Abstract:In developing countries like Pakistan, the capacity shortage (CS) of electricity is a critical problem. The frequent natural gas (NG) outages compel consumers to use electricity to fulfill the thermal loads, which ends up as an increase in electrical load. In this scenario, the authors have proposed the concept of a combined heat & power (CHP) plant to be a better option for supplying both electrical and thermal loads simultaneously. A CHP plant-based microgrid comprising a PV array, diesel generators and batteries (operating in grid-connected as well as islanded modes) has been simulated using the HOMER Pro software. Different configurations of distributed generators (DGs) with/without batteries have been evaluated considering multiple objectives. The multiple objectives include the minimization of the total net present cost (TNPC), cost of generated energy (COE) and the annual greenhouse gas (GHG) emissions, as well as the maximization of annual waste heat recovery (WHR) of thermal units and annual grid sales (GS). These objectives are subject to the constraints of power balance, battery operation within state of charge (SOC) limits, generator operation within capacity limits and zero capacity shortage. The simulations have been performed on six cities including Islamabad, Lahore, Karachi, Peshawar, Quetta and Gilgit. The simulation results have been analyzed to find the most optimal city for the CHP plant integrated microgrid.

No abstract

The benefits of thermal energy storage using phase change materials are well documented in the literature. Despite all the potential benefits of thermal energy storage, its commercial and widespread application remains limited. This is due to the high initial cost of phase change materials, extensive rework required in buildings, major modifications in HVAC systems, and the potential for leakage, fire and toxicity hazards. There is a strong need for a simple thermal energy storage solution which can be adopted by large number of consumers. Ductless split air-conditioners are portable, low cost, efficient and account for 70% of all air-conditioning systems sold worldwide each year. The present research provides a novel and low cost solution that incorporates thermal energy storage in these air conditioners, allowing them to run without electricity for 3 h. The paper deals with the detailed design aspects and engineering challenges that arise when incorporating thermal energy storage in these small units. A prototype air-conditioner with in-built thermal energy storage was developed, and all performance parameters presented have been validated through data obtained from the prototype. Our results indicate that thermal energy storage can be incorporated in split units in low cost and with minimal drop in overall energy efficiency of the system. Practical application: Incorporating thermal energy storage in split air-conditioners which enables them to run without grid for many hours has immense practical applications. Since around 50% power in any building is consumed by HVAC systems, being able to provide cooling during peak hours without using grid can significantly reduce load on the grid without compromising user comfort. For developing countries where load shedding is frequent, the users can run these air-conditioners without the use of generators or batteries thus saving costs and the environment.

No abstract

No abstract