Adeel Waqas

UTILIZATION OF LATENT HEAT STORAGE UNIT FOR COMFORT VENTILATION OF BUILDINGS IN HOT AND DRY CLIMATES

In hot and dry climatic conditions of South Asia, summer night temperatures are low, and phase change material (PCM) based heat storage technique could be used as heat sink to reduce ambient air temperature during hot day times, as an alternate of current ventilation techniques for the building sector. This can help in reducing electricity consumption and consequently reducing green house gas emissions. This study presents the analysis of PCM storage unit using cooler night temperatures for charging of storage material and later acting as a heat sink for hot ambient air during day time in hot and dry climatic conditions. The influence of air flow rates and melting point of PCM on the availability of comfort temperatures at storage unit outlet has been studied. The results clearly indicate the feasibility of PCM storage unit as a heat sink to keep ambient air within comfort limits during the hot day time in summer season. When the PCM melting temperature is equal to the comfort temperature of the hottest summer month, the storage unit performance is maximized for all the months during the summer season.

Phase Change Material (Pcm)-Based Solar Air Heating System For Residential Space Heating In Winter

This study presents the analysis of phase change material (PCM)-based solar air heating system to achieve comfort conditions in a living space during winter season. The technical feasibility of PCM-based solar air heating system has been demonstrated, thus reducing the risks due to indoor air pollution caused by the use of fossil fuel or biomass combustion devices. The most sensitive parameters affecting the performance of storage unit are the melting point of storage material, mass of PCM, and airflow rate. The simulation results considering various flow rates and melting temperature of PCM indicate that, when melting temperature of PCM is equal to the comfort temperature of all the winter months, the storage unit performance is maximized for all the months during winter season. A new parameter, heating capacity of the PCM, has been introduced to illustrate the performance of the PCM storage.

Performance analysis of phase-change material storage unit for both heating and cooling of buildings

Utilisation of solar energy and the night ambient (cool) temperatures are the passive ways of heating and cooling of buildings. Intermittent and time-dependent nature of these sources makes thermal energy storage vital for efficient and continuous operation of these heating and cooling techniques. Latent heat thermal energy storage by phase-change materials (PCMs) is preferred over other storage techniques due to its high-energy storage density and isothermal storage process. The current study was aimed to evaluate the performance of the air-based PCM storage unit utilising solar energy and cool ambient night temperatures for comfort heating and cooling of a building in dry-cold and dry-hot climates. The performance of the studied PCM storage unit was maximised when the melting point of the PCM was ∼29°C in summer and 21°C during winter season. The appropriate melting point was ∼27.5°C for all-the-year-round performance. At lower melting points than 27.5°C, declination in the cooling capacity of the storage unit was more profound as compared to the improvement in the heating capacity. Also, it was concluded that the melting point of the PCM that provided maximum cooling during summer season could be used for winter heating also but not vice versa.

Thermal behavior of a PV panel integrated with PCM-filled metallic tubes: An experimental study

The current research work aims to maintain high photovoltaic (PV) efficiency by keeping them at low operating temperature. For this purpose, commercially available phase change material (PCM) RT24 encapsulated in copper tubes was attached at the back side of a PV panel as a heat sink. The main concept of using the copper tube as PCM encapsulation is to produce a fin effect on the back of the PV panel to enhance the rate of heat transfer from the PV panel to ambient air. The experimental results showed that a maximum temperature reduction of 8.5 °C can be achieved at the front surface of the PV panel with 2.5 kg of PCM per square meter of the PV panel area. The PV back surface was also cooled down from 62 °C to 56 °C by the PCM. Enhancement in efficiency up to 3% was observed. The fin effect for the PV panel cooling was observed as the PV panel was maintained at a lower temperature, even after the PCM was completely utilized. The total cost incurred for the current PCM-based thermal regulation of the PV pa...

Effectiveness of the phase change material-based thermal energy storage integrated with the conventional cooling systems of the buildings – A review:

A significant portion of energy is consumed by the buildings to provide thermal comfort for its occupants. Energy consumed by the conventional cooling machines is expected to increase substantially around the globe. Cooling systems coupled with phase change materials offer a high potential to minimize the cooling energy demand and shifting peak time cooling load to off-peak time period without compromising the indoor comfort conditions. The interest in phase change material utilization for cooling applications has been increasing significantly over the last decade because of their energy saving benefits in building sector. Therefore, in this work, effectiveness of the phase change material storage coupled with free cooling, evaporative cooling, and compressor-based cooling techniques in reducing the energy consumption or shifting the peak cooling load have been discussed and analyzed in detail. Different types of phase change materials used for active cooling systems along with their selection criteria for a particular application have been elaborated and discussed. Techniques to estimate the thermophysical properties of phase change material have also been explained. Phase change material capsulation techniques along with their merits and demerits are also described. Challenges and issues that may arise during integrating of phase change material storage with the active cooling system have also been explained. Finally, this review also presents some current problems that needed further research in this area. Current review will be a useful guide for the research community working or intending to work in the field of phase change material-based cooling system.

