Claims:STATEMENT OF CLAIMS

I claim:

1. An apparatus (300) of hybrid solar energy, comprising:
an at least one thermal panel (302);
an at least one photovoltaic (PV) panel (301);
the at least one PV panel (301) arranged at a predefined height directly above the at least one thermal panel (302); and
the at least one thermal panel (302) arranged longitudinally along north-south direction, sloping at a fixed north-south tilt-angle.

2. The apparatus (300) as claimed in claim 1, wherein the at least one PV panel (301) is approximately the same size as the at least one thermal panel (302) such that the at least one thermal panel (302) occupies the same floor area as the at least one PV panel (301) stacked above in arrangement.

3. The apparatus (300) as claimed in claim 1, wherein the height of the at least one PV panel (301) above the at least one thermal panel (302) is adjustable.

4. The apparatus (300) as claimed in claim 1, comprising a frame (304) to allow mounting of the at least one PV panel (301) at atleast one suitable height from the at least one thermal panel (302).

5. The apparatus (300) as claimed in claim 1, wherein the at least one PV panel (301) is freely rotatable 360 degrees from an orientation perpendicular to solar radiation where the at least one PV panel (301) catches maximum sun to an orientation parallel to the solar radiation where the solar radiation passes through the at least one PV panel (301).

6. The apparatus (300) as claimed in claim 1¸ wherein the at least one PV panel (301) is split longitudinally into a first portion (3011) and a second portion (3012).

7. The apparatus (300) as claimed in claim 6¸ wherein the first portion (3011) and the second portion (3012) are independently rotatable on an axle (303) arranged on the frame (304) at the sufficient height above the at least one thermal panel (302).

8. The apparatus (300) as claimed in claim 6, wherein the first portion (3011) and the second portion (3012) are fully and independently rotatable 360 degrees from an orientation perpendicular to the solar radiation where the a portion (say 3011) catches maximum sun to an orientation parallel to the solar radiation where the solar radiation passes through that portion (i.e. 3011) to the at least one thermal panel (302).

9. The apparatus (300) as claimed in claim 1, comprising a reflecting mirror (305) on back surface of the at least one PV panel (301).

10. The apparatus (300) as claimed in claims 6 and 9, wherein the first portion (3011) and the second portion (3012) rotated appropriately will expose either the at least one PV panel (301) or the reflecting mirror (305) on the back surface of the at least one PV panel (301) to face towards sun.

11. The apparatus (300) as claimed in claim 9, wherein the reflecting mirror (305) can be rotated to face the sun at a carefully and continuously or intermittently controlled angle (reflection-tracking) in order to reflect the solar radiation on to the at least one thermal panel (302) which is useful in the morning and evening when the sun strikes the at least one thermal panel (302) at a steep angle from vertical, thereby resulting in a thermal output reduced by cosine of the angle as compared to mid-day.

12. The apparatus (300) as claimed in claim 9, wherein the reflecting mirror (305) is not facing the sun, but the at least one PV panel (301) is rotated to face the sun to generate power or the at least one PV panel (301) is rotated parallel to the solar radiation to allow the solar radiation to directly fall on to the at least one thermal panel (302) around midday.

13. The apparatus (300) as claimed in claim 9, wherein if the reflecting mirror (305) is metallic then the reflecting mirror (305) can cool the at least one PV panel (301) facing the sun such that efficiency and life span of the at least one PV panel (301) is not decreased due to the higher temperature of the panel.

14. The apparatus (300) as claimed in claim 7, wherein the axle (303) can be a hollow cylindrical pipe with coolant water entering through the bottom end of the axle (303) and exiting through the top end of the axle (303) through rotatable joints such that the water connection is an integral part of the axle (303) and therefore does not interfere with the full and continuous rotation of the at least one PV panel (301).

15. The apparatus (300) as claimed in claim 14, wherein the axle (303) is supplied with coolant water, periodically pumps a spray to clean dust, dirt off the at least one thermal panel (302), the at least one PV panel (301) and the reflecting mirror (305).

16. The apparatus (300) as claimed in claim 14, wherein the idea of water connection through the axle (303) is similarly used with the at least one thermal panel (302) to connect the thermo-siphon structure allowing the at least one thermal panel (302) to rotate for sun tracking without any moving tubes if desired.

17. The apparatus (300) as claimed in claim 1, comprising a temperature sensor on the at least one PV panel (301) such that if the at least one PV panel (301) becomes too hot as sensed by the temperature sensor, then the at least one PV panel (301) is rotated parallel to the sun rays so that that the at least one PV panel (301) stops getting further heated, water is sprayed on one or both sides of the panel to cool it down, or the reflecting mirror (305) backside of the at least one PV panel (301) is rotated to face the sun in order to reflect the solar radiation on to the at least one thermal panel (302).

18. The apparatus (300) as claimed in claim 1, wherein when the at least one PV panel (301) is directly sun-facing, then the at least one PV panel (301) will block the solar radiation from falling on the at least one thermal panel (302) around mid-day, but at other times of the day this blockage will not happen due to east-west slant of the sun and due to the large height of the at least one PV panel (301) above the at least one thermal panel (302) thus allowing both the at least one thermal panel (302) and the at least one PV panel (301) to receive the solar radiation and operate simultaneously.

19. The apparatus (300) as claimed in claim 1, wherein when one split-side of the at least one PV panel (301) is parallel to the sun’s rays then the solar radiation falls on to the at least one thermal panel (302) below while the other split-side of the at least one PV panel (301) faces the sun to produce electricity simultaneously.

