Memahami Status Reaktor Fusi

Pada tahun 1968 ilmuwan Rusia dari Institut Kurchatov mengumumkan keberhasilan mereka mengoperasikan reaktor fusi pertama yang mereka sebut tokamak.

Kurchatov Institute of Atomic Energy, now the Kurchatov Institute Russian Research Centre.

Sukses besar tersebut mendorong negara-negara Eropa, Jepang, dan Amerika untuk membangun fasilitas riset termonuklir sendiri yang juga berbentuk tokamak, yaitu JET di Inggris, JT-60 di Jepang, dan TFTR di Princeton, Amerika. Hingga kini hampir semua reaktor fusi berbentuk tokamak.

Tokamak adalah sebuah mesin yang memproduksi medan magnet berbentuk torus untuk mengurung plasma. Alat ini merupakan salah satu bentuk dari alat pengurung plasma, dan merupakan alat yang paling banyak diteliti untuk memproduksi tenaga fusi termonuklir terkendali.

Istilah tokamak berasal dari bahasa Rusia yang merupakan singkatan dari kata Rusia "тороидальная камера в магнитных катушках" (toroidal'naya kamera v magnitnykh katushkakh) Ruang torus dengan koil magnetik atu "тороидальная камера с аксиальным магнитным полем" (toroidal'naya kamera s aksial'nym magnitnym polem) toroidal chamber with axial magnetic field.

Alat ini diciptakan pada tahun 1950-an oleh fisikawan Soviet Dr. Igor Tamm and Dr. Andrei Sakharov, inspired by an original idea of Oleg Lavrentiev.

Eksperimen pada fasilitas-fasilitas riset fusi tersebut umumnya ditujukan untuk mencapai kondisi breakeven (Q=1), sehingga sifat-sifat plasma yang didominasi oleh partikel alpha (kondisi penyalaan) belum dapat dipelajari. Sampai detik ini semua reaktor fusi masih berada dalam tahap eksperimen, masih jauh dari sisi komersial.

Versi ITER dan DEMO pun diperkirakan baru rampung pada tahun 2020 dan 2030

Meski demikian banyak kemajuan yang telah dicapai. Eksperimen terakhir pada fasilitas JET dan TFTR berhasil mempertahankan confinement dengan daya sebesar 15 MW selama kurang lebih 1 -2 detik.
Pada saat eksperimen berlangsung seluruh fasilitas eksperimen mengkonsumsi daya tak kurang 100 MW, jadi masih jauh dari titik breakeven. 

Untuk mempercepat penelitian negara-negara Eropa, Jepang, Rusia dan Amerika bergabung membangun International Thermonuclear Experimental Reactor (disingkat ITER) yang akan menjadi tokamak terbesar di dunia.

Daya keluaran reaktor ini direncanakan sebesar 500 MW. Meski dengan daya keluaran sebesar itu daya listrik yang dihasilkan dapat mencapai 150 MW, reaktor ini belum direncanakan untuk tujuan komersial.

ITER dibangun masih untuk menyelidiki efisiensi pembakaran termonuklir dan mekanisme pengendalian plasma.

ITER The Great Adventure of Fusion

Untuk tujuan ini, ITER memfokuskan diri pada pembangunan superkonduktor terbesar di dunia, penguasaan teknologi cryogenic, kerapatan tinggi, pembiakan serta penanganan tritium, pemanasan plasma, pengendalian jarak jauh, dan robotika, yang belum pernah ada sebelumnya.

Untuk skala komersial, reaktor sejenis ITER nanti akan direncanakan berdaya sekitar 4000 MW, sehingga listrik yang dapat dihasilkan cukup menjanjikan, yaitu sekitar 1000 MW.

Meski proyek ambisius ini mendapat dukungan negara-negara maju, ITER tetap saja memiliki problem internal. 

Lokasi pembangunan ITER.

 The world's largest experimental tokamak nuclear fusion reactor at the Cadarache facility in the south of France.

Sebelum reaktor dioperasikan, tritium harus disuplai dari luar. ITER harus memperoleh tritium dari negara anggotanya. Rusia dan Amerika memiliki banyak tritium, namun tentu saja mereka tidak mau membuka informasi tentang ini karena tritium dipakai sebagai pemicu bom nuklir.

Informasi jumlah tritium dapat membongkar rahasia cadangan senjata nuklir mereka. 

Banyak juga orang skeptis dengan mega proyek ini.

Bahkan, pertanyaan yang sering terlontar adalah mengapa diperlukan waktu yang sangat lama untuk membangun reaktor fusi komersial? 

Tidak dapat dipungkiri bahwa teknologi termodern sekalipun belum sanggup mempercepat kemajuan di bidang ini.

Pasalnya memang diperlukan waktu untuk riset, membangun reaktor, mendesain peralatan, serta memecahkan permasalahan yang ada. 

Di samping itu, pembangunan reaktor fusi tidak pernah menjadi prioritas seperti proyek nuklir fisi, karena reaktor fusi belum pernah dimasukkan ke dalam agenda program pertahanan negara manapun.

Jadi, tahun 2040 hingga 2050 masih merupakan prakiraan yang realistis untuk permulaan beroperasinya reaktor fusi komersial.

Bisakah Indonesia Membangun Reaktor Fusi Nuklir?

Kunjungi Juga:

National Fusion Laboratory [Sebuah Ide Pembuatan Reaktor Fusi Nuklir Riset di Indonesia] 

Semoga Bermanfaat Sobat

Indonesia Go Nuklir

Sumber:  

Prof. Dr. rer. nat. Terry Mart, M.Sc.
ITER
http://en.wikipedia.org/wiki/Fusion_power
Fisika Modern
http://www.nrcki.ru/e/engl.html
http://www.pppl.gov/

Peran Fisika untuk Lingkungan dan Konservasi Energi

Ilmu Fisika bukan hanya berkutat dengan rumus. Keberadaannya ternyata mampu berkontribusi bagi perkembangan lingkungan dan energi di bumi.

Definisi konservasi energi adalah upaya sistematis, terencana, dan terpadu guna melestarikan sumber daya energi dalam negeri serta meningkatkan efisiensi pemanfaatannya.

"Motor Tanpa Bensin, Karya Penduduk Pedalaman"

Pelaksanaan konservasi energi mencakup seluruh aspek dalam pengelolaan energi yaitu:

Penyediaan Energi 
Pengusahaan Energi 
Pemanfaatan Energi 
Konservasi Sumber Daya Energi 

Efisiensi merupakan salah satu langkah dalam pelaksanaan konservasi energi.

Efisiensi energi adalah istilah umum yang mengacu pada penggunaan energi lebih sedikit untuk menghasilkan jumlah layanan atau output berguna yang sama.

Di masyarakat umum kadang kala efisiensi energi diartikan juga sebagai penghematan energi.

1. Menggunakan lampu hemat energi, misalnya lampu neon yang lebih bersifat hemat energi daripada lampu bohlam. Di siang hari dapat menggunakan penerang alami secara optimal.

2. Membentuk perilaku dan kebiasaan diri untuk menggunakan listrik saat diperlukan, secara bergantian, dan tidak berlebihan.

3. Mematikan televisi, kran air, komputer atau lampu jika sudah tidak digunakan. Jika memungkinkan untuk mengeringkan pakaian secara alami di bawah sinar matahari.

