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UDC 662.997: 662. 93(44)
Salamov O.M., Salmanova F.A. Institute of Radiation Problems of Azerbaijan National Academy of Sciences
9 B. Vahabzade str., Baku Az 1143, Azerbaijan DOI: 10.24412/2520-6990-2022-8131-11-22 AN INVESTIGATION OF SUPPLY OPPORTUNITIES OF HEAT LOAD BY SOLAR AND WIND POWER SOURCES TO PROVIDE HEATING AND HOT WATER OF THE PRIVATE HOUSES
Abstract
The main purpose of this work is to study the mechanism of year-round change of heat load (HL) required for heating (HS) and hot water supply (HWS) of a single-family house located in Baku and to explore supply opportunities of this HL together with using solar and wind energy. Considering the mechanism of change of daily and monthly amounts of HL, the types of solar and wind energy sources with appropriate energy characteristics were selected. Currently, flat solar collectors (FSC) are used as a solar energy source, and the A WPP-6-4M type wind-electric unit (WEU) with a wheel diameter of 6.6 m and an output power of 4.0 kB is used as a wind energy source. To solve the problem, the daily, monthly and annual amounts of total HL of the experimental individual house required for HS and HWS were determined. Moroever, the daily, monthly and annual changes in the energy performance of both energy sources in different climatic conditions observed in Baku were studied and appropriate graphical dependencies were established.
Keywords: Flat solar collector, wind electric motor, hot water, heat supply, hot water supply, heat load, solar radiation intensity, average wind speed, instantaneous wind speed, output power, gas meter, electricity meter
1. Introduction
Analysis of the literature and many years of research shows that the share of energy used for heating supply (HS) and hot water supply (HWS) in the total energy balance used by the population in all countries of the world is more than 50% [1-5]. The transition to nanotechnology and the creation of a variety of energy-efficient electrical equipment each year, in particular technological breakthroughs in communications, the transition to mobile and satellite communications systems, which require thousands of times less energy than previous systems, Jouled lead to a significant reduction in the relative share of electricity in the
overall energy balance in the future, and the share of HS and HWS can even reach to 70%, which as a rule, different organic and synthetic fuels like oil, gas, coal, etc. are used .
On the other hand, firewood is still used as a fuel in rural areas, and it takes 20-30 years to restore felled trees. It should be noted that the use of all these fuels significantly damages the ecology of the Earth and the Earth's atmosphere, which in turn leads to the use of these fuels in the greenhouse (CO, CO2, etc.) and other (SO2,). NO2, NH3, etc.), which can combine with water vapor in the atmosphere to form toxic substances. Therefore, in recent years the climatic conditions are
not typical for the current season in different parts of the world. For example, snowfall in spring or forest fires in winter, as well as acid and alkaline rains etc., which cause serious damage to both flora and fauna. Moreover, the natural disasters, such as tsunamis, river floods, floods, floods, mass droughts, landslides, etc. have occurred in many parts of the world due to the violation of the thermal balance of the atmosphere, such as tsunamis, overflow of rivers, floods, flooding of residential areas, massive global droughts, landslides etc, have occurred in many parts of the world due to the violation of the thermal balance of the atmosphere.
Currently, most fuels such as natural gas, fuel oil, diesel fuel and coal are used for electricity generation, which contributes to the deepening of the environmental crisis. It's known that a large part of the total energy demand in private and public housing, hospitals, boarding houses, schools, kindergartens, catering facilities, wedding halls, military facilities, as well as in many public institutions is due to the using above-mentioned fuel types. Therefore, in order to gradually reduce dependence on these harmful fuels, it is extremely important to meet at least half of these demands at the initial stage through environmentally friendly and inexhaustible alternative energy sources, in particular, solar and wind energy. First of all, both
N1, N2, N3, N4, day; T1, T2, hours
36 32 28 24 20 16 12 8 4
types of energy must have sufficient reserves in a particular place in order to efficiently use these types of energy. Azerbaijan is one of the world's leading countries in terms of solar and wind energy reserves. Figure 1 shows the average monthly values of fully clear (N1), semi-cloudy (N2), fully cloudy (N3) and working (N4) days for Baku, as well as the number of working days during the day without considering (Ti) and considering (T2) the number of cloudy days. The average monthly values during the year are described graphically. As can be seen from Figure 1, in Baku, which covers the northern latitude 40024I, the number of sunny days per year is 242, the number of semi-cloudy days is 72, and the number of sunless (full cloudy) days is 51. Thus, the total number of working days during the year is 314 days in Baku. Average annual sunshine hours up to 3000 hours, the amount of solar energy per m2 of horizontal surface per year 1900 kWhm2/hour, maximum value of the intensity of solar radiation (ISR) per m2 of horizontal surface per day 950 W m2, and the average annual value of this indicator is up to 200 W/m2. The duration of uninterrupted operation of solar power plants during the day is 4.8^12.5 hours and more (during the summer months) depending on the purpose and season [6].