Thermal management of conventional photovoltaic module using phase change materials—An experimental investigation

The electrical conversion efficiency of the monocrystalline photovoltaic module is adversely affected due to the higher temperature of the solar cells. Therefore, cooling technologies to remove the excess heat generated by the photovoltaic modules play a vital role to enhance its output. In this article, thermal management of the conventional monocrystalline photovoltaic modules using phase change material has been experimentally evaluated. Phase change material with a melting point of 30°C to 32°C was encapsulated in the aluminium tubes that were 500 mm long having 19 mm inner diameter. Phase change material-filled tubes were attached to the rear side of the photovoltaic module at an equal distance to cover the module area of 0.30 m2. The total mass of the phase change material used in the current experimental study was 1.0 kg. The average temperature of the modified photovoltaic module was 2.4°C to 2.8°C lower than conventional photovoltaic module during sunshine hours. The peak temperature of the conventional photovoltaic panel was lowered from 6°C to 9°C due to the inclusion of phase change material. The electrical conversion efficiency enhanced up to 2.0%. The current configuration of integrating phase change material with photovoltaic modules was observed advantageous as it assisted in enhancing the natural convection from the back of the photovoltaic module rather suppressing. An energy balance showing the trend of energy losses from conventional photovoltaic and photovoltaic with phase change material is also presented and discussed.

Utilizing built infrastructure and otherwise non-utilizable space for solar PV power projects—A case study for an educational institution

Ground mounted solar PV systems utilize a large amount of land that could otherwise be used for different developmental activities, such as agricultural growth, fuel crops production, and industrial development. Utilizing the already built infrastructures such as building rooftops, parking sheds, and canal water systems for installation of solar PV projects has proven beneficial as it minimizes the procurement and opportunity cost of the land. Taking into consideration the best practices adopted globally, Pakistan must evolve its policy for a shift towards utilization of existing infrastructures rather than using prime lands for solar PV power projects. Building Integrated Photovoltaic (BIPV) systems have been effective for deployment and penetration of solar PV technology (SPVT) in different countries. In this paper, we present a case study, established on the basis of existing BIPV principles followed in developed countries. This case study proposes to utilize existing storm water drains, parking lots, ...

Modelling of a solar energy driven water desalination system using TRNSYS

The overall broad purpose of this paper is to develop and evaluate a small scale solar humidification dehumidification water desalination system using a graphical tool TRNSYS and assess its thermal behavior. Considering the intense need for the development of alternate technologies for energy deficient and impoverished countries of the world like Pakistan, this model is in particular anticipated for underprivileged communities where pure and uncontaminated drinking water as well as modern technologies are not accessible. The system consists of isolated components for heating, evaporation and condensation, in order to lower the thermal losses. The weather file used was in standard TMY 2 format for Asian data. A flat plate solar collector, humidifier and dehumidifier are to be integrated in an open air open water configuration. The simulations for a water heated cycle revealed that the output water temperature be reliant strongly on the incident solar radiations and inlet water temperature. Collector area and inlet water flow rate also had a considerable impact on productivity. A significant increase in efficiency was observed by using a water storage tank and pre heating the feed water favorably influenced the output.

Comparative study of wax and nitrate salts for thermal storage for a 500 W fresnel mirror solar concentrator

The demand and supply gap of global energy needs is increasing exponentially. This situation is further worsening as the conventional fossil fuel resources are decreasing. Solar thermal is one of the alternatives that can be used to fulfil the power requirements of the world without effecting the environment. Solar is one of the widely available renewable energy resources around the globe. One of the key challenges in harvesting this resource is that it is intermittent, thus its availability is limited. Several techniques are used to overcome this challenge, the method being used now is hybrid technology of conventional and solar; where solar is being used in peak hours. Another technique is to store the excess energy present during day and utilize it during night by using phase change material. This paper presents a comparative study between two phase change materials; nitrate salts and wax for energy storage of a 500 Watt Fresnel Mirror Solar Concentrator. A comparison between their thermal storage capacities, their charge and discharge time is made using CFD tool like COMSOL.

Assessment of most suitable location for solar feed in tariff policy implementation in Pakistan

A shift towards alternate and renewable energy sources is inevitable in Pakistans current energy demand scenario. Electricity supply shortfall, exhausting extractable oil and gas resources, extensive reliance on imported crude oil and climate change are major drivers for the shift towards renewable energy alternatives. Since high electricity generation cost of renewable energy technologies remain a major hurdle, it is countered through introducing RE support and policy measures such as Tax Rebates, Capital Subsidies, Feed in Tariff and Net Energy Metering policies etc. Pakistan introduced its Feed in Tariff support policy for integration of renewable energy into the national grid. National Electricity and Power Regulatory Authority (NEPRA), a regulatory body, set two different tariffs for solar PV FiT projects in northern and southern regions of the country based on varying solar irradiation. In the light of tariff set by the regulatory authority and simulations performed with Polysun 6.2, for an identical nameplate capacity solar PV projects in different cities, an economic comparison in terms of Payback Period and Net Present Value has been conducted to assess the most suitable location for solar PV installations in Pakistan, as per which Peshawar turned out to be the most financially lucrative location for implementation of solar FiT projects in Pakistan.