3E (Energy-Exergy-Economic) comparative study of integrating wet and dry cooling systems in solar tower power plants (original) (raw)
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Potential assessment of using dry cooling mode in two different solar thermal power plants
International journal of energetica, 2017
Most of Concentrating Solar Power (CSP) plants are usually installed in desert regions where water resource availability is a critical limitation due to the lack of water required for the exploitation of these systems in these regions. Therefore, the aim of this study is to investigate the techno-economic competitiveness of deploying both modes of cooling (wet and dry) in two different parabolic trough solar thermal power plants integrated with thermal energy storage and fuel backup system; the first one is using thermic oil, while the other is working using molten salt. The obtained results show that the dry cooling mode can decrease the yields of the two power plants down to 8.7 % and 9.3 % for oil and salt configurations respectively. On the other hand, the levelized cost of electricity can increase by using this cooling option up to 9.3 % for oil plant, and 10.0 % for salt one. However, the main advantage of using dry cooling option is reducing water consumption which has been decreased by more than 94 % for both plants. The application of our methodology to other two sites worldwide, confirms the viability of the obtained results. The importance of this result is to show the effect of working fluids on the cooling system of solar power plants.
Energy and Economic Performance of Solar Cooling Systems World Wide
Energy Procedia, 2014
Solar thermal cooling systems have been installed as pilot projects in most regions of the world, but due to the low number of total installations there is not yet much experience available about system sizing and design. To counter the lack of experience and to evaluate the potential of energy efficient solar cooling systems, a systematic system design study has been carried out covering most climatic regions worldwide. For each technology investigated, an energy optimized control strategy was developed which maximizes the primary energy efficiency. This control strategy was implemented in the simulation environment INSEL and system models were developed for a range of thermal cooling technologies and validated with operating experiences from different plants monitored by the authors. It could be shown that a reduction of nominal chiller power by 30% to 40% or more hardly effects the solar cooling fraction for most climates, but significantly increases the machine operating hours and thus improves the economics. The lower the nominal power of the chiller, the higher the recommended ratio of collector surface area per kW. For a given machine nominal power, solar cooling fractions increase with collector surface area until saturation is reached. Collector surface areas can be as high as 5 m² to 10 m 2 per kW with still increasing solar cooling fractions, but acceptable specific collector yield reduction. The economic optimum is reached for less solar cooling fraction and thus lower primary energy savings. Single effect absorption cooling systems easily reach 80% solar cooling fraction for all but very humid climates. Primary energy ratios can be over 3.0, depending on system design and cooling load data. CO 2 and primary energy savings of 30-79% are achievable. The economic study showed that solar thermal cooling is more viable in hot climates than in moderate European climates. Annual costs strongly depend on the locations. The specific costs per kWh cooling in German locations vary between 0.25 and 1.01 €/kWh, in Spanish locations between 0.13 and 0.30 €/kWh. In hot climates like Jakarta and Riyadh the specific costs are as low as 0.09 to 0.15 €/kWh. Furthermore the maximum investment costs were calculated get a payback time of 10 years.
This work describes and analyses the Rankine cycle of the 50 MW parabolic trough power plant Andasol 1 in the Spanish region of Andalusia, a prime example of the use of solar energy for electricity generation. By means of an exergoeconomic analysis, all components of the thermal plant are considered individually. Thermodynamic inefficiencies within the system are located, quantified and economically evaluated. Generally, various wet and dry cooling methods come into consideration for the re-cooling of the steam. Andasol 1 uses the more effective wet cooling method, because in the vicinity sufficient water reserves are available. In this work, the water-cooled system is replaced by an air-cooled condenser and the two variants are compared under exergoeconomics aspects. Also the impact of a construction of Andasol 1 in a hotter and drier climate than the northern Sahara is simulated. The analysis shows that within the air-cooled condenser much more exergy is destroyed than within the ...