<'X-Xs /
< / \ x
X / Q > <
/1
i-a-c
2
rCf /5
3 6
6 8
10 12 14k
Months
Figure 1. Average monthly values of fully clear (N1), semi-cloudy (N2), fully cloudy (N3) and working (N4) days for Baku, as well as the number of working days during the day without considering (T1) and considering (T2) the number of cloudy days: curves 1, 2, 3, 4, 5 and 6, respectively e
0
2
4
As for wind energy resources, based on long-term measurements, research and generalizations, it was found that the number of days with instantaneous wind speeds exceeding 8 m/s in the Absheron Peninsula, as well as Baku and the Caspian Sea is 280 days. The average annual wind speed is 6 ^ 8 m/s in most places, and even more than 10 m/s in some small areas. This is sufficient for the stable and reliable operation of both small (up to 100 kW) and large-capacity (in MW) WEUs designed for parallel operation with the power grid. The estimated annual reserves of wind energy in the total area of Azerbaijan are ~5.41012 kWh.
However, if we clonsider that the main part wind resources of Azerbaijan is concentrated in zone A [4, 7, 8], where, as mentioned above, only the Absheron Peninsula and the Caspian Sea fall into a narrow zone, then the last indicartor of annual wind energy reserves decreases significandtly. However, this is a huge energy potential and shouldi be used to the maximum.
From all this, yit is clear that the use of solar and wind energy in private homes in the Absheron Peninsula, as well as in Baku for HS and HWS purposes is entirely expedieant from an energy point of view. Since the production of thermal energy is not observed
by the combustion process, no harmful emissions and toxic gases are released into the environment, the use of these energy sources is environmentally efficient.
Considering this, relevant investigation was carried out in the "Laboratory of conversion of renewable energy types" of the Institute of Radiation Problems of ANAS, a combined solar and wind power plant (CSWPP) for individual HS and HWS purposes has been developed and tested for several years. In the presented work, the detailed study of the possibility of providing the experimental individual dwelling selected using this device with sustainable heating and hot water throughout the year.
2. Research method
A private house in Baku was taken as an experimental house. The total area of the house is 60 m2, and the number of permanent residents are 5 people. During the experiments, the temperatures of hot water and air in the rooms were kept at a constant level at 55 0C and 22 0C, respectively, while the temperatures of cold water and ambient air varied over a wide range.
In order to determine the daily, average monthly and annual amount of total HL required for HS and HWS, monthly indicators of gas and electricity meters installed in the experimental house were recorded and
annual gas and electricity consumption graphs were plotted based on the obtained indicators (Figure 2). It was determined that the average monthly and annual electricity consumption was 316.3 kWh (1,139 GJ) and 3796 kWh (13,665 GJ), respectively.
The daily and monthly amount of HL required for HS and HWS was determined considering the amount of heat given by 1 m3 of natural gas during combustion. As it is known, if we do not take into account the effect of water vapor, then the maximum heat energy of 1 kmol of methane gas during combustion is 891 MJ/mol. Moreover, since the volume of 1 kmol of gas is 22.4 m3, the combustion temperature of 1 m3 of methane gas is 891/22.4 = 39.78 MJ/m3 [9,10]. Considering this, the monthly values of the total HL of the experimental house were determined using the following empirical formula:
Qmonrny = 39J8Clgas, (1)
Where, C - monthly gas meter, m3; ngas -coefficient of performance of gas heater, part of the unit (varies in the range of 0.5 ^ 0.6).
1) It was considered that ngas=0,55 when calculating according to formula (1).
Q
gasmeter.
700 600 500 400 300
, m3, E,^
' ' el .meter
kWh
200 100
.2
0
2 4 6 8 10 12 14
Months
Figure 2. Graphs of the annual course of changes in energy consumption, in an experimental individual dwelling house, registered by means of gas and electric meters: 1- gas consumption; 2- consumption of electrical energy
Then, using the curve 1 and formula (1) described in Figure 2 and considering the coefficient of performance of the gas appliance used by the consumer,
the daily Q^^ and monthly Qmothly of the total HL
required for HS and HWS, separately the average
monthly PaVrage values of total power required from
energy sources have been determined in order to meet
t z^daily s^daily * t /Omonthly
the daily QHWys, QHSy and monthly Qнwsy,
QmOnthly of the HL required for HS and HWS, as well as the QZnMy of the total HL. In order to determine
the daily and monthly values of the required HL for HS, the amount of daily and monthly HS required for hot water were first determined.
In this case, in order to obtain more accurate
results, instead of t^^ = 15 C for cold water
temperature, as in previous calculations [3], the
relevant average monthly values taemothly observed
for many years in Baku for each month were taken, which are given in Table 1. . The hot water temperature
was kept constant (tAoi w = 55 C) for all months [9].
Daily HL values for HWS were determined from the following formula [1,3,9]:
QW = aPCpm (thot. tZa7"tky ), (2)
where - a is daily norm of hot water per capita, l/day (in this case a = 80 l/day); p - density of water,
kg/l (p = 1 kg/l); Cp = 4190 Goul/(kg0C) - specific heat capacity of water; m - number of residents living in the house, people (m = 5).