Dated: 20th day of May 2019 Signature:
Name: Arun Kishore Narasani
Patent Agent: INPA 1049

, Description:FIELD OF INVENTION
[0001] The present disclosure relates to a hybrid space saving photovoltaic thermal panel such that the split-PV type hybrid panel allows the same panel area of typical dimension around 8’X4’ for residential use to be smartly used between electricity and heat generation on demand, saving at least 5K INR per year per family, at 3.0 INR/KWh unit.
BACKGROUND OF INVENTION
[0002] Solar electricity and solar hot water generation are both needed badly on a global scale to reduce the current huge carbon imprint from the overwhelming use of non-renewable sources for these. Both are easy to produce but today high costs inhibiting their adoption are the only block and are decreasing. The economic impact of adoption of smart, inexpensive, advanced solar technology is additionally beneficial for the majority of the world’s economically disadvantaged population living in cramped housing. Since the roof-area available for panel installation in low or middle income families is very limited, once a PV panel of typical dimension around 8’X4’, 300W is installed there is no further roof-area available for a pure thermal solar system of a similar dimension especially since the storage tank occupies space too.
[0003] Current thermal panels can provide 200-300 liters of household hot water at 70-80 deg C, operating at almost 90% heat efficiency with cost recovery in just 3 years, and are beginning to be widely used in developing economies. However the thermal panels are currently much more expensive than PV panels for the same panel area, much heavier than PV panels (70 kg versus 20 kg), and cannot simultaneously provide essential home electricity in power cut prone developing economies.
[0004] Photovoltaic thermal (single sided PV/T) hybrid solar systems, based on a metal heat-absorber back-plate with water or air connections, have been described before. While providing the same electricity as standard PV panels of similar area, PV/T panels can only provide 40 deg C water or air. The PV/T panel cannot be operated at 60-80 deg since PV conversion efficiency of around 18 % degrades 0.42 % for every deg C rise in temp. The lukewarm heat from the hybrid’s thermal metal back plate is therefore not useful for tropical household and can only be used for room heating in the cooler climates.
[0005] Rotatable hybrids i.e, PV on one side, thermal on other side, can provide only electricity or heat but not both at same time. This PV/T panel is usually at least 60+20 kg in weight, and rotating this frequently, either to switch from thermal to electric or to track the sun, is a big challenge even though the PV panel by itself is very light.
[0006] Low or middle income families worldwide currently depend exclusively on expensive, non-renewable sources for heat, hot water and electricity, due to lack of awareness and access, large initial cost and large roof area requirement of renewables. Clearly, it will impact the carbon problem greatly if they can obtain both solar electricity and solar hot water in a very limited roof-area typically 8’ X 4’. Once a thermal panel is installed, there is no more roof-area available for a PV panel. There is therefore a need of a combination panel which flexibly accommodates both PV and T intelligently in same area, and this need cuts across higher income brackets too.
[0007] Photovoltaic panels are widely adopted in advanced economies today, but they are known for a 0.42% per deg C efficiency loss on rising temperature and material damage on being exposed to long term high temperature. Recovery of cost from Silicon PV panels takes 10 years but the system is guaranteed for 20 years or more. While they produce power at < 18% efficiency from the 70% of solar radiation up to 1100 nm, they get heated by the remaining incident energy as also by the 30% radiation above 1100 nm, which really heats up the panel to above 50 deg C, thus necessitating some form of cooling.
[0008] Solar thermal panels of two types are widely used in developing economies for water heating, namely (FPC) flat-plate-conductor and (EVT) evacuated vacuum tube. Recovery of cost from thermal panels takes only three years.
[0009] Thermal panels are very heavy at around 70 kg, and their rotation, for the purpose of sun-tracking through the day which increases heat output by almost 60%, is cumbersome additionally due to the fixed water connections to the thermal panel which in series with the insulated storage tank form a water-recirculation thermo-siphon. Therefore the thermal panels are permanently fixed flat at an incline facing south, thereby suffering substantial angular radiation incidence loss and also substantial reflection losses at their coated glass surface when the sun strikes them at a large east-west inclination except during midday. Therefore thermal panels with additional fixed or tracking reflectors that take up extra area have been proposed before and analyzed for reflecting additional radiation from the sun to compensate this loss.
[0010] Bifacial panels that allow sunlight to enter both sides of the silicon PV area are getting known, but are used only for enhancing photovoltaic effect by a maximum of 15%, and their bottom is not exposed to the sun.
[0011] New technology panels made of Perovskite are currently being developed, and they are reported to reach as much as 28% efficiency.
[0012] Sun-tracking is a known idea to increase panel output by upto 60%, with the availability of single axis and of late dual axis trackers, but PV panel tracking, even if technically feasible in home configurations, currently is not available at affordable prices to home users, and it also consumes precious electric power. As mentioned earlier, residential thermal panel tracking is very cumbersome and not practical, and therefore would require a practical reflector to try to reach sun-tracked panel efficiency. As described later in the present disclosure, we provide a practical, compact, and efficient thermal reflector that takes up no area, and works as an integral backside of the sun-tracking PV panel in our hybrid solar panel apparatus, and actually raises the thermal panel efficiency to equal to or higher than sun-tracked efficiency.
