In this work, the impact of using Renewable Energy Source (RES) generators in next-generation (5G) cellular systems on total power consumption (PC) has been investigated. The paper highlights the gain related to the use of photovoltaic (PV) panels and wind turbines (WTs) in the form of two factors - the average extension of battery lifetime (AEBL) powering a single network cell and the average reduction in energy consumption (AREC) within the whole network. The examination has been conducted for four different seasons of the year and various configurations of available power sources. The provided system scenario was based on real data on weather conditions, building placement, and implemented mobile networks for the city of Poznan in Poland. Used RES generators were designed in accordance with the specifications of real devices.
, EBATT (t) (cid:19) , (11) where BATT and EBATT,max are the efficiency of the used battery type and maximum energy the battery system is able to collect, respectively. The latter is equal to EBATT,max = NBATTE BATT,max is the maximum energy of a single battery, and NBATT = NBATT,sNBATT,p is the total number of accumulator units in a battery system. The parameters of NBATT,s and NBATT,p are the numbers of batteries linked to each other in serial and parallel order, respectively. To evaluate the current energy balance (E), the formula below was engaged: BATT,max, where E E (t) = (cid:32) PPV (t) + PWT (t) PMIMO (t) 1 DC (cid:33)(cid:32) t t (cid:33) , (12) where DC is the loss factor related to DC supplying the hardware parts of the network cell.
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E. Atmospheric Parameters Finally, let us collect all auxiliary formulas used to calculate necessary atmospheric parameters. To approximate the actual speed of wind (vw) at the specific altitude h in the time step t, the following mathematical equation can be used : vw (t, h) = vw (t, hWS)
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The air density () at the altitude h and in the current time step t can be calculated as follows : (t, h) = (14) pd (t, h) Rd (cid:0)Ta (t, h) + 273.15(cid:1) + pv (t, h) Rv (cid:0)Ta (t, h) + 273.15(cid:1) , where Rd and Rv are the specific gas constants for dry air and water vapor, respectively. Next, pd and pv are the pressures of dry air and water vapor. The latter at the altitude h and in the time step t can be expressed by the formula : pv (t, h) = 6.1078 10 7.5Ta(t,h) Ta(t,h)+237.3 , (15) The pressure of dry air at the same altitude and moment has been described by pd (t, h) = p (t, h) pv (t, h), where p is the air pressure evaluated as : p (t, h) = p0 (t) e g(h)M (h+hTh0) RTa (t,h) , (16)
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It was assumed that the reference level is the sea level altitude (h0 = 0 ). Next referring to , the gravitational acceleration r2 (re+h)2 , where g0 and re are the sea is described by g (h) = g0 e level acceleration and mean radius of the Earth, respectively. Finally, the formula to calculate the ambient temperature (Ta) at the altitude h and moment t is shown below : Ta (t, h) = Ta(t, hWS) 0.0065 (h + hT hWS) . (17)
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