فوتوولتیک‌های ترکیبی با ساختمان (BIPV) یک نوع مصالح و مواد فوتوولتیک هستند که برای جایگزین کردن مواد قدیمی و سنتی در بخشهایی از پوشش ساختمان مثل پشت بام، پنجره‌های شیروانی (سقف) یا سر در و نمای خانه‌ها، به کار می‌روند. آنها به طور فزاینده ایی در ساخت ساختمان‌های جدید به کار رفته‌اند، مثلاً به عنوان منبع اصلی (عمده) یا منبع مویین و بسیار کوچک توان الکتریکی، هر چند که ساختمانهای فعلی ممکن است از تکنولوژی مشابهی نیز بهره گرفته باشند. مزیت فوتوولتیک‌های ترکیبی نسبت به سیستمهای غیر ترکیبی رایج تر این است که می‌توان با کاهش مبلغ خرج شده برای مصالح ساختمان، هزینه اولیه را حذف کرد و کاری که معمولاً برای ساخت قسمتی از ساختمان که جایگزین مدولهای (بخشهای) BIPV می‌شود، نیاز می‌شود، را انجام نداد. این مزیتها باعث شده که BIPV یکی از سریع / پیشرفت ترین بخشهای صنعت فوتوولتیک باشد. واژه فوتوولتیکهای به کار رفته در ساختمان (BAPV) گاهی برای اشاره به فوتوولتیکهایی به کار می‌روند که پس از تکمیل ساخت ساختمان، در آن نصب می‌شوند. اکثر تاسیسات ترکیبی در واقع BAPV هستند. برخی از سازندگان بین ساخت و سازهای جدید BIPV و BAPV تمایز قائل می‌شوند...

 

پیشرفت در روش های تولید باکیفیت و بازدهی محصولات را بهبود می بخشد و باعث ایجاد افقی روشن در زمینه تولید انبوه می گردد.عمومی شدن بحث نانوفناوری و سود دهی بالای آنها موجب شده تا بیشتر محققان در زمینه گسترش کاربرد های نانوفناوری به کار خود ادامه دهند.نیروی محر که همه ی این فعالیتها،گسترش مداوم نانومواد به علاوه خصوصیات و قابلیت های جدیدی است که کشف شده است.

همچنین برای افزایش تعداد تقضا برای نانومواد،نوآوریهایی انجام می شود تا عملکرد آنها اصلاح یافته و سوددهی افزایش یابد.در بسیاری از حوزه ها مانند خودرو که صنایع  در آن به حد رشد رسیده اند،استفاده از نانومواد در واقع تلاش برای مرگ و زندگی است.به عبارتی دیگر استفاده از نانو مواد در این صنایع  ودیگر صنایع به عنوان روش کسب برتری در بازار، دائما در حال گسترش است.بنابراین در اینجا به کاربردهای نانوفناوری در صنعت تولید شیشه و مزایای استفاده از این فناوری اشاره میگردد.

پنجره های هوشمند:

تصور کنید که در یکی از گرمترین روزهای آفتابی در تابستان، نور خورشید به طور مستقیم به اتاق شما میتابد و هیچ راه گریزی به جز استفاده از پنجره های با شیشه تیره برای متعادل تر نمودن گرما و نور اتاق ندارید.احتمالا تمایل دارید تا شیشه ها، تنها زمانی که نور شدت دارد درست مانند عینک های فتوکرومیک، دودی شوند.

امروزه این کار با استفاده از الکتروکروماتیک ها انجام می شود که موادی هستند که رنگ آنها در اثر جریان الکتریکی تغییر می کنند.جریان الکتریسته با ایجاد واکنش شیمیایی سبب تغییرات خصوصیات مواد شده و کاری میکند تا آنها نور را جذب یا منعکس کنند.

امروزه از صنعت الکترونیک در ساخت این نوع از شیشه های پنجره استفاده می شود به این صورت که زمانی که نور خورشید به شیشه ها می تابد جریان الکتریکی برقرار و سبب می شود تا یون ها از لایه ی ذخیره یونی به سمت لایه هدایت یونی حرکت نموده و به لایه الکتروماتیکی برسند و شیشه را تیره نمایند. با قطع جریان الکتریسیته، فرایند برعکس عمل نموده و شیشه مجددا شفاف می شود.

مقدار جریان تنظیم کرد. شرکت هایی که در این نوع از پنجره ها مشغول فعالیت هستند، موفق به ساخت پنجره های نانوکروماتیک شده اند. اساس این نمایشگرها درست مانند آنچه در الکتروماتیک ها شرح داده شد، است؛ با این تفاوت که در ساخت آنها از فناوری نانو استفاده شده است. نانوکروماتیک ها ذراتی در مقیاس نانومتر هستند که می توانند به سرعت خاموش یا روشن شوند. همچنین پایداری دوطفه ی فرایند باعث می شود که در مصرف انرژی نیز صرفه جویی شود.

شیشه های خود تمیز شونده:

شیشه های خود تمیز شونده(فتوکاتالیتی آبدوست) از سال 2002 در بازار در دسترس بوده اند که هر روز نیاز وتقاضای استفاده ازآنها افزایش می یابد. برای عمل خود تمیز شوندگی این شیشه ها، نور UV به عنوان یک پیش شرط لازم است.بنابراین شیشه ها را می توان تنها برای سطوح خارجی سازه به کار برد.با اعمال پوشش خاص (مانند اکسید تیتانیوم) و به کارگیری UV که در نور خورشید نیز وجود دارد،تشکیل اکسیژنِ فعال بر روی سطح شیشه تسریع می گردد.

این اکسیژن به لکه های چربی آلی روی سطح شیشه حمله نموده وبا تجزیه سطح تماس بین شیشه و چربی،چسبندگی کاهش یافته و چربی می تواند بهتر شسته شود؛بنابراین چربی به طور کامل از روی سطح پاک می شود. پس شیشه هایی با ترکیبی از خواص فتوکاتالی و آب دوستی می توانند تحت عنوان شیشه های خودتمیز شونده نامیده شود.

عمل دفع چربی و سطوح تمیز شونده روی سطح شیشه

سطوح آبگریز(HYDROPHOBIC):با به کار بردن پوشش های خاص، امکان افزایش کشش سطحی شیشه وجود دارد. احتمالاً بهترین مثال شناخته شده،سطح جسمیست که به تازگی واکس زده شده است. در این حالت به راحتی می توان اثر آب گریزی را در آن مشاهده نمود. به دلیل کشش سطحیِ افزایش یافته، آب دفع می شود و به شکل دانه های کروی جریان می یابد. در این حالت به دلیل آنکه سطح کفش واکس زده شده است، آب نمی تواند به سطح بچسبد. در این حالت آب به شکل قطرات و دانه هایی متراکم در می آید و به دنبال این رفتار، سعی می کند که از سطح فرار کند. عمل تمیز کنندگی این پوشش ها به این علت است که نه تنها آب، بلکه لکه های چربی و آلودگی ها نیز قادر به چسبیدن به سطح نیستند و همین باعث می شود که اگر بر روی سطح، آب ریخته شود یا بعدها باران ببارد، سطح شیشه شسته شود ( لکه های چربی شسته شده و سطح به راحتی تمیز می شود).

