电气专业英文文

71Introduction to Intelligent BuildingsT.Nikolaou, D. Kolokotsa, G.StavrakakisINTELLIGENT BUILDINGS: THE GLOBAL FRAMEWORK Sustainability is a term that has become an integral part of our vocabulary. By this word we understand the protection of the ecosystem through protection of its resources. The economic sustainability of buildings can be divided into two parts: the investment, which in the case of buildings and buildings stocks should be considered as long term resource productivity problem, and the running costs. Instead of minimizing the investment cost through low cost highly customized solutions, it is preferable to find for a given investment the solution which has the highest durability and reusability. Solutions which can be repaired and used in several ways have the highest long term potential. On the other hand, solutions with low energy consumption, easy to clean, to operate and easy to maintain have generally low running costs (and a feasibly low environmental impact at the same time).The social and cultural aspects of sustainability include comfort, wellbeing and safety of the building occupants. Human health protection, which is often wrongly associated with protection of the ecosystem, is in fact much more closely related to comfort problems (indoor air quality, etc.). The protection of cultural resources, above all building stocks and historic urban systems, protected biotopes and man-made landscapes gives a common framework for architecture, city planning, regional planning and landscape architecture. Environments which have a high cultural and social quality do not become obsolete.During its life cycle, which can vary from some months to hundreds of years, a building consumes resources from nature, produces large quantities of emissions and affects the ecosystem in many different ways. In addition to the general objective of maximizing the quality of a building, the design process should also aim at minimizing the resource consumption and the emissions due to the construction, operation, maintenance, refurbishment and disposal process. One of the possible actions is to maximize the closed loops, i.e. the reuse or recycling of building elements and materials, heat recovery and the multiple use of water. To reduce the environmental impact means to reduce the mass and energy flows and raise at the same time the overall quality of a building. It does not mean to reduce the comfort level or the indoor quality.The most important factor that threatens the sustainability of the planetary ecosystem as we know it, is the accumulation in the atmosphere of the 'greenhouse gases'. This is causing the planet to warm, and is producing climate changes that may be irreversible. These climate changes are already occurring at a rate, which exceeds the adaptive capacity of some of the earth's bio systems [1].The most important greenhouse gas is carbon dioxide, and the increase in its concentration is mainly because of the quantities which are being discharged into the atmosphere due to the burning of fossil fuels.The mechanism of the global warming effect is described briefly (see Figure 1.1.). Carbon dioxide produced when fossil fuels are burned, but also methane, nitrous oxide, ozone, and chlorofluorocarbons, has created what scientists call a greenhouse effect in the atmosphere. While the solar radiation reaches the earth, one third of it is reflected back into space and the remainder is absorbed by the earth and the atmosphere. Some of the long-wave infrared radiation emitted back from the earth is returned to the earth by the greenhouse gases. Like the glass in a greenhouse, greenhouse gases let in the sun's rays, but trap heat radiated back by the earth. This causes warming of the planet. The solar energy absorbed by natural features is balanced by the energy re-radiated from the earth and atmosphere. Without this greenhouse canopy, the earth would be up to 30 C cooler. Figure 1.1. The Greenhouse MechanismAtmospheric carbon dioxide levels were never rising above 280 parts per million until the recent decades. Today, carbon dioxide levels are 25-28 percent higher than they were before the Industrial Revolution, and still rising. Atmospheric CO2 levels are 365 parts per million, and projected to double in the coming decades. Man-made sources of carbon dioxide (fossil fuel emissions and the clearing of forests) are responsible for this increase. Roughly five billion tons of carbon in the form of CO2 (one ton per human being) is released into the air every year by the burning of oil, gas, and coal.The Inter-governmental Panel on Climate Change (IPCC) reported a prediction of the global temperature rise due to greenhouse gas emissions. According to IPCC report a doubling of the concentration of carbon dioxide in the atmosphere compared to pre-industrial levels would lead to an average global temperature rise of as much as 4.5 °C. Predictions regarding the impact of global warming are bound to be fuzzy. Nevertheless, certain outcomes, the most critical being the rise in sea level due to the melting of land based ice and the thermal expansion of sea water are certain.The fossil fuels, namely petroleum, natural gas and coal are the energy sources on which the European energy infrastructure is based. The energy use can be divided into three end use segments:TransportationResidential and commercial buildingsIndustryEach of these sectors consumes about one-third of the total energy use. More specifically the total final energy consumption in the EU in 1997 was about 930 Mtoe. A simplifiedbreakdown of this demand shows the importance of buildings in this context: 40.7% of total energy demand is used in the residential and tertiary sectors, most of it for building-related energy services. It should also be pointed out that approximately 10% of the consumed energy in buildings comes from renewable energy sources (RES). Space heating is by far the largest energy end-use of households in Member States (57%), followed by water heating (25%). Electrical appliances and lighting make up 11% of the sector’s total energy consumption (Figure 1.2.). For the tertiary sector (Figure 1.3) the importance of space heating is somewhat lower (52% of total consumption of the sector), while energy consumption for lighting and "other" (which is mainly office equipment) are 14% and 16%, respectively.On the other hand, there is increasing international concern with climate change, and the targets agreed by the European Union under the Kyoto Protocol to reduce emissions of greenhouse gases in 2010 by 8% compared to 1990 levels represent a real challenge. In the Green Paper three major points emerged concerning the European Union and its energy strategic issues [4]:The European Union will become increasingly dependent on external energy sources; enlargement will