Effect of Thermal Bridges in Insulated Walls on Air-Conditioning Loads Using Whole Building Energy Analysis

Thermal bridges in building walls are usually caused by mortar joints between insulated building blocks and by the presence of concrete columns and beams within the building envelope. These bridges create an easy path for heat transmission and therefore increase air-conditioning loads. In this study, the effects of mortar joints only on cooling and heating loads in a typical two-story villa in Riyadh are investigated using whole building energy analysis. All loads found in the villa, which broadly include ventilation, transmission, solar and internal loads, are considered with schedules based on local lifestyles. The thermal bridging effect of mortar joints is simulated by reducing wall thermal resistance by a percentage that depends on the bridges to wall area ratio (TB area ratio or Amj/Atot) and the nominal thermal insulation thickness (Lins). These percentage reductions are obtained from a correlation developed by using a rigorous 2D dynamic model of heat transmission through walls with mortar joints. The reduction in thermal resistance is achieved through minor reductions in insulation thickness, thereby keeping the thermal mass of the wall essentially unchanged. Results indicate that yearly and monthly cooling loads increase almost linearly with the thermal bridge to wall area ratio. The increase in the villa’s yearly loads varies from about 3% for Amj/Atot = 0.02 to about 11% for Amj/Atot = 0.08. The monthly increase is not uniform over the year and reaches a maximum in August, where it ranges from 5% for Amj/Atot = 0.02 to 15% for Amj/Atot = 0.08. In winter, results show that yearly heating loads are generally very small compared to cooling loads and that heating is only needed in December, January and February, starting from late night to late morning. Monthly heating loads increase with the thermal bridge area ratio; however, the variation is not as linear as observed in cooling loads. The present results highlight the importance of reducing or eliminating thermal bridging effects resulting from mortar joints in walls by maintaining the continuity of the insulation layer in order to reduce energy consumption in air-conditioned buildings

Improved Prediction Model and Utilization of Pump as Turbine for Excess Power Saving from Large Pumping System in Saudi Arabia

The throttling process is frequently encountered in many industrial practices utilizing Pressure Reducing Valves (PRVs). This process is typically used to control pressure and flow in pipeline networks. The practice of utilizing PRVs is considered simple and cheap in terms of installation cost and control. It dissipates the excess fluid energy that can be used for other purposes. This paper studies the feasibility of utilizing the Pump as Turbine (PAT) concept to partially recover the excess power dissipated from PRVs located at the discharge lines of refined product shipping pumps at one of the hydrocarbon distribution facilities in Saudi Arabia. Multiple PAT installation layouts have been studied to achieve this goal, selecting the optimum option to maximize the power recovery. The final selection of PAT was conducted to achieve a reasonable payback period. A new method for predicting the pump performance in reverse mode was developed depending on the manufacturer’s pump performance curves. The comparison of the proposed model with experimental data and previous models for three modes of operation reveals that the proposed model in this paper’s results either have the minimum deviation or the second minimum deviation out of all models. In the case of flow ratio prediction, the predicted deviation is merely 3.83%, −1.14%, and 1.35% in three modes of operation. For power prediction, the proposed model is the best and the only reliable model out of all with the least deviation of −7.48%, 0.07%, and −3.16% in three modes of operation. The economic analysis reveals the Capital Payback Time (CPP) for five optimum PATs is around 5 years. The new method was also validated against previous models showing more precise performance prediction of multistage centrifugal pumps running in turbine mode

Recycling Discarded Facemasks of COVID-19 Pandemic to New Novel Composite Thermal Insulation and Sound-Absorbing Materials

The COVID-19 pandemic has forced the whole world to wear single-use disposable facemasks for health protection. Studies have shown that about 129 billion facemasks are wasted each month, which will contaminate the environment and create a big problem in getting rid of them. These discarded facemasks are usually dumped in garbage bins, in landfills, or in some cases littering them on the streets, which creates a health hazard to human beings. In order to solve such environmental problems, the current study presents new novel composite materials developed by recycling discarded facemasks. These materials have great potential to be used for both thermal insulation and sound-absorbing for building walls. Experiments have been performed to make bound composite materials using the discarded facemasks as new raw materials with wood adhesive as a binder. The discarded facemasks were first heated for one and half-hour at 120 °C to kill any contaminants (biological or others). Five different composites are made: the first uses the complete facemasks, the second uses facemasks with iron nose clip only, the third uses facemasks with no both ear loops and iron nose clip, the fourth one contains the elastic ear loops only, and the fifth one has facemasks with elastic ear loops only. Coefficients of thermal conductivity for the five samples are obtained as 0.0472, 0.0519, 0.05423, 0.0619, 0.0509 (#5, e), and 0.04347 (#5, f) W/m K at 25 °C, respectively. The sound-absorbing coefficient for samples 1, 2, and 3 is above 0.5 in general and, at some frequencies, approaches 0.8. Results show that the soft samples with low binder concentration have a good sound absorbing coefficient at high frequency, while the one with high binder concentration has that at a low frequency for the same facemasks’ mass. Mechanical properties of all samples are also reported by performing the three-point bending moment. Composite samples have a low moisture content (0.2%) and have high thermal stability up to 325 °C. These composite samples could replace the petrochemical and synthetic thermal insulation materials and, at the same time, get rid of the huge discarded waste facemasks, which is considered a huge environmental problem