به دلیل کشش سطحی بالاتر ، نیاز است قطرات آب قبل از چکیدن،وزن بالاتری به دست آورند. قطرات کوچک به اندازه کافی سنگین نبوده و حتی بر روی سطوح لعاب کاری شده ممکن است خشک شده و بر روی شیشه به صورت لک و خال، اثرات آنها باقی بماند. هر آلودگی چسبنده از سطوح آب گریز، خیلی آسان تر از سطح یک شیشه معمولی می توانند خارج شوند.

تشکیل لایه نازک آبدوست(HYDROPHILIC): با عمل آب دوستی، کشش سطحی کم می شود. در چنین حالتی قطرات آب بر روی سطح پخش شده و یک لایه نازک آب بر روی سطح تشکیل می دهند. تشکیل این لایه نازک آب، دو مزیّت دارد: اوّل این که مقدار یکسانی از آب، سطح بزرگتری را خیس می کند. این عمل طور طبیعی بهره وری  تمیز کاری را در مقایسه با سطح شیشه های معمولی بهبود می بخشد. دوّم اینکه هیچ قطره بارانی بعد از باران باقی نمانده و بدین ترتیب شیشه سریعتر خشک شده و هیچ اثری از لکه باران روی شیشه باقی نمی می ماند.

مکانیزم خود تمیز شوندگی:

تیتانیا(اکسیدتیتانیوم) یک ماده نیمه هادی است که باند ممنوعه ی نسبتا وسیع دارد. وقتی یک پرتوی نور با انرژی مساوی و یا بالاتر از باند ممنوعه به آن بتابد، الکترون از باند ظرفیت خارج شده و به باند هدایت می رود. به این ترتیب یک حفره در باند ظرفیت و یک الکترون در باند هدایت ایجاد خواهد شد.

در نتیجه ی این عمل، یک جفت الکترو حفره به وجود می آید. یون های هیدروکسیل(OH) داخل حفره می افتد و منجر به تشکیل رادیکالهای هیدروکسیلی می شود که عوامل اکسیداسیون بسیار قوی هستند. این عمل باعث کاهش قدرت چسبندگی ماده ی آلی روی سطح شیشه شده و محصولات تولید شده حاصل از واکنش چربی ها با پوشش، در اثر وزش باد یا بارش آب باران از سطح جدا می شوند.

مزایا و ویژگی های شیشه های خود تمیز شونده:

 پس زدن آب و روغن از روی سطح

 عدم چسبندگی آلودگی و کثیفی ها بر روی سطح

 پاک شدن گل ولای به وسیله آب باران

 عدم رسوب گرفتن سطوح

 ممانعت از خوردگی شیشه

 جلوگیری از تشکیل اثر انگشت بر روی شیشه

 تا 20% شیشه روشنتر و شفافتر می شود

 تمیز ماندن شیشه تا مدت بسیار طولانی تر

 کاهش انتقال صدا تا 24% نسبت به شیشه های معمولی

 و...

منبع:کتاب شگفتی های نانوفناوری

برچسب‌ها: فناوری نانو در صنعت شیشه و آینه

با بومی تکنولوژی نانو هر سال در استان مرکزی ۱۰ میلیون متر مربع شیشه های حرارتی تولید می شود.

مدیر تولید شیشه های فولت گروه صنعتی کاوه گفت: این شیشه های حرارتی با لایه نشانی اتم های فلز تا ۱۶ لایه شامل فلزهای اکومنیوم، نقره، جیوه، کُرُم، وسرب  با مقیاس نانو روی شیشه های جام صورت می گیرد که مانع از عبور طیف حرارتی انرژی از این شیشه ها می شود
رحیمی گفت: تولید شیشه با کمک فن آوری نانو در این کارخانجات بومی شده و اکنون ۱۰ درصد از تولیدات ۳۰ میلیون متر مربعی این کارخانجات به تولید شیشه های حرارتی با استفاده از تکنولوژی نانو اختصاص یافته است
محمدی مدیر خط تولید شیشه های حرارتی نانوگروه کارخانجات کاوه هم گفت : این شیشه ها در قیاس با شیشه های معمولی قمیت تقریبا دو برابر داشته که با توجه به صرفه جویی تا ۸۰ درصد درمصرف انرژی این میزان کمتر از ۶ ماه برای خانواده ها و مصرف کننده ها جبران می شود
کیایی مدیر آزماشگاه کارخانجات کاوه هم گفت : نتایج آزمایشات علمی ثابت می کند که شیشه های معمولی حدود ۸۵ درصد انرژی را از خود عبور می دهند در صورتی که این میزان در شیشه های حرارتی کمتر از ۵ درصد است
رحیمی مدیر کارخانجات شیشه فلوت کاوه هم گفت: با بومی سازی تکنولوژی نانو تولید نسل جدید شیشه شامل شیشه ها خود تمیز شونده و شیشه های ضد بخار بزودی در این کارخانجات آغاز می شود
کارخانه شیشه فلوت کاوه در شهر ساوه مستقر است که سالانه ۱۰ میلیون مترمربع شیشه تولیدی خود را به ۲۰ کشور آسیایی ، اروپایی و افریقایی صادر می کند

برچسب‌ها: تولید شیشه با فناوری نانو

تهران- ایرنا- پژوهشگران دانشکده مهندسی نساجی دانشگاه صنعتی امیرکبیر به فناوری تولید نانو الیاف شیشه‌ای با قابلیت کاربرد در تولید عایق‌های صوتی و تولید پارچه‌های ضد آتش دست یافتند.

