Characterization of energy use in 300 mm DRAM (Dynamic Random Access Memory) wafer fabrication plants (fabs) in Taiwan

Driven by technology advances and demand for enhanced productivity, migration of wafer fabrication for DRAM (Dynamic Random Access Memory) toward increased wafer size has become the fast-growing trend in semiconductor industry. Taiwan accounts for about 18% of the total DRAM wafer production in the world. The energy use required for operating wafer fabrication plants (fabs) is intensive and has become one of the major concerns to production power reliability in the island. This paper characterizes the energy use in four 300 mm DRAM wafer fabs in Taiwan through performing surveys and on-site measurements. Specifically, the objectives of this study are to characterize the electric energy consumption and production of 300 mm DRAM fabs by using various performance metrics, including PEI ((production efficiency index), annual electric power consumption normalized by annual produced wafer area) and EUI ((electrical utilization index), annual electric power consumption normalized by UOP (units of production), which is defined as the product of annual produced wafer area and the average number of mask layers of a wafer). The results show that the PEI and EUI values are 0.743 kWh/cm² and 0.0272 kWh/UOP, respectively. Using EUI in assessing energy efficiency of the fab production provides more consistent comparisons than using PEI alone.     

Building energy index and end-use energy analysis in large-scale hospitals—case study in Malaysia

Hospital energy consumption is relatively high, while saving energy and reducing cost comprise one of the most important challenges considered by the majority of building designers, engineers, and decision makers. An end-use energy analysis was conducted in a large-scale hospital in Malaysia to identify energy apportioning and energy end use in the areas of air conditioning, lifts, lighting, equipment, and others. The analysis was carried out by assessing the collected desktop and field data as well as some calculations. The Building Energy Index (BEI) was calculated to compare the consumption levels in the selected hospital, which is a typical hospital building, with other hospitals in Malaysia as well as low energy buildings and Malaysian standards. The main energy source in this case study was electricity with a supply of around 75 % of total energy consumption. The current average annual electricity consumed by this hospital was 44,637,966 kWh, out of which 63 % was used by air conditioning systems and 17 % by lighting. The BEI comparison revealed that the calculated BEI of 384 kWh/m²/year is significantly higher than Malaysian rating systems and standards which recommend 200 kWh/m²/year for hospitals, 135 kWh/m²/year for commercial sectors, and is higher than previously observed hospitals with a BEI of less than 300 kWh/m²/year.     

A computer study for estimation of seasonal energy consumption and selection of air-conditioner in six Saudi Arabian cities

A computer model was developed to simulate the building cooling load and the seasonal energy consumption of standard residential sized central air-conditioning systems. The model was first validated by comparing the predicted cooling energy consumption against the metered energy of a 100 m² residence. The model predicts within 10% of the metered value. The validated model was next used to compute the cooling load and seasonal energy consumption for similar 100 m² residences in six cities located in different climatic zones of Saudi Arabia. Simulations showed that the cities of Dhahran and Riyadh required a 17.6 kW system to satisfy the cooling load through the year, whereas the defined residences in the cities of Taif, Hail, Jeddah and Gizan required a 14.1 kW system. Our analysis showed that the selected residence in Gizan would consume 23,100 kWh annually, while a comparable residence located in Dhahran, having a more severe summer, required only 21,500 kWh. This difference may be explained by analysis of the weather data which revealed that Gizan required year-round cooling, whereas Dhahran needed cooling for only 283 days during the year. Investigation showed that, by selecting the next smaller capacity air-conditioning unit for each location than required to satisfy the load for 100% of the time, the annual power consumption may be reduced, on an average, by 10%, with about 7% of the hours during the cooling season when the air-conditioning load may not be satisfied.     

Hydropower potential of municipal water supply dams in Turkey: A case study in Ulutan Dam

This paper aims to analyze the hydropower potential of municipal water supply dams in Turkey. The facility is in favor with the energy policy of Turkish Government and European Union. In the study, the design head of the power plant was selected as the average water level of the reservoir and the discharge was calculated from the annual water supply of the dam. It has been estimated that the existing 45 municipal water supply dams of Turkey have an electric energy potential of 173 GWh/year, corresponding to about 24,000,000 Euro/year economic benefit. The financing of these facilities can be provided from international funding institutions. For a case study, Zonguldak Ulutan Dam and its water treatment plant have been investigated in detail. The current electricity consumption of the water treatment plant is 4,500,000 kWh/year and the facility provides 35,000 m³/day water to 6 settlements. The installation of a hydropower plant on the mentioned water treatment plant will cut the electric consumption by 24%. The proposed project has a payback period of 1.4 years and it can produce clean and feasible energy.     

