Characterization of minienvironments in a clean room: Design characteristics and environmental performance

A minienvironment is normally used to maintain a level of stringent cleanliness through controlling particle concentrations within a tightened volume of clean spaces. Because minienvironments are expected to locally achieve a higher level of cleanliness than their adjacent clean room, it is important to understand the characteristics of their design and operation and effectiveness in environmental control. This paper presents findings from an in-situ study on a group of minienvironments, with the focus on characterizing and evaluating environmental performance of the minienvironments as part of a large-scale of in-situ investigation into the total performance of the minienvironments operating in a clean room. In particular, this paper summarizes design and operating characteristics and presents measured environmental performance of five minienvironments and the clean room that housed them. The study discovers that pressure differentials as low as under 0.2 Pa can be sufficient for achieving a high level of air cleanliness to meet environmental control expectation and requirements. Comparisons with relevant industry standards show that existing standards or guidelines may have been suggesting thresholds that are higher than necessary at least in some minienvironment applications. The paper suggests potential benefits from identifying and optimizing the required range of pressure differentials, and likely opportunities and challenges in improving the system's total performance through further studies and refining relevant standards.     

Performance of large fan-filter units for cleanroom applications

Fan-filter units (FFUs) are widely used in clean space to re-circulate and remove particles out of the airflows directed to cleanrooms or minienvironments. Energy and aerodynamic performance of FFUs may largely influence both energy efficiency and effectiveness in contamination control in the cleanroom design, qualifications, and operation. This article presents laboratory-measured performance of seven relatively new and large FFUs, with a section size of 122-cm×122-cm, or 4-ft×4-ft. In addition, this article includes a comparison of the performance of these large FFUs with that of smaller, 122-cm×61-cm (or 4-ft×2-ft) FFUs that were previously tested. The comparison was based upon a set of performance metrics such as total pressure efficiency (TPE) and energy performance index (EPI). This article found that there were wide variations in the energy performance of FFUs, and that using a consistent evaluation method can generate comparable FFU performance information. When operating at the maximal setting of speed control dials used to control their respective fan-wheel speeds, the larger units in this study tended to be more energy efficient than their smaller counterparts. The energy efficiency level of the same unit may vary considerably, depending on actual operating conditions such as airflow speeds and pressure rise across the units. Furthermore, this article provides recommendations for further investigations to improve energy efficiency of FFU applications.     

Costing small cleanrooms

The quick development of high technology and life sciences industries nowadays sees the need for more and better cleanrooms in modern laboratories expanding dramatically. Cleanrooms, as mechanically intensive facilities that consume large amount of energy to maintain its defined environment demand high capital and operating costs. The owners also expect the cleanrooms to be constructed with less money, less time, yet with higher performance standards and lower running costs. Most cleanroom designs and construction are customized for a wide-ranging scale of operations. To date, not only there is no complete study on cost of the entire lifetime of cleanroom, but also no standard cost system available, which makes it fairly difficult to verify and project the costs of cleanroom design and construction. In order to obtain accurate costing, it is necessary to establish a thoughtful cost framework based on the critical parameters of the facility. This paper defines the critical elements of cleanroom design that would significantly impact the costs of its construction. It also presents the relationships among the elements within the cost model. The cost model is applied to small cleanrooms, which has an increasing demand from entrepreneurs and small and medium enterprises. Such small, standard and modular cleanrooms are suitable for individual inventors, small high-tech manufacturers and school laboratories.     

Cleanroom energy efficiency strategies: Modeling and simulation

To maintain ultra-low particle concentrations, cleanrooms can require several hundred air changes per hour. These ventilation rates make cleanrooms 30-50 times more energy intensive than the average U.S. commercial building. There are an estimated 12 million m² of cleanroom space in the U.S., consuming over 370 PJ of energy each year. This paper explores opportunities to improve the energy efficiency of cleanrooms while maintaining or improving operating conditions.This paper documents the modeling of a 1600 m² cleanroom in upstate New York. The TRNSYS model includes TMY2 weather data; building geometry and material properties; empirical data on occupancy, lighting and process equipment; and sophisticated HVAC systems. The model was validated based on metered steam, chilled water and electricity usage. Under 8% error was achieved in all fields.Four strategies were simulated: a heat recovery system for exhaust air, resulting in an 11.4% energy reduction with a 2.7-year simple payback; solar preheating of desiccant dehumidifier regeneration air (2.4% energy reduction, 11.5-year payback); improved lighting controls (0.3% energy reduction, 1.5-year payback); and demand-controlled filtration (4.4% energy reduction, 3.1-year payback). Implementation of recommended strategies is predicted to save 9 TJ, 862 tonnes of CO₂, and $164k annually.     

