RU2670180C1 - Solar module with asymmetric parabolic cylindrical concentrator and photo receiver with triangular profile - Google Patents

Abstract

FIELD: solar engineering.SUBSTANCE: invention relates to the field of solar engineering and concerns a solar module with an asymmetric parabolic cylindrical concentrator and a photodetector with a triangular profile. Solar module contains an asymmetric concentrator of one branch of a parabolic-cylindrical type with a mirror internal reflection surface and a line photodetector located in the focal region with a uniform distribution of concentrated radiation along the cylindrical axis. Linear photodetector is made hollow with a variable triangular profile for the flow of the coolant. Concentrated radiation from the reflecting surface of the concentrator corresponds to the condition of uniform longitudinal illumination of the working surface of the photodetector. Photodetector is fixed rotatable along the cylindrical axis by the device on the fastening posts.EFFECT: technical result consists in increasing the efficiency of heating the coolant, increasing the efficiency of the module and ensuring the operation of the photodetector of the solar module at moderate concentrations and optimum illumination of the photodetector.1 cl, 8 dwg

Description

The invention relates to solar engineering and the construction of solar modules with photovoltaic and thermal receivers of solar radiation and concentrators for generating electrical energy and heat.

A solar module with a concentrator is known, comprising a main linearly-focusing parabolic-cylindrical mirror reflector made of two different parts in the form of one branch of a para-cylindrical reflector with a second semi-cylindrical mirror reflector, and a photoelectric receiver in which the radiation receiver is made of a glass cylindrical tube and a flat glass unit integrated inside photoelectric receiver with solar cells (RF patent No. 2225966, IPC F24J 2/14, published 2004).

The disadvantages of the known solar module are a complex system of a photovoltaic receiver, which leads to the loss of solar radiation.

Closest to the technical nature of the present invention is a solar module with a concentrator containing a main linear focusing parabolic cylindrical reflector and a receiver in the form of a strip mounted parallel to the focal axis of the main reflector, in which the main mirror reflector is made in the form of one branch of a parabolic cylindrical reflector, equipped with a second a semi-cylindrical mirror reflector, as well as a third

semi-cylindrical reflector, and the third mirror reflector is equipped with a device for rotation around its axis (RF patent No. 2206837, IPC F24J 2/14, published 2003).

The disadvantages of the known solar module are:

- a decrease in the optical efficiency of the module due to multiple, at least 3 times on each concentrator, reflection of sunlight from the concentrators, as well as due to absorption of reflected rays passing through the glass elements enclosing the photomultiplier, therefore, the overall efficiency of the conversion of solar energy to thermal and electric;

- complication of the design of the module;

- the difficulty of adjusting 2-3 concentrators and receivers of concentrated radiation;

- shading by additional concentrators of the main one.

The objective of the invention is to ensure the operation of the photodetector of the solar module at medium concentrations and optimal illumination of the photodetector, increasing the efficiency of heating the coolant (water) and reducing the cost of generated energy.

As a result of using the present invention, the overall efficiency of the module (thermal and electric) is increased, it becomes possible to more efficiently generate thermal energy and heat carrier due to the formation of optimal illumination by concentrated radiation on the surface of a ruled photodetector with a triangular profile made hollow for the heat carrier duct.

The above technical result is achieved in that in a solar module with an asymmetric parabolic-cylindrical concentrator and a photodetector with a triangular profile, containing a concentrator asymmetric from one branch of the parabolic-cylindrical type with a mirrored internal reflection surface, and a linear photodetector located in the focal region with a uniform distribution of concentrated radiation along the cylindrical axis ,

according to the invention, the line photodetector is hollow with a triangular profile for the coolant flow, and the concentrated radiation from the reflecting surface of the concentrator corresponds to the condition of uniform longitudinal illumination of the working surface of the photodetector, while the photodetector is fixed by a device rotatable along the cylindrical axis on the mounting posts, and the distribution of the profile area F _n and the volume V _{n of the} photodetector along the working surface of length L, width d with an interval Δd are determined by the ratio:

F _n = Δd [h ₁ + Δh (n-1) / N + Δdtga / 2], Δh = (hh ₁ ) / N, Δd = d / N, V _n = F _n L,

where n varies in the intervals n = 1, 2, 3 ... N;

h ₁ - the minimum height of the profile of the photodetector;

h is the maximum height of the profile of the photodetector,

and the distribution of the heating temperature of the coolant along the profile of the photodetector is determined taking into account the distribution of the concentration K _{n of} solar radiation over the width of the photodetector d, the shape of the profile of the photodetector and is determined by the system of equations corresponding to the condition for the average value of the distributed temperature T _cf and the output temperature of the coolant T _o (T _cf = T _out ):

n * = V _n / V _min , n * _max = V _max / V _min , ΔT ₁ = ΔT _cp / n * _max , ΔT _cp = (T _out -T _in )

