High Temperature, High Efficiency PV-Thermal Solar System

太阳能可以用来产生热量和电力。大多数太阳能电池板仅用于其中一个目的，因此光伏电池板的效率通常不超过20%，并且在暴露于阳光下时会变热。如果通过使流体穿过面板的后部来主动冷却面板，则可以产生热量和电力。这种太阳能热电联产系统被称为混合光热（PV-T）集热器，当空间非常宝贵并且对热和电力都有需求时，它具有一些优势。到2050年，太阳能发电预计将提供世界上大部分的电力，并将需要更有效地利用建筑环境中存在的优质无阴影空间。PV-T集热器是一种高效技术，能够实现超过70%的系统效率（电+热）。为了应对这一中期机会，本研究计划开发光学纳米结构表面，使工业可制造的太阳能电池成为理想的PV-T吸收器。这是通过确保可见光和近红外太阳光在太阳能电池内内部散射，吸收较长波长的太阳光并抑制极长波长的热发射来实现的。该研究采用最先进的计算机模拟来设计纳米结构表面，然后使用低成本有效的纳米压印方法（用于制造DVD的技术）进行大面积纳米加工。通过低辐射率的表面来实现热辐射的抑制，这也是一种低成本的工艺，类似于应用于节能窗户中的低辐射玻璃的“热反射”涂层。所采用的太阳能电池结构是三洋率先开发的异质结界面（HIT）太阳能电池，最近创造了有史以来效率最高的硅太阳能电池的世界纪录。值得注意的是，这种太阳能电池可以以低成本制造，并且由于独特的异质结设计而适合于结构化涂层。重要的是，这种太阳能电池在高温下保持其特有的高电效率，使其成为PV-T应用的理想选择。包含这种优化太阳能电池的原型PV-T集热器将在该项目中制造，并进行室内和室外测试。将建立一个预测性计算机模型，再现集热器在室内和室外条件下的电和热输出。该模型将被用作评估该技术在各种应用中的适用性的基础，特别是那些需要相对较高温度的热（100摄氏度）的应用，该系统将特别适合。该研究将在科学文献和会议中传播，并在帝国理工学院举办的研讨会和贸易展览会上向更广泛的受众传播。

Solar energy can be used to generate both heat and electrical power. Most solar panels are designed for only one of these purposes, so an electrical photovoltaic panel is typically no more than 20% efficient and will become hot when exposed to sunlight. If the panel is actively cooled by passing a fluid through the rear of the panel, it is possible to generate both heat and electrical power. This combined solar heat and power system is known as a hybrid Photovoltaic-Thermal (PV-T) collector and offers some advantages when space is at a premium and there is demand for both heat and power. By 2050 solar power is projected to deliver the majority of the world's electricity and will require much more efficient use of the premium, unshaded space that exists in the built environment. PV-T collectors are a highly efficient technology, capable of achieving system efficiencies (electrical + thermal) of over 70%.In response to this medium term opportunity, this research proposal develops optical nanostructured surfaces that enable an industrially manufacturable solar cell to become the ideal PV-T absorber. This is achieved by ensuring visible and near-infrared sunlight light is scattered internally within the solar cell, longer wavelength sunlight is absorbed and very long wavelength thermal emission is suppressed. The research employs state of the art computer simulation to design the nanostructured surface, followed by large area nanofabrication that can be performed using low-cost effective nanoimprint methods (the technique used to manufacture DVDs). The the suppression of thermal radiation is achieved using a low-emissivity surface which is also a low-cost process, similar to the 'heat reflecting' coatings that are applied to low-E glass used in energy efficient windows.The solar cell architecture employed is the Heterojunction Interface (HIT) solar cell pioneered by Sanyo and that recently set the world record for the highest efficiency silicon solar cell ever demonstrated. Remarkably, this solar cell can be manufactured at low cost and lends itself to structured coating owing to the unique heterojunction design. Importantly, this solar cell retains it's characteristically high electrical efficiency at high temperature making it ideal for PV-T applications. Prototype PV-T collectors that contain this optimised solar cell will be fabricated in this project and subjected to both indoor and outdoor testing. A predictive computer model will be established that reproduces the electrical and thermal output of the collector under both indoor and outdoor conditions. The model will be used as a basis to assess the applicability of the technology in various applications, especially those that demand relatively high temperature heat (100 degC) for which the system will be particularly well suited.The research will be disseminated in the scientific literature and conferences and also to a broader audience at workshops held at Imperial College and trade shows.