A study of energy performance and audit of commercial mall in hot-summer/warm-winter climate zone in China

The building energy performance improvement of large-scale public buildings is very important to release China’s energy shortage pressure. The aim of the study is to find out the building energy saving potentials of large-scale public and commercial buildings by energy audit. In this paper, the energy consumption, energy performance, and audit were carried out for a typical commercial mall, the so-called largest mall in Asia, located in a hot-summer and warm-winter climate zone. The total annual energy consumption reaches 210.01 kWh/m², of which lighting energy consumption accounts for 30.03 kWh/m² and the lift and elevator energy consumption accounts for 40.46 kWh/m². It is by far higher than that of the average building energy consumption in the same category. However, the annual heating, ventilation, and air-conditioning (HVAC) energy consumption is only 87.19 kWh/m² even though they run 24/7. It proves that the energy performance of the HVAC system is good. Therefore, the building energy savings potential mainly relies on reducing the excessive usage of lighting, lifts, and elevators.     

Improved components for advanced alkaline water electrolysis

The industrial realization of an advanced electrolysis cell for alkaline water electrolysis is gradually achieved and semitechnical cell units were constructed. The cells work with ceramic diaphragms and galvanically-deposited Raney nickel electrodes. The working temperature is 100–120°C and total pressure between 1 and 5 bar. The average energy consumption at 0.4 A cm⁻² and 100°C is 3.8 kWh m⁻³ hydrogen. The influence of cell components on total cell performance data is discussed. The variation of manufacturing parameters on the quality of single components (electrodes and diaphragm) is considered. Corrosion problems at operating conditions and their elimination by using proper construction techniques were investigated.     

Energy and environmental evaluation of municipal facilities: Case study in the province of Barcelona

The service sector is extraordinarily important for the European economy, as it accounts for 75% of the GDP. Yet it is also a huge consumer of energy, especially in urban environments. Municipalities have the authority to develop and manage municipal services, and as a result the European Commission drew up the Covenant of Mayors in which the signatory municipalities pledge to reduce their CO₂ emissions by 20% of their 1990 rates. Sustainable Energy Action Plans (SEAPs) emerged from this covenant with the goal of analysing the current consumption patterns and compiling the actions that the municipalities should undertake in order to fulfil their pledges.This article focuses on analysing the energy consumption and greenhouse gas emissions of 978 municipal service facilities in the province of Barcelona in the year 2005. The average consumption per facility by surface area is 118.8 kWh/m². Regarding greenhouse gas emissions, the average annual emissions in the facilities studied in the province of Barcelona were 40.0 kg CO₂ eq/m².     

Performance assessment of an integrated free cooling and solar powered single-effect lithium bromide-water absorption chiller

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/kW_cold) and the solar energy system support of the institute heating system for the duration from August 2002 to November 2007 is 8124 kWh.     

Economic viability in thermal retrofit policies: Learning from ten years of experience in Germany

Germany aims to reduce CO₂ emissions by 80% by 2050 compared to 1990 levels and has merged this target with mandatory Energy Saving Regulations for thermal renovation of existing homes: the policy uses the criterion of ‘economic viability’, whereby renovations must pay back through the space and water heating fuel savings they produce. This paper explores the extent to which economically viable thermal renovations can contribute to the 80% goal, based on an analysis of Germany’s experience. It finds that the theoretical savings being achieved, based on calculated pre- and post-renovation consumption, are around 33%, while actual savings, based on measured consumption, are likely to be around 25%. The difference appears to be due to the effects of household behaviour. Further, average measured consumption is estimated to be around 150–180 kWh/m²a nationally, and this would have to be reduced to 30–35 kWh/m²a to meet the 80% policy goal. This is beyond the limits of economically viable renovation technology, which currently achieves around 100 kWh/m²a. The paper suggests that policymakers should de-couple the criterion of economic viability from the 80% goal, emphasise other reasons for renovating to economically viable levels, and consider a more systematic approach to facilitate household behaviour change.     