Capturing energy-saving opportunities in make-up air systems for cleanrooms of high-technology fabrication plant in subtropical climate

Operation of make-up air units (MAUs) for cleanrooms of high-technology fabrication plant in subtropical climates is very energy intensive, in that it is expected to deliver conditioned air at elevated airflow rates, compared to conventional commercial applications. Optimizing the design of MAU via reducing or displacing mechanical cooling or electrical heating processes can improve energy efficiency in cleanrooms since cleanroom air-conditioning systems typically use 30-65% of the total energy consumption in a high-tech fabrication plant [1]. This paper investigates the difference in energy efficiency performance of MAU systems with different pre-cooling and preheating/humidification schemes. Additionally, a comparative study was carried out for humidification schemes including wet media, directly atomized water, steam, and two-phase flow. The results show that energy recovery by DCC water return method exhibits the best energy efficiency among a total of eight schemes evaluated in this study. In addition, wet media scheme is the best humidification scheme in winter time, compared with the other three types of humidification schemes.     

Innovative method for energy management: Modelling and optimal operation of energy systems

This paper presents an optimal management control strategy for power systems in industrial plants. A dedicated code has been developed to perform system analysis and simulation. The energy/mass balances existing between building and power plant has been depicted through a mathematical model based on vector equations, taking into account the behaviour of each system component. The main result is the definition of the power plant component set points satisfying the energy load under predefined optimization criterion (i.e. system efficiency, costs, pollutant emissions). Input data are the industrial plant loads, both electric and thermal, the technical characteristic of the installations, and the cost of electricity and fuel. As a general result we show that the optimal management of a power plant is as significant as the efficiency of its components for energy saving purposes. In particular, the correlation between the component set point profiles and the energy/cost/pollution savings is highlighted. Yearly simulations are performed on an existing energy system of an industrial plant varying the frequency of energy load dataset. The considered time steps are month, half a day, 4 h and 1 h. The results demonstrate that the whole power plant management leads to a global reduction of the cost and that the availability of more detailed energy load dataset leads to better operation cost estimation. As expected, considering a large time-step, the variation of energy load is not appreciable.The energy saving potential of this method is demonstrated allowing the best plant management solution under different energy loads.     

Using energy audits to investigate the impacts of common air-conditioning design and installation issues on peak power demand and energy consumption in Austin, Texas

This study presents an analysis of a unique dataset of 4971 energy audits performed on homes in Austin, Texas in 2009–2010. We quantify the prevalence of typical air-conditioner design and installation issues such as low efficiency, oversizing, duct leakage, and low measured capacity, and estimate the impacts that resolving these issues would have on peak power demand and cooling energy consumption. We estimate that air-conditioner use in single-family residences currently accounts for 17–18% of peak demand in Austin, and we found that improving equipment efficiency alone could save up to 205 MW, or 8%, of peak demand. We estimate that 31% of systems in this study were oversized, leading to up to 41 MW of excess peak demand. Replacing oversized systems with correctly sized higher efficiency units has the potential for further savings of up to 81 MW. We estimate that the mean system could achieve 18% and 20% in cooling energy savings by sealing duct leaks and servicing their air-conditioning units to achieve 100% of nominal capacity, respectively. Although this analysis is limited to the City of Austin, understanding the methods described herein could allow electric utilities in similar climates to make better-informed decisions when considering efficiency improvement programs.     

Solar energy systems installed on Chinese-style buildings

A building-integrated solar energy system is proposed, with the panels installed such that the overall morphology resembles that of a traditional Chinese building, i.e., roofing (eaves) at each storey, in addition to that on top of the building. The panels include photovoltaic cells and solar thermal collectors, thus producing electric power as well as heating. The particular morphology provides a number of advantages, in terms of solar energy collection and shading, and their matching to temporal and locational variations in energy demand. These are in addition to the advantages of solar energy generally. Solar heating and photovoltaic power generation were calculated for a number of locations. These were compared with the space heating and air conditioning demands, respectively. The requirement for supplementary energy was calculated. Equivalent calculations for similar buildings without solar panels allowed the saving in non-solar energy to be estimated. Calculations were made for Beijing in winter, as an example of high space heating demand, for Hong Kong in summer, as an example of high air conditioning demand, and for Shanghai, as an intermediate example. These showed potential savings of up to 15% in space heating, and up to 55% in air conditioning energy demand.     

