Hai Veera,

There are 2 conditions,

Condition 1: Pouring water over the panels

If you pour water over the panels then there won't be any significant increase in your efficiency.

Because, the water you pour on the top of the panels will decrease the solar irradiation falls on the panels. So the good(taking away heat) done by the water is compensated by blocking the solar irradiation.

Condition 2 : Flowing water under the panels in a passage or spraying water under

In this condition the water will take away the heat and also it will not block the solar irradiation falling on the panels. So the efficiency of the panels are increased and also you will get hot water.(double bonanza)

There is a research going on this hybrid type of solar PV+thermal panels in CSIR renewable energy division in chennai.

Dear Prof. Veera,

      The water flow over the solar PV panel will reduce the heat. Reduction in the heat will increase the efficiency of solar PV Panel. 

   According to my perception water flow under the solar panel will good effect than the water flow over the solar PV panel.

Hai Veera,

There are 2 conditions,

Condition 1: Pouring water over the panels

If you pour water over the panels then there won't be any significant increase in your efficiency.

Because, the water you pour on the top of the panels will decrease the solar irradiation falls on the panels. So the good(taking away heat) done by the water is compensated by blocking the solar irradiation.

Condition 2 : Flowing water under the panels in a passage or spraying water under

In this condition the water will take away the heat and also it will not block the solar irradiation falling on the panels. So the efficiency of the panels are increased and also you will get hot water.(double bonanza)

There is a research going on this hybrid type of solar PV+thermal panels in CSIR renewable energy division in chennai.

Dear Veera,

Using water as a coolant for increasing the efficiency of solar panel is a good thought, but pouring water will definitely reduce the irradiation.Instead of pouring u can try spraying the water.Kindly refer the pdf file.

Continously spraying the water might not increase the efficiency, but intermittent spraying of water would augment the efficiency of PVs

The water cooling will increase PV power by several percents (maybe). But additional loss on water pumping and transportation will decrease this effect.

I hope the solar water heater with PV-battery on the front side is more useful. But I doubt on the effective realisation of thermal contact between PV and water tank. Any deformation of  the tank surface will destroy thin and fragile PV elements.

And what is about industrial safety of high voltage PV system with water  round-up?

Dear Prof. Veera

My own concern is also directed both to get the best from the solar radiation and generate as much electricity as possible. Anyway, the extra electricity consumption associated to the pump on one side and the one needed to get and carry the water from its source, being possibly not negliigble, may therefore diminish the total energy balance.

Have you measured or calculated such extra electricity consumption?

Best Regards

Jacques

I think it will not in the long run. Maybe in the short term.

Unless extremely clean, (maybe even needs to be de-ionized) water is used, residue will build up and reduce output or require extra cleaning. Recirculating might seem attractive, but adds cost and energy use for cleaning the water and increases the evaporation residues. Free water is seldom clean enough to used untreated. Perhaps in Norway.

Regarding the electrical risks, I sure hope any solar panel mounted outdoors is capable of handling rain fall or the investment will have a very bad ROI.

The waste heat recovery technique can be used to reduce the heat from the solar PV panel but direct flow of water above the panels will directly effect the power produced. 

Pouring water over the panels is used only at the time of cleaning the solar panels once in a week or more than that....it will definitely increase the output power (this is the regular practice in most of the large scale PV power plants).

But continuous Pouring of water over the panels or under the panels will never increase the output efficiency .... rather it will induce some unwanted disturbance to the system.. PVT needed individual paths for electrical as well as thermal energy..

In my opinion PVT is totally different research area from cooling of PV panels...

There are competing benefits and drawbacks as follows:

Benefits:

1) Water will lower the surface temperature of the solar panels and, hence, efficiency will improve.

2) flowing water will clean surface of  the solar panels which will improve the efficiency.

Drawback: Water film on the surface of the solar panel may act as a reflecting mirror which reflects the sun radiation away from the panels. This will decrease the efficiency.

It would be possible the net result would be slight improvement in the performance of the solar panels.

Hope this helps answer your question.

Professor Yehia Khalil

Yale University

USA

"Yehia F. Khalil. Drawback: Water film on the surface of the solar panel may act as a reflecting mirror which reflects the sun radiation away from the panels. This will decrease the efficiency."

n=1.3 - water; n=1.5 - glass; n=1 - air. R=(n1-n2)/(n1+n2) for pitch angle near 0.

So reflection from water surface less compare to glass one.

The additional water layer works as anti-reflection (match) coating in coated lens

Thanks to all for you quick response and valuable answers,

Dear Sir,

Generally, the energy efficiency of a solar panel (thermal collectors or PV/T systems) increases with the increasing of coolant flow (air or water).

Article Study and modeling of energy performance of a hybrid photovo...

Mohamed El Amine Slimani Article: Study and modeling of energy performance of a hybrid photovoltaic/thermal solar collector: Configuration suitable for an indirect solar dryer

This is a great work! There are answers for most questions. The Heat energy 5 time  greater relative to Electric energy.

My respect to all colleagues. The question is not very definitive. The author would tell us about the objectives of this experiment. Is the water flow to cool the cells or to collect the heat from incident solar radiation. In both cases it is advisable to let the panels face the sun and collect or cool the panel from the back side. Simply because water in the front will obstruct the incident solar radiation and at the same time it will be in contact with glass which is a bad heat conductor.

Best wishes to all.

1) Flowing of water on the solar panel reduces the temperature of the solar panels. Reduction in temperature by 1 degree c increases the efficiency by 0.35-0.5%.

2) Its helps in cleaning of the panels.

3) The thin layer of water over the panel ( refractive index of 1.33) between air and glass reduces the reflection of solar radiation giving more solar penetration.

I hope this helps, open to any clarifications and inputs.

If my main purpose is to clean the panel surface by continuous flow of thin layer of water and hence reducing the temperature as the added advantage, would it be advisable to obtain greater output from the panel?