Table 1
Average monthly temperatures of cold water in the centralized water line ___in Baku for many years __
Months I II III VI V VI VII VIII IX X XI XII
,ave. monthly tc. wat. , C 11 11 12 14 16 18 18 18 16 14 12 11
Then, by multiplying the daily indicators for each month from formula (2) by the number of days in that month (N), the monthly values of HL required for HWS
are Q
monthly HWS
formulas, the daily HL for HS is Qd^ y and monthly
Q
month y HS
values are determined:
Ôdaily _s^daily s^daily ^ monthly _ u daily
HS ~ QTot ~ QHWS ' QHS ~N QHS ,
(3)
and using the following empirical 2
The results of the calculations are given in Table
Table 2.
Daily and monthly values of total HL required for HS and HWS, and separately HL required for HWS and HS, as well as average monthly values of total power required from energy sources to provide total
HL
Parameter s Months Monthl y average
I II III IV V VI VII VIII IX X XI XII
daily QTot > 423, 5 422, 6 388, 1 292, 0 105, 9 72,9 63,5 63,5 72,9 84,6 218, 7 317, 6 229,1
m monthly QTot > 13,1 3 12,2 6 12,0 3 9,19 3,28 2,19 1,97 1,97 2,19 2,62 6,56 9,85 6,44
gj daily QHWS > 73,7 4 73,7 4 72,0 7 68,7 2 65,3 6 62,0 1 62,0 1 62,0 1 65,3 6 68,7 2 72,0 7 73,0 4 68,23
m monthly QHWS > 2,21 2,07 2,23 2,06 2,03 1,86 1,92 1,92 1,96 2,13 2,16 2,21 2,06
GJ oaily QHS > 349, 8 348, 9 316, 0 223, 3 40,5 10,9 1,5 1,5 7,5 15,9 146, 6 244, 5 142,2
m monthly QHS > 10,9 2 10,1 9 9,8 7,13 1,25 0,33 0,05 0,05 0,23 0,49 4,4 7,64 4,37
j ave .monthly 1 e.s. 17,6 5 17,6 1 16,1 7 12,1 7 4,41 3,04 2,65 2,65 3,04 3,53 9,11 13,2 3 8,77
A s can be seen from the table, in the experimental house, in fact, the average monthly electricity consumption for HWS is ~ 1.81 times, the energy consumption for HS is ~3.84 times, and the total monthly energy consumption for HS and HWS is ~5.66 times higher, which is very well consistent with the data in the literature [1-5,9].
Considering these, CSWPP for HS and HWS of the experimental individual dwelling house was created and tested in the natural conditions of Baku, which uses 8 SPL type FSCs produced in Sumgayit Technologies Park with an area of 2.4 m2 each as a solar energy source, and two-winged, horizontal rotating AWPP-6-4M type WEUs was used as wind power source.
Taking into account the indicators given in Table 1, the constructive and energy characteristics of FSC and WTM used in the experimental CSWPP were determined.
FSC has the following technical characteristics: dimensions - 1993x1220x90; weight - 41 kg; operating pressure - 6 bar; maximum test pressure - 10 bar; vertical pipes - copper 010; horizontal pipes - copper
0 25; heating plate - 1150x0,2 selective; glass -tempered; welding - ultrasound; total liquid capacity of pipes - 2.6 l; heat resistance - + 236 0C.
WTM has the following technical characteristics: maximum output power - 4 kW (14.4 MJoule/hour); diameter of wind wheel (WW) - 6.6 m; number of wings -2; operating range of wind speed, where the rated power of the electric generator is provided - 4.5 ^ 25 m/s; the rotational speed of the WW under the nominal load and at the operating speed of the wind -230 rpm; the value of wind speed required to obtain the nominal rotational speed of the WW in no-load mode -5 m/s; method of regulating the rotational speed of the WW - dynamic-centrifugal; wind direction system -using an endless screw-type reducer and a winding wheel; multiplier - cylindrical, two-stage; type of electric generator - MWTSG (modernized wind turbine synchronous generator) - 4 - 91/1500 type synchronous generator; wiring diagram of electric generator windings - neutral grounded star; rated power per phase - 1.3 kW; rated output voltage - 400/230 V; current frequency - 50 Hz; difference of current frequency from
50 Hz at minimum and maximum operating speed of wind ± 5 Hs; rotation speed of the rotor of the electric generator - 1500 rpm; amount of daily energy produced in places where the average annual wind speed is not less than 6 m/s - 30 kWh (108 MJoule); height of the mast - 9.6 m; maximum allowable wind speed - 50 m/s; uninterrupted life time - 30 years.
In order to increase the efficiency of the plant, as well as the reliability of the consumer's supply of heat and hot water, WEU was taken as the main energy source in the experimental plant. In order to derive the characteristics of the output power and the frequency of the current generated by the electric generator from the instantaneous wind speed, the WEU was tested naturally in different wind modes. In order to ensure the safe operation of the electric generator when plotting the wind speed dependence of the output power of the WEU, the value of the electric load was changed accordingly during the time when the rotational speed of the WW was obtained (when the wind speed varied between 4 ^ 9 m/s).
It was found that when at wind speeds below 7 m/s, the output power of the WEU is significantly reduced, and when under load it reaches its nominal output power only at constant wind speeds above 9 m/s. Then (at values of instantaneous wind speed in the range of 9 ^ 25 m/s), by automatically changing the current flowing through the excitation winding of the electric generator, the output power of the WEU is regulated and its value reaches the maximum allowable wind speed. For this purpose, the methods of automatic change of the attack angles of the wings of the WW in accordance with the change of wind speed and sequential action of the generator are applied.
