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Explore the most cost-effective and environmentally friendly water heating methods for a University of Bristol hall of residence. Compare thermal and financial models to find the best solution. Recommendations include a Mitsubishi ASHP for reduced emissions and costs.
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The most acceptable method of water heating for Badock – a University of Bristol Hall of Residence. A Thermal and Financial Model Naomi Knight - University of Bristol - 2013-2016
Background • Hot water accounts for 18% of domestic energy use in the UK. • Halls of Residence are unique • University of Bristol target - 38% reduction in emissions.
Aims and Objectives Find the cheapest method of heating water in Badock Hall of Residence, with consideration of the environmental impact of the system. Objectives: • Undertake site visit to identify current systems and suitability for alternate systems. • Produce thermal model of the current system and a solar thermal system. • Produce financial model of both systems • Compare results with those of Yingpei Gao
Current System Simple schematic of current electric immersion heater system.
Current System (2) System with WWHR and insulation Current system Varying tank temperature over the course of the day for different system configurations
Solar Thermal Varying tank temperature over the course of the day for different system configurations
Solar Thermal (2) Data set Find time Panel and HX heat addition Electricity and heat loss Left: simple flow chart of thermal matlab model, Above: Stratified tank model, water returns via manifold diffuser. Mass and Heat balance for tank
Solar Thermal (3) Monthly solar fractions for each system. 33% - 41% annual solar fraction - increases to 35% - 44.7% for PV pumping.
Financial Model • Includes energy tariffs – FIT and RHI - and maintenance costs. • Solar thermal ROIs £102, 000 and £146,000. (Highest ROI for small FPC system with PV pump.) • ASHP ROI £200,000.
Financial Model (2) Do nothing scenario Annual cost of each system configuration, including amortised CAPEX and predicted maintenance costs. ASHP
Environmental Impact Gas emissions higher than grid emissions ASHP Annual CO2 emissions for each system, 70% reduction for solar thermal and 90% reduction for ASHP.
Conclusions • Mitsubishi ASHP is the recommended heating method. (Limited) • Potential for solar thermal • Worst possible outcome – is do nothing.