{"id":1265,"date":"2013-07-25T18:27:15","date_gmt":"2013-07-25T18:27:15","guid":{"rendered":"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/?p=1265"},"modified":"2013-07-25T18:27:33","modified_gmt":"2013-07-25T18:27:33","slug":"optimizing-emitter-to-absorber-area-ratio-for-improved-efficiency-in-planar-solar-thermophotovoltaics","status":"publish","type":"post","link":"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/optimizing-emitter-to-absorber-area-ratio-for-improved-efficiency-in-planar-solar-thermophotovoltaics\/","title":{"rendered":"Optimizing Emitter-to-Absorber Area Ratio for Improved Efficiency in Planar Solar Thermophotovoltaics"},"content":{"rendered":"<p align=\"left\">Solar thermophotovoltaic (STPV) devices have the potential to overcome the Shockley-Queisser limit by converting solar radiation to a narrow-band thermal emission matched to the spectral response of a photovoltaic (PV) cell<sup>[<a href=\"#footnote_0_1265\" id=\"identifier_0_1265\" class=\"footnote-link footnote-identifier-link\" title=\"H. Nils-Peter and W. Peter, &ldquo;Theoretical limits of thermophotovoltaic solar energy conversion,&rdquo; Semicond. Sci. Technol. , vol. 18, no. 5, pp. 151-157, 2003.\">1<\/a>]<\/sup>,<sup>[<a href=\"#footnote_1_1265\" id=\"identifier_1_1265\" class=\"footnote-link footnote-identifier-link\" title=\"W. Shockley and H.J. Queisser, &ldquo;Detailed Balance Limit of Efficiency of p-n Junction Solar Cells,&rdquo; J. Appl. Phys., vol. 32, no. 3, pp. 510-519, 1961.\">2<\/a>]<\/sup>. However, limiting the influence of non-idealities of the individual STPV components (absorber\/emitter\/PV) through an understanding of the highly coupled energy conversion process is needed to approach high efficiencies. Although reported TPV efficiencies (thermal-to-electric) have exceeded 10%<sup>[<a href=\"#footnote_2_1265\" id=\"identifier_2_1265\" class=\"footnote-link footnote-identifier-link\" title=\"C.J. Crowley, N. A. Elkouh, S. Murray, and D. L. Chubb, &ldquo;Thermophotovoltaic Converter Performance for Radioisotope Power Systems,&rdquo; in AIP Conf. Proc., 2005, vol. 746, pp. 601-614.\">3<\/a>]<\/sup>, measured overall STPV conversion efficiencies are below 1%<sup>[<a href=\"#footnote_3_1265\" id=\"identifier_3_1265\" class=\"footnote-link footnote-identifier-link\" title=\"A.S. Vlasov et al., &ldquo;TPV Systems with Solar Powered Tungsten Emitters,&rdquo; in AIP Conf. Proc., 2007, vol. 890, pp. 327-334.\">4<\/a>]<\/sup>,<sup>[<a href=\"#footnote_4_1265\" id=\"identifier_4_1265\" class=\"footnote-link footnote-identifier-link\" title=\"A. Datas and C. Algora, &ldquo;Development and experimental evaluation of a complete solar thermophotovoltaic system,&rdquo; Prog. Photovolt: Res. Appl., Available: doi:&nbsp;10.1002\/pip.2201\">5<\/a>]<\/sup>. One of the most prohibitive aspects of this system can be the thermal transfer efficiency due to the high temperature operation of the device.<\/p>\n<p align=\"left\">In this work, we designed an experimental system for characterizing high-temperature planar STPVs, schematically shown in Figure 1, aimed to bridge the gap between potential and measured STPV performance. We show how increasing the emitter-to-absorber area ratio (AR) can compensate for non-ideal spectral selectivity on the absorber side. This concept was implemented in planar devices through a process of seeded growth of vertically aligned multi-walled carbon nanotube forests on smooth tungsten surfaces (shown in Figure 2). The TPV-side of the system is composed of a one-dimensional Si\/SiO<sub>2<\/sub> photonic crystal emitter (1D PhC) paired with a low band-gap PV cell (InGaAsSb). With a 4:1 emitter-to-absorber area ratio (AR 4), we experimentally demonstrate a two-fold increase in thermal transfer efficiency (relative to AR 1) and a significant boost in STPV performance leading to efficiencies exceeding 2%.<\/p>\n\n\t\t<style type=\"text\/css\">\n\t\t\t#gallery-1 {\n\t\t\t\tmargin: auto;\n\t\t\t}\n\t\t\t#gallery-1 .gallery-item {\n\t\t\t\tfloat: left;\n\t\t\t\tmargin-top: 10px;\n\t\t\t\ttext-align: center;\n\t\t\t\twidth: 50%;\n\t\t\t}\n\t\t\t#gallery-1 img {\n\t\t\t\tborder: 2px solid #cfcfcf;\n\t\t\t}\n\t\t\t#gallery-1 .gallery-caption {\n\t\t\t\tmargin-left: 0;\n\t\t\t}\n\t\t\t\/* see gallery_shortcode() in wp-includes\/media.php *\/\n\t\t<\/style>\n\t\t<div id='gallery-1' class='gallery galleryid-1265 gallery-columns-2 gallery-size-medium'><dl class='gallery-item'>\n\t\t\t<dt class='gallery-icon landscape'>\n\t\t\t\t<a href='https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/optimizing-emitter-to-absorber-area-ratio-for-improved-efficiency-in-planar-solar-thermophotovoltaics\/lenert_tpv_01\/'><img width=\"300\" height=\"241\" src=\"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-content\/blogs.dir\/22\/files\/2013\/07\/lenert_tpv_01-300x241.png\" class=\"attachment-medium size-medium\" alt=\"\" loading=\"lazy\" aria-describedby=\"gallery-1-1267\" srcset=\"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-content\/blogs.dir\/22\/files\/2013\/07\/lenert_tpv_01-300x241.png 300w, https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-content\/blogs.dir\/22\/files\/2013\/07\/lenert_tpv_01-220x177.png 220w, https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-content\/blogs.dir\/22\/files\/2013\/07\/lenert_tpv_01.png 608w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a>\n\t\t\t<\/dt>\n\t\t\t\t<dd class='wp-caption-text gallery-caption' id='gallery-1-1267'>\n\t\t\t\tFigure 1: Schematic of the planar STPV experimental layout. Incoming solar radiation is converted to heat at the absorber (MWCNT\/W); heat is selectively radiated by the emitter (1D PhC) and converted to electrical power at the PV (InGaAsSb \u2013 0.55 eV).