To Zero Carbon and Beyond - Essay Example

1. Introduction: Global warming due to the increased concentration of greenhouse gases in the atmosphere because of fossil fuel (coal, gas and oil) burning is a scientifically proved phenomenon. Carbon dioxide (CO2) is a greenhouse gas mainly comes from fossil fuel burning. United Kingdom (UK) has published its draft climate change bill in March 2007. The bill aims at reducing UK's carbon dioxide emission by 60% by the year 2050 and 26-32 % by the year 2020 to comply with its commitment to Kyoto Protocol (Draft Climate Change Bill will put carbon reductions on a legal footing, 2007). European Commission intends to reduce its greenhouse gas emission by at least 20 % by 2020 (Integrated energy policy for EU sets targets on markets, emissions and efficiency, 2007). In the UK buildings accounts for 45-50% of delivered energy use and it accounts for about 50% of CO2 emission. UK's contribution to global total CO2 is 3%. Almost 30% of building related CO2 in the UK comes from service sector and 44% of it goes to space heating (Watts and Thomas, 1999). In November 2006, Chancellor Gordon Brown has announced that by 2016 every new home will be a zero carbon home (Towards zero carbon future, 2007). A zero carbon development is one that achieves zero net carbon emissions from energy use on site, on an annual basis. Excluded in this definition are embodied energy in construction and demolition and transport energy (Building A Greener Future: Towards Zero Carbon Development, 2007). Literary the meaning of zero carbon home should be a home which emits zero carbon throughout its life time, (i.e. construction, operation, maintenance and demolition). It is very important in the UK's context to design energy efficient buildings, which can utilize maximum heat and light from the sun. This paper will describe the design aspects of an office building, which will emit zero carbon throughout its lifetime (operating). It will discuss site selection of the office, transport system, use of sun as a source of light, heat and energy, selection of energy efficient materials, recycling of grey water and solid waste management. 2. Site selection for the office: The office has to be located near public transport, access to road and other facilities (water supply, gas and electricity) should be close to the office location. Brownfield sites may be classified as abandoned, idle, or under-used industrial and commercial facilities where expansion or redevelopment is complicated by environmental contaminations. They can be found in urban areas, particularly near highways, railroads and low income areas of a city.The Brownfield site has advantages of ease of transport, pollution can be reduced by using more public transport and infrastructural facilities like water, gas electricity normally exist. The brown field may be contaminated and need money to clean it up with the help of environmental consultants (Brown Field vs. Greenfield, 2007). A Greenfield is any piece of land where there had not been any previous type of development on site. Greenfield sites are almost always found in suburban or rural areas. Normally undeveloped farmlands and woodlands fall in this category.It offers opportunity to build bigger offices, with parking areas and lower cost (water, energy, construction labor, and waste disposal generally cost less). But it occupies virgin land which could be used for agriculture, pasture or plantation (Brown Field vs. Greenfield, 2007). So, for constructing the new office building a Brownfield site selection will be more environmentally friendly. Because it will clean up already contaminated land and make it usable. Moreover by choosing Brownfield land we are saving virgin land which can be used for agriculture, pasture or plantation. So, we decide to locate our office in a Brownfield. 3. Transport infrastructure: The office employees will be encouraged to use public transport, because they are more environmental friendly. There will be other transports to carry things to and from the office. These transports can use biofuel as fuel. As biofuel is made from plant or seed, they are renewable and produce less carbon dioxide than fossil fuel. Moreover, biofuel is carbon neutral, because it emits CO2 which it has sequestered during its growth. It also can be carbon positive if it uses a lot of energy in the form of fertilizer and water. There is also debate going on about the environmental concern of growing plant for fuel. Some argue that it will cause loss of biodiversity, increase soil erosion and destroy natural forest. While others say that all the environmental effects can be minimized and it can be grown sustainably. So, all depends on how it is being grown and managed. Under Renewable Transport Fuel Obligation (RTFO), the transport fuel suppliers in the UK require that by 2010, 5% of all road vehicle fuel supplied from renewable, non-fossil sources. Biodisel or biofuel are mainly made from sugar cane, straw, jatropha curcus. maize, sorghum, miscanthus (Delivering Sustainable Biofuel, 2007). So, if the office transports use biofuel, it will also contribute to fulfilling the government's aim. Car can be also powered by electricity from the roof mounted photovoltaic installation, but this option may be expensive. 