利用蓄冷熱替代蓄電的太陽能空調系統研究

Abstract

台大新能源中心開發的「混合型發電自用太陽光發電系統」(hybrid PV system HyPV)主要用來推動空調機，太陽光發電與冷氣負載同步，又因空調機開機時段不一定與太陽光發電同步(例如白天不使用空調機)，必須設置昂貴的蓄電池蓄電。本研究將空調機設計成具有儲能(冷或熱)的功能，稱為「儲能式太陽能空調系統(HyPV-Z)」，利用白天多餘太陽電力由空調機儲冷熱，用水當介質，替代蓄電，並且可回收廢冷或廢熱。本研究共開發三種系統進行實測: 1. HyPV-Z1: 所儲存的冷能，透過冷房的冷水器(Fan-coil unit, FCU)釋冷，減少空調機負荷(省電)達到間接利用多餘太陽電力目的(蓄冷替代蓄電)。 2. HyPV-Z2: 為HyPV-Z1 的改良型I，將原設置於冷房的FCU 移到室外機側(冷凝器)，將多餘太陽電力所儲存的冷能用來冷卻變頻空調機的冷凝器，降低冷凝溫度，提高變頻空調機的COP。 3. HyPV-Z2a: 將HyPV-Z1 的改良型I (HyPV-Z2)空氣換熱器取消，直接將多餘太陽電力所儲存的冷水用來冷卻串聯在變頻空調機冷凝器後端的水冷器(water cooler)，降低冷凝溫度，提高變頻空調機的COP。 由測試結果獲致如下結論: 1. 實驗證明，三種儲能式太陽能空調系統都可以用蓄冷熱替代蓄電，降低太陽光發電系統的成本。 2. HyPV-Z1 先利用太陽能多餘的電來製冷水並儲存於儲能桶(模式C)，等使用冷氣時，再將冷水送至冷房FCU 進行室內降溫，減少空調機耗電，此時儲能空調機冷氣模式(Ap 模式)的COP 平均6.01，比原機的冷氣性能(A 模式)COP平均5.2 提高，所降低的耗電量等於太陽餘電量，太陽餘電儲冷可以完全替代蓄電。 3. HyPV-Z2(改良型I)在暖氣運作時，先利用太陽能餘電製熱水並儲存於儲能桶(模式D)，於使用冷氣時，再將熱水送至水排對室外機的蒸發器釋熱，其COP 達6.04，相較於原空調機暖氣模式(B 模式) COP 5.2 提升約30%，證明太陽餘電儲熱可以替代蓄電。 4. HyPV-Z2a(改良型II)利用HyPV 多餘太陽電力蓄冷(Ce 模式)之COP 可達4.33，於冷氣機啟動時利用儲存的冷水釋冷(Ae 模式)的COP 可達6.62，比原機冷氣運轉(模式A)之COP (4.66) 提升42%，亦即可將太陽餘電利用儲冷轉移至冷氣運轉時刻應用。

The hybrid PV system (HyPV) developed by NTU is used to drive air conditioners which operation may not be in phase with solar radiation and expensive battery storage may be needed. An air conditioner with thermal storage is developed in the present study to replace battery storage, called “HyPV-Z”, which utilizes excess PV power to converted into thermal energy to store in hot or cold water tank. Three kinds of systems are developed: 1. HyPV-Z1: using a FCU (fan-coil unit) installed in cooling room to utilize the stored cold water for cooling of room. 2. HyPV-Z2: improvement I of PV-Z1 to move the FCU to outdoor to cool the condenser to reduce power consumption of air conditioner. 3. HyPV-Z2a: improvement II of PV-Z1 to eliminate the outdoor FCU and direct cool the heat exchanger after the condenser to reduce condenser temperature. The following conclusions are made by the research: 1. Three systems developed are proved experimentally to be able to use thermal storage to replace battery to reduce the HyPV-A cost. 2. HyPV-Z1 utilize excess PV power for cold storage and released when air conditioning is turned on. The COP reaches 6.01 which is higher than the original air conditioner before modification with COP 5.2. This proves the cold storage is effective in replacing battery storage. 3. HyPV-Z2 obtainCOP 6.04 running in heating mode with heat release from the hot storage. This is about 30% higher than the COP of the original air conditioning running in heat mode. This proves the hot storage is effective in replacing battery storage. 4. HyPV-Z2a obtain a COP 4.33 when running with cooling mode with cold release fro the cold storage, about 42% higher than that of the original air conditioner running in cooling mode. This proves the cold storage is effective in replacing battery storage.