Innovative Sustainable Water Desalination system using a heat pump with conventional or solar energy

Water Desalination is one of the most vital topics all over the world. This is due to the limited high quality water resources and the rapid increase in world population, urbanization and industrialization. Certain places in the world especially in arid and semi-arid regions suffer from a lack of natural pure water resources. The Kingdom of Saudi Arabia is one of the countries that suffer from this problem. That explains why the Kingdom has become the world first desalinated water producers with variety of desalination technologies; mainly, MSF, MED and RO. The abundant solar energy is a motive to many attempts to make use of this available energy to desalinate water. Medium to small-scale system that can use solar energy to desalinate water include Humidification dehumidification systems. The reason is that such systems require low-grade energy to reach a maximum temperature of about 80oC that can be achieved easily through solar energy. The major concern with HDH system lies in their lower GOR (Gained output ratio) compared to conventional systems. Although the solar energy is free, efficient utilization is an important issue. It is therefore important to exceed the maximum limit of the GOR practically achieved (4.5). The proposed design of the HDH thermal desalination systems is a step in this direction. A water heated HDH system for example is made of a humidifier (where air is humidified through direct contact with hot water), the humid air is then dehumidified in a condenser (dehumidifier) where pure liquid water condenses and collected. The energy released by vapor condensing in the dehumidifier is gained by cold water used for the condensation process by passing it inside a pipe where it is preheated is then admitted to a water heater to be heated before it is sprayed in the humidifier. Preheating of water is a sort of energy recovery that helps enhance the system GOR. The required heat for the HDH system in this proposal will rely on using a heat pump to provide the required energy to heat water. Hot water enters to the humidifier to be sprayed. Since the Heat pump would have a COP of about 3 or more, one third of the energy needed to heat the water will be provided for the system in the form of work to the compressor, the condenser will release sufficient amount of heat to heat the water. The HDH system will be designed, sized for a given distillate flow rate. Then the rate of heat transfer will be identified to desalinate this rate of water. Then, the heat pump will be sized, selected and connected. The heat pump can operate by connecting it to the electric power or to an outlet of a PV system to convert solar energy to electric power. Both modes will be tried. Furthermore, heat pump operation mode will be changed from air to water mode into water to water mode and finally seawater to water mode to see which is the most effective way to deliver heat to the HDH system and results in the highest GOR. The proposed work will include simulations assisted by experimental work