CSP tower

Solar towers capture the sun's energy using a field of plain reflectors called heliostats, each up to 120 m2. These reflect, focus, and concentrate the heat of the sun onto a receptor at the top of a tower that can be between 30m and 250m tall. There are two main types of receiver and the operating temperature (depending on the heat transfer method used) at its hottest can reach as high as 1000 oC.

Volumetric receiver
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.

Cylindrical receiver
This type of receiver extracts the heat through bundles of cylinders where the sun's energy is transferred to the electricity generation system by a Heat Transfer Fluid (HTF). When the HTF is a molten salt, although the inlet temperature is normally less than 300 oC, because the receiver temperature can reach 1000 oC it is possible that the HTF temperature can be well over 500 oC when it leaves the receiver. These temperatures demand the very best in thermal insulation to conserve the thermal energy and prevent heat leakage. For each type of receiver system, the use of a purpose designed Promat HPI system dramatically improves the process efficiency.

Promat HPI is active on different parts of a solar tower plant:

Oven boxes
Mainly insulation systems based on microporous products.

Piping/hot air lines
High temperature bio-soluble wool is used near heating elements backed up by MICROTHERM® MPS and MICROTHERM®-QUILTED or MICROTHERM®-OVERSTITCHED. MONOLUX® or PROMASIL® is used for shaped systems.

Heat storage tanks
Mainly PROMAGLAF® high temperature bio-soluble blankets, MICROTHERM®-QUILTED or MICROTHERM®-OVERSTITCHED, MONOLUX®, PROMABOARD® and PROMALIGHT®. Separation walls use SUPALUX-V®, Calsil/Vermiculite board.

Outside heat shield & backside receiver insulation
Systems based on custom-made SCUTTHERM® systems with extremely low solar absorbance.

Cavity of the receiver area
Systems based on custom-made SCUTTHERM® systems with extremely low solar absorbance.
Parabolic trough reflector system

In the parabolic trough system, the energy of the sun is captured 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. The temperature at the receiver pipe containing a Heat Transfer Fluid (HTF) is around 400 oC.

The challenge of the ball joint assemblies (BJAs) & rotary joint assemblies
Because of the pivoting action of each collector as it follows the path of the sun, special insulated swivelling ball joint assemblies are necessary for connection to other collectors and to the distribution pipes carrying the HTF. The insulation needs to be easily demountable for routine inspections. Systems based on MICROTHERM®-MPS and also flexible jackets made using MICROTHERM®-OVERSTITCHED panels are available.

Fire safety
Because of the risk of leakage of the HTF from the moving parts of the BJA and the possibility of fire due to self ignition from the high operating temperatures, a system of flexible jackets with stainless steel finishing on the hot face has been developed. This ensures that the transfer fluid cannot penetrate the insulation which effectively minimises any fire risk at the joints. MICROTHERM® is completely non-combustible.
Distribution pipe runs & pipe supports

Because of the size of a CSP plant, long runs of interconnecting pipework are necessary to link the various sections of the plant. Excessive heat loss from these pipe runs would seriously reduce the overall operational efficiency of the installation.

Cost effective and the best performance
Microtherm® microporous insulation systems based on moulded pipe sections (MPS) for smaller diameters, and flexible insulation products for larger diameters, offer many advantages:
  • Best performance of any insulation - most compact insulation system available. Easily demountable for routine inspections and replacement.
  • Fast and simple installation. Pre-fabricated bends and other fittings available.
  • Stable performance. Insulation will not deteriorate with time.
  • A bespoke system tailored to the installation.
  • Cost effective in volume when compared to less efficient conventional insulation products. Easier logistics and lower fitting cost due to greatly reduced insulation volume and tailored products - bends as fast to insulate as straight runs.
Pipe supports
As well as insulating all pipework it is essential to prevent heat loss at support points do to thermal bridging by direct metal contact. Microtherm® has excellent compression resistance and will maintain the insulation performance at a support point irrespective of the weight of the pipework involved.