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The effects of global warming, climate change etc are well known and accepted by most governments of the world as a problem that can be attributed to carbon emissions generated by industrialisation. In 1997 the United Nations set a framework aiming to reduce these carbon emissions, known as the Kyoto Protocol, in which member states agreed that 'stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.' should be adopted. As of 2009, 189 member states have ratified the principles set out in this protocol including Great Britain. To meet the principles of the Kyoto Protocol the Government have set targets for industry and government organisations to meet.
The NHS's energy consumption is increasing year on year and in order to meet government targets the NHS are required to reduce both carbon emission and energy consumption of its buildings and engineering services; NHS carbon reduction strategy for England states 'The NHS should set itself targets and trajectories to meet the provisions of the Climate Change Act'. As an incentive for the NHS to reduce their carbon emission the government made available funds to install viable sustainable technologies. One such technology to achieve these targets has been by using Combined Heat and Power (CHP) systems.
A feasibility study was undertaken at Royal Preston Hospital(NIFES Consulting Group, 2006) in order to find the most effective sustainable technology that could be found to reduce carbon emissions. From the findings of this study it was decided that a Combined Heat and Power unit would be the most cost effective means to reduce carbon emissions. In 2009 a gas fired reciprocating engine CHP system was installed at the Hospital that provides an electrical output of 1800kW, approx 700kg of steam/hr and low grade heat for heating and DHW. The aims of this report is to determine if the installed CHP is in fact the most viable and cost effective approach to reducing carbon or if there are most suitable sustainable technologies available.
Aims and Objectives
The project will appraise this CHP system and an analysis of the CHP will be conducted in order to determine the CHP's efficiency. Following the initial analysis the project will investigate any improvements that could be made in order to further improve the efficiency in the CHP system. Finally alternative sustainable technologies will be discussed and compared against the CHP system with respect to their carbon saving and energy reduction capabilities and the viability of these technologies over CHP.
The CHP has been installed in order to reduce the hospitals carbon footprint and as a subsequent benefit to reduce the annual energy costs.
The initial phase of the project will discuss CHP systems currently in use and their relative merits and disadvantages such systems pose within this setting. This will take the form of a literary review of current ideas and practices incorporating the latest guidance and legislation. From this the choice of the CHP installed will be assessed as to its suitability for this particular site.
The second part of the project will assess the particular CHP system that has been installed and it will be determined if this system is performing to the CHP specification. In order to determine this then data will be collected over time and then assessed to determine the efficiency of the system is as anticipated and within the expected norm. Following this assessment the system will be critically appraised in order to determine if there are further enhancements/modifications to the system which will improve the overall efficiency.
Outline of ....
What is CHP
Electrical power generation produced centrally and distributed along the national grid is inherently inefficient as the heat produced in generating the electricity is 'dumped' to the atmosphere. Combined Heat and Power also know as co-generation is the production of electricity and the recovery of the heat produced in a single process. In CHP systems the fuel used can be natural gas, oil, coal, bio gas or other bio fuels or any combination of these. The use of these fuels by the CHP is to provide the heat and electricity to a building and in doing so is more efficient than if the heat and electricity was provided separately, as is the case with centrally produced electrical power. CHP's can convert up to 80% to 90% (Combined Heat and Power association, 2010) of the fuel used into useful energy whereas electricity produced by central electricity generating stations are typically 30% to 40% fuel efficient. The production of electrical power by CHP requires high temperatures, however in order to utilise the waste heat in buildings lower temperatures are required to provide space heating. The high temperatures produced by the co-generation process are required to be converted into temperatures that can be utilised by space heating or process energy needs. This can be achieved by utilising the low grade heat for example that emitted by the cooling system of a reciprocating engine and by using the high grade heat such as that emitted from the exhaust gases of a reciprocating engine.
Figure - Energy balance for a typical gas engine (GPG388 Good Practice Guide, 2010)
History of CHP
In the late 1800's the use of electricity was becoming more widely used in both the domestic and industrial areas. Electrical generation used amongst other means reciprocating steam engines to produce this electricity which was found to be inefficient and wasted a large amount of steam. This wasted steam was used to provide steam for process which included space heating.
Principles of CHP
Types of CHP systems
There are three main ranges of CHP systems available for buildings, these are:
Micro CHP (range, up to 5kWe)
Small Scale (range below 2MWe)
Large Scale (range, above 2MWe)
Review of Guidance and Legislation
System under investigation
Figure - CHP
Electrical generation of the system
Thermodynamics of the system
CHP and Carbon Reduction in the NHS
Review of alternative sustainable technologies
RESULTS AND DISCUSSION