Characterization of Low-Cost Particulates Used as Energy Storage and Heat-Transfer Medium in Concentrated Solar Power Systems

Utilizing solid particles as a heat-transfer medium in concentrated solar power applications has gained growing attention lately. Unlike molten salts, solid particles offer many benefits, which include: high operating temperatures (greater than 1000 °C), a lack of freezing issues and corrosivity, abundant availability, high thermal energy storage capacity, a low cost, and applicability in direct irradiation. Comprehensive knowledge of thermophysical and optical properties of solid particles is essential to ensure an effective harnessing of solar energy. The most important considerations when selecting solid particles include: thermophysical and optical properties, thermal resistance, crack resistance, satisfactory health and safety risks, availability, and low cost. It is also imperative to consider optical and thermophysical characteristics that might change from what they were “as received” after cyclic heating for a long period. Therefore, the knowledge of thermal performance of particulate materials becomes significant before using them as a heat-transfer medium. In this study, some particulate materials were chosen to study their feasibilities as heat-transfer and storage media for a particle-based central receiver tower system. These particulate materials included white sand, red sand, ilmenite, and Carbobead CP. The candidate particulate materials were heated at high temperatures for 6 h and then cooled to room temperature. After that, cyclic heating was performed on the particulate materials for 500 h at 1200 °C. The optical properties were represented by weighted solar absorptance, and the thermophysical properties of the particulates were measured “as received” and after cyclic heating (aging). EDX and XRD were conducted to quantify the chemical composition and interpret the changes in appearance associated with the particulate materials after cyclic heating. The results showed a considerable agglomeration in all particulates except for white sand in the 6 h heating test, and high agglomeration in the ilmenite. A slight decrease in the optical properties in the white sand and Carbobead CP was found after the aging test. The specific heat was decreased for red and white sand. The EDX and XRD results for white sand and Carbobead CP showed chemical stability, indicating high durability and reliability

An experimental investigation of chevron-shaped discrete structure configuration on the particle flow behavior of particle heating receivers

One of the main components of particle-based power tower (PBPT) systems is the particle heating receiver (PHR), through which solid particles are heated by concentrated sunlight. An obstructed-flow PHR (OF-PHR) developed by King Saud University is a type of PHR that has inverted V-shaped obstructions made of Inconel meshes, called chevrons, allowing for a longer time of sunlight exposure on the particles; hence, overcoming one of the limitations of free-fall PHRs. Two problems have been observed with this OF-PHR: (1) a considerable amount of the falling particles bounces forward and leaves the chevrons region; (2) it has a high packing density of chevrons that results in a very low falling particle velocity, which can lead to chevrons overheating. The present research attempts to resolve these issues and improve the PHR performance by understanding deeply the falling-particles behavior of OF-PHRs. The effects of (i) vertical spacing of chevrons and (ii) porosity of chevron meshes, (iii) PHR tilt angle, (iv) particle mass flow rate, and (v) type of particulate material were studied, at room temperature, concerning the following metrics: (1) particle velocity, (2) particle retention, and (3) particle curtain opacity. It was found that the particle velocity profile was nearly identical throughout the OF-PHR, which means that the obstructions successfully limited the particle falling speed. As for the PHR tilt angles, values below 10° were not sufficient to effectively retain the particles flowing through the chevron meshes since many particles bounced and left the PHR (low particle retention). Chevron's vertical spacing showed the most significant effect on particle opacity, with 30 mm spacing resulting in opacity values greater than 94 %. Two types of particulate material were tested, olivine sand and CARBOBEAD; the particle curtain opacity values using these materials were found to be comparable. By having high particle retention, sufficiently low particle falling speed, and high particle curtain opacity, the number of falling particles “controlled” by the obstructions (chevrons) is high; hence, a high number of particles has increased residence time, which will lead to higher PHR outlet temperatures. Moreover, high particle opacity ensures that most of the sunlight strikes the particles instead of the back side of the PHR and the obstructions (chevrons), ensuring optimal absorption of the solar energy and protecting the PHR construction from overheating/damage

