INTRODUCTION TO COMBINED HEAT & POWER (CHP), ENERGY EFFICIENCY AND SUSTAINABLE BUILDING TECHNOLGY
Combined Heat and Power
CHP or cogeneration is the simultaneous or sequential energy production of usable heat and power (usually electricity) in a single process from a common source of energy. Useful energy outputs can be more varied. Increasingly, heat is being used to drive absorption chilling, and in some cases power can be mechanical power e.g. to drive a compressor. The term CHP is synonymous with cogeneration and total energy, which are terms often used in other Member States of the European Community and in the United States. CHP uses a variety of fuels and technologies across a wide range of sites, and scheme sizes. The basic elements of a CHP plant comprise one or more prime movers (a reciprocating engine, gas turbine, or steam turbine) driving electrical generators, or other machinery, where the steam or hot water generated in the process is utilised via suitable heat recovery equipment for use either in industrial processes, or in community heating and space heating.
Whereas an electricity-only plant is typically large, and connected at very high voltage to the grid transmission system, a CHP plant is typically much smaller, attached to a site which consumes the heat and power produced (or a large proportion of it), is sized to make use of the available heat, and connected to the lower voltage distribution system (i.e. embedded). Not only is CHP more efficient through utilisation of heat, it also avoids significant transmission and distribution losses, and can provide important network services such as black start, improvements to power quality, and the ability to continue to supply the site if the grid goes down.
CHP usually displaces boiler plant and electricity only plant using a range of fuels and technologies. CHP typically achieves a 25 to 35 per cent reduction in primary energy usage compared with electricity-only generation and heat-only boilers. This can allow the host organisation to make substantial savings in costs and emissions where there is a suitable heat load.
CHP power plants can be divided into five types: backpressure, extraction condensing, gas turbine heat recovery, combined cycle and reciprocating engine power plants.
Backpressure power plant
The simplest cogeneration power plant is the so-called backpressure power plant, where CHP electricity and heat is generated in a steam turbine. Another main component of the backpressure power plant is the steam boiler, which can be designed to fire solid, liquid or gaseous fuels.
Extraction condensing power plant
A condensing power plant is generating only electricity. However, in an extraction condensing power plant some part of the steam is extracted from the turbine to generate also heat.
Gas turbine heat recovery boiler power plants
In gas turbine heat recovery boiler power plants heat is generated with hot flue gases of the turbine. The fuel used in most cases is natural gas, oil, or a combination of these. Gas turbines can even be fired with gasified solid or liquid fuels.
Combined cycle power plants
Recently, natural gas fired combined cycle power plants consisting of one or more gas turbines, heat recovery boilers, and a steam turbine have become quite common.
Reciprocating engine power plant
Instead of a gas turbine, a reciprocating engine, such as a diesel engine, can be combined with a heat recovery boiler, which in some applications supplies steam to a steam turbine to generate both electricity and heat.
Advantages of CHP include:
- Potential energy savings
- Security of supply
- Cost-effectiveness
- Increases competition among producers
- Opportunity to create new enterprises
- Well-suited to isolated or ultraperipheral areas.
Euroheat & Power Project of the EU indicates that huge heat losses appear in the EU energy balance. From the annual energy supply of 63 EJ, more than 20 EJ heat are lost in power plants, oil refineries, and industrial processes. Parts of these losses can be retrieved and distributed by district heating systems to heat urban buildings. District heating systems provide the necessary heat load for high-efficiency CHP plants and, at the same time, make it also possible to use renewable energy sources (RES). District cooling is emerging as a similar energy efficient tool for providing comfortable indoor climate during summers.
Sustainable Building Technology
The environmental problems arising from the industrial revolution and the population explosion of the last century resulted in a new era of environmental laws internationally. The international treaties addressed environmental concerns about ocean dumping, air pollution, endangered species, etc. Governmental and industrial leaders around the world have begun to consider a holistic way of protecting the environment, which is known as sustainable development. Recognizing that a holistic approach would require new levels of international collaboration on environmental issues, the United Nations hosted an Earth Summit in June 1992 in Rio de Janiero, Brazil. The Earth Summit attracted nearly all of the governments of the world, more than 100 of which were represented by their heads of state, and resulted in two landmark conventions on climate change and biodiversity. The 1992 summit also established sustainability as a goal leaders worldwide supported and agreed to work toward achieving.
