電動車太陽能冷氣機研製

Abstract

本碩士論文之研究目的為開發一套適合電動車使用之太陽能空調系統，以降低空調系統對於電動車之耗能負擔。本研究使用兩片發電量二百三十瓦的太陽能板與一具額定功率一百五十瓦之壓縮機開發一套十二伏特太陽能驅動之冷氣系統，此系統包含冷氣空調、電池管理與能源管理三個子系統，每一個子系統都包含了一個自製的嵌入式控制器。所有系統軟/硬體及韌體的設計、製作、測試與分析都會在本論文中詳細描述與討論。 本研究所開發之電動車用太陽能冷氣系統經過實驗運轉測試與分析後，可歸納出此系統具備以下幾項特色: 1. 本系統使用台大新能源中心開發之nMPPO(near Maximum Power Point Opeartion)太陽光發電控制技術，減少太陽光發電系統之硬體成本及損耗所可能造成的不確定性； 2. 透過電力電子控制技術，並利用鋰電池輔助太陽電池以提供冷氣系統壓縮機啟動所需之大電流(可高達100安培)，當太陽光發電量充足時，可直接以太陽光發電驅動冷氣機運轉，並將多餘的電能儲存在鋰電池，當太陽光發電量不足時，可以鋰電池輔助供電給冷氣機，以確保冷氣系統可在太陽光發電量擾動情形下亦能平順地運轉； 3. 為了延長冷氣機在太陽光發電量不足或不穩定下之運轉時間與提升系統可靠度，本系統可利用現有車用鉛酸電池(低壓)作為額外的供電來源，該鉛酸電池可由電動車之動力電池(高壓)保持其電壓維持在一穩定範圍內，除可在鋰電池(低壓)電量不足時輔助供電給冷氣機使用，亦可與鋰電池(低壓)共同作為太陽電池與冷氣機間之緩衝，發揮穩定電壓與保護冷氣機之功能，以提昇本系統抵抗太陽光輻射量擾動之強健性；此外，鉛酸電池提供給冷氣使用之電能亦可在太陽輻射量充足時由太陽光發電補充，藉此可提高本系統之太陽能能源替代率； 4. 本系統透過自行研發之電池管理與能量管理整合控制技術，可在冷氣機運轉下同時對鋰電池芯/模組進行電量平衡工作。在電池芯/模組高電量狀態下，能量控制器將輸出電壓保持在直流/交流逆變器的輸入電壓範圍內和電池的充放電控制，除可供應冷氣機電源，電池管理系統可同時對鋰電池芯/模組進行平衡。 5. 本系統之冷氣機控制透過擾動式搜尋法，搜尋最佳之冷氣機效能係數(Coefficient of Performance, COP)，並透過蒸發器之風速控制，將冷氣機之COP值盡可能控制在此最佳值，根據2012年12月~2013年1月所收集之實驗數據顯示，在外界環境溫度約攝氏25度、蒸發器出風口溫度約攝氏17度下，COP平均值可達2.0左右，若是在較高環境溫度下，COP值可再更高。

The goal of this research is to develop a solar powered air-conditioner for electric vehicles (EVs) to reduce the energy consumption load of air-conditioning to batteries. In this thesis, two 230W photovoltaic modules and a 150W compressor were adopted to develop a 12V solar powered air-conditioner. The system consistss of three sub-systems an air-conditioner, a battery management system and an energy management system, which all employed a self-made embedded controller. The details about the design, development, tests and evaluation of the system’s hardware,firmware and software will be presented and discussed. Experimental tests and data analysis reveal that the developed solar powered air-conditioning system has the following features: 1. The system utilizes the novel solar PV control technique dubbed nMPPO (near Maximum Power Point Operation), which was developed by the NTU New Energy Center., to reduce the hardware cost and uncertainty due to wear of hardware components. 2. Through power electronics control techniques and the use of lithium-ion batteries for aiding solar batteries in providing high currents (up to 100A) to start the compressor of the air-conditioner, the air-conditioner is able to be directly driven by solar PV panels as the power generation of solar PV panels is high. Also, the excess electrical energy generated by solar PV panels can be saved in the lithium-ion batteres. As the solar PV power generation is low, lithium-ion batteries can provide ancillary electric power for the air-conditioner to make the system be able to smoothly operate in the face of solar power generation fluctuation. 3. In order to extend the run time of the air-conditioner in poor or unstable solar power generation conditions and improve the reliability of the system, the existing lead-acid batteries (low voltage) can be incorporated into the system to provide extra electic power. The lead-acid batteries are charged by the EV power batteries (high voltage) to maintain the voltage in a certain, steady range. Besides providing ancillary electric power, the lead-acid batteries function as the buffer between solar batteries and the air-conditioner to protect and stabilize the input voltage to the air-conditioner along with lithium-ion batteries, thereby the system’s robustness against the fluctuation of solar power generation can be enhanced. In addition, the electric energy consumed by the air-conditioner can be restored to lead-acid batteries by the excess solar PV power, so that the green energy substitution rate can be increased. 4. Through integraton of self-developed battery management and energy management control techniques, the state of charge (SOC) of lituium-ion batteries can still be balanced while the air-conditioner is running. In high SOC status, the energy management controller keeps its output voltage within the input voltage range of the DC/AC inverter, so that the air-conditioner can be charged while the battery management system can apply balanced charging to the lithium-ion batteries. 5. The air-conditioner controller employs a perturbation search algoroithm to explore the optimal coefficient of performance (COP) point and use it as the reference operation point for the air-conditioner through output flow control of evaporator. According to the experimental data collected in December, 2012 ~January, 2013, the COP of the developed solar air-conditioning system is able to reach ~2.0 in the environment temperature of 25 degrees Celsius with the evaporator output flow temperature of 17 degrees Celsius. Note that the value of the COP can be larger in higher environmental temperature.