Integrated CSP-PV hybrid solar power plant for two cities in Saudi Arabia

Solar energy has the potential to provide most of the electricity needed by mankind sustainably into the indefinite future. Concentrated Solar Power (CSP) has conventionally been considered more applicable than photovoltaic (PV) for baseload power since thermal storage is far cheaper than battery storage. However, the solar fields for CSP are relatively expensive. On the other hand, PV plants without storage deliver electric power at a much lower cost than CSP plants of comparable capacity without storage. Integrating both technologies is an attractive approach towards solar baseload power with affordable levelized cost of energy (LCOE). This study, which investigates the two cities of Saudi Arabia, consists of simulation and optimization in three main parts: The first part is a simulation of the CSP parabolic trough (CSP-PT) standalone plant and integrating the output parameters with an economic model to calculate the LCOE. The second part is the simulation of combined CSP-PT with PV, with a design strategy of utilizing all PV power for daytime use, and supplementing the PV output with thermal power as needed to maintain baseload operation in the daytime. The third part is the simulation of combined CSP-PT with a design strategy of providing all or nearly all daytime power with PV, with the utilization of excess energy from PV to supply heat to the thermal storage system. The results show that for a target capacity factor of 79%, the CSP plant alone requires a solar multiple of 6 in Riyadh and 3.5 in Tabuk. For both locations, the introduction of the hybrid concept substantially reduced the solar multiple. In Riyadh, the solar multiple ranged from 2.9 to 3 with the PV portion of the plant having a nameplate capacity equal to that of the CSP portion and 1.95 for a case with the PV nameplate capacity 60% greater than the CSP portion. For these same cases in Tabuk, the solar multiples were 1.78–1.85 and 1.6 simultaneously. Generally, hybridization is of greater benefit in Riyadh than in Tabuk owing to the greater fraction of solar resource in the form of diffuse sunlight which can be collected by the PV plant but not by the CSP plant. The LCOE was reduced by hybridization in both locations, but again the benefit was greater for Riyadh. Clearly, from a technological perspective, it is important to study the hybridization for an individual city based on its weather data as the incorporation of PV into CSP plant designs should be considered for all locations in order to reduce the cost to provide baseload power from solar energy, and the application of the hybridization concept can extend the applicability of CSP technology to regions with less direct sunlight than would be economically feasible with CSP alone

An Experimental Demonstration of the Effective Application of Thermal Energy Storage in a Particle-Based CSP System

Tests were performed at the particle-based CSP test facility at King Saud University to demonstrate a viable solution to overcome the limitations of using molten salt as a working medium in power plants. The KSU facility is composed of a heliostat field, particle heating receiver (PHR) at the top of a tower, thermal energy storage (TES) bin, a particle-to-working fluid heat exchanger (PWFHX), power cycle (microturbine), and a particle lift. During pre-commissioning, a substantial portion of the collected solar energy was lost during particle flow through the TES bin. The entrained air is shown to be the primary cause of such heat loss. The results show that the particle temperature at the PHR outlet can reach 720 °C after mitigating the entrained air issue. Additionally, during on-sun testing, a higher temperature of the air exiting the PWFHX than that of the air entering is observed, which indicates the effective solar contribution. Half-hour plant operation through stored energy was demonstrated after heliostat defocusing. Lastly, a sealable TES bin configuration for 1.3 MWe pre-commercial demonstration unit to be built in Saudi Arabia by Saudi Electric Company (SEC) is presented. This design modification has addressed the heat loss, pressure build-up, and contamination issues during TES charging

Vulnerability of Thermal Energy Storage Lining Material to Erosion Induced by Particulate Flow in Concentrated Solar Power Tower Systems

Researchers from all around the world have been paying close attention to particle-based power tower technologies. On the King Saud University campus in the Kingdom of Saudi Arabia, the first integrated gas turbine–solar particle heating hybrid system has been realized. In this study, two different types of experiments were carried out to examine how susceptible prospective liner materials for thermal energy storage tanks were to erosion. An accelerated direct-impact test with high particulate temperature was the first experiment. A low-velocity mass-flow test was the second experiment, and it closely mimicked the flow circumstances in a real thermal energy storage tank. The tests were conducted on bare insulating fire bricks (IFBs) and IFBs coated with Tuffcrete 47, Matrigun 25 ACX, and Tuffcrete 60 M. The latter three lining materials were high-temperature-resilient materials made by Allied Mineral Products Inc. (AMP) (Columbus, OH, USA). The results showed that although IFBs coated with AMP materials worked well in this test, the accelerated direct-impact test significantly reduced the bulk of the bare IFB. As a result, lining substances must be added to the surface of IFBs to increase their strength and protection because they cannot be used in situations where particles directly impact their surface. On the other hand, the findings of the 60 h cold-particle mass-flow test revealed that the IFBs were not significantly eroded. Additionally, it was discovered that the degree of erosion on the samples of bare IFB was unaffected by the height of the particle bed