[0013] Silicon PV panels can collect solar radiation only up to 1100 nm at efficiency of 17% and the remaining 83% energy and the sun’s radiation above 1100 nm which makes up 30% of sun’s total earth-surface incident energy is not converted into electricity, but just over-heats the silicon, bringing down the efficiency. This scientifically unavoidable situation indicates the need for built-in PV panel cooling in tropical climates. In the present disclosure, we later propose a novel way to inject coolant into a panel through the axle that does not interfere with sun-tracking.
[0014] A standalone thermal blackbody panel with glass insulation can indeed collect 90% of sun’s incident radiation, and it reaches high temperatures. Using a PV panel at 17% efficiency to just electrically heat water on demand to a similar temperature is inefficient. Even with ongoing PV technology improvements, when one needs only heat or hot water at a household level, but not electricity, it is clearly more effective and efficient to have a true thermal panel. However, when large or complex thermal systems are proposed to run steam turbines to generate electricity, the thermodynamic loss in conversion would bring the overall efficiency to around 40% or so, and therefore, when electricity is actually needed on a smaller scale, it makes real sense to employ a PV system. This indicates the need for both thermal and PV systems to be available at a household level, which is the actual subject of the present disclosure. This is especially so in power-cut prone developing economies.
[0015] FIG. 1 is an illustration of existing panel types, according to the existing art.
[0016] Thermal EVT panel (Evacuated Glass Tube) costing around 25K INR (370 US$ installed) is shown in notation (a) of FIG. 1. Thermal FPC panel (Flat Plate Collector with glass insulation) costing around 40K INR (600 US$ installed) is shown in notation (b) of FIG. 1. A PV panel (8’X4’, 300W) costing around 9K INR (140 US$ installed) is shown in notation (c) of FIG. 1.
[0017] FIG. 2 is an illustration of current hybrid PV/T panel, according to the existing art.
[0018] The PV/T panel’s tube heat absorber plate and water tube system is shown in notation (a) of FIG. 2. The PV/T panel’s glass insulation is shown in notation (b) of FIG. 2. Hybrid PV/T collector (200) is shown in notation (c) of FIG. 2. Hybrid PV/T collector (200) includes side insulation (201), glazing cover (202), photo voltaic (203), absorber (204) and back insulation (205). These photo voltaic thermal (PV/T) hybrid panels with a water cooled metal back plate to take away the heat from the silicon face are known but can be rarely used in tropical climates due to the low temperature heat output. Sun exposure still occurs only from one side of the PV/T hybrid panel.
[0019] Thus, it is desired to address the above mentioned disadvantages or other shortcomings or at least provide a useful alternative.
[0020] The present disclosure solves the above problems by a system of space saving hybrid photovoltaic thermal panel.
OBJECT OF INVENTION
[0021] The principal object of the embodiments herein is to provide a system of photovoltaic-thermal hybrid panel in low and middle income houses with very little roof area in developing economies, which makes it possible to smartly reuse the same available panel base area for both solar electricity and solar hot water generation needs, by providing a rotatable PV panel stacked at a sufficient height directly above a fixed thermal panel below, that takes advantage of the east-west inclination or slant of the sun from the vertical in the morning and the evening to allow radiation to reach both panels, and allows the sun to shine on the thermal panel below during midday by an unblocking orientation of the PV panel above.
[0022] Another object of the embodiments herein is to provide a system with a north-south split of the PV panel above, which can simultaneously produce electricity and much more heat for the given area, taking advantage of the north-south inclination or slant of the sun in winter by unblocking the south PV panel and in summer by unblocking the north PV subpanels.
[0023] Another object of the embodiment herein is to provide a system also consisting of a polished metal reflector integrated into the backside to the PV panel, that allows rotating the PV panel quickly by an appropriate angle closer to 180 degrees from a position where the PV panel faces and tracks the sun to a position where the backside mirror faces and tracks the sun, in order to reflect additional solar radiation on the thermal panel below to increase the overall thermal output, thus compensating the decreased energy output of the thermal panel due to the east-west slant of the sun during morning and evening, as compared to the midday energy output.
SUMMARY OF INVENTION
[0024] The embodiment here discloses a system of space-saving hybrid photovoltaic-thermal panel, consisting of subsystems of thermal panel placed below and PV panels arranged vertically above the thermal panel. The hybrid panel faces longitudinally south in the northern hemisphere, inclined down as usual at a fixed north-to-south tilt-angle (NS-tilt) equal roughly to the latitude of the location, so that the sun strikes the hybrid panel vertically on March 22 and September 22, and strikes 23.5 deg north from panel-vertical on June 22 and 23.5 deg south from panel-vertical on Dec 22. Since cos (23.5) == 0.92, only 8% energy is lost due to this fixed NS-tilt in the worst case, so there is no need to change this when season changes. The heavy thermal panel below can be made to track the sun during the day from east-to-west on a center axle in order to add almost 60% extra heat gathering capacity, but this is cumbersome and energy consuming due to its large weight and also considering that its thermal water tubes will shift and twist.
[0025] The other embodiment discloses a PV panel system of size W X L arranged at a height of around H from the thermal panel below. This PV system is longitudinally split, and is comprised of say two or more independent PV panels placed longitudinally next to each other. The panels have a common axle going along and through their centers. The two PV panels are independently rotatable on this common axle by a respective stepper motor. Each panel can thus independently do full east-west sun-tracking increasing electrical output by 60% or can be put on-demand in a sun-parking position, i.e. least exposure to the sun, so that the sun’s radiation is not blocked by the PV panel and instead falls fully on the thermal panel below, especially around midday.
