CASE STUDY [100 marks] You are tasked with designing a system to supply energy to a new block of 30 'eco' flats, providing heat (150 kWh per flat) and electricity (at a constant rate of 5KW per flat) for one day (24 hours). Electricity will be supplied by proton exchange membrane fuel cells (PEMFCs), fed by hydrogen, and operating under standard conditions (P=1atm,T=25C), with a fuel utilisation of 80% and oxygen utilisation of 100%. For the given property, it would be appropriate to install commercial stacks of 15 individual cells, arranged in series. Hydrogen gas necessary for the 1-day operation is stored in 100L tanks, at 700atm and room temperature, T=25C. Heat will be delivered by an air-source cascade heat pump system, operating under the vapour-compression refrigeration cycle, between temperatures of 10C (assume air temperature is stable) and 100C, and using water as the working fluid. The cascade system has two cycles, and an intermediate temperature of 46C. You are requested to prepare a report for the client, containing the following sections and information: Section 1. Calculations and estimations of the energy parameters, justifying assumptions made. In the fuel cells subsystem: (i) Minimum number of hydrogen tanks required for storage. [20 marks] (ii) Overall subsystem efficiency. [10 marks] In the heat pump subsystem: (i) Sketch of the vapour-compression refrigeration cycle (T-S diagram) [5 marks (ii) Work done at the compressor. (iii) Overall subsystem efficiency. Section 2. The client has enquired whether it would be more economical to provide heat using hydrogen boilers, with 100% fractional conversion of hydrogen, producing water in the gas phase. The reactants (hydrogen and air, in stoichiometric and dry conditions) enter the boiler at 25C, and the products leave at 250C. Given that the cost of hydrogen is 8.50/kg and of green electricity is 67.2p/kWh ( p cents of E ): (i) Verify and justify the suggestion. [20 marks] (ii) Critical discussion/comparison between heat produced using heat pumps in section1 and hydrogen boilers, in terms of energy conversion efficiency. Consider the assumptions made in your calculations. Take into account energy parameters, infrastructure, environmental concems and cost limitations (qualitatively) (1 page maximum) [15 marks] General format and presentation will be assessed, in terms of adequate scientific writing style and notation, citation and clarity of figures, tables and their captions and headers. [5 marks] Maximum page count is 20 (excluding plagianism form, front page and list of contents), in A4. Minimum specifications: Anal (font), font size 11 , and 2cm margins in all directions