T * _n = T _PL + [ΔT ₁ n * f (K _n )],

,f (K _n ) = K _g / K _n , T _n = T * _n k _cor -T _pl + T _in , k _cor = (T _pl + ΔT _cp ) / T * _ncp ,

,

where V _min is the minimum value of the volume of the photodetector along the working surface of length L, width d with an interval Δd in the intervals n = 1, 2, 3 ... N;

V _max - the maximum value of the volume of the photodetector along the working surface of length L, width d with an interval Δd in the intervals n = 1, 2, 3 ... N;

T _I - the input temperature of the coolant;

T _PL - melting point, K (phase transition solid / f);

f (K _n )] is the distribution function of the concentration over the width of the photodetector, and the average value of the distributed temperature (boundary condition);

T _ncp = ΣT _n / N = T _o is equal to the output temperature of the coolant, and the heating energy of the coolant is determined by the ratio:

where, T _n = T * _n k _cor -T _pl + T _I ,

[λ / η] _(Tn) is the ratio of thermal conductivity to viscosity of water at a heating temperature along the receiver profile T _n ,

[λ / η] _(Tcp) - the ratio of thermal conductivity to viscosity at an average temperature T _c = T _out water,

the heating time of the coolant to T _cp = T _o is determined by the ratio:

,

,

where P = P _p -P _conv- P _rad;

P _p - absorbed by the receiver stream P _p = η _opt E _with F _PP K _g ;

where the heat loss to the environment is convective P _conv , radiation P _rad ;

To _g - geometric concentration;

η _opt - optical efficiency;

E _with - the specific power of solar radiation;

F _PP - the area of the midsection of the concentrator,

heating the mass of the coolant per unit time m * (flow) to T _cf = T _o is determined by the ratio:

m * = m / t, (m = ρ V),

where m is the mass of the coolant;

ρ is the density of the coolant;

V is the volume of the heated coolant in the photodetector,

thermal power of the heat carrier is determined by the ratio:

P _t = m * s (T _out -T _in ),

where c is the heat capacity of the coolant;

T _I , T _o temperature at the inlet and outlet of the photodetector,

the thermal efficiency of the module (the efficiency of the solar radiation power) is determined by the ratio: η _t = P _t / E _c F _pp .

The invention is illustrated in FIG. 1-8.

In FIG. Figure 1 shows the design diagram of a solar module with an asymmetric parabolic cylinder concentrator with a uniform distribution of concentrated radiation on the ruled surface of the photodetector.

In FIG. Figure 2 shows the path of rays from an asymmetric parabolic-cylindrical concentrator to a photodetector.

In FIG. Figure 3 shows the design form of the concentrator and photodetector of the solar module.

In FIG. 4 shows the profile shape of the photodetector of the solar module.

In FIG. Figure 5 shows the distribution of the illumination concentration on the working surface of the module photodetector over the width d of the focal region.

In FIG. Figure 6 shows graphs of the distribution of the heating temperature of the coolant of the module for various functions of the distribution of the concentration of illumination on the working surface of the photodetector of the module over the width d of the focal region.

In FIG. Figure 7 presents graphs of the temperature versus the flow rate of the coolant of the module for various functions of the distribution of the concentration of illumination on the working surface of the photodetector of the module (experimental data are indicated by dots).

In FIG. Figure 8 shows graphs of the dependence of thermal efficiency on the flow rate of the coolant of the module for various functions of the distribution of the concentration of illumination on the working surface of the photodetector of the module (experimental data are indicated by dots).

The solar module in FIG. 1 consists of an asymmetric parabolic-cylindrical hub 1, mounted on racks 2,

line photodetector 3 of width d, length L, equipped with a rotary device 4, mounted on the support posts of the fastening 5, the device of the flow of coolant 6, with fittings 7 for the input and output of the coolant.

The asymmetric parabolic cylinder concentrator 1 of the solar module in FIG. 2 with a working profile concentrates solar radiation beyond the focal region on the working surface of the photodetector 3 of width d _o , length L; rays from the upper part of the concentrator come to the lower part, and rays from the lower part of the concentrator come to the upper part of the photodetector 3.