4. Maximum utilization of sunlight for lighting: Daylight is a gift of nature which is free and abundant. United Kingdom has a potential of exploiting daylight from 0.7 to 1.3 mtce (Million tones of coal equivalent) by 2020. In the UK domestic lighting accounts for only 2 % of total delivered energy use. But in case of offices and commercial places it can be as high as 30% (Everett, 1996). Lighting consumes 40% of total energy in the European Union (Hunt, 2007). This can be reduced by using more sunlight for lighting purpose. This will save electrical energy and money at the same time contribute to the reduction in greenhouse gas emission, if electricity is generated from fossil fuel. So, it is crucial to design buildings which can use daylight efficiently for lighting purpose and save energy. 4.1 Concept of Daylight Factor: Daylight factor can be defined as the ratio of the indoor illuminance to outdoor illuminance under an unobstructed overcast sky. Daylight factor is expresses as percentage (Lynes, 1992). The average daylight factor can be calculated by using the following equation (Lynes, 1992). df = (TWM)/ A(1- R2). 1 Where T = diffuse transmittance of glazing material (for clear single glazing = 0.85, double glazing = 0.75). W = net area of window = angle subtended in the vertical plane by sky visible from centroid of window. A = Total area of interior wall surfaces: floor, ceiling and walls (including windows). R = area weighted average reflectance of indoor surfaces (fairly light = 0.6 and fairly dark = 0.4). M = maintenance factor to allow for dirt and deterioration If the average daylight factor exceeds 5% the interior will look daylited. But if it drops below 2%, use of artificial light will be essential (Lynes, 1992 and Rennie and Parand, 1998). By using the concept of daylight factor engineers can design buildings which will maximize the use of daylight for lighting. As we can see from equation 1 the daylight factor can be increased by increasing the transmittance of glazing material, net area of window, angle of visible sky from the centre of the window, the reflectance of indoor surfaces, keeping the window glasses clean and by reducing the total interior surface area. So, to improve the quality and quantity of daylight in the office the following steps can be taken: Use clear single glazing instead of double glazing in the windows. Increase the window area so that W/A is large. Keep the window clean. Design and place the window such that the visible sky angle is large. Vertical windows from working plane to ceiling will allow maximum light penetration and good views (Rennie and Parand, 1998). Paint the interior walls and ceiling with a light colour to maximize their reflectance. Use materials with high reflectance in the floor. Moreover, the skylight is the combination of direct light, external reflections and internal reflections. External reflection can be increased by using mirrors (Rennie and Parand, 1998). By changing the sitting arrangement the quality of light can be improved, i.e. setting working table perpendicular to the windows facing south walls, the visibility will be better. 4.2 Use of energy saving lights and control mechanisms to reduce electricity consumption: Now a days many types of energy saving lights are available in the market. Energy saving light bulbs uses a quarter of the electricity of ordinary bulbs to generate the same amount of light as can be seen from the table-1 below (Light bulbs and fittings, 2007). Table 1: Comparison of energy saving bulbs with ordinary bulbs (a 6 W energy saving bulb will give same amount of luminance as a 25 W ordinary bulb) Ordinary bulbs Energy saving equivalent 25W 6W 40W 8 - 11W 60W 13- 18W 100W 20- 25W Low energy fittings use a ballast or transformer fitted into the base of the light fitting. It controls the supply of electricity to the bulb, allowing for a small surge of power for a millisecond to light the bulb and then reducing the electricity flow to a very low level (Light bulbs and fittings, 2007). Linear fluorescent tubes or low pressure discharge lamp with high frequency (HF) electronic blast can be used in the office. The modern 16mm diameter T5 model with 105 lm/W is more efficient than the old 26 mm T8 model with 96 lm/W. T 5 lamps are shorter also and can be easily incorporated into luminaries for 600, 1200 and 1500 mm ceiling modules (Hunt, 2007). So, T5 linear fluorescent tube with 16 mm diameter with HF electronic blast and 600 mm luminaries will be used in the rooms of the office. As the toilets are used intermittently and abundant light is not required, one 8 watt energy saving florescent light will be sufficient for each