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(a) A plot of friction factor against Reynolds number (b) A plot of the non-dimensional heat transfer against Reynolds number
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This paper aims at developing a novel air-cooled condenser for concentrated solar power plants. The condenser offers two significant advantages over the existing state of the art. Firstly, it can be installed in a modular format where pre-assembled condenser modules reduce installation costs. Secondly, instead of using large, fixed speed fans, smal...
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An updraft tower cooling system is assessed for elimination of water use associated with power plant heat rejection. Heat rejected from the power plant condenser is used to warm the air at the base of an updraft tower; buoyancy-driven air flows through a recuperative turbine inside the tower. The secondary loop, which couples the power plant conden...
Citations
... This restricts the amount of cooling or spray water available for usage in cooling towers in CSP plants. As such, aircooled condenser (ACC) units are ubiquitous as cooling systems in CSP power blocks [2,3], for the attractive reason of rejecting heat without consuming spray water. This is opposed to a water-intensive deluge or evaporative cooling process in a wet-cooling tower [4]. ...
... This allows 1 and 2 to be determined, as well as the spray water consumption 2 in Eq. (5). During 2 The slightly negative air pressure due to induction is expected to influence the evaporation rate. We do not consider this effect. ...
... Condensers that employ ambient air as a cooling medium are termed air-cooled condensers (ACCs). Moore et al. (2014) claim that the use of ACCs can potentially reduce the water usage of a power plant by as much as 90 %. This reduction is especially significant for CSP plants. ...
... This reduction is especially significant for CSP plants. Moore et al. (2014) believe that ACCs are in many situations the only feasible option for CSP application. ...
This study aims to enhance the performance of an induced draught air-cooled condenser (ACC) by increasing the ACC's air mass flow rate and heat rejection rate. These improvements are achieved through pressure recovery, which is the conversion of the dynamic pressure at the fan outlets into static pressure. Pressure recovery increases the effective static pressure rise of the axial flow fans in the ACC, resulting in a higher operating airflow rate. Consequently, higher heat removal rates are possible.
Stator blade rows and diffusers are capable of pressure recovery. Combinations hereof are tested for the axial flow fan featured in the ACC (i.e. the M-fan) through numerical simulation in OpenFOAM. Diffuser lengths of l_dif = d_F, 0.4d_F and 0.2d_F are considered, where d_F = 7.315 m is the fan diameter. The most promising discharge configurations are selected for a five-by-four induced draught ACC. The ACC is then analysed with and without these appendages under windless and windy conditions. Wind directed along the shorter and longer axes of the ACC is considered at wind speeds of 3, 6 and 9 m/s.
Amongst the diffusers of length l_dif = d_F, an annular diffuser with both walls diverging at 22° from the axial direction recovers the most pressure for the M-fan over a range of flow rates. For the l_dif = 0.4d_F length, a conical diffuser with an included angle of 2θ = 32° recovers the most pressure. And a conical diffuser with 2θ = 40° yields the highest pressure recoveries for the l_dif = 0.2d_F length. However, the l_dif = d_F annular diffuser is deemed impractical for ACC application due to its length and wide wall angles.
Under windless conditions, both conical diffusers increase the mass flow rate through the five-by-four ACC by ~2.5 %. As a result, the heat transfer rate improves by 2.0 %. The power consumption of the ACC fans also drops by 5.2--5.5 %, increasing the heat-to-power ratio by 12.4--13.1 W/W. In a light breeze of 3 m/s, the increase in mass flow rate due to the diffusers is 1.7--2.0 %; in a moderate breeze of 6 m/s, the increase is 0.9--1.3 %; and in a fresh breeze of 9 m/s, it is 1.0--1.6 %.
There is more variation in the thermal performance results of the ACCs featuring the two different diffusers: The shorter diffuser does not improve the heat transfer rate of the ACC as much as the longer diffuser does under windy conditions. At 6 m/s, the ACC with longer diffusers rejects 1.6--2.2 % more heat than the ACC with shorter diffusers. At 9 m/s, the former rejects ~2.5 % more heat than the latter.
This research demonstrates that discharge diffusers can enhance the performance of an induced draught ACC. The diffusers' pressure recovery increases the mass flow rate through the ACC, aiding its heat rejection capability. From a performance perspective, the l_dif = 0.4d_F diffuser is recommended. However, practical considerations might render the shorter l_dif = 0.2d_F diffuser more suitable.
... As presented by many research works [45,46], and confirmed by industrial partners, for smaller devices such as examined in this work, other expressions based on material cost and other additional costs could be suitable. The investment cost in this study can be expressed as: ...
