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1 Name: Personal number: Sustanable Energy Utlsaton SEU-SEM1: Heatng demand for a sngle famly resdence In order to desgn a proper heatng system for a sngle famly resdence a heatng demand calculaton has to be performed. The maxmum heat load for the house s used to decde the sze of the boler so the house could be heated properly durng cold perods. The energy loss calculaton s to get an dea of the total energy need for the house durng one year and hereby also to calculate the total runnng cost for the heatng. Make a calculaton for the losses through walls, roof, wndows, doors, and ground for the whole house. Mnor detals n the buldng shall not be consdered. In ths assgnment you wll be asked to fll n a number of tables. At the top of each table column, the unts are gven. Ths means that you are supposed to enter the values usng ths unt. THIS DOES NOT IMPLY THAT THE UNITS YOU GET WHEN YOU USE THE EQUATIONS BELOW ARE THE SAME AS THE ONES YOU SHOULD ENTER IN THE TABLE. THEREFORE, CHECK UNITS AND BE VERY CAREFUL WITH UNIT TRANSFORMATIONS! In order to promote contnuous learnng, you wll get extra ponts on the exam f you submt the assgnment before the deadlne and receve a passng grade. Deadlne for submsson to receve bonus s September 25, If ths assgnment s submtted after December 9, 2009, no feedback s gven by teachers untl September 2010 (automatc correcton wll of course work n the meantme). The assgnment should be submtted through the Blda platform. The submsson tool wll be avalable on September 14, at the latest. Please keep all your calculatons untl the entre course s reported as complete! FINAL RESULTS MWh/year Q total,losses (Calculated) Q total,real (Read from graph) Queston: There s a dference n the quantty of heat demand calculated and the one read from the graph, explan why. Page 1 of 16

2 Input data Date of Brth (yy mm dd): 0 1 => 2 3 => 4 5 => 6 7 => 8 9 => t t t t t = 18 C = 20 C = 21 C = 22 C = 23 C 0 1 => Kruna 2 3 => Umeå 4 => Östersund 5 => Karlstad 6 => Stockholm 7 => Göteborg 8 => Vsby 9 => Malmö 1. Cty n Sweden: (gven by the nput data above). Desgn ndoor temperature, t : C (gven by the nput data above). Accordng to the cty your house s located and the type of buldng, fnd on the map the relevant Desgned Outdoor Temperature, t DOT, (Fgure 1). t DOT = C Page 2 of 16

3 Addtonal nstructons to SEU Semnar Assgnment 1 Snce the assgnment s automatcally corrected, I provde these extra nstructons. Earler, when I corrected the assgnment manually, the students had to assume the thngs below. Calculate for a new house, meanng that you should use the specfc heatng demand for new houses as gven n table 2, page 10. Assume that the house lght,.e. use DOT1 as the desgn outdoor temperature (get DOT1 from table on page 11). The volume of the house can be assumed to 576 m³. For ventlaton and nfltraton, use an ar densty of 1.2 kg/m³. The ventlaton system s equpped wth a heat exchanger, assume effcency, η = 0.6. Assume that there are 4 persons lvng n the house and that the heat dsspaton s 100 W/person. Assume that they are all at home durng 12 h per day on average. Heat dsspated from electrcal applences are assumed at 685 W whch yelds an average energy addton at about 6000 kwh/year. Assume that the wndow area s dstrbuted n the followng manner: 10% or the wndow area s facng north, 25% s facng east, 40% s facng south, 25% s facng west. Kruna Östersund Umeå Karlstad Göteborg Stockholm Vsby Malmö Page 3 of 16