of the toilets. In the corridors, kitchen and store room (s) same 8 watt energy saving florescent light can be used. To minimize the electricity consumption all office staffs and visitors should be made aware of switching the lights off after use. But as people are not aware and normally forget to switch the lights off, automatic control system will be useful. Artificial lighting controls can be linked to natural light levels to minimize energy demand. Lighting can be controlled by automatic or semi-automatic control system. These can be time switches operating to a preset schedule, photoelectric switches reacting to daylight conditions, and the occupancy -linked controls sensing the presence of user (United Nations, 1991). Photoelectric switch will be used in the rooms of the office, which will automatically turn on the light when the sunlight is insufficient. For the toilets, occupancy linked control system can be used which will turn on the switch when somebody is in the toilet and turn the switch off when he/she leaves. Task lighting can be used directly over the work place, rather than lighting the whole room. 5. Heating and ventilation: Over 25% of UK primary energy production goes towards heating buildings. By incorporating passive solar design into new buildings, annual fuel bills can be reduced by about a third and thus reduce CO2 emission. Passive solar design optimises the amount of energy that can be derived directly from the sun, by planning of buildings to collect the sun's heat, thus reducing the need for space heating. Passive solar houses are designed to let heat into the building during the winter months and block out the sun during hot summer days. This can be achieved using deciduous trees or bushes to the south of the buildings. During the summer, the leaves of the trees block a lot of the sunshine. During winter, the trees lose their leaves, allowing an increase in the solar gain during the colder days. Louvers, shutters or blinds can be used in the windows to block out sun when it is high in the sky and during summer while allowing it in during the winter when it is lower in the sky. Passive solar designs can also include natural ventilation for cooling with windows playing a large part. Large south facing windows will allow sunlight to come inside the rooms, the building materials (walls, roof, floor and insulators) absorb solar heat during their exposure to direct sunlight and radiates that heat back into the space during the cooler night. During the summer, the reverse occurs. The thermal mass is prevented from receiving direct sunlight (by blinds, louvers or shutters) and absorbs the heat in the room, helping to keep the room's temperature cooler. Most design consideration can be made and implemented using standard building materials and basic construction skills. This can reduce the electricity consumption by 40% annually, and also improve the comfort of living spaces (Passive Solar Design, 2007). To get maximum gain by passive design for the proposed office, following steps should be taken: 1. Maximum number of tall windows in the south walls with no obstruction from tall buildings or evergreen trees. 2. Thermally massive design and good insulation to absorb and retain heat (masonry, steel and concert for structure and mineral fibre for insulation). 3. Main occupation rooms in the south side of the building 4. Use of shading devices (blinds, louvers etc) to avoid overheating during summer. 5. Rooms not more than 2.5 times the window head height. 6. Single glazed windows (although double glazing is better for heat gain, but it reduces the amount of sunlight). The building will be naturally ventilated from one side. There will be provision of opening the windows during summer. In addition to passive design, heat pumps will be used in the office to supply hot water and additional space heating during winter. The heat pumps will get energy from the solar photovoltaic electricity. Heat pumps work in the same principle of refrigerator, but instead of cooling it gives heat. Heat pumps can give heat energy output 2-3 times electrical energy needed by the compressor (Everett 1996). A new type of heat pump has been manufactured by Yorkshire based Heatking. It is a ventilation heat pump fitted in the external wall with heater in each room with temperature control. The heat pump uses an electrically driven compressor to extract low grade heat from ambient air and generate hot water, which can be circulated by insulated pipe work. Electricity use can be reduced by around 60% compared with the conventional electric heater (Air heat pumps come to North East, 2007). So, use of heat pump in the office building for hot water and space heating will save energy. 6. Orientation of the building: South facing building with lots of windows will allow both light and heat (Everett, 1996). Most occupied rooms of the office buildings should be located in this area. Rooms for staffs, meeting room, conference hall etc. should be located here. Least used rooms like toilet, store, kitchen and cafeteria should be located in the Northern side of the building. 