When the wind speed reaches the maximum allowable limit (in this case, Vmax = 25 m/s), the electric generator is automatically disconnected from the impact current circuit and the load (the role of this load is played by the electric heater on the CSWPP). The minimum frequency of the alternating current when the generator is switched on and off is 35 Hz and 16 Hz, respectively.
In Table 2, to explore the feasibility of providing the total HL required for HWS and HS during the year, it is necessary to determine the daily and monthly energy production of both energy sources, ie both WEU and FSC. Since this problem is very difficult to solve in practice, this energy production is usually determined theoretically (by calculation), considering the solar and wind potentials at the research site.
When theoretically determining the daily, monthly and annual energy production of WEU, the calculations are usually based on the average monthly and average annual wind speeds [4, 5, 8, 11, 12], but the results obtained in this way are very large due to the fact that the calculation error is very large. Therefore, for this purpose, for different values of average monthly wind speeds, taking into account the coefficients of repetition of different gradations of its instantaneous speed during the month and year gives more accurate results. Although these ratios are given in the literature in the thousandth system or as part of a unit, in fact, these ratios show how many hours a day, month and
year the WEU can operate in optimal mode (with nominal output power) at different values of instantaneous wind speed [8, 9 ].
The report considered the wind regimes currently observed not only in Baku, but also in the suburbs, a few km outside the city, in order to ensure that the total HL required for both HS and HWS purposes of the experimental individual dwelling can be sustained throughout the year, where situated majority of individual houses, villas and cottages. In this case, according to Grinovich's classification, the indicators of the Absheron-lighthouse meteorological station, where the shading conditions can be attributed to the 5th class, were considered. This is explained by the fact that over the past 20 years, a large number of high-rise residential buildings (above 17 floors), hotels, etc. have been built in Baku, and now the wind regime in residential areas has changed significantly compared to the surrounding areas. Thus, due to the fact that the residential buildings, built perpendicular to the North-South direction and more than 50 m in length, shade each other, the speed of wind flow between these buildings has sharply decreased. Otherwise, a very high turbulent wind flow occurs between the two buildings, which are located in parallel to the North-South Poles. However, it is not possible to install WEUs in these areas, in particular WEUs with horizontal axes of rotation. On the other hand, in recent years, individual houses in Baku, even five-storey houses from the former Soviet era, have been demolished and replaced by high-rise buildings, and this trend will continue. Therefore, the individual use of WEUs in the territory of Baku for any purpose, including HS and HWS is not so important.
In view of all this, in order to more accurately calculate the daily, monthly and annual energy production of the WEU was tested naturally near the site of the Apsheron-lighthouse station and its output power was plotted according to the instantaneous wind speed (Figure 3). When determining the output power of the WEU based on the relative strength of the wind flow entering the single surface of the WW, even at wind speeds below 4 m/s, it is alleged that the WEU produces a significant amount of energy [11,12] and if we take into account that at the average monthly wind speeds of 6 ^ 8 m/s, the repetition time of the instantaneous wind speed in 0-4 m/s gradations is much longer than in other gradations, then the value of this error is also significant. Moreover, at wind speeds above 9.0 m/s, the output power of the WEU is virtually stabilized and maintained at the established nominal level. Therefore, if we determine the amount of energy produced by the WEU on the basis of the characteristic of the dependence of the specific power on the wind speed, we can get results that do not show the reality. According these, we considered it more appropriate to determine the output power of the WEU at the Absheron-Mayak metro station, taking into account the coefficients of repetition of different gradients of instantaneous wind speed and using the power curve shown in Figure 3.
Figure 4 shows the iteration curve of different gradients of instantaneous velocity during the year (in
hours) for the average annual wind speed of 7.88 m/s at the Absheron-lighthouse station. Since WEU does not operate at wind speeds below 4 m/s and above 25 m/s, and at rated output power in the range of 9-25 m/s wind speed, when determining the amount of daily, monthly and annual energy it produces it is important to consider this.
For this purpose, using Figure 4, for the values of wind speed (V < 4 m/s), V = 4 ^ 9 m/s, V = 9 ^ 25 m/s and V > 25 m/s, the corresponding values of the repetition coefficient of its instantaneous speed, determined from the following empirical formula:
K =Tl /Tmax , (4)
where, T - the period of repetition of the relevant instantaneous wind speed during the year, hour (Can be determined from Figure 4); T - the number of hours
during the year, hour (Tmax = 8766 hours).
The repetition coefficients determined by formula (4) are used to determine the monthly, daily and annual energy production of the WEU, as well as its average monthly capacity.