به گزارش روز شنبه گروه علمی ایرنا از روابط عمومی دانشگاه صنعتی امیرکبیر، مجری این طرح پژوهشی با تاکید بر کارایی بالای نخ و الیاف شیشه در صنعت گفت: این الیاف به خصوص برای صنایع با نیاز به استحکام بالا مانند کامپوزیت‌های سبک و در موارد نیاز به مواد عایق صوت یا ضد آتش، اهمیت دارد.
مهسا کنگازیان کنگازی افزود: بر این اساس پروژه تحقیقاتی را با عنوان «تولید نخ نانو لیفی شیشه با استفاده از الکتروریسی سل ژل همزمان با سنتز نانو ذرات نقره» اجرا کردیم تا نخ شیشه‌ای تولید کنیم.
وی با بیان اینکه این الیاف در مقیاس نانو و به روش الکتروریسی تهیه شدند، یادآور شد: در این مطالعات الیاف و نخ نانویی شیشه با استفاده از پیش ماده سیلیکونی تهیه شد.
مجری طرح خاطر نشان کرد: با اجرای این طرح توانستیم نخ شیشه‌ای نانو لیفی با استفاده از پیش ماده سیلیکونی را به همراه نانو ذرات نقره با استفاده از دستگاه الکتروریسی تولید کنیم.
وی با تاکید بر اینکه مقاله و ثبت اختراع آن در حال داوری است، ادامه داد: نخ تولیدشده بسیار شکننده بود و برخلاف سایر نخ‌های شیشه‌ای مقاومت خوب در محیط‌های به شدت اسیدی داشت.
کنگازیان با اشاره به روش اجرای این تحقیقات توضیح داد: در ابتدا نیاز به تهیه محلولی برای الکتروریسی این ماده داشتیم اما از آنجا که برای الکتروریسی وجود یک پلیمر با زنجیره‌های بلند لازم است، از یک پلیمر کمکی در کنار سنتز سیلیکا استفاده شد. همچنین برای کاهش قطر الیاف از 280 نانومتر به حدود 130 نانومتر از سنتز نقره نیز کمک گرفتیم.
وی دلیل استفاده از نانو نقره برای کاهش قطر الیاف را حضور فلزات در میدان مغناطیسی دستگاه الکتروریسی دانست که سبب کاهش قطر نانو الیاف می‌شود.
کنگازیان اضافه کرد: بعد از این مرحله برای خالص سازی نخ و از بین بردن پلیمر کمکی از کوره با دمای بالا و شستشو استفاده شد و در انتها تست‌هایی همچون شناسایی عناصر، تست‌های کششی، اندازه گیری قطر الیاف و اندازه نانو ذرات روی نخ نانویی شیشه‌ای انجام گرفت.
وی پیچیدگی طرح را در تولید محلول سل ژل با غلظت و کشش سطحی مناسب برای الکتروریسی ذکر کرد و افزود: الیاف تولیدشده در صنعت کامپوزیت سازی، عایق صوت و تولید پارچه‌های ضد آتش و دارای استحکام کاربرد دارد.
وی به مزایای دستاوردهای این پژوهش اشاره کرد و گفت: در حالی که در مطالعات قبلی تنها نانو الیاف شیشه تهیه شده بود و گزارشی مبنی بر تهیه نخ وجود ندارد، در این تحقیقات این هدف محقق شد ضمن آنکه نخ تولیدشده مقاومت در محیط‌های اسیدی را دارد.
کنگازیان بی نیازی انجام تست‌های شناسایی پرخطر و هزینه بر را از دیگر مزایای این طرح عنوان کرد.

 سطح شیشه از لحاظ میکروسکوپی بسیار متخلخل است و به راحتی آلودگی و یا قطرات آب را جذب می کند. با مرور زمان، آلودگی ها در این تخلخل ها نفوذ کرده و دیگر شیشه ها به راحتی قابل تمیز شدن نخواهند بود. آب گریزی بدین معناست که شیشه آب را دفع می کند و سطوح آ ب کریز  کمترین سطح تماس با قطرات آب را دارند و به بیان دیگر قطرات به صورت کروی بر روی این سطوح قرار می گیرند. می توان از نانو مواد برای تولید سطوحی صاف و منظم استفاده کرد که به عنوان یک شبکه منظم نفوذ ناپذیر عمل کنند. محلول تولید شده توسط نانوذرات دارای خاصیت آب گریزی است و زاویه تماس با شیشه را از حدود ۴۰ درجه به ۱۲۰ درجه افزایش داده است. با اعمال محلول نانوکلوئید شرکت نانوپاد بر روی سطح شیشه، سطح دارای خاصیت آبگریزی و خود تمیز شوندگی شده و در برابر انواع کثیفی مقاوم می شود و بارش باران شدید باعث تمیز شدن شیشه ها می گردد اعمال این پوشش بر روی سطح شیشه منجر به افزایش زاویه ( بیش از۱۱۰ درجه) قطرات آب با سطح خواهد شد و این خاصیت موجب غلتیدن قطرات کاملاً کروی آب (یا باران) روی سطح و شسته شدن آلودگی ها از روی آن می گردد. همچنین اعمال پوشش نانو بر روی سطح شیشه باعث محافظت در برابر اشعه UV خورشید، جلوگیری از جذب عمقی آلودگی ها روی سطح، خاصیت آسان تمیز شوندگی و مقاومت در برابر باران های اسیدی می شود .

اعمال این پوشش بر روی سطح، شیشه را مات و براق نمی کند و همچنین می تواند از اشیاء داخل ساختمان یا خودرو نسبت به نور خورشید محافظت کند. معمولا در بیشتر شیشه های خودرو و شیشه هایی که از آنها استفاده های صنعتی می شود، سطح شیشه به مرور زمان ساییده می شود و بر روی آن چاله های ریزی ایجاد می شود. این پوشش علاوه بر ضد آب و لک کردن شیشه که از کثیف شدن آن جلوگیری می کند، خواص مکانیکی شیشه را هم افزایش می دهد. همچنین به دلیل عدم جذب آلاینده ها بر روی سطح شیشه، با وزش باد و بارش باران شیشه آب گریز تمیز می شود .

نحوه مصرف 

 سطح شیشه مورد نظر باید تمیز، خشک و عاری از هرگونه آلودگی و مواد اضافی باشد .

 ظرف محتوی محلول آب گریز شیشه به خوبی تکان دهید .

 محلول آبگریز شیشه را بر روی سطح شیشه اسپری کرده بطوری که تمامی سطح آغشته به محلول گردد .

 پس از 9 دقیقه دستمال میکروفایبر را با محلول نانو آغشته و به صورت دورانی سطح مورد نظر را به آرامی ماساژ دهید .  

 شیشه مورد نظر پس از خشک شدن و گذشت 9 ساعت دارای خاصیت آب گریزی خواهد شد .

مزایا 

 افزایش زاویه (بیش از ۱۱۰ درجه) قطرات آب با سطح شیشه

 غلتیدن قطرات کاملاً کروی آب (یا باران) روی سطح و شسته شدن آلودگی ها از روی شیشه

 سدی در برابر اشعه UV خورشید

 خاصیت آسان تمیز شوندگی و مقاومت در برابر باران های اسیدی

 جلوگیری از سائیده شدن به وسیله عبور ریزگردها از روی سطح

شیشه خودرو

 قرار گرفتن محافظ نانو بر روی شیشه خودرو به صورت لایه ای نامرئی

 عدم تغییر در وضوح بافت شیشه

 ایجاد سطح بسیار شفاف و دید واضح

 نچسب کردن شیشه ها و آئینه ها و عدم انباشته شدن گرد و خاک، چربی، روغن، قیر، حشرات مرده و

شیره گیاهان بر روی شیشه

 بهبود قابلیت دید راننده به علت قطره قطره شدن باران بر روی سطح شیشه

شیشه ساختمانی

 ایجاد سطحی دارای خاصیت آبگریزی و خود تمیز شوندگی و مقاوم در برابر انواع کثیفی

 تمیز شدن شیشه ها توسط بارش باران شدید

 حفظ شدن شفافیت اولیه سطح شیشه

 جلوگیری کردن از مات شدن و کدر شدن در اثر شرایط

 محافظت از اشیاء داخل ساختمان و پشت پنجره ها مثل تابلو، پرده، مبل و غیره در مقابل نور خورشید

 کاهش دفعات تمیز کردن شیشه نمای ساختمان به حداقل ممکن

برچسب‌ها: نانو کلوئید آبگریز شیشه

The idea that the air that we breathe could turn into a liquid is counterintuitive to say the least, but scientists have known how to liquefy the constituents of air for well over a century, and the industrial gases industry now produces thousands of tonnes of liquid nitrogen and liquid oxygen every day. However, these gases need not be separated when liquefied, in which case the result is liquid air. A number of technologies are now being developed to exploit liquid air – or liquid nitrogen, its main constituent - as an energy vector.

