84
2
Fig. 1.
Block diagram of a combined energy device consisting of a solar photovoltaic plant and a
microhydroelectric power plant. The combined energy complex consists of the following: 1-solar power
plant, 2-microhydroelectric power plant, 3-rectifier, 4 and 5-controlled switches, 6-first control device,
7-boost converter, 8-second control device, 9 – current measuring device, 10 and 11 - controlled
switches, 12 and 13 - a device for measuring current, 14 - battery, 15 - ballast load, 16 - inverter and 17
- load.
The second control unit 8 controls the operation of the energy accumulator 14, the ballast
load 15, designed to consume excess power, and the load 17, which receives energy through
the inverter 16 through current measuring devices 9, 12 and 13, as well as using controlled
switches 10 and 11, excess power is transferred to the ballast load, controls battery
consumption and charging.
2 Materials and methods
To determine the geometrical and hydraulic parameters of the Archimedes screw, certain
characteristics will be fixed to facilitate the study. In Figure 2, the screw parameters are
shown.The geometric parameters of an Archimedean screw are [12]:
•
the outer radius Ra
• the inner radius Ri
• the pitch of the screw S
• the total length L
• the threaded length Lb
• the number of blades N
• the inclination of the screw β
The hydraulic parameters are:
• the inflow Q
• the geodesic head H.
, 05027 (2024)
BIO Web of Conferences
AQUACULTURE 2023
https://doi.org/10.1051/bioconf/20248405027
84
3
Fig. 2.
Longitudinal section of the Archimedes screw turbine
In the work of [13], the author asserts that the screw performs well when the angle of
inclination varies from 22
0
to 45
0
. We therefore fixed the value of this angle at β = 25◦.
The number of blades used for the design of the turbine is fixed at N equal to 1 referring
to the work of Maulana et al. [14] who showed that turbines with one blades have a more
inclined pressure distribution so that it has better stability. The length of the screw L
b
is taken
equal to 1.89 m. The geodesic drop height is set at 0.8 m depending on the topography of the
site. Finally, the outer radius Ra is 0,34 m.
Not all the water entering the Archimedean turbine is involved in generating electricity.
Part of it flows through the gap between the blades and the frame, and the other part forms a
layer of excess water after filling the blade capacity to the optimal point.
To determine the flow rate of water entering the Archimedes turbine, we use the analytical
model developed by D. M. Nurnberg and K. Rores [15].
Rotation speed, n rpm:
𝑛 ≤
50
(2𝑅
𝑎
)
2
3
The ratio of radii r and the ratio of steps l is determined by the following formula:
𝜌 =
𝑅
𝑖
𝑅
𝑎
(1)
𝜆 =
𝑆∙tan𝛽
2𝜋𝑅
𝑎
(2)
The ratio of volume to revolutions
𝜆𝑣
𝑈
is assumed to be 0.98, taking into account that N=1.
The flow rate of water generating electricity
𝑄
𝑊
is determined as follows:
𝑄
𝑊
=
2𝜋
2
𝑅
𝑎
3
tan𝛽
𝜆𝑣
𝑈
𝑛
60
(3)
The leakage angle values
𝛼
3
,
𝛼
4
and
𝛼
5
are found using the algorithm described by Rorres
(2000):
𝛼
3
= 0.478 radians;
𝛼
4
= 2.338 radians;
𝛼
5
= 0.358 radians.
The determination of the distance between the trough and thescrew Ssp (m) is given
by Eq. (4) [16, 17]:
𝑠
𝑠𝑝
= 0.0045√2𝑅
𝑎
(4)
The value of the distance dh in the vertical direction between the surfaces of the water
layers on two adjacent steps of the parrot is found:
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4
𝛿ℎ =
𝑆
𝑁
𝑠𝑖𝑛𝛽
(5)
The water flow
𝑄
𝐺
passing through the gap between the blades and the blade is found
by the following formula:
𝑄
𝐺
= 𝜇
𝐴
𝑠
𝑠𝑝
𝑅
𝑎
(1 +
𝑠
𝑠𝑝
2𝑅
𝑎
) √1 + (
𝑆
2𝜋𝑅
𝑎
)
2
∙ (
2
3
𝛼
3
+ 𝛼
4
+
2
3
𝛼
5
) √2𝑔𝛿ℎ
(6)
The total water flow Q entering the turbine is:
𝑄 = 𝑄
𝑊
+ 𝑄
𝐺
(7)
The mechanical power of the screw shaft Pm is determined from Eq. (18) [18-20]:
𝑃
𝑚
= 𝜌𝑔𝑄𝐻
(8)
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