AN ENERGY BALANCE MODEL OF GREEN ROOF INTEGRATED PHOTOVOLTAICS : A DETAILED ENERGY BALANCE INCLUDING MICROCLIMATIC EFFECTS
AN ENERGY BALANCE MODEL OF GREEN ROOF INTEGRATED PHOTOVOLTAICS : A DETAILED ENERGY BALANCE INCLUDING MICROCLIMATIC EFFECTS
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绿色屋顶光伏发电的能量平衡模型：包括微气候影响的详细能量平衡
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发表时间：
2011
期刊：
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通讯作者：
Lucas Witmer
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作者：
Lucas Witmer
光伏(PV)电池板在阳光下变热。这通过各种手段降低了运行效率。有几种方法在冷却面板方面已被证明是有效的。绿色屋顶的温度很低，寿命长于白色屋顶。在炎热的夏日，绿色屋顶可以比普通屋顶低30◦C，潜在地将光伏(PV)电池板的效率提高高达16%。其他通常用于冷却PV的方法包括吸湿、喷雾和组合的PV/热系统，以移除或捕获和利用PV中的多余热量。这些系统通常需要复杂的机械系统。通过使用绿色屋顶为PVS创造凉爽的小气候，可以通过被动的方式获得可量化的好处。这个系统被称为绿色屋顶集成光伏系统(GRIPV)：通过屋顶和PV之间的热和漫反射关系来耦合系统。绿色屋顶的降温量在很大程度上取决于气候。根据一个地区的降雨量、相对湿度和典型的环境温度，树叶的蒸散量和在绿色屋顶上存活的植物的种类将有很大的差异。为了量化植物的热效益，基于叶片蒸发蒸腾的质量传递和屋顶的对流效应，建立了计算流体力学模型，并结合瞬变系统模拟来确定基于气候、地理位置、光伏材料类型和几何配置的潜热和显热去除。系统集成光伏(SIPV)设计通过考虑每种配置的热效应，在系统级进行集成。如果不从这个角度进行设计，系统可能会变得悲观，因此能够量化各种系统的主动和被动热效益是至关重要的。与绿色屋顶集成的光伏系统是SIPV设计，因为PV受益于绿色屋顶的热性能，而绿色屋顶同时受益于因阵列的部分遮挡而减少的灼热。该模型为绿色屋顶集成光伏发电系统的综合设计和经济决策提供了依据。图10显示了GRIPV系统的总能量平衡。本质上，这是一个绿色屋顶模型和一个热集成的BIPV模型。绿色屋顶产生的PV和小气候之间的关系增加了屋顶的价值主张，潜在地有利于PV的性能，并且基于夏季光伏性能的提高，在某些地理区域可能是经济可行的。
Photovoltaic (PV) panels get hot in the sun. This decreases the operating efficiency through various means. Several approaches have been proven effective at cooling panels. Green Roofs are thermally cool, outperforming even white roofs over their life. On a hot summer day, a green roof can be 30◦C cooler than a typical roof, potentially improving the efficiency of a photovoltaic (PV) panel by as much as sixteen percent. Other methods that are typically used to cool PVs include wicking, spraying, and combined PV/Thermal systems to remove or capture and utilize excess heat from the PVs. These systems typically require complex mechanical systems. Through the employment of a green roof to create a cool microclimate for the PVs, a quantifiable benefit can be obtained by passive means. This system is termed Green Roof Integrated Photovoltaics (GRIPV): coupled systems via thermal and diffuse-reflective relationship between the roof and the PVs. The amount of cooling from a green roof is highly dependent on climate. Depending on the amount of rainfall, relative humidity, and typical ambient temperature of a region, the evapotranspiration from the leaves and the variety of plants that will survive on a green roof will vary significantly. To quantify the thermal benefit of the plants, based on both the mass transfer from evapotranspiration of water from the leaves as well as the convective effects of the roof, computational fluid dynamics models are developed in conjunction with transient system simulations to determine the latent and sensible heat removal based on climate, geographic location, type of PV material, and geometric configuration. System integrative photovoltaic (SIPV) design contains integration at the systems level by considering thermal effects of each configuration. Because systems can be pessimized if the design is not approached from this perspective, it is crucial to be able to quantify both the active and passive thermal benefits of various systems. A PV system that is integrated with a green roof is a SIPV design because the PVs benefit from the thermal properties of the green roof while the green roof simultaneously benefits by reduced scorching from the partial shading of the array. The model that has been developed in this study enables comprehensive design and economic decision making for green roof integrated photovoltaics. Figure 10 shows the total energy balance of a GRIPV system. In essence, this is a green roof model coupled with a thermally integrated BIPV model. The resulting relationship between the PVs and the microclimate created by the green roof increases the roof’s value proposition and is potentially beneficial to the performance of the PVs and could be economically viable in certain geographic regions based on an increase in PV performance during the summer.