Air can be turned into a liquid by cooling it to around -196C using standard industrial equipment. 700 litres of ambient air becomes about 1 litre of liquid air, which can then be stored in an unpressurised insulated vessel. When heat is reintroduced to liquid air it boils and turns back into a gas, expanding 700 times in volume. This expansion can be used to drive a piston engine or turbine to do useful work. The main potential applications are in electricity storage, transport and the recovery of waste heat.

Since the boiling point of liquid air (-196C) is far below ambient temperatures, the environment can provide all the heat needed to make liquid air re-gasify. However, the low boiling point also means the expansion process can be boosted by the addition of low grade waste heat (up to +100C), which other technologies would find difficult to exploit and which significantly improves the energy return. There are myriad sources of low grade waste heat throughout the economy (see chapter 5).

The industrial gases industry has been producing liquid nitrogen and liquid oxygen – the main components of liquid air - for over a century. These cryogens have a wide range of applications including steel-making, food processing, medicine and superconducting technologies. Since oxygen and nitrogen liquefy at similar temperatures, and since there is four times more nitrogen than oxygen in the atmosphere but much less demand for it commercially, the industry has substantial spare nitrogen production capacity. The thermo-physical properties of liquid nitrogen and liquid air are similar, so a cryogenic energy vector could be provided by either.

There have been several attempts to exploit liquid air or liquid nitrogen as an energy vector over the past century without commercial success. However, technological advances and market evolution in the early years of this century appear to have made it a practical and economic possibility worth considering again. In this chapter we describe how liquid nitrogen and liquid air are produced, and introduce the new technologies being developed to exploit them as energy vectors.

 

Attempts to develop liquid air as an energy vector date back to 1900, when the Tripler Liquid Air Company was formed in the US to develop a liquid air car that briefly competed with the steam and electric vehicles of the day.¹ But early liquid air vehicles required bulky and inefficient external heat exchangers, and soon the internal combustion engine came to dominate road transport, so it was not until the second half of the twentieth century that interest in cryogenic engines revived.

In the 1960s, self-powered cryogenic pumping systems² were explored as an alternative to electric pumps for fuel delivery in rockets. However, this was at the height of the space race and cold war, so very little information is available. With the arrival of the oil crises in the 1970s interest in cryogenic cars returned, and a number of patents were filed, although few, if any, vehicles were actually built.³ There was also interest in developing liquid air as a grid-scale energy store, evidenced by a paper presented to a conference of the Institution of Mechanical Engineers in 1978.⁴

The 1980s saw the first recorded work on hybrid or dual-fuel cryogenic vehicles, where fossil fuels were typically used to raise the temperature of a cryogenic working fluid to increase its energy density. The combination of cryogenic engine and internal combustion engine was found to produce synergistic increases in efficiency, which in one case delivered a 50% greater range than using each fuel on its own.⁵

Another engine proposed in 1984 with the help of US Department of Energy funding⁶ worked by superheating liquid nitrogen to very high temperatures in a furnace powered by any fossil fuel, before expansion in the cylinder. The fuel consumption of this configuration was 4.2 miles per gallon of liquid nitrogen and 132 mpg of petrol. At 1984 prices, projected driving costs were comparable to a similar specification petrol car. Systems using LNG as the fuel were also proposed.

In the early 1990s, the California Air Resources Board’s Zero Emission Vehicle mandate created significant interest in alternative engine technologies. Recognising the limitations of electric vehicle concepts of the time, the Universities of Washington and North Texas began research programmes into cryogenic engines for transport, and built some demonstration units capable of achieving speeds of a few miles per hour.⁷

A number of utility-scale applications were also developed and tested, including one from Mitsubishi called LASE – Liquid Air Storage Energy System.⁸ The design involved producing liquid air during off-peak periods and then pressurising it to supply high pressure gas to the air inlet valve of a gas turbine to boost its output.

After a century of faltering attempts to exploit liquid air, what appears to have been a significant breakthrough came in 2001, when the British inventor Peter Dearman developed and patented the Dearman Engine. Mr Dearman’s key insight was that liquid air could be vaporised inside the engine cylinder using heat supplied by a thermal fluid mixture such as water and antifreeze, eliminating the need for the bulky and inefficient external heat exchangers of traditional cryogenic engines. This insight allowed Dearman to make simple modifications to a small car and run it on liquid nitrogen at speeds of more than 30mph.⁹

By contrast, in 2005 the Ukranian Kharkov National Automobile and HighwayUniversitydeveloped a two person lightweight road car whose design continued to rely on an ambient heat exchanger, and this achieved just 10 kph for 42 minutes on 22 kg of liquid nitrogen.¹⁰

After buying the rights to the Dearman Engine, Highview Power Storage went on to develop the grid scale energy storage system described below. In 2006, working with scientists at the University of Leeds, Highview developed a series of efficiency enhancements to the liquid air cycle by integrating the production and expansion processes to make use of waste heat and cold, so making the concept economically viable. In 2010, Highview spun off the Dearman Engine Company to develop a cryogenic engine for transport applications. Today a number of companies around the world are investigating the use of liquid air as an energy vector for transport and grid scale applications.

 

Air is made up of nitrogen (78%), oxygen (21%) and argon (1%), and these components can be separated because they liquefy/boil at different temperatures: nitrogen at -196°C, oxygen at -183°C and argon at -186°C. This is done using an Air Separation Unit (ASU).

First the air must be cleaned through a dust filter, and compressed to a pressure of about 6 bar (Figure 2.1, step 1). The compressed air is then cooled down to a temperature of about 15°C (2). Then water and CO2, which would otherwise freeze and block pipes in the ASU, are removed using a molecular sieve in a process known as adsorption (3).

The cleaned air is then cooled down to close to liquefaction temperatures by repeatedly compressing and expanding the gas and passing it through a heat exchanger, much like a domestic refrigerator (4). Most of the energy needed for air separation is consumed by this part of the ASU.

The extremely cold air is now separated into its components in two distillation columns (5), in which gas moves to the top and liquid falls to the bottom. In the first, medium pressure column, air is separated into nitrogen gas and an oxygen enriched liquid containing 30% oxygen. In the second, low pressure column, the full separation of oxygen and nitrogen is achieved, and both are available in liquid or gaseous form (6). These products are typically delivered to customers as compressed gases by pipeline or cylinder, or as liquids by road tanker.

