Novel metallic alloys as phase change materials for heat storage in direct steam generation applications
Novel metallic alloys as phase change materials for heat storage in direct steam generation applications
复制标题
新型金属合金作为直接蒸汽发生应用中储热的相变材料
DOI：
10.1063/1.4949130
复制
发表时间：
2016
影响因子：
2.2
通讯作者：
M. Zubieta
中科院分区：
文献类型：
--
作者：
J. Nieto;I. Iparraguirre;Z. A. Velasco;I. Kaltzakorta;M. Zubieta
聚光太阳能发电（CSP）是关键的电力生产可再生能源技术之一，具有明显的独特优势：可以储存在晴天产生的热量，将其转化为可调度的技术。目前的CSP发电厂使用中间传热流体（HTF），导热油或无机盐，将热量从太阳能场（SF）传递到热交换器（HX）单元以产生高压蒸汽，该蒸汽可被引导到涡轮机用于发电或热能储存（TES）系统。近年来，一种新的光热发电技术引起了人们的极大兴趣：直接蒸汽发电（DSG）。通过抑制HX装置，直接使用水/蒸汽作为HTF将降低CSP工厂的投资成本。此外，水比导热油或盐更环保，不易燃，与容器材料（管道，水箱）兼容。然而，这项技术也面临着一些重要的挑战，这是优化TES系统的主要需求之一。在DSG中，从火用的角度来看，基于两个显热TES系统（用于水和过热蒸汽的预热）和一个潜热TES系统（用于水的蒸发（约70%的能量））的优化TES系统是优选的解决方案。这一概念已被广泛测试[1,2,3]，主要使用NaNO3作为潜热储存介质。其有趣的熔融温度（Tm）为306°C，考虑到驱动温差为10°C，这意味着TES在316°C下充汽条件为107 bar，在296°C下放电条件为81bar。从文献资料中得到的NaNO3的熔合热（ΔHf）平均值为178 J/g[4]。无机盐的主要缺点是它们的导热系数非常低（0.5 W/m.K），需要复杂的热交换设计。最近提出使用高导热共晶金属合金[5,6,7]作为一种可行的替代方法。这些共晶合金的Tms对于目前可用的DSG太阳能领域来说太高了，例如Mg49-Zn51合金在342°C熔化，需要超过160 bar的饱和蒸汽压力来给TES装置充电。考虑到这一点，设计了新型共晶金属合金，将Tms降低到285°C至330°C（分别为充注蒸汽压力79bar和145bar）， ΔHfs介于150至170 J/g之间，从而实现了适用于现有DSG技术的金属相变材料（PCM）。聚光太阳能发电（CSP）是关键的电力生产可再生能源技术之一，具有明显的独特优势：可以储存在晴天产生的热量，将其转化为可调度的技术。目前的CSP发电厂使用中间传热流体（HTF），导热油或无机盐，将热量从太阳能场（SF）传递到热交换器（HX）单元以产生高压蒸汽，该蒸汽可被引导到涡轮机用于发电或热能储存（TES）系统。近年来，一种新的光热发电技术引起了人们的极大兴趣：直接蒸汽发电（DSG）。通过抑制HX装置，直接使用水/蒸汽作为HTF将降低CSP工厂的投资成本。此外，水比导热油或盐更环保，不易燃，与容器材料（管道，水箱）兼容。然而，这项技术也有一些重要的挑战，作为…
Concentrating Solar Power (CSP) is one of the key electricity production renewable energy technologies with a clear distinguishing advantage: the possibility to store the heat generated during the sunny periods, turning it into a dispatchable technology. Current CSP Plants use an intermediate Heat Transfer Fluid (HTF), thermal oil or inorganic salt, to transfer heat from the Solar Field (SF) either to the heat exchanger (HX) unit to produce high pressure steam that can be leaded to a turbine for electricity production, or to the Thermal Energy Storage (TES) system. In recent years, a novel CSP technology is attracting great interest: Direct Steam Generation (DSG). The direct use of water/steam as HTF would lead to lower investment costs for CSP Plants by the suppression of the HX unit. Moreover, water is more environmentally friendly than thermal oils or salts, not flammable and compatible with container materials (pipes, tanks). However, this technology also has some important challenges, being one of the major the need for optimized TES systems. In DSG, from the exergy point of view, optimized TES systems based on two sensible heat TES systems (for preheating of water and superheating vapour) and a latent heat TES system for the evaporation of water (around the 70% of energy) is the preferred solution. This concept has been extensively tested [1, 2, 3] using mainly NaNO3 as latent heat storage medium. Its interesting melting temperature (Tm) of 306°C, considering a driving temperature difference of 10°C, means TES charging steam conditions of 107 bar at 316°C and discharging conditions of 81bar at 296°C. The average value for the heat of fusion (ΔHf) of NaNO3 from literature data is 178 J/g [4]. The main disadvantage of inorganic salts is their very low thermal conductivity (0.5 W/m.K) requiring sophisticated heat exchanging designs. The use of high thermal conductivity eutectic metal alloys has been recently proposed [5, 6, 7] as a feasible alternative. Tms of these proposed eutectic alloys are too high for currently available DSG solar fields, for instance the Mg49-Zn51 alloy melts at 342°C requiring saturated steam pressures above 160 bar to charge the TES unit. Being aware of this, novel eutectic metallic alloys have been designed reducing the Tms to the range between 285°C and 330°C (79bar and 145bar of charging steam pressure respectively) with ΔHfs between 150 and 170 J/g, and thus achieving metallic Phase Change Materials (PCM) suitable for the available DSG technologies.Concentrating Solar Power (CSP) is one of the key electricity production renewable energy technologies with a clear distinguishing advantage: the possibility to store the heat generated during the sunny periods, turning it into a dispatchable technology. Current CSP Plants use an intermediate Heat Transfer Fluid (HTF), thermal oil or inorganic salt, to transfer heat from the Solar Field (SF) either to the heat exchanger (HX) unit to produce high pressure steam that can be leaded to a turbine for electricity production, or to the Thermal Energy Storage (TES) system. In recent years, a novel CSP technology is attracting great interest: Direct Steam Generation (DSG). The direct use of water/steam as HTF would lead to lower investment costs for CSP Plants by the suppression of the HX unit. Moreover, water is more environmentally friendly than thermal oils or salts, not flammable and compatible with container materials (pipes, tanks). However, this technology also has some important challenges, being one of th...