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Boiling water reactors of the Fukushima vintage were constructed with multiple, overlapping alternatives for removing decay heat during shutdown situations.
By Bruce Mrowca
Shutting down a nuclear power plant is not as simple as flipping a switch. Following a plant shutdown, decay heat, a byproduct of nuclear fission, initially produces about 6 percent of the steady state power. That heat decreases over time at a rate dependent on the fuel type, reactor history, and power levels experienced during operation. Decay heat removal has been long recognized as an important plant safety function and is typically mitigated with many layers of defense and redundant systems.

Those systems are usually of no major concern to anyone outside the power plant. But in the weeks since March 11, when a combination of an earthquake and a tsunami shut down the boiling water reactors at Fukushima Daiichi Nuclear Power Plant in Japan, the means by which engineers at a shutdown reactor remove decay heat has taken on worldwide importance.

The Fukushima plant features boiling water reactors, known as BWRs, which operate at lower pressures than the other main light-water reactor technology, the pressurized water reactor. Because of the lower pressure, when the demineralized water flows through the reactor core, the absorbed heat makes the water boil. In normal operation, after water droplets are removed, the resulting steam is fed to a turbine that powers a generator. Continue reading →

By Daniel Mahr, P.E.
Energy Associates, P.C.
Montville, NJ, USA
WHY BIOMASS?

The power industry is confronting challenges with seemingly conflicting goals. Large, solid-fuel power plants provide the reliability and flexibility utilities require for baseload, cycling, and on-demand situations. They provide the economy of scale needed to minimize the cost of production. Consumers, including industry, rely on affordable, dependable electrical energy. It’s an important part of our economy and our daily lifestyle. Reducing emission levels and conserving our finite resources are key components for achieving a sustainable environment.

Historically, biomass powered society’s early development, and its ability to power our needs today is being reassessed, as a means to recycle carbon emissions. Biomass is a resource that can be substituted for coal, in varying degrees for existing pulverized coal (PC) plants. New, large power plants are being designed to utilize biomass as the primary fuel, most notably in circulating fluidized bed combustion (CFB) boilers.
Biomass is available now. New products and sources are being developed, as the market unfolds.

While biomass-fired plants have been a part of the scene for some time, they have typically been relatively small, 25 to 50 MW, and often address specialized, local conditions. Biomass units on the scale of 300 MW and larger present a number of different and important challenges. The plant’s ability to effectively utilize biomass fuel products is more important for this technology scale-up. Continue reading →

empa.ch/vg

EMPA, laboratorium Swiss, telah mengambil langkah besar dalam pengembangan sel pembangkit listrik tenaga surya. Para ilmuwan telah menemukan sel fleksibel berbiaya rendah yang hampir seefisiensi sel dari silikon atau kaca yang lebih mahal.

Hal itu merupakan terobosan kecil, tetapi signifikan dalam memanfaatkan sumber energi terbarukan.

Pada Kamis (19/5), Empa, Laboratorium Sains dan Teknologi Federal Swiss, mengumumkan bahwa mereka telah meningkatkan efisiensi sel surya fleksibel sekaligus membuat rekor dunia baru yakni sebesar 18,7 persen. Ini merupakan perbaikan signifikan atas rekor sebelumnya 17,6 persen yang juga dibuat Empa. Continue reading →

KOMPAS/LASTI KURNIA Kelompok nelayan tradisional yang menangkap ikan dengan tombak di Uma Rai, Pulau Pura, Alor, Nusa Tenggara Timur.

KOMPAS.com – Gelombang laut dan bandul lonceng menjadi inspirasi Zamrisyaf. Periset pada Divisi Penelitian dan Pengembangan PT PLN (Persero) ini merancang pembangkit listrik dengan energi gelombang laut yang menggerakkan bandul kemudian diubah menjadi energi penggerak roda gila dan turbin listrik.

“Teknologi ini sudah mendapatkan hak paten dan siap dikomersialkan,” kata Zamrisyaf, Kamis (19/5/2011) di Jakarta. Zamrisyaf mendaftarkan teknologi pembangkit listrik tenaga gelombang laut-sistem bandulan (PLTGL-SB) untuk mendapatkan paten sejak tahun 2002.

Awalnya Zamrisyaf menekuni bidang pembangkit listrik mikrohidro. Kemudian, suatu perjalanan dengan kapal mendatangkan inspirasi baginya untuk merancang PLTGL-SB. Pada perjalanan itu, kapal diterpa badai dengan gelombang laut tinggi. Kapal berayun-ayun. Lonceng kapal pun berdentang. Zamrisyaf menyimak rumah lonceng beradu dengan bandulannya.

“Gelombang laut memiliki energi yang diteruskan bandulan lonceng. Bandulan lonceng menghasilkan energi bunyi, tetapi bandulan pada PLTGL-SB rancangan saya menghasilkan listrik,” kata Zamrisyaf. Ia mengutip hukum kekekalan energi bahwa energi tidak dapat diciptakan dan dimusnahkan, tetapi diubah.

Zamrisyaf mengubah energi gelombang laut menjadi energi listrik melalui perantara energi gerak bandulan yang menjadi penggerak roda gila. Pada akhirnya, roda gila menggerakkan turbin atau dinamo yang berputar dan menghasilkan listrik.(Nawa Tunggal)

Sumber : http://sains.kompas.com/read/2011/05/20/14243145/Listrik.dari.Gelombang.Laut.Menjanjikan

gobizkorea.com

Cara kerja VGT

Volvo & Porsche

Posisi baling-baling turbon ketika bekerja pada putaran rendah

Volvo & Porsche

Posisi baling-baling turbin ketika berkerja pada putaran tinggi

KOMPAS.com – Variable Geometry Turbocharger, merupakan trend teknologi pada mesin diesel masa kini. Teknologi ini bukan baru, tetapi sudah digunakan pada mesin diesel, terutama yang menggunakan teknologi common rail atau yang menuntut emisi yang rendah pada akhir 1980-an.

Sebutan lain dari VGT adalah VTG (variable turbo geometry), VVT (variable vanes turbocharger) dan VNT (variable nozzle turbocharger). Ya, tergantung pada produsen turbo dan pembuat mesin. Continue reading →