The shape of the reflective surface of the concentrator X (Y) is determined by a system of equations corresponding to the condition of uniform illumination of the working surface of the photodetector, made in the form of a ruler of width d _o and length L and located at an angle to the center of the concentrator:

Х_н=d_osinβ_в, Y_н=f-Х_нtgβ,X _n = (fY _n ) / tgα _n ,

X _n = d _o sinβ _in , Y _n = f-X _n tgβ,

Х_в=0, Y_в=Y_н+dcosβ_н,

, Y_a=R²/4f, К_г=R/d_o,

X _in = 0, Y _in = Y _n + dcosβ _n ,

, Y _a = R ² / 4f, K _g = R / d _o ,

where α _n is the angle (in the area of the working profile of the concentrator) between the ordinate level at the coordinate point X _n , Y _n and the beam reflected from the surface of the parabola with focal length f, coming into the focal region at a width d _n located on a flat photodetector with a width d _o , where n is selected from a series of integers n = 1, 2, 3 ... N;

ξ _about is the angle between the coordinate axis 0Y and the beam reflected from the upper coordinate point Y _a , R of the concentrator arriving at the lower coordinate point of the photodetector X _n , Y _n ;

(между нижней точкой координат фотоприемника Х_н,Y_н и фокусным расстоянием f параболы);β _n - the angle between the photodetector and the segment

(between the lower coordinate point of the photodetector X _n , Y _n and the focal length f of the parabola);

(между верхней точкой координат фотоприемника Х_в,Y_в и фокусным расстоянием f параболы) и поверхностью фотоприемника;β _in - the angle between the segment

(between the upper coordinate point of the photodetector X _в , Y _в and the focal length f of the parabola) and the surface of the photodetector;

β is the angle between the beam reflected from the upper coordinate point Y _a , R of the concentrator and the straight line Y = f parallel to the abscissa axis;

the values of the parameters f, β _in , k are selected in accordance with the boundary conditions, and the geometric concentration of the illumination of the photodetector K _n in the intervals of the coordinate values of the concentrator ΔX _n = X _n -X _n-1 and in the intervals of the coordinate values of the photodetector (d _{n + 1} -d _n ) is equal to:

K _n = (X _{n + 1} -X _n ) / (d _{n + 1} -d _n )

Based on the above formulas, the shape of the reflecting surface of the concentrator and the coordinates of the photodetector are calculated — a graph of the dependence Y (X) (Fig. 3).

In FIG. 4 shows the profile shape of the photodetector of the solar module.

In FIG. Figure 5 shows the distribution of the illumination concentration on the working surface of the module photodetector over the width d of the focal region.

With a decrease in the width d _{o of the} photodetector 3, (with a decrease in the area), the illumination concentration of the photodetector 3 increases.

Thus, it is possible to change the concentration of illumination of the photodetector 3, without changing the overall dimensions of the hub 1 and the photodetector.

It can be seen from the above characteristics that, for a different distribution of the light concentration over the width of the focal region of the photodetector 3, a different effect on the volumetric heating of the heat carrier in different parts of the cavity of the photodetector occurs, which affects the thermal characteristics of the solar module.

Calculation of heat and mass transfer was carried out in accordance with the general heat engineering formulas:

α=5,7+3,8 V, Q_рад=εσ(T_c ⁴-T_a ⁴)F, Q=Q_пп-N-Q_конв-Q_рад. m=Q/c_p(t_вых-t_вх), W=m/γF_пс, Re=wd_экв/ν, α_ж=Nu λ_ж/d_экв, Q_в=α_ж(t_c-t_ж)F, η=η_o[1-k(T_f-T_o)],Q _pp = η _opt RF _pp To _geom , N = Q _FE η _FE .

α = 5.7 + 3.8 V, Q _rad = εσ (T _c ⁴ -T _a ⁴ ) F, Q = Q _pp -NQ _conv -Q _rad . m = Q / c _p (t -t _{Rin O),} W = m / γF _ps, Re = wd _eq / ν, α _w = Nu λ _g / d _eq, Q _a = α _x (t _c -t _x) F, η = η _o [1-k (T _f -T _o )],