System performance and economic analysis of solar-assisted cooling/heating system

The long-term system simulation and economic analysis of solar-assisted cooling/heating system (SACH-2) was carried out in order to find an economical design. The solar heat driven ejector cooling system (ECS) is used to provide part of the cooling load to reduce the energy consumption of the air conditioner installed as the base-load cooler. A standard SACH-2 system for cooling load 3.5 kW (1 RT) and daily cooling time 10 h is used for case study. The cooling performance is assumed only in summer seasons from May to October. In winter season from November to April, only heat is supplied. Two installation locations (Taipei and Tainan) were examined.It was found from the cooling performance simulation that in order to save 50% energy of the air conditioner, the required solar collector area is 40 m² in Taipei and 31 m² in Tainan, for COP_j = 0.2. If the solar collector area is designed as 20 m², the solar ejector cooling system will supply about 17–26% cooling load in Taipei in summer season and about 21–27% cooling load in Tainan. Simulation for long-term performance including cooling in summer (May–October) and hot water supply in winter (November–April) was carried out to determine the monthly-average energy savings. The corresponding daily hot water supply (with 40 °C temperature rise of water) for 20 m² solar collector area is 616–858 L/day in Tainan and 304–533 L/day in Taipei.The economic analysis shows that the payback time of SACH-2 decreases with increasing cooling capacity. The payback time is 4.8 years in Tainan and 6.2 years in Taipei when the cooling capacity >10 RT. If the ECS is treated as an additional device used as a protective equipment to avoid overheating of solar collectors and to convert the excess solar heat in summer into cooling to reduce the energy consumption of air conditioner, the payback time is less than 3 years for cooling capacity larger than 3 RT.     

Cooling cogeneration cycle

The existed combined power and cooling cycle operates with ammonia–water mixture as working fluid having low cooling due to the vapor at the inlet of evaporator. It also demands high ammonia concentration at turbine inlet to get cooling and suitable only at low sink temperature (10–12°C). A new cooling cogeneration cycle has been proposed and solved to generate more cooling with adequate power generation from single source of heat with two options in working fluids i.e. ammonia–water mixture and LiBr–water mixture. The results show that an increase in cycle maximum temperature is only supporting the power but not the cooling. A suitable range for separator temperature has been developed and optimized to maximize the total output. From this study, the resulted specific power, specific cooling, cycle power efficiency, cycle coefficient of performance (COP) and cycle energy utilization factor (EUF), plant EUF, and specific area of solar collector are 0.008 kW/m², 0.11 kW/m², 2%, 0.28, 0.3, 0.13 and 8 m²/kW for ammonia–water cycle and 0.04 kW/m², 0.3 kW/m², 9.5%, 0.7, 0.8, 0.37 and 3 m²/kW for LiBr–water mixture plant respectively.     

Potential benefits of cool roofs on commercial buildings: conserving energy, saving money, and reducing emission of greenhouse gases and air pollutants

Cool roofs—roofs that stay cool in the sun by minimizing solar absorption and maximizing thermal emission—lessen the flow of heat from the roof into the building, reducing the need for space cooling energy in conditioned buildings. Cool roofs may also increase the need for heating energy in cold climates. For a commercial building, the decrease in annual cooling load is typically much greater than the increase in annual heating load. This study combines building energy simulations, local energy prices, local electricity emission factors, and local estimates of building density to characterize local, state average, and national average cooling energy savings, heating energy penalties, energy cost savings, and emission reductions per unit conditioned roof area. The annual heating and cooling energy uses of four commercial building prototypes—new office (1980+), old office (pre-1980), new retail (1980+), and old retail (pre-1980)—were simulated in 236 US cities. Substituting a weathered cool white roof (solar reflectance 0.55) for a weathered conventional gray roof (solar reflectance 0.20) yielded annually a cooling energy saving per unit conditioned roof area ranging from 3.30 kWh/m² in Alaska to 7.69 kWh/m² in Arizona (5.02 kWh/m² nationwide); a heating energy penalty ranging from 0.003 therm/m² in Hawaii to 0.14 therm/m² in Wyoming (0.065 therm/m² nationwide); and an energy cost saving ranging from 0.126/m < sup > 2 < /sup > in West Virginia to0.126/m² in West Virginia to 1.14/m² in Arizona ($0.356/m² nationwide). It also offered annually a CO₂ reduction ranging from 1.07 kg/m² in Alaska to 4.97 kg/m² in Hawaii (3.02 kg/m² nationwide); an NO_x reduction ranging from 1.70 g/m² in New York to 11.7 g/m² in Hawaii (4.81 g/m² nationwide); an SO₂ reduction ranging from 1.79 g/m² in California to 26.1 g/m² in Alabama (12.4 g/m² nationwide); and an Hg reduction ranging from 1.08 μg/m² in Alaska to 105 μg/m² in Alabama (61.2 μg/m² nationwide). Retrofitting 80% of the 2.58 billion square meters of commercial building conditioned roof area in the USA would yield an annual cooling energy saving of 10.4 TWh; an annual heating energy penalty of 133 million therms; and an annual energy cost saving of $0.356/m² nationwide). It also offered annually a CO₂ reduction ranging from 1.07 kg/m² in Alaska to 4.97 kg/m² in Hawaii (3.02 kg/m² nationwide); an NO_x reduction ranging from 1.70 g/m² in New York to 11.7 g/m² in Hawaii (4.81 g/m² nationwide); an SO₂ reduction ranging from 1.79 g/m² in California to 26.1 g/m² in Alabama (12.4 g/m² nationwide); and an Hg reduction ranging from 1.08 μg/m² in Alaska to 105 μg/m² in Alabama (61.2 μg/m² nationwide). Retrofitting 80% of the 2.58 billion square meters of commercial building conditioned roof area in the USA would yield an annual cooling energy saving of 10.4 TWh; an annual heating energy penalty of 133 million therms; and an annual energy cost saving of 735 million. It would also offer an annual CO₂ reduction of 6.23 Mt, offsetting the annual CO₂ emissions of 1.20 million typical cars or 25.4 typical peak power plants; an annual NO_x reduction of 9.93 kt, offsetting the annual NO_x emissions of 0.57 million cars or 65.7 peak power plants; an annual SO₂ reduction of 25.6 kt, offsetting the annual SO₂ emissions of 815 peak power plants; and an annual Hg reduction of 126 kg.     

