Caloric Systems for Cooling, Heating, and Work

全球对热服务的需求，包括空间冷却、加热、制冷和储热，约占全球能源消耗的40-50%。根据劳伦斯伯克利国家实验室最近的一项研究，到2030年，全球可能会增加7亿台空调，到2050年将增加16亿台。这只是新需求如何导致额外发电和温室气体排放的一个例子，“就像在世界上增加了几个新国家”。目前的加热和冷却技术已经成熟，但使用的工作流体存在臭氧消耗、全球变暖和安全问题。全球正在努力使替代技术商业化，使用固体材料的新循环已被确定为有希望的替代方法。******发热材料是固体物质，具有一种或多种可逆的工作模式，由其主导的有序模式定义。例子包括磁热学（MC磁性顺序）、弹性热学（eC结构顺序）和电热学（eC电气顺序）。具有一种以上工作模式的材料是多色的。特别感兴趣的是表现出一阶相变的材料，其熵随温度和应用场的变化很大。实际上，热材料的使用类似于蒸汽压缩系统，其中绝热功输入导致可逆的温度变化。*** ***在加热或冷却系统中使用发热材料的挑战之一是可逆温度变化的幅度，以及响应显著的温度范围。为了克服这个问题，主动热再生器（ACR）在分层再生器结构中使用一种或多种材料，从而产生级联循环。实际上，热量从一个位置或材料被泵送到下一个位置或材料，跨越所需的温度范围。许多发热材料都有类似的问题，即相对于温度和场的有限热响应，这表明需要ACR循环。******这项研究计划的目标是开发有效的热量系统进行能量转换。本文涉及三个方面：(1)发展我们对热热力学的理解，(2)确定能够实现高性能的过程，(3)开发具有成本效益的高效设备。

Global demand for thermal services including space cooling, heating, refrigeration, and thermal storage is responsible for approximately 40-50% of global energy consumption. According to a recent study from Lawrence Berkeley National Laboratory, the world may see an additional 700 million air conditioners by 2030, and 1.6 billion of them by 2050. This is but one example of how new demands can result in additional electricity generation and GHG emissions “like adding several new countries to the world.” Current technologies for heating and cooling are mature, but use working fluids with ozone depletion, global warming, and safety concerns. A global effort is underway to commercialize replacement technologies new cycles using solid materials have been identified as promising alternatives.******Caloric materials are solid substances with one or more reversible work modes defined by their dominant ordering mode. Examples include magnetocaloric (MC magnetic order), elastocalorics (eC structural order), and electrocalorics (EC electrical order). Materials with more than one work mode are multicaloric. Of particular interest are materials exhibiting first order phase transformations providing large changes in entropy with temperature and applied field. In practice, the use of caloric materials is analogous to vapour-compression systems where adiabatic work input results in a reversible temperature change.*** ***One of the challenges of using caloric materials in heating or cooling systems is the magnitude of the reversible temperature change, and the temperature range over which the response is significant. To overcome this, an active caloric regenerator (ACR) uses one or more materials in a layered regenerator structure so that a cascade of cycles is created. In effect, heat is pumped from one location, or material, to the next, across a desired temperature span. Many caloric materials suffer from similar problems of limited caloric response with respect to temperature and field suggesting the need for an ACR cycle.******The objective of this research program is to develop efficient caloric systems for energy conversion. Three areas are addressed: (1) developing our understanding of caloric thermodynamics, (2) determining the processes which enable high performance, (3) developing efficient devices that are cost effective.