中国储能网讯：根据美国罗彻斯特理工学院的一个研究小组的调查研究表明，电池储能不一定能帮助电网脱碳。在许多情况下，电池储能还有可能增加煤炭消耗。

由RIT Golisano可持续性研究所的Naga Srujana Goteti领导的研究团队发现，安装在美国大陆中部独立系统运营商（MISO）电网上的电池储能可能会增加煤炭消费量，导致碳排放增加。

这一发现并不令人意外，因为煤炭是MISO电网的主要发电的能源之一。但是在纽约州，煤炭是其发电组合的次要组成部分，如果天然气价格很高，电池储能仍可能导致排放增加。

该研究报告指出：“鉴于当前天然气价格低迷，增加储能量会略微降低纽约州的碳排放量，同时增加美国大陆中部独立系统运营商（MISO）的碳排放量。如果储能部署能够使高排放的发电机（如煤电厂）替代天然气等更洁净的工厂，那么储能部署将会增加碳排放。”

这个研究还研究了碳排放、发电组合和定价之间的复杂关系。

由于研究中的电池在电价下跌时设置为充电，当电力价格上涨时设置为放电，当能源需求低时，它们会增加任何生成电源的消耗。例如，在像MISO这样以煤电为主的电网中，夜间充电时会产生额外的电力需求，即使提供风力发电，燃煤的电力也会大大增加。这种燃煤的电力随后在需求高峰期释放，通常取代低碳天然气。

因此，“以煤电为基础的电网中，即使从可再生能源收取电力，储能部署也会增加排放量。”Goteti说，“除非过量的可再生能源发电正在减少，并且可用于充电。”

而这取决于燃料定价，即使在像纽约州的独立系统运营商管理的电网上，这种情况也可能存在，而在这种电网中，其发电主要是无碳能源。

纽约州的电力只有约3％来自煤炭，这意味着电池储能的排放通常来自于天然气。但如果天然气价格从目前的2.60美元上升到每百万英热单位5美元，将会首先采用煤炭发电，并最终用于储能系统充电，导致整体排放量增加。

研究人员能够粗略地计算出，在电网上需要多少可再生能源才能开始削减排放量。在MISO的电网中，只有风能和太阳能的份额达到18％，储能部署才能保持碳平衡。与纽约州一样，这一水平对天然气价格高度敏感。如果MISO的天然气价格达到每百万英热单位5美元，那么系统运营商需要从可再生能源中获得35％的发电量，然后才能实现碳中和。

该研究评论说，可再生能源发电要达到这种比例可能至少需要10年。

目前，MISO的太阳能发电量可以忽略不计。大约7.6％的运营商电力来自风力发电，另有3.3％来自其他来源的组合，包括水电和生物质能，还有柴油。

报告总结说：“天然气价格的影响不利于储能的经济和环境影响。我们发现储能引发的零排放或负排放取决于目前较低的天然气价格。然而，如果天然气变得更加昂贵，储能部署提供能源套利只会带来经济上的意义，在这种情况下，储能会促使更多地使用煤炭，增加系统排放。”

虽然对于那些假设电池通过采用可再生能源而自动减少排放量的人来说，这项研究可能会让人清醒，但Goteti和她的同事们也发现，这种情况可能会随着碳税而发生根本变化。

研究报告称：“发电机排放的碳排放价格将转变运营模式，即使在当前的风能和太阳能能源情况下，储能部署也能保持碳中性。”

调研机构GTM Research公司高级能源存储分析师Daniel Finn-Foley说：“这取决于企业为什么要安装储能系统。如果在MISO的电网添加储能，那么其目标是为了实现收入最大化，而不是限制温室气体减排。运行储能系统以提供另一种经济效益较低的服务，例如捕获受限的风力或将太阳能转换到峰值时段发电，将产生不同的结果。”

去年1月，研究人员发现，如果不直接与可再生能源配套使用，家用电池储能系统可能成为一个重要的碳排放源。（中国储能网独家编译，转载请注明来源）

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.