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[en] For the Danish solar heating industries it is interesting to discuss the domestic market possibilities and the export possibilities for solar heating cooling systems. The Danish solar heating sector also wants to participate in the international collaboration within IEA Solar Heating and Cooling Task 25 'Solar Assisted Air Conditioning of Buildings'. The Danish Energy Agency therefore has granted means for this project to discuss: The price of cooling for 3 different solar cooling methods (absorption cooling, desiccant cooling and ejector cooling); Market possibilities in Denmark and abroad; The advantages by Danish participation in IEA Task 25. The task has been solved through literature studies to establish status for the 3 technologies. It turned out that ejector cooling by low temperatures (85 deg. C from the solar collector) exists as pilot plants in relation to district heating, but is still not commercial accessible. Desiccant cooling, where the supplied heat has temperatures down to 55 deg. C is a well-developed technology. However only a handful of pilot plants with solar heating exists, and thus optimization relating to operation strategy and economy is on the experimental stage. Absorption cooling plants driven by solar heating are found in a large number in Japan and are also demonstrated in several other countries. The combination of absorption heating pump and solar heating is considered to be commercial accessible. Solar heating is interesting as heat source of to the extent that it can replace other sources of heat without the economy being depreciated. This can be the case in South Europe if: 1) oil or natural gas is used for heating; 2) a solar heating system already exists, e.g. for domestic water supply, and is installed so that the marginal costs by solar heating supply of the ventilation plant is reduced. All in all the above conditions mean that the market for solar heating for cooling is very limited in Europe, where almost everybody are connected to the electric power network and where the effect tax, except in certain German areas, is low. Should a European market for solar cooling be developed a conscious policy is required, which rewards effect savings. Because of the non-existing domestic market and the diffuse European market possibilities active Danish participation in IEA Task 25 it is not recommended. (EHS)
[en] Alternative solar systems include a large number of heat-and mass exchange apparatus (HMTA) with considerable size surfaces. Prequired for realization of the work processes. This result in the increase in the overall dimentions. and cost of the system. The possibility of using the principle of combining the working and auxiliary processes within the (HMTA) has been considred, and the calculation proving the working ability of the alternative system for solving the task of air-condition, obtaining comfort parameters by employing evaporative air-cooling methods only, and a solar system with flat solar collectors to provide for the absorbent regeneration, have been performed. The study shows the importance in using Live Cycle Assessment, study for renewable energy, technologies, where environmental performance is especially important.(Author)
[en] The implementation of a variable structure fuzzy logic controller for a solar powered air conditioning system and its advantages are investigated in this paper. Two DC motors are used to drive the generator pump and the feed pump of the solar air-conditioner. Two different control schemes for the DC motors rotational speed adjustment are implemented and tested: the first one is a pure fuzzy controller, its output being the control signal for the DC motor driver. A 7 x 7 fuzzy matrix assigns the controller output with respect to the error value and the derivative of the error. The second scheme is a two-level controller. The lower level is a conventional PID controller, and the higher level is a fuzzy controller acting over the parameters of the low level controller. Step response of the two control loops are presented as experimental results. The contribution of this design is that in the control system, the fuzzy logic is implemented through software in a common, inexpensive, 16-bit microcontroller, which does not have special abilities for fuzzy control
[en] Solar driven rotary desiccant cooling systems have been widely recognized as alternatives to conventional vapor compression systems for their merits of energy-saving and being eco-friendly. In the previous paper, the basic performance features of desiccant wheel have been discussed. In this paper, a solar driven two-stage rotary desiccant cooling system and a vapor compression system are simulated to provide cooling for one floor in a commercial office building in two cities with different climates: Berlin and Shanghai. The model developed in the previous paper is adopted to predict the performance of the desiccant wheel. The objectives of this paper are to evaluate and compare the thermodynamic and economic performance of the two systems and to obtain useful data for practical application. Results show that the desiccant cooling system is able to meet the cooling demand and provide comfortable supply air in both of the two regions. The required regeneration temperatures are 55 deg. C in Berlin and 85 deg. C in Shanghai. As compared to the vapor compression system, the desiccant cooling system has better supply air quality and consumes less electricity. The results of the economic analysis demonstrate that the dynamic investment payback periods are 4.7 years in Berlin and 7.2 years in Shanghai.
