o C Think of why air and water is heated at home? To what temperatures do You need to heat? What about humidity? Which air velocities are accepted?

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1 Ready the 8 th of march, leave to Peter Kjaerboe via Inga deriez. Energy balance in your home, suggestions for project Aim To get an understanding of the importance of energy for living in a society a good start could be to estimate the amount of power passing Your home. Different activities need simply a certain amount of energy. Nomenclature A Area m 2 P power W Q energy kwh, J R th heat resistance (W/(m 2 K)) -1 U U-value (=1/ R th ) W/(m 2 K) k conductivity W/(mK) θ temperature o C T temperature K h heat transfer coefficient W/(m 2 K) Method Collect data and present in written form. Use equations, pictures and diagrams. Take into account energy such as heat for transmission through walls and windows, heat for air i e ventilation, food, lightning, hygiene and communication. If You have time compare also energy for transport. Think of why air and water is heated at home? To what temperatures do You need to heat? What about humidity? Which air velocities are accepted? What temperature do we reach without auxiliary heat? Count with metabolism i e body combustion, heat from electrical appliances and radiation from sun. Multiply with the amount of people in Sweden approximately Depending on Your choice multiply with number of rooms or houses. Make tables such as Transmission Surface U-value Area Temperature- Power difference Window Door Wall 1 Wall 2 This will give you power, P transmission. 1

2 Ventilation Flow Density Heat capacitivity Temperature- Power of air difference This gives You power for air heating, P ventilation. Add this P sum =P transmsision + P ventilation Water Flow Density Heat capacitivity Temperature- Power of water difference This gives power for water heating. Calculate free heat from - inhabitants - solar radiation through windows - lights - cooking This gives You P free power, P free add to P. Should of course be negative. Table 1. U-values or Rvalues, in Sweden different buildings and age. Year of construction Single family house Multi family house U R U R W/(m 2 K) m 2 K/W W(m 2 K) m 2 K/W ,55 1,8 0,80 1, ,55 1,8 0,65 1, ,38 2,6 0,45 2, ,30 3,3 0,35 2,9 2

3 U-value of windows approximately U window =5,6/n or R th =0,175n were n is number of panes. U is in W/(m 2 K) and R m 2 K/W. Table 2, Heat conductivity examples and R values depending of thickness, d. Material k, W/(mK) R th wood lightconcrete 0,14 7 d mineralwool, ecofiber 0, d cork 0,10 10 d concrete, glass 0,9 1,1 d Heat resistance R=heat transfer coefficient h can be calculated as R=1/h Assume R surfaces approx 0,20 then R = d/k by adding each R tot =ΣR You are always free to check other materials in litterature. Power is normally written as P=1 /R A Δθ compare analogy with current, resistance and difference of potential. Heat.by itself... from hot to cold and balance, the sum of energy is constant.. Hints Solar radiation se enclosure for Stockholm. Use average data! Does radiation on wall affect transmission? Heat from metabolism equivalent to energy in food. Heat from light bulbs and electrical tools and computers. Ventilation flow from combustion and drying water from washing (evaporation) approx 10 l/(second person). Hygiene water. Measure need for shower and washing multiply with heat capacitivity and temperatures. This is the situation today, what about tomorrow, compare in the past. If time look at dynamic situation. Cold temperatures occurs only for short periods see picture 2. 3

4 Table 3. Temperatures each month in Stockholm. Average temp Month -2,9 1-3,1 2-0,7 3 4,4 4 10,1 5 14,9 6 17,8 7 16,6 8 12,2 9 7,1 10 2,8 11 0,1 12 Table 4. Occurrence of certain temperatures in Stockholm. temp tid sthlm -22,5 1-17,5 5-12, , ,5 7 Temperature outdoor tout, oc Time with certain temperature, part of year a, o/oo Temperature outdoor, tout, oc tid/grad Time with certain temperature in Sthlm, n, hours Temperatur Picture 1. Occurance of temperatures during a typical year, Stockholm. Picture 2. Occurrence of certain temperatures in Stockholm. 4

5 Table 5. Data on transmitted solar radiation through single- respectively double-glazed windows. 5

6 Table 6. Data on solar irradiation reaching vertical and inclined surfaces. 6