Patent Publication Number: US-2018041038-A1

Title: Hybrid power generation station

Description:
FIELD OF THE INVENTION 
     The present invention relates in general to hybrid renewable power generation and in specific to combining solar and wind systems. 
     BACKGROUND OF THE INVENTION 
     Solar and wind energy have incredible potential for electricity production. Over the years, industries have made several attempts to harvest wind and solar energy with high efficiency. 
     Concentrated Solar Power (CSP) energy systems convert sunlight into electricity using parabolic mirrors. The concentrated solar energy is either focused on a photovoltaic module, or a heat receiver that absorbs the solar energy and transfers it to a working fluid such as a high temperature oil, molten salt, or hydrogen. 
     The most widely used CSP technology utilizes a large number of parabolic trough having parabolic mirrors with a common focal point. The troughs are arranged in a large space and usually in a number of rows. A receiver pipe at the focal point of the parabolic troughs absorbs the concentrated solar energy. Power towers are another CSP technology that could become more economical than parabolic troughs by using a field of mirrors to focus on a central receiver that boils water for a standard steam cycle. 
     Thermal storage can be used in these systems to provide electricity during peak hours or when the sun intensity is low. The storage tanks can use molten salts for indirect heat exchange systems. The molten salt storage tanks offer an inexpensive means of storing solar energy in comparison to other storage media such as batteries with higher lifetime and efficiency. 
     High concentrating photovoltaics (HCPV) have recently become the most energy efficient technology to convert solar energy into electricity. HCPV systems employ concentrating optics consisting of dish reflectors or Fresnel lenses that concentrate sunlight to intensities of 1,000 suns or more. The multi junction solar cells require high-capacity active cooling system to prevent thermal destruction and to manage temperature related electrical performance and life expectancy losses. 
     The current technologies have several drawback: Sun energy is diluted; large scaled photovoltaic (PV) plants require large land usage due to their low efficiency, therefore, the cost of collecting system is increasing with the increased scale. 
     The wind and solar outputs are intermittent and uncontrollable, if no storage exists. 
     The CSP technologies, such as parabolic trough and power tower, have low converting rate and high cost, and do not work with diffused light. Silicon cells cannot absorb all sun spectrums, and therefore, their efficiency is low. The uncollected spectrums are converted to heat radiation and are wasted. 
     Concentrated photovoltaic has higher efficiency but also higher cost due to the active cooling and two-axes tracking system. The thermal generated by cooling system cannot be easily converted to electricity because HCPV cell require low temperature to have the best performance. However, the cost can be lowered by increasing the scale. Also increasing the aperture size will increase the amount of solar radiation intercepted by the receiver, but also will increase the losses due to convection and radiation out of the aperture. Convection and radiation decrease the effective radiative energy absorbed in the receiver. 
     Despite these limitations, combination of wind and solar energy can be a perfect match, since normally when the sun is shining there is little wind, and at night time and cloudy days there is more wind. 
     With a proper storage, the wind-solar combined system can provide continuous power output to meet the fluctuation in the load demand. The system can be easily built in large scales with less land, e.g. one wind tower can be 5-8 MW and the solar energy can be 1 kW/m 2 . The efficiency of the solar energy converted to electricity can be above 70% with storage, since the invisible spectrum of the sun light is used to generate heat and be stored in a molten salt heat storage. The cooling water of the HCPV solar cell can be used as preheated water, which is heated up later by molten salt for steam turbine. In the existing photovoltaic conversion systems, the heat is normally wasted. 
     SUMMARY OF THE INVENTION 
     The present invention is a combination of wind and solar energy to achieve higher efficiencies, larger scale and controllable power output with lower cost. The system basically comprises of three portions.
         1. Wind turbine integrated with centralized HCPV receivers system mounted on the tower;   2. Fixed focus dish solar concentrator with solar spectra splitting technology for both photovoltaic (visible light) and thermal storage (invisible light); and   3. Molten salt thermal storage and conventional steam generator.       