[0026] The other embodiment discloses a thermal panel system of size around W X L (say 8’ X 4’) at the bottom weighing roughly 70 kg with a typical water circulated thermo-siphon. Typically this can sustain a 250L storage tank, supplying 60-80 deg C hot water. The thermal panel is fixed, but if one wants it to track the sun during the day to obtain 60% more energy, it is proposed that the inlet-tube attaches by a rotating joint to a central hole in the southern end of the axle which rotates inside bearings fixed on the supporting frame and the outlet-tube similarly attaches by a rotating joint at the northern end of the axle. When both the PV panels in hybrid photovoltaic-thermal panel are sun-tracking continuously or intermittently by means of stepper motors, then both PV panels fully receive sun’s radiation, producing full electricity but blocking radiation to the thermal panel around mid-day. If the key clearance height H is large enough, then except from around 11AM-1PM, the sun will anyway shine from east or west onto the thermal panel below regardless of the sun-tracking angle of the above PV Panel. This allows simultaneous production of heat from full thermal panel and electricity from full PV panels. More tracking PV panels can be repeated at further height clearances to generate more electricity. If the sensed PV panel temperature rises for any reason, it can sun-parked allowing the thermal panel below to produce heat until PV panel cools down. When only one PV panel i.e., the northern one is sun-parked, its side of sun’s radiation falls through to the northern side of the thermal panel, while the sun-tracking southern PV panel produces full electricity. If however both PV panels are sun-parked, then the thermal panel is fully exposed to the sun absorbing and producing full heat during midday. The same stepper motor for tracking the sun is also smartly used to instantly turn panel away from or towards the sun. In the parked position, the PV panel produces much less electricity from the diffused daylight than when the PV panel is directly facing the sun. Instead of PV panel sun-parking or PV panel facing the sun, as is described below, with a metal mirror backside on the PV panel, the system can be rotated using the stepper motor so that the metal mirror can face the sun and reflect additional radiation on to the thermal panel below in the morning or evening in addition, or provide cooling when the PV side is facing the sun.
[0027] The other embodiment discloses a metal polished mirror backside (reverse) to the rotatable PV panel, such that, instead of presenting the PV side to the sun, if the metal mirror backside is instead presented to the sun at an appropriate angle to the sun in the morning and the evening, then when the sun is closer to the horizon, the thermal panel’s decreased effective width W1 presented to the sun can be compensated by the increased effective width W2 presented by the mirror to the sun, thus keeping the total effective width near constant throughout the day, thus obviating the need to rotate the heavy thermal panel to the sun. The energy advantage of the mirror in general depends on H, its reflectivity, and its width W. The net result of using the reflector mirror backside is that, in spite of thermal panel being fixed, we can generate as much heat in the morning or evening as during the mid-day. When our back-reflector-integrated PV panel is facing the sun, it reaches thermal equilibrium with respect to the surroundings, which depends on its specific heat, heat conductivity, reflectivity, surface, humidity, wind, radiation, etc. Our shiny metal reflector integrated PV panel will be at a lower temperature at equilibrium, compared to a simple PV panel.
[0028] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF FIGURES
[0029] The method is illustrated in the accompanying drawings, throughout which like-reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0030] FIG. 1 is an illustration of existing panel types, according to the existing art;
[0031] FIG. 2 is an illustration of current PV/T panel, according to the existing art;
[0032] FIG. 3 is an illustration of hybrid photovoltaic (PV)- thermal (T) panel, according to the embodiments as disclosed herein;
[0033] FIG. 4 is an illustration of longitudinal view for hybrid PV-T panel, according to the embodiments as disclosed herein;
[0034] FIG. 5 is an illustration of PV panel with sun-facing and sun-parking, according to the embodiments as disclosed herein;
[0035] FIG. 6 is an illustration of the metal reflector back on the PV panel reflecting the radiation on to the thermal panel increasing its effective heat output by (W1+W2)/W1 where W1 is larger than W2, according to the embodiments as disclosed herein;
[0036] FIG. 7 is an illustration of the metal reflector back on the PV panel reflecting the radiation on to the thermal panel increasing its effective heat output by (W1+W2)/W1 where W1 is smaller than W2, according to the embodiments as disclosed herein;
[0037] FIG. 8 is an illustration of a segmented finning of the metal mirror to produce an effective concave mirror and to provide better cooling for the PV panel by the fins, according to the embodiments as disclosed herein;
[0038] FIG. 9 is an illustration of northern PV panel in tracking mode at latitude F on December 22, according to the embodiments as disclosed herein;
[0039] FIG. 10 is an illustration of southern PV panel in tracking mode at latitude F on June 22, according to the embodiments as disclosed herein;
[0040] FIG. 11 is an illustration of vertically stacked PV panels, according to the embodiments as disclosed herein;
[0041] FIG. 12 is an illustration of sliding PV panels
view from north, according to the embodiments as disclosed herein;
[0042] FIG. 13 is an illustration of rotating arm in the frame containing one or two rotating panels such that the metal mirror back on the PV panel reflects the radiation on the thermal panel thus increasing effective heat output by (W1+W2)/W1, according to the embodiments as disclosed herein; and
[0043] FIG. 14 is an illustration of the rotating arm in the frame containing one or two rotating panels such that the sun-facing PV panel is producing full power in the afternoon with very little shadowing of the thermal panel, according to the embodiments as disclosed herein.

