Solar Mechanical Energy
Mechanical energy can be obtained from solar energy in one of the following ways:
- With a turbine actuated by the air current that is generated by heating air in a solar collector and allowing it to rise due to its buoyancy in a very high tower (the solar tower).
- Through an electric motor actuated by photovoltaic panels exposed to solar radiation. The cost of the energy obtained this way is quite high because of the high cost of the photovoltaic panels.
- Through a thermal engine having solar energy as its heat source. That may be a Stirling engine, or it can be a turbine system
- Through the pressure exerted by light on solid surfaces. This is a very weak effect that may be employed by the future sail-spaceships.
- Through differential thermal expansion of solid bodies alternatively exposed to solar radiation and shade (or other cold sink). Although the needed machinery is very reliable, it is very bulky and expensive, resulting in expensive mechanical energy.
The solar tower (previously called 'solar chimney')
This is basically an artificial wind generator that uses the solar energy and the inverted temperature gradient of the lower parts of the troposphere to generate a pressure difference between the ends of a high tower.
One of the first description of this method of obtaining mechanical or electrical power from solar energy was given by the German engineer Jorg Schlaich more than 25 years ago. The engineering firm Schlaich Bergermann und Partner has built in cooperation with departments of the German and Spanish governments an experimental solar tower at Manzanares, in Spain, that had a mechanical power of about 70kW and was tested between 1982 and 1989.
Classically, a solar tower consists of an impermeable transparent cover that allows the solar radiation to heat the ground or objects placed on it (see figure below).
The ground is used as a heat accumulator that receives the heat from the sun during the day and releases it during the night, also allowing functioning during the night . A relatively recent innovation of the German firm is to place water-filled bags on the ground to increase the heat retention and to spread the power generation more evenly during the 24 hours of the day.
The tower may be built from a large variety of materials. The 195m high and 10m diameter tower of the Manzanares prototype plant was made out of corrugated steel sheeting.
Q Solar has developed new solar collectors for the solar towers that have higher performances.
Our innovation
We have designed a different kind of solar collector for the solar tower.
The advantages of using our solar collectors for solar tower instead of the classical ones are:
- Less affected by hail
- Requires a simpler and more economical supporting structure
- Simpler solution to rainwater drainage
- Less influenced by dust
- Not affected by fine particles abrasion (as the classical covers are)
- Higher resistance to the wear and tear produced by wind
- More economical
Given the very large size of the solar collector for a solar tower, we designed solar collectors that:
- can withstand the most adverse conditions: hail, sand storms, torrential rains, strong winds
- need little or no maintenance despite said adverse conditions
- the materials they are made of are environmentally friendly (recyclable)
- last for many years
- their cost is within economical limits
The mechanical energy of the shaft of the turbine can be used for actuating many devices, not only electric generators. For example, the turbine can be directly coupled to water pumps, grain grinding devices, or many other devices that require mechanical energy.
Moreover, the high tower could be used as support for a wind turbine, so that mechanical energy would still be available during cloudy and windy weather.
Solar towers are especially suitable for sunny and remote areas with low land values, like the Australian Outback or other desert areas of the world.
Since 2001 we have designed and tested hundreds of materials for the solar collector of the solar tower. The successive improvements have provided viable solutions for:
- storm dust influence,
- pressure gradient with distance from the tower,
- ease of installation
- ease of maintenance and repair,
- suitability to the entire area of the solar collector
- service life
The thorough assessment of the properties of our solar collectors have shown them as the single economical and environmentally friendly option for a solar tower. Q Solar Pty Ltd is proud to be the promoter and the developer of this new technology for the solar tower.