# Thermal absorbing system

1. Jun 29, 2006

### xharville

I want to attach a photovoltaic panel on top of a thermal absorbing system. My idea was to to replace or add a steel backing to the photovoltaic panel. The thermal system would consist of a box filled with water, which would be in direct contact with the panel. But before I begin my idea I need to know whether it would work. I need to know the heat transfer coefficient between steel and water so that I can find out whether the photovoltaic panel would be able to provide enough heat. But I don't know where to get the heat transfer value. I was thinking about using the formula q= h*A*deltaT but I figured this would leave me with two unknowns. I searched around for a value for the heat transfer coefficient between steel and water but no website gave me a value. Could someone please tell me a value or a correct formula. Thanks for the help.

2. Jun 29, 2006

### Artman

Are you talking about solar heat? There are charts on how much energy transfer you can get for the the conditions (cloudy or clear), time of year, time of day, and location of your system.

Not sure if this is what you are talking about.

3. Jun 30, 2006

### FredGarvin

Since the water is not flowing, try using a simple 1-D conduction scenario (plane wall). You would then only need the heat transfer coefficient of the steel plate. Of course this value will change with temperature and so will the overall heat transfer rate. Your water and whatever is on top of the steel plate will dictate the delta T across the plate. Then it's just q=((k*a)/L)*dT

At 300 K, plain carbon steel has a tabulated value of 60.5 W/m*K .

The only caveat with this is that this assumes no heat generation and steady state conditions. I would think it would get you in the ballpark though.

Last edited: Jun 30, 2006
4. Jul 3, 2006

### xharville

I am trying to transfer heat through the solar panel to heat the water. I know that 43 % of the energy created by photovoltaic panels is loss through heat. So I was trying to figure out how hot I would be able to get the water and how much heat energy would be created. I was going to replace the back of the panel with a steel sheet that would be around 0.0017 m thick. I would have a thin plastic box that was integrated below the panel with pipes running through them. The water would be in direct contact with the panel and flowing. The box dimensions are 6.32m * 6.4 m * .0005 m. I have 32 165 W solar panels for this experiment. Each individual solar panel has the dimensions 1.58 m * .800 m * .046m.