 

 

Figure 2.1: Air Separation Unit. Source: Messer

 

The process inevitably produces excess nitrogen, because there is four times as much nitrogen as oxygen in the atmosphere but much less demand for it commercially. Some of the excess nitrogen is recycled to cool incoming air, so raising the energy efficiency of the ASU, but much is vented harmlessly to the atmosphere. Spiritus Consulting estimates excess nitrogen production capacity in the UK at 8,500 tonnes per day (tpd) (see chapter 6). Since this excess nitrogen is in gaseous form, exploiting it as an energy vector would require the construction of additional liquefiers at existing industrial gas production sites.

Air can be liquefied without separating the oxygen and nitrogen using only the ‘front end’ of an ASU – essentially steps 1-4 above. Air is cleaned, compressed and water and CO₂ removed, and the air then liquefied using a compressor, turbines and a heat exchanger (a ‘liquefier’). There is no need for the distillation columns, and the liquid air can then be stored in tanks similar to those used for liquid oxygen or nitrogen. A diagram of this simpler process is shown in Figure 2.2.

 

Figure 2.2: Air liquefier

 

The amount of energy required to produce a tonne of oxygen or nitrogen using ‘best available technology’ is shown in Table 2.1.¹¹ According to Messer, the German industrial gas company, of the 549kWh required to produce a tonne of liquid nitrogen, about 20% is consumed in the separation process. Producing a tonne of liquid air therefore consumes about 439kWh.

 

Table 2.1: The energy consumption of oxygen and nitrogen production.  

Source: EIGA¹²

 

Liquefied gases can be stored in two types of tank: smaller vacuum insulated, and larger flat-bottomed. The advantage of vacuum insulated tanks is that they can be operated at any pressure required, depending on the construction material. They can be economically produced up to a size of 300m³. Any tank larger than 500m³ will be flat bottomed, insulated with the volcanic material perlite, and will operate at near-atmospheric pressure – typically 30-100mbar.

Because the temperature outside the tank is typically ~200C warmer than inside, heat leaks inwards and causes some of the liquid to boil off. The boil-off rate for both vacuum insulated and flat-bottomed tanks is about 0.1-0.2% per day – although the rate for larger tanks can be as low as 0.07%. Because nitrogen boils at a lower temperature than oxygen, a tank of liquid air may gradually become oxygen enriched. As we discuss in chapter 8, this is a hazard that must be managed, since liquid oxygen is highly reactive.

 

A large scale, long duration energy storage system based on the liquid air cycle has recently been developed by Highview Power Storage and demonstrated at a 300kW pilot plant in Slough. The plant is hosted by SSE (Scottish & Southern Energy) next to its biomass power station, and was partly funded by the Department of Energy and Climate Change (DECC). The pilot plant has been successfully tested against standards set by National Grid and other international electricity system operators (UK STOR and TRIAD markets, US PJM market). A 10MW commercial demonstration plant is now planned, and the company predicts efficiencies and costs will improve at progressively larger scales. The system is built from components already widely used in the industrial gases and electricity generating industries, but combined in a novel form that the company calls a Cryo Energy System, and describes more generically as Liquid Air Energy Storage.

The system consists of three main elements: charging, storage and power recovery (see figures 2.3 and 2.4). First, grid electricity is used to power an air liquefaction plant (the front end of an industrial gas separation unit) to refrigerate air to its liquid state. The liquid is then stored in an insulated tank at low pressure*, which functions as the energy store. When power is required, liquid air is drawn from the tank and pumped to high pressure and into a heat exchanger, where ambient and low grade waste heat turns the cryogen into a high pressure gas, which is then used to drive a turbine and generator to deliver electricity back to the grid.

Cryogenic tanks that hold less than 100 tonnes are typically held at

 

Figure 2.3: Schematic of a Liquid Air Energy Storage system. Source: Highview Power Storage

 

The efficiency of the process is increased by exploiting both waste heat and waste cold. The use of low grade waste heat during expansion generates additional power that improves the overall round trip efficiency of the cycle; the cycle’s maximum efficiency is determined by the highest and lowest temperatures, so raising the higher temperature with waste heat increases the available work. At Slough, waste heat at around 60C is sourced from the biomass power station next door. Performance data shows this heat is converted into power at an efficiency of 50-60%.¹³

 

 

Figure 2.4: the Highview Power Storage pilot plant in Slough. Source: Highview Power Storage

 

BOX 2.1: Liquid Air Energy Storage process 

 

Figure 2.5: Schematic of a Liquid Air Energy Storage device. Source: Highview Power Storage. 

 

The schematic separates the process into three sections: charging (grey); storage (green); and discharge or power recover (red). The air is first compressed (1) and passed through a filter to remove water and carbon dioxide, that would otherwise freeze and block the process. The air is compressed in a recycle air compressor (2) and then cooled in a series of heat exchangers, referred to as a cold box (3). The now very cold air is expanded where most of the flow condenses to liquid (4). The part of the flow that is not condensed returns through the cold box to cool the main high pressure flow. Part of the flow from the recycle compressor is diverted to a separate channel in the heat exchanger where it is cooled and expanded through a turbine (5). This achieves more efficient cooling and reduces the energy required to liquefy the air. The liquid air is then stored in an insulated tank (6). The discharge process follows the Rankine cycle. The thermal energy required to heat the cold liquid after compression is captured and stored in a thermal store (7) after the liquid pump (8). The resulting warm high pressure gas is expanded through a series of turbines (9) to generate electricity. 

The process as described could achieve an efficiency of around 25%. The efficiency is greatly increased by storing and recycling the thermal energy released during the power recovery process, more than doubling the process efficiency to 50-60%. This is achieved by capturing the cold thermal energy released during the power recovery process in a thermal store, typically a bed of gravel. The thermal energy stored in the gravel bed is then used to improve the efficiency of the liquefaction process by circulating dry air through the cold box and thermal store, transferring the thermal energy from the store to the cold box. The result of this ‘cold recycle’ is that less air is recycled round the process through the expansion turbines (5) and more of the air is turned to liquid during the expansion process at the separator (4), reducing the energy cost of manufacturing a specific quantity of liquid air. 

 

The turbine exhaust gas is also recycled as part of the process and its residual heat removed to help drive the evaporation of the cryogen. This then produces a very cold gas stream, the cold content of which is stored in a proprietary high-grade cold store, and used to pre-cool incoming air when liquefaction next takes place, so further raising the efficiency of the plant. The process is described in more detail in Box 2.1.

The pilot plant was fully commissioned in July 2011 and has been tested for cold recycle, reliability, response and heat to power performance. In testing against National Grid STOR criteria, the pilot plant proved 95% reliable, considered high for a pilot plant, and in testing against the US PJM self testing protocol, the plant was 99.8% compliant – against a pass mark of 75% - as reviewed by the PJM assessors. The plant was able to reach desired output within 2½ minutes, meaning that at larger scale the technology is a potential candidate for the fast reserve market as well as STOR. A full technical description of the Cryo Energy System provided by the company forms Appendix 1.