4. Menggunakan alat rumah tangga atau kantor yang bersifat hemat energi dan ramah lingkungan, seperti pendingin ruangan dan kulkas dengan freon yang ramah lingkungan

5. Mengefisienkan pemakaian energi di tempat umum, seperti di pusat perbelanjaan, perkantoran, terminal, jalan raya, bandara, stasiun dan sebagainya.

6. Mendesain rumah atau gedung hemat energi, misalnya pencahayaan yang baik dengan cukup ventilasi, sehingga mengurangi penggunaan lampu di siang hari, mempergunakan bahan atap bangunan yang dapat mendinginkan suhu di dalam ruangan seperti atap berbahan tanah atau keramik, menaruh tanaman hias di dalam rumah untuk menyejukkan udara di dalam ruangan dan sebagainya.

7. Pemerintah meyediakan fasilitas kendaraan umum massal secara efektif dan efisien.
Pemerintah menyusun kebijakan dan memberikan penghargaan atau apresiasi positif atas segala upaya atau inovasi penghematan energi.

8. Mensosialisasikan kegiatan-kegiatan yang bersifat menghemat energi.

9. Memakai jenis pakaian yang nyaman dan sesuai dengan kondisi cuaca dan suhu udara, sehingga mengurangi penggunaan energi untuk pendingin atau pemanas ruangan

10. Mengembangkan dan melakukan penelitian untuk energi alternatif, misalnya energi biodiesel.

Semoga Bermanfaat.

Sources:

Arip Nurahman Notes
http://www.konservasienergiindonesia.info/energy
Kompas Forum
Kementrian ESDM
Masyarakat Energi Terbarukan Indonesia
https://www.coursera.org/course/globalenergy

Bahan Bakar Alternatif Potensial

Minat menggunakan bahan bakar alternatif untuk mobil atau truk yang terus tumbuh pada dasarnya dimotivasi oleh tiga pertimbangan berikut ini:

1. Bahan bakar alternatif umumnya menghasilkan lebih sedikit emisi kendaraan yang berkontribusi terhadap kabut asap, polusi udara dan pemanasan global;

2. Sebagian besar bahan bakar alternatif tidak diturunkan dari bahan bakar fosil yang merupakan sumber daya yang terbatas.

3. Bahan bakar alternatif dapat membantu negara memenuhi kebutuhan energi secara lebih mandiri.
 

"Tempat Pengisian Mobil Listrik Masa Depan Bertenaga Matahari"

Ada delapan bahan bakar alternatif yang paling potensial. Beberapa darinya sudah banyak digunakan, dan yang lainnya masih berupa bahan bakar eksperimental atau belum tersedia secara luas.

Semuanya memiliki potensi yang tinggi sebagai bahan bakar alternatif murni atau campuran untuk bensin dan diesel.

1. Etanol Sebagai Bahan Bakar Alternatif

Etanol adalah bahan bakar alternatif berbasis alkohol yang dibuat dengan cara fermentasi dan penyulingan dari tanaman seperti jagung atau gandum. Etanol dapat dicampur dengan bensin untuk meningkatkan kadar oktan bahan bakar dan meningkatkan kualitas emisi.

2. Gas Alam Sebagai Bahan Bakar Alternatif

Gas alam merupakan bahan bakar alternatif yang bersih dan sudah tersedia bagi banyak orang di banyak negara melalui berbagai fasilitas penyedia gas alam untuk di rumah dan bisnis. Ketika digunakan pada kendaraan bertenaga gas - mobil atau truk yang dirancang khusus - gas alam menghasilkan jauh lebih sedikit emisi berbahaya daripada bensin atau diesel.


3. Listrik Sebagai Bahan Bakar Alternatif

Listrik dapat digunakan sebagai bahan bakar alternatif, seperti dengan menggunakan baterai. Kendaraan listrik mendapatkan sumber tenaganya dari baterai yang dapat diisi ulang menggunakan sumber listrik standar. Bahan bakar ini menghasilkan tenaga tanpa ada pembakaran ataupun polusi, namun sebagian dari sumber tenaga ini masih tercipta dari batu bara dan meninggalkan gas karbon.

 Prof. Muhammad Nuh, MENDIKBUD dan Dr. Budi Santoso DIRUT PT. Dirgantara Indonesia

Berfoto dengan Gang Car, sebuah Mobil Listrik karya Anak Bangsa

4. Hidrogen Sebagai Bahan Bakar Alternatif

Hidrogen dapat dicampur dengan gas alam untuk membuat bahan bakar alternatif untuk kendaraan. Hidrogen juga digunakan pada kendaraan yang menggunakan listrik sebagai bahan bakarnya. Walaupun begitu, harga untuk penggunaan hidrogen masih relatif mahal.

5. Propana Sebagai Bahan Bakar Alternatif

Propana yang juga disebut sebagai bahan bakar gas cair atau LPG adalah produk sampingan dari pengolahan gas alam dan penyulingan minyak mentah. Propana sudah banyak digunakan sebagai bahan bakar untuk kegiatan memasak dan pemanas, propana juga merupakan bahan bakar alternatif yang populer bagi kendaraan. Propana menghasilkan emisi yang lebih sedikit dibandingkan bensin, dan sudah tersedia infrastruktur yang sangat maju untuk transportasi, penyimpanan dan distribusi propana.

6. Biodiesel Sebagai Bahan Bakar Alternatif

Biodiesel merupakan bahan bakar alternatif yang berbasis minyak nabati atau lemak hewan, salah satu bahkan bakunya berupa limbah minyak makan dari restoran. Mesin kendaraan dapat dikonversi untuk dapat membakar biodiesel dalam bentuk murni, dan biodiesel juga dapat dicampur dengan diesel konvensional untuk digunakan pada mesin yang tidak dimodifikasi. Biodiesel aman, biodegradable, dan dapat mengurangi polusi udara.

7. Methanol Sebagai Bahan Bakar Alternatif

Metanol juga dikenal sebagai alkohol kayu, dapat digunakan sebagai bahan bakar alternatif pada kendaraan yang didesain berbahan bakar M85, campuran 85 persen metanol dan 15 persen bensin, tapi saat ini perusahaan mobil sudah banyak yang tidak lagi memproduksi kendaraan berbahan bakar metanol. Namun, metanol bisa menjadi bahan bakar alternatif yang penting di masa depan.

8. P-Series Sebagai Bahan Bakar Alternatif

P-Series merupakan perpaduan bahan bakar etanol, gas alam cair dan methyltetrahydrofuran (MeTHF). P-Series merupakan bahan bakar yang bersih dan beroktan tinggi. Penggunaannya pun sangat mudah jika ingin dicampurkan tanpa ada proses dengan teknologi lain. Akan tetapi, hingga sekarang belum ada produsen kendaraan yang menciptakan kendaraan dengan bahan bakar fleksibel.

 Pak. Dahlan Iskan Berdialog dengan Masyarakat dalam Kereta Listrik

Sumber:

1. Kementrian ESDM
2. Indonesia Energi
3. Masyarakat Energi Terbarukan Indonesia
4. Kementrian BUMN

Kuliah Umum: Hulk dan Energi Hijau

Mark A. Ruffalo, Marco Krapels and Mark Z. Jacobson:

Power the World with Wind, Water and Sunlight



What happens when you put a movie scientist in the room with a real scientist? 

You hope to inspire millions to take part in an energy revolution!

