首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 62 毫秒
1.
2.
In this study, performance assessment of an integrated cooling plant having both free cooling system and solar powered single-effect lithium bromide–water absorption chiller in operation since August 2002 in Oberhausen, Germany, was performed. A floor space of 270 m2 is air-conditioned by the plant. The plant includes 35.17 kW cooling (10-RT) absorption chiller, vacuum tube collectors’ aperture area of 108 m2, hot water storage capacity of 6.8 m3, cold water storage capacity of 1.5 m3 and a 134 kW cooling tower. The results show that free cooling in some cooling months can be up to 70% while it is about 25% during the 5 years period of the plant operation. For sunny clear sky days with equal incident solar radiation, the daily solar heat fraction ranged from 0.33 to 0.41, collectors’ field efficiency ranged from 0.352 to 0.492 and chiller COP varies from 0.37 to 0.81, respectively. The monthly average value of solar heat fraction varies from 31.1% up to 100% and the five years average value of about 60%. The monthly average collectors’ field efficiency value varies from 34.1% up 41.8% and the five-year average value amounts about 28.3%. Based on the obtained results, the specific collector area is 4.23 (m2/kWcold) and the solar energy system support of the institute heating system for the duration from August 2002 to November 2007 is 8124 kWh.  相似文献   

3.
Institutional buildings contain different types of functional spaces which require different types of heating, ventilating and air conditioning (HVAC) systems. In addition, institutional buildings should be designed to maintain an optimal indoor comfort condition with minimal energy consumption and minimal negative environmental impact. Recently there has been a significant interest in implementing desiccant cooling technologies within institutional buildings. Solar desiccant cooling systems are reliable in performance, environmentally friendly and capable of improving indoor air quality at a lower cost. In this study, a solar desiccant cooling system for an institutional building in subtropical Queensland (Australia) is assessed using TRNSYS 16 software. This system has been designed and installed at the Rockhampton campus of Central Queensland University. The system's technical performance, economic analysis, energy savings, and avoided gas emission are quantified in reference to a conventional HVAC system under the influence of Rockhampton's typical meteorological year. The technical and economic parameters that are used to assess the system's viability are: coefficient of performance (COP), solar fraction, life cycle analysis, payback period, present worth factor and the avoided gas emission. Results showed that, the installed cooling system at Central Queensland University which consists of 10 m2 of solar collectors and a 0.400 m3 of hot water storage tank, achieved a 0.7 COP and 22% of solar fraction during the cooling season. These values can be boosted to 1.2 COP and 69% respectively if 20 m2 of evacuated tube collector's area and 1.5 m3 of solar hot water storage volume are installed.  相似文献   

4.
This paper describes a new small air-cooled double-effect LiBr–H2O absorption prototype directly powered by fuel and discusses the experimental findings for some tests carried out in Madrid in 2007, with natural gas as energy source. The prototype, which has been designed to supply 7 kW of cooling power, was able to chill water up to 7–18 °C under extreme outdoor temperatures. A new flat-sheet adiabatic absorber was used allowing it to operate at outdoor temperatures about 45 °C without any sign of crystallization. A mean daily coefficient of performance (COP) of about 1.05 was obtained. Since this absorption machine does not need cooling tower, there is neither water consumption nor Legionella pollution. Moreover, it is a quite compact unit. The ratio of cooling power over volume is about 6.0 kW/m3, while for the only air-cooled absorption chiller, Rotartica 045v, in the marked until 2009 this ratio is 4 kW/m3. When comparing with electric chillers presently on the market, this prototype was found to have a cooling cost approximately 15.9% higher and an environmental impact 16.7% lower. The absorption prototype is a more environmentally friendly solution as it does not emit fluorinated refrigerants.  相似文献   

