中國儲能網訊：根據美國羅徹斯特理工學院的一個研究小組的調查研究表明，電池儲能不一定能幫助電網脫碳。在許多情況下，電池儲能還有可能增加煤炭消耗。
由RIT Golisano可持續(xù)性研究所的Naga Srujana Goteti領導的研究團隊發(fā)現(xiàn)，安裝在美國大陸中部獨立系統(tǒng)運營商（MISO）電網上的電池儲能可能會增加煤炭消費量，導致碳排放增加。
這一發(fā)現(xiàn)并不令人意外，因為煤炭是MISO電網的主要發(fā)電的能源之一。但是在紐約州，煤炭是其發(fā)電組合的次要組成部分，如果天然氣價格很高，電池儲能仍可能導致排放增加。
該研究報告指出：“鑒于當前天然氣價格低迷，增加儲能量會略微降低紐約州的碳排放量，同時增加美國大陸中部獨立系統(tǒng)運營商（MISO）的碳排放量。如果儲能部署能夠使高排放的發(fā)電機（如煤電廠）替代天然氣等更潔凈的工廠，那么儲能部署將會增加碳排放。”
這個研究還研究了碳排放、發(fā)電組合和定價之間的復雜關系。
由于研究中的電池在電價下跌時設置為充電，當電力價格上漲時設置為放電，當能源需求低時，它們會增加任何生成電源的消耗。例如，在像MISO這樣以煤電為主的電網中，夜間充電時會產生額外的電力需求，即使提供風力發(fā)電，燃煤的電力也會大大增加。這種燃煤的電力隨后在需求高峰期釋放，通常取代低碳天然氣。
因此，“以煤電為基礎的電網中，即使從可再生能源收取電力，儲能部署也會增加排放量?！盙oteti說，“除非過量的可再生能源發(fā)電正在減少，并且可用于充電?！?
而這取決于燃料定價，即使在像紐約州的獨立系統(tǒng)運營商管理的電網上，這種情況也可能存在，而在這種電網中，其發(fā)電主要是無碳能源。
紐約州的電力只有約3％來自煤炭，這意味著電池儲能的排放通常來自于天然氣。但如果天然氣價格從目前的2.60美元上升到每百萬英熱單位5美元，將會首先采用煤炭發(fā)電，并最終用于儲能系統(tǒng)充電，導致整體排放量增加。
研究人員能夠粗略地計算出，在電網上需要多少可再生能源才能開始削減排放量。在MISO的電網中，只有風能和太陽能的份額達到18％，儲能部署才能保持碳平衡。與紐約州一樣，這一水平對天然氣價格高度敏感。如果MISO的天然氣價格達到每百萬英熱單位5美元，那么系統(tǒng)運營商需要從可再生能源中獲得35％的發(fā)電量，然后才能實現(xiàn)碳中和。
該研究評論說，可再生能源發(fā)電要達到這種比例可能至少需要10年。
目前，MISO的太陽能發(fā)電量可以忽略不計。大約7.6％的運營商電力來自風力發(fā)電，另有3.3％來自其他來源的組合，包括水電和生物質能，還有柴油。
報告總結說：“天然氣價格的影響不利于儲能的經濟和環(huán)境影響。我們發(fā)現(xiàn)儲能引發(fā)的零排放或負排放取決于目前較低的天然氣價格。然而，如果天然氣變得更加昂貴，儲能部署提供能源套利只會帶來經濟上的意義，在這種情況下，儲能會促使更多地使用煤炭，增加系統(tǒng)排放?！?
雖然對于那些假設電池通過采用可再生能源而自動減少排放量的人來說，這項研究可能會讓人清醒，但Goteti和她的同事們也發(fā)現(xiàn)，這種情況可能會隨著碳稅而發(fā)生根本變化。
研究報告稱：“發(fā)電機排放的碳排放價格將轉變運營模式，即使在當前的風能和太陽能能源情況下，儲能部署也能保持碳中性?！?