DETAILED DESCRIPTION OF INVENTION
[0044] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments. The term “or” as used herein, refers to a non-exclusive or, unless otherwise indicated. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein can be practiced and to further enable those skilled in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0045] Referring now to the drawings and more particularly to FIG 3 to FIG. 14, where similar reference characters denote corresponding features consistently throughout the figure, there are shown preferred embodiments.
[0046] FIG. 3 is an illustration of hybrid photovoltaic (PV)-thermal (T) panel, according to the embodiments as disclosed herein.
[0047] In an embodiment in FIG. 3, the apparatus (300) of hybrid photovoltaic-thermal panel consists of a W’ X L’ thermal panel (302) placed at the bottom i.e., longitudinally facing and inclining to south in north hemisphere as usual at a fixed north-south tilt-angle (NS-tilt) roughly equal to the latitude of the location, so that the sun strikes the panel vertically on March 22 and September 22, and strikes 23.5 deg north from panel-vertical on June 22 and 23.5 deg south from panel-vertical on Dec 22 during mid-day. Since cosine (23.5) == 0.92, only 9% energy is lost due to this fixed NS-tilt in the worst case, so there is in principle no need to change this tilt when season changes. However it is common practice, depending on different seasonal preferences like more emphasis on hot water in winter, that the panel can tilt south at an angle larger than the latitude. While the large W’ X L’ thermal panel (302) which is very heavy due to the metal plates, tubes, water, etc. can, in theory, be made to track the sun during the day from east-to-west on a north-south center axle adding almost 60% extra heat gathering capacity, this tracking is very energy consuming and also cumbersome considering that its thermal water tubes will shift and twist. So in general, the heavy W’ X L’ thermal panel (302) is basically fixed permanently facing vertically and does not rotate. So the W’ X L’ thermal panel (302) is fixed, but is provided with a light-weight metallic reflecting mirror (305) as the backplane of a rotary sun-tracking W’ X L’ PV panel (301) above to reflect additional heat onto the W’ X L’ thermal panel (302).
[0048] In an embodiment in FIG. 3, the apparatus (300) of hybrid photovoltaic-thermal panel further consists of the W’ X L’ PV panel (301) that is arranged at a height of H directly above the W’ X L’ thermal panel (302) such that the W’ X L’ PV panel (301) is split longitudinally into a W’ X L’/2 first portion (3011) at the south and a W’ X L’/2 second portion (3012) at the north which are rotating independently and longitudinally next to each other on a common north-south PV panel rotation axle (303). The stepper motors are algorithmically controlled such that the W’ X L’/2 first portion (3011) and the W’ X L’/2 second portion (3012) can independently do continuous or intermittent east-west sun-tracking increasing the PV output by 60% or one or both can be placed on-demand in a sun-parking position i.e. least exposure to the sun, parallel to the radiation so that the sun’s radiation falls fully on to the W’ X L’ thermal panel (302) below as needed, or one or both can be flipped to point the metallic reflecting mirror (305) backside at the sun at a precisely controlled angle to reflect maximum additional radiation on the W’ X L’ thermal panel (302) below. The W’ X L’ PV panel (301) on top is approximately of the same size as the W’ X L’ thermal panel (302) at the bottom. The reason is that the same floor area that is occupied by the W’ X L’ thermal panel (302) at the bottom is now sufficient for the multiple PV panels, if they are stacked in the said arrangement. This stacking of multiple PV panels on the same ground area is made possible by the frame (304), which sits on the northern and southern side of the panel arrangement. The height adjustability of the frame (304) on both the north or south serves multiple uses for example, the higher the W’ X L’ PV panel (301) is, then, except during mid-day when the sun is directly overhead, the east or west slanted sun can more easily illuminate both the panels, for another example, the southern side of the frame can be adjusted higher than the northern side in summer since then the sun is more northerly, or similarly the northern side can be higher in winter, thereby avoiding the 9% loss in PV production. The separation height H of stacking is at least half the width W of the W’ X L’ PV panel (301) to allow full rotation of the above W’ X L’ PV panel (301) about its north-south axis without touching the other panels. The height H can be larger to allow the slanting sun to more easily reach both panels except during mid day, the reason it cannot be too large is that then the reflecting mirror (305) reflection of heat will then not fully fall on the W’ X L’ thermal panel (302) below.
[0049] In an embodiment in FIG. 3, the apparatus (300) of hybrid photovoltaic-thermal panel is provided with frame (304) for supporting the W’ X L’ PV panel (301) and the W’ X L’ thermal panel (302). The W’ X L’ thermal panel (302) is typically provided with low-reflectivity glass plating (306), air insulation (307), copper pipes (308) fixed on metal blackbody thermal absorber plate (309) and insulation (310).
[0050] FIG. 4 is an illustration of longitudinal view for hybrid PV-T panel, according to the embodiments as disclosed herein.
[0051] In an embodiment in FIG. 4, longitudinal view
for hybrid PV-T panel from north direction is shown, to illustrate the PV panel rotation axle (303) to allow sun tracking, and the copper pipes (308) fixed on the metal blackbody thermal absorber plate (309). The stepper motors for the PV panels are not shown, and they are controlled intelligently to enable the various embodiments described herein.
[0052] FIG. 5 is an illustration of PV panel with sun-facing and sun-parking, according to the embodiments as disclosed herein.
[0053] In an embodiment in FIG. 5, during morning the W’ X L’ PV panel (301) is sun parked and the W’ X L’ thermal panel (302) gets full sun. During evening the W’ X L’ PV panel (301) is sun-facing and depending on H and sun-angle, the W’ X L’ thermal panel (302) still gets partial sun. When H is sufficiently large compared to W, it is clear that a fully sun-facing W’ X L’ PV panel (301) will not block the sun from reaching the W’ X L’ thermal panel (302) below before a certain time in the morning, and after a certain time in the afternoon which times will be determined by the ratio of H to W assuming the W’ X L’ thermal panel (302) and the W’ X L’ PV panel (301) have the same width and how the W’ X L’ PV panel (301) blocks the sun from reaching the W’ X L’ thermal panel (302) fully.
[0054] FIG. 6 is an illustration of the metal mirror back on the PV panel reflects the radiation on to the thermal panel increasing its effective heat output by (W1+W2)/W1 where W1 is larger than W2, according to the embodiments as disclosed herein.
