Technology Status - NET Nowak Energie & Technologie AG

98
Further cost reductions will be possible with Direct Steam Generation (DSG),
which will eliminate the need for the heat transfer fluid system and reduce
the efficiency loss involved with using a heat exchanger to generate steam.
DSG will also improve the solar-field operating efficiency due to lower
average operating temperatures and improved heat transfer in the collector.
Thermal Storage
Thermal storage has made tremendous progress in recent years. The most
advanced thermal-storage technology is the two-tank, molten-salt unit at
Solar Two. This technology has not yet been applied to trough systems, but
studies have shown the feasibility of developing a molten-salt heat transfer
fluid system which will eliminate heat exchanger losses. A thermocline
molten-salt system for both power tower and trough is planned for future
development. The long-term objective is an advanced organic heat transfer
fluid, which will also work as a direct thermal-storage medium. The
advantages of such a system will be a low freezing point, low vapour
pressure, high thermal stability and low cost.
More advanced thermal storage for power tower will include high-temperature
phase change and thermal-chemical approaches to hydrogen generation. Since
the dish/engine system does not include thermal-storage capacity, R&D should
focus on alternative storage systems using batteries or hydrogen.
Concentrators
The solar concentrator is the most expensive feature of a CSP plant. Better
reflective materials, mirror facets, structural design and drives all promise
future cost reductions. New reflective materials hold particular long-term
promise because they may be cheaper and lighter than glass and result in
easier and less expensive manufacturing. Optimisation of concentrator design
will reduce structural costs. One innovative concept under development in
Australia is the Linear Fresnel Reflector that employs nearly-flat mirrors
located very close to the ground. This reduces concentrator wind loads and
increases packing density, both of which could reduce system costs.
O&M
Better operation and maintenance can contribute considerably to reducing
the costs of CSP technology. R&D will focus on construction and control and
communication systems. Maintenance, such as mirror cleaning, must keep
the collector field operating at high levels of efficiency and availability, but
also be inexpensive and easy. Improved methods of installation will be
pursued during the next large-scale project.
CONCENTRATING SOLAR POWER X4