4 2. Transmsson loss calculatons Heat load: P wall, roof, wndow, door = U A t (. t DOT ) [ t 3 ] ( t ) = U A t ( ) Pground = U A t g o + Energy loss: Q Q wall, roof, wndow, door ground = U A S [ ( t + )] Δτ = U A t 3 o Maxmum transmsson heat load: P transm, total P = Total transmsson energy loss: where: U heat transfer coeffcent, (Table1), W/m 2 K A surface area, m 2 t desgned ndoor temperature, o C t DOT desgned outdoor temperature, o C ground temperature, o C t g t o Q transm, total mean annual outdoor temperature, (Table 2), o C S specfc heatng demand, (Table2), degree-hours, K h/yr Δτ heatng perod, (Table 2) x 24, h/yr Q = Part Area, m 2 U-value, W/m 2 K Max heat load, kw Energy loss, kwh/year Walls 160 Roof 190 Wndows 44 Doors 12 Ground 160 Total transmsson loss P transm,total (kw) Q transm,total (kwh/yr) Page 4 of 16

5 3. Ventlaton loss calculaton Ventlaton heat load: P ventlaton ( t. t ) ( η) = V ρ c 1 p DOT Ventlaton energy loss: Q ventlaton = V ρ c p ( 1 η) S Mnmum ar flow: Infltraton heat load: P nfltraton p V = 0.5 V (m³/h) ( t. t ) = 0.1 V ρ c, (0.1 represents 0.1 ACH). DOT Infltraton energy loss: Q nfltraton = 0.1 V ρ c p S Total for ventlaton heat load: P ventlaton, total = Pventlaton + Pnfltraton Total for ventlaton energy loss: Q ventlaton, total = Q ventlaton + Qnfltraton Total heat load: Total energy loss: P = P + P total,max total,losses transm, total Q = Q + Q transm, total ventlaton, total ventlaton, total where: V ventlaton ar flow, m 3 /s ρ ar densty, (Table 3), kg/m 3 c p specfc heat of ar, (Table 3), J/kg K t desgned ndoor temperature, o C t DOT desgned outdoor temperature, o C η effcency of the heat exchanger (n case of system wth heat recovery), (50 80%, typcally 60%) S specfc heatng demand, (Table2), degree-hours, K h/yr V total volume of the house, m 3 Page 5 of 16

6 Flow, m 3 /s Heat load, kw Energy loss, kwh/year Ventlaton Infltraton Total ventlaton losses P ventlaton, total Q ventlaton,total Total loss (transmsson + ventlaton + nfltraton) P total, max (kw) Q total, losses (kwh/yr) Calculaton of the specfc energy demand for the house By makng calculatons of the energy gan and energy demand for every month durng the heatng season and plottng ths values n a graph t s possble to estmate the specfc energy requrement for ths specfc house. A 4-person famly, two adults and two chldren lve n the house. Both the length of stay ndoors as well as actvtes performed vary among the famly members. In addton, varous electrcal applances are used n the household. The heat gan from solar radaton through wndows s tabulated for a standard 2-glazed wndow under normal weather condtons (Table 5). Plan of the house s presented n Fgures 2 4. Page 6 of 16

7 4. Heat gan from occupants and varous electrcal applances Q people = No.of people tmendoors heat producton Source Heat from occupants Free Energy Number of persons: Tme ndoors: h/day Heat producton per person P people, W (Table 2.3 n Thermal comfort) (Use a mean value) Q people kwh/year Electrcal applances Heat producton P el.appl., W (Use a mean value) Q el.appl. kwh/year (Table 4) (approxmately 6000 kwh/yr) Free Energy Heat Load: Free Heatng Energy Gan: P = P + P FreeEnergy people Q = Q + Q FreeEnergy people el.appl. el.appl. Free energy: kwh/day Page 7 of 16

8 5. Solar gan through the wndows n dfferent drectons Solar gan: Q solar = 0.9 q A wndow,, Wh/day where: 0.9 overall solar transmsson coeffcent for double-glazed wndows q solar gan, (Table 5), Wh/m 2 day A wndow, area of wndow n gven drecton, m 2 Drecton North East South West Wndow area, m 2 Σ = 44 m² Drecton North, East, South, West, Total, solar Solar + Free Month kwh/day kwh/day kwh/day kwh/day kwh/day energy, kwh/day January February March Aprl May June For the sake of July graph only August September October November December Page 8 of 16

