ARTICLE / MAKALE Project Development The development of the project through the detailed design and construction phases was carried out by means of a forma! partnering arrangement between Portsmouth City Council, United House, Vital Energy and PB Power. This partnership enabled the design, construction and operating experience of the contractors to be brought to the project much earlier than normally possible and during the design period. PB Power was retained to ensure the original energy-efficiency concepts were taken forward. United House was the principal contractor and carrier out the work in the dwellings. Vital Energy supplied and installed the heat mains, hydraulic interface units and the energy centre plant and is now responsible for operating the whole system. A forma! risk assessment was carried out at the start of the detailed design phase to focus effort to design out or reduce risks as far as possible. Communications with residents was also important as the dwellings remained fully occupied throughout the works. A full-time resident liaison officer was employed to arrange access to flats and act as first point of contact for any issues. The projeci construction phase lasted 18 months, which in cluded installing new heating in the 515 dwellings, the installation of new boilers and the CHP unit and the heat mains to link the eight housing blocks, the arts and leisure centre and the schools.The electricity produced by the CHP unit is used partly on site to supply the Energy Centre's pumps and boiler fans, but the majority is delivered into the local network and sold in bulk to a public electricity supplier. The electricity produced is exempt from the Climate Change Levy, a UK energy tax. Energy Efficiency Benefits The system's energy efficiency has been calculated and can be compared to the previous arrangements. The carbon dioxide content of heat from a CHP unit depends on the electrical and thermal efficiencies of the unit and the emissions factor of the electricity displaced by the unit. The UK's average electricity emissions factor is 430 g CO/ kWh. However, this includes a significant contribution from nuclear and renewable energy. As the operation of the CHP plant will have no effect on these baseload or preferential generators, it is the fossil fuel generators only that will be displaced. A calculation of the emissions factor tor this displaced power was given in Energy Trends of June 2003 as 697 g CO/ kWhe, reducing to 521 g CO/kWhe by 2010. This reflects the increasing use in the UK of combined cycle gas turbine plant fired by natura! gas. The draft Building Regulations in the UK to be implemented from A�ril 2006 use a figure of 568 g CO/ kWhe. Using this figure and the efficiencies of the CHP unit means that heat produced by the CHP has a negative carbon dioxide content of- 14 g CO/ kWh. Not all of the heat can be supplied by the CHP unit. it is not economic to size the unit to meet the peak heat demand, and there will be times when it is down for maintenance. The use of the thermal store will enable about 70% of the annual heat "' ı::: - .2 ı:ı "' Q) "' :.: ·- o. E o. Q) :ı Q) "' ı:ı - ·- "" >< Q) o .ı:: 'ö ..ı::: ı::::?;0." .0 - ... cıı cıı - 450 400 350 300 250 200 150 100 50 o .lı Electric Gas CHP/OH heating boilers Figure1. Carbon dioxide emissions when emissions factor for electricity displaced by CHP is 568 g CO/kWh demand to be supplied by the CHP unit, will the remainder being supplied from high- efficiency gas boilers producing heat with a carbon dioxide content of 236 g CO/kWh (194 g CO/kWh for gas and 82% boiler effi ciency). The overall carbon dioxide content of the heat from the energy centre is therefore 61 g/kWh. To this value for overall carbon dioxide content it is necessary to allow for heat losses of about 8%, giving a delivered energy carbon dioxide content of 66 g/kWh. This can be compared with the equivalent numbers for heating with electricity of 430 g CO/kWh (current grid mix figure) or gas-fired condensing boilers of 226 g CO/kWh. The carbon dioxide reduction is therefore 71 % compared with gas-fired boilers, as Figure 1 shows. Benefits to Portsmouth City Council The cost of the projeci was about $10,500 per dwelling, or about twice as much as the equivalent upgrade for an individual condensing boiler system. However, there are many advantages: • Lower cost of heat for residents • Maintenance costs are reduced as there is no need for an annual gas inspection and boiler servicing within the flats • The heat provision has a much lower carbon dioxide content • No flues penetrate the fabric of the building • Controllable and quiet operation • Avoidance of the cost of installing boilers in the new arts and leisure centre • Fewer complaints about heating. Benefits to Residents The residents previously paid a fixed charge for the provision of space heating, whether using electric heating or communal gas-fired boilers. in addition, electricity or gas for domestic hot water heating was paid for separately. Typical charges tor heating and hot water tora two- bedroom flat were about $11.80 per week. The charges using the new CH P system have been reduced to less than halt this fıgure: $5.30 per week. The communal gas- fireci boilers used to be shut down completely in the summer, which caused problems if there was a cold spell in May or September. Now the heating is available to residents throughout the year. t ENERJİ & KOJENERASYON DÜNYASI · OCAK I ŞUBAT 2006 A 6 --4-+==�:::::.:.:: ::::::::::.:..:.:....:::.:::.::..::::::.:.-=::::::.:c:::.::....::::::.:_____:,=======-- "� "AB'ye Giriş Sürecinde Türkiye'de Kojenerasyon-Yeni Gelişmeler"
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