     The system utilizes a plurality of parabolic mirrored solar receptors which focus solar energy into a lens, which lens focuses visible spectrum light to a aiming mirror for aiming at a central wind tower, and which reflects the rest of spectrum light to a receptor for heating molten salt. Molten salt is also heated by PV cell installed at the back of the parabolic mirror from catching the diffused light. The visible light which is reflected by the aiming mirror is aimed at a receptor on the tower of a wind turbine, which receptor is also for high concentrated photovoltaic with heating cooling water. In return, the heated water (around 90 degree) from the cooling system can later be further heated up by the stored molten salt and utilized for electrical generation through standard techniques. 
     Since the visible light is redirected to a wind tower for HCPV cells to generate electricity so that the cost on collecting the electricity is minimized. In addition, other equipment, such as inverter step up transformer, cooling systems can also be minimized through this centralized arrangement. 
     Fixed focus solar dish collector is used to collect the direct sunlight radiation, an optical means with IR reflection on one side is used to split the spectrum to allow the visible light passing through the optical means and form a parallel incident light while the other spectrum reflecting back to the center of the dish. Visible light can then be re-directed and aim to the HCPV receivers on wind tower for photovoltaic, and the rest are used for thermal storage through conventional CSP technology. The back side of the dish has enough space to install thin film solar cells to catch the diffused light for thermal storage. This may further increase the efficiency of the sunlight use. 
     The parallel incident light will be redirected to the aiming mirror mounted 6 meter above the focal point by a stretchable mirror, when dish moves to track the sun, the mirror will also change the length and angle to reflect all the light to aiming mirror. 
     The present invention can be used for expansion of the existing wind farms by adding solar collecting yard, thermal storage and steam turbine or retiring the existing end of life fossil fuel generation stations by keeping the conventional portion and adding the renewable portion. The present invention is a centralized renewable hybrid power generation technology matches the need of the existing bulk grid and transmission system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments herein will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the scope of the claims, wherein like designations denote like elements, and in which: 
         FIG. 1  shows a schematic diagram of an embodiment of the present invention; 
         FIG. 2  shows a perspective view of a solar dish collector of the present invention; 
         FIG. 3  shows a side view of a solar dish collector of the present invention; 
         FIG. 4A  shows a perspective view of an optical means of the present invention; 
         FIG. 4B  shows a side view of an optical means of the present invention; 
         FIG. 4C  shows a side view of an optical means of the present invention; 
         FIG. 5A  shows a perspective view of a light reflector of the present invention; 
         FIG. 5B  shows a side view of a light reflector of the present invention; 
         FIG. 6A  shows a top view of the light reflector with the bearing system; 
         FIG. 6B  shows a side view of the light reflector with the bearing system; 
         FIG. 7  shows a wind turbine and a plurality of HCPV receiver installed at wind tower; and 
         FIG. 8  shows a wind turbine and a plurality of solar dish collectors of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The figures are not intended to be exhaustive or to limit the present invention to the precise form disclosed. It should be understood that the invention can be practiced with modification and alteration, and that the disclosed technology be limited only by the claims and equivalents thereof. 
     The technology disclosed herein, in accordance with one or more various embodiments, is described in detail with reference to the following figures. The drawings are provided for purposes of illustration only and merely depict typical or example embodiments of the disclosed technology. These drawings are provided to facilitate the reader&#39;s understanding of the disclosed technology and shall not be considered limiting of the breadth, scope, or applicability thereof. It should be noted that for clarity and ease of illustration these drawings are not necessarily made to scale. 
     The schematic concept of the present invention is shown in  FIG. 1 . The combination of harvesting solar energy  11  and wind energy  12  with present parabolic mirror reflector  10  and wind turbine  20  with the necessary elements are shown in  FIG. 1 . Solar energy  11  is collected by a parabolic mirror reflector  10 , which has an optical means  39  to concentrate visible spectrum light  13  and reflect the rest of the spectrum light e.g. infrared energy  14 . The reflected infrared energy is captured by a receptor e.g. heat receiver  50  in the back portion of the parabolic mirror reflector  10  to be used to heat cold molten salt  60 . The concentrated visible light  13  is reflected to high concentrated photovoltaic HCPV receiver  40  by an aiming mirror  30 . The diffused light collect by the thin film solar cells  15  designed at the back portion of the parabolic mirror reflector  10 . The electricity produces from the cheat solar cells used for tracking control system  17  and the DC heater  16  to heat up the molten salt in the molten salt storage system  60 . 
