High temperature heat transfer fluids previously used in other, more traditional applications are quickly becoming the heat transfer fluid of choice for concentrating solar power (CSP) applications - powerhouse installations that harness the heat of the sun and convert it into electricity. Facilities in the United States and Spain already are generating electricity using CSP technology. As the popularity of this type of solar power is increasing, more demand for these fluids is expected.
CSP technology predominantly uses parabolic mirrors to reflect and concentrate sunlight onto receivers that collect solar energy and convert it to heat. The role of heat transfer fluids is to collect the heat energy and transport it to a power-generating station. The transported heat converts water to steam, which in turn drives turbines to make electricity.
The CSP technology helps to diversify energy supply and is capable of producing power during periods of peak demand, while reducing dependence on fossil fuels. When used instead of fossil-fuel-based generation plants, CSP facilities offer improved air quality and can help many nations meet off-set goals for carbon emissions produced by existing fossil fuel power plants.
Already in UseThe heat transfer fluids best suited for these applications are those with the high temperature stability required to collect, transport and store heat. Other requirements include good heat transfer properties, low energy transportation losses, low vapor pressure, low freeze point, low hazard properties and economical maintenance costs. Fluids with the ability to manage temperatures up to 750°F (400°C) are best for this application.
When determining the viability of heat transfer fluids for CSP applications, there are four important properties that help determine the viability of a heat transfer fluid. These are:
Stability. Look for thermal
stability at temperatures up to 750°F (400°C.) The maximum recommended
film temperature is 800°F (425°C).
Vapor Pressure. Vapor-phase heat
transfer applications range from 495 to 750°F (257 to 400°C). The
better fluids may be used in the liquid phase from 60°F
Point. Look for a freezing point of 53.6°F (12°C). Fluid and
can be used without steam tracing in installations protected from the
- Viscosity. The viscosity of the preferred fluid is low and changes only slightly between the melting point of the product and its top operating temperature. As a result, startup problems are minimized.