5.
《Applied Energy》2007,84(6):608-622
A method is proposed for estimating the electricity consumption (and associated carbon emissions) of a defined electrical-lighting configuration in an office building, accounting for the daylight contribution from windows and rooflights. Heat gains due to lighting for an average day in each month may be used to aid assessments of the effect of lighting systems on the cooling load, known to be high for office environments. For a typical 6-storey office building, annual energy savings for lighting of 56–62% and a reduction in CO2 emissions of nearly 3 tonnes are predicted by changing the lighting and daylighting specifications for a defined “2005” scenario to those of a low-carbon “2030” scenario. The associated reduction in peak lighting-load, and hence heat gain due to lighting, is 3 W/m2.  相似文献   

6.
Low depth geothermal heat exchangers can be efficiently used as a heat sink for building energy produced during summer. If annual average ambient temperatures are low enough, direct cooling of a building is possible. Alternatively the heat exchangers can replace cooling towers in combination with active cooling systems. In the current work, the performance of vertical and horizontal geothermal heat exchangers implemented in two office building climatisation projects is evaluated.A main result of the performance analysis is that the ground coupled heat exchangers have good coefficients of performance ranging from 13 to 20 as average annual ratios of cold produced to electricity used. Best performance is reached, if the ground cooling system is used to cool down high temperature ambient air. The maximum heat dissipation per meter of ground heat exchanger measured was lower than planned and varied between 8 W m?1 for the low depth horizontal heat exchangers up to 25 W m?1 for the vertical heat exchangers.The experimental results were used to validate a numerical simulation model, which was then used to study the influence of soil parameters and inlet temperatures to the ground heat exchangers. The power dissipation varies by ±30% depending on the soil conductivity. The heat conductivity of vertical tube filling material influences performance by another ±30% for different materials. Depending on the inlet temperature level to the ground heat exchanger, the dissipated power increases from 2 W m?1 for direct cooling applications at 20 °C up to 52 W m?1 for cooling tower substitutions at 40 °C. This directly influences the cooling costs, which vary between 0.12 and 2.8€ kW h?1.As a result of the work, planning and operation recommendations for the optimal choice of ground coupled heat exchangers for office building cooling can be given.  相似文献   

7.
《Energy Policy》2005,33(6):721-756
We have developed summary tables (sorted by heating- and cooling-degree-days) to estimate the potential of heat-island reduction (HIR) strategies (i.e., solar-reflective roofs, shade trees, reflective pavements, and urban vegetation) to reduce cooling-energy use in buildings. The tables provide estimates of savings for both direct effect (reducing heat gain through the building shell) and indirect effect (reducing the ambient air temperature).In this analysis, we considered three building types that offer the most savings potential: residences, offices, and retail stores. Each building type was characterized in detail by Pre-1980 (old) or 1980+ (new) construction vintage and with natural gas or electricity as heating fuel. We defined prototypical-building characteristics for each building type and simulated the effects of HIR strategies on building cooling- and heating-energy use and peak power demand using the DOE-2.1E model and weather data for about 240 locations in the US. A statistical analysis of previously completed simulations for five cities was used to estimate the indirect savings. Our simulations included the effect of (1) solar-reflective roofing material on building (direct effect), (2) placement of deciduous shade trees near south and west walls of building (direct effect), and (3) ambient cooling achieved by urban reforestation and reflective building surfaces and pavements (indirect effect).Upon completion of estimating the direct and indirect energy savings for all the locations, we integrated the results in tables arranged by heating- and cooling-degree-days. We considered 15 bins for heating-degree-days, and 12 bins for cooling-degree-days. Energy use and savings are presented per 1000 ft2 of roof area.In residences heated with gas and in climates with greater than 1000 cooling-degree-days, the annual electricity savings in Pre-1980 stock ranged from 650 to 1300 kWh/1000 ft2; for 1980+ stock savings ranged 300–600 kWh/1000 ft2. For residences heated with electricity, the savings ranged from 350 to 1300 kWh/1000 ft2 for Pre-1980 stock and 190–600 kWh/1000 ft2 for 1980+ stocks. In climates with less than 1000 cooling-degree-days, the electricity savings were not significantly higher than winter heating penalties. For gas-heated office buildings, simulations indicated electricity savings in the range of 1100–1500 kWh/1000 ft2 and 360–700 kWh/1000 ft2, for Pre-1980 and 1980+ stocks, respectively. For electrically heated office buildings, simulations indicated electricity savings in the range of 700–1400 kWh/1000ft2 and 100–700 kWh/1000 ft2, for Pre-1980 and 1980+ stocks, respectively. Similarly, for gas-heated retail store buildings, simulations indicated electricity savings in the range of 1300–1700 kWh/1000 ft2 and 370–750 kWh/1000 ft2, for Pre-1980 and 1980+ stocks, respectively. For electrically heated retail store buildings, simulations indicated electricity savings in the range of 1200–1700 kWh/1000 ft2 and 250–750 kWh/1000 ft2, for Pre-1980 and 1980+ stocks, respectively.  相似文献   