Thermodynamics analysis of a hybrid system based on a combination of hydrogen fueled compressed air energy storage system and water electrolysis hydrogen generator

In front of the opportunity of the rapid development of renewable energy power generation, energy storage is playing a more important role in improving its utilization efficiency. In this paper, a hybrid energy system based on combination of hydrogen fueled compressed air energy storage system and water electrolysis hydrogen generator is proposed. The superfluous renewable energy power is charged by compressing the air and/or producing hydrogen through water electrolysis. A hydrogen combustor is introduced to raise the air temperature in the discharging process. A thermodynamic model of the proposed system is built. Energy and exergy analysis found that under the design condition, the proposed system can achieve a round trip efficiency of 65.11%, an exergy efficiency of 79.23%, and an energy storage density of 5.85 kWh/m³. The exergy loss of water electrolysis hydrogen generator and hydrogen combustor rank in the top two of all components. Sensitivity analysis indicates that the outlet temperature of hydrogen combustor and specific energy consumption of water electrolysis hydrogen generator are the crucial influencing factor of system performance.     

Design and installation of solar photovoltaic powered water pumping system at Usmanu Danfodiyo University, Sokoto

The paper presents the outcome of the powering of a conventional a.c. type water pump by photovoltaic (pv) solar modules which were 28 in number connected 7 in series giving a total of 4 parallel strings. An assesment of the system, which provides water to the University Mechanical Workshop and a nearby village, shows that the system has been operating continously since October 1993 and on average 20 m³ of water is pumped daily at average solar radiation level of 5kWh/m²/day.     

Economic perspective of PV electricity in Oman

Solar and wind energies are likely to play an important role in the future energy generation in Oman. This paper utilizes average daily global solar radiation and sunshine duration data of 25 locations in Oman to study the economic prospects of solar energy. The study considers a solar PV power plant of 5-MW at each of the 25 locations. The global solar radiation varies between slightly greater than 4 kWh/m²/day at Sur to about 6 kWh/m²/day at Marmul while the average value in the 25 locations is more than 5 kWh/m²/day. The results show that the renewable energy produced each year from the PV power plant varies between 9000 MWh at Marmul and 6200 MWh at Sur while the mean value is 7700 MWh of all the 25 locations. The capacity factor of PV plant varies between 20% and 14% and the cost of electricity varies between 210 US$/MWh and 304 US$/MWh for the best location to the least attractive location, respectively. The study has also found that the PV energy at the best location is competitive with diesel generation without including the externality costs of diesel. Renewable energy support policies that can be implemented in Oman are also discussed.     

Performance degradation of an air-conditioner caused by cyclic operations

We have illustrated the effect of degradation in the seasonal coefficient of performance (COP) of an air-conditioner caused by cyclic operations. This degradation is demonstrated for a 100 m² residence in Dhahran equipped with a 17.6 kW capacity central unit. A computer model simulates cooling loads and transient (start-up) losses. Simulations show that cyclic losses can be as high as 22% during months of low cooling. The system experienced little degradation during the peak cooling period. The annual steady-state energy consumption is 17,900 kWh; transient start-stop penalties required an additional 2100 kWh, which agrees within 5% with the annual metered consumption. Cyclic losses are significantly reduced with design changes that prevent refrigerant migration during the off-cycle period. The seasonal steady-state and cyclic COP values were found to be 2.11 and 1.88, respectively.     

