Table 4.2 lists the parameters of wind and traditional systems for heat supply on the organic fuel of various capacity, designed for the following initial data: area of the greenhouses is 10000…100000 m^{2}; specific heat losses in the greenhouses are 200 W/m^{2}; the specific power of electric system of additional illumination of plants – 100 W/m^{2}; the average daily duration of the wind is 10 hours; the duration of the cold season is 6 months; average wind speed for a given region is 7 m/s; energy conversion efficiency of wind power system – 0,9; specific heat capacity of coolant (water) is 4,2 kJ/(kg x K); working temperature mode of operation for thermal storage unit – 20^{0}C…70^{0}C…20^{0}C; energy conversion efficiency of boiler on the organic fuel is 0.9; specific heat of combustion for fossil fuel (natural gas) is 32,7 MJ/m^{3}.
The examples of energy parameters calculation for wind and gaseous power systems for heat supply of green house with area of 10000 m^{2}
Thermal parameters of green house: Heat losses’ intensity for 1 m^{2} area of building - 200 W = 200 J/s. Specific heat losses of 1 m^{2} area per 1 s - 200 (J/s)m^{-2 }= 200 J = 200Jх0,24 calхJ^{-1} = 48 cal. Specific heat losses of 1 m^{2} area during 1 hour - 200(W/m^{2}) х 3600 s = 720 kJ = 720 kJ х 0,24 (kcal/kJ) = 172,8 kcal; Specific heat losses per day - 720 kJх24 = 17,28 MJ = 17,28 MJ х 0,24 Мcal/МJ = 4,15 Мcal. Specific heat losses during a month - 17,28 MJ х 30 = 518,4 МJ = 518,4 МJ х 0,24 Мcal/МJ = 124,4 Мcal; Specific heat losses during 6 months of heating season - 518,4 МJ х 6 = 3110 МJ = 3110 МJ х 0,24 (Мcal/МJ) = 746,5 Мcal; Total heat losses of building during a day – 10000 m^{2}х 17,28 МJ = 172,8 ГJ = 172,8 ГJ х 0,24 (Гcal/ГJ) = 41,47 Гcal; Heat losses’ intensity for all area of green house building(s) – 200 (J/s) х m^{-2 }х 10000 m^{2} = 2 МW. Average power for heat supply – 2 МW.
Wind power: Average power of wind turbine at duration of wind 10 hours per day is (2 МW х 24 h)/10 h = 4,8 МW. Average wind power that fall on 1 m^{2} area, perpendicular to wind flow direction and wind velocity of 7 m/s per 1 s is 0,5 х 1,2(kg/m^{3}) х 7^{3} (m/s)^{3} х 1 m^{2} = 206 J = 206 J х 0,24 cal/J = 50 cal. Specific WPT power is 206 W. During an hour 1 m^{2} of useful wind flow area produces 0,206 kWh = 0,206 kWh х 860 kcal/kWh = 177 kcal. During a day – 10 х 0,206 kWh = 2,06 kWh = 2,06 kWh х 3,6 МJ = 7,4 МJ = 7,4 МJ х 0,24 (Мcal/МJ) = 1,78 Мcal. Area of wind flow cross section А, that provides power of 4,8 МW is 4,8(МJ/s)/[0,5 х 1,2 (kJ/m^{3}) х 7^{3}(m/s)^{3}] = 23301 m^{2}. Wind flow with the area of cross section of 23301 m^{2} can be taken, for example, with 2 wind turbines (every one takes of 11660 m^{2} and has length of turbine’s blades of 60 m.
Heat accumulator: Heat quantity, stored by 1 m^{3} volume of water with a specific heat capacity 4,2 kJ/(kg·°C) when heating from 20^{0}C to 70^{0}C 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 172,8 GJ per day is 172,8 GJ/0,210 GJхm^{-3} = 823 m^{3}.
By Vasil Sidorov on October 15, 2012
Technopark QUELTA, Queltanews from
Nizhyn Laboratories of Scanning Devices
sidorovvasil@gmail.com