This Small Business Innovation Research Phase I project will build a proof-of- concept unit of a high efficiency and low cost liquid desiccant dehumidifier that can be activated by heat at a temperature as low as 140o Farenheit, such as that from the low cost solar water heaters and condensers of air conditioners designed to be integrated with such dehumidifiers. Such low level heat currently cannot be economically used, while the existing dehumidification systems rely on the inefficient process of cooling air to a very low temperature and then heating it up again, wasting a lot of energy. The thermal coefficient-of- performance of Xunergy?s dehumidifier is expected to be on the order of 0.9, much higher than those of existing systems, and the humidifier uses an essentially non-corrosive and safe liquid desiccant and therefore is expected to be of low in cost and long-lasting. Such a system will be particularly cost effective for conditioning of ventilation air in hot and humid climates.
The broader impact/commercial potential of this project are allowing for low level heat such as that from low cost solar water heaters and that from condensers of air conditioners to be used for driving conditioning of ventilation air with a low cost and long lasting system, greatly reducing the energy and other costs of conditioning of ventilation air, emission of greenhouse gases due to the use of energy and the leaked refrigerant, and reducing the peak electricity demand, especially on hot and humid days when the grid is strained. The lower cost of ventilation air conditioning is also likely to help make air fresher and healthier in public buildings such as hospitals, schools, theaters, indoor markets etc. without increasing cost.
i) Due to the currently relatively small solar water installation base in this country, we concluded the best fit of this technology for application in US is to use the heat from air conditioner condensers. We therefore modified our initial process design so that the system is optimal for using the heat from air conditioners. A process and instrumentation diagram was developed based on this process for the project. Such a process is expected to be used for prototype design and construction in Phase II. ii) We initially chose shell-and-tube with some special features for the absorber and stripper of the proof-of-concept unit although we planned to use a planar design for the prototype during Phase II of the project. Fabrication of the absorber and striper using such a design turned out to be more costly and time-consuming than originally anticipated. We were able to develop a relatively simple planar absorber and stripper design that is easy to manufacture and has the desired flow patterns for good mass transfer and heat transfer. We therefore concluded that the planar design is indeed the way to go, and will focus our future efforts on planar configurations using low cost and relatively high thermal conductivity materials, collect test data to confirm the expected COP values, and build the prototype with this or a similar planar design in Phase II. Last Modified: 01/16/2013 Submitted by: Jianguo Xu We successfully built and ran the proof-of-concept unit and obtained COP values in excess of 0.8, our initial target in the Phase I proposal, and achieved the desired moisture removal levels. We therefore declare that our mission was accomplished as we defined in our Phase I proposal. We also identified areas for further efficiency improvement which we expect to add 5-10% efficiency improvement. Our experiment with an all plastic air heater shows that it can indeed be a good low cost (and corrosion resistant) way for making low cost and durable heat exchangers. This gives us a lot of confidence in using this low cost and long lasting material as the main material for making absorber, stripper, and heat exchangers in the future. We expect such a choice of materials of construction will greatly reduce the cost of such systems and make these key components very durable.
