混合動力汽車充電關鍵是控制高電壓電池組
綠色革(ge)命(ming)可能(neng)(neng)不久就將(jiang)迎來一場重大勝利。在大規(gui)模的(de)電(dian)能(neng)(neng)成(cheng)為“可儲存”和(he)“便攜式”能(neng)(neng)源之時,能(neng)(neng)量(liang)效(xiao)率(lv)將(jiang)獲得顯著(zhu)改善,而且可再生能(neng)(neng)源的(de)推動工作(zuo)也將(jiang)取得進展。可儲存性和(he)便攜性是液體(ti)燃(ran)料的(de)主要優(you)勢,而通過電(dian)池(chi)系統提(ti)供(gong)的(de)電(dian)力(li)(li)則(ze)擁(yong)有提(ti)供(gong)一種(zhong)可行替代方案(an)的(de)潛力(li)(li)。電(dian)能(neng)(neng)可在幾乎所(suo)有的(de)耗能(neng)(neng)設備中使用,而且,電(dian)能(neng)(neng)也可以從幾乎所(suo)有的(de)可用能(neng)(neng)源來產生。核能(neng)(neng)、太陽能(neng)(neng)、風(feng)能(neng)(neng)、地熱(re)能(neng)(neng)和(he)液體(ti)燃(ran)料(汽油、柴油、乙醇、氫等等)都(dou)能(neng)(neng)很(hen)容易(yi)地轉換成(cheng)電(dian)能(neng)(neng)。因(yin)此,與石油燃(ran)料相比,電(dian)力(li)(li)的(de)重大優(you)勢是可以利用最具成(cheng)本效(xiao)益(yi)的(de)解決方案(an)隨(sui)時隨(sui)地產生能(neng)(neng)量(liang)。
對電(dian)(dian)(dian)能(neng)(neng)(neng)的(de)規(gui)范化可(ke)以同時(shi)實(shi)現規(gui)模經濟,并免除局部燃(ran)料消耗所需(xu)的(de)基(ji)礎(chu)設施。優越(yue)的(de)電(dian)(dian)(dian)能(neng)(neng)(neng)可(ke)儲存(cun)性便(bian)于(yu)發(fa)電(dian)(dian)(dian)(效率(lv)最高,且不是“按需(xu)”型的(de)),目前的(de)情況大(da)體如(ru)此。例如(ru):風力發(fa)電(dian)(dian)(dian)和太陽能(neng)(neng)(neng)發(fa)電(dian)(dian)(dian)未必與(yu)峰值功率(lv)需(xu)求(qiu)模式(shi)相吻合,而可(ke)儲存(cun)特(te)性則(ze)能(neng)(neng)(neng)緩解這個(ge)問題有所緩解。優越(yue)的(de)便(bian)攜性允(yun)許(xu)電(dian)(dian)(dian)能(neng)(neng)(neng)作為汽(qi)車(耗能(neng)(neng)(neng)大(da)戶)的(de)能(neng)(neng)(neng)源。隨著時(shi)間的(de)推移,其他傾向(xiang)于(yu)使用(yong)綠色能(neng)(neng)(neng)源的(de)應用(yong)肯定將得益(yi)于(yu)此項技術(shu)。
電(dian)動汽車對(dui)電(dian)池系統的要求
電(dian)(dian)(dian)(dian)動(dong)(dong)汽車(che)為(wei)(wei)(wei)綠色革命提供了一(yi)個(ge)巨(ju)大的(de)(de)(de)(de)發(fa)展機遇,原因(yin)(yin)有(you)很(hen)多(duo)。電(dian)(dian)(dian)(dian)動(dong)(dong)汽車(che)采用(yong)(yong)電(dian)(dian)(dian)(dian)網(wang)電(dian)(dian)(dian)(dian)力取代了燃(ran)氣動(dong)(dong)力。電(dian)(dian)(dian)(dian)網(wang)電(dian)(dian)(dian)(dian)力的(de)(de)(de)(de)生(sheng)成效(xiao)(xiao)(xiao)率(lv)很(hen)高,可以從幾乎所有(you)的(de)(de)(de)(de)能(neng)(neng)源來獲得。此外,電(dian)(dian)(dian)(dian)動(dong)(dong)汽車(che)的(de)(de)(de)(de)能(neng)(neng)源使用(yong)(yong)效(xiao)(xiao)(xiao)率(lv)也高于(yu)燃(ran)油汽車(che)。大多(duo)數汽車(che)在(zai)運行(xing)時(shi)將經歷一(yi)個(ge)“加速(su)、減速(su)和空轉(zhuan)”的(de)(de)(de)(de)連續周(zhou)期。相比之(zhi)下(xia),易(yi)變的(de)(de)(de)(de)負載(比如加速(su)或減速(su))更有(you)利于(yu)電(dian)(dian)(dian)(dian)動(dong)(dong)馬達(而(er)非燃(ran)油引(yin)擎(qing)),因(yin)(yin)為(wei)(wei)(wei)它(ta)在(zai)低速(su)條(tiao)件(jian)下(xia)提供了高轉(zhuan)矩。