8.
A solar-powered adsorption chiller with heat and mass recovery cycle was designed and constructed. It consists of a solar water heating unit, a silica gel-water adsorption chiller, a cooling tower and a fan coil unit. The adsorption chiller includes two identical adsorption units and a second stage evaporator with methanol working fluid. The effects of operation parameter on system performance were tested successfully. Test results indicated that the COP (coefficient of performance) and cooling power of the solar-powered adsorption chiller could be improved greatly by optimizing the key operation parameters, such as solar hot water temperature, heating/cooling time, mass recovery time, and chilled water temperature. Under the climatic conditions of daily solar radiation being about 16–21 MJ/m2, this solar-powered adsorption chiller can produce a cooling capacity about 66–90 W per m2 collector area, its daily solar cooling COP is about 0.1–0.13.  相似文献   

9.
A small combined cold and power (SCCP) system is presented. An experimental study of the performance of the SCCP system is described. The gas fuelled SCCP system uses a micro gas turbine generator set and an absorption chiller. The test facility designed and built is also described. The rated electricity power of the micro gas turbine generator is about 24.5 kW at the experimental conditions. When exhaust gas from the micro gas turbine is used to drive the absorption chiller, the rated cooling capacity is 52.7 kW without supplying fuel to burn in the absorption chiller and 136.2 kW with supplying about 78.9 kW LPG fuel to burn in the absorption chiller, respectively. Primary energy rate (PER) and comparative saving of primary energy demand are used to evaluate the performance of the SCCP system. PER of the SCCP system decreases rapidly with the decrease of electric power output when the electric power output is less than 10 kW. The calculated results also show that comparative saving of primary energy demand of the SCCP system decreases with the decrease of electric power output and the SCCP system do not save primary energy comparing to conventional energy system when the electric power output is less than 10 kW.  相似文献   

10.
A solar adsorption cooling system was constructed in the green building of Shanghai Institute of Building Science. The system consisted of evacuated tube solar collector arrays of area 150 m2, two adsorption chillers with nominal cooling capacity of 8.5 kW for each and a hot water storage tank of 2.5 m3 in volume. A mathematical model of the system was established. According to experimental results under typical weather condition of Shanghai, the average cooling capacity of the system was 15.3 kW during continuous operation for 8 h. The theoretical analysis of the system was verified and found to agree well with the experimental results. The performance analysis showed that solar radiant intensity had a more distinct influence on the performance of solar adsorption cooling system as compared with ambient temperature. It was observed that the cooling capacity increased with the increase of solar collector area, whereas, solar collecting efficiency varied quite contrary. With the increase of water tank volume, cooling capacity decreased, while, the solar collecting efficiency increased. The system performances can be enhanced by increasing the height-to-diameter ratio of water tank. Additionally, it was observed that solar collecting efficiency decreased with the increase of the initial temperature of water in the tank; however, cooling capacity varied on the contrary. Also can be seen is that optimum nondimensional mass flow rate is 0.7 when the specific mass flow rate exceeds 0.012 kg/m2 s.  相似文献   

11.
A low-grade waste heat driven solid/vapour adsorption chiller has been successfully designed and tested. A simple model was developed to aid the design and predict the performances. The system comprised two identical sorption reactors operating out of phase in order to ensure continuous cold production. One sorption reactor consisted of six commercially available automotive plate/fin heat exchangers in which silica gel grains were accommodated between the fins. The system was tested as to the power delivered at 12 °C and the power density. The average cooling power was 3.6 kW. This is only 72% of the design value and can be largely attributed to the lower heat transfer fluid flow rate through the sorbent reactor. The thermal efficiency, COP, was 0.62 and the power density was 17 kW/m3 for the system as a whole. Higher power densities are possible. At present, the adsorption chiller is integrated in a prototype trigeneration system, which is tested at CRF’s Eco-building in Turin.  相似文献   

12.
《Energy》2005,30(7):933-951
We present the energy use situation in Hong Kong from 1979 to 2001. The primary energy requirement (PER) nearly tripled during the 23-year period, rising from 195,405 TJ to 572,684 TJ. Most of the PER was used for electricity generation, and the electricity use in residential buildings rose from 7556 TJ (2099 GWh) to 32,799 TJ (9111 GWh), an increase of 334%. Air-conditioning accounted for about 40% of the total residential sector electricity consumption. A total of 144 buildings completed in the month of June during 1992–2001 were surveyed. Energy performance of the building envelopes was investigated in terms of the overall thermal transfer value (OTTV). To develop the appropriated parameters used in OTTV calculation, long-term measured weather data such as ambient temperature (1960–2001), horizontal global solar radiation (1992–2001) and global solar radiation on vertical surfaces (1996–2001) were examined. The OTTV found varied from 27 to 44 W/m2 with a mean value of 37.7  W/m2. Building energy simulation technique using DOE-2.1E was employed to determine the cooling requirements and hence electricity use for building envelope designs with different OTTVs. It was found that cooling loads and electricity use could be expressed in terms of a simple two-parameter linear regression equation involving OTTV.  相似文献   

13.
An innovative cooling system based on evaporative CO2 two-phase flow is under investigation for the tracker detectors upgrade at CERN (European Organization for Nuclear Research). The radiation hardness and the excellent thermodynamic properties emphasize carbon dioxide as a cooling agent in the foreseen minichannels. A circular stainless steel tube in horizontal orientation with an inner diameter of 1.42 mm and a length of 0.3 m has been used as a test section to perform the step-wise scanning of the vapor quality in the entire two-phase region. To characterize the heat transfer and the pressure drop depending on the vapor quality in the tube, measurements have been performed by varying the mass flux from 300 to 600 kg/m2 s, the heat flux from 7.5 to 29.8 kW/m2 and the saturation temperature from ?40 to 0 °C (reduced pressures from 0.136 to 0.472). Heat transfer coefficients between 4 kW/m2 K and 28 kW/m2 K and pressure gradients up to 75 kPa/m were registered. The measured data was analyzed corresponding to the dependencies on heat flux, mass flux and saturation temperature. A database has been established containing about 2000 measurement points. The experimental data was compared with common models recently developed by Cheng et al. [1], [2] to cross check their applicability. The overall trends and experimental data were reproduced as predicted by the models before the dryout onset, and deviations have been analyzed. A modified friction factor for the pressure drop model [1] in mist flow has been proposed based on the experimental data.  相似文献   

14.
Despite its attractiveness, solar cooling technology is still in an early stage of development. Most installations currently in operation show differences in the collector area per kilowatt of cooling capacity that cannot be explained only by project-specific circumstances. The purpose of this paper was twofold. First, to answer some questions that came up during the design process of the plant by using a TRNSYS system model and statistical tools. Second, to gain knowledge about the plant operation and validate the TRNSYS model through measured data. The system was equipped with a flat-plate collector field of 38.4 m2. A lithium bromide-water single-effect absorption chiller (17.6 kW) was selected in order to provide chilled water to fan-coils. Performance data were registered at the solar plant working with a 1000-l heat storage tank and a required temperature of 80 °C to drive the absorption machine. An average of 29% of the solar energy incident on the solar collectors’ surface was transferred to the hot water storage. The registered average COP of the absorption chiller was 0.691. The performance data were compared with the values predicted by the TRNSYS plant model and a high level of agreement was obtained.  相似文献   

15.
The current paper presents experimental investigation of nucleate pool boiling of R-134a and R-123 on enhanced and smooth tubes. The enhanced tubes used were TBIIHP and TBIILP for R-134a and R-123, respectively. Pool boiling data were taken for smooth and enhanced tubes in a single tube test section. Data were taken at a saturation temperature of 4.44 °C. Each test tube had an outside diameter of 19.05 mm and a length of 1 m. The test section was water heated with an insert in the water passage. The insert allowed measurement of local water temperatures down the length of the test tube. Utilizing this instrumentation, local heat transfer coefficients were determined at five locations along the test tube. The heat flux range was 2.5–157.5 kW/m2 for the TBIIHP tube and 3.1–73.2 kW/m2 for the TBIILP tube. The resulting heat transfer coefficient range was 4146–23255 W/m2. °C and 5331–25950 W/m2. °C for both tubes, respectively. For smooth tube testing, the heat flux ranges were 7.3–130.7 kW/m2 and 7.5–60.7 kW/m2 for R-134a and R-123, respectively; with resulting heat transfer coefficient ranges of 1798.9–11,379 W/m2. °C and 535.4–3181.8 W/m2. °C. The study provided one of the widest heat flux ranges ever examined for these types of tubes and showed significant structure to the pool boiling curve that had not been traditionally observed. Additionally, this paper presented an investigation of enhanced tubes pool boiling models.  相似文献   

16.
Accurate measurement of solar radiation heat flux is important in characterizing the performance of CSP plants. Thermopile type Heat Flux Sensors (HFSs) are usually used for this purpose. These sensors are typically reasonably accurate at high heat fluxes. However measurement accuracy drops significantly as the measured radiation is below 1 kW/m2, this often leads to underestimation of the actual flux. At the Masdar Institute Beam Down Solar Thermal Concentrator (BDSTC), measurement of fluxes ranging from 0 kW/m2 to more than 100 kW/m2 is required. To improve the accuracy of the sensors in the lower range around 1 kW/m2, we have performed a test under ambient (not-concentrated) sunlight. Such low irradiation levels are experienced in characterizing the concentration quality of individual heliostats. It was found during the test that the measurement at this low range is significantly affected by ambient conditions and transients in the HFS cooling water temperature. A Root Mean Square Error (RMSE) of more than 100 W/m2 was observed even though we kept the transients in water temperature to a minimum. Hence we devised a model to account for this measurement error at this flux range. Using the proposed model decreased the RMSE to less than 10 W/m2. The application of the model on existing heat flux measurement installations is facilitated by the fact that it only employs easily measurable variables. This model was checked by using a test data set and the results were in good agreement with the training data set.  相似文献   

17.
Australia is a country with a vast amount of natural resources including sun and wind. Australia lies between latitude of 10–45°S and longitude of 112–152°E, with a daily solar exposure of between less than 3 MJ/(m2 day) in winter and more than 30 MJ/(m2 day) in summer.Global solar radiation in Australia varies between minimum of 3285 MJ/(m2 year) in Hobart to 8760 MJ/(m2 year) in Northern Territory. As a result of this wide range of radiation level there will be a big difference between costs of solar PV electricity in different locations.A study we have recently conducted on the solar PV electricity price in all states of Australia. For this purpose we have developed an economical model and a computer simulation to determine the accurate unit price of grid-connected roof-top solar photovoltaic (PV) electricity in A$/kWh for all state of Australia. The benefit of this computer simulation is that we can accurately determine the most appropriate feed-in tariff of grid-connected solar PV energy system. The main objective of this paper is to present the results of this study.A further objective of this paper is to present the details of the unit price of solar PV electricity in the state of Victoria in each month and then to compare with electricity price from conventional power systems, which is currently applied to this state. The state Victoria is located south of Australia and in terms of sun radiation is second lowest compared with the other Australian states.The computer simulation developed for this study makes it possible to determine the cost of grid-connected solar PV electricity at any location in any country based on availability of average daily solar exposure of each month as well as economical factors of the country.  相似文献   

18.
In this paper, a solar-powered compound system for heating and cooling was designed and constructed in a golf course in Taiwan. An integrated, two-bed, closed-type adsorption chiller was developed in the Industrial Technology Research Institute in Taiwan. Plate fin and tube heat exchangers were adopted as an adsorber and evaporator/condenser. Some test runs have been conducted in the laboratory. Under the test conditions of 80 °C hot water, 30 °C cooling water, and 14 °C chilled water inlet temperatures, a cooling power of 9 kW and a COP (coefficient of performance for cooling) of 0.37 can be achieved. It has provided a SCP (specific cooling power) of about 72 W/(kg adsorbent). Some field tests have been performed from July to October 2006 for providing air-conditioning and hot water. The efficiency of the collector field lies in 18.5–32.4%, with an average value of 27.3%. The daily average COP of the adsorption chiller lies in 33.8–49.7%, with an average COP of 40.3% and an average cooling power of 7.79 kW. A typical daily operation shows that the efficiency of the solar heating system, the adsorption cooling and the entirely solar cooling system is 28.4%, 45.2%, and 12.8%, respectively.  相似文献   

19.
The 100 kW high concentration photovoltaic (HCPV) system has been constructed in October 2007 at the Institute of Nuclear Energy Research (INER), Taiwan. The maximum module efficiency with a geometrical concentration ratio of 476× is about 26.1% under 850 W/m2 DNI and passive cooling conditions [Cherng-Tsong Kuo. The project of demonstrating MW high concentration photovoltaic (HCPV) system. Science and technology yearbook of Taiwan. ROC; 2008]. The 100 kW HCPV system consists of 14 sets of pillar-stand 5 kW systems and 21 sets of roof-top 1.5 kW systems. Each 5 kW system and 1.5 kW are comprised of 40 modules and 12 modules respectively. Each module was integrated with 40 solar cells with 35% conversion efficiency each, manufactured by Spectrolab Company, the highest III-V solar cell conversion efficiency record keeper. This project is the pioneer for the establishment of one MW HCPV demonstration system in 2008.  相似文献   

20.
《Applied Thermal Engineering》2007,27(13):2188-2194
Mediterranean countries show two specific features regarding air-conditioning of buildings: a high—and growing—cooling load and high relative humidity, at least in coastal zones. In this contribution we report on the development of an innovative micro scale tri-generation system (power + heating + cooling), equipped with a rotor based desiccant system adapted to the Mediterranean conditions which receives heat for the desiccant regeneration from a combined heat and power (CHP) cycle.The paper presents the design of the advanced desiccant air handling unit which uses a high efficient combination of a vapor compression chiller working at a high evaporator temperature and a desiccant wheel (silica gel). The electricity of the chiller is supplied by the CHP system and the heat to regenerate the desiccant is the waste heat of the CHP. System simulations have been used to optimize the hydraulic design and the operation strategy in order to minimize operation costs and maximize energy savings. Some new component models, e.g. for the advanced desiccant cycle were developed for this purpose. The final design of the entire system consisting of the CHP system, the vapor compression chiller, the advanced desiccant air handling unit and the load system is described. The load system is composed of an air duct network with induction units and a chilled water network with fan-coils in the office rooms.Regarding energy performance results indicate an electricity saving >30% in comparison to state-of-the-art solutions based on conventional technology.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号