7. Use of construction materials: Most of the construction materials for building like steel, bricks, cement and glasses are energy intensive. They have huge amount of embodied energy. They consume a lot of energy during different stages of their production processes starting from mining to finished product. As Thomas (1999) six has defined embodied energy as energy used to (a) win raw materials (b) convert them to construction materials, products or components (c) transport the raw materials, intermediate and the final products and (d) build them into structures. Amount of embodied energy can be calculated by performing detailed life cycle analysis of a product. In the UK approximately 5-6 % of total energy consumption is embodied in construction materials, this is not very high if we compare it to about 50% of total energy consumption for space heating, cooking, water heating, lighting and power. In case of new office building, the embodied energy ranges from 3.5 to 7.5 GJ/m2 of floor area whereas the energy consumption is 0.5 to 2.2 GJ/m2 yr. In an office building embodied energy is about 7% of the total energy used in the lifetime of the building Thomas (1999). Embodied energy of some construction materials are listed in Thomas (1999). Embodied energy sequence of some of the construction materials are: concrete> plasterboard>concrete blocks> bricks> mortar> copper> softwood> paint> chipboard floor> steel> glass. Some materials produced from the recycled materials will have less embodied energy than the materials produced from virgin materials. Noise transmission, fire consideration, structural span, insulating properties of the materials are also important aspects to consider before choosing a material for construction. Lightweight concrete block wall required 1.7 times embodied energy than timber framed wall Thomas (1999). In our case the structure of the building should be build with structural masonry, steel frame and concrete floor. Foundation of the building should be made of bricks/stone, steel, cement and sand. During procuring the materials steel produced from recycled ones can be procured. Moreover, the source of energy used during production process can be taken into consideration. Materials produced by using renewable energy sources will be more environmentally friendly than the others. The floor can be made of wood rather than concrete, because it has less amount of embodied energy. External walls can be made of solid concrete blocks, because it needs less energy than solid brickworks. Pitched timber and tile roof will be suitable in terms of embodied energy compared to steel frame. The cavity between the external and internal wall should be filled with insulating materials. When choosing insulating materials their environmental performances should be carefully examined. Such as plastic insulators may use CFCs and HCFCs, glass and mineral fibre can cause cancer and bronchitis. Mineral fibres require less embodied energy and releases less CO2, so we can use it for our office (Thomas, 1999). In the building cables for electricity, pipes for water supply should be carefully selected so that they are environmentally friendly and use less amount of embodied energy. Plastic pipes and ductwork can be used instead of copper or steel as they have less embodied energy. Although wood is more environmentally friendly than other construction materials (it is also renewable), but care should be taken whether it is coming from rain forest, or causing habitat destruction or any environmental problem in the original location (Thomas, 1999). 8. Source of renewable energy: The electrical energy requirement for the office can be generated onsite by either installing Solar Panels on the rooftop or by establishing windmills or by installing a biomass gasification plant nearby (with generator to generate electricity). Wind mill in the urban area can cause aesthetic problem and noise pollution. Moreover, it depends on the wind velocity and amount of generated electricity varies. Biomass is clean in that it emits carbon dioxide equal to what it has sequestered during its growth. It also can be carbon positive or negative depending on how it was grown and how it is being burnt. If it were grown with lots of fertilizer and energy input it is carbon positive, on the other hand if it can be burnt with CO2 capture technology, it will become carbon negative http://www.science.org.au/nova/039/039box01.htm,). For proposed office purpose it will not also be feasible because wood is a low density fuel and mass amount will be needed. If the source of biomass is far way, it will again consume energy for transportation. As most of the activities of an office take place at daytime, solar photovoltaic is the best option for the office. With solar panel mounted in the roof, batteries will be kept as standby for cloudy or rainy days and night time purpose. The electricity obtained from this solar panel will be used to run the electric appliances, to run the heat pump for hot water and space heating and to light when sunlight is insufficient or falls below visible limit. The disadvantages of photovoltaic power is high cost and intermittency. For office purpose it will work. The excess amount of generated electricity will be sold to the national grid. Tax exemption or other type of government incentive can be received for producing own electricity. Unfortunately in the PV array there will be some embodied energy, which is unavoidable. 