\n\t\t\t\t<\/dd><\/dl><dl class='gallery-item'>\n\t\t\t<dt class='gallery-icon landscape'>\n\t\t\t\t<a href='https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/optimizing-emitter-to-absorber-area-ratio-for-improved-efficiency-in-planar-solar-thermophotovoltaics\/lenert_tpv_02\/'><img width=\"300\" height=\"242\" src=\"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-content\/blogs.dir\/22\/files\/2013\/07\/lenert_tpv_02-300x242.png\" class=\"attachment-medium size-medium\" alt=\"\" loading=\"lazy\" aria-describedby=\"gallery-1-1268\" srcset=\"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-content\/blogs.dir\/22\/files\/2013\/07\/lenert_tpv_02-300x242.png 300w, https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-content\/blogs.dir\/22\/files\/2013\/07\/lenert_tpv_02-220x178.png 220w, https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-content\/blogs.dir\/22\/files\/2013\/07\/lenert_tpv_02.png 905w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a>\n\t\t\t<\/dt>\n\t\t\t\t<dd class='wp-caption-text gallery-caption' id='gallery-1-1268'>\n\t\t\t\tFigure 2: a) Absorber-side top view of a 4:1 emitter-to-absorber module showing spatially-defined MWCNT growth on a W-coated Si substrate. b) SEM side view of the MWCNT\/W boundary, showing the vertically aligned nanotubes.\n\t\t\t\t<\/dd><\/dl><br style=\"clear: both\" \/>\n\t\t<\/div>\n\n<ol class=\"footnotes\"><li id=\"footnote_0_1265\" class=\"footnote\">H. Nils-Peter and W. Peter, &#8220;Theoretical limits of thermophotovoltaic solar energy conversion,&#8221; <i>Semicond. Sci. Technol. ,<\/i> vol. 18, no. 5, pp. 151-157, 2003. [<a href=\"#identifier_0_1265\" class=\"footnote-link footnote-back-link\">&#8617;<\/a>]<\/li><li id=\"footnote_1_1265\" class=\"footnote\">W. Shockley and H.J. Queisser, &#8220;Detailed Balance Limit of Efficiency of p-n Junction Solar Cells,&#8221; <i>J. Appl. Phys.<\/i>, vol. 32, no. 3, pp. 510-519, 1961. [<a href=\"#identifier_1_1265\" class=\"footnote-link footnote-back-link\">&#8617;<\/a>]<\/li><li id=\"footnote_2_1265\" class=\"footnote\">C.J. Crowley, N. A. Elkouh, S. Murray, and D. L. Chubb, &#8220;Thermophotovoltaic Converter Performance for Radioisotope Power Systems,&#8221; in <i>AIP Conf. Proc.<\/i>, 2005, vol. 746, pp. 601-614. [<a href=\"#identifier_2_1265\" class=\"footnote-link footnote-back-link\">&#8617;<\/a>]<\/li><li id=\"footnote_3_1265\" class=\"footnote\">A.S. Vlasov <i>et al.<\/i>, &#8220;TPV Systems with Solar Powered Tungsten Emitters,&#8221; in <i>AIP Conf. Proc.<\/i>, 2007, vol. 890, pp. 327-334. [<a href=\"#identifier_3_1265\" class=\"footnote-link footnote-back-link\">&#8617;<\/a>]<\/li><li id=\"footnote_4_1265\" class=\"footnote\">A. Datas and C. Algora, &#8220;Development and experimental evaluation of a complete solar thermophotovoltaic system,&#8221; <i>Prog. Photovolt: Res. Appl.<\/i>, Available: doi:\u00a010.1002\/pip.2201 [<a href=\"#identifier_4_1265\" class=\"footnote-link footnote-back-link\">&#8617;<\/a>]<\/li><\/ol>","protected":false},"excerpt":{"rendered":"<p>Solar thermophotovoltaic (STPV) devices have the potential to overcome the Shockley-Queisser limit by converting solar radiation to a narrow-band thermal&#8230;<\/p>\n","protected":false},"author":370,"featured_media":1267,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[6,8,5532],"tags":[12682,4110],"_links":{"self":[{"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-json\/wp\/v2\/posts\/1265"}],"collection":[{"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-json\/wp\/v2\/users\/370"}],"replies":[{"embeddable":true,"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-json\/wp\/v2\/comments?post=1265"}],"version-history":[{"count":4,"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-json\/wp\/v2\/posts\/1265\/revisions"}],"predecessor-version":[{"id":2140,"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-json\/wp\/v2\/posts\/1265\/revisions\/2140"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-json\/wp\/v2\/media\/1267"}],"wp:attachment":[{"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-json\/wp\/v2\/media?parent=1265"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-json\/wp\/v2\/categories?post=1265"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/wp-json\/wp\/v2\/tags?post=1265"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}