The pilot plant was built from standard components that are widely used in the industrial gases and power generation industries. The company is now planning a 10MW/40MWh Commercial Demonstration Plant with ~300 t/day liquefaction plant and a high grade cold store on the same basis. All of the main components of the system are more efficient at commercial scale, and the company has calculated this will raise round-trip efficiency to 60%.¹⁴ Other companies are also reported to be investigating the opportunity of liquid air storage, including Praxair, Air Products and Expansion Energy in the US, but there is no news to date of any hardware deployed.

 

The Cryo Energy System is a fully integrated electricity storage system in which liquid air is produced and consumed on the same site. However, liquid air could also be produced in one place and used to generate electricity in another. The liquid would be transported between sites in the same way industrial gas companies distribute liquid oxygen and nitrogen today - typically by road tanker (Figure 2.6). This might make sense for applications where the generator is too small, or used too infrequently, to justify the cost of building an on-site liquefier. It could also make use of an estimated 8,500 tonne per day surplus of nitrogen production capacity in the UK (chapter 6). 

Highview Power Storage has developed a generation-only device to fulfil this function called the Cryogenset. It is essentially the same as the Cryo Energy System described above but without the liquefier, and whereas the storage system would scale from 10MW to several 100MW, the Cryogenset is designed for 3-10MW.

The Cryogenset is intended eventually to compete with diesel generators and Open Cycle Gas Turbines (OCGT) in their roles as corporate emergency back-up power and grid peaking plant that typically generate for less than 100 hours per year (chapter 3). It is estimated that UK companies have diesel generators with a total capacity of around 15GW, of which about 2.5GW are in units of 1MW or larger. National Grid currently contracts 493MW of diesel generation and 346MW of OCGT capacity as part of its Short Term Operating Reserve.¹⁵ The Cryogenset shares many characteristics of diesel gensets and OCGT, such as low capital cost and relatively fast start up times (less than 15 minutes), but with the added benefit of lower carbon emissions, since liquid air generated from off-peak electricity is likely to be less carbon intensive than diesel or gas when burned in inefficient open cycle plants (chapter 10).

 

 

Figure 2.6: Schematic of a Cryogenset. Source: Highview Power Storage

 

 

The Dearman Engine Company is developing a cryogenic engine that operates through the vaporisation and expansion of liquid air or liquid nitrogen. Ambient or low grade waste heat is used as an energy source with the cryogen providing both the working fluid and heat sink. Heat is introduced to the cryogenic fluid through direct contact heat exchange with a heat exchange fluid (HEF) inside the engine.

Figure 2.7 shows an overview of key parts of the Dearman Engine process. On the return stroke a warm heat exchange fluid flows into the cylinder filling nearly all of the dead volume. Just after top-dead centre the liquid air or nitrogen is injected directly into the heat exchange fluid. There is a large surface area and temperature differential and this causes the cryogenic fluid to boil very rapidly.

As the fluid turns into a gas it expands, and this expansion process drives the piston down the cylinder for the power stroke. During this process, the heat exchange fluid keeps giving up heat to the expanding gas ensuring a nearly isothermal expansion – the gas expands yet the temperature remains relatively constant.

 

 

Figure 2.7: The Dearman cycle. Source: Dearman Engine Company

 

At bottom dead centre an exhaust valve opens allowing the mixture of gas and heat exchange fluid to exit the cylinder. The heat exchange fluid is recovered from the exhaust stream and reheated whilst the air or nitrogen gas is exhausted to the environment.

While cryogenic expansion engines are not new, previous incarnations have worked on an open Rankine cycle – similar to a traditional steam engine but operating across a different temperature range. Under this arrangement the cryogenic fluid is pumped to operating pressure and vaporised through a heat exchanger before expansion in the engine cylinder.

A number of drawbacks exist with this arrangement when applied to mobile applications, since the heat exchanger must be large to cope with the heat transfer rates, and heavy to withstand the high pressure. Since little heat is added to the gas during the expansion phase in the engine cylinder, it cools while expanding (near adiabatic expansion) so reducing the work output.

The novelty of the Dearman Engine lies in the use of a heat exchange fluid (HEF) to facilitate extremely rapid rates of heat transfer within the engine. This allows injection of the liquid cryogen directly into the engine cylinder where heat transfer occurs via direct contact mixing with the HEF. The heat transfer on injection generates very rapid pressurisation in the engine cylinder. Direct contact heat transfer continues throughout the expansion stroke giving rise to a more efficient near-isothermal expansion.

The inventive step is covered by a patent covering the European Patent Office (EPO), US and Japanese territories. In December 2011 the company filed a subsequent application covering insights derived from its engine testing experience.

The specific work available from an expansion over a variety of pressures is shown in Figure 2.8 for both adiabatic expansion, where no heat is added and the gas inevitably cools as it expands, and isothermal expansion, where heat is added during expansion to maintain a constant temperature, so increasing the work output. The dashed lines indicate the specific work from the expansion net of pumping work.

 

 

Figure 2.8: Specific work from the expansion of liquid air

 

The benefit of the pressurisation process taking place in the cylinder is to reduce the amount of pumping work required to reach a given peak cylinder pressure, meaning that the likely specific work from a kilogramme of liquid nitrogen is between the dashed and solid lines. The benefit of having a heat source present during the expansion stroke - the core Dearman Engine invention - is demonstrated by the difference in specific work availability between the adiabatic and isothermal processes. Taking the benefits of in-cylinder pressurisation and heat transfer together, the likely specific work from a kilogramme of liquid nitrogen is between the dashed and solid red lines.

The engine has two unique capabilities within the zero-emission engine space:

Heat to power

The Dearman Engine power cycle has a bottom temperature of about -196C and peak cycle temperature of ambient, meaning even relatively low grade heat can increase the peak cycle temperature and be converted into additional work at very high conversion efficiencies. The Dearman Engine can be deployed as a high yield thermal energy recovery system that could convert heat from the exhaust or coolant systems of an internal combustion engine into shaft power at conversion efficiencies of up to 50%. This would have the advantages of:

• reducing or eliminating the loads associated with heat rejection on the IC engine;

• enabling the IC engine to be downsized;

• displacing a material portion of transport related emissions into an energy vector (liquid air) that can be produced from renewable sources.

Initial comparison suggests that liquid air can be profitably substituted for on-highway hydrocarbons, so there is a fuel cost saving too (see chapter 6).

Fuel cells also give off large amounts of heat, so in future the Dearman engine could be used to raise the efficiency of vehicles powered by hydrogen (chapter 5) as well as fossil fuels.

Cooling

The engine absorbs significant quantities of heat during its operation and so can be viewed as a heat sink or cooling source. If there is a requirement for a heat sink or cooling source (eg air conditioning or refrigeration) then a Dearman Engine can simultaneously displace cooling loads and generate shaft power. The engine absorbs approximately twice as much heat as shaft power generated.

 

The auto engineering consultancy Ricardo is conducting engine development for the Dearman Engine Company, and a fully characterised bench prototype is expected to be completed by the end of 2013. However, Ricardo has also proposed another engine concept to exploit the potential benefits of liquid nitrogen. Whereas the Dearman engine uses liquid air as fuel, Ricardo’s engine would run on petrol or diesel but incorporate a quantity of cryogenic gas into the cycle to make it significantly more efficient. The Ricardo design is based on advances in static electricity generation technology.

In power generation, a Combined Cycle Gas Turbine (CCGT) is extremely efficient in spite of its low compression ratio. This is because the temperature difference between the compressed inlet air (Figure 2.9 position 2) and the exhaust gas (position 5) is big enough to allow significant heat transfer, meaning that heat from the exhaust can be used to raise the temperature of the compressed air through a heat exchanger or ‘recuperator’ before combustion. This reduces the amount of fuel required to achieve the same output.

 

 

Figure 2.9: Combined Cycle Gas Turbine

 

By contrast, the ICE derives its efficiency from having a high compression ratio, and this means the temperature of the compressed air is too close to that of the exhaust to allow effective heat transfer; waste heat from the exhaust cannot be recovered. In addition, most ICE designs compress and expand the air in the same cylinder, making it impractical to introduce a recuperator into the system.

This problem can be overcome using a split cycle engine design similar to the Isoengine concept first developed by Ricardo in the 1990s and the Scuderi engine today. In such designs, compression takes place in one cylinder and expansion in another, which is similar in concept to a gas turbine. However, to make the split cycle thermodynamically efficient requires isothermal compression, in which the air remains at a relatively constant temperature despite being compressed. The temperature-entropy diagram in Figure 2.10 shows how isothermal compression allows the temperature difference between the compressed intake air and the exhaust gas to be maximised, so creating an opportunity for waste heat recovery.

 

Figure 2.10: Recuperated diesel cycle with high compression ratio and isothermal compression. Source: Ricardo

 

Isothermal compression can be achieved by spraying a fluid into the compression chamber to absorb heat from the gas being compressed, and this approach has been tested in a 3MW power generation demonstrator using water. However, although this produced a large demonstrable gain, raising gas to electricity conversion efficiency to 59%, it also required large quantities of water because of the small temperature difference between it and the air being compressed, along with complex and expensive water management equipment.

The Ricardo split cycle invention replaces water with liquid nitrogen which is far colder at about -200C, meaning that far smaller volumes are required. In addition, once vaporised during compression the nitrogen can then pass straight through the combustor and be exhausted to the atmosphere. As a result, the system can be made far more compact and suitable for vehicle engines.

Detailed modelling of this approach under-taken through the TSB ‘CoolR’ programme has suggested an efficiency of more than 60%. As a result, a modest onboard tank of liquid nitrogen would extend the range of the vehicle by increasing the efficiency of the primary engine. Liquid nitrogen could also be produced by an onboard liquefier driven by the engine and boosted by regenerative braking.

 

Technologies that use liquid air as an energy vector exploit its thermo-physical properties - its expansion between liquid and gaseous phases and/or its ability to absorb heat. Air and nitrogen have relatively similar thermo-physical properties and so most technologies under consideration (except the Ricardo split-cycle engine) could use either liquid nitrogen or liquid air. The choice is likely to be driven by existing supply, economics, infrastructure, safety and application-specific factors.

One major advantage of nitrogen is the industry has a substantial surplus of production capacity both in the UK and globally (chapter 6). This arises because there is four times more nitrogen than oxygen in the atmosphere but much less demand for it commercially. Spiritus Consulting estimates the surplus amounts to about 8,500 tonnes of nitrogen gas per day, which currently is simply vented to the atmosphere. To turn this into a cryogenic energy vector would require investment in additional liquefiers. If that were done, this surplus could absorb 4.6GWh¹⁶ of ‘wrong time’ wind generation and, at 60% round trip efficiency, deliver 2.8GWh back to the grid, enough to power the equivalent of 310,000 households.¹⁷ Alternatively it could potentially fuel the equivalent of 6.5 million car kilometers daily.¹⁸ Since the marginal cost of exploiting this waste product is low (chapter 6), it is likely that many early applications of ‘liquid air’ would in fact run on liquid nitrogen.

Once the nitrogen surplus has been exhausted, liquid air would have an economic advantage since its production requires less equipment and less energy than liquid nitrogen and should therefore be cheaper. A wide range of air liquefiers is already available commercially, ranging from small-scale units producing 2,000 litres per day, made by companies such as Stirling Cryogenics of the Netherlands¹⁹, to industrial plants of about 30 tonnes per day, such as the Chinese unit installed by Highview Power Storage at its pilot plant in Slough. There is no barrier to scaling these liquefiers up to units of several thousand tonnes per day as they are typically based on industry standard designs for nitrogen liquefiers which are already available at these scales. Once investment in new plant is required to supply cryogenic energy vectors, these simpler and cheaper systems will have a cost advantage, and liquid air may therefore be preferred over liquid nitrogen. 

One disadvantage of liquid nitrogen compared to liquid air is that its exhaust is not breathable since it contains no oxygen (safety issues are covered in detail in chapter 9). This would preclude its use in enclosed spaces such as mines or warehouses without appropriate ventilation and oxygen monitoring equipment – the same precautions employed for fossil fuel powered engines. In these circumstances liquid air would be the preferred option, since the exhaust is breathable. Both liquid air and liquid nitrogen would provide free cooling from cold exhaust.

The disadvantage of liquid air is the potential for oxygen enrichment, which is a potentially serious hazard, although one that has been safely managed by the industrial gases industry for decades. Liquid air can become oxygen-enriched because nitrogen has a lower boiling point than oxygen, and so can evaporate more quickly in some circumstances, raising the oxygen concentration to higher than that found in the atmosphere. As we discuss in chapter 9, this hazard can be managed using equipment to prevent such enrichment, monitoring and safety procedures.

In the case of liquid air that is produced and consumed over short periods or hours or days – a grid balancing unit operating in the STOR market, for example - there is no danger of enrichment in any event.²⁰ But for strategic energy storage over weeks or even months, the risk would be higher. In this case the risk could either be managed as described earlier, or eliminated entirely by using liquid nitrogen rather than liquid air (chapter 9).

Neither liquid air nor liquid nitrogen emit CO₂ at the point of use, and both can be low carbon energy vectors depending on the energy source used to produce them. Liquid nitrogen is already typically generated during off-peak hours when electricity prices and carbon intensity are lower. In future, production of liquid nitrogen and liquid air could be ‘wind-twinned’ – concentrated in periods when the proportion of wind generation is highest.

Nor do they produce the nitrous oxide (NO_X), sulphur dioxide (SO_X) or particulates (PM10) associated with diesel generators, so cryogenic backup generators could have a beneficial impact on air quality in urban areas.

On balance it seems likely that early applications will exploit the nitrogen surplus except where there are specific reasons to choose liquid air, and that over time, as new production capacity is built, the advantages of liquid air over liquid nitrogen will become more compelling.

 

From the discussion presented in this chapter we conclude:

• There is a sporadic history of failed attempts to exploit liquid air as an energy vector, but technological breakthroughs and market evolution since the turn of the century make it worth investigating once again.

• Liquid air is not currently produced commercially but easily could be. There is a large surplus of liquid nitrogen gas available for liquefaction, and this would offer similar thermo-physical properties to liquid air.