9. Overall energy conservation: By changing habit of the employees energy and materials can be saved. Like switching of light, computer, room heater and tap after use. Electrical appliances with low energy consumption should be procured for the office (refrigerator, computer, printer, photocopier and oven) so that their operating cost (electricity consumption) is low. Moreover the environmental performance of these appliances should be carefully considered (whether they contain any chemical or substance harmful to the environment) before purchasing. 10. Recycling of grey water and water conservation: In the office, the sources of grey water can be the wash basins in the toilet, the kitchen basins and wash basins in the cafeteria or dinning area. The water from all these sources can be collected in a tank and kept it for some hours (8-10) to settle the settleable materials. At the same time organic materials will be removed by microbial activities. This water can be recycled and used to flash the toilets and for irrigating garden. Other measures can be taken to conserve or save water such as by using once through taps in the wash basins, by using low volume flash in the toilet. Rain water can be collected from the roof top through duct into a tank. After first shower, the rain water become clean and can be used for washing and cooking and other purposes except drinking. Office staffs should be make aware of conservation of water. In the basin a slogan may be written, "every drop counts". 11. Solid waste management: In the office solid waste generation should be kept minimum as far as possible. All the recyclable materials should be kept separate and send them in the corresponding recycle bins. Polythene bags and plastic bottles can be reused several times before throwing them into the bins. Use of paper can be reduced by sending notice, minutes and making all the correspondence electronically. Drafts can be read and corrected on the computer screen without taking a print. Both sides of paper can be used for printing and photocopying. Recycled paper can be used for all purposed in the office. 12. Conclusions: Energy efficient building design is a must because of the concern about global warming and conservation of energy. United Kingdom has set a target to make all their homes zero carbon homes by 2016. But it does not include the embodied energy in the building materials, furniture, electrical and electronic appliances and other things used at home; it only considers the energy needed for lighting, space heating, hot water, cooling and power needed at home for other purposes. But it is a good initiative and achievable by the participation and cooperation of all concern. If individual household can generate and meet their own energy demand from any of the renewable energy sources, that will reduce a considerable amount of CO2 emission. Then government can put emphasis on the embodied energy in the materials. Electricity generation by renewable energy sources is also increasing day by day in many countries. Renewable energy will be cost competitive in course of time, with continuous research and development efforts and replace the fossil fuel. Materials produced by renewable energy will be carbon free. Then we will be able to call our homes zero carbon homes in true sense. This paper has discussed various design aspects of a new office building, which will use less energy and emit zero carbon during its lifetime. References Air heat pumps come to North East, (2007) Energy World, March 2007, published by energy Institute, UK. Brown Field vs. Greenfield, (2007) available at http://www.continuitycentral.com/feature0179.htm, accessed on 02-05-07. Building A Greener Future: Towards Zero Carbon Development, (2007) Comments by the Royal Institute of British Architects, available at www.riba.org/fileLibrary/pdf/RIBA_response_to_building_a_greener_future_070307.pdf - accessed on 02-05-07. Draft Climate Change Bill will put carbon reductions on a legal footing, (2007) Energy World, March 2007, published by energy Institute, UK. Delivering Sustainable Biofuel, (2007) Energy World, April 2007, published by energy Institute, UK. Everett, B., (1996) Solar Thermal Energy, In: Boyle, G., (eds) Renewable Energy: Power for a Sustainable Future. Oxford, Alden Press Ltd. 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