Mark Ruffalo, known for his portrayal of Dr. Banner and the Incredible Hulk, will speak with Mark Jacobson of the Stanford Atmosphere/Energy Program and Marco Krapels of Rabobank about powering the world with wind, water and sunlight. 

Global warming, environmental pollution, and energy insecurity are three of the most significant problems facing the world today. 

This talk discusses a technical plan to solve these problems by powering 100% of the United States' and world's energy for all purposes, including electricity, transportation, industry, and heating/cooling, with wind, water, and sunlight (WWS) within 20-40 years. 

As part of the plan, we consider transmission infrastructure, resources, reliability, catastrophic risk, materials, costs, health effects, job creation, revenue streams, and policies needed. We discuss a detailed version of the plan for New York State and its potential application to California and other states. 

We also discuss the public engagement needed and how social media can help to implement the plan on the state, national, and international levels.

About the Speakers:

Mark A. Ruffalo is an Oscar-nominated actor and advocate of addressing climate change and renewable energy. In March 2011, Mark co-founded Water Defense to raise awareness about energy extraction impact on water and the public health.

A regular contributor to the Guardian and the Huffington Post, Mark is a recent recipient of the Global Green Millennium Award for Environmental Leadership, and the Meera Gandhi Giving Back Foundation Award. He was named one of Time Magazine's "People Who Mattered" in 2011. Most recently, he played Dr. Banner and the Incredible Hulk in the box-office hit, The Avengers. 

Marco Krapels is the Executive Vice President of Rabobank N.A,,where he runs the commercial banking product groups including its capital markets and renewable energy finance divisions.

He co-chairs the bank's Corporate Social Responsibility (CSR) committee, where he's initiated notable sustainability efforts, including a Rabobank solar/Tesla electric car project featured in the New York Times.

Marco is co-founder and board member of Empowered by Light, which promotes renewable energy solutions for 1.6 billion people living without electricity.

http://empoweredbylight.org/

Prof. Mark Z. Jacobson is Director of the Atmosphere/Energy Program and Professor of Civil and Environmental Engineering at Stanford University. He is also a Senior Fellow of the Woods Institute for the Environment and Senior Fellow of the Precourt Institute for Energy.

He is on the Energy Efficiency and Renewables Advisory Committee to the U.S. Secretary of Energy. He co-authored a 2009 cover article in Scientific American and two more recent articles in Energy Policy with Dr. Mark DeLucchi of U.C. Davis on how to power the world with renewable energy.

 

Professor of Civil and Environmental Engineering

Director, Atmosphere/Energy Program
Senior Fellow,  Woods Institute for the Environment
Senior Fellow, Precourt Institute for Energy

Education: 

B.S. Civil Engineering B.A. Economics and M.S. Environmental Engineering(1988) Stanford University
M.S. (1991) and Ph.D. (1994) Atmospheric Science, University of California at Los Angeles

Kunjungi Web Pribadinya di:

http://www.stanford.edu/group/efmh/jacobson/

https://twitter.com/mzjacobson 

"Bahan bakar fosil suatu saat PASTI AKAN HABIS, dan kita harus mempersiapkan diri sebelum itu terjadi. Konservasi Energi, Hemat Energi, Energi Terbarukan dan Energi Hijau adalah pilihan-pilihan yang harus kita ambil, mari kita mulai hari ini."

*A.N.*

Semoga Bermanfaat

Sumber: 

1. Google Talk
2. The Avengers
3. Stanford University
4. Empowered by Light
5. http://www.meti.or.id/
[Masyarakat Energi Terbarukan Indonesia]

Solar Power Satellite VII

"Antariksa adalah kebun yang dipenuhi oleh buah-buahan Energi yang begitu melimpah ruah, bisakah umat manusia memanennya?" 

*A.N*

Defending solar power satellites:

Solar power satellites would normally be at a high orbit that is difficult to reach, and hence attack.

However, it has been suggested that a large enough quantity of granular material placed in a retrograde orbit at the geostationary altitude could theoretically completely destroy these kinds of system and render that orbit useless for generations.

Whether this is a realistic attack scenario is arguable, and in any case at the present time there is only a small list of countries with the necessary launch capability to do this, such an attack would probably be considered an act of war by every single nation (except the attacker, which would lose its satellites, too) with satellites in geostationary orbit, and an attack with more conventional anti-satellite weapons would probably be considered an act of war by the nation whose satellite was attacked.

In any case, the receiving stations on the ground, and conventional power generators (which are unlikely to be completely replaced by solar power satellites), are more easily attacked.

Computer security may be a bigger issue than physical defense, since launch capabilities aren't necessary to hack a satellite for purposes of malicious orbital "corrections", extortion (by threatening to destabilize its orbit) or outright "grand theft satellite".

http://www.niac.usra.edu/

Proyek ini merupakan bagian dari penelitian Institute for Advanced Concepts NASA (NIAC) yang dipimpin oleh Dr John Mankins dari Artemis Innovation. The University of Strathclyde mewakili konsorsium internasional Eropa yang melibatkan para peneliti dari Amerika dan sebuah tim dari Jepang yang dipimpin oleh Profesor Nobuyuki Kaya dari Universitas Kobe, yang saat ini merupakan acuan dunia dalam teknologi wireless power transmission (transmisi energy tanpa kabel).

Penelitian yang dilakukan NIAC ini menunjukkan desain konseptual baru untuk satelit tenaga surya skala besar. Peran tim dari University of Strathclyde adalah untuk mengembangkan solusi inovatif pada elemen struktural dan solusi baru untuk mengorbitkan satelit sel surya dan kontrol orbitnya.

Kunjungi Juga:

• Space Solar Power - from the Space Development Steering Committee
• Space Solar Power - An Earth to Orbit Challenge - from NASA Kennedy Space Center
• Space Solar Power Disaster Relief - Online Journal of Space Communication, Ohio University
• Space Solar Power Info - News and Blog by QualityPoint Technologies (India)
• Space Solar Power Information Service
• Space Solar Power Institute - solarsat.org
• Space Solar Power (SSP) - A Solution for Energy Independence & Climate Change - position paper submitted to the Obama-Biden Transition Team at Change.gov, with public comments
• Space Solar Power Workshop
• SSP Monitor

Lihat Juga:

Indonesian Space Sciences & Technology School

Indonesian University Space Research Association

Semoga Bermanfaat.

The End

Ketika "Hulk" Bicara Energi Hijau

Mark Ruffalo Visits Stanford to Talk Clean Energy



Life imitated art when MARK RUFFALO, the actor who plays scientist Dr. Bruce Banner (aka “The Hulk”) in the blockbuster film The Avengers, came to Stanford University.

The Oscar-nominated actor/director teamed up with Mark Jacobson, a real-life scientist and senior fellow with the Stanford Woods Institute for the Environment and the Precourt Institute for Energy, for an informal discussion with students about a nascent initiative to convert the world to renewable energy.

The talk was part of a series of planned dialogues Ruffalo and Jacobson had with Stanford students and staff at companies such as Google, Facebook and Tesla Motors. Joining Ruffalo and Jacobson were clean energy advocates Marco Krapels, executive vice president of Rabobank, and Jon Wank, co-president of Skadaddle Media.