調研機構GTM Research公司高級能源存儲分析師Daniel Finn-Foley說：“這取決于企業(yè)為什么要安裝儲能系統(tǒng)。如果在MISO的電網添加儲能，那么其目標是為了實現(xiàn)收入最大化，而不是限制溫室氣體減排。運行儲能系統(tǒng)以提供另一種經濟效益較低的服務，例如捕獲受限的風力或將太陽能轉換到峰值時段發(fā)電，將產生不同的結果。”
去年1月，研究人員發(fā)現(xiàn)，如果不直接與可再生能源配套使用，家用電池儲能系統(tǒng)可能成為一個重要的碳排放源。（中國儲能網獨家編譯，轉載請注明來源）
原文如下：
Battery Storage Could Boost Coal Consumption
Why batteries on their own won’t necessarily slash carbon emissions.
Jason Deign February 26, 2018
Researchers warn about use of batteries without renewables.
More research shows that batteries aren't necessarily helping decarbonize the grid. In many cases, according to a team from the Rochester Institute of Technology, batteries are making it dirtier.
The team, led by Naga Srujana Goteti of RIT’s Golisano Institute for Sustainability, found batteries installed on the Midcontinent Independent System Operator (MISO) grid led to a net increase in carbon emissions, by increasing coal consumption.
The finding is not entirely surprising, since coal is one of the major generation sources on the MISO grid. But in New York, where coal is a minor component of the generation mix, batteries could still result in increased emissions if gas prices are high.
“With current low natural-gas prices, adding storage slightly reduces carbon emissions in New York, while increasing them in the Midcontinent ISO,” states the study.
“Storage increases carbon emissions when it enables a high-emissions generator, such as a coal plant, to substitute for a cleaner plant, such as natural gas.”
The study unpacks the complex relationship between emissions, generation mixes and pricing.
Because the batteries under study are set up to charge when electricity prices fall and discharge when the price rises, they increase consumption of whatever generation source is in use when energy demand is low.
In a coal-based grid such as MISO, for example, charging batteries at night creates extra electricity demand that will mostly be met by coal generation even if the wind is blowing.
This coal-based energy then gets released during peak demand periods, often displacing lower-carbon natural gas.
As a result, “in a coal-based grid, storage increases emissions even if you charge from renewables,” Goteti said, unless excess renewable generation is being curtailed and can be used for charging instead.
Depending on fuel pricing, this can hold true even on a grid like that managed by the New York Independent System Operator, where generation is predominantly carbon-free.
Only about 3 percent of New York’s electricity comes from coal, which means emissions from battery storage are usually a result of charging on natural gas.
But if the price of gas were to go up to $5 per million Btu, from the $2.60 level at the time of the study, coal would be dispatched first and could end up being used for battery-charging, leading to increased emissions overall.
The researchers were able to calculate roughly how much renewable energy would be needed on a grid for batteries to start cutting emissions. In MISO, storage would not be carbon-neutral until the share of wind and solar reached 18 percent.
As with New York, this level is highly sensitive to the price of natural gas. If gas were to go up to $5 per million Btu in MISO, the system operator would need to get 35 percent of its generation from renewables before storage could become carbon-neutral.
Such a percentage of renewable generation is likely to be at least a decade away, the study commented.
Currently, MISO has a negligible amount of solar generation; around 7.6 percent of the operator’s electricity comes from wind and a further 3.3 percent comes from a mix of other sources, including hydro and biomass but also diesel.
“The effect of natural-gas price leaves the economic and environmental effects of storage at odds,” concludes the report. “We have found that storage-induced emissions that are zero or negative depend on the currently-low natural gas prices.
“However, storage providing energy arbitrage only makes financial sense if natural gas becomes more expensive, in which case energy storage will induce greater use of coal generation, increasing system emissions.”
While the research may be sobering for those who assume batteries automatically cut emissions by mopping up renewable generation, Goteti and her colleagues also discovered that the picture could change radically with carbon taxes.
“A carbon price on emissions from generators would shift operation to make energy storage carbon-neutral even with current wind and solar capacities,” said the study.
At the end of the day, said Daniel Finn-Foley, senior energy storage analyst at GTM Research, “it depends on why you're installing storage. If you are adding storage in the MISO region then you're aiming to maximize revenue, not limit greenhouse gas emissions reductions.
“Operating storage to provide another less-economic service, such as capturing curtailed wind or shifting solar energy to times of peak use, would yield much different results.”
In January of last year, researchers showed that residential battery storage could be a significant source of emissions if not paired directly with renewable energy.