A photovoltaic-powered system for medium-head pumping

A prototype photovoltaic-powered pumping system capable of supplying 15 m³ of water per day in full sunlight at heads of around 35 m has been developed. Design criteria are based on requirements for drinking water supplies to small villages in tropical countries.The system consists of a well-known and widely used pump (the Mono^®† progressive cavity pump) driven by a very efficient dc motor with long brush life, which is supplied with power from a dc-dc converter. The power source is a 800 W photovoltaic array. Laboratory testing of the whole system shows that it is reliable and has an overall sunlight to pumped-water efficiency in excess of 3%. This is comparable to the highest efficiencies that have been reported elsewhere for solar powered pumps. The system behaves well at heads other than the design head (35 m) and has been tested over the range 25 to 55 m. Simulations of the volumes of water pumped during standard solar days of 4 kWh/m² and 5 kWh/m² have enabled comparisons to be made with published tests on other solar powered pumps. The present system easily meets the established criteria.     

Thermodynamic analysis of low-temperature and high-pressure (cryo-compressed) hydrogen storage processes cooled by mixed-refrigerants

Cryo-compressed hydrogen (CcH₂) is a promising hydrogen storage method with merits of high density with low power consumption. Thermodynamic analysis and comparison of several CcH₂ processes are conducted in this paper, under hydrogen storage conditions of 10–100 MPa at 60–100 K. Mixed-refrigerant J-T (MRJT), nitrogen/neon reverse Brayton (RBC) and hydrogen expansion are employed for cooling hydrogen, respectively. Combined CcH₂ processes such as MRJT + neon-RBC are proposed to reach higher CcH₂ density at lower temperatures (<80 K). It was indicated that the specific power consumptions (SPC) of MRJT processes are obviously lower than those of nitrogen/neon-RBC or hydrogen expansion processes. For a typical storage condition of 50 MPa at 80 K, MRJT CcH₂ process could achieve hydrogen density of 71.59 kg m^?3, above liquid hydrogen. While its SPC of 6.42 kWh kg^?1 is about 40% lower than current dual-pressure Claude hydrogen liquefaction processes (10.85 kWh kg^?1).     

Gliding arc plasma oxidative steam reforming of a simulated syngas containing naphthalene and toluene

Conversion of a simulated syngas containing vaporized toluene and naphthalene was studied in a non-equilibrium gliding arc plasma reformer. The reformer was designed for efficient reforming of high temperature syngas (greater than 650 °C) containing heavy hydrocarbons, air, and water vapor. The reactor utilized forward vortex flow, where a preheated simulated syngas containing vaporized naphthalene and toluene tar surrogate was injected tangentially in the flow to ensure effective mixing and reforming of all components. At low tar concentration (30 g/m³), over 90% naphthalene and toluene conversion was achieved at the benchmark specific energy input of 0.1 kWh/m³ and energy efficiencies of 62.5 g/kWh for naphthalene and 215 g/kWh for toluene. At higher tar concentration (75 g/m³), over 70% naphthalene and toluene conversion was achieved at the benchmark specific energy input of 0.1 kWh/m³ and energy efficiencies of 93.6 g/kWh for naphthalene and 369 g/kWh for toluene. Explanations for the results include effective gas mixing and plasma chemistry, such as the very fast reaction kinetics from ions, radicals and active species, specifically hydroxyl.     

Energy assessment of the Portuguese meat industry

The meat product industries play a major role in many global economies. In several countries, it is the industry with a higher economic weight within the food industries. As refrigeration systems are indispensable within the production processes, it is important to improve the overall energy efficiency in order to reduce the electricity consumption in these industries. The electrical energy consumption of the Portuguese meat industries is evaluated in this paper. The field study shows that electrical energy accounts for 66.5 % of the overall energy consumption in slaughterhouses, 85 % in sausage houses and 92.5 % in ham industries. Relatively to the refrigeration systems of these industries, results show that the average compressor nominal power per unit of cold room volume is comprised between 0.072 and 0.043 kW/m³. The average value of the specific electrical energy consumption for the slaughterhouses was 149 kWh/ton_HSCW, 660 kWh/ton_RM for sausage houses and 1208 kWh/ton_RM for ham production industries. Finally, a potential reduction of the electricity consumption based on simple energy efficiency measures was estimated in 24 % for the slaughterhouses, 13 % for the sausage houses and 8 % for the ham industry.