德州因為地區霧霾空污規範以及經濟等因素，未來 5 年內將淘汰 5GW 燃煤發電，這些停役的燃煤發電的發電容量，將幾乎全由太陽能填補，據德州獨立電網德州電力可靠性會議（Electric Reliability Council of Texas，ERCOT）長期系統計畫，接下來 15 年內，德州將新增 14~27GW 太陽能發電容量。
ERCOT 考量未來可能面對各種變化，如極端氣候以及低天然氣價格等共 8 種情況，8 種情況中，新增發電容量幾乎都將由太陽能一力承擔，而以總發電容量來看，主力能源則為燃氣發電，不過部分德州燃氣發電廠將因老舊而屆齡退役，至 2031 年，燃氣發電將佔德州電力供給的將近半數，太陽能則由目前的 3% 提升至 17%，2015 年時，德州在太陽能電池安裝數上於全美排名第 9。風能與其他發電方式佔比則不變。
德州風力發電在中午發電最低，夜間發電較高，而太陽能則在中午發電最高，雙方可發生天然彌補作用，並由太陽能抑低中午用電需求，但傍晚至晚間的用電高峰，將有一小段時間落在日落後太陽能已經不發電，但風能尚未增加的尷尬期間，於晚上 8 點產生一個小的供需突峰，這很容易由反應快速的燃氣發電克服。
近年來德州的備轉容量常常偏低，不過 ERCOT 表示接下來幾年內已經添加足夠的風能、太陽能與燃氣發電容量，將走出備轉容量偏低的陰影。不過，還有另一個考量是，若「潔淨電力法案」（Clean Power Plan）通過，德州將得淘汰 9 吉瓦燃煤發電，而非原本計劃的 5 吉瓦，中間又會產生落差。
而若太陽能比重持續加大，中午可能會發生發電過剩，而傍晚至晚間的供需突峰規模將拉大，造成所謂「鴨形曲線」，但若中午有過剩電力，此問題將可以大量應用能源儲存技術解決，能源儲存價格正持續下降，使之成為直覺的選向，不過 ERCOT 電網有如「大西部」競爭相當混亂，因此廣泛應用能源儲存並未如表面上看來那麼容易。
德州 2 年來引進新的電價機制，在需求上升時提高電價，預期將可促進能源儲存，以及需求反應技術的發展，但德州對推動分散式能源並不積極，分散式能源推動計畫在 2015 年 6 月停擺，因此屆時有可能是大型電力公司發展電網級能源儲存。不過，在新能源技術發展日新月異的情況下，15 年後的解決方案可能今日完全無法想像，或許德州並不需要為了 15 年後的鴨形曲線問題提早杞人憂天。
In the next 15 years, Texas expects to add somewhere between 14 and 27 gigawatts of solar capacity, according to a new long-term system assessmentfrom the state’s grid operator, ERCOT.
ERCOT is considering eight different scenarios, such as continued low natural-gas prices or extreme weather. Under all scenarios, solar makes up nearly all of the new capacity. In all of the scenarios, ERCOT assumes that changes to the U.S. Environmental Protection Agency’s regional haze rule will go into effect. Those changes are expected to make the rule more stringent and impact power producers with emissions that affect air quality.
As more solar energy comes on-line, coal will retire. About 5 gigawatts of coal are expected to go offline in the next five years because of the regional haze rule, according to ERCOT’s assessment. Even without the regional haze rule, some coal will retire anyway.
Natural gas is now the dominant electric generation source in Texas and could see some retirement as well, although the facilities that will retire are mostly older steam units that will be shut down due to age, rather than environmental rules or market conditions.
By 2031, natural gas would make up slightly less than half of the capacity in Texas, while solar jumps from about 3 percent to about 17 percent. Wind, solar and other forms of electricity capacity were expected to stay roughly the same. In 2015, Texas ranked ninth in U.S. PV installations, according to GTM Research.
The drop in coal and increase in solar could bring about something that resembles a duck-curve situation in Texas. The duck curve shows the gap between the total load a utility serves and what that load looks like after wind and solar generation serve some of that load. The duck curve in Texas would look more like a lean duck than the plump sitting duck that California’s grid operator has forecasted.
With considerably more solar, the capacity shortage is expected from about 7 p.m. to 10 p.m. in Texas. But there is one scenario among the eight that could alleviate that: a high-storage scenario.
With falling costs, storage may sound like a no-brainer, but nothing is a no-brainer in ERCOT territory. “ERCOT is like the Wild West,” Randa Stephenson, VP of wholesale markets at Lower Colorado River Authority, said during Bloomberg New Energy Summit earlier this year.
For years, Texas had low reserve margins, but the situation has been looking up lately. ERCOT says it has added on enough new wind, solar and natural gas capacity for the coming years to wade out of dangerous waters when it comes to its reserve margins. Furthermore, the future demand forecast has been lowered overall.
But the beefier capacity margins expected in coming years did not take into account the approximately 6 gigawatts of retirements due to the regional haze rule. The current long-term planning also doesn’t take into account the Clean Power Plan, which has been stayed by the Supreme Court. If the CPP moves ahead, ERCOT has modeled that up to 9 gigawatts of coal could be retired.
There are some other potential factors that could impact more generation or more storage, all of which could address the change in generation mix forecasted in Texas. The state now has a price cap of $9,000 per megawatt-hour when capacity is tight, but it rarely hits that mark.
There is also a relatively new operating demand curve, less than two years old, which is meant to ratchet prices up more as demand increases, but it has been ineffectual so far. It is currently being re-evaluated in hopes of making changes that will allow it to be more effective. Those changes are meant to incentivize new generation or more demand response, although it’s unclear whether they will.
Another change that would incentivize distributed energy resources such as demand response and batteries are the reforms proposed by ERCOT’s Distributed Resource Energy & Ancillaries Market Task Force. The task force was recently disbanded, but there is more work being done to integrate distributed resources into the energy markets.
And it may not be distributed resources that would address a duck curve in Texas given the sloth-like pace of significant market rule changes. Instead, utility-owned energy storage could be a more prevalent solution if it requires less market innovation. Fifteen years is a lifetime in clean energy, however, so the solution to meet the problem in 2030 could look very different from the options today.
Source:http://www.greentechmedia.com/articles/read/solar-will-replace-nearly-all-retiring-coal-in-texas
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