High Temperature, High Efficiency PV-Thermal Solar System

太阳能既可以用来产生热能，也可以用来发电。大多数太阳能电池板只设计用于其中一种目的，因此光伏电池板的效率通常不超过20%，在阳光下暴露时会变热。如果通过让流体穿过面板后部来主动冷却面板，则可以同时产生热量和电能。这种太阳能热电结合系统被称为混合光伏-热能(PV-T)集热器，在空间紧张和对热量和电力都有需求的情况下，它提供了一些优势。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、无阴影的空间。PV-T集热器是一种高效的技术，能够实现超过70%的系统效率(电+热)。为了响应这一中期机遇，本研究计划开发光学纳米结构表面，使可工业化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部散射，吸收更长波长的太阳光，并抑制非常长波长的热发射来实现的。这项研究使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、高效的纳米压印方法(用于制造DVD的技术)进行大面积纳米制造。热辐射的抑制是使用低发射率表面实现的，这也是一种低成本的工艺，类似于应用于节能窗户的Low-E玻璃的热反射涂层。所采用的太阳能电池架构是由三洋首创的异质结界面(HIT)太阳能电池，最近创造了有史以来最高效率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低成本制造，并由于独特的异质结设计而适合于结构涂层。重要的是，这种太阳能电池在高温下保持了其特有的高电效率，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PV-T收集器原型将在该项目中制造，并接受室内和室外测试。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的温度(100摄氏度)的应用，该系统将特别适合。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.