Past, present, future of solar cooling: Technical and economical considerations
Solar Energy, 2018
A large fraction of cooling demand depends on solar radiation intensity, therefore a strong attention was directed toward solar cooling immediately after the 1973 energy crisis. Whereas pilot solar cooling plants were built up and experimented, this technology never really took off. A recent survey reported something more than 1000 plants operating, a very modest number with respect the great potential of solar cooling. A review of technologies as they developed in the past, operate in the present with a forecasting for the future is here proposed to follow how the technology evolved during almost half a century regarding the solar section and the relative refrigeration equipment. The analysis allows to take stock of the situation selecting solar sections, cooling machines and their coupling which seem nowadays more suitable for wide application in the near future. A study is proposed at the end to put together some energy evaluations in different climates and much more difficult economical evaluations to investigate whether a possible fossil fuel parity cost can be attained, if not today, in a near future. • the cost of the solar section in cooling plants is rapidly reducing to
Sustainability
The use of wet cooling in Concentrated Solar Power (CSP) plants tends to be an unfavourable option in regions where water is scarce due to the high water requirements of the method. Dry-cooling systems allow a water consumption reduction of up to 80% but at the expense of lower electricity production. A hybrid cooling system (the combination of dry and wet cooling) offers the advantages of each process in terms of lower water consumption and higher electricity production. A model of a CSP plant which integrates a hybrid cooling system has been implemented in Thermoflex software. The water consumption and the net power generation have been evaluated for different configurations of the hybrid cooling system: series, parallel, series-parallel and parallel-series. It was found that the most favourable configuration in terms of water saving was series-parallel, in which a water reduction of up to 50% is possible compared to the only-wet cooling option, whereas an increase of 2.5% in the ...
Performance and Operational Experiences of Solar Driven Cooling Plant after Five Years in Operation
01-902-664-9706, 2010
The main aim of this study is to report the performance evaluation as well as the gained operational experiences of a solar-driven cooling plant after 5 years in operation, in addition, based on the gained experiences, a suggestion for an appropriate small-scale solar-driven cooling plant for hot arid areas is presented. The plant includes a 35.17 KW cooling (10-RT) absorption chiller, vacuum tubes collectors with gross and net areas of 108 m 2 and 72 m 2 , a hot water storage capacity of 6.8 m 3 , a cold water storage capacity of 1.5 m 3 and a 134 kW cooling tower. The plant provides airconditioning for a floor space of 270 m 2. The plant performance results indicate: instead small solar energy values at the plant location, the daily solar fraction ranged from 0.33 to 0.41, and for the duration from August 2002 to November 2007 the total solar energy supplied to the chiller is 53914 kWh and the total external energy (gas energy) supplied to the chiller is 35249 kWh and their percentage are about 60% and 40%, respectively. The collectors' filed instantaneous mean efficiency value is about 0.63, the monthly average value varies from 34.1 % up to 41.8 %, with a five-year average value of 28.3 %, respectively and the daily chiller COP varies from 0.37 to 0.81, respectively. The gained from the operational experiences are: in hot arid areas, the water normally is rare, thus the re-cooling system should be designed based on dry re-cooling techniques. Moreover, based on the total initial capital cost of the entire solar cooling system, adsorption-cooling technology for small-scale solar-driven airconditioning systems is the most appropriate. This is because these chillers can be driven by a low temperature energy source that can be obtained from flat plate collectors where, costs are a bit lower for flat plate collectors with liquid heat transfer carrier.