wherein Q _claims - absorbed receiver stream, η _opt - optical efficiency, R - the direct solar radiation, F _nn - receiving surface area, K _Geom - geometric concentration, N - power electric, η _PV - the efficiency of the PV Q _PV - absorbed flow photocells Q _Conv is convective heat loss, α is the heat transfer coefficient, t _c , ° C is the average temperature of the receiver wall, t _a , ° C is the temperature of the medium, V is the wind speed, Q _rad is the radiation heat loss, _ε is the degree of blackness of the wall, σ is Stefan-Boltzmann constant, T _c, K - average temperature of the wall of the receiver, _and T, K -_tempe Atur medium, _Q - flow for cooling the coolant, m - mass flow rate of water to _p - specific heat, t _O, t _Rin - water temperature at the exit and the receiver input, W - water flow rate, γ - density of water, F _ps - receiver cross-sectional area, d _equiv - equivalent diameter of the receiver cross-section, v - coefficient of kinematic viscosity of water, Re - Reynolds number, Nu - Nusselt number, α _w - heat transfer coefficient from wall to water, t _w - average water temperature, λ _w - water heat transfer coefficient, Q _a - heat flux distilled water second, η _t - dependence of efficiency PV from temperature, η ₀ - efficiency PV at a standard temperature T ₀ = 298 K, T _ƒ - PV temperature, k - temperature coefficient.

The dependence of the thermal conductivity of water on the heating temperature λ = f (T) was obtained in accordance with the developed system of equations:

- отношение температуры плавления (К) к температуре нагрева воды (К);where for water

- the ratio of the melting temperature (K) to the temperature of water heating (K);

- значение коэффициента

при температуре кипения (фазового перехода ж/пар) воды Т*=Т_к, (K),

- coefficient value

at the boiling point (phase transition w / steam) of water T * = T _k , (K),

where T _PL is the melting temperature, K (phase transition solid / f);

ΔT is the temperature of water heating, C;

T * = T _pl + ΔT - temperature of water heating, K;

λ _about - thermal conductivity of water (ice) at the melting temperature;

λ _t - thermal conductivity of water at a heating temperature.

The dependence of the dynamic viscosity of water on the heating temperature η = f (T) was obtained in accordance with the developed system of equations:

where η _o is the dynamic viscosity of water at the melting temperature;

η is the dynamic viscosity of water at a heating temperature;

T _PL - melting point, K;

ΔT - heating medium temperature, С;

T * = T _pl + ΔT - heating temperature of the coolant (K);

- отношение температуры плавления (К) к температуре нагрева теплоносителя (К).

- the ratio of the melting temperature (K) to the heating temperature of the coolant (K).

Based on the above formulas, the dependence of the characteristics of the solar efficiency module η _(T) , water consumption m _(T) on temperature is calculated.

In FIG. Figure 6 shows graphs of the distribution of the module water heating temperature for various functions of the distribution of the illumination concentration on the working surface of the module photodetector over the width d of the focal region.

In FIG. Figure 7 shows plots of the temperature versus module water consumption for various functions of the distribution of the illumination concentration on the working surface of the module photodetector (dots indicate experimental data).

In FIG. Figure 8 shows graphs of the dependence of thermal efficiency on module water flow for various functions of the distribution of illumination concentration on the working surface of the module photodetector (dots indicate experimental data).

A solar thermal photovoltaic module with a hub operates as follows.

Solar radiation, falling on the working surface of the asymmetric parabolic cylinder concentrator 1 of the solar module (Fig. 1), is reflected at the calculated angles of inclination so that they

provided a uniform concentration of rays on the photodetector 3 of the module, made in the form of a ruler of width d _o and length L, and the device for the flow of heat carrier 6 is made in the form of a pipeline with a triangular cross-sectional profile in which the coolant (water) is heated.

By adjusting the flow rate and the flow rate of the coolant, it is possible to optimize the heating of the coolant, thermal efficiency (coefficient of conversion of solar energy into thermal) of the solar module.

An example of a solar thermal module with an asymmetric parabolic cylinder concentrator

The hub 1 (Fig. 1) with a length of L = 700 mm, a width of R _max = 660 mm, a height of 350 mm is made of an aluminum sheet with a thickness of 0.3 mm with a mirror-reflecting inner surface mounted on racks 2, with a calculated working profile that ensures uniform concentration rays in the longitudinal direction of the line photodetector 3 of a module with a width of h _o = 66 mm, length L = 700 mm, with a device for a heat carrier flow 6, made in the form of a pipeline with a triangular profile of size 80 × 80 × 10 mm and length L = 700 mm, with fittings 6 for the inlet and outlet of the coolant and fixed on racks.

The average concentration of illumination on the surface of the photodetector module is K ~ 10 times.

For the purpose of regulation (optimization at various angles of rotation of the photodetector β _in relation to the ordinate 0Y) of the distribution of the light concentration over the width of the focal spot, a ruled hollow photodetector of a triangular shape in cross section for the coolant flow is secured by a device 4 that rotates along a cylindrical axis on mounting posts 5.