[0055] In an embodiment in FIG. 6, the metal reflecting mirror (305) back plate on the W’ X L’ PV panel (301) acts as a reflector and also as a cooling mechanism. The metal reflecting mirror (305) back plate on the W’ X L’ PV panel (301), when arranged at an appropriate angle, reflects the radiation on to the W’ X L’ thermal panel (302), increasing the total heat output. Instead of presenting the PV silicon front side (311) to the sun, if the mirror backside is instead presented to the sun at an appropriate angle to the sun in the morning and the evening, then when the sun is closer to the horizon, the W’ X L’ thermal panel (302) decreased effective width W1 presented to the sun can be compensated by the increased effective width W2 presented by the mirror to the sun, thus keeping the total effective width which represents the total heat energy falling on to the W’ X L’ thermal panel (302) nearly constant throughout the day, thus obviating the need to rotate the heavy W’ X L’ thermal panel (302) to face the sun. Thus when needed or demanded, the metal reflecting mirror (305) back-plate on the W’ X L’ PV panel (301) is rotated to reflect thermal radiation on to the W’ X L’ thermal panel (302), increasing its effective heat output by (W1+W2)/W1. The calculations for setting the reflector angle for maximizing this quantity are explained next. For a typical fixed Thermal panel lying flat, without the reflector, the heat energy is proportional to cos(?), where ? is the east-west angle of sun from vertical. But with our reflector backside of the PV panels located at height H and angled correctly at the sun (either continuously or intermittently by the stepper motor), we can calculate the total heat irradiance falling on the thermal panel (from both direct and reflected) as follows. Assuming the reflector axis is located directly above the thermal panel centre (for the purpose of east-west symmetry), we should, for any given time, set the angle of the reflector such that (i) the topmost reflected ray in the image that falls within the thermal panel and the bottommost reflected ray from the bottom tip of the reflector (which will fall inside the thermal panel) should define a maximum sun-normal width W2; (ii) the topmost direct ray from the sun is not blocked by the bottom tip of the reflector; (iii) the sum W1+W2 should be maximized (assuming perfect reflection). While this sum will be significantly larger than W1 for that time, the intent is that this should come close to or exceed the midday W1 (but at the cost of the PV panel not being used). The advantage from the reflector is that, as the sun goes down, W1 will decrease as W. cos(?), but then W2 can be increased by rotating the reflector. Let ß be the to-be-calculated angle of the PV plane from the vertical. Let D be the displacement (from PV rotational centre) and H’ be the height of the PV-top-incidence point of the “highest” reflected ray that still falls inside the thermal panel below. (Note that the PV-bottom-incidence point of the “lowest” reflected ray will be the bottom of the PV panel, and this ray is guaranteed to fall within the thermal panel). Now, let x’ be the x-displacement of this top incidence from the left tip of the thermal panel in the figure, and x’’ be its displacement from the centre of the thermal panel. x’ = H’.tan(? – 2.ß). x’’ = D.sin(ß). H’ = H + D.cos(ß). But, the half-width W/2 = x’+ x’’ = (H + D.cos(ß)).tan(? – 2.ß) + D.sin(ß). Let us call this the “first solution constraint”: Note that, for any given H, ß and ?, the value D can be calculated. Note when ß =0, then W/2 = (H + D).tan(?), but the D value thus calculated may not be the optimum, but this tells us that as H increases for a given ?, positive D decreases, and this decreases the energy. But, the “second solution constraint” is that the bottom reflected ray should not block the direct ray from the sun from reaching the right extreme of the thermal panel: if H’’ is the height of the bottom tip of the PV panel and x’’’ is its displacement from the centre, H’’ = H – W/2.cos(ß), and x’’’ = W/2. sin(ß). To avoid blocking, H’’ >= (W/2 - x’’’).tan(?). That is, H – W/2.cos(ß) >= W/2. cos(ß).tan(?). For a given ß and ?, this will be the case only by keeping H >= W/2. cos(ß)(1+ tan(?)). That is, a larger H allows smaller ß; or given a H, the angle ß should be sufficiently large for the second solution constraint. The instantaneous maximum energy of L.(W.cos(?) + ?.W2) is obtained when the W2 is maximized, where ? is the reflectivity which is a function of various factors. Here, W2 = (W/2 + D).sin(? – ß) which can be numerically solved for various ß, by first finding the D from the first solution constraint, subject to the second solution constraint, and finding the instantaneous best ß and D. Even for practical ?, we will find that effective W. cos(?) + ?.W2 reaches W, which implies that we are able to match the midday production of a thermal panel at any time of the day using our reflector. Our reflector rotates at the centre, in order to be of symmetrical value during both morning and evening, but it is clear that placing the reflector off-centre will slightly increase the heat gathering at the cost of this symmetry. Exact reflector cut-in sun-angle (at which it should start reflecting, which depends on H, W, dust, reflectivity, other parameters, etc., and most importantly a over-riding need for electrical power at that instant) can thus be readily determined numerically, but since the sun-angle is 30 degrees or more from vertical before 10 AM and after 2 PM (cos 30 = 0.866, and cos 25 = 0.906), the theoretical thermal loss due to sun-angle as compared to mid-day exceeds say 10% only before 10:20 AM or after 1:40 PM (in reality however, 10 AM is colder than 2 PM). These are the important periods when the reflector can be effective to cover the >10% loss.
[0056] In an embodiment in FIG. 6, if the metal reflecting mirror (305) is made very slightly concave parabolic and if is located sufficiently above the W’ X L’ thermal panel (302), then it can track and focus the sun on the W’ X L’ thermal panel (302) while presenting a better effective angle than a flat mirror to the sun, thereby increasing the effective width W2 mentioned above or track and focus the sun on a single receiver at a fixed focal-axis such that this receiver can be a thermal axial tube like an evacuated vacuum tube to produce instant high temperature water for the house. Another use of the metal reflecting mirror (305) is to cool the W’ X L’ PV panel (301), since silicon relative efficiency falls quite rapidly with a rise in panel temperature. This metal reflecting mirror (305) back-panel for the PV silicon front side (311) however has to be attached during fabrication of the W’ X L’ PV panel (301) itself for best performance, taking care not to add too much cost or weight to the panel, while noting that it also adds to the physical integrity of the panel during transportation, high wind, etc. It is also possible to add a water-cooling component to the W’ X L’ PV panel (301), the water for which will have to enter by a rotating joint connected to a cylindrical hole in the PV panel rotation axle (303), so as to avoid cumbersome connections and twisting. This water supply can also be used to automatically spray-clean all the panels in order to maintain the efficiencies.
