Wind power systems for heat production, storage and supply of living buildings: Parameters of the small wind thermal stations

Table 4.2 gives assessment of parameters for small wind power systems and traditional gas heating systems at the next initial data: area of domestic building is 30000 m2; specific heat loss in buildings is 40 W/m2; the duration of the cold season is 6 months; average duration of the wind is 10 hours per day; average wind velocity  is 7 m/s; density of air is 1.2 kg/m3; energy efficiency of wind power system is 0,9; specific heat capacity of coolant (water) is 4.2 kJ/(kgxK); working temperature is 2000C; working range of water temperature is 700C …200C; energy efficiency of the gas boiler is 0.9; specific heat of combustion for a natural gas is 32,7 MJ/m3.

 

 

The examples of energy parameters calculation for wind and gaseous power systems for heat supply

 

Thermal parameters of building: Heat losses’ intensity for 1 m2 area of building - 40 W = 40 J/s. Specific heat losses of 1 m2 area during 1 s - 40 (J/s)m-2 = 40 J = 40Jх0,24 calхJ-1 = 9,6 cal. Heat losses of 1 m2 area during 1 hour - 40(W/m2) х 3600 s = 144 kJ = 144 kJ х 0,24 kcal/kJ = 34,56 kcal. Heat losses during a day - 144 kJх24 = 3,46 MJ = 3,46 MJ х 0,24 Mcal/MJ = 0,83 Mcal. Heat losses during a month - 3,46 MJ х 30 = 103,4 MJ = 103,4 MJ х 0,24 Mcal/MJ = 24,8 Mcal. Heat losses during 6 months of heating season - 103,4 MJ х 6 = 622,8 MJ = 622,8 MJ х 0,24 Mcal/MJ = 149,5 Mcal. Total heat losses of building during a day – 30000 m2х 3,46 MJ = 103,68 GJ = 103,68 GJ х 0,24 Gcal/GJ = 24,9 Gcal. Heat losses’ intensity for all area of building(s) – 40 (J/s) х m-2 х 30000 m2 = 1,2 MW. Necessary average power for heat supply – 1,2 MW..

 

Wind power: Necessary average power of wind turbine at duration of wind 10 hours a day is (1,2 MW х 24 h.)/10 h = 2,88 MW. Average wind power that fall on 1 м2 area, perpendicular to wind flow direction and wind velocity of 7 m/s during 1 s is 0,5 х 1,2(kg/m3) х 73 (m/s)3 х 1 m2 = 206 J = 206 J х 0,24 cal/J = 50 cal. Specific WPT power is 206 W. During an hour 1 m2 of useful wind flow area produces 0,206 kWh = 0,206 kWh х 860 kcal/kWh = 177 kcal of energy. During a day – 10 х 0,206 kWh = 2,06 kWh = 2,06 kWh х 3,6 MJ = 7,4 MJ = 7,4 MJ х 0,24 Mcal/MJ = 1,78 Mcal. Area of wind flow cross section А, that provides power 2,88 MW is 2,88(MJ/s)/[0,5 х 1,2 (kg/m3) х 73(m/s)3] = 15534 m2. Length of turbines blades is ~ 70 m.

 

Heat accumulator parameters: Heat quantity, stored by 1 m3 volume of water with a specific heat capacity 4,2 kJ/(kg·°C) at heating from 200C to 700C is 4,2 kJ/(kg·°C) х 50·°C = 210 MJхm-3; volume of water with a specific heat capacity 4,2 kJ/(kgх°C) that provides accumulation of 103,68 GJ during a day is 103,68 GJ/0,210 GJхm-3 = 493,7 m3.

 

Heat-only boiler station parameters: Volume of natural gas necessary to heat 1m2 of apartment during 1s is 40 J/[32,7х 106 (J/m3) х 0,9] = 1,359х10-6 m3; Volume of natural gas necessary to heat  2 of apartment during 1 hour at energy conversion efficiency of heat-only boiler station of 0,9 is (0,144 MJ)/[32,7 MJm3х0,9] = 0,005 m3. Consumption of natural gas to heat 1m2 area during a day is 0,005 m3 х 24 = 0,12 m3. Consumption of natural gas to heat 1m2 area during a month is 0,005 m3 х 24 х 30 = 3,6 m3; Consumption of natural gas to heat2 area during 6 month of heating season is 0,005 m3 х 24 х 30 х 6 = 21,6 m3/m2. Consumption of natural gas to heat total area during 6 month of heating season is 570696 m3.

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