Studying the Reduction of Water Use in Integrated Solar Combined-Cycle Plants
With vast amounts of water consumed for electricity generation and water scarcity predicted to rise in the near future, the necessity to evaluate water consumption in power plants arises. Cooling systems are the main source of water consumption in thermoelectric power plants, since water is a cooling fluid with relatively low cost and high efficiency. This study evaluates the performance of two types of power plants: a natural gas combined-cycle and an integrated solar combined-cycle. Special focus is made on the cooling system used in the plants and its characteristics, such as water consumption, related costs, and fuel requirements. Wet, dry, and hybrid cooling systems are studied for each of the power plants. While water is used as the cooling fluid to condense the steam in wet cooling, dry cooling uses air circulated by a fan. Hybrid cooling presents an alternative that combines both methods. We find that hybrid cooling has the highest investment costs as it bears the sum of the costs of both wet and dry cooling systems. However, this system produces considerable fuel savings when compared to dry cooling, and a 50% reduction in water consumption when compared to wet cooling. As expected, the wet cooling system has the highest exergetic efficiency, of 1 and 5 percentage points above that of dry cooling in the conventional combined-cycle and integrated solar combined-cycle, respectively, thus representing the lowest investment cost and highest water consumption among the three alternatives. Hybrid and dry cooling systems may be considered viable alternatives under increasing water costs, requiring better enforcement of the measures for sustainable water consumption in the energy sector. Sustainability 2019, 11, 2085 2 of 27
Solar cooling technologies. Design, application and performance of existing projects
Solar Energy, 2017
The present paper introduces the concept of solar cooling as a major issue in the valorization of the solar source in front of the challenge represented by the worldwide growing demand of cold. The most relevant solar cooling technologies are briefly discussed as well as their possible combination and implementation in different contexts. Some real-world installations are proposed as representative of possible plant design in a variety of climate and building integration conditions. Through these cases, trends of innovation are identified both for small and settlement scale applications, supporting the perspective of a more efficient exploitation of the solar cooling potential.
Model performance assessment and experimental analysis of a solar assisted cooling system
Solar Energy, 2017
Due to the economic development and occupancy requests, building thermal comfort reached higher levels during the last years. Energy consumption rates have become excessive and engendered an increasing reliance on fossil-fuel reserves. Hence, the conception of energy-efficient buildings as well as applying solar cooling techniques has become a promising solution. In this context, the current work dealt with the appraisal of a solar system that drives the cooling process in an office building located in the Center of Researches and Energy Technologies in Tunisia. The solar system consisting of linear parabolic trough solar collectors' field coupled to a 16 kW double effect Lithium Bromide absorption chiller, supplies chilled water to a set of fan coils installed in the 126 m 2 laboratory building. A dynamic model that couples the solar cooling system with the building was developed using the TRNSYS tool and several simulations were performed to assess the case study and improve its performance. The model results were compared to the data collected during the experimental campaign conducted in summer 2015 and showed that the collectors efficiency was at the range of 26-35%, the COP ranged between 0.65 and 1.29, the daily maximum solar COP was approximately at 35%. However, the solar system was unable to cover 32.3% of the cooling requirements, the absorption chiller was switched on only during 53.8% of its total operating time. An improved system configuration was then studied; the integration of an auxiliary heater prior to the chiller as well as the increase of the aperture area guaranteed high driving temperatures and more suitable conditions to the absorption chiller. As a result, the chiller operating time increased to 75.8%, the cooling power increased by 75.6%, the solar COP reaches 57% and the solar fraction averaged 87%. The summer season performances predict that the improved system configuration achieves primary energy savings that reach 82.3% compared to a classic air conditioning system producing the same cooling power, the yearly avoided CO 2 emissions are estimated to 2947 kg.
Solar Cooling Technologies for Southern Climates -A System Comparison –
In the present paper different solar thermal cooling systems are compared to a PV driven and a net connected compression chiller in hot and dry southern climate. The cooling systems are considered to be applied to a planned innovative office building in Cairo, Egypt. A single effect absorption chiller with vacuum tube collectors is analysed as well as a double and a triple effect absorption chiller with higher concentrating Fresnel collectors. For the PV driven compression chiller system high efficient mono crystalline PV modules are considered together with a highly efficient compression chiller system with integrated direct dry het rejection. Dynamic system simulations with INSEL are used to analyse the performance of the different cooling systems. To compare the overall performance of the analysed solar cooling systems, the primary energy consumption required to cover the whole cooling load of the building and the resulting primary energy ratio are calculated for each system.