Portable Solar Irrigation System: IGCSE Engineering Case Study | 便携式太阳能灌溉系统：IGCSE 工程案例分析实战演练

📚 Portable Solar Irrigation System: IGCSE Engineering Case Study | 便携式太阳能灌溉系统：IGCSE 工程案例分析实战演练

Case studies are central to IGCSE Cambridge Engineering because they require learners to apply design, materials, electronics and mechanics to a real problem. This worked example follows a solar-powered irrigation system for a school greenhouse.

案例分析是剑桥IGCSE工程的核心，因为它要求学习者将设计、材料、电子和机械知识应用于真实问题。本实例围绕学校温室的太阳能灌溉系统展开。

We will move from design context to specification, calculations, manufacturing and testing. Each section shows how theory is turned into an engineering decision.

我们将从设计背景逐步推进到设计规格、计算、制造和测试。每一节都展示理论如何转化为工程决策。

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1. Understanding the Design Context | 理解设计背景

The school greenhouse needs a reliable watering system for holiday periods when staff are not available. Plants require about 2 litres of water per day, and the greenhouse receives strong sunlight for most of the summer day.

学校温室在假期无人值守时需要可靠的浇水系统。植物每天大约需要2升水，而且温室在夏季白天大部分时间有充足日照。

The key users are teachers, students and maintenance staff. The design must be safe, easy to operate and powered by renewable energy because the greenhouse has no convenient mains socket near the beds.

关键用户是教师、学生和维护人员。设计必须安全、易于操作，并使用可再生能源供电，因为温室种植床附近没有方便的市电插座。

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2. Research and Product Analysis | 调研与产品分析

Existing products include timer-based sprinklers, drip irrigation kits and soil moisture sensors sold with garden controllers. Most timer systems water at fixed times, so they waste water if the soil is already wet.

现有产品包括基于定时器的喷灌器、滴灌套件以及与园艺控制器配套销售的土壤湿度传感器。大多数定时系统在固定时间浇水，因此如果土壤已经湿润就会浪费水。

Product analysis shows that a closed-loop system using a soil moisture probe can switch the pump only when the soil is dry. Solar panels and rechargeable batteries remove the need for mains wiring and reduce running costs.

产品分析表明，使用土壤湿度探头的闭环系统可以让水泵仅在土壤干燥时启动。太阳能电池板和可充电电池免去了市电布线并降低运行成本。

A key limitation of resistive soil sensors is corrosion. A capacitive sensor is more durable and provides a more stable reading for a school project that must last several growing seasons.

电阻式土壤传感器的主要局限是腐蚀。电容式传感器更耐用，能为必须使用多个种植季的学校项目提供更稳定的读数。

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3. Writing a Design Specification | 撰写设计规格

A strong specification must be measurable so the final prototype can be tested objectively. The main criteria are shown below.

良好的设计规格必须可测量，以便最终原型能够被客观测试。主要标准如下所示。

The system must deliver 2 L of water per day, operate automatically when the soil moisture falls below 40%, and run for at least 3 cloudy days from the battery. The total material cost should be below 30 USD, and the pump must lift water by at least 0.8 m.

该系统每天应输送2升水，在土壤湿度低于40%时自动运行，并且电池至少能支持3个阴天。总材料成本应低于30美元，水泵扬程至少达到0.8米。

The specification also requires safe low-voltage DC operation, a waterproof enclosure for the controller, and easy maintenance by students with basic tools.

规格还要求低电压直流安全运行、控制器防水外壳，以及学生使用基本工具即可进行维护。

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4. Generating and Selecting Ideas | 方案生成与筛选

Three concepts were considered. Concept A uses a simple timer. Concept B uses a soil moisture threshold to control the pump. Concept C adds wireless monitoring to a smartphone.

考虑了三种方案。方案A使用简单定时器。方案B使用土壤湿度阈值控制水泵。方案C在智能手机上增加无线监控。

A decision matrix scored the ideas against cost, reliability, ease of manufacture and water efficiency. Concept B scored highest because it saves water, has fewer failure points than C and is much more responsive than A.

决策矩阵从成本、可靠性、制造便利性和节水效率等方面对方案进行评分。方案B得分最高，因为它节水、比方案C故障点更少，并且比方案A响应更灵敏。

The chosen concept combines a capacitive soil moisture sensor, a 12 V DC pump, a 5 W solar panel and a small rechargeable battery controlled by a comparator circuit. A manual override button is included for classroom demonstrations.

选定方案结合了电容式土壤湿度传感器、12V直流泵、5W太阳能电池板和由比较器电路控制的小型可充电电池。还配有一个手动按钮，用于课堂演示。

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5. Materials and Component Selection | 材料与元件选择

Material selection balances strength, corrosion resistance and cost. The frame is 3D printed from ABS because it is tough, UV-resistant and easy to replace if a part breaks.

材料选择需要平衡强度、耐腐蚀性和成本。支架采用ABS材料3D打印，因为它坚韧、抗紫外线，并且零件损坏时易于更换。

Water pipes are made from food-grade PVC tubing. Stainless steel screws are used in wet areas to prevent rust, while the enclosure is laser-cut acrylic with a rubber gasket for waterproofing.

水管采用食品级

Published by TutorHao | IGCSE 工程 Revision Series | aleveler.com

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