• Liquid air and/or nitrogen offer a means to exploit myriad sources of waste heat.

• A number of promising technologies to exploit liquid air have either been demonstrated already or are in development.

 

Endnotes

¹
The World, New York, June 24th 1900

²
Cryogenic engine system and method. E.H. Schwartzman. Patent number US3451342, 1969.

³
Non-pollution motors including, cryogenic fluid as the motive means, H.L. Boese and T.R. Hencey, Patent number US3681609, 1972.

⁴
Storage of Electrical Energy Using Supercritical Liquid Air, E.M. Smith, Proc. Inst. Mech. Eng., pp289-298, 1977.

⁵
Engine systems using liquid air and combustable fuel, A.L. Latter et al., Patent number US4359118, 1982.

⁶
The cryogenic nitrogen automotive engine, J.L. Dooley and R.P. Hammond, Mechanical Engineering, pp66–73, October 1984.

⁷
Cryogenic heat engines for powering zero emission vehicles, C.A. Ordonez et al., ASME IMEC, PID-25620, 2001.

⁸
Development of Generator of Liquid Air Storage Energy System, Kenji Kishimoto et al., Mitsubishi Heavy Industries Technical Review, October 1998.

⁹
Inventor’s creation not just hot air, BBC News, 2 October 2012, http://www.bbc.co.uk/news/technology-19802190.

¹⁰
Development first in the ukraine demonstrational model of non-polluting automobile with cryogenic powerplant, A.N. Turenko et al., ISJAEE, 4 (24), 2005.

¹¹

Indirect CO2 emissions compensation: Benchmark proposal for Air Separation Plants, European Industrial Gases Association (EIGA), position paper #33, December 2010, http://eiga.org/fileadmin/docs_pubs/PP-33-Indirect_CO2_emissions_compensation_Benchmark_proposal_for_Air_Separation_Plants.pdf

¹²
Ibid.

¹³
Results from performance tests carried out by Highview at the Slough site, personal communication, February 2013. 

¹⁴
Because of its small scale the pilot plant operates at a subcritical pressure (peak process pressure 13bar), whereas at commercial scale the plant would operate at a supercritical pressure (>38bar). This means that in the pilot plant the majority of the air is reduced to liquid by means of cooling to the saturation point, giving a low efficiency of 7-12%. In the commercial plant the air is cooled to a level above the saturation temperature and then expanded through a Joule-Thomson valve to reduce to liquid. This is a significant factor in the higher efficiency of a commercial scale plant, calculated to be 60%. Highview Power Storage, personal communication February 2013. For more detail see Appendix 1.

¹⁵
National Grid, personal communication.

¹⁶
Nitrogen liquefaction requires 549kWh/tonne (European Industrial Gases Association (EIGA), December 2010). 8,500 tonnes x 0.55MWh = 4,675MWh.

¹⁷
2.8GWh x 365 = 1,022GWh per year, or 1,022,000,000kWh. Average annual household electricity consumption is 3,300kWh. (http://www.ofgem.gov.uk/Media/FactSheets/Documents1/domestic%20energy%20consump%20
fig%20FS.pdf). 1,022,000,000 / 3,300 = 309,696.

¹⁸
We assume a small car has an energy requirement of 0.13kWh/km, on the basis that the Nissan Leaf has a 24kWh battery and range of 175km (24/175 = 0.13). At a practical energy density of 0.1kWh/kg this translates to a requirement of 1.3kg of liquid air per km for a liquid air prime mover, and 1.04kg/km for one operating with the benefit of waste heat from an ICE engine. The UK could produce 8,500T (8.5 million kg) per day of additional liquid nitrogen. At 1.3kg/km this would equate to 6.5m vehicle miles, increasing to more than 8m vehicle miles with waste heat. Cf http://www.nissan.co.uk/?cid=ps-63_296991&gclid=CIX476ulyrUCFcbKtAodfw0AbA#vehicles/electric-vehicles/electric-leaf/leaf/pricing-and-specifications/brochure.

¹⁹
http://www.stirlingcryogenics.com/stirling-cryogenics-contact/

²⁰
For example, a tank containing 60 tonnes of liquid air based with 0.5% nitrogen boil-off per day would see oxygen concentration rise by 0.1% per day. Liquid air is typically considered to be enriched at 23% oxygen. At this rate it would take about 17days to reach this level.

برچسب‌ها: liquid air

 

محققان دانشگاه میشیگان سلول خورشیدی شفافی را ابداع کرده‌اند که برخلاف نمونه‌های قبلی قابل استفاده روی پنجره‌های ساختمان نیز هست.

به گزارش گروه علم و فناوری آنا به نقل از UPI، این گروه تحقیقاتی ادعا کردند که فناوری جدیدشان جایگزین یا مکمل پنل‌های خورشیدی سقفی خواهد شد. این فناوری از فیلم نازکی از مولکول‌های ارگانیک درست شده است که طول موج‌های نامرئی نور خورشید را جذب می‌کند و طول‌موج‌های ماوراء بنفش و نزدیک به مادون قرمز را به برق تبدیل می‌کند.

این دستگاه که یک «متمرکز کننده نور لومینسان شفاف» به شمار می‌رود می‌تواند روی پنجره‌های ساختمان، شیشه جلوی ماشین یا حتی روی صفحه‌نمایش گوشی نصب شود و در این صورت، بدون اینکه خللی در دید انسان به وجود آورد، انرژی مورد نیاز برای ابزارهایی چون گوشی هوشمند را هم تامین می‌کند.

گفتنی است که قبلا هم دانشمندان چنین فناوری‌ای را تشریح کرده بودند اما محققان دانشگاه میشیگان کاربردهای یکپارچگی متمرکزکننده‌های خورشید لومینسان شفاف را در ساختارها و ابزارهای مدرن شرح داده‌اند.

دانشمندان تخمین می‌زنند که حدود 5 تا 7 میلیارد متر مربع سطح شیشه‌ای در آمریکا وجود دارد که تاکنون کاربردی در زمینه تولید برق نداشتند اما با این فناوری جدید هم‌اکنون آنها هم می‌توانند برق تولید کنند. اگر تمام این سطوح شیشه‌ای با سلول‌های خورشیدی شفاف پوشیده شوند، می‌توانند 40 درصد نیاز برقی کل آمریکا را تامین کنند.

لانت می‌گوید: «اگر بتوانیم ذخیره‌سازی انرژی را نیز بهبود بخشیم، پیاده‌سازی کاملی از هر دو تکنولوژی می‌تواند نزدیک به 100 درصد تقاضای ما را برطرف کند»

یکی از چالش‌هایی که دانشمندان در مورد این فناوری دارند این است که بهره‌وری بهترین‌ نوع پنل‌های خورشیدی حدود 15 تا 18 درصد است. در حالی که کارایی سلول‌های خورشیدی شفاف فعلا فقط پنج درصد است. اما دانشمندان بر این باورند که می‌توانند کارایی این فناوری را نیز به پنل‌های معمولی نزدیک کنند.

برچسب‌ها: ساخت سلول خورشیدی شفاف