     Again as shown in  FIG. 1 , a water cooling system  71  for heat removal for wind turbine  20  and HCPV receiver on wind tower  40  are combined in the present invention to decrease the cost for having two separate cooling systems for the HCPV receivers and wind turbine. 
     Again as shown in  FIG. 1 , the infrared energy  14 , captured by a heat receiver  50  installed in the solar dish collector  10  provides the necessary energy to heat a molten salt reservoir  60 . To increase the efficiency, a storage tanks is used to store the molten salts  60  for indirect heat exchanger system  65 . The molten salt  60  storage tank offers an inexpensive means of storing solar energy in comparison to other storage media, such as batteries. In addition, the molten salt  60  has a higher lifetime and efficiency compared to batteries. 
     As shown in  FIG. 1 , the molten salt  60  can be used to provide heat for heat exchanger system  65  to generate high pressure steam  70  for steam turbine generator  72  to produce electricity. The used steam in the proposed system will return to the condenser  73  and to the wind tower water cooling system  71 . 
     By combining the solar energy  11  and wind energy  12  in the present embodiment, the components, such as DC to AC inverter  82 , step up transformers  84 , for transferring electricity to the substation  89  and the grid  90 , can be used for both systems to decrease the cost. 
     One embodiment of a solar dish collector  10  of the present invention is shown in  FIGS. 2-3 . The solar dish collector  10  comprises of a parabolic surface  102 , a plurality of support bracing  103 - 106  to hold an optical means  39  and also pivotally attach to an aiming mirror  30 . The solar dish collector further has a support base  110  to support whole structure and the aiming mirror  30 . Again as shown in  FIG. 2 , the parabolic surface  102  comprises of a plurality of mirrors which are attached to the surface  102  to collect and concentrate the sun light. 
     As shown in  FIGS. 2-3 , the front portion of the parabolic surface  102  is covered by a plurality of mirrors. At the back portion of the parabolic surface  102 , a heat receiver  107  locates to absorb heat from the diffused light. The diffused light passes through an opening  140  at the centre of the parabolic surface  102  and hits the heat receiver  107 . The heat receiver  107  is fixed to the back portion of the parabolic surface  102 . 
     Two flexible ducts carry a molten salt to the heat receiver  107  and to the two fixed ducts at the bottom portion of the solar dish collector. The fixed ducts are responsible for carrying molten salt in the molten salt storage system. A cheat photovoltaic cell can be replaced at the back portion of the parabolic surface  102  to generate electricity. The electricity which produced from the thin film solar cell can be used for a DC heater to heat the molten salt and also provide electricity for the tracking system. 
     The heat absorbs by heat receiver  107  is collected by a molten salt circulation system, which is installed at the back portion of the dish  10 . As shown in  FIGS. 2-3 , a piping system  61 - 62  circulates the molten salt in the proposed system, as an indirect heat exchanger system. The fixed ducts  61 - 62  are located at the bottom portion of the solar dish collector  10 , two flexible ducts connect to the fixed ducts  61 - 62  and the heat receiver  107 . Flexible ducts are used in the proposed system, because the solar dish collector is moving and tracking the sun light during a day time. 
     Again as shown in  FIGS. 2-3 , during a day, the solar dish collector  10  traces the sun movement. For tracking sun movement, the solar dish collector  10  moves by the support bracings  103 - 106  over a railing system  200  at the back portion. The railing system  200  supports the dish in a specific position, the movement of the solar dish collector  10  over the railing system  200  drives by a mechanical motor (not shown). The railing system supports by a plurality of pillars  201 - 202  over the ground  400 . For the horizontal movement, a circular rail  300  is used, the circular rail provides the horizontal movement for the whole structure, the circular railing rotates around the bearing point  301 . The solar dish collector  10  and the aiming mirror  30  rotate over the bearing point  301 . The solar dish collector  10  also rotates over a pivot point  111  which is located at a distal end of the aiming mirror  30 . 