燃(ran)油引(yin)擎(qing)的(de)(de)(de)(de)工作效(xiao)(xiao)(xiao)率(lv)只在(zai)一(yi)個(ge)很(hen)窄的(de)(de)(de)(de)速(su)度/負載范圍(wei)內達到最高,而(er)且(qie)為(wei)(wei)(wei)滿足峰值加速(su)的(de)(de)(de)(de)需要,它(ta)必須是超大型(xing)的(de)(de)(de)(de)。用(yong)(yong)于(yu)把汽油能(neng)(neng)量(liang)轉(zhuan)換為(wei)(wei)(wei)動(dong)(dong)能(neng)(neng)的(de)(de)(de)(de)引(yin)擎(qing)效(xiao)(xiao)(xiao)率(lv)通常(chang)為(wei)(wei)(wei) 20%,而(er)電(dian)(dian)(dian)(dian)動(dong)(dong)馬達將電(dian)(dian)(dian)(dian)能(neng)(neng)轉(zhuan)換為(wei)(wei)(wei)動(dong)(dong)能(neng)(neng)的(de)(de)(de)(de)過(guo)程(cheng)中可以實現 90% 的(de)(de)(de)(de)典型(xing)效(xiao)(xiao)(xiao)率(lv)。此外,電(dian)(dian)(dian)(dian)動(dong)(dong)馬達還無須在(zai)停靠時(shi)因(yin)(yin)為(wei)(wei)(wei)空轉(zhuan)而(er)無謂地消耗能(neng)(neng)量(liang),而(er)且(qie)電(dian)(dian)(dian)(dian)動(dong)(dong)系統還具備(bei)通過(guo)再生(sheng)制(zhi)動(dong)(dong)來恢復機械能(neng)(neng)的(de)(de)(de)(de)潛力。通過(guo)電(dian)(dian)(dian)(dian)動(dong)(dong)汽車(che)的(de)(de)(de)(de)典型(xing)能(neng)(neng)耗成本(ben)僅為(wei)(wei)(wei)0.013美元/英里(li)這一(yi)事實,便(bian)能(neng)(neng)看出(chu)能(neng)(neng)量(liang)效(xiao)(xiao)(xiao)率(lv)的(de)(de)(de)(de)整體改(gai)善情況。
遺憾的(de)(de)(de)(de)(de)是(shi),在(zai)(zai)現今(jin)的(de)(de)(de)(de)(de)市場上,純電(dian)(dian)(dian)動(dong)汽(qi)車(che)(che)(che)還不是(shi)一(yi)(yi)種可行(xing)的(de)(de)(de)(de)(de)解決(jue)(jue)方(fang)案(an),因為其行(xing)駛距(ju)(ju)離受(shou)限于(yu)車(che)(che)(che)上所能儲存的(de)(de)(de)(de)(de)能量。如(ru)(ru)今(jin)常見的(de)(de)(de)(de)(de)電(dian)(dian)(dian)池組在(zai)(zai)充電(dian)(dian)(dian)8小時之后能夠(gou)讓一(yi)(yi)輛(liang)電(dian)(dian)(dian)動(dong)汽(qi)車(che)(che)(che)行(xing)駛100英(ying)里。而一(yi)(yi)個普通的(de)(de)(de)(de)(de)汽(qi)車(che)(che)(che)油(you)(you)(you)箱則能為一(yi)(yi)輛(liang)標準汽(qi)車(che)(che)(che)提供(gong)300英(ying)里的(de)(de)(de)(de)(de)行(xing)駛距(ju)(ju)離,且只需幾(ji)分鐘(zhong)的(de)(de)(de)(de)(de)時間(jian)就能完成(cheng)加油(you)(you)(you)。如(ru)(ru)果想(xiang)得到美(mei)國消費者的(de)(de)(de)(de)(de)廣泛接(jie)受(shou),那么電(dian)(dian)(dian)動(dong)汽(qi)車(che)(che)(che)必須延長行(xing)駛距(ju)(ju)離和(he)(he)/或縮短再(zai)充電(dian)(dian)(dian)時間(jian)。應(ying)運而生的(de)(de)(de)(de)(de)解決(jue)(jue)方(fang)案(an)是(shi)“油(you)(you)(you)電(dian)(dian)(dian)混合動(dong)力(li)車(che)(che)(che)”,它把(ba)燃(ran)油(you)(you)(you)引擎(qing)和(he)(he)電(dian)(dian)(dian)動(dong)傳動(dong)系(xi)統組合起來(lai),以提供(gong)足夠(gou)的(de)(de)(de)(de)(de)行(xing)駛距(ju)(ju)離,同時仍然擁有綠色能源(yuan)的(de)(de)(de)(de)(de)大多數好處。油(you)(you)(you)電(dian)(dian)(dian)混合動(dong)力(li)車(che)(che)(che)采(cai)用(yong)車(che)(che)(che)載(zai)燃(ran)氣引擎(qing)(用(yong)于(yu)電(dian)(dian)(dian)池充電(dian)(dian)(dian)),并在(zai)(zai)需要時在(zai)(zai)最有效的(de)(de)(de)(de)(de)速度/轉矩(ju)范圍內操作(zuo)該引擎(qing)。