A comparative study is made between various optimized configurations of finned tube heat exchanger used to transfer thermal energy from a solar parabolic trough collector to a bench-scale dryer. The exchanger design relies on the logarithmic mean temperature difference (LMTD) and conjugate directions optimization method already integrated into the Engineering Equation Solver software (EES). Total cost minimization was set as the objective function. The model is first tested with previous literature results before being used to compare optimum configurations of four distinct heat exchanger configurations. The effect of five geometric and operating parameters is investigated. Results show that the third heat exchanger configuration (HX 3) yields the lowest costs. Therminol-LT and-VP1, as well as Dowtherm-Q and-A, were found as the best working fluids for this application. Using copper as both tubes and fins material results in the smallest heat transfer surface area because of its high thermal conductivity. When economics are considered, aluminum and stainless steel alloys become suitable alternatives for fins and tubes, respectively. This yields savings of more than 40% on total costs from an all-copper construction.
... Mechanical draught air-cooled condensers (ACCs) employ air as the cooling medium. Moore et al. [2] estimate that ACCs can potentially reduce the water consumption of a power plant by as much as 90 %. Therefore, ACCs are often the only feasible option for CSP applications. ...
... FC , dif and dif are generally unknown, Kröger [9] argued that it is useful to obtain the performance characteristics of the fan-diffuser unit. Four terms in equation (2) can then be replaced by ...
This study investigates the potential gain in operating volume flow rate and static efficiency for an induced draught fan arrangement by reducing the outlet kinetic energy loss. The reduction is achieved through pressure recovery, which is the conversion of dynamic pressure into static pressure. Downstream diffusers, stator blade rows, or a combination of these can recover pressure. Six difference discharge configurations are tested for a fan. An annular diffuser with equiangular walls at an angle of 22° from the axial direction and a length equal to the fan diameter recovers the most pressure over a range of volume flow rates.
... The previous research literature [8] reveals that there exists the potential in desert areas under typical environment conditions to store cold energy in the winter, but to date, it has not been verified either experiments or simulations that include a storage system to fulfill the cooling requirements for a solar thermal power plant located in a desert area. Mostly, a condenser is cooled by using high power electrical fans at solar thermal power plant [9]. This dry cooling of condensers at power plants not only affects the thermal efficiency of the power plant but also increases the unit price of electricity, especially in the peak summer season when high power is required. ...
This paper aims to explore an efficient, cost-effective, and water-saving seasonal cold energy storage technique based on borehole heat exchangers to cool the condenser water in a 10 MW solar thermal power plant. The proposed seasonal cooling mechanism is designed for the areas under typical weather conditions to utilize the low ambient temperature during the winter season and to store cold energy. The main objective of this paper is to utilize the storage unit in the peak summer months to cool the condenser water and to replace the dry cooling system. Using the simulation platform transient system simulation program (TRNSYS), the borehole thermal energy storage (BTES) system model has been developed and the dynamic capacity of the system in the charging and discharging mode of cold energy for one-year operation is studied. The typical meteorological year (TMY) data of Dunhuang, Gansu province, in north-western China, is utilized to determine the lowest ambient temperature and operation time of the system to store cold energy. The proposed seasonal cooling system is capable of enhancing the efficiency of a solar thermal power plant up to 1.54% and 2.74% in comparison with the water-cooled condenser system and air-cooled condenser system respectively. The techno-economic assessment of the proposed technique also supports its integration with the condenser unit in the solar thermal power plant. This technique has also a great potential to save the water in desert areas.
... Moreover, it has high water consumption which is not a suitable solution in hot areas [7]. Different approaches to reduce water consumption in wet cooling towers are suggested, which one of the most commonly used solutions is the conversion of wet cooling tower to dry or hybrid cooling systems [8][9][10][11][12]. Various articles have addressed these strategies, including Rezaei and Shafiei [8], which analyzed the combined dry/wet cooling system. ...
... The difference between this system and the reference [8] in this section is that at first, the whole cooling water flows into the dry cooling system, then the cooling water enters the wet cooling tower which results in a further reduction in water consumption. Moore et al. [10] developed a method for designing an A.C.C system for a small solar power station, which could maintain the power generation capacity for the most times during normal operation. One of this system's features is bank of circular finned tubes usage for fan speed control. ...
The consequences of water crisis in terms of political, social and environmental impacts have been motivated in this paper to recognize the hybrid wet /dry cooling systems of power plant in Iran. The existence of temperature constraints for consumers connected to the hybrid cooling tower, Space constraints for the construction of auxiliary system, devoting attention to high Net Present Value (NPV) of the project over the course of 25 years, Returning the appropriate capital, Optimal Design of air cooler and it's desirable performance over the course of a year were the reasons led to use of the genetic algorithm (GA) in this paper. The GA should optimize the design of the air cooler, according to that, at one functional point of a year, the lowest investment costs and the lowest cost of utilization in one year will happen. The cost of utilization in this project including: water consumption (makeup water of the cycle), fan power consumption (wet and dry block of hybrid cooling system), as well as chemical additives to water. The results illustrated that the proposed algorithm usage, applying a proper control system, taking into account the standards in the written code and determining the optimization intervals according to the manufacturer's data could conclude to the design of an air cooler, which can be constructed by inquiring from the manufacturing companies. The results also indicated that optimized design of hybrid cooling tower could reduce water consumption about 63% over the course of one year, return on investment by 5 years, develop NPV up to 40 M€ and enhance steam turbine power.
