SMALL HELIOSTATS CSP SYSTEMS ON LONG-SPAN HANGING ROOFS

Building Integrated Concentrating Solar Power (BI-CSP) schematic studies with small scale exterior two-axis tracking heliostats anchored on and semi-shading long span hanging roofs with elevated receiver(s) are presented for populated urban and rural locations. Hanging roofs (inverted shallow dome shape) with two-way structural cables and mostly square infill prefabricated slabs/panels supported from a perimeter horizontal circular donut shape rim-girder-platform without a center tension ring studies are for comparing to radial cable structural configurations with a center tension ring. Cable gap grouting between slabs/panels form a pre-tensioned inverted shell structure after temporary weights are removed. Securing vertical heliostat posts studies include: three vertical bolts cast in grout gap two-way cables intersections for three point adjustment of horizontal post base plates;and one-axis adjustable manu­factured post brackets bolted to sloped roof surfaces at holes cast in the gaps/slabs. A main case study schematic is around a 30m/100ft diameter hanging roof with a 0.07 sag/diameter ratio with around 271 1m2 heliostats for 230kWt solar thermal steam or air to around 300degC/572degF building integrated thermal energy storage (molten salt, firebricks, etc.) and applications (water purification, cooling, industrial process heat, etc.). A BI-CSP hanging roofs R&D project proposal is outlined: with a circular roof study diameter range of around 25m/82ft-200m/656ft diameter for comparing two-way and radial cable structural configurations for distributed steam stations and a wide range of application temperatures.

Three-degree-of-freedom Parallel Manipulator to Track the Sun for Concentrated Solar Power Systems

In concentrated solar power（CSP） generating stations, incident solar energy is reflected from a large number of mirrors or heliostats to a faraway receiver. In typical CSP installations, the mirror needs to be moved about two axes independently using two actuators in series with the mirror effectively mounted at a single point. A three degree-of-freedom parallel manipulator, namely the 3-RPS parallel manipulator, is proposed to track the sun. The proposed 3-RPS parallel manipulator supports the load of the mirror, structure and wind loading at three points resulting in less deflection, and thus a much larger mirror can be moved with the required tracking accuracy and without increasing the weight of the support structure. The kinematics equations to determine motion of the actuated prismatic joints in the 3-RPS parallel manipulator such that the sun＇s rays are reflected on to a stationary receiver are developed. Using finite element analysis, it is shown that for same sized mirror, wind loading and maximum deflection requirement, the weight of the support structure is between 15% and 60% less with the 3-RPS parallel manipulator when compared to azimuth-elevation or the target-aligned configurations.

Evaluation of survival stow position and stability analysis for heliostat under strong wind

Heliostats are sensitive to the wind load, thus as a key indicator, the study on the static and dynamic stability bearing capacity for heliostats is very important. In this work, a numerical wind tunnel was established to calculate the wind load coefficients in various survival stow positions. In order to explore the best survival stow position for the heliostat under the strong wind, eigenvalue buckling analysis method was introduced to predict the critical wind load theoretically. Considering the impact of the nonlinearity and initial geometrical imperfection, the nonlinear post-buckling behaviors of the heliostat were investigated by load-displacement curves in the full equilibrium process. Eventually, combining B-R criterion with equivalent displacement principle the dynamic critical wind speed and load amplitude coefficient were evaluated. The results show that the determination for the best survival stow position is too hasty just by the wind load coefficients. The geometric nonlinearity has a great effect on the stability bearing capacity of the heliostat, while the effects of the material nonlinearity and initial geometrical imperfection are relatively small. And the heliostat is insensitive to the initial geometrical imperfection. In addition, the heliostat has the highest safety factor for wind-resistant performance in the stow position of 90-90 which can be taken as the best survival stow position. In this case, the extreme survival wind speeds for the static and dynamic stability are 150 m/s and 36 m/s, respectively.

Simulation Study of Heliostat-Based Daylighting System for Multi-Story Buildings

The following article has been retracted due to the fact that it cannot be accepted as Duplicate Publication. The Editorial Board takes a very strong respect to the author’s situation on this matter. This paper published in Journal of Power and Energy Engineering Vol.3 No.4, April 2015, has been removed from this site.

Complete Solution of Sun Tracking for Heliostat

A general solution of sun tracking for an arbitrarily oriented heliostat towards an arbitrarily located target on the earth is published. With the most general form of solar tracking formulae, it is seen that the used azimuthelevation, spinning-elevation tracking formulae etc. are the special cases of it. The possibilities of utilizing the general solution and its significance in solar energy engineering are discussed.

Experimental Small Scale Solar Power Tower in Iraq

Solar energy is the most available, clean and inexpensive source of energy among the other renewable sources of energy. This work deals with experimental steady to determent the performance of solar tower steam production for power generation. Designed and fabricated of a solar tower, consist of a central receiver tank （0.4 m × 0.6 m × 1.0 m） and 150 heliostat mirrors arranged around it. The central tank was made of galvanized steel. Each heliostat consisted of two （0.5 m × 0.5 m） mirrors. The results of this work produce steam at temperature 110 ℃. Large steam quantity could be obtained when using large scale experimental. The results of the work give good indication for application of solar energy to produce power in Iraq.

Overview of Concentrated Solar Power

CSP （concentrated solar power） has been viewed as the technology that if properly developed could lead to a large scale conversion of solar energy into electricity. CSP is a type of solar energy converter that is classified as thermal converter because the output power produced is a function of the operating temperature. The main components of a CSP plant are the solar field which is made up of the heliostat arrays, the receiver tower, the heat transfer fluid, the molten salt thermal energy storage tanks and the power conversion unit, which is made up of the turbine and the generator. The main advantage of CSP is that of a cheap thermal storage （i.e., molten salt storage） which makes it possible to dispatch power at a cost comparable to the grid electricity. Simulations run with the SAM （systems advisory model） developed by NREL （National Renewable Energy Laboratory） showed that CSP is capable of delivering electricity at the cost of 17UScents per kWh for the 30-year life of the plant. The main disadvantage of CSP however, is that of low efficiency （8%-16%）. There are ongoing research works to improve the efficiency of the CSP. One way to improve the efficiency is to increase the operating temperature of the system. In this paper, the authors discussed different modules of the CSP plant and suggested ways to improve on the conversion efficiencies of individual modules. Finally, an overall systems performance simulation is carried using SAM and the simulation results show that electricity can be produced using CSP at the cost of RI.05 per kWh.