Green energy – Microtherm® insulation in Concentrated Solar Power (CSP)
Microtherm® - the insulation of choice for Concentrated Solar Power (CSP).
CSP – Optimised energy efficiency with Microtherm® thermal insulation solutions – the most compact insulation systems available.
Concentrated Solar Power is being developed in many of the hot regions around the world. It offers an endless supply of renewable energy. For many of the specialist companies dealing in this field, Microtherm® is now the preferred insulation for the most compact and thermally efficient systems that also offer the best return on investment.
What is Microtherm®?
Microtherm® is a microporous insulation that is around 90% air, but with the air contained in minute cells, or pockets, that are smaller in average size than the mean free path of an air molecule. This characteristic almost completely eliminates gaseous conduction. It also means that Microtherm® is a very low density insulation offering very lightweight systems.
Microtherm® is made from amorphous Silica particles many thousand times smaller in diameter than a human hair. The small area of these nano sized particles, which chemically bond together into long tangled chains, almost completely eliminates solid conduction through the insulation.
Also present is a mineral oxide opacifier that effectively stops heat transfer by radiation by repeatedly refracting penetrating waves of infra red so that they cannot pass through the insulation.
Add all of these characteristics together and you have an insulation that is more efficient at blocking heat than still air!
What does this mean?
It means quite simply that Microtherm® is easily the best insulation available for high temperatures and also for use at ambient and low temperatures. Microtherm® has a clearly superior performance to all conventional insulation materials including Aerogel blanket as shown in our chart comparing the TCs of various insulations.
Renewable energy – Concentrated Solar Power
There is a growing global awareness that current energy trends are not sustainable and renewable energy sources are the most attractive option. Of all the newer alternative green energy sources currently being developed, Concentrated Solar Power (CSP) is probably the most attractive because of the unlimited solar energy reserves available in the sunny regions of the world.
The principle of CSP is very simple. Solar energy is collected by means of a system that focuses and concentrates the thermal energy onto a point where it can be collected and transferred for use, usually by conversion to steam for conventional turbine generation of electricity. The thermal energy is collected throughout daylight hours and can be stored in special heat storage systems to extend the working period for electrical power generation.
There are several systems in use around the world for collecting the solar energy. The two of most immediate interest for the use of Microtherm® are the "parabolic trough" system and the "solar tower".
In the "parabolic trough" system, the energy is harnessed by a collector field consisting of many parallel rows of solar collectors, each of which can swivel on the N-S axis to enable it to follow the path of the sun overhead. Each collector is a linear parabolic shaped reflector that focuses the sun's direct beam radiation onto a receiver pipe positioned at the focus of the parabola. Temperature at the receiver is around 400 °C (750 °F).
The most difficult areas to insulate in a parabolic trough system are the ball joint assemblies. Because of the swiveling action of the reflector, special swiveling ball joint connections are necessary as these connect the different collectors to each other and to the distribution pipes carrying the Heat Transfer Fluid. As the collectors rotate over a N-S axis to track the sun during daytime, the insulation of these ball joint assemblies needs to be flexible enough to allow this movement.
Our first involvement in the CSP market was in the test facility Plataforma Solar de Almeria, where Microtherm® Overstitched Panel was used as the thermal component of a flexible jacket system fitted to the ball joint assemblies. As well as being flexible, these jackets are quickly demountable for routine maintenance inspections. This solution is in use in some of the first commercial plants in Spain.
Because of the possibility of leakage of Heat Transfer Fluid (HTF) and corresponding fire by self ignition from the high temperatures in the system, a new system of flexible jackets with a stainless steel finishing on the hot face has been developed. This ensures that the transfer fluid cannot penetrate into the Insulation. In this way the system effectively minimizes any risk of fire at and around the ball joints.
For future projects, one of our partners in the Solar market, Aislamientos Suaval, has developed a new solution for the insulation of the ball joint assemblies using Microtherm® MPS (moulded pipe sections) which are finished with an aluminium or stainless steel outer cladding.
Both systems based on Microtherm® are by far the best ball joint insulation systems currently available. Although they are slightly more expensive than competing systems they prove cost effective due to greatly reduced maintenance costs and simplified fitting. They offer a very attractive ROI together with a number of other advantages:
- Best thermal insulation; decrease heat losses by at least 30-40% with correspondingly higher electricity production
- One layer system and easy to install, this lowers the installation cost
- No degradation over time, achieves lifetime of solar plant
- Non combustible
- 100% recyclable
- No health hazards
Control of energy loss throughout the system is of paramount importance. For optimised thermal efficiency of the complete solar plant, Microtherm® offers a complete range of products to insulate all transfer pipe work and connections, pipe supports, etc. ... .
The use of Microtherm® ensures the thinnest possible insulation system combined with fast assembly and easy maintenance for best ROI.
The "solar tower" system of collection is slightly different.
Solar towers use a field of reflectors called heliostats, each up to 120 m² in size, to focus and concentrate the heat of the sun onto a receptor at the top of a tower, possibly up to 150 meters tall. There are two types of receiver and depending on the heat transfer fluid used, the operating temperature can reach 1000 °C (approx 1830 °C).
A volumetric receiver is essentially a huge ceramic mesh that transfers heat energy by a forced air system which draws the air through the mesh for feeding to the steam generation cycle.
A cylindrical receiver extracts the heat through bundles of cylinders where the energy is transferred to the generation system by HTF. When the HTF is molten salt, the inlet temperature is 290°C, but because the temperature in the receiver can easily reach 1000°C it is possible to attaina much higher temperature of 565°C when the heated fluid leaves the receiver.
Because of these high temperatures at the receiver, it is of the utmost importance that the very best thermal insulation is used. Again this is where Microtherm® microporous insulation is the insulation of choice.
For each type of collection system, the use of Microtherm® dramatically improves the process efficiency.
Further information can be found in our downloadable brochure 'Microtherm - insulation for concentrated solar power'.