... The consideration of ACCs is of topical interest, as many plants that are currently under development or in the tender phase will be placed in desert areas. Having no direct access to cooling water mandates the use of ACC in which the condensation of steam is achieved solely by air cooling and parasitic electrical power consumption (Moore et al., 2013). The ACC model was previously validated by Guedez et al. (2017). ...
Concentrating solar power plants are taking an increasing share in the renewable energy generation market. Parabolic trough is one of such technologies and the most commercially mature. However, this technology still suffers from technical challenges that need to be addressed. As these power plants experience daily start-up procedures, the optimal performance in transient operation needs to be considered. This paper presents a performance based modelling tool for a gas-boosted parabolic trough power plant. The objective of the paper is to define an optimal operational strategy of the power plant start-up procedure with the aim of minimizing its fuel consumption while at the same time maximizing its electric energy output, taking into account all the thermo-mechanical constraints involved in the procedure. Heating rate constraints of the steam generator and the booster heater, and the steam turbine start-up schedule were considered. The simulation model was developed based on a power plant located near Abu Dhabi, and was validated against real operational data with a maximum integral relative deviation of 4.3% for gross electric energy production. A multi-objective optimization was performed for a typical operating week during winter and spring weather conditions. The results suggest that in order to minimize the fuel consumption and at the same time maximize the electric energy production, an evaporator heating rate of 6 K/min is an optimal value both for winter and spring conditions.
... The use of earth as a cooler results in removal of the condenser fan and contributes to the protection of the environment. Moore et al. (2013) developed a new, air-cooled condensing unit for solar power plants. It offers two significant advantages over the state of the art. ...
The article deals with analysis of defects of condensing units for refrigerators with R134a, R404A refrigerant, which caused frequent complaints to the company. Up to 30% of the claims related to a valve of the condensing unit. Various quality management tools and risk assessment methods were used to solve the problem. The Pareto analysis and Lorenz curve were used to determine the significant minor causes that need to be addressed to resolve the majority of problems. Based on the Fault Tree Analysis (FTA), a change in the technological process was made for assembly and installation procedure of the valve to the base plate and in hard brazing of the tube and the valve, thus reducing the number of defects in the condensing unit by 40%. Valve defects have been reduced by nearly 50%.
... The consideration of ACCs is of topical interest, as many plants that are currently under development or in the tender phase will be placed in desert areas. Having no direct access to cooling water mandates the use of ACC in which the condensation of steam is achieved solely by air cooling and parasitic electrical power consumption (Moore et al., 2013). The ACC model was previously validated by Guedez et al. (2017). ...
Concentrating solar power plants, even though they can be integrated with thermal energy storage, are still subjected to cyclic start-up and shut-downs. As a consequence, in order to maximize their profitability and performance, the flexibility with respect to transient operations is essential. In this regard, two of the key components identified are the steam generation system and steam turbine. In general it is desirable to have fast ramp-up rates during the start-up of a power plant. However ramp-up rates are limited by, among other things, thermal stresses, which if high enough can compromise the life of the components. Moreover, from an operability perspective it might not be optimal to have designs for the highest heating rates, as there may be other components limiting the power plant start-up. Therefore, it is important to look at the interaction between the steam turbine and steam generator to determine the optimal ramp rates. This paper presents a methodology to account for thermal stresses limitations during the power plant start up, aiming at identifying which components limit the ramp rates. A detailed dynamic model of a parabolic trough power plant was developed and integrated with a control strategy to account for the start-up limitations of both the turbine and steam generator. The models have been introduced in an existing techno-economic tool developed by the authors (DYESOPT). The results indicated that for each application, an optimal heating rates range can be identified. For the specific case presented in the paper, an optimal range of 7-10 K/min of evaporator heating rate can result in a 1.7-2.1% increase in electricity production compared to a slower component (4 K/min).
... Thermal systems comprising ambient atmospheric air based cooling units (such as dry air cooled condensers used in chillers and power generation plants) have gained much importance over the years especially in dry arid areas. For instance, air-cooled condensers may be the only feasible option for concentrated solar power (CSP) plants which are typically installed in dry areas [1]. Furthermore, the basic media for active photovoltaic (PV) cooling is either the ambient air or water [2]. ...
In this paper, a new design of atmospheric air passive cooling system which consists of an earth-air pipe heat exchanger is proposed. The objective of this system is to cool the warm ambient air for thermal applications in hot arid areas. A 1.5 m long copper pipe with 1.5 cm inner diameter was buried under the soil contained in a galvanized steel drum. The blower and air heater were used at pipe inlet to induce warm air inside the pipe which gets cooled in earth-air pipe heat exchanger. The experiments were performed under the controlled conditions of operating parameters such as induced air temperature, flow rate and soil bulk temperature. The performance of considered heat exchanger was studied for three different soil compaction levels with distinct values of relative density, void ratio and porosity. The results showed that induced air temperature was dropped in the range between 8 and 24 °C across the earth-air pipe heat exchanger and the system effectiveness varied between 0.3 and 0.7 depending on the operating conditions and soil compaction.
