2段ランキンサイクルを用いた海洋温度差発電システム(Double-Stage Rankine Cycle for Ocean Thermal Energy Conversion)
- 標題
- 2段ランキンサイクルを用いた海洋温度差発電システム(Double-Stage Rankine Cycle for Ocean Thermal Energy Conversion)
- 作者
- 森﨑敬史・池上康之(Takafumi Morisaki and Yasuyuki Ikegami)
- 文件屬性
- 日本研究
- 知識分類
- 能源利用
- 出版年
- 2014
- 刊名
- 海洋深層水研究
- 卷
- 14
- 期
- 3
- 頁
- P185-195
- 點閱數
- 2529
摘要
海洋温度差発電（OTEC) は，エネルギーおよび環境問題が深刻化する中，再生可能な自然ェネ ルギーのーつとして注目されている． このOTECの一層の高効率化のために，近年，非共沸混合 媒体であるアンモニア／水を作動流体として用い熱交換器における不可逆損失を低減させるための 種々のサイクルが検討されている．一方，非共沸混合媒体を用いるため熱交換器における熱伝達係 数の低下が懸念される． そこで，本研究では，作動流体に純媒体を用いて熱交換器における不可逆 損失を低減させるための2 段ランキンサイクルに注目した． そのサイクル特性および有効性を明ら かにするために，新しい性能解析を行った． さらに，このシステムと一般的な（単段）ランキンサ イクルおよびカリーナサイクルとの比較を行った，その結果，伝熱性能が高い場合，2段ランキン サイクルは，最大出力時で，ランキンサイクルより約15%，カリーナサイクルより約2％出力が高 くなることが明らかとなった．
Ocean Thermal Energy Conversion (OTEC) is able to supply stable electric power and presents a variety of integrated applications. The thermal efficiency of the cycle using pure substance as working fluid that converts thermal energy of the ocean into work increases with a decrease of irreversible losses in the cycle or an increase of the effective temperature difference between evaporating and condensing temperature of the working fluid. Therefore, improvement in the system performance is achieved by decreasing the irreversible losses in the evaporators and the condensers. This paper investigates the thermal performance of Double-stage Rankine (D-Rankine) cycle that employs independent equipment in two Rankine cycles. The D-Rankine cycle was com-pared with the Single-stage Rankine (S-Rankine) cycle as well as Kalian cycle and has shown the best performance in terms of maximum output power. The advantage of using two independent cycles is that it decreases irreversible losses in the heat exchangers. As a result, in the case of equal working fluid flow rates in D-Rankine cycle, the warm and the cold water temperature differences in cycles-No.1 and -No.2 are almost identical. The difference of power output between D-Rankine cycle and S-Rankine cycle at a fixed thermal efficiency increases with an increase of the thermal performance of the heat exchangers. In the case of high thermal performance, the maximum power output of D-Rankine cycle is about 15% and 2% higher than that of 5-Rankine cycle and Kalina cycle, respectively.
Ocean Thermal Energy Conversion (OTEC) is able to supply stable electric power and presents a variety of integrated applications. The thermal efficiency of the cycle using pure substance as working fluid that converts thermal energy of the ocean into work increases with a decrease of irreversible losses in the cycle or an increase of the effective temperature difference between evaporating and condensing temperature of the working fluid. Therefore, improvement in the system performance is achieved by decreasing the irreversible losses in the evaporators and the condensers. This paper investigates the thermal performance of Double-stage Rankine (D-Rankine) cycle that employs independent equipment in two Rankine cycles. The D-Rankine cycle was com-pared with the Single-stage Rankine (S-Rankine) cycle as well as Kalian cycle and has shown the best performance in terms of maximum output power. The advantage of using two independent cycles is that it decreases irreversible losses in the heat exchangers. As a result, in the case of equal working fluid flow rates in D-Rankine cycle, the warm and the cold water temperature differences in cycles-No.1 and -No.2 are almost identical. The difference of power output between D-Rankine cycle and S-Rankine cycle at a fixed thermal efficiency increases with an increase of the thermal performance of the heat exchangers. In the case of high thermal performance, the maximum power output of D-Rankine cycle is about 15% and 2% higher than that of 5-Rankine cycle and Kalina cycle, respectively.