While renewable sources of power, like solar and wind, hold promise for producing energy with fewer environmental impacts, the ability of those power sources to contribute significantly to meeting our energy needs affordably is likely many years away. In the meantime, efficiently using energy in buildings through careful design and choice of building materials could go a long way to minimizing the environmental damage attributable to energy production.
In addition to the land required to dispose of building-related construction and demolition debris generated, the amount of natural resources that are mined and harvested to supply building materials are considerable.
Sustainable approaches to building and the industries can both improve productivity and open up new business opportunities by enabling better use of the earth's 'natural capital' natural resources and ecological systems that provide vital life-support services to society and all living things. There are many features of a building that contribute to its sustainability, and the products used in the building are key features. Other features influencing sustainability include the overall efficiency of the building, the impact the building has on both the habits of the occupants and the microclimate. Green building concept has created more widespread awareness of the challenges involved in using alternative materials and methods of construction, including earthen building technologies.
The European Commission's document on sustainable development An European Union Strategy for Sustainable Development provides for support research activities related to sustainable development as a part of the European Research Area; guidance document for Member States to consider how to make better use of public procurement to favour environmentally-friendly products and services and encourage private sector initiatives to incorporate environmental factors in their purchasing specifications.
ASTM International Standards on SUSTAINABILITY in BUILDING meets the worldwide growing demand for sustainable building standards and address environmental problems & challenges related to the design, construction, and operation of environmentally-sound and resource-efficient sustainable buildings.
Standards cover:
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Site & Ecosystems land management, biodiversity impacts, and ecosystem functioning
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Water water efficiency and water quality impacts
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Energy energy efficiency, renewable energy, and atmospheric impacts
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Materials recycled contents, nontoxic and biobased products
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Indoor Environmental Quality indoor air quality, acoustics, and lighting
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Operations durability, waste management, maintenance, quality of life (QOL), and life cycle assessment (LCA).
Energy efficiency
Energy efficiency of a building envelop or a machinery equipment or a process for producing energy means the ratio of useful energy to actual input energy for heating, cooling, and lighting or process. Energy efficiency implies that:
- all the components of the building envelope including the doors, windows, walls, foundation, roof, and insulation need to work together to keep a building warm in the winter and cool in the summer.
- energy saving appliances and equipment should be used in buildings.
- renewable energy systems should employ energy efficient components.
- as the most of the renewable energy sources are of intermittent nature, efficient energy storage technologies need to be employed.
Improving energy efficiency of a building envelop, machinery or equipment, both by reducing quantities of energy consumed and by changing processes, offers a promising method for sustainable development by reducing the investments in energy infrastructure, by cutting fuel costs. It will create environmental benefits through reduced emissions of greenhouse gases and local air pollutants.
European Union's Green Paper on energy efficiency or doing more with less includes the energy policy measures and highlights that even without high and volatile oil prices, which have led to a downgrading of the prospects of economic growth in Europe, there would be very good reasons for the European Union to make a strong push towards a re-invigorated programme promoting energy efficiency at all levels of European society
The United States and Japan have already taken initiatives to reach a maximum consumption figure of one watt for several types of appliance. In Europe, and still in the context of the eco-design directive, it is foreseen to:
In India, TERI (The Energy and Resources Institute), is actively involved in development, demonstration, and propagation of products based on renewable and clean energy technologies. As an Associate of OPET [a network of Organisations for the Promotion of (clean and efficient) Energy Technologies], TERI carries out activities related to dissemination of EU RTD Framework programmes, and promotion of new and innovative energy technologies, in close collaboration with European OPET Members. Potential of CHP in Indian industries has been assesed in the OPET report, which indicates that to-date CHP in India has been restricted to the production of electrical energy for self-use or captive power and has been viewed as a way to meet simultaneous on-site heat and power demands independently of the grid. Industries such as sugar, pulp and paper, and textiles have been cogenerating electricity and steam for many years.
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