[en] This article takes a look at solar cooling and air-conditioning, the use of which is becoming more and more popular. The article discusses how further research and development is necessary. The main challenge for professional experts is the optimal adaptation of building, building technology and solar-driven cooling systems to meet these new requirements. Various solar cooling technologies are looked at, including the use of surplus heat for the generation of cold for cooling systems. Small-scale solar cooling systems now being tested in trials are described. Various developments in Europe are discussed, as are the future chances for solar cooling in the market
[en] This first article of two on solar air-conditioning takes a look at how interest in solar-driven cooling systems is growing, especially in the Mediterranean area. The author comments that scientists are warning that, in spite of the fact that first all-in offers for solar cooling systems are on the market, much research and development still has to be done in this area. Contributions presented by various lecturers at a seminar on solar air-conditioning in Freiburg, Germany, are summarised. The dangers involved in using components that are badly suited to each other are noted. A check list method presented at the seminar is briefly mentioned and it is stressed that all costs, including regular maintenance fees, should be included in calculations and when making comparisons
[en] Highlights: • Modular silica gel–water adsorption chiller was designed and tested. • Single/double effect LiBr–water absorption chiller was operated and tested. • 1.n effect LiBr–water absorption chiller was proposed, designed and tested. • CaCl_2/AC–ammonia adsorption refrigerator was introduced and tested. • NH_3–H_2O absorption ice maker with better internal heat recovery was introduced. - Abstract: Solar driven air conditioning systems can cope with solar collectors working in a wide range of temperatures. Sorption systems, including absorption and adsorption refrigeration systems, are among the best choices for solar cooling. Five systems including modular silica gel–water adsorption chiller, single/double effect LiBr–water absorption chiller, 1.n effect LiBr–water absorption chiller, CaCl_2/AC (activated carbon)–ammonia adsorption refrigerator, and the water–ammonia absorption ice maker with better internal heat recovery were presented. The above five sorption chillers/refrigerators work under various driven temperatures and fulfill different refrigeration demands. The thermodynamic design and system development of the systems were shown. All these systems have improvements in comparison with existing systems and may offer good options for high efficient solar cooling in the near future.
[en] Highlights: • The performance of a solar hybrid air conditioner integrated with HDH desalination system is numerically investigated. • For increase the regeneration air from 70 to 130 m3/h, the distillate water productivity increases from 2.988 to 4.78 L/h. • For increase the regeneration air from 70 to 130 m3/h, COPoverall daily decreases from 4.66 to 3.386. • For increases the regeneration air temperature from 75 to 95 °C, the distillate water increases from 3.1752 to 5.011 L/h. • For increases the regeneration air temperature from 75 to 95 °C, COPoverall daily decreases from 4.392 to 3.636. - Abstract: In this study, the performances of a solar energy assisted hybrid desiccant air conditioning system integrated with humidification–dehumidification (HDH) desalination system are numerically investigated. The aim of this study is to benefit from the temperature rise of the regeneration air outside of the desiccant conditioning system as well as the water vapor content in this regeneration air by feeding it to the humidification-dehumidification water desalination unit to produce distillate water. The distillate water productivity, human thermal comfort issues, and energy saving represent the main objective of the present numerical study. The simulated results developed for subsystems are validated with the published experimental results. The effects of regeneration air temperature and flow rate on supply cooled air temperature, distillate water productivity, the cooling coefficient of performance and overall daily coefficient of performance of the proposed system are investigated. The results show that (i) the distillate water productivity increases from 3.175 to 5.011 L/h and overall daily coefficient of performance decreases from 4.392 to 3.636 with increasing the regeneration air temperature from 75 to 95 as (ii) the increase in the regeneration air flow rate from 70 to 130 m3/h, increases the distillate water productivity from 2.988 to 4.78 L/h and decrease the overall daily coefficient of performance from 4.66 to 3.386. The study demonstrates that the proposed system represents the best options in hot and humid regions.
[en] This article takes a look at the increasing range of products on offer in the solar cooling area. Such an increase applies in particular to products in the low and medium power ranges under 30 kilowatts. Several hindrances to the expansion of the solar air-conditioning (SAC) market are named, both in the technological as well as in the operational area. The author states that a considerable amount of optimisation work is still to be done. Market offerings using absorption and adsorption techniques are examined, as are silica gel-based systems. Companies in the German-speaking parts of Europe active in the area are listed and their work is reviewed. The opinions of various experts that were presented at a congress on the subject are noted. Planning tools made available by the International Energy Agency's Task 38 'Solar air-conditioning and refrigeration' are mentioned.
[en] Highlights: ► In this study, a hybrid desiccant assisted air conditioner powered by a hybrid solar collector is proposed. ► A hybrid air conditioning system is modeled using TRNSYS simulation program. ► We find that the system is better than a standalone vapor compression cycle in ensuring thermal comfort. ► We also find that the new approach’s COP is about double that of the common solar air conditioners. - Abstract: Liquefied Natural Gas (LNG) and chemical processing are energy-intensive facilities, such that any enhancement of their efficiency will result in abundant reduction of energy consumption and green house gas emissions. To enhance LNG plant energy efficiency, the potential of various options for improving liquefaction cycle efficiency is investigated in this study. After developing models for the LNG process using ASPEN software, four expansion loss recovery options are simulated. The simulation results show that the compressor power reduction, expansion work recovery, and LNG production increase can be achieved as much as 2.68 MW, 3.82 MW, and 1.24%, respectively, by replacing conventional expansion processes with expanders. By implementing all of the enhancements, the power consumption per unit mass of LNG could be reduced by 7.07% and 3.68%, with and without considering deduction of the recovered power from the total required power, respectively. Therefore, the expansion work recovery is an important option to be implemented in LNG plants.