# Charge pump for solar cell.

#### RobertsMrtn

Joined Jul 19, 2020
2
I have a 7V solar panel which can power an electric pump to pump water to a height of 30cm when the sun is not behind a cloud. When the sun goes behind a cloud, the power drops too low to power the pump fully. Is there a circuit I can buy which will charge a hefty capacitor and then intermittently discharge once the correct voltage has been reached so that the pump will still pump water intermittently when the sun goes behind a cloud? I have looked at charge pump circuits which seem to do this type of thing, but can I wire my own capacitors to achieve different output voltages and discharge times? I also need to be able to disable the circuit when the panel is in full sun.

#### sparky 1

Joined Nov 3, 2018
301
The spiral pump is efficient at 30cm

#### crutschow

Joined Mar 14, 2008
25,267
Need to know how much current the motor takes, and what is its minimum operating voltage?

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#### dl324

Joined Mar 30, 2015
11,282
but can I wire my own capacitors to achieve different output voltages and discharge times?
You'd be better off using a battery.

#### MrChips

Joined Oct 2, 2009
21,666
Use the solar panel to charge a battery.

#### ci139

Joined Jul 11, 2016
1,677
The spiral pump
it does look "good" -- only there're 2 things :

• i must somehow compute the efficiency of such setup ...
... to be able to compare with the other ones ( there is an extra flow-drag because of the extensive tubing length ... )
.
• it generates high atmosphere mixed water content ...
... depending on circumstances -- it may favor the algae growth inside the tubing -- so permanent attachment of the tube -- may turn out to be not a practical solution

#### sparky 1

Joined Nov 3, 2018
301
The concept not the materials or a specific replication. Motor should be more compatable to the application such as a low BEMF like a window motor . Improvement using bearings. Photovoltaics directly converted to spiral disk torque on a cloudy day could rely on elevated storage of water lifted during solar intensive times. The use of vortex drain to generate so net loss is near zero.
The use of marsh variety plants that process waste. The real balance being that two systems of pH are needed. Whereas doggy world needs to sell disposable cartridges.

The fresh water is lifted up into two separate systems having water plants.
The alkaline in one and the acid variety in the other. This is why off the shelf is difficult to adapt to a biological system.

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#### ci139

Joined Jul 11, 2016
1,677
made a quick test with tiny 3x 2.4 x 13.6 cm = 97.92 cm² , 6V 60mA solar panel ::

$$\begin{array}{ccccl} {V_{R=∞}V}&{V_R\\V}&{I\\ \mathbf{mA}}&{R-Rm\\Ω}&condition\\ 5.73 & 5.60 & 12.1 & 390 & clear\\ 5.70 & 5.47 & 23.8 & 200 & clear\\ 5.67 & 5.26 & 43.2 & 100 & clear\\ 4.32 & 1.665 & 13.7 &100 & cloudy\\ 4.32 & 1.355 & 11.35 &100 & *emulated\ 230W\ light\ source\ apx. at 30cm\\ 4.33 & 2.13 & 9.4 & 200 & SAP*\\ 4.33 & 3.0 & 7.0 & 390 & SAP*\\ \end{array}$$

from $$\displaystyle{ε=I\left({r+R}\right)=Ir+U \rightarrow \frac{\mathbf{-\Delta U}}{\Delta I}=\mathbf{r}=\frac{U_{\mathbf{0}}-U_{\mathbf{1}}}{I_1-I_0} ,\ \rightarrow \mathbf{ε}=\frac{\Delta\frac{U}I}{\Delta\frac1I}=\frac{U_1I_0-U_0I_1}{I_0-I_1}}$$

returns */!\ it may give better (lower) r value using R values closer to r ...

ε & r :: 5.73V & 11.0Ω for the sunny/"clear" and 4.81V & 277Ω for the "cloudy"

as the best energy transfer occurs at r=R the potential energy output at R is thus respectively $$\displaystyle{P_{r\&R}=\frac{ {\left({ \frac{ε}2 }\right)}^2}r}$$

avail energy RATIO P.cloudy/P.sunny ≈ 27.8%
EDIT :: i thought i passed a mistake - and i did it's 2.78% , roughly $$\frac1{36}$$
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#### ci139

Joined Jul 11, 2016
1,677