Empirical analysis of the Russian power industry's transition to sustainability

Solutions to sustainability challenges often focus on low-carbon energy transition. This paper highlights the Russian electric power industry's barriers to and drivers for achieving zero emissions by 2060. The methods used include policy analysis and an econometric analysis of variables that affect and are affected by per capita electricity consumption in 1990–2021. The results show that while renewables lower overall electricity use, economic growth, financial development, and CO₂ emissions increase use. A bidirectional causality exists from trade openness and CO₂ emissions to electricity consumption. A sustainable energy transition framework is proposed based on consolidating selected policy tools.     

Experimental study on airflow characteristics and temperature distribution in non-unidirectional cleanrooms for electronic industry

A non-unidirectional airflow cleanroom in electronic industries is prone to be challenged by the wide spread of hot air and contaminants dissipated from process tools to surrounding area, resulting from the collision of the uprising hot air current from the tools and the downward cold air from ceilings. To effectively remove the dissipated heat and maintain the required cleanliness level, we proposed an innovative fan dry coil unit (FDCU) return air system (referring to  and ), consisting of ceiling-supply grilles and ceiling-return fans/coils, and demonstrated that the FDCU-return air system can effectively eliminate sub-micron particles from the cleanroom, compared with a conventional ceiling-supply and wall-return air system [1]. This study further investigated the effect of the heat dissipation from the tools on airflow characteristics and temperature distribution in the FDCU-return and wall-return airflow type cleanrooms. Comparisons of velocity vector, turbulence intensity, and temperature distribution between the FDCU-return air system and the conventional wall-return air system were presented. The results showed that the FDCU-return air system can significantly provide better air motion characteristics and temperature distribution in a high heat source case in comparison with the wall-return air system.     

Characterization of the household electricity consumption in the EU, potential energy savings and specific policy recommendations

Although significant improvements in energy efficiency have been achieved in home appliances and lighting, the electricity consumption in the European Union household has increased by 2% per year during the past 10 years. Some reasons are associated with an increased degree of basic comfort and level of amenities and with the widespread utilisation of new types of loads. Wishing to increase the understanding of the energy consumption in the EU households for the different types of equipment including the consumers’ behaviour and comfort levels, and to identify demand trends, an energy monitoring campaign, was carried out in 12 geographically representative EU countries, accompanied by a lifestyle survey. From the measurements carried out it was concluded that Information Technologies and entertainment loads are key contributors to the power demand. In basically all types of loads there is wide range of performance levels in the models available in the market. Available technology, associated with responsible consumer behaviour, can reduce wasteful consumption. Based on a bottom up approach the European residential sector potential electricity savings that can be implemented by existing technologies and improved behaviour can reach 48%. The paper presents policy recommendations promoting market transformation and behavioural changes in the equipment selection and operation.     

Assessment of energy efficiency in electric storage water heaters

Nowadays there are several ways of supplying hot water for showers in residential buildings. One of them is the use of electric storage water heaters (boilers). This equipment raises the water temperature in a reservoir (tank) using the heat generated by an electric resistance. The behavior of this equipment in Brazil is still a research object and there is not a standard in the country to regulate its efficiency. In this context, an experimental program was conducted aiming to collect power consumption data to evaluate its performance. The boilers underwent an operation cycle to simulate a usage condition aiming to collect parameters for calculating the efficiency. This 1-day cycle was composed of the following phases: hot water withdrawal, reheating and standby heat loss. The methods allowed the identification of different parameters concerning the boilers work, such as: standby heat loss in 24 h, hot water withdrawal rate, reheating time and energy efficiency. The average energy efficiency obtained was of 75%. The lowest efficiency was of 62% for boiler 2 and the highest was of 85% for boiler 9.     

Desiccant HVAC system driven by a micro-CHP: Experimental analysis

In the Mediterranean area, there is increase in demand for summer cooling satisfied by electrically driven units in domestic and small commercial sectors; this involves electric peak loads and black-outs. Consequently, there is an increasing interest in small scale polygeneration systems fuelled by natural gas.In this paper, attention is paid to a test facility, located in Southern Italy, to carry out experimental analysis on a small scale polygeneration system based on a natural gas-fired Micro-CHP and a desiccant HVAC system. The MCHP provides thermal power, recovered from engine cooling and exhaust gas, for the regeneration of the desiccant wheel and electric power for the chiller, the auxiliaries and the external units (computers, lights, etc.). The HVAC system can also operate in traditional way, by interacting with electric grid and gas-fired boiler. An overview of the main experimental results is shown, considering both the desiccant wheel and the global polygeneration system.The experimental results confirm that the performances of the desiccant wheel are strongly influenced by outdoor thermal-hygrometric air properties and regeneration temperature. The polygeneration system guarantees primary energy savings up to 21.2% and greenhouse-gas emissions reductions up to 38.6% with respect to conventional HVAC systems based on separate energy “production”.     

