Preparing For Energy Shortfalls: How To Harness Hydropower
Feb 27th, 2012 | By Andrew | Category: Energy, Water | Print This Article
The search for home energy alternatives has been heating up in recent years, thanks to high utility costs, undependable service, and a general desire to return to a more authentic and sustainable style of living. This has helped stimulate mini-booms in small-scale wind and solar, and it has even helped rejuvenate wood burning, the oldest form of heat and energy generation known to man. But there is another ancient technology that offers great promise to at least some homesteaders and hardy modern-day pioneers, and it is high time people began to rediscover this very neat and very interesting form of energy generation.
Hydropower is not something that would come to the minds of most off-the-gridders. After all, it takes a big effort and a big scale to harness the energy potential hidden in water, which is why when people think of hydropower they normally think of heavily capitalized mega-projects such at Hoover Dam or the Tennessee Valley Authority. But moving water can be made to do some very interesting and useful things, not all of which require a grand scale or a massive investment of resources. Would you believe, for example, there is a way to get free air conditioning simply by using the basic principles behind hydropower generation to cool and compress a steady and easily deliverable supply of air? And would you believe that in order to make such a system work you would theoretically need to capture no more than three gallons of water per minute?
Well, such a system does exist – and not only can it be constructed and installed cheaply, but it can continue to function without any further outside power inputs for literally decades. This system is called a trompe, and any family fortunate enough to have a source of running water on their farm or homestead should start educating themselves about this ancient little marvel of nature post haste.
The Ancient Power of the Trompe
Falling water has the potential to move the turbines in electric generators, and this is the secret behind hydroelectric power. But it is another useful characteristic of moving water that is exploited inside of a trompe. Anytime flowing water can be redirected through a narrow channel, like a thin pipe, for example, this sudden act of constriction causes a reduction in fluid pressure. This is known as the Venturi Effect, after the eighteenth century Italian physicist who discovered it, and when fluid pressure is decreased, water will absorb bubbles of air from the surrounding atmosphere. Interestingly, even though the Venturi Effect wasn’t “officially” discovered until the 1700s, trompes have been around since the Iron Age, meaning the technology is at least 2,500 years old.
The first section in a trompe is a downshaft or standpipe, which is a length of pipe that runs vertically under the ground from directly beneath a waterfall or the bed of a running stream. The standpipe will have a wide funnel-shaped top that helps it capture the running water, but the pipe then quickly narrows and constricts the flow, thereby lowering fluid pressure. This makes it possible for the water to absorb bubbles of air, which flow in through small inclined tubes that extend out from the standpipe, rise up through the ground, and open up into the atmosphere. The added air is then carried along as the water descends through the downshaft and falls to the bottom, where it is redirected into another length of attached pipe that runs horizontally. This horizontal section of pipe is wider than the downshaft, which ends constriction and allows fluid pressure to return to normal. The air bubbles that had been transported from outside are then released from the water, leaving them free to flow down the length of the horizontal pipe above the water in a separate channel of air.
As water moves to the end of this stretch of pipe, the water pressure built up behind it will push it upward and out through a vertical exit shaft, so once water begins to flow through a trompe it will do so continuously for as long as the system is left in place. But the most important part of the trompe is a reservoir that is connected to the horizontal section. Here, the added air that has been separated from the water will be held under pressure before being released through an escape nozzle. This highly compressed cool air, which will be at the same temperature as the water, can then be piped indoors, where it can function as a completely cost-free form of totally natural air conditioning. As long as the water temperature is lower than the temperature of the pipes, any moisture held in the air will be reabsorbed by the water, meaning that the air pressurized and released in the reservoir will be very dry as well as being cool.
A trompe reservoir must be fitted with a blow-off valve to get rid of excess pressure anytime the escape nozzle is closed off and the system is not in use. The opening of this valve should be located just below the surface of the water flowing through the pipe, so that when pressure builds up too much, it will cause the water level is drop and allow the pressurized air to escape.
Nature Always Provides
Trompes are the ultimate do-it-yourself project, and just about any materials that are capable of holding water without breaking or eroding quickly can be used to build one. Even though the technology has become rather obscure, it is not completely unknown, so it should not be too difficult to find advice and guidance in the art of trompe construction in online forums and websites devoted to off-the-grid living.
Besides just providing compressed air, trompes can also be used to pump water for irrigation or other purposes, although the characteristics of devices used for this task might be somewhat different than what has been described here. Some have even speculated that compressed air created in a trompe could be used to power machinery, and this is certainly true in principle. However, air would have to be compressed to something in the neighborhood of 50-150 psi to deliver enough force to effectively turn a motor, and this would be problematic in a homemade trompe. With this technology, it is the energy produced by water cascading down the standpipe that determines the intensity of the compression process, and you are generally only able to compress air at about 15 psi for every 35 feet of downshaft fall. Of course, do-it-yourselfers are well known for their ingenuity and love of tinkering, so who is to say what kind of power-boosting trompe modifications might prove to be possible once this technology starts to come back into wider use?
We are constantly bombarded with stories about future energy shortages and crises. But we must remember – scarcities are man-made; they are not found in nature. God gave us everything we need to take care of ourselves and to live in abundance, and when shortages occur it is only because of inefficiencies in the way man and society have chosen to organize their activities. Because trompes are cheap, easy to construct, and operate as perpetual motion machines with no additional sources of power required, they could never be profitable for big business or the energy companies, which is almost certainly why most have never heard of this technology before. But the power of water is readily available everywhere water flows, and for those with a source of moving water on their land, constructing a trompe could prove to be an eminently practical undertaking – not to mention a lot of fun.
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