Question

3) A home requires 62 kWh of energy (heat) on a winter day to maintain a constant indoor temperature of 20 °C. (a) How much collector surface area does it need for an all-solar thermal heating system that has an absorptivity of 0.2? The average solar radiation in winter is about 6.5 kWh/m2/day. [35 points] a) What is the mass of water required if this energy is stored as sensible heat energy storage system? Where the water operates between 20 °C and 60 °C kcal and assuming constant specific heat of water at 1 kg C b) What is the mass of the water required if this energy is stored as latent heat energy storage system? Where the water operates between 20 °C and 120°C with latent heat of vaporization at 540 kcal/kg and assuming constant specific kcal heat of water at 1 kgoc c) Determine the energy density of both a) and b) in volume basis. Where 997and PH,0 (vapor) kg 0.6 H20 d) Comment on the difference between systems in part a) and part b). And what do you think is a better option?

Answer 1

a Let total cellector s rm Total theident radiaten en seupace per-day 6.5A Kk/h Total absorbed redint en en surtate per deay'-65#x0.2 kWh hence, 6.5 x0-2 x A 62 i x(60-20) Kタ → m= 531-28-83 ery aveible En ) Energy density- Energy avaitable mars/density) Volume Eneagy density per care a53142. -31897 Kcal m3 , density ror cate b= 531 H28-38니 Kfal u hen Liquid wati is converted o vporstea ncrease in ids velume. Case h is beter option 132/997 3739 Ke 83/0.6 is eneyy canfent ncreave witi relatively larger uohen uve wwant to uimit our uoater con sumption Case Baiu bettes option wchen use want to redluce our extra main tenence cos