‘Squeezing’ near-field thermal emission for ultra-efficient high-power thermophotovoltaic conversion

We numerically demonstrate near-field planar ThermoPhotoVoltaic systems with very high efficiency and output power, at large vacuum gaps. Example performances include: at 1200 °K emitter temperature, output power density 2 W/cm[superscript 2] with ~47% efficiency at 300 nm vacuum gap; at 2100 °K, 24 W/cm[superscript 2] with ~57% efficiency at 200 nm gap; and, at 3000 °K, 115 W/cm[superscript 2] with ~61% efficiency at 140 nm gap. Key to this striking performance is a novel photonic design forcing the emitter and cell single modes to cros resonantly couple and impedance-match just above the semiconductor bandgap, creating there a ‘squeezed’ narrowband near-field emission spectrum. Specifically, we employ surface-plasmon-polariton thermal emitters and silver-backed semiconductor-thin-film photovoltaic cells. The emitter planar plasmonic nature allows for high-power and stable high-temperature operation. Our simulations include modeling of free-carrier absorption in both cell electrodes and temperature dependence of the emitter properties. At high temperatures, the efficiency enhancement via resonant mode cross-coupling and matching can be extended to even higher power, by appropriately patterning the silver back electrode to enforce also an absorber effective surface-plasmon-polariton mode. Our proposed designs can therefore lead the way for mass-producible and low-cost ThermoPhotoVoltaic micro-generators and solar cells.Massachusetts Institute of Technology. Institute for Soldier Nanotechnologies (Contract W911NF-13-D-0001

Benthic Estuarine Assemblages of the Southeastern Brazil Marine Ecoregion (SBME)

We assess the current knowledge of the benthic assemblages in the Southeastern Brazil Marine Ecoregion (SBME), which extends for approximately 1200 km of coastline and includes seven major estuarine systems from Guanabara Bay in Rio de Janeiro to Babitonga Bay (or Sao Francisco do Sul) in Santa Catarina. The high ecosystem diversity of SBME putatively accounts for the high levels of endemism of the regional marine invertebrate fauna. However, until more taxonomical and biogeographical evidence is available, the SBME should be treated as a working biogeographical hypothesis rather than a cohesive unit identified by endemic fauna. As a consequence of urban, agricultural, and industrial development, the coastal areas from the SBME have been the most altered in the country over the last 500 years. Some of the largest cities and busiest harbors of the country are in or near the regional estuarine areas. The rapid environmental changes over the last several decades do not allow for the assessment if current similarities and dissimilarities in the benthic assemblages express pristine conditions or if they are already the result of major human interventions, especially in the case of the Guanabara, Sepetiba, and Santos estuaries.Univ Fed Parana, Ctr Estudos Mar, Pontal Do Sul, Parana, BrazilUniv Fed Sao Paulo, Inst Mar, Santos, SP, BrazilUniv Catolica Norte, Millennium Nucleus Ecol & Sustainable Management, Fac Ciencias Mar, Dept Biol Marina, Coquimbo, ChileUniv Estadual Paulista, Inst Biociencias, Campus Litoral Paulista, Sao Vicente, SP, BrazilUniv Fed Fluminense, Dept Biol Marinha, Campus Valonguinho, Niteroi, RJ, BrazilUniv Estadual Paulista, Inst Biociencias, Campus Litoral Paulista, Sao Vicente, SP, Brazi