Pressure retarded osmosis: Operating in a compromise between power density and energy efficiency

There is an enormous potential for energy generation from the mixing of sea and river water at global estuaries. Here, we model a novel approach to convert this source of energy directly into hydrogen and electricity using reverse electrodialysis (RED). RED relies on converting ionic current to electric current using multiple membranes and redox-based electrodes. A thermodynamic model for RED is created to evaluate the electricity and hydrogen which can be extracted from natural mixing processes. With equal volume of high and low concentration solutions (1 L), the maximum energy extracted per volume of solution mixed occurred when the number of membranes is reduced, with the lowest number tested here being five membrane pairs. At this operating point, 0.32 kWh/m3 is extracted as electrical energy and 0.95 kWh/m3 as hydrogen energy. This corresponded to an electrical energy conversion efficiency of 15%, a hydrogen energy efficiency of 35%, and therefore, a total mixing energy efficiency of nearly 50%. As the number of membrane pairs increases from 5 to 20, the hydrogen power density decreases from 13.6 W/m2 to 2.4 W/m2 at optimum external load. In contrast, the electrical power density increases from 0.84 W/m2 to 2.2 W/m2. Optimum operation of RED depends significantly on the external load (external device). A small load will increase hydrogen energy while decreasing electrical energy. This trade-off is critical in order to optimally operate an RED cell for both hydrogen and electricity generation.

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Penentuan Rasio Bahan Sampah Organik Optimum Terhadap Kinerja Compost Solid Phase Microbial Fuel Cells (CSMFCs)

Jurnal Presipitasi Media Komunikasi dan Pengembangan Teknik Lingkungan ◽

10.14710/presipitasi.v16i1.24-28 ◽

2019 ◽

Vol 16 (1) ◽

pp. 24 ◽

Cited By ~ 1

Author(s):

Meishinta Ariyanti ◽

Ganjar Samudro ◽

Dwi Siwi Handayani

Keyword(s):

Energy Efficiency ◽

Fuel Cells ◽

Power Density ◽

Microbial Fuel Cells ◽

Solid Phase ◽

Coulombic Efficiency ◽

Single Chamber

Compost Solid Phase Microbial Fuel Cells (CSMFCs) merupakan teknologi pengomposan yang diintegrasikan dengan sistem MFCs untuk menghasilkan kompos dan produksi biolistrik dari sampah padat organik. Penelitian ini bertujuan untuk meningkatkan kinerja CSMFCs melalui penerapan perlakuan optimal dari penelitian terdahulu seperti, kadar air 60%, volume sampah 2/3 reaktor, dan penambahan bioaktivator. CSMFCs dalam penelitian ini dilakukan dalam kondisi batch menggunakan reaktor tipe single chamber dan dual anode graphene. Sampah daun dan sampah sisa makanan digunakan sebagai substrat dalam studi ini. Bahan sampah tersebut divariasikan berdasarkan rasio bahan (sampah daun:sampah sisa makanan) yaitu 100:0, 0:100, dan 50:50. Hasil penelitian ini menunjukan kinerja CSMFCs yang optimum terdapat pada variasi sampah campuran keduanya dengan rasio bahan 50:50. Variasi ini dapat menghasilkan kompos yang baik, yaitu memenuhi SNI 19-7030-2004, serta produksi listrik yang cukup tinggi yaitu power density 41,6 mW/m2, coulombic efficiency 0,647% dan energy efficiency 0,0127%.

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