[0057] FIG. 7 is an illustration of the metal mirror back on the PV panel reflects the radiation on to the thermal panel increasing its effective heat output by (W1+W2)/W1 where W1 is smaller than W2, according to the embodiments as disclosed herein;
[0058] In an embodiment in FIG. 7, the metal reflecting mirror (305) back-plate on the W’ X L’ PV panel (301) again acts as a reflector and as a cooling mechanism when the W’ X L’ PV panel (301) faces sun and when more heat is needed, the reflector is rotated to optimally reflect solar radiation on to the W’ X L’ thermal panel (302), increasing its effective heat output by roughly (W1+W2)/W1. As sun goes down, W1 will decrease but down-rotation of the reflecting mirror (305) increases W2. The reflection functionality is the same in morning and evening due to central placement of the support rod. In the early morning and late evening the both PV subpanels can fully face the sun for electricity generation or one half of the W’ X L’ PV panel (301) can be used facing the sun, and the other side of the W’ X L’ PV panel (301) can be used as the metal mirror (305). If H is large, then shadow of the W’ X L’ PV panel (301) on W’ X L’ thermal panel (302) is minimal during midday, but then the angle of reflection will accordingly change to aim the reflection on the thermal panel below.
[0059] FIG. 8 is an illustration of segmented finning of the metal mirror to produce an effective concave mirror and to provide much better cooling for the PV panel by the fins, according to the embodiments as disclosed herein.
[0060] In an embodiment in FIG. 8, segmented finning of the metal reflecting mirror (305) can produce an effective concave mirror and can provide much better cooling for the W’ X L’ PV panel (301).
[0061] FIG. 9 is an illustration of northern PV panel in tracking mode at latitude F on December 22, according to the embodiments as disclosed herein.
[0062] In an embodiment in FIG. 9, exactly one of the W’ X L’ PV panel (301) out of the two is sun-tracking. At a sunny location at a earth latitude of F, due to the height H at which the W’ X L’ PV panel (301) is situated above the W’ X L’ thermal panel (302), the W’ X L’ thermal panel (302) receives sun’s radiation on an area W X (L/2 + H Sin 23.5) instead of W X L/2 on Dec 22 or June 22 when the sun is farthest from the panel’s vertical line. Here W and L are width and length of the panel. This amounts to (2.H.Sin 23.5)/L percent more thermal area and power than the half thermal portion. That is 40% more heat when H=L/2, however since the panel is tilted 23.5 degrees away from the sun, the effective normal area facing the sun is W X (L/2 + H Sin 23.5)*Cos (23.5) which is still 28% more heat when H=L/2 as compared to a W X L/2 thermal panel when directly facing the sun such that the northern PV portion is producing full electric power. A similar argument applies on June 22 when the southern PV panel produces full electric power and the northern PV panel is parked. Clearly if H is even larger than L/2, then the gain during midday is even higher. Note H has to be greater than W/2, so that the W’ X L’ PV panel (301) can rotate without touching the W’ X L’ thermal panel (302).
[0063] In an embodiment in FIG. 9, except energy loss due to partial shadowing of bottom panel during midday, the rotational apparatus provides a 100% additional tracked panel area except roughly during midday in the same floor area, with no need for any complex calculations for small gains. That is, except during midday, both PV subpanels can track and produce full power along with full production from the thermal panel. If the key clearance height H is sufficient, then, except from around 11AM-1PM, the sun will shine fully from east or west onto the W’ X L’ thermal panel (302) below regardless of the sun-tracking angle for the above W’ X L’ PV panel (301). This allows simultaneous full production of heat from the W’ X L’ thermal panel (302) and electricity from the W’ X L’ PV panel (301). The W’ X L’ PV panel (301) can be repeated at further height clearances to generate more electricity, these PV panels are much lighter and easier to rotate, and their costs are rapidly coming down. If the W’ X L’ PV panel (301) temperature rises for any reason as measured by a sensor, it can sun-parked immediately until PV cools down. If more heat is needed in the morning or evening due to the slanting sun, the W’ X L’ PV panel (301) can be flipped to act as smart reflectors.
[0064] FIG. 10 is an illustration of southern PV panel in tracking mode at latitude F on June 22, according to the embodiments as disclosed herein.
[0065] In an embodiment in FIG. 10, clearly when only one portion of the W’ X L’ PV panel (301) is sun-parked, the solar radiation on its side falls through to the W’ X L’ thermal panel (302), while the other portion of the sun-tracking W’ X L’ PV panel (301) produces full electricity. In winter, the southern PV portion can be sun-parked, so that the 23.5 southern slant of the sun allows it to get through to a much larger area of the W’ X L’ thermal panel (302) at midday. In general, this amounts to an area of W x (L/2 + H Sin F) instead of area W x L/2, where W and L are width and length of the panel, and F is the seasonal midday north-south tilt of the sun from the panel vertical (note F is zero on March 22 and September 22 for our setup). This amounts to a (2.H.Sin F)/L relative increase in thermal area and power compared to the W x L/2 thermal portion. That is 40% more heat when H=L/2 on Dec22 when F is 23.5; however since the panel is tilted 23.5 degrees away from the sun on say December 22, the effective normal area facing the sun is W x (L/2 + H Sin 23.5)*Cos (23.5) which is still 28% more heat (when H=L/2) as compared to a W x L/2 thermal panel when directly facing the sun (note the northern W x L/2 PV portion is simultaneously producing full electric power). A similar argument applies on June 22. Clearly if H is even larger than L/2, then the seasonal gain during midday is higher. In general, the effective area under this scenario is W x (L/2 + H Sin F)*Cos (F), and thus the seasonal midday advantage of ((H.Sin 2F)/L) tends to zero as we move towards March 22 or September 22. If we do not need much thermal advantage during summer, but maximum direct (non-split) thermal production during winter, then we can actually select a steeper incline of the hybrid panel, but interestingly this steeper incline actually results in a larger summer advantage. It can be noticed additionally that if the heat reflecting mirror (305) is going to be used in the morning or evening on or around December 22, it is more advantageous to use the southern reflector (instead of parking it during midday), because then the sun which is striking the mirror at 23.5 deg south from vertical would strike the southern reflector but the reflection would fall partially on the northern half of the W’ X L’ thermal panel (302), thereby preventing wastage of the reflection; if the northern reflector were used on December 22, then some of the reflection would fall farther north than the panel system and get wasted, this wastage depending on the angle, H, and W. Similar arguments shows one needs to use the northern reflector (instead of parking it during midday) on June 22.