However, in order to increase the accuracy of the calculation, it is necessary to use other statistical parameters, which are determined from the following empirical formulas, considering the number of days of the month and the average monthly wind speed:
iy month t t month /t t KV -Vave lVc r month
annual
Kmonh = N month I N
month ave
Pexp kW
1 WTM , k W
2 4 6 8 10 12
V, m/s
Figure 3. Graph of experimental dependence of the output power of A WPP-6-4M type WEU on wind speed
t^ month t^ month t^ month K adj - KV • KT > (5)
where, K month - the coefficient that distinguishes the average monthly wind speed from its average annual speed, part of the unit; vmonth - average monthly wind speed, m/s (for Absheron-lighthouse station is
• r-r-1 i i tf annual i • j j
given in Table 3); V me - average annual wind speed,
m/s (for Absheron-lighthouse station - ya""ual = 7.88
m/s); Kmonth - coefficient that distinguishes the real number of days of the month from the average monthly number, part of the unit; Nmmth - the real number of
days of the month, days (for the February - Nmmth =
28.25); N'm0'th - average number of days of the month,
days (Nmr = N annual / 12 = 30,417); Kj -
monthly value of the adjustment factor, part of the unit.
Table 3 shows the repetition periods of different gradations of its instantaneous velocity V for years
and days (respectively, KO""11" and KTm y) and the repetition coefficient ( K ) corresponding to those
periods for the value of the average annual wind speed of 7.88 m/s, which are used during report.
Kt, hours 800 700 600 500 400 300 200 100
0
4 8 12 16 20 24 28 32
Vmst., m/s
Figure 4. Repetition curve of different gradations of its instantaneous speed during the year for the average annual wind speed of 7.88 m/s at Absheron-lighthouse station
4
3
2
Table 3 also shows the estimates of the output power of the AWPP-6-4M type WEU at different instantaneous wind speeds, which is determined from the graph of its output power depending on the wind speed during a natural test near the Absheron-Mayak station (Figure 3) and the units of measurement are expressed in MJoules/hour (1 kW = 3.6 106 Joule/hour). Given that the calculation of daily,
monthly and annual energy production of WEUs by reporting only on the basis of the average annual wind speed and the optimal output power of WEU leads to large errors. The report is based on a special method, considering the values of the real power of the WEU in different gradations of instantaneous wind speed given in Table 3 [8,9].
Table 3
For the value of the average annual wind speed of 7.88 m/s, the repetition times of different gradations of its instantaneous speed during the year and day and the values of the repetition coefficient corresponding ___to those periods ____
V, m/s < 4 4 5 6 7 8 9-25 > 25
Ki, part of unit 0,233 0,083 0,08 0,076 0,07 0,065 0,387 0,0056
annual . KT , hours 2042,0 727,4 705,6 666,2 613,6 570,0 3392,2 49,0
daily . KT , hours 5,592 1,992 1,920 1,824 1,680 1,560 9,288 0,134
P^ev , MJoule/hours 0 0,54 1,80 3,42 5,58 9,36 14,4 0
t^annual «. . Eweu , Gj°ule 0 0,393 1,270 2,278 3,424 5,335 48,848 0
EWeu , Mjoule 0 1,08 3,456 6,239 9,374 14,601 133,74 0
The calculated values of the annual Ea^U"' and
daily E^Éu energy produced by WEU in different
gradations of wind speed are given in Table 3. As can be seen, the annual energy production of WEU is 61,548 GJoule, the average monthly energy production is 5,129 GJoule, and the average daily energy production is 168.5 MJoule. This means that the average capacity of the WEU is 9.22 MJoules/hour
during the working day ( Tdlly = 18,276 hours).
However, as shown in Table 3, the WEU operates at rated output power (14.4 MJoule/hours) for more than half of the daily operating time (9,288 hours).
Monthly numerical values of coefficients K}
Since the parameters given in Table 3 are determined only considering the coefficients related to the average annual wind speed (7.88 m/s), ie the average monthly wind speeds, as well as the number of operating hours during the month, the amount of monthly energy production of WEU not specified. In order to determine the monthly indicators, it is necessary to take into account the numerical values of
the coefficients K
month
K
month
and K
month adj
month
determined according to the formula (5), which are given in Table 4.
Table 4
month month
K and K determined according to the
formula (5)
Parametrlar Months Averag e annual
I II III IV V VI VII VIII IX X XI XII
t r month , Vave > m/s 7,6 8,4 8,8 8,0 7,6 7,6 7,8 8,0 7,6 7,7 7,6 7,8 7,88
month KV , p.u. 0,96 5 1,06 7 1,11 7 1,01 5 0,96 5 0,96 5 0,99 0 1,01 5 0,96 5 0,97 7 0,96 5 0,99 0 1,0
month KT , p.u. 1,01 9 0,92 9 1,01 9 0,98 6 1,01 9 0,98 6 1,01 9 1,01 9 0,98 6 1,01 9 0,98 6 1,01 9 1,0
month Kd , p.u. 0,98 3 0,99 0 1,13 8 1,00 5 0,98 3 0,95 1 1,00 9 1,03 4 0,95 1 0,99 6 0,95 1 1,00 9 1,0
month eweu > GJoule 5,04 2 5,07 8 5,83 7 5,13 4 5,04 2 4,87 8 5,17 5 5,30 3 4,87 8 5,10 8 4,87 8 5,17 5 5,127
T^daily EWEU > MJoule 164, 8 179, 7 188, 3 171, 1 162, 6 162, 6 166, 9 171, 1 162, 6 164, 8 162, 6 166, 9 168,5
-pave.annual PWEU > MJoule/hou rs 8,90 9,84 10,3 0 9,36 8,90 8,90 9,13 9,36 8,90 9,01 8,90 9,13 9,22
, MJoule/(m2• hour); t^, 17cut,
0c so
25 20 15 10 5
0 2 4 6 8 10 12
Months
Figure 5. The change in the daily average values of the total ISR per 1 m2 of sloping surface, the temperature of
the heat carrier at the input of the FSC, as well as changes in the average monthly temperature during the year in Baku: curves 1, 2 and 3, respectively.
