Technology

General | System Overview | Heliostat | Air Receiver  | Thermal Storage

General

The enormous potential of Solar Thermal Power is about to be realized through the significant improvements in efficiency and thermal storage achieved by Regenesys’ proprietary technology. The thermal storage allows power to be generated at night time and the efficiency improvements result in significant cost reductions.

The collectors in any solar thermal power system (whether they be troughs, heliostats or dishes) represent the major part of the cost of the system. Any improvements made in the overall efficiency of the system will enable a smaller collector field to deliver the same electrical output. In this way, increasing the efficiency has a dramatic effect on the overall cost of the system which in turn results in cheaper electricity.

A consequence of the Second Law of Thermodynamics is that system efficiency is proportional to temperature. A system operating at a higher temperature will be a more efficient system. Systems that use oils are limited to 400degC, steam and molten salts are limited to about 500 to 600degC. Even at these temperatures oils and molten salts are highly dangerous materials, not to mention highly toxic and polluting. Steam at temperatures greater than 500degC also exerts massive pressures that cause materials problems.

Air and rocks are one of the few substances that can be taken to 1000degC and beyond and yet remain safe, stable and benign.

Advantages

 A system running on high temperature air has a number of significant advantages over other solar thermal power systems including

• The ability to store high temperature heat and have 24/7 power on demand
• The ability to run on a gas turbine, the most efficient of all thermodynamic heat engines
• The ability to run without the cooling water usually seen in systems running on Rankine Cycle steam turbines. No water is required to run a gas turbine meaning that the plant can be situated almost anywhere in Australia
• The potential to run on a combined cycle operation with thermal to electric efficiencies approaching 60%. No other solar system currently running in the world can come close to these efficiencies.  Solar thermal plants that run on steam are down around 35% (turbine only), the best gallium arsenide photovoltaic systems are around that figure also.

System Overview

The major components of the system are:

• Heliostats which concentrate the sunlight
• Air Receiver providing 1000degC air
• Hot Rock storage system
• Heat Recovery Heat Exchanger
• Gas Turbine and generator to produce power

Heliostat

A heliostat has been developed using unique construction techniques that save on materials usage and commissioning times. The heliostat works by making each mirror panel spherically curved so that it concentrates the light to a circular zone. A high level of focusing and tracking precision is required to achieve the concentration ratio exhibited by each heliostat. Each heliostat is required to focus light into a circle with an approximate diameter of 2m. For an 84sqm heliostat this represents a concentration ratio of about 30:1.

Air Receiver

The air receiver is constructed from a heat resistant ceramic the purpose of which is to convert concentrated sunlight into heat that can be taken up by an air stream. Due to the low conductivity of air, the receiver has been designed to present a very large surface area to the air stream yet still retain structural integrity in the face of the concentrated solar flux and thermal shocks.

Thermal Storage

Thermal storage systems have been the Achilles heel for solar thermal systems. Many products have been used however they all have their limitations not the least of which is their cost. The use of air as the heat transfer medium enables heat to be stored in one of the cheapest and most effective materials on Earth, rocks. If you think of your backyard BBQ you will be aware that rocks can be repeatedly heated to very high temperatures by hot gases. Very few materials can actually do this without oxidizing, melting, expanding, exploding, reacting or degrading. Another way of thinking about this is to picture it as an above ground geothermal system that is based on air rather than steam.