Reference no: EM132601047

ME60234 Energy Conservation and Waste Heat Recovery

Question 1. A pumped hydro energy storage system with an elevation of 40-m is considered for a power grid which has a load pattern of 600 MW during 18 hrs and 1200 MW for 6 hrs in a day. Calculate the nominal power output of a power plant that would meet this load demand with and without energy storage. What is the volume of water in [m3] that must be pumped to meet the energy storage demand. The electric generator efficiency is 0.8 and density of water is 1000 kg/m3.

Question 2. In a CAES plant, air is compressed from 1 bar, 25 ºC to 50 bar. Calculate the compressed air temperature, assuming Cp/Cv of air to be 1.4. If the compressor efficiency is 70%, what is the modified compressed air temperature?

Question 3. An electric heater is used to heat a room which is at 25 ºC while the outside temperature is -5 ºC. It is decided to replace the heater by a heat pump. COP of the heat pump is 80% of ideal COP. The total heat loss from the room is estimated as CΔT, where ΔT is the temperature difference between the room and outside and C is estimated as 0.5 kW/K. Calculate the saving in electrical energy in kW.

Question 4. A flywheel in the form of a circular disc is slowed down from 5000 rps to 2000 rps. The device weighs 20 kg and has a radius of 30 cm. Calculate the energy released.

Question 5. n-Hexadecane, an organic PCM with melting point of 18°C and specific gravity of 0.8 is used for building air-conditioning. The PCM chamber has a volume of 2 m3. If the latent heat of fusion of n-Hexadecane is 225 kJ/kg, calculate the energy storage capacity of the unit. Assuming the PCM to be frozen, if outside air at 30°C has to be cooled down to 22°C by the PCM and supplied indoor from 10 am to 4 pm what should be the maximum mass flow rate of air? Neglect sensible heating of PCM and assume specific heat of air to be 1.0 kJ/kg-K.