From Table 4, if we determine the amount of annual energy produced by WEU, then E""""™1 61,527 Gjoule which differs from Table 3 by only 21 MJoules (0.034%). This indicates that the coefficients
K, K
annual T ,
K
daily
K
monthly V 9
K
monthly
T
Y9
Km;;thly are determined with high accuracy for
different gradations of instantaneous wind speed. This allows us to clarify the role of WEU in providing the consumer with reliable HS and HWS during day and month.
The total surface area of the SPL type FSC used in the experimental CSWPP is 19.2 m2. Data on the total ISR in the territory of Baku city were used to determine the thermal energy parameters of FSC [3, 6].
Figure 5 graphically shows the change in the
= average monthly values of the total ISR (IdT""ly) per 1
m2 of sloping surface of the FSC per day, the temperature of the heat carrier (currently water is used
for this purpose) at the input (t'^P") of the FSC, as well as the air temperature (t^r) typical for Baku.
When determining the average monthly values of ISR per day per 1 m2 of sloping surface of FSC, the average monthly numbers of clear (N1), semi-cloudy (N2), full cloudy (N3) and operating (N4) days which typical for Baku were considered from Figure 1. During the calculations, the temperature of the heat carrier at the output of the FSC was assumed to be constant,
„„ monthly 1
rjp^, , arb. un.
t
output _ - -0
HC
= 550C.
Months
Figure 6. Schedule of change of average monthly c. o.p. of FSC during the year
Since the use of package-type double glazing as a W/(m20C), which is the factory value of the FSC for protective layer in the FSC, the total heat loss normal operation. coefficient from them was taken as t/Afas= 6
The following formula was used to determine the average monthly values of the efficiency (c.o.p.) of the FSC:
rf^ = 0,8
0-
8U(H -tair)
I
daily SS
(6)
where, 0 - the optical characteristics of the FSC,
part of the unit, (0 = 0.8 was adopted for FSC with
selective coated heating plate); t^ - is the average
numerical value of the temperature of the heat carrier in the contours of the FSC, 0C, which is determined from the following formula:
Cr = 0,5 ( t
input . J output x
+ ' un A (7)
lHC
The average monthly values of t^ for FSC used on the experimental device are given in Figure 5.
Based on the results obtained from the report, a graph of the average monthly values of the efficiency of the FSC for the year has been established, which is described in Figure 6.
A number of thermal energy parameters of FSC were detemined from Figure 5, considering the monthly
average values of I
daily SS
and t^r, and from the Table
5, considering average monthly value of t^.
Moreover, the thermal energy parameters of CSWPP were determined considering monthly average value of
E^jj and EmOu1 from Table 4, which results are
given in Table 6. Calculations were performed according to the methods previously proposed by us [3,8,9]
Table 5
Average numerical values of the heat carrier in the contours of the FSC taken for the report
Parameters Months
I II III IV V VI VII VIII IX X XI XII
fave 0p lHC ' C 35,5 35,5 36,0 37,0 38,0 39,0 39,5 39,0 38,0 37,0 36,0 35,5
As can be seen from the table, the maximum value of energy produced by FSC is observed in June (7.02 GJoule), and the minimum value is observed in January (1.42 GJoule). Unfortunately, the monthly values of the total HL required for HS and HWS, by contrast, reach a minimum in the summer (1.97 GJoule) and a maximum in the winter (for example, 13.13 GJoule in
January). Therefore, WEU plays a key role in ensuring the overall HL in the winter season, with the average monthly minimum and maximum values of energy production differing from each other by 5,837/4,878 = 1.2 times (~ 20%), whereas for FSC, this indicator is 4.94 times.
