Solar home systems for improving electricity access : An off-grid solar perspective towards achieving universal electrification
Solar home systems for improving electricity access : An off-grid solar perspective towards achieving universal electrification
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用于改善电力供应的太阳能家用系统：实现普遍电气化的离网太阳能视角
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发表时间：
2019
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通讯作者：
N. Narayan
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作者：
N. Narayan
全球近10亿人无法获得电力。由于各种原因，电网扩展对于未通电社区来说不是立即可行的解决方案。由于这些电力匮乏的地区大多位于热带地区，因此使用离网太阳能解决方案，如太阳能家庭系统（SHS）是一种合乎逻辑的方法。然而，最先进的SHS在其功率水平和可用性方面受到限制。此外，次优的系统尺寸导致SHS电池的过度利用--因此，更快的退化--，或者SHS电池的利用不足，导致更高的系统成本。另外，离网SHS设计遭受缺乏作为离网光伏（PV）系统的第一步所需的可靠负载分布数据（例如，SHS）设计。本论文所做的工作旨在分析使用SHS在功率水平、可用性、电池尺寸和寿命方面的技术限制和机会，以实现普遍电气化。首先，三个主要的电气化途径，即，电网扩展，集中式微电网，和独立的太阳能为基础的解决方案，如微微太阳能和SHS的相对优点和缺点进行了分析。然后，提出了一种方法来量化的电力需求的家庭的电力接入的多层框架（MTF）所概述的各个层次的电力接入的负载配置文件的形式，用于测量家庭电力接入。其次，对于SHS应用，提出了一种非经验电池寿命估计方法，该方法可在SHS的设计阶段用于以电池寿命的形式比较手头的候选电池选择的性能。第三，考虑到电池寿命、温度对SHS性能的影响、负载丢失概率（LLP）方面的电源可用性以及多余的光伏能量，对每个电气化层的最佳独立系统尺寸进行了评估。基于遗传算法的多目标优化进行，提供洞察力的各种系统指标，如LLP，多余的能量，和电池寿命的SHS大小的微妙的相互依赖性。这项工作的结论是，满足第4级和第5级电气化的电力需求是无法通过单独的社会科学及人文科学。因此，一个自下而上的直流微电网诞生的SHS的互联进行了探索。一个模块化的和可扩展的架构，这样一个自下而上的，互连的SHS为基础的架构介绍，和独立的SHS的微电网的好处量化在较低的电池尺寸和定义的系统指标。在对SHS之间的能量共享进行建模时，结果表明，与独立SHS相比，通过第5层级别的互连可以实现超过40%的电池尺寸增益，以满足相同的功率可用性阈值。最后，一个地理信息系统（GIS）为基础的方法，考虑到家庭的空间分布，同时利用图论为基础的方法来达到最佳的微电网拓扑结构的网络长度。本论文中进行的研究强调了SHS在实现普遍电气化方面的技术局限性，同时强调了通过SHS建立（农村）DC微电网的自下而上方法的好处，这可以使爬上所谓的电气化阶梯。
Almost a billion people globally lack access to electricity. For various reasons, grid extension is not an immediately viable solution for the un(der-) electrified communities. As most of these electricity-starved regions lie in tropical latitudes, the use of off-grid solar-based solutions like solar home systems (SHS) is a logical approach. However, state-of-the-art SHS is limited in its power levels and availability. Moreover, sub-optimal system sizing leads to either over-utilization --- and therefore, faster degradation --- of the SHS battery, or under-utilization of the SHS battery, leading to higher system costs. Additionally, off-grid SHS designs suffer from a lack of reliable load profile data needed as the first step for an off-grid photovoltaic (PV) system (e.g., SHS) design. The work undertaken in this dissertation aims to analyze the technological limits and opportunities of using SHS in terms of power level, availability, and battery size, lifetime for achieving universal electrification. Firstly, the three main electrification pathways, viz., grid extension, centralized microgrids, and standalone solar-based solutions like pico-solar and SHS are analyzed for their relative merits and demerits. Then, a methodology is presented to quantify the electricity demand of the households in the form of load profiles for the various tiers of electricity access as outlined by the multi-tier framework (MTF) for measuring the household electricity access. Secondly, for the SHS application, a non-empirical battery lifetime estimation methodology is presented that can be used at the design phase of SHS for comparing the performance of candidate battery choices at hand in the form of battery lifetime. Thirdly, an optimal standalone system size is evaluated for each tier of electrification, taking into account the battery lifetime, temperature impact on SHS performance, power supply availability in terms of the loss of load probability (LLP), and excess PV energy. A genetic algorithm-based multi-objective optimization is performed, giving insights on the delicate interdependencies of the various system metrics like LLP, excess energy, and battery lifetime on the SHS sizing. This exercise concludes that meeting the electricity requirements of tiers 4 and 5 level of electrification is untenable through SHS alone. Consequently, a bottom-up DC microgrid born out of the interconnection of SHS is explored. A modular and scalable architecture for such a bottom-up, interconnected SHS-based architecture is introduced, and the benefits of the microgrid over standalone SHS are quantified in terms of lower battery sizes and the defined system metrics. On modeling the energy sharing between the SHS, it is shown that battery sizing gains of more than 40% could be achieved with inter-connectivity at tier 5 level as compared to standalone SHS to meet the same power availability threshold. Finally, a Geo-Information System (GIS)-based methodology is presented that takes into account the spatial spread of the households while utilizing graph theory-based approaches to arrive at the optimal microgrid topology in terms of network length. The research carried out in this dissertation underlines the technological limitations of SHS in aiming towards universal electrification, while highlighting the benefits of moving towards a bottom-up approach in building (rural) DC microgrids through SHS, which can enable the climb up the so-called electrification ladder.