Thus, the proposed module of concentrated solar radiation with an asymmetric parabolic cylinder concentrator 1 provides: a fairly uniform distribution of illumination with an average concentration of K ~ 10 times on the working surface of the photodetector 3 of the module, increasing the efficiency of conversion of solar energy into thermal energy by optimizing the distribution of the concentration of illumination over the width of the focal spot a triangular-shaped ruled hollow photodetector for a coolant flow.

Based on the above calculations, depending on the natural conditions - the flux density of solar radiation, wind speed, ambient temperature; the design parameters of the module — the shape and dimensions of the concentrator and the photodetector, the optical efficiency, the materials used, the flow rate of the coolant (water) —it can predict the output energy parameters and the overall performance of the module.

Claims (39)

A solar module with an asymmetric parabolic-cylindrical concentrator and a photodetector with a triangular profile, comprising a concentrator asymmetric from one branch of the parabolic-cylindrical type with a mirrored internal reflection surface, and a line photodetector located in the focal region with a uniform distribution of concentrated radiation along the cylindrical axis, characterized in that the line photodetector is made hollow with a triangular profile for the coolant duct, and concentrated radiation from the reflecting surface of the concentrator corresponds to the condition of uniform longitudinal illumination of the working surface of the photodetector, while the photodetector is fixed by a device rotatable along the cylindrical axis on the mounting posts, and the distribution of the profile area F _n and the volume V _{n of the} photodetector along the working surface of length L, width d with an interval Δd are determined by the ratio: F _n = Δd [h ₁ + Δh (n-1) / N + Δdtga / 2], Δh = (hh ₁ ) / N, Δd = d / N, V _n = F _n L, where n varies in the intervals n = 1, 2, 3 ... N; h ₁ - the minimum height of the profile of the photodetector; h is the maximum height of the profile of the photodetector, and the temperature distribution of the heating medium along the profile of the photodetector is determined taking into account the distribution of the concentration K _{n of} solar radiation over the width of the photodetector d, the shape of the profile of the photodetector and is determined by the system of equations corresponding to the condition for the average value of the distributed temperature T _cf and the outlet temperature of the coolant T _o : n * = V _n / V _min , n * _max = V _max / V _min , ΔT ₁ = ΔT _cp / n * _max , ΔT _cp = (T _out -T _in ) T * _n = T _PL + [ΔT ₁ n * f (K _n )], f (K _n ) = K _g / K _n , T _n = T * _n k _cor -T _pl + T _in , k _cor = (T _pl + ΔT _cp ) / T * _ncp ,

, where V _min is the minimum value of the volume of the photodetector along the working surface of length L, width d with an interval Δd in the intervals n = 1, 2, 3 ... N; V _max - the maximum value of the volume of the photodetector along the working surface of length L, width d with an interval Δd in the intervals n = 1, 2, 3 ... N; T _I - the input temperature of the coolant; T _PL - melting point, K (phase transition solid / f); f (K _n )] is the concentration distribution function over the width of the photodetector, and the average value of the distributed temperature (boundary condition) T _ncp = ΣT _n / N = T _o is equal to the outlet temperature of the coolant, and the heating energy of the coolant is determined by the ratio:

where, T _n = T * _n k _cor -T _pl + T _I , [λ / η] _(Tn) is the ratio of thermal conductivity to viscosity of water at a heating temperature along the receiver profile T _n , [λ / η] _(Tcp) - the ratio of thermal conductivity to viscosity at an average temperature T _c = T _out water, the heating time of the coolant to T _cf = T _o is determined by the ratio

where P = P _p -P _conv- P _glad P _p - absorbed by the receiver stream P _p = η _opt E _with F _PP K _g , where the heat loss to the environment is convective P _conv , radiation P _rad ; Kg is the geometric concentration; η _opt - optical efficiency; E _with - the specific power of solar radiation; F _PP - the area of the midsection of the concentrator, heating the mass of the coolant per unit time m * (flow) to T _cf = T _o is determined by the ratio: m * = m / t, (m = ρ V), where m is the mass of the coolant; ρ is the density of the coolant; V is the volume of the heated coolant in the photodetector, the thermal power of the coolant is determined by the ratio: P _t = m * s (T _out -T _in ), where c is the heat capacity of the coolant; T _I , T _o temperature at the inlet and outlet of the photodetector, the thermal efficiency of the module (the efficiency of solar radiation power) is determined by the ratio: η _(T) = P _t / E _with F _pp .

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