Table 6
Results from the thermal energy balance report of CSWPP used for HS and HWS purposes
Parameters
II
III
IV
V
Months VI VII
VIII
IX
X XI
XII
Ö daily FSC ■
45,7
99,7
163,
202,
217,
234,
225,4
221,0
196,
184,
100,
55,4
Ö monthly FSC ■
1,42
2,79
5,08
6,05
6,72
7,02
6,977
6,851
5,86
5,70
3,01
1,71
_a_
Ö, monthly FSC+WEU ■
6,64
7,38
10,9
11,1 _o_
11,7
_a_
11,9
_a_
12,15
12,15
10,7 _£_
10,8 _J_
7,89
6,84
q,
monthly tot '
13,1
_2_
12,2
_£_
12,0
_2_
9,19
3,28
2,19
1,97
1,97
2,19
2,62
6,56
9,85
mocthly qFSC +WEU ■
+2,0
+8,4
_o_
+9,7
_J_
+10,1
+10,3
+9,9
_c._
+8,1 _o_
+1,3
mcnthly
ytf-FSC
1,42
2,79
5,08
6,06
3,28
2,19
1,97
1,97
2,19
2,62
3,01
1,72
) monthly ) qFSC
3,45
4,83
5,01
4,88
3,68
3,08
, ^ monthly ( HWEU
5,04 _d_
5,07
_Q_
5,83
_O._
3,13
_3_
3,54
_o._
5,17 _£_
/ monthly \ viwEU ^ loss
2,00
5,04
4,88
5,18
5,30
4,88
5,11
1,33
I
Q
i
L_J_U
1 ^ <•>
J_J_J
Q
H
J
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Note: In Table 6: Q^c - the amount of thermal energy produced per day by the inclined surface FSC, MJoule; Qm0"thlj - the total amount of thermal energy
produced by FSC in a month, GJoule; Q-
monthly
■ the
total amount of energy produced by FSC and WEU together during the month, GJoule; Qm0"thlj - average monthly value of total heat load required for HS and
HWS, GJoule; q
monthly
- the difference between
total HL and monthly values of energy produced by FSC and WEU during the month, GJoule;
(qmOCtMj )e/fec - effectively used part of the monthly
energy produced by FSC, GJoule; (qmscMy\ost - the lost portion of the monthly energy produced by FSC, GJoule; (qWv°Eijly - the part of the energy produced by the WEU used to cover the total HL, GJoule; (qWEu" )i°ss - the unused (lost) part of the energy produced by WEU for HS and HWS, which can be used
to provide with electric power of the experimental house, GJoule.
All this shows that the use of individual apartments for HS and HWS purposes separately is not very effective. Thus, although in January they were only able to pay 10.68% of the total HL in January, in the summer, when there is no heating season, the total HL decreases sharply, while the heat produced by the FSC up to 69% of its energy remains unused as it cannot be converted to other forms of energy. As for the energy produced by WEU, this energy is fully used in December, January, February and March, ie in the winter season, when the total HL is maximum. During April-November, most of the total HL is not used for the energy produced by the WEU, as it is provided by the FSC (especially in the summer season). However, this should not mean that its energy is not used unequivocally in the summer, as in FSC. Thus, since the type of energy produced by WEU is more universal in terms of usability, it can provide electricity to all types of power operators during the summer season. Since the current study focuses only on HS and HWS, we are not exploring the possibility of using the remaining part of the energy produced by FSC and WEU in the summer to cool that dwelling, although at least the energy produced by WEU can be fully used for this purpose.
In winter, even in the worst weather conditions, which are not very typical for Baku (when the air temperature is tair = - 5 0C), the difference between the indoor and outdoor temperatures is 23.50C, as the temperature required to be kept constant inside the rooms heated by FSC and WEU is +18.5 0C. In contrast to the winter season, when the room temperature is maintained at 24 0C in summer, the above-mentioned temperature difference is still 21 0C, even when the air temperature reaches +45 0C, which is 2.5 0C less than in winter. In this case, the main problem that needs to be addressed is to select the output power of the WEU, taking into account the maximum value of the total HL, in particular observed in the winter season. If this decision is made correctly, CSWPP, which can provide
the total HL needed for HS and HWS in the winter, can provide the house with both hot water and electricity in the summer. As can be seen from Table 6, in the present case, ie when using WEU with a nominal output of 4 kW, the total energy required for HS and HWS in December, January, February and March is the energy produced jointly by FSC and WEU. can't provide (
qfsc+wvm gets a negative value). Therefore, it is necessary to use an alternative energy source in those months, for which gas or electric heaters can be used.
Analyzing the parameters given in Table 6, it seems that it is not profitable to take the total surface area of the FSC larger than it is now in order to provide the consumer with stable heat and hot water in winter. It is true that the demand for hot water increases significantly (100 + 150 l/day per capita) due to more frequent hot showers in the summer, but even in this case, part of the thermal energy produced by FSC remains unused. Therefore, in the current situation, it may be more expedient to use for this purpose 6 units of the same type with a total surface area of 14.4 m2. However, in this case, it is necessary to use a WEU with a nominal output power of 8 + 10 kW. It is possible to convert the remaining part of the thermal energy produced by FSC into electricity through an appropriate energy system. In this case, FSC can be used not only to heat apartments, but also to cool them in the summer. However, it is not advisable to use multi-stage energy conversion systems in such small-capacity CSWPP for individual purposes, and in this case, the higher the output power of the WEU compared to the total capacity of the CSWPP, the better.
On the other hand, since the average monthly electricity demand of an experimental individual dwelling house is 316.3 kWh (1,139 GJoule), WEU provides with electricity in a sustainable way for additional 3+4 individual dwellings with the same number of family members and energy requirements during the summer.
Mfsc , Mweu , №tot , №gas ' arb
un.
0 2 4 6 8 1 1 0 , 2 months
Figure 7. The changes in the monthly average numerical values of the energy supply coefficient for
the year, showing the share of FSC, WEU and alternative energy source (gas heater) in the energy supply of the experimental individual house separately and together:
1 - MfSC ; 2 - №wTM ; 3 - № gas .; 4 - Mtot
T THL T TEL Ttot 1
LFSC , LWEU , LFSC+WEU, LWEU , LWEU , arb. un.
0.