not change the situation; based on current forecasts, EU energy dependence will reach 70% in 2030.The European Union has very limited scope to influence energy supply conditions; it is essentially on the demand side that the EU can intervene, mainly by promoting energy saving in buildings and the transport sector.At present, the European Union is not in a position to respond to the challenge of climate change and to meet its commitments, notably under the Kyoto Protocol.Figure 1.2. Energy consumption by end use in EU residential buildingsINTRODUCTION TO INTELLIGENT BUILDINGS 10 Figure 1.3. Energy consumption by end use in EU tertiary buildingsEnergy use in commercial buildings represents a direct cost to business, while the thermal comfort, visual comfort and indoor air quality of the indoor environment have a substantial bearing on occupants’ productivity [5]. It is more than obvious that improved energy efficiency and reduction of energy cost can have beneficial impacts on the competitiveness, the environment, the health and the well being of European citizens. The benefits of installing BEMS are therefore direct and indirect as well as micro-economic and macro-economic. Apart from the obvious environmental benefits, other improvements also occur as a result of BEMS installations.Fire control is an obvious example and it is expected that the total integration concept will become popular. This implies a single central host computer serving the fire alarm system as well as the other building systems. The fire alarm control panels and the Application Specific Controllers (ASCs) communicate with the Operator Workstations (OWSs) over separate communication buses. A merit here is that, if a fire occurs on one floor of a multi-storey building, the HVAC units can be used to prevent the smoke from spreading by opening exhaust dampers and closing outdoor air intake dampers of the fire floor.The integration of security and access control and other building services systems into a BEMS can also provide both economic and operational benefits. First, initial installation work, such as electric wiring can be consolidated, resulting in cost savings. Substantial paybacks can be generated through HVAC energy management and lighting programs, thereby offsetting some of the costs involved in the integration process. Secondly, the cost of on-site guard services can be greatly reduced.The BEMS can also be a tool to assist facility management and operating personnel of a building. The computerised maintenance management programs provide facility management personnel with tools needed to protect equipment, control costs, schedule workloads, review historical trends, manage materials and plan budgets. Maintenance scheduling includes work order printout, maintenance history, material inventory, financial analysis and management information, etc. The utilities metering program provides the means to dynamically monitor and record a facility's energy consumption on a real-time basis while a tenant energy monitoring program is also available. The heating/cooling plant efficiency program can continuously monitor the efficiency of the central HVAC plants because a small decrease in operating efficiency of these large central systems can result in a significant increase in energy consumption and its associated costs.INTRODUCTION TO INTELLIGENT BUILDINGS 11OVERVIEW OF INTELLIGENT BUILDINGSDefinition of Intelligent BuildingsThe recent energy crises, the realization that energy resources are not inexhaustible and the general trend towards a cleaner environment have led to the development of many practices that aim at using energy as "optimally" as possible. In the building sector this has materialised in the form of "Building Energy Management Systems" (BEMS). Broadly speaking, BEMS refers to a computerised system that attempts to "control" all the energy consuming operations in a building. These may include heating and ventilation, lighting, indoor climate and others. Depending on the level of sophistication these operations may be controlled independently or not. In this way it is expected that the subtle interrelations between the various parameters are taken into account, resulting in "optimum" operation.Nowadays, the term "smart" or "intelligent building" is gaining popularity and this concept generated a good deal of market anticipation during the last decade, much of which subsequently dissipated once the limits and complexities of building intelligence were discovered. Though intelligence is an ambiguous term, especially when applied to man-made systems, it is widely accepted that it refers to objects that can react correctly to unforeseen circumstances by choosing amongst a set of possible actions and furthermore, can learn from the associated response. The concepts of self-correction or fault tolerance are considered as essential elements of "artificial intelligence". It is also widely accepted that the means to achieve intelligence consist of tools that resemble human intelligence methods, such as neural networks and fuzzy logic.Intelligent Building technology generally refers to the integration of four systems: a Building Automation System (BAS), a Telecommunications System (TS), an Office Automation System (OAS) and a Computer Aided Facility Management System (CAFMS). A sophisticated BAS is actually the basis of every "intelligent building". BEMS originated in the USA in the ear ly 1970’s. They initially consisted of dumb outstations, which collected data and fed them to a central station. The central station was the only part of the system with some ‘intelligence’. BEMS from the early 1980s are now considered cumbersome compared with today's systems. The next development was the introduction of the intelligent outstation, which resulted from the development of the low-cost PC.A typical centralized commercial BEMS consists of the central station and a number of outstations. The outstation accepts inputs from sensors monitoring the values of variables, such as flow and return temperatures of a heating system. Then the inputs are processed and the outstation sends output signals to control items of a plant, i.e. actuators or a valve. The outstation contains a small circuit board, the communication board, which allows it to interface with the central station usually Local Area Network (LAN), sub-LANS or a modem. The central station is where most of the long-term data storage takes place.Historical OverviewThere was a general expansion in the construction industry after World War II. A desire to improve comfort inside new, larger buildings resulted in more complex mechanical systems. The impact of this was the development of better heating and cooling control systems. The large size of buildings was one of the major forces behind the concept of centralization.。