     At least one light direction sensor  130  is installed in the parabolic surface  102  to detect sun light direction and move the solar dish collector  10  with bearing system  120  and the support bracing systems  103 - 106  over the pivot point  111 . The solar dish collector  10  is designed to follow the sun, and its direction is changed to collect the sun light when the light direction is changed. 
     A control system  100  controls the light direction sensor  130 , the bearing system  120  and the movement of support bracing system  103 - 106  over the pivot point  111  and the railing system  200 . The purpose of the control system  100  is to track the sun light during a day time to make sure the visible spectrum light reflects to the wind tower. 
     As shown in  FIGS. 2, 6A and 6B , the aiming mirror  30  has a bearing system  120 . The bearing system  120  is designed at a distal end of the support base  110 . The bearing system  120  rotates the aiming mirror  30  by the rotation of the solar dish collector  10 . When the solar dish collector  10  rotates over the circular railing  300 , the aiming mirror  30  also rotates by the bearing system  120 . 
     The optical means  39  of the present invention is shown in  FIGS. 4A, 4B and 4C . The optical means  39  is designed to concentrate the visible spectrum light and reflect the rest of the spectrum (Infrared). The optical means  39  comprises of a plurality of lenses  391 - 392 . Any combination of concave lenses and convex lenses is possible to concentrate some portion of sun light and reflect the inferred. In the  FIG. 4B , one example for the present invention is shown. The optical means  39  which is connected to the support bracing and the pivot point on the light reflector is located in the focal point in all time to concentrate and reflect the sun light. 
     The aiming mirror  30  of the present invention is shown in  FIGS. 5A, 5B, 6A, 6B, 7A, 7B and 7C . The aiming mirror  30  comprises of a reflector-body  31  and a reflecting mirror  32 . The first reflecting mirror  32  has a moving means  23 - 26  to move a distal end  35  of the first reflecting mirror  32  on a horizontal surface  37  and a proximal end  36  on a vertical surface  38 . The moving means for the first reflecting mirror  32  have a plurality of rollers  23 - 26  on the edges. When the distal end  35  of the first reflecting mirror  32  moves back on the horizontal surface  37 , the proximal end  36  moves up on the vertical surface  38 . The reflector-body  31  has an L-shaped opening  115  in a distal end near the first reflecting mirror  32 . The first reflecting mirror  32  stretches over the opening  115 . 
     The control system  100  of the present invention controls the movement of the rollers  23 - 26  for the first reflecting mirror  32  and the dish movement to make sure that the sun light is efficiently captured and reflected to the wind tower. 
     Again as shown in  FIGS. 7A, 7B and 7C , the location of the optical means  39  is fixed by the movement of the parabolic surface  102 . The first reflecting mirror  32  moves by the rotation of the parabolic surface  102 . The rollers  23 - 26  help the first reflecting mirror  32  to stretch. The control system  100  controls the movement of the first reflecting mirror  32  and the parabolic surface  102 . The control system makes sure the reflecting light will pass through the second reflecting mirror installed at the top portion of the support base  110 . 
       FIGS. 8 and 9  show a wind turbine  20 , which has a plurality of HCPV receivers  40 . The HCPV  40  has multi-junction solar cells that absorb the sun light and produce electricity. The cooling system for the wind turbine  20  and the HCPV receivers  40  are combined to achieve economical solution for both systems. The HCPV receivers  40  are installed on the tower body  21  along its lengths. 
     Again as shown in  FIG. 9 , a plurality of solar dish collectors  10  is arranged in circular arrangement to harvest the sun light and reflect it to the wind tower  21 . Each HCPV receiver  40  is assigned for one dollar dish collector  10 . The combination of solar energy and wind energy of the present invention can be applied in new power plants or existing wind farms or solar farms to decrease the cost of installing common equipment for both systems. 
     The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention. 
     With respect to the above description, it is to be realized that the optimum relationships for the parts of the invention in regard to size, shape, form, materials, function and manner of operation, assembly and use are deemed readily apparent and obvious to those skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention.