In the ST plants, a large number of computer assisted mirrors (heliostats) track the sun individually over two axes and concentrate the solar irradiation onto a single receiver mounted on top of a central tower where the solar heat drives a thermodynamic cycle and generates electricity. In principle, ST plants can achieve higher temperatures than PT and FR systems because they have higher concentration factors.
The ST plants can use water-steam (DSG), synthetic oil or molten salt as the primary heat transfer fluid. The use of high-temperature gas is also being considered. Direct steam generation (DSG) in the receiver eliminates the need for a heat exchanger between the primary heat transfer fluid (e.g. molten salt) and the steam cycle, but makes thermal storage more difficult. Depending on the primary heat transfer fluid and the receiver design, maximum operating temperatures may range from 250-300°C (using water-steam) to 390°C (using synthetic oil) and up to 565°C (using molten salt). Temperatures above 800°C can be obtained using gases. The temperature level of the primary heat transfer fluid determines the operating conditions (i.e. sub-critical, super-critical or ultra-super-critical) of the steam cycle in the conventional part of the power plant.
ST plants can be equipped with thermal storage systems whose operating temperatures also depend on the primary heat transfer fluid. Today’s best performance is obtained using molten salt at 565°C for either heat transfer or storage purposes. This enables efficient and cheap heat storage and the use of efficient super-critical steam cycles. High-temperature ST plants offer potential advantages over other CSP technologies in terms of efficiency, heat storage, performance, capacity factors and costs. In the long run, they could provide the cheapest CSP electricity, but more commercial experience is needed to confirm these expectations
Current installed capacity includes the PS10 and PS20 demonstration projects (i.e. Spain) with capacities of 11 MW and 20 MW, respectively. Both plants are equipped with a 30-60 minute steam-based thermal storage to ensure power production despite varying solar radiation .
The PS10 consists of 624 heliostats over 75,000 m2
Its receiver converts 92% of solar energy into saturated steam at 250°C and generates 24.3 GWh a year (i.e. 25% capacity factor), with 17% efficiency. In Spain, a 19-MW molten salt-based ST plant
with a 15-hour molten salt storage system started operation in the second half of 2011. It is expected to run for almost 6,500 operation hours per year, reaching a 74% capacity actor and producing fully dispatchable electricity.
Larger ST plants are under construction (e.g. the 370-MW Ivanpah project in California with water-steam at 565°C and 29% efficiency and the 50-MW Supcon project in China) or under development (e.g. eight units with a total capacity of 1.5 GW in the southwestern United States). Large plants have expansive solar fields with a high number of heliostats and a greater distance between them and the central receiver. This results in more optical losses, atmospheric absorption and angular deviation due to mirror and sun-tracking imperfections.
The ST plants can use water-steam (DSG), synthetic oil or molten salt as the primary heat transfer fluid. The use of high-temperature gas is also being considered. Direct steam generation (DSG) in the receiver eliminates the need for a heat exchanger between the primary heat transfer fluid (e.g. molten salt) and the steam cycle, but makes thermal storage more difficult. Depending on the primary heat transfer fluid and the receiver design, maximum operating temperatures may range from 250-300°C (using water-steam) to 390°C (using synthetic oil) and up to 565°C (using molten salt). Temperatures above 800°C can be obtained using gases. The temperature level of the primary heat transfer fluid determines the operating conditions (i.e. sub-critical, super-critical or ultra-super-critical) of the steam cycle in the conventional part of the power plant.
ST plants can be equipped with thermal storage systems whose operating temperatures also depend on the primary heat transfer fluid. Today’s best performance is obtained using molten salt at 565°C for either heat transfer or storage purposes. This enables efficient and cheap heat storage and the use of efficient super-critical steam cycles. High-temperature ST plants offer potential advantages over other CSP technologies in terms of efficiency, heat storage, performance, capacity factors and costs. In the long run, they could provide the cheapest CSP electricity, but more commercial experience is needed to confirm these expectations
Current installed capacity includes the PS10 and PS20 demonstration projects (i.e. Spain) with capacities of 11 MW and 20 MW, respectively. Both plants are equipped with a 30-60 minute steam-based thermal storage to ensure power production despite varying solar radiation .
The PS10 consists of 624 heliostats over 75,000 m2
Its receiver converts 92% of solar energy into saturated steam at 250°C and generates 24.3 GWh a year (i.e. 25% capacity factor), with 17% efficiency. In Spain, a 19-MW molten salt-based ST plant
with a 15-hour molten salt storage system started operation in the second half of 2011. It is expected to run for almost 6,500 operation hours per year, reaching a 74% capacity actor and producing fully dispatchable electricity.
Larger ST plants are under construction (e.g. the 370-MW Ivanpah project in California with water-steam at 565°C and 29% efficiency and the 50-MW Supcon project in China) or under development (e.g. eight units with a total capacity of 1.5 GW in the southwestern United States). Large plants have expansive solar fields with a high number of heliostats and a greater distance between them and the central receiver. This results in more optical losses, atmospheric absorption and angular deviation due to mirror and sun-tracking imperfections.
Nice post about solar energy
ReplyDeleteThanks for sharing such post
Energy Saving Consultants
Renewable Energy Consulting Firms