關領域的研究人員才能成事。短期內，這技術將能透過減少廢氣排放而為燃氣電廠提升 25% 至 50％ 的效率，並大幅減少 CO2 的排放。而 Sanborn 則預計系統最快可在 5 至 10 年內投入商用，最終的目標是透過達成一套高效率、高效能的可再生能源系統，減少對化石燃料產電的依賴。  

               

2016 年 3 月 10 日GE creates ‘sunrotor’ system to store, generate clean energy

Brittany A. Roston - Mar 9, 2016  

https://www.slashgear.com/ge-creates-sunrotor-system-to-store-generate-clean-energy-09430845/

 A solar thermal power concentrates heat from the sun to boil water and use the steam to generate electricity. Image credit: Getty Images 

GE researchers have developed a new technology that uses CO2 to generate a substantial amount of clean energy, and it doubles as an energy storage solution for solar panels. CO2, of course, is one big cause of climate change, and the irony isn’t lost on GE. By using the technology, solar storage and clean energy could be made more efficient while simultaneously reducing the amount of fossil fuels needed to power homes and dealing with harmful CO2 pollution wrecking the environment.

In a statement on Tuesday, GE detailed the work of Stephen Sanborn, a senior engineer with GE Global Research and the principal investigator for this project. The issue concerns energy demands that come at times when solar is not ideal, and presents a way to store surplus energy when the weather is more than ideal. During the long dark days of winter, for example, having a surplus of energy is necessary to meet demand. During the bright, long days of summer, solar arrays may generate more electricity than current technologies can adequately store.

A life-size prototype of GE’s “sunrotor” on a shelf at GRC. This 10 megawatt prototype is the basis for the full-scale system which stores 100 megawatt-hours and generates power at 33 megawatt, Sanborn says. Image credit: GE Global Research


The solution could be the contraption you see above, a so-called ‘sunrotor’ that functions as a CO2 turbine based on the company’s own steam turbine design. Rather than using steam, though, the sunrotor uses CO2 that is heated from its dry ice stage into a supercritical fluid using molten salt. This particular prototype is able to generate 100megawatts of electricity.

The storage part comes from how the system deals with the CO2 — in this case, solar heat is stored in molten salt, and extra electricity is used to cool CO2 into dry ice. When more electricity is needed than the system is able to provide in that moment, the salt is then used to warm up the dry ice, powering the sunrotor and generating electricity to fill in the gap.

Adding the system to existing solar setups would be simple, according to GE; right now, researchers are focusing on the bringing the cost-per-megawatt down to $100.

General Electric has been increasingly working toward a more green future, and to that end it recently announced plans to focus solely on LED bulbs in the U.S., ditching CFLs 慳電膽 and the problems they present. The time is right, GE had said, as the technology has improved while costs have come down substantially. Though an LED bulb is usually still more expensive than a CFL bulb, they last much longer and, as one example, illuminate at full brightness instantly rather than taking a few minutes to warm up.

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GE原文: https://www.ge.com/reports/this-scientist-has-turned-the-tables-on-greenhouse-gas-using-co2-to-generate-electricity/

Tables On Greenhouse Gas, Using CO2 To Generate Electricity

Mar 7, 2016 by Mark Egan

Solar power is a great source of renewable energy, but as with many things in life, timing is everything. The sun doesn’t shine on long winter nights when people turn on their lights. On the other hand, a sunny Sunday afternoon can produce an ample electricity surplus that’s difficult to store.

“That’s the grand challenge,” says Stephen Sanborn, senior engineer and principal investigator at GE Global Research (GRC). “We need to make renewable energy available to the grid when it is needed.”

Sanborn and his team decided to solve this problem by storing some of the heat generated by thermal solar power plants in carbon dioxide. These power plants concentrate solar rays with vast fields of mirrors and use the heat to generate steam that spins a turbine. The carbon dioxide effectively works like a battery that can quickly release energy during peak demand.

The irony, of course, is that CO2 is the prime contributor to climate change, and the reason the world is switching to renewable energy in the first place.

The work is part of a research partnership between the GRC and the U.S. Department of Energy. Sanborn says the solution could revolutionize the solar power industry and also make natural-gas power plants more efficient.Here’s how it works. The design has two main parts. The first one collects heat energy from the sun and stores it in a liquid of molten salt. “This is the hot side of the solution,” Sanborn says. The other component uses surplus electricity from the grid to cool a pool of liquid CO2 so that it becomes dry ice.

During power generation, the salt releases the heat to expand the cold CO2 into a supercritical fluid, a state of matter where it no longer has specific liquid and gas phases. It allows engineers to make the system more efficient.

The supercritical fluid will flow into an innovative CO2 turbine called the sunrotor, which is based on a GE steam turbine design. Although the turbine can fit on an office shelf (see image above) it can generate as much as 100 megawatts of “fast electricity” per installed unit—enough to power 100,000 U.S. homes.

Sanborn believes that a large-scale deployment of the design would be able to store “significant amounts” of power —— and deliver it back to the grid when needed. “We’re not talking about three car batteries here,” he says. “The result is a high-efficiency, high-performance renewable energy system that will reduce the use of fossil fuels for power generation.”

He says the system could be easily connected to a solar power system or a typical gas turbine. The tanks and generators could fit on trailers  拖車. His goal is to bring the cost to $100 per megawatt-hour, way down from the $250 it costs to produce the same amount in a gas-fired power plant. “It is so cheap because you are not making the energy, you are taking the energy from the sun or the turbine exhaust, storing it and transferring it,” says Sanborn.

The process is also highly efficient, Sanborn says, yielding as much as 68 percent of the stored energy back to the grid. The most efficient gas power plants yield 61 percent.

The team is now building a conceptual design, which Sanborn believes could take five to 10 years to get from concept to market.

GE is also looking at other commercial applications that could be made available sooner. One such utilizes the waste exhaust heat from a natural gas generator. Sanborn says the solution could make gas-fired power plants 25 to 50 percent more efficient. That, he says, would be a major environmental benefit, because it would significantly reduce the overall CO2 emissions per kW hour of electricity produced by gas-powered plants.

Sanborn’s included in his team turbine experts, thermal engineers who understand refrigeration, heat-transfer scientists, chemical engineers who know how CO2 behaves and energy-storage experts. “We call all this expertise we have at our fingertips the GE Store,” he says. “It would be very difficult for me to do everything that this research calls for without that deep expertise of people available at GE.”