“Fizika va texnologik ta’lim” jurnali | Журнал “Физико-технологического
образование” | “
Journal of Physics and Technology Education” 2021, № 4 (Online)
Journal of Physics and Technology Education | https//phys-tech.jspi.uz/
13
When using photocells, the question often arises
of the energy efficiency of
converting electrical energy. As we know, in practice two main modes of using
photocells are applied - continuous and periodic. The
calculation of the energy
efficiency of solar cells for these modes is carried out according to different
methods. So, to evaluate the effectiveness in continuous mode,
the efficiency
indicator is used. In periodic mode, the efficiency indicator does not reflect the
picture of energy consumption [2].
In
continuous operation, the photocell is constantly working on load. The
power of this load may vary over time. Let us evaluate the effect of the
efficiency of photocells on the duration of their work. Then for the load power
and duration of work we have the following formulas
i
P
P .
E
T
.
P
where
P is the load power; P
i
power consumption from the battery; E is the
available
energy of the accumulator; T - the duration of the load; η is an
indicator of efficiency. It can be seen that
the duration of the load is
proportional to the efficiency. So, if in the ideal case when η = 100% the battery
life is 10 hours, then with a real value of 80% efficiency,
the battery life
decreases by 20% and will be 8 hours. In order to evaluate the efficiency of the
photocell, we need to know the efficiency indicator at an arbitrary load power
[1]. Now consider the proposed linear energy model of the solar cell. This
model is a simplification of the real processes occurring in the photocell;
accordingly, the efficiency indicator obtained using
the model has a certain
error. The model can be displayed in the form of an electrical circuit shown in
Fig. 1. The essence of the circuit is that there is a load from the source of
electrical energy displayed by the resistance R
n
. The R
s
and R
p
present in the
resistance circuit simulate energy losses. P
p
models
the no-load losses, and P
s
models the losses due to the introduced series resistance. A typical graph of this
dependence is shown in Fig. 1.
