Wednesday, November 02, 2016

Good old tiles with embedded solar panels

I wish to trigger several student projects around the idea of using roof tiles to tap solar energy.  I think that students of architecture, design, or civil/electrical engineering would find this most interesting.

At the higher end, Tesla Motors in the US has showcased advanced batteries for home use to store solar energy as well as efficient and attractive solar tiles. Visit

However, affordability in countries like India makes it necessary for them to develop their own solutions. I urge students in such countries to try their own designs. The greatest value would be in areas where power failures/cuts are frequent, and of course in rural areas which are not electrified. As the cost of electrical power keeps going up at the consumer end, many rural homes may choose solar solutions to cut expenditure. 
Look at what is called a Mangalore Tile in India:

It is usually made of clay and is 10 to 16 inches in size. I think that there is some logic in making solar tiles of the same size. Such solar tiles can be used along with the traditional Mangalore Tiles to build a roof and use only a fraction of the roof area to produce electricity. An alternative would be to make a big tile 20 x 32 inches in size, to replace four Mangalore Tiles. A large tile would be more susceptible to breaking during transportation and installation. So, some reinforcement should be considered to make them less fragile. Ideally, the tile should provide a connector on the lower side, that is inside the dwelling, to minimize wiring required. It would be great if the tile provides for supporting a lithium ion battery below it. This would enable keeping the battery inside the house. Care would have to be taken to insulate the battery from the heat that would emanate from the tile during daylight hours. An air gap between the tile and battery would help. It would be nice if the tile also provides mechanical support for suspending a small ceiling lamp with a reflector and LED. Then the wiring required would be minimal. 

How would you turn the lamp on or off? A hanging power cord with a switch at the lower end? Or a remote-control mechanism that responds to the TV set’s remote control when it is pointed at the tile? 
If you manage to get all this done, you can then consider if you can buy a DC driven small fan and incorporate that as well into the system. By then you might consider using two or more big tiles connected in parallel. The tile design should provide for serial or parallel connection of individual tiles.  
The National Renewable Energy Laboratory (NREL) of the US provides information about solar energy incident at different places in North West India.

In general, most places in India seem to receive about 4 to 7 kWh/m2 per day. That means that a big tile (as defined above) would generate only a fraction of this energy. Such a tile would have energy generating area somewhat less than 20x32 sq. inches, which is about 0.4 sq. meter.  A tiled roof would receive direct sunlight only for a few hours per day, and the energy it receives would depend upon the place it is in, the slope of the roof and the direction it is facing. Then there is the efficiency of energy conversion, perhaps about 10%. My guess is that with good engineering one could expect to get about 0.05 kWh per big tile, enough to power one or two 6W LED lamps for a few hours a day.
There are solar lighting solutions in the market that could provide parts for experiments with tile based solar energy system. Visit, for instance, 


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