毫無疑問(wen),電(dian)(dian)動汽車的成(cheng)功將有助于(yu)其(qi)它(ta)應用(yong)的高性能(neng)(neng)電(dian)(dian)池(chi)系統找到屬(shu)于(yu)自己的生(sheng)存(cun)空間,從(cong)而推進(jin)其(qi)價格(ge)的下降和(he)(he)性能(neng)(neng)的提升。對于(yu)局部發電(dian)(dian)(包括小(xiao)型光伏(fu)或風力發電(dian)(dian)系統),電(dian)(dian)池(chi)可以(yi)起到至關重要的平衡作用(yong),且當(dang)(dang)可以(yi)使用(yong)電(dian)(dian)網電(dian)(dian)力時,它(ta)還能(neng)(neng)充當(dang)(dang)一個后備電(dian)(dian)源(yuan)系統。目前的電(dian)(dian)池(chi)系統相(xiang)當(dang)(dang)昂貴而且龐(pang)大,且存(cun)在可靠性和(he)(he)安全(quan)方面(mian)的問(wen)題。下一代電(dian)(dian)池(chi)系統將提供較(jiao)高的能(neng)(neng)量密度,旨(zhi)在實現外形較(jiao)小(xiao)、價格(ge)較(jiao)低、可靠性和(he)(he)安全(quan)性更高的解決方案。
高電壓電池(chi)組的設(she)計(ji)挑(tiao)戰(zhan)
對于大功率電池應用而言,鋰離電池可(ke)作為(wei)首選的化學電(dian)池(chi),主要因為(wei)它的能量(liang)密度高。當今的電(dian)動汽車(che)和油電(dian)混合動力(li)車(che)采用的是NiMH電(dian)池(chi),如果采用鋰離子(zi)電(dian)池(chi)將使其能量(liang)儲存密度提高400%。然(ran)而(er),為(wei)了使鋰離子(zi)電(dian)池(chi)在多達數(shu)千(qian)次(ci)的充放電(dian)循環過程中保持可(ke)靠,電(dian)池(chi)系(xi)統必須解決諸多技術難題。
鋰離子電池的性能取決于電池溫度和使用期限、電池充電和放電速率以及充電狀態(SOC)。這些因素并不是獨立的。例如:鋰離子電池在放電時將產生熱量,從而增加放電電流。這有可能形成熱失控狀態,并導致災難性故障的發生。此外,把鋰離子電池充(chong)電(dian)(dian)至(zhi)100% SOC或放(fang)電(dian)(dian)至(zhi)0% SOC將迅速(su)降低(di)其容量(liang)。因(yin)此,必須將鋰(li)離子電(dian)(dian)池的(de)(de)操作限(xian)制在某個(ge)SOC范圍(wei)內,比如20%至(zhi)80%,此時的(de)(de)可用(yong)容量(liang)僅(jin)為規定容量(liang)的(de)(de)60%。不(bu)僅(jin)如此,鋰(li)離子電(dian)(dian)池還具有平坦的(de)(de)放(fang)電(dian)(dian)曲線(圖1),其中1%的(de)(de)SOC變化可能僅(jin)表現為數毫伏的(de)(de)電(dian)(dian)壓(ya)差異。為充(chong)分利(li)用(yong)電(dian)(dian)池的(de)(de)可用(yong)電(dian)(dian)壓(ya)范圍(wei),電(dian)(dian)池系(xi)統必須非常準確地監視電(dian)(dian)池電(dian)(dian)壓(ya)(它直接對應于(yu)SOC)。
除了鋰離子電(dian)(dian)(dian)池的(de)敏感(gan)特(te)性之外(wai),把電(dian)(dian)(dian)池組合在(zai)(zai)一起的(de)方法(fa)也是(shi)一個(ge)重(zhong)要(yao)的(de)考慮因素。如欲從一個(ge)電(dian)(dian)(dian)氣系統(tong)(比如用于給車輛加速所需(xu)的(de)電(dian)(dian)(dian)氣系統(tong))來提供有(you)效的(de)功率(lv)(lv),則(ze)需(xu)高達(da)數百伏的(de)電(dian)(dian)(dian)壓。舉例來說,在(zai)(zai)1V電(dian)(dian)(dian)壓條件(jian)下輸送1kW功率(lv)(lv)需(xu)要(yao)1,000A電(dian)(dian)(dian)流(liu),而在(zai)(zai)100V電(dian)(dian)(dian)壓條件(jian)下輸送1kW功率(lv)(lv)則(ze)僅需(xu)10A電(dian)(dian)(dian)流(liu)。系統(tong)布線(xian)和互連線(xian)中的(de)固有(you)電(dian)(dian)(dian)阻將轉(zhuan)換成(cheng)IR損耗,因此(ci)設計(ji)師需(xu)采用切實可行的(de)最(zui)高電(dian)(dian)(dian)壓/最(zui)低電(dian)(dian)(dian)流(liu)。