Data center design and location: Consequences for electricity use and greenhouse-gas emissions

The rapidly increasing electricity demand for data center operation has motivated efforts to better understand current data center energy use and to identify strategies that reduce the environmental impact of these buildings. This paper builds on previous data center energy modeling efforts by characterizing local climate and mechanical equipment differences among data centers and then evaluating their consequences for building energy use. Cities in the United States with significant data center activity are identified. Representative climate conditions for these cities are applied to data center energy models for several different prototypical space types. Results indicate that widespread, effective economizer use in data centers could reduce energy demand for data centers by about 20–25%, equivalent to an energy efficiency resource in the US of ∼13–17 billion kWh per year. Almost half of the potential savings would result from better airflow management and proper control sequences. The total energy savings potential of economizers, although substantial, is constrained by their limited potential for use in server closets and server rooms, which together are estimated to account for about 30% of all data center energy demand. Incorporating economizer use into the mechanical systems of larger data centers would increase the variation in energy efficiency among geographic regions, indicating that as data center buildings become more energy efficient, their locations will have an increasing effect on overall energy demand. Differences among regions become even more important when accounting for greenhouse-gas emissions. Future data center development could consider site location, along with efficiency measures, to limit the environmental impact attributable to this increasingly prominent economic sector.     

Improved control of the pressure in a cleanroom environment

In order to protect cleanrooms from contamination from adjacent less clean spaces, the cleanroom must be built air tight and maintain an (over) pressure of sufficient magnitude and deviation. For this magnitude there are guidelines. However, there is a lack of guidelines for the required deviation of the pressure. As a result, an unstable pressure could result in an undefined air direction and increase the risk of contamination. This unstable pressure occurs especially during entering the cleanroom with an air tight cleanroom. In this paper the pressure and the entrance of the cleanroom are modeled in the SimuLink modeling environment. The model is verified and validated. The main problem addressed here is that the air tightness and the deviation of the pressure are in conflict with each other. It is concluded that the new proposed adjustment decreases the deviation of the pressure in the cleanroom and enhances the precision of control.     

A new heat pump desiccant dehumidifier for supermarket application

Recently a new equipment for dehumidification was put onto the market. It is a self-regenerating liquid desiccant cooling system able to dehumidify, heating or cooling the ambient air by an electric heat pump that is a part of the equipment. Its operation is here studied in a supermarket application where air temperature and relative humidity play a very important role and the air-conditioning becomes necessary not only to assure a suitable thermal comfort, but also to make the refrigerated display cabinets operate properly. In this paper possible energy savings, compared to a traditional mechanical dehumidification, are evaluated by means of a numerical model that simulates a typical Italian supermarket.     

Experimental study of using PCM in brick constructive solutions for passive cooling

This work presents the results of an experimental set-up to test phase change materials with two typical construction materials (conventional and alveolar brick) for Mediterranean construction in real conditions. Several cubicles were constructed and their thermal performance throughout the time was measured. For each construction material, macroencapsulated PCM is added in one cubicle (RT-27 and SP-25 A8). The cubicles have a domestic heat pump as a cooling system and the energy consumption is registered to determine the energy savings achieved. The free-floating experiments show that the PCM can reduce the peak temperatures up to 1 °C and smooth out the daily fluctuations. Moreover, in summer 2008 the electrical energy consumption was reduced in the PCM cubicles about 15%. These energy savings resulted in a reduction of the CO₂ emissions about 1-1.5 kg/year/m².     

洁净室气密性检测方法研究——国标《洁净室施工及验收规范》编制组研讨系列课题之八

分析了在正、负压洁净室进行洁净室气密性验证的重要性,对洁净室气密性相关问题进行了理论计算,给出了具体检测方法,并进行了实验研究.结果表明,一个密封很好的洁净室,500 Pa压力的半衰期不足5 min,小时泄漏率不到10%.     

Two smart energy management models for the Spanish electricity system

This paper evaluates two smart energy management models for the Spanish electricity system in terms of power consumption savings, CO₂ emissions, and dependence upon primary energy from abroad. We compare a baseline scenario with two alternatives. The first model entails the reduction of the power demand through energy savings measures, smart meters, and self-supply. The second model entails the application of all measures included in first scenario, plus measures oriented to electric vehicles. For each model a sensitivity analysis was performed. Results show that both models can result in reductions of peak loads, CO₂ emissions, and energy dependence.