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Steam, Refrigeration, Tin and Aluminium

First published May-2010
last update 27-July-2010


There are already many uses of steam today in plenty of industrial processes, so a solar boiler can be simply piped into many existing systems.

Steam Engine and Stirling Engines
Both steam and sterling engines can provide mechanical power from only a heat source, easily supplied by a solar concentrator, and any waste heat used for a secondary application.

The internal combustion is cheaper than the steam or Stirling engine, as compared to steam there is no boiler or pipe system and so less parts and compared to Stirling an internal combustion engine is easier to build. However an internal combustion requires a liquid explosive to function and cannot function on direct sunlight. This is the reason for the renaissance steam and Stirling engines are currently experiencing. For though a steam and Stirling engine are more expensive to build, if powered with solar energy, the fuel is free, so far cheaper and far less environmentally damaging in the long term.

Before the internal combustion engine half the engines in the world were steam engines and the other half Stirling, but today we are far from having a similar community of steam and Stirling engineers and mechanics around. However, as petroleum depletes and becomes more and ore expensive, if available at all, the existing community of engineers and mechanics for internal combustion can easily re-learn steam and Stirling, as all the knowledge still exists, as well as examples in museums. This process is already occurring, but the sooner a stand alone solar-steam or solar-Stirling system that is obviously cheaper than petroleum, the sooner an explosion of steam and sterling engines there will be.

For both steam and Stirling, the advantage of a fixed focal point is particularly useful, since for steam it allows many relatively small concentrators to be easily coupled together in the same steam system to power a single steam engine. For Stirling engines, which can simply be placed in the focal point, a fixed focal point allows the Stirling engine to not be attached to the concentrator, but rather directly to the ground, significantly reducing vibration problems that could easily destroy the concentrator otherwise.

The reason that before the internal combustion engine half the engines were steam and half sterling, is that both engines have their advantages. Where a steam engine is easier to build than a Stirling, a steam engine requires a boiler and more maintenance. Where a Stirling engine can function for long periods without any maintenance and can be more efficient, they must in general function without lubrication which means a much more precise construction than steam engines, and much more difficult to repair if need be.

Absorption refrigerator

The absorption refrigerator has no moving parts and requires only a heat source to function. For these reasons it is cheap to produce, highly durable, and was the principal refrigeration device for the first half of the 20th century, and still used for off-grid refrigeration today. The disadvantage is that it is less fuel efficient than compression based refrigeration.

However, when the fuel is solar energy which costs essentially nothing, the advantages far outweigh the fuel efficiency factor.

In regions where there is no electricity grid, or electricity is expensive, and compression refrigerators also expensive and difficult to maintain, solar concentration power absorption refrigeration is an ideal solution to extend food stores.

In industrialized nations, absorption refrigeration can significantly increase the autonomy of a household, reduce electricity costs, and at the social level reduce the electricity load on the grid.

A solar concentration can heat directly the input of the absorption refrigerator or steam can be circulated for the job.

Tin and Aluminium

Tin melts at 250°C so can be easily worked in a solar forge.

Though aluminium cannot be refined from ore at low temperatures, once pure it melts at 660 °C so can also be worked with a concentrator relatively easy to construct and for the foreseeable future there is plenty of aluminium to recycled from defunct machines and infrastructure.

Solar aluminium working is of special note since aluminium is the third most abundant substance on earth, and can be used to make solar concentrators, but the mirrors and the structure.

Bronze is 10-20 copper and the rest tin, but though tin can be easily melted, copper melts at about 1000 °C. Existing locally built concentrators can reach 1000 °C, but this is at the focal point and it is yet to be seen how much heat can be transferred to the metal (a focal point of 1200 °C or above may be necessary to heat the copper to 1000 °C), so further development is necessary here to bring copper melting out of the range of advanced applications.

Written by Eerik Wissenz.

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*Chapters in grey are in progress.

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