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plants. In their paper “Life Cycle Climate Performance Model for Residential Heat Pump Systems”, Zhang and co-workers developed an software plugin that calculates LCCP values for residential heat pumps. The work is documented in an AHRTI report (Zhang et al., 2011). Life Cycle Climate Performance Tool - V1.0 In continuation to the AHRTI work described above, a web-based calculator was developed by the University of Maryland College Park (UMCP, 2017), under a subcontract from Oak Ridge National Laboratory (ORNL), for supermarket refrigeration and air source heat pump systems. The “LCCP Desktop Application v1.0” tool is available online (UMCP, 2017). The results of these tools will vary based on the assumptions used, particularly the assumptions for the efficiency of the system, power generation, refrigerant leakage and refrigerant management methods. Therefore, these tools are best used for comparative analysis of competing systems. It may be possible to improve the portability of the results through the establishment of documented standards and methods. To this end, there is a need to standardize the tools by an international agency like ISO or IEC to allow comparison across manufacturers. 11.4.3 Total Equivalent Warming Impact (TEWI) TEWI is a measure of the direct and indirect global warming impact of equipment. It is based on the total related emissions of greenhouse gases during the operation and disposal, and the indirect emissions. Indirect emissions are the CO2 that is generated at the fossil fuel power plant when energy is consumed by the refrigeration equipment. TEWI is measured in units of mass in kg of carbon dioxide equivalent (kg CO2-eq.). The TEWI equation can be found in (EN, 2008) and (Fischer, 1991). It can be evaluated in conjunction with seasonal profiles of temperatures and capacity. TEWI is a widely accepted tool because of its ease of use and transparent way of showing the calculation. TEWI was introduced in the 1990’s and is well known in the industry. TEWI is much simpler to implement than a complete LCCP calculation. When emissions related to energy are dominant, which is often the case for RACHP applications, TEWI may be preferable to LCCP. However, the impact of refrigerants on the environment goes beyond the direct and indirect values produced in a TEWI analysis. TEWI does not account for the process of production, transportation and other significant factors. Studies of LCCP have included the fugitive emissions of a refrigerant from production until installation in equipment, the embodied energy or GHG emissions associated with producing the refrigerant, and the GHG emissions associated with extracting materials and producing components of an air-conditioning or refrigeration system. Other factors not included in TEWI are the following: Energy effect of refrigerant charge leakage: as refrigerant charge leaks from a refrigeration system, the system capacity and efficiency are affected. The effect of this leakage over time on net GWP impact has been studied using LCCP by several authors (Beshr, 2014). Refrigerant mismatch: for example, when a refrigerant that is poorly matched for the cooling task, such as CO2 in a continuous high ambient condition, the energy consumption is elevated and can result in the release of additional CO2 at a fossil fuel power plant when compared to a correctly matched refrigerant. Both LCCP and TEWI are affected by the product efficiency and thus give a better indication than a simple GWP reference of what the greenhouse gas emissions associated with the use of air- conditioning and refrigeration equipment will be. LCCP and TEWI calculations provide more information on the sustainability of air-conditioning and refrigeration equipment than GWP or energy efficiency alone; therefore, these methodologies are recommended when comparing 2018 TOC Refrigeration, A/C and Heat Pumps Assessment Report 213PDF Image | Heat Pumps Technical Options
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