9 6. Losses due to Transmsson and Ventlaton Monthly Monthly heat load losses: Q month = P total, max where: P total, max maxmum heat load, W t desgned ndoor temperature, o C t DOT desgned outdoor temperature, o C t month mean monthly outdoor temperature, (Table 6), o C t t t t month DOT 24 Month Mean temperature, (Table 6), o C Total heat, kwh/day January February March Aprl May June July August September October November December Make a dagram on a separate sheet of mllmeter paper wth tme on the x-axs and heat losses and gans n kwh/day on the y-axs. Also, plot a curve for the monthly outdoor temperature (use a rght hand sde y-axs). Note that all values are for the 15 th of every month. Try to estmate or measure the surface under the curve for the heat load to fnd the requred energy demand n kwh/year for ths specfc house Heat energy, kwh/day July August September TRANSMISSION, VENTILATION INFILTRATION LOSSES October November December January Page 9 of 16 SOLAR IRRADIATION + FREE ENERGY INTERNAL GAINS FROM OCCUPANTS AND ELECTRICAL APPLIANCES February March Aprl Outdoor temperature ( C) May Tme, days June

10 Table 1. Overall heat transfer coeffcents (U-values) for walls, roof, wndows, doors and ground Part U-value, W/m 2 K Wall 0.25 Roof 0.15 Wndow 2.0 ( ) Door 1.0 Ground 0.15 Table 2. Heatng season, specfc heatng demand for houses, and average mean outdoor temperatures for varous locatons n Sweden ( ) Locaton Heatng season start end Length of heatng season, days Specfc heatng demand, S, K h/yr Old houses New houses Annual mean outdoor temperature, t, o C Kruna Umeå Östersund Karlstad Stockholm Göteborg Vsby Malmö o Table 3. Propertes of ar at varous temperatures Temperature, o C Densty, kg/m 3 Specfc heat, kj/kg K Page 10 of 16

11 Table 4. Heat gan from varous applances Applance Common power Approxmate annual Length of use demand (W) use (kwh) Freezer 200 Thermostat 1000 Refrgerator 150 Thermostat 750 Toster mn/day 60 Dshwasher 2000 Once/day 540 Mxer mn/week 2 Food processor 450 1h/week 23 Coffee brewer 800 1h/day 288 Mcrowave mn/day 90 Ktchen fan 150 1h/day 55 Cookng plates mn/day 400 Oven h/week 200 Vacuum cleaner h/week 52 Iron h/week 60 Dryer h/week 210 Washng machne h/week 210 Lght bulb 60 3h/day 65 Tape deck 25 1h/day 9 Rado 40 1h/day 15 TV b/w 100 2h/day 70 TV color 150 2h/day 108 Vdeo 45 1h/day 16 Sauna h/week 260 Hardryer h/week 52 Car-warmer 600 3h/day (wnter) 220 Razor 20 10mn/day 1 Sewng machne 75 1h/week 5 Table 6. Normal annual and monthly (for 15 th of every month) outdoor temperatures for varous locatons n Sweden ( ) Locaton Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Kruna Umeå Östersund Karlstad Stockholm Göteborg Vsby Malmö Cty DOT1 ( C) DOT5 ( C) Kruna Umeå Östersund Karlstad Stockholm Göteborg Vsby Malmö Page 11 of 16

12 Table 5. Solar gan through double panel wndows (for 15 th of every month), Wh/m 2 day Month Drecton Jan Feb Mar Aprl May Jun July Aug Sept Oct Nov Dec Kruna North East South West Umeå North East South West Östersund North East South West Karlstad North East South West Stockholm North East South West Göteborg North East South West Vsby North East South West Malmö North East South West Page 12 of 16

13 DOT 1 DOT 5 Fgure 1. Desgn Outdoor Temperatures for Sweden Page 13 of 16

14 Storage & Hobby Room Dnng Room Lvng Room Entrance GROUND FLOOR Ktchen Bedroom UPPER FLOOR Bedroom Hallway Bedroom Storage Attc / Storage Dmensons n mm. Fgure 2. Plan of the house Page 14 of 16

15 Dmensons n cm. Fgure 3. Plan of the house Page 15 of 16

16 North South East West Fgure 4. Plan of the façades of the house Page 16 of 16