0.6
5 0. 4 0. 3
4
X-X-V 2
4 6
10 1 2
month
Figure 8. The changes in the average monthly values
of conventional fuel savings during the year when separately and in combination with FSC and WEU, to cover the total HL and electrical load (EL) required for HS and HWS:
l - L
L
EL
FSC
5 - L
5 - Ln
2- L
2- L
HL
3 - L
'FSC+WTM
4 -
2
0
8
Using the indicators given in Table 6, the average monthly values of energy supply coefficients, which reflect the role of primary (alternating and WEU) and alternative (currently gas-fired heating) energy sources separately and together in the overall energy supply of an experimental individual house, were determined. Based on the obtained results, the graphical dependencies are presented in Figure 7.
Then, according to the methodology previously developed by us [3,9], the report shows the savings on conventional fuel when used separately and in combination with FSC and WEU to cover the total HL and electrical load (EL) required for HS and HWS.
During the calculations, the efficiency of the gas-fired heater was taken as 0.55 (due to the large heat losses, the maximum value of the efficiency of this type of heater is 0.6). Based on the results of the report, appropriate graphical dependencies were constructed, which are described in Figure 8.
When determining the energy supply coefficients of FSC and WEU, it was not considered that these quantities are greater than one for the summer months, as most of the energy produced by FSC, especially in those months, cannot be used and is considered a loss. However, Figure 7 considers the use of the energy generated by the WEU to meet only the total HL required for HS and HWS, as this is the main purpose of the present study. For this reason, WEUs energy utilization rate was zero in May-October. In general, the energy utilization rate of WEU is the same in all months of the year, which shows that its use as an autonomous energy source is highly efficient.
As a result of the calculations, it was determined that the amount of conventional fuel saved during the year for the HS and HWS of the experimental individual house separately using the FSC is 2,134 t.c.f., the amount of savings at the expense of a separate WEU is 1,731 t.c.f., the total amount of savings obtained from the joint use of FSC and WEU is 3,865 t.c.f., the savings obtained during the use of WEU for electricity supply in the summer months are 2,098 t.c.f., and finally, the total savings obtained from the use of WEU is 3,827 t.c.f.
Such an indicator is not a bad result for a single CSWPP used for individual purposes. If we consider that more than 20% of population in Baku lives in the surrounding villages, there is no doubt that this figure will be much higher, which is important both from a fuel saving and environmental point of view.
As can be seen from Figure 7, the maximum value of the energy utilization factor of the alternative energy source is observed in January and is 0.5. However, as mentioned above, if WEU with an output power of 8 + 10 kW is used, it is possible to provide the total HL by CSWPP throughout the year.
Conclusions
1. The indicators of gas and electricity meters installed in the house were used in order to accurately determine the daily and monthly amounts of total HL required for HS and HWS in the experimental private house with permanent population of 5 people located in the territory of Baku. The report first determined the total amount of total heat loss, and then the monthly amounts of total heat loss required for HS and HWS, as
well as the total heat loss. Analyzing the results, 8 SPL type FSCs with a total area of 19.2 m2 and AWPP-6-4M type WEU with a nominal output of 4 kW were selected to provide the house with hot water all year round and heating in most months of the year.
2. In order to study the possibility of providing daily and monthly HL for HS and HWS, WEU was tested naturally at different instantaneous wind speeds in the Absheron Peninsula, near the Absheron-lighthouse meteorological station, and its output power dependence was determined by wind speed. Then, the amount of daily and monthly energy that WEU can produce has been determined separately for each month considering the real power of the WEU at different wind speeds and the repetition coefficients of the different gradations of its instantaneous speed for the average annual wind speed (7.88 m/s) characteristic of the Absheron-lighthouse station. In this case, the monthly values of the correction factors determined by a special methodology were also used in order to increase the accuracy. It was found that the minimum value of energy produced by WEU in different months of the year differs by 20% from its maximum value. This shows the possibility of efficient use of WEU energy throughout the year.
3. Using the average monthly ISR values per 1 m2 of sloping surface of the FSC in the latitude of the Baku, the average monthly energy production of the FSC with a total surface area of 19.2 m2 was determined. In this case, the average monthly values of the efficiency of the FSC were considered. It was found that, in contrast to WEU, the maximum value of FSCs monthly energy production observed in June is 4.94 times higher than its minimum value observed in January. Moreover, FSC produces minimum energy in the months when there is a high demand for energy, and maximum in the months when there is less demand. This indicate it impossible to use FSC efficiently all year round, and most of the produced energy cannot be used during the summer months.
4. It has been determined that when FSC and WEU are used together, the consumer can be reliably provided with hot water in all months of the year, and heat in March-November. In the remaining months of the year, it is sufficient to use either an alternative energy source or WEU with nominal output power of 8
10 kW to heat the house. In this case, the additional energy produced by WEU can be used during the summer season both to cooling the experimental house and to supply electric devices.
5. It was determined that the maximum value of the energy supply coefficient for FSC is 0.659 (April), the minimum value is 0.108 (January), and the maximum value of this coefficient is 0.541 (November) and the minimum value is 0.341 (April) for WEU. It
was found that the joint use of FSC and WEU saves 3,865 tons of conventional fuel per year. By this way, the savings of FSC alone are 2,134 tons, the savings of WEU when used only to cover HL are 1,731 tons, and the total savings, including the use of electricity to cover electricity, are 3,827 tons of conventional fuel.
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