[0066] FIG. 11 is an illustration of vertically stacked PV panels, according to the embodiments as disclosed herein.
[0067] In an embodiment in FIG. 11, vertical stacking of W’ X L’ PV panel (301) on top of the W’ X L’ thermal panel (302) can be extended to include many more of the W’ X L’ PV panel (301) i.e., two PV panels, each vertically separated from the one below by a certain height separation say H. The advantage of this is that, except a couple of hours during midday, the two PV panels can both be rotated to sun-track and catch two times the radiation of a single W’ X L’ PV panel (301). The metal reflecting mirror (305) back-plate for either or both of the PV panels can help in redirecting by rotating around 180 degrees extra sun’s radiation on the W’ X L’ thermal panel (302). Multiple stacking of the W’ X L’ PV panel (301) can be arranged with gaps of say H to produce multiple times power. The W’ X L’ thermal panel (302) itself can be rotatable to generate 60% more power. However in order to even make this rotation feasible in practice, an alternate construction where the water connection in the tubes goes through a central hole (312) in a thermal panel axle is provided. Rotatable sun tracking W’ X L’ thermal panel (302) has the central hole (312) in the center of the W’ X L’ thermal panel (302) axle at the top and bottom for water connections to storage.
[0068] FIG. 12 is an illustration of sliding PV panels
view from north, according to the embodiments as disclosed herein.
[0069] In an embodiment in FIG. 12, the PV-T hybrid with two non-rotating PV panels that slide east-west. The two PV panels can be non-rotating and horizontal, situated at a height of H above the W’ X L’ thermal panel (302), but which slide on each other to reveal more sun to the W’ X L’ thermal panel (302) when needed. Due to the fixed nature of the W’ X L’ thermal panel (302), when the eastern PV panel slides west in the morning, sun shines on more of the W’ X L’ thermal panel (302), which then produces almost as much heat depending on the sun’s incline and the height H as with its area, while indeed the western PV panel is operating. The sliding PV panel system can be extended northerly in length even further to cover the thermal-water storage tank, this way getting additional area.
[0070] FIG. 13 is an illustration of rotating arm in the frame containing one or two rotating panels such that the metal mirror back on the PV panel reflects the radiation on the thermal panel thus increasing effective heat output by (W1+W2)/W1, according to the embodiments as disclosed herein.
[0071] In an embodiment in FIG. 13, the rotating arm in the frame that holds two rotating PV panels with the rotating arm of width W housing the two rotating panels of width W each. Because of the positioning of the panels at a distance R from the centre of the rotating arm, the frame assembly is weight-balanced at all positions. When rotating frame is vertical and the two panels are vertical in the morning and evening, double the electricity is produced. When rotating frame is horizontal and the two panels are horizontal at noon, double the electricity is produced. In this position, as the sun is close to vertical, one of the panels can be parked other producing full power, letting in full sun on half of the W’ X L’ thermal panel (302). A metal reflecting mirror (305) back added on the W’ X L’ PV panel (301) can act as a heat reflector and as a cooling mechanism. When the back side is turned to the sun at an appropriate angle, the metal reflector reflects the radiation on to the W’ X L’ thermal panel (302), increasing heat output. The metal reflecting mirror (305) back on the W’ X L’ PV panel (301) reflects the radiation on to the W’ X L’ thermal panel (302), thus increasing effective heat output by (W1+W2)/W1, wherein the increase is larger than when one does not use the rotating arm. Also it serves to cool the panel, when it is turned around to produce PV power.
[0072] In an embodiment in FIG. 13, if the W’ X L’ PV panel (301) is not mounted in the centre as before, but instead balanced at a distance of R i.e. roughly W/2 from the center of a rotary arm, then it is possible to exactly bring the bottom tip of the W’ X L’ PV panel (301) near the right tip of the W’ X L’ thermal panel (302) so that such a reflection configuration fully contains the radiation. This setup can be simply rotated to the left side as well, because of the dual rotary structure. This morning to evening flexibility in the reflector configuration is more useful and more effective than the fixed reflectors studied before, which in addition occupy extra area. The metal reflecting mirror (305) can indeed be slightly curved and thereby slightly increase the effective W2. Such a slightly concave mirror can also be put to other uses like feeding a light-slit like a light-pipe, or instantly heating a single blackbody metal water pipe or a single evacuated vacuum tube, albeit placed at a sufficient distance, so as not to make it excessively concave. It can be seen that all descriptions of reflection mechanisms herein can be equally applied when PV panels are not even used.
[0073] FIG. 14 is an illustration of the rotating arm in the frame containing one or two rotating panels such that the sun-facing PV panel is producing full power in the afternoon with very little shadowing of the thermal panel, according to the embodiments as disclosed herein.
[0074] In an embodiment in FIG. 14, rotating frame containing a rotating panel such that the W’ X L’ PV panel (301) while sun-facing except at midday, is producing full PV power, full thermal power and at midday, at least half thermal power is produced. The other counter-balancing PV panel can simply be removed and replaced with a counter-weight, so that shadowing of the W’ X L’ thermal panel (302) does not occur as much.
[0075] It can be seen from the foregoing descriptions and embodiments, that the stacked systems with heat reflection components is equally usable in cool climates and developed economies as well, is usable without a PV portion altogether, and is usable even with other tracking mechanisms such as dual-axis trackers.
[0076] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and, or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.