I started this blog in order to share ideas on small scale alternative energy devices. In this post I am going to discuss a very interesting device. The idea is nothing new. It has existed for over a century. Let me explain the basic principle.
The Solar Updraft Tower
The solar updraft tower is basically just a large heat collector with a chimney in the middle. It works on the principal of convection. The heat collector is similar to the solar cooker or the solar water heater. It's consists of a glass canopy spread over the ground. It collects and traps sunlight and heats up the air underneath the canopy. We all know that hot air rises. Since the hot air has nowhere else to go, it rises straight through the chimney in the middle of the canopy.
The purpose of chimney is to create a draft. The temperature at the top of the chimney is much lower than the temperature of the hot air (heated by the solar collector) at the bottom. This temperature difference causes a difference in pressure, which in turn causes the hot air to rise rapidly. This is called updraft.
Those of you who are technically oriented can read more about this phenomenon here:
http://en.wikipedia.org/wiki/Stack_effect
All you have to do is to place turbines at the mouth of the chimney such that the turbines face the air flow. The air rising through the chimney will rotate these turbines and viola, you've got electricity. its quite a simple device. Read more about the Solar Updraft Tower here:
http://en.wikipedia.org/wiki/Solar_updraft_tower
My Thoughts And Ideas I Want to Experiment With
Now suppose I want to build something like this on a much smaller scale, say, just big enough to provide electricity to a small household, maybe 300-500 Watts. I want to improvise the design since I think that the maintenance of a glass canopy would be too much hassle. Glass is expensive and breaks easily.
So I have some ideas. Suppose we lay down some metal sheets very close to the ground(maybe half an inch above the ground). We paint the top surface of this metal canopy black, so it absorbs sunlight and gets really hot(I think 60 degree Celsius is easily attainable in tropical regions like southern India). We spread these black painted metal sheets over an area of a few square meters(maybe 100). At the centre of this canopy we make a hole and place a 10 feet tall chimney and inside the chimney we place a turbine. So I am hoping that heat absorbed by the metal sheets will be transferred to the thin layer of air underneath the sheets. The hot air will rise through the chimney and rotate the turbine.
The reason I like this device so much is because of its simplicity. It can be built and maintained by people anywhere in the world. There are very few moving parts. And there is no need for complicated devices like heliostats (sun trackers) and heat engines. Of course, this simplicity comes at the cost of efficiency. There is always a trade-off between simplicity and efficiency. But since I plan to build small scale devices, it is better to keep it simple. Plus sunlight is free. So efficiency is not the most important thing.
Your Thoughts?
I urge all those who read this post to share their thoughts on the ideas mentioned above. Also feel free to suggest your own ideas.
The Solar Updraft Tower
The solar updraft tower is basically just a large heat collector with a chimney in the middle. It works on the principal of convection. The heat collector is similar to the solar cooker or the solar water heater. It's consists of a glass canopy spread over the ground. It collects and traps sunlight and heats up the air underneath the canopy. We all know that hot air rises. Since the hot air has nowhere else to go, it rises straight through the chimney in the middle of the canopy.
The purpose of chimney is to create a draft. The temperature at the top of the chimney is much lower than the temperature of the hot air (heated by the solar collector) at the bottom. This temperature difference causes a difference in pressure, which in turn causes the hot air to rise rapidly. This is called updraft.
Those of you who are technically oriented can read more about this phenomenon here:
http://en.wikipedia.org/wiki/Stack_effect
All you have to do is to place turbines at the mouth of the chimney such that the turbines face the air flow. The air rising through the chimney will rotate these turbines and viola, you've got electricity. its quite a simple device. Read more about the Solar Updraft Tower here:
http://en.wikipedia.org/wiki/Solar_updraft_tower
My Thoughts And Ideas I Want to Experiment With
Now suppose I want to build something like this on a much smaller scale, say, just big enough to provide electricity to a small household, maybe 300-500 Watts. I want to improvise the design since I think that the maintenance of a glass canopy would be too much hassle. Glass is expensive and breaks easily.
So I have some ideas. Suppose we lay down some metal sheets very close to the ground(maybe half an inch above the ground). We paint the top surface of this metal canopy black, so it absorbs sunlight and gets really hot(I think 60 degree Celsius is easily attainable in tropical regions like southern India). We spread these black painted metal sheets over an area of a few square meters(maybe 100). At the centre of this canopy we make a hole and place a 10 feet tall chimney and inside the chimney we place a turbine. So I am hoping that heat absorbed by the metal sheets will be transferred to the thin layer of air underneath the sheets. The hot air will rise through the chimney and rotate the turbine.
The reason I like this device so much is because of its simplicity. It can be built and maintained by people anywhere in the world. There are very few moving parts. And there is no need for complicated devices like heliostats (sun trackers) and heat engines. Of course, this simplicity comes at the cost of efficiency. There is always a trade-off between simplicity and efficiency. But since I plan to build small scale devices, it is better to keep it simple. Plus sunlight is free. So efficiency is not the most important thing.
Your Thoughts?
I urge all those who read this post to share their thoughts on the ideas mentioned above. Also feel free to suggest your own ideas.
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