Dr. Bruce Banner: "So he's building another portal. That's what he needs Erik Selvig for."
Thor: "Selvig?"
Dr. Bruce Banner: "He is an astrophysicist." 
Thor: "He is friend"

Mark Alan Ruffalo (born November 22, 1967) is an American actor, director, producer and screenwriter. Known for portraying Marvel Comics character Bruce Banner / The Hulk in Marvel's The Avengers (2012), he has also starred in films such as You Can Count on Me (2000), Collateral (2004), Eternal Sunshine of the Spotless Mind (2004), Just Like Heaven (2005), Zodiac (2007), and Shutter Island (2010).

For his role in The Kids Are All Right (2010), he received an Academy Award nomination for Best Supporting Actor.

“It’s the right time for this,” Ruffalo told the 30 or so audience members, most of them students in the Atmosphere/Energy Program Jacobson heads in the Department of Civil and Environmental Engineering. People are more aware of and more ready than ever to grapple with climate and energy problems, Ruffalo said, adding, “Now we’re able to talk about it without going through a centralized media.”

Ruffalo explained that his interest in creating a roadmap to repower the energy infrastructure with clean energy began when he moved to upstate New York a few years ago and learned about hydrofracking, a polluting natural gas extraction method used in the region. “It sounded more and more like a nightmare,” he said.

Local involvement around the hydrofracking issue led to a broader engagement in the sustainability movement for Ruffalo, who has been speaking out to his social media followers and the blogosphere about the need for clean energy. Ruffalo connected with Jacobson and Josh Fox, the director of the 2010 fracking documentary Gasland, at an event in San Francisco last year.
 

Apa Itu Energi Hijau?

Definisi energi hijau paling sederhana adalah energi yang dihasilkan dari sumber energi yang lebih ramah lingkungan (atau "hijau") dibandingkan dengan bahan bakar fosil (batubara, minyak, dan gas alam). Karena itulah energi hijau mencakup semua sumber energi terbarukan (surya, angin, panas bumi, biofuel, tenaga air), dan menurut definisi juga harus mencakup energi nuklir meskipun ada banyak penggiat lingkungan yang menentang gagasan mengenai energi nuklir masuk ke dalam energi hijau karena nuklir memiliki masalah limbah, dan efeknya yang berbahaya terhadap lingkungan.

Terminologi energi hijau diciptakan untuk memisahkan bahan basar fosil yang mengakibatkan tingkat polusi yang tinggi dengan bahan bakar lainnya yang mengakibatkan polusi lebih rendah dan ramah lingkungan seperti pada sumber energi terbarukan. Perubahan iklim telah menjadi ancaman global, dan dunia perlu menemukan pilihan energi bersih (lebih sedikit emisi), dan dengan demikian energi hijau penting untuk terus berkembang.

 Para Avengers Berkumpul

The three had an in-depth conversation about Jacobson’s work with Mark DeLucchi at the University of California-Davis to develop a global renewable energy plan. The plan – featured on the cover of Scientific American is a blueprint for building an energy grid based only on clean sources such as solar, wind and hydroelectric. This grid, not subject to price fluctuations, would eliminate energy insecurity, air pollution and global warming.

Following that dinner conversation, Ruffalo, Jacobson, Fox and researchers at Cornell University began reaching out to other scientists, business people and cultural figures to further develop a roadmap for repowering the world. The effort would galvanize support for a clean-energy economy at state, national and, eventually, global levels. Jacobson described it as a “grand vision” involving science, economics, policy, finance, multimedia and activism. Ruffalo and Jacobson wrote about their vision in the Huffington Post earlier this month.

The next step will focus on informing policymakers about viable options for converting to a clean-energy economy, Jacobson told the Stanford audience. Beyond that crucial component, the way forward will not have to depend on good intentions alone, he added. “This will be driven a lot by people who want to make money,” he said of developers interested in building renewable energy infrastructure. Krapels echoed that sentiment, saying that Rabobank, the world’s largest agricultural bank, is interested in how renewable energy can save money for its clients. “We’ve been looking at this very much from a business perspective.”

During a question-and-answer session, students offered suggestions for connecting with college students, ranging from campus advocates to conferences.

One student’s suggestions of imitating a Stanford/NASA teacher-training partnership elicited particular interest from the speakers.

 "The Iron Man and The Hulk Together"

Energi hijau masih tidak cukup kuat untuk bersaing dengan bahan bakar fosil. Hal ini terutama karena energi hijau masih menjadi pilihan energi yang secara signifikan lebih mahal dibandingkan dengan bahan bakar fosil, dan dengan demikian banyak negara, terutama negara berkembang, tetap menggunakan bahan bakar fosil yang lebih murah seperti batubara.

Istilah energi hijau tidak hanya mencakup sumber energi terbarukan tetapi dapat diperluas untuk mencakup konservasi energi (contohnya energi hijau juga dipakai untuk menyebut bangunan yang dibangun dengan cara agar tetap dingin di siang hari dan tetap panas di malam hari melalui desain arsitektur yang tidak mengandalkan AC atau sistem pemanas ruangan).

Promosi energi hijau tidak hanya dengan menggunakan sumber energi terbarukan di tahun-tahun mendatang, tetapi juga untuk membuat dominasi teknologi bahan bakar fosil saat ini menjadi lebih hijau dan mengurangi tingkat polusi (seperti teknologi batubara bersih).

Istilah energi hijau kadang-kadang diidentifikasikan dengan istilah energi berkelanjutan, tetapi hal ini tidak sepenuhnya benar karena energi yang berkelanjutan juga mencakup teknologi untuk meningkatkan efisiensi energi. Energi hijau tidak mengacu pada efisiensi sumber energi terbarukan tetapi hanya menekankan pada dampak positif mereka terhadap lingkungan (dibandingkan dengan bahan bakar fosil).

Mari kita kembangkan Energi Hijau, kalau "Hulk" saja peduli, apa lagi kita?

Semoga Bermanfaat

Sources:

1. Stanford University
2. The Avengers 
3. Indonesia Energi
4. www.meti.or.id/
[Masyarakat Energi Terbarukan Indonesia]

Solar Power Satellite VI

Percobaan yang dikenal dengan nama Suaineadh (yang artinya ‘memutar’ dalam bahasa Gaelic skotlandia) merupakan langkah maju yang penting dalam desain konstruksi luar angkasa dan menunjukkan bahwa struktur yang lebih besar dapat dibangun di atas sebuah jaring ringan yang berputar.

Hal tersebut akan membuka jalan untuk tahap berikutnya dalam proyek tenaga surya luar angkasa.

Dr. Vasile menambahkan:

“Keberhasilan Suaineadh memungkinkan proyek kami  bergerak maju pada tahap berikutnya, dimana akan melibatkan reflektor yang diperlukan untuk mengumpulkan tenaga surya."

“Proyek yang diberi nama SAM (Self-inflating Adaptable Membrane) ini akan menguji peluncuran struktur selular sangat ringan yang dapat berubah bentuk pada saat diluncurkan."

Struktur terbuat dari sel-sel yang dapat menggembungkan diri dalam ruang hampa udara dan dapat mengubah volumenya sendiri melalui nanopumps (pompa nano).

“Struktur tersebut meniru struktur selular alami yang ada pada semua makhluk hidup. Kontrol independen dari sel akan memungkinkan kita untuk merubah struktur menjadi konsentrator surya yang akan mengumpulkan sinar matahari dan memproyeksikannya pada rangkaian sel surya surya. Struktur yang sama dapat digunakan untuk membangun sistem ruang angkasa yang besar dengan merakit ribuan unit individu kecil.”

Lofstrom launch loop

A Lofstrom loop could conceivably provide the launch capacity needed to make a solar power satellite practical. This is a high capacity launch system capable of reaching a geosynchronous transfer orbit at low cost (Lofstrom estimates a large system could go as low as $3/kg to LEO for example). The Lofstrom loop is expected to cost less than a conventional space elevator to develop and construct, and to provide lower launch costs. Unlike the conventional space elevator, it is believed that a launch loop could be built with today’s materials.

Space elevators

More recently the SPS concept has been suggested as a use for a space elevator. The elevator would make construction of an SPS considerably less expensive, possibly making them competitive with conventional sources.

However it appears unlikely that even recent advances in materials science, namely carbon nanotubes, can make possible such an elevator, nor to reduce the short term cost of construction of the elevator enough, if an Earth-GSO space elevator is ever practical. A variant to the Earth-GSO elevator concept is the Lunar space elevator, first described by Jerome Pearson in 1979.

Because of the ~20 times shallower (than Earth's) gravitational well for the lunar elevator, this concept would not rely on materials technology beyond the current state of the art, but it would require establishing silicon mining and solar cell manufacturing facilities on the Moon, similar to O'Neill's lunar material proposal, discussed above.

Safety

The use of microwave transmission of power has been the most controversial issue in considering any SPS design, but any thought that anything which strays into the beam's path will be incinerated is an extreme misconception. Consider that quite similar microwave relay beams have long been in use by telecommunications companies world wide without such problems.

At the earth's surface, a suggested microwave beam would have a maximum intensity, at its center, of 23 mW/cm² (less than 1/4 the solar irradiation constant), and an intensity of less than 1 mW/cm² outside of the rectenna fenceline (10 mW/cm² is the current United States maximum microwave exposure standard).

In the United States, the workplace exposure limit (10 mW/cm²) is at present, per the Occupational Safety and Health Act (OSHA), expressed in voluntary language and has been ruled unenforceable for Federal OSHA enforcement.

The beam's most intense section (more or less, at its center) is far below dangerous levels even for an exposure which is prolonged indefinitely. Furthermore, exposure to the center of the beam can easily be controlled on the ground (eg, via fencing), and typical aircraft flying through the beam provide passengers with a protective shell metal (ie, a Faraday Cage), which will intercept the microwaves.

Other aircraft (balloons, ultra-light, etc) can avoid exposure by observing airflight control spaces, as is currently done for military and other controlled airspace. Over 95% of the beam energy will fall on the rectenna. The remaining microwave energy will be absorbed and dispersed well within standards currently imposed upon microwave emissions around the world.

The microwave beam intensity at ground level in the center of the beam would be designed and physically built into the system; simply, the transmitter would be too far away and too small to be able to increase the intensity to unsafe death ray levels, even in principle.

In addition, a design constraint is that the microwave beam must not be so intense as to injure wildlife, particularly birds. Experiments with deliberate microwave irradiation at reasonable levels have failed to show negative effects even over multiple generations.

Some have suggested locating rectennas offshore, but this presents serious problems, including corrosion, mechanical stresses, and biological contamination.

Phased array transmission was originally developed in 1905 by Nobel Physics Laureate Karl Ferdinand Braun who demonstrated enhanced transmission of radio waves in one direction.

A commonly proposed approach to ensuring fail-safe beam targeting is to use a retrodirective phased array antenna/rectenna. A "pilot" microwave beam emitted from the center of the rectenna on the ground establishes a phase front at the transmitting antenna. There, circuits in each of the antenna's subarrays compare the pilot beam's phase front with an internal clock phase to control the phase of the outgoing signal.

This forces the transmitted beam to be centered precisely on the rectenna and to have a high degree of phase uniformity; if the pilot beam is lost for any reason (if the transmitting antenna is turned away from the rectenna, for example) the phase control value fails and the microwave power beam is automatically defocused Such a system would be physically incapable of focusing its power beam anywhere that did not have a pilot beam transmitter.

It is important for system efficiency that as much of the microwave radiation as possible be focused on the rectenna. Outside of the rectenna, microwave intensities would rapidly decrease, so nearby towns or other human activity should be completely unaffected.

The long-term effects of beaming power through the ionosphere in the form of microwaves has yet to be studied, but nothing has been suggested which might lead to any significant effect.

Lihat Juga:


Indonesian Space Sciences & Technology School

Indonesian University Space Research Association

Kunjungi Juga:

• Space Based Solar Power - Wikipedia
• Space Canada - Solar Power Alternative for Clean Energy
• Space Energy Corporation
• Space Environment Technologies: The Vision for Producing Fresh Water Using Space Solar Power
• Spacefaring America: Space Solar Power - Mike Snead's weblog includes extensive articles on Space Solar Power and America's Future
• SpaceFuture.com Space Power section

Semoga Bermanfaat.

To Be Continued 

Solar Power Satellite V

Dr. Massimiliano Vasile, dari Departemen Mechanical and Aerospace Engineering, University of Strathclyde, di UK yang memimpin penelitian energi surya ini, mengatakan, “Luar angkasa menyediakan sumber energi yang fantastis untuk mengumpulkan tenaga surya dan kami memiliki keuntungan dapat mengumpulkan energi itu terlepas dari siang ataupun malam dan kondisi cuaca."

Mahasiswa Ph.D. Thomas Sinn (kiri) dan Dr. Massimiliano Vasile (kanan) dengan prototipe satelit uji.

Pada daerah seperti gurun Sahara di mana tenaga surya yang berkualitas dapat ditangkap, akan sangat sulit untuk mendistribusikan energi tersebut ke daerah dimana energi tersebut dapat digunakan. Namun, penelitian ini berfokus pada bagaimana kita dapat menghapus kendala ini dan menggunakan sel surya berbasis ruang angkasa untuk mengirimkan energi ke daerah-daerah yang sulit dijangkau. 

“Dengan menggunakan gelombang mikro atau laser kita memancarkan energy kembali ke bumi dan langsung menuju ke daerah tertentu.", Kata mereka.

Hal ini akan menyediakan sumber energi berkualitas yang dapat diandalkan dan akan menghilangkan kebutuhan untuk menyimpan energi yang berasal dari sumber terbarukan di tanah. Platform ini akan menyediakan pengiriman energi surya yang konstan.

"Awalnya, satelit yang lebih kecil akan dapat menghasilkan energi yang cukup untuk sebuah desa kecil akan tetapi dengan teknologi yang tersedia sekarang, kami memiliki tujuan, untuk pada suatu hari menempatkan struktur yang cukup besar pada ruang angkasa untuk mengumpulkan energi yang akan mampu memberikan daya bagi kota besar.", jelas mereka.

Di tahun-tahun yang lalu, sebuah tim ilmuwan dan mahasiswa teknik di Strathclyde mengembangkan percobaan inovatif ‘space web’ yang dibawa oleh roket dari Lingkaran Arktik menuju batas ruang angkasa dengan bumi. 

Advantages of an SPS:

The SPS concept is attractive because space has several major advantages over the Earth's surface for the collection of solar power. There is no air in space, so the collecting surfaces would receive much more intense sunlight, unaffected by weather. In geostationary orbit, an SPS would be illuminated over 99% of the time. The SPS would be in Earth's shadow on only a few days at the spring and fall equinoxes; and even then for a maximum of 75 minutes late at night when power demands are at their lowest.

This characteristic of SPS based power generation systems to avoid the expensive storage facilities (eg, lakes behind dams, oil storage tanks, coal dumps, etc) necessary in many Earth-based power generation systems. Additionally, an SPS will have none of the polluting consequences of fossil fuel systems, nor the ecological problems resulting from many renewable or low impact power generation systems (eg, dam retention lakes).

Economically, an SPS deployment project would create many new jobs and contract opportunities for industry, which may have political implications in the country or region which undertakes the project. Certainly the energy from an SPS would reduce political tension resulting from unequal distribution of energy supplies (eg, oil, gas, etc). For nations on the equator, SPS provides an incentive to stabilise and a sustained opportunity to lease land for launch sites.

An SPS would also be applicable on a global scale. Nuclear power especially is something many governments would be reluctant to sell to developing nations in which political pressures might lead to proliferation. Whether bio-fuels can support the western world, let alone the developed world, is currently a matter of debate. SPS poses no such problems.

Developing the industrial capacity needed to construct and maintain one or more SPS systems would significantly reduce the cost of other space endeavours. For example, a manned Mars mission might only cost hundreds of millions, instead of tens of billions, if it can rely on an already existing capability.

More long-term, the potential power production possible is enormous. If power stations can be placed outside Earth orbit, the upper limit is vastly higher still. In the extreme, such arrangements are called Dyson spheres.

Other web pages devoted to SSP (alphabetical)

• Citizens for Space Based Solar Power
• Connecting the Dots to Future Electric Power - Dr. Edward J. Blair, Indiana University
• EADS Astrium: Space Based Solar Power: innovating for clean energy
• International SunSat Design Competition
• International Collegiate Solar Power Satellite Design Competition
• Japanese Aerospace Exploration Agency (JAXA): Practical Application of Space-Based Solar Power Generation
• Mitsubishi Electric: How Solarbird Works
• Moon Society Solar Power Beaming Desktop Demo Unit Online Kit
• Orbital Power Corporation
• PowerSat Corporation
• Research and Markets: Analyzing Microwave Power Transmission & Solar Power Satellite Systems (expensive report dated October 2009; we have not seen it)
• Research and Markets: Microwave Power Transmission Market Potential (expensive report dated July 2008; outstanding detailed report; current availability unknown)
• Solar High - Energy for the 21st Century
• Space-Based Solar Power - Public discussion of 2007 National Security Space Office study of space solar power

Kunjungi Juga:

Pusat Teknologi Satelit - Lembaga Penerbangan dan Antariksa Nasional

Semoga Bermanfaat.


To Be Continued

Solar Power Satellite IV

Satelit Sel Surya, Teknologi Penyuplai Sumber Energi Terbarukan Di Masa Depan: 

Tenaga surya yang dikumpulkan di luar angkasa dapat digunakan untuk menyediakan energi terbarukan di masa depan. Hal tersebut kemungkinan dapat terjadi berkat penelitian inovatif yang dilakukan oleh para insinyur di University of Strathclyde di Glasgow. 

Para peneliti dari University of Strathclyde telah menguji peralatan ruang angkasa yang akan menyediakan platform untuk panel surya yang akan mengumpulkan energi dan kemudian ditransfer ke bumi ditransfer kembali ke bumi melalui gelombang mikro atau laser.

Panel Surya tersebut akan menjadi sumber energi yang dapat diandalkan dan memungkinkan mengirimkan energi ke daerah terpencil di dunia, misalnya seperti memberikan daya ke daerah bencana atau daerah terpencil yang sulit dijangkau dengan cara tradisional. 

Problems:

Launch costs 

Without doubt, the most obvious problem for the SPS concept is the current cost of space launches. Current rates on the Space Shuttle run between $3,000 and $5,000 per pound ($6,600/kg and $11,000/kg) to low Earth orbit, depending on whose numbers are used. Calculations show that launch costs of less than about $180-225 per pound ($400-500/kg) to LEO (Low Earth orbit) seem to be necessary.

However, economies of scale for expendable vehicles could give rather large reductions in launch cost for this kind of launched mass. Thousands of rocket launches could very well reduce the costs by ten to twenty times, using standard costing models. This puts the economics of an SPS design into the practicable range. Reusable vehicles could quite conceivably attack the launch problem as well, but are not a well-developed technology.

Much of the material launched need not be delivered to its eventual orbit immediately, which raises the possibility that high efficiency (but slower) engines could move SPS material from LEO to GEO at acceptable cost. Examples include ion thrusters or nuclear propulsion. They might even be designed to be reusable.

Power beaming from geostationary orbit by microwaves has the difficulty that the required 'optical aperture' sizes are very large. For example, the 1978 NASA SPS study required a 1-km diameter transmitting antenna, and a 10 km diameter receiving rectenna, for a microwave beam at 2.45 GHz. These sizes can be somewhat decreased by using shorter wavelengths, although they have increased atmospheric absorption and even potential beam blockage by rain or water droplets.

Because of the thinned array curse, it is not possible to make a narrower beam by combining the beams of several smaller satellites. The large size of the transmitting and receiving antennas means that the minimum practical power level for an SPS will necessarily be high; small SPS systems will be possible, but uneconomic.

To give an idea of the scale of the problem, assuming an (arbitrary, as no space-ready design has been adequately tested) solar panel mass of 20 kg per kilowatt (without considering the mass of the supporting structure, antenna, or any significant mass reduction of any focusing mirrors) a 4 GW power station would weigh about 80,000 metric tons, all of which would, in current circumstances, be launched from the Earth.

Very lightweight designs could likely achieve 1 kg/kW, meaning 4,000 metric tons for the solar panels for the same 4 GW capacity station. This would be the equivalent of between 40 and 80 heavy-lift launch vehicle (HLLV) launches to send the material to low earth orbit, where it would likely be converted into subassembly solar arrays, which then could use high-efficiency ion-engine style rockets to (slowly) reach GEO (Geostationary orbit).

With an estimated serial launch cost for shuttle-based HLLVs of $500 million to $800 million, total launch costs would range between $20 billion (low cost HLLV, low weight panels) and $320 billion ('expensive' HLLV, heavier panels).

Economies of scale on such a large launch program could be as high as 90% (if a learning factor of 30% could be achieved for each doubling of production) over the cost of a single launch today. In addition, there would be the cost of an assembly area in LEO (which could be spread over several power satellites), and probably one or more smaller one(s) in GEO. The costs of these supporting efforts would also contribute to total costs.

So how much money could an SPS be expected to make? For every one gigawatt rating, current SPS designs will generate 8.75 terawatt-hours of electricity per year, or 175 TW•h over a twenty-year lifetime. With current market prices of $0.22 per kW•h (UK, January 2006) and an SPS's ability to send its energy to places of greatest demand (depending on rectenna siting issues), this would equate to $1.93 billion per year or $38.6 billion over its lifetime.

The example 4 GW 'economy' SPS above could therefore generate in excess of $154 billion over its lifetime. Assuming facilities are available, it may turn out to be substantially cheaper to recast on-site steel in GEO, than to launch it from Earth. If true, then the initial launch cost could be spread over multiple SPS lifespans.

"Ilmu Pengetahuan dan Teknologi Canggih dapat kita kuasai bersama asal kita dapat bekerja bersama-sama"

~A.N.~

Extraterrestrial materials

Gerard O'Neill, noting the problem of high launch costs in the early 1970s, proposed building the SPS's in orbit with materials from the Moon. Launch costs from the Moon are about 100 times lower than from Earth, due to the lower gravity. This 1970s proposal assumed the then-advertised future launch costing of NASA's space shuttle. This approach would require substantial up front capital investment to establish mass drivers on the Moon.

Nevertheless, on 30 April 1979, the Final Report ("Lunar Resources Utilization for Space Construction") by General Dynamics' Convair Division, under NASA contract NAS9-15560, concluded that use of lunar resources would be cheaper than terrestrial materials for a system of as few as thirty Solar Power Satellites of 10GW capacity each.

In 1980, when it became obvious NASA's launch cost estimates for the space shuttle were grossly optimistic, O'Neill et al published another route to manufacturing using lunar materials with much lower startup costs This 1980s SPS concept relied less on human presence in space and more on partially self-replicating systems on the lunar surface under telepresence control of workers stationed on Earth. Again, this proposal suffers from the current lack of such automated systems on Earth, much less on the Moon.

Asteroid mining has also been seriously considered. A NASA design study evaluated a 10,000 ton mining vehicle (to be assembled in orbit) that would return a 500,000 ton asteroid 'fragment' to geostationary orbit. Only about 3000 tons of the mining ship would be traditional aerospace-grade payload. The rest would be reaction mass for the mass-driver engine; which could be arranged to be the spent rocket stages used to launch the payload.

Assuming, likely unrealistically, that 100% of the returned asteroid was useful, and that the asteroid miner itself couldn't be reused, that represents nearly a 95% reduction in launch costs. However, the true merits of such a method would depend on a thorough mineral survey of the candidate asteroids; thus far, we have only estimates of their composition. There has been no such survey. Once built, NASA's CEV should be capable of beginning such a survey, Congressional money and imagination permitting.

"Kita harus kembali ke dasar pembangunan, BACK TO BASIC!, untuk penghematan Energi, jangan segan kembali ke hal-hal bermanfaat yg sudah disediakan oleh pemerintah sebelumnya. Pernah dibuat prototipe kapal yg memanfaatkan energi angin, energi sinar matahari, jangan disia-siakan."

Kunjungi Juga:


Indonesian Space Sciences & Technology School

Indonesian University Space Research Association


Semoga Bermanfaat

To Be Continued

Mengenal Alat-Alat Penukar Kalor: Heat Exchanger

Suatu alat penting yang memiliki banyak aplikasi dalam engineering adalah alat penukar kalor. Alat penukar kalor digunakan untuk memindahkan energi dari sebuah benda panas ke benda yang lebih dingin atau ke lingkungannya melalui perpindahan kalor. 

 

Energi ditransfer dari gas-gas panas setelah terjadi pembakaran dalam sebuah pembangkit daya ke air yang mengalir di dalam pipa-pipa boiler dan dari air panas yg keluar dari sebuah mesin mobil ke atmosfer, dan generator-generator listrik didinginkan melalui air yg mengalir melalui saluran-saluran internal. 

Dalam Industri:

Heat exchangers are widely used in industry both for cooling and heating large scale industrial processes. The type and size of heat exchanger used can be tailored to suit a process depending on the type of fluid, its phase, temperature, density, viscosity, pressures, chemical composition and various other thermodynamic properties.

In many industrial processes there is waste of energy or a heat stream that is being exhausted, heat exchangers can be used to recover this heat and put it to use by heating a different stream in the process. This practice saves a lot of money in industry, as the heat supplied to other streams from the heat exchangers would otherwise come from an external source that is more expensive and more harmful to the environment.

Heat exchangers are used in many industries, including:

• Waste water treatment
• Refrigeration
• Wine and beer making
• Petroleum refining

In waste water treatment, heat exchangers play a vital role in maintaining optimal temperatures within anaerobic digesters to promote the growth of microbes that remove pollutants. Common types of heat exchangers used in this application are the double pipe heat exchanger as well as the plate and frame heat exchanger.

Dalam Penerbangan:

 

In commercial aircraft heat exchangers are used to take heat from the engine's oil system to heat cold fuel. This improves fuel efficiency, as well as reduces the possibility of water entrapped in the fuel freezing in components.

Early 2008, a Boeing 777 flying as British Airways Flight 38 crashed just short of the runway. In an early-2009 Boeing-update sent to aircraft operators, the problem was identified as specific to the Rolls-Royce engine oil-fuel flow heat exchangers. Other heat exchangers, or Boeing 777 aircraft powered by GE or Pratt and Whitney engines, were not affected by the problem.

 Lihat Juga:

• Architectural engineering
• Chemical engineering
• Cooling tower
• Copper in heat exchangers
• Heat pipe
• Heat pump
• Heat recovery ventilation
• Jacketed vessel
• Log mean temperature difference (LMTD)
• Mechanical engineering
• Micro heat exchanger
• Moving bed heat exchanger

• Packed bed and in particular Packed columns
• Pumpable ice technology
• Reboiler
• Recuperator, or cross plate heat exchanger
• Regenerator
• Run around coil
• Steam generator (nuclear power)
• Surface condenser
• Toroidal expansion joint
• Thermosiphon
• Thermal wheel, or rotary heat exchanger (including enthalpy wheel and desiccant wheel)
• Waste heat

Sumber:

Arip Nurahman Notes

Wikipedia

Solar Power Satellite III

Satelit tenaga surya adalah satelit yang diusulkan dibuat di orbit Bumi tinggi yang menggunakan transmisi tenaga gelombang mikro untuk menyorotkan tenaga surya kepada antena sangat besar di Bumi yang dpaat digunakan untuk menggantikan sumber tenaga konvensional.

Working lifetime:

The lifetime of a PV based SPS is limited mainly by the ionizing radiation from the radiation belts and the Sun. Without a protection method, this is likely to cause the cells to degrade by about a percent or two per year. Deterioration is likely to be more rapid during periods of high exposure to energetic protons from solar particle outburst events. If some practical protection can be designed, this also might be reducible (eg, for a CPV station, radiation and particle shields for the PV cells out of the energy path from the mirrors, of course).

Lifetimes for SD based SPS designs will be similarly limited, though largely for structural or mechanical considerations, such as micrometeorite impact, metal fatigue of turbine blades, wear of sliding surfaces (although this might be avoidable by hydrostatic bearings or magnetic bearings), degradation or loss of lubricants and working fluids in vacuum, from loss of structural integrity leading to impaired optical focus amongst components, and from temperature variation extremes.

As well, most mirror surfaces will degrade from both radiation and particle impact, but such mirrors can be designed simply (and so to be light and cheap), and replacement may be practical.

In either case, another advantage of the SPS design is that waste heat developed at collection points is re-radiated back into space, instead of warming the adjacent local biosphere as with conventional sources, though some care will likely be required to provide for the radiation of this waste heat.

Thus thermal efficiency will not be in itself an important design parameter except insofar as it affects the power/weight ratio via operational efficiency and hence pushes up launch costs. (For example SD may require larger waste heat radiators when operating at a lower efficiency).

Earth based power handling systems must always be carefully designed, for both economic and purely engineering reasons, with operational thermal efficiency in mind.

One useful aspect of the SPS approach is that, at the end of life, the material does not need to be launched a second time, at least in principle. In theory, it would be possible to recycle much of the satellite 'on-site', potentially at a significantly lower cost than launching an SPS as new.

This might allow a very expensive launch cost to be paid for over multiple satellite lifetimes, but does require an in orbit re-processing facility which doesn't currently exist.

Energy Payback:

Clearly, for an SPS system (including manufacture, launch and deployment) to provide net power it must repay the energy needed to construct it.

Solar satellites can pay back the lift energy in a remarkably short time. It takes 14.75 kWh/kg for a 100% efficiency system to lift a kg from the surface of the earth to GEO; no such launch system exists and so energy costs are always higher. If the satellite generated a kW with 2kg of mass, the payback time would be 29.5 hours. Assuming a much less efficient (and more realistic) 3% efficient rockets, the energy payback time is only extended to about 6 weeks for such an SPS.

For current silicon PV panels, production energy requirements are relatively high, and typically three-four years of deployment in a terrestrial environment is needed to recover this energy.

With SPS, net energy received on the ground is higher (more or less necessarily so, if the system to be worth deploying), so this energy payback period would be reduced to about a year. Thermal systems, being made of conventional materials, are more similar to conventional power stations and are likely to be less energy intensive during manufacture. They would be expected to give quicker energy break even, depending on construction technology. The relative merits of PV vs SD is still an open question.

Clearly, for a system (including manufacture, launch and deployment) to provide net power it must repay the energy needed to construct it. For current silicon PV panels this is relatively high. With an SPS, the net energy received on the ground is higher so this energy payback period would be somewhat reduced; however an SD based SPS, being made of conventional materials, are more similar to conventional powerstations and are likely to be less energy intensive during production and would be expected to give a quicker energy break even, depending on construction technology and other variations.

Wireless power transmission to the Earth:

Wireless power transmission was early proposed to transfer energy from collection to the Earth's surface. The power could be transmitted as either microwave or laser radiation at a variety of frequencies depending on system design. Whatever choice is made, the transmitting radiation would have to be non-ionizing to avoid potential disturbances either ecologically or biologically if it is to reach the Earth's surface. This established an upper bound for the frequency used, as energy per photon, and so the ability to cause ionization, increases with frequency. Ionization of biological materials doesn't begin until ultraviolet or higher frequencies so most radio frequencies will be acceptable for this.

William C. Brown demonstrated in 1964 (on air Walter Cronkite's CBS News program), a microwave-powered model helicopter that received all the power it needed for flight from a microwave beam. Between 1969 and 1975, Bill Brown was technical director of a JPL Raytheon program that beamed 30 kW of power over a distance of 1 mile at 84% efficiency.

To minimize the sizes of the antennas used, the wavelength should be small (and frequency correspondingly high) since antenna efficiency increases as antenna size increases relative to the wavelength used. More precisely, both for the transmitting and receiving antennas, the angular beam width is inversely proportional to the aperture of the antenna, measured in units of the transmission wavelength. The highest frequencies that can be used are limited by atmospheric absorption (chiefly water vapor and CO2) at higher microwave frequencies.

For these reasons, 2.45 GHz has been proposed as being a reasonable compromise. However, that frequency results in large antenna sizes at the GEO distance. A loitering stratospheric airship has been proposed to receive higher frequencies (or even laser beams), converting them to something like 2.45 GHz for retransmission to the ground. This proposal has not been as carefully evaluated for engineering plausibility as have other aspects of SPS design; it will likely present problems for continuous coverage.

Spacecraft Sizing:

The size of an SPS will be dominated by two factors. The size of the collecting apparatus (eg, panels, mirrors, etc) and the size of the transmitting antenna which in part depends on the distance to the receiving antenna. The distance from Earth to geostationary orbit (22,300 miles, 35,700 km), the chosen wavelength of the microwaves, and the laws of physics, specifically the Rayleigh Criterion or Diffraction limit, used in standard RF (Radio Frequency) antenna design will all be factors.

For best efficiency, the satellite antenna should be circular and for the probable microwave wavelength, about 1 kilometers in diameter or larger; the ground antenna (rectenna) should be elliptical, 10km wide, and a length that makes the rectenna appear circular from GSO. (Typically, 14km at some North American latitudes.) Smaller antennas would result in increased losses to diffraction/sidelobes. For the desired (23mW/cm²) microwave intensity these antennas could transfer between 5 and 10 gigawatts of power.

To be most cost effective, the system should operate at maximum capacity. And, to collect and convert that much power, the satellite would require between 50 and 100 square kilometers of collector area (if readily available ~14% efficient monocrystalline silicon solar cells were deployed). State of the art (currently, quite expensive, triple junction gallium arsenide) solar cells with a maximum efficiency of 40.7%  could reduce the necessary collector area by two thirds, but would not necessarily give overall lower costs for various reasons.

For instance, these very recently demonstrated variants may prove to have unacceptably short lifetimes. In either cases, the SPS's structure would be essentially kilometers across, making it larger than most man-made structures here on Earth. While almost certainly not beyond current engineering capabilities, building structures of this size in orbit has not yet been attempted.

LEO/MEO instead of GEO:

A collection of LEO (Low Earth Orbit) space power stations has been proposed as a precursor to GEO (Geostationary Orbit) space power beaming system(s). There would be advantages, such as much shorter energy transmission path lengths allowing smaller antenna sizes, lower cost to orbit, energy delivery to much of the Earth's surface (assuming appropriate antennas are available), etc. And disadvantages, including constantly changing antenna geometries, increased debris collision difficulties, many more power stations to provide continuous power delivery at any particular point on the Earth's surface, etc.

It might be possible to deploy LEO systems sooner than GEO because the antenna development would take less time, but it would certainly take longer to prepare and launch the number of required satellites. Ultimately, because full engineering feasibility studies have not been conducted, it is not known whether this approach would be an improvement over a GEO installation.

Earth Based Infrastructure:

The Earth-based receiver antenna (or rectenna) is a critical part of the original SPS concept. It would probably consist of many short dipole antennas, connected via diodes. Microwaves broadcast from the SPS will be received in the dipoles with about 85% efficiency. With a conventional microwave antenna, the reception efficiency is still better, but the cost and complexity is also considerably greater, almost certainly prohibitively so. Rectennas would be multiple kilometers across. Crops and farm animals may be raised underneath a rectenna, as the thin wires used for support and for the dipoles will only slightly reduce sunlight, so such a rectenna would not be as expensive in terms of land use as might be supposed.

NSS web pages devoted to SSP:

• NSS Space Solar Power Library
• NSS Position Paper on Space Solar Power [PDF]
• NSS Blogs on Space Solar Power
• Brochure on Space-Based Solar Power [PDF]
• Press Conference on First International Assessment of Space Solar Power
• Kalam-NSS Energy Initiative Press Conference
• Kalam-National Space Society Energy Technology Universal Initiative: An International Preliminary Feasibility Study on Space Based Solar Power Stations [PDF]
• Space Solar Power Press Conference (September 12, 2008)
• Press Conference on 2007 National Security Space Office study of space solar power
• News reports on 2007 National Security Space Office study of space solar power

Semoga Bermanfaat

Kunjugi Juga:

Indonesian Space Sciences & Technology School

To Be Continued