Zakaria Mohd. Amin

Desalination With a Solar-Assisted Heat Pump: An Economic Optimization

The solar-assisted heat pump (SAHP) desalination, based on the Rankin cycle, operates in low temperature and utilizes both solar and ambient energy. An experimental SAHP desalination system has been constructed at the National University of Singapore, Singapore. The system consisted of two main sections: an SAHP and a water distillation section. Experiments were carried out under the different meteorological condition of Singapore and results showed that the system had a performance ratio close to 1.3. The heat pump has a coefficient of performance of about 8, with solar collector efficiencies of 80% and 60% for evaporator and liquid collectors, respectively. Economic analysis showed that at a production rate of 900 L/day and an evaporator collector area of around 70 m2 will have a payback period of about 3.5 years.

Steel SIPs for Residential Building Construction: Lessons from Air Leakage and Thermography Analysis of Australian Houses

Freely access on publisher website Stick-frame residential construction is renowned for being leaky. Structural insulated panels (SIPs) theoretically resolve the issues with air and thermal leakage, but such construction systems are new to the Australian housing market. The purpose of this study was to determine the extent to which a steel-skinned SIP construction product could resolve air leakage and thermal performance challenges in five climate zones across Australia in 2015. All houses used the same steel SIPs as the main construction element (walls and roof). Airtightness and thermography tests were conducted in each house in winter to identify air and thermal leakage paths. The results show that even first-time users of this product can produce well-sealed homes, but there is a need to address thermal bridging (because of the steel componentry) and to consider the house as a whole system (not just walls and roof). The results of the study raise questions about thermography test procedures and airtightness regulations for naturally ventilated homes in warm-temperature climates. Addressing these issues will assist in the diffusion of innovative construction products and methods to enhance the energy efficiency of housing.

Analytical modelling of integrated solar drying system

The drying of fruit and vegetables is a subject of great importance. Dried fruit and vegetables have gained commercial importance, and their growth on a commercial scale has become an important sector of the agricultural industry. However, food drying is one of the most energy intensive processes of the major industrial process and accounts for up to 15 % of all industrial energy usage. Due to increasingly high electricity prices and environmental concern, a dryer using traditional energy sources is not a feasible option anymore. Therefore, an alternative/renewable energy source is needed. In this regard, an integrated solar drying system that includes highly efficient double-pass counter flow v-groove solar collector, conical-shaped rock-bed thermal storage, auxiliary heater, the centrifugal fan and the drying chamber has been designed and constructed. Mathematical model for all the individual components as well as an integrated model combining all components of the drying system has been developed. Mathematical equations were solved using MATLAB program. This paper presents the analytical model and key finding of the simulation.

Modelling Conical Rock-Bed Solar Thermal Storage Tank

An important application of solar thermal storage is for power generation or process heating. Low-temperature thermal storage in a packed rock bed is considered the best option for thermal storage for solar drying applications. In this chapter, mathematical formulations for conical have been developed. The model equations are solved numerically for charging/discharging cycles utilizing MATLAB. Results were compared with rock-bed storage with standard straight tank. From the simulated results, the temperature distribution was found to be more uniform in the truncated conical rock-bed storage. Also, the pressure drop over a long period of time in the conical thermal storage was as low as 25 Pa. Hence, the amount of power required from a centrifugal fan would be significantly lower. The flow of air inside the tank is simulated in SolidWorks software. From flow simulation, 3D modelling of flow is obtained to capture the actual scenario inside the tank.

Mathematical Modelling and Experimental Validation of Solar Assisted Heat Pump System

Singapore is located at the equator, with abundant supply of solar radiation, relatively high ambient temperature and relative humidity throughout the year. The meteorological conditions of Singapore are favourable for efficient operation of solar energy based systems. Solar assisted heat pump systems are built on the roof-top of National University of Singapore’s Faculty of Engineering. The objectives of this study include the design and performance evaluation of a solar assisted heat-pump system for water desalination, water heating and drying of clothes. Using MATLAB programming language, a 2-dimensional simulation model has been developed to conduct parametric studies on the system. The system shows good prospect to be implemented in both industrial and residential applications and would give new opportunities in replacing conventional energy sources with green renewable energy.

Water Heating and Dehumidification With Heat Pump Utilizing Solar, Ambient and Waste Heat

The low temperature operation of a heat pump makes it an excellent match for the use of solar energy. At the National University of Singapore, a solar assisted heat pump system has been designed, fabricated and installed to provide water heating and drying. The system also utilizes the air con waste heat, which would normally be released to atmosphere adding to global warming. Experimental results show that the two-phase unglazed solar evaporator-collector, instead of losing energy to the ambient, gained a significant amount due to low operating temperature of the collector. As a result, the collector efficiency attains a value greater than 1, when conventional collector equations are used. With this evaporator-collector, the system can be operated even in the absence of solar irradiation. The waste heat was collected from an air-con system, which maintained a room at 20–22 °C. In the condenser side, water at 60 °C was produced at a rate of 3 liter/minute and the drying capacity was 2.2kg/hour. Maximum COP of the system was found to be about 5.5.Copyright

Conversion of Seawater to Fresh Water: An Experiment With a Solar Assisted Heat Pump

Seawater desalination is one of the most suitable areas for the utilization of solar thermal energy due to the coincidence, in many places of the world, of water scarcity, seawater availability and good levels of solar irradiation. The solar assisted heat pump provides a new horizon in the seawater desalination. Experiments were conducted on solar assisted heat pump desalination system under meteorological conditions of Singapore. This system uses two types of flat-plate solar collectors. One is called evaporator-collector which is entirely unglazed. The other type is single-glazed collector used for feed water heating. A single stage MED (multi-effect distillation) evaporator is used in this system and the refrigerant R134a is used in the heat pump. The system has a Performance Ratio (PR) of around 1.3 and water production capability of 0.6 to 0.9 kg/hr. The Coefficient of Performance (COP) of the heat pump reaches a maximum value of about 9 for the meteorological conditions of Singapore.Copyright