WO2015006021A1

WO2015006021A1 - Photovoltaic powered door lock

Info

Publication number: WO2015006021A1
Application number: PCT/US2014/042548
Authority: WO
Inventors: Daniel David FRIEL; Alan John MONTELLO; Stuart Marshall SPITZER
Original assignee: Electric Film Llc
Priority date: 2013-07-12
Filing date: 2014-06-16
Publication date: 2015-01-15
Also published as: WO2015006020A1; WO2015006019A2; WO2015006019A3

Abstract

Photovoltaic systems and methods, as well as related components, are disclosed. Such systems and methods can provide good performance under conditions of low light. In general, the disclosure provides photovoltaic systems that can provide a relatively high electrical power output under relatively low light conditions (low Lux), such as on an overcast or foggy day, indoor lighting, and/or artificial lighting (e.g., outdoor nighttime lighting). Generally, such systems can include one or more photovoltaic cells and one or more voltage boosting devices electrically coupled to the photovoltaic cell(s).

Description

PHOTOVOLTAIC POWERED DOOR LOCK

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 1 19(e) to each of U.S.S.N.

61/845,776, filed July 12, 2013, and entitled "Photovoltaic Cells, Systems, Components and Methods," U.S.S.N. 61/931,494, filed January 24, 2014, and entitled "Hybrid Photovoltaic Systems," and U.S.S.N. 61/949,913, filed March 7, 2014, and entitled "Photovoltaic Powered Door Lock." The entire contents of each of these applications is incorporated by reference herein.

FIELD

The disclosure generally relates to photovoltaic systems and methods, as well as related components. Such systems and methods can provide good performance under conditions of low light.

BACKGROUND

Photovoltaic cells convert light to electrical energy.

SUMMARY

In general, the disclosure provides photovoltaic systems that can provide a relatively high electrical power output under relatively low light conditions (low Lux), such as on an overcast or foggy day, indoor lighting, and/or artificial lighting (e.g., outdoor nighttime lighting). Generally, such systems can include one or more photovoltaic cells and one or more voltage boosting devices electrically coupled to the photovoltaic cell(s). The photovoltaic cell(s) and voltage boosting device(s) are electrically coupled to a load, such that the photovoltaic cell(s) and voltage boosting device(s) work together to provide electrical energy to the load so that the load can operate under relatively low light conditions.

Optionally, one or more batteries is electrically coupled between the voltage boosting device(s) and the load so that the photovoltaic cell(s) and voltage boosting device(s) are used to keep the battery(ies) properly charged so that the battery(ies) can provide sufficient electrical energy to operate the load without needing to replace the battery(ies), even under conditions of relatively low light.

The systems disclosed herein provide several significant advantages over systems which have previously been proposed. For example, many environments involve relatively low light conditions. Such environments can include indoor lighting environments. In an environment having relatively low light conditions, a known photovoltaic cell may not produce sufficient electrical power to charge a battery. As a result, in such an environment, a photovoltaic cell cannot effectively charge a battery. In contrast, because the photovoltaic cells disclosed herein provide relatively high electrical power even under relatively low light conditions, the photovoltaic cells disclosed herein succeed where other known photovoltaic cells would fail. This can reduce both cost and environmental impact. In many cases, preexisting systems can be retrofit to include photovoltaic cells and systems in accordance with the present disclosure.

In one general aspect, the disclosure provides a system that includes a subsystem and a battery. The subsystem includes photovoltaic cell. The photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less (e.g., 1500 Lux or less, 1000 Lux or less, 500 Lux or less, 400 Lux or less, 300 Lux or less, 200 Lux or less, 150 Lux or less, 100 Lux or less, 50 Lux or less), the subsystem charges the battery at a rate that is at least equal to a discharge rate of the battery.

In another general aspect, the disclosure provides a system that includes a subsystem that includes a photovoltaic cell. The system also includes a battery having an average battery use capacity loss. The photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less (e.g., 1500 Lux or less, 1000 Lux or less, 500 Lux or less, 400 Lux or less, 300 Lux or less, 200 Lux or less, 150 Lux or less, 100 Lux or less, 50 Lux or less), the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within at least 10 times an average time period between uses of the battery.

In a further general aspect, the disclosure provides a system that includes a subsystem that includes a photovoltaic cell. The system also includes a battery having an average battery use capacity loss. The photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less (e.g., 1500 Lux or less, 1000 Lux or less, 500 Lux or less, 400 Lux or less, 300 Lux or less, 200 Lux or less, 150 Lux or less, 100 Lux or less, 50 Lux or less), the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within five hours.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are described below with the aid of drawings, in which:

Figure 1 depicts a system including a photovoltaic cell; Figure 2A is a front view of a system including a door and an electronic door lock; Figure 2B is a cross-sectional view of the system depicted in Figure 2A;

Figure 3 A is a front view of a system including a door and an electronic door lock and a photovoltaic cell;

Figure 3B is a cross-sectional view of the system depicted in Figure 3A;

Figure 4 depicts a system including a photovoltaic cell;

Figure 5 depicts a system including a photovoltaic cell;

Figure 6 depicts a system including a photovoltaic cell;

Figure 7 depicts a system including multiple photovoltaic cells;

Figure 8 depicts a system including multiple photovoltaic cells;

Figure 9 depicts a system including a photovoltaic cell and multiple batteries;

Figure 10 depicts a system including a photovoltaic cell and multiple loads; and

Figure 1 1 depicts a system including a photovoltaic cell.

DETAILED DESCRIPTION

Figure 1 shows an embodiment of the general arrangement of a system 100 in accordance with the present disclosure. System 100 includes a photovoltaic cell 1 10, a battery 120, a voltage booster 130 electrically coupled to both photovoltaic cell 110 and battery 120, and a load 140. During use, light impinges on photovoltaic cell 110, which converts the light to electrical energy (an electrical current). The electrical energy generated by cell 1 10 enters voltage booster 130, and booster 130 increases the voltage of the electrical energy. The electrical energy is then input into to battery 120 to charge battery 120.

Photovoltaic cell 110 is configured to provide good electrical output (e.g., good electrical current) under conditions of low light. For example, photovoltaic cell 110 may have a construction disclosed in commonly-owned, co-pending U.S. Provisional Application No. 61/845,776, the entire contents of which are incorporated by reference herein. In some embodiments, cell 1 10 is capable of producing, for example, an electrical current of at least one milliAmpere (mA) (e.g., at least 2 mA, at least 3 mA, at least 3.5 mA) at 200 Lux or less. Examples of the electrical current produced by cell 110 at 200 Lux include 1.04 mA, 2.1 mA and 3.6 mA. In certain embodiments, cell 110 is capable of producing, for example, an electrical current of at least 10 mA (e.g., at least 20 mA, at least 30 mA, at least 40 mA) at 2,000 Lux or less. Examples of the electrical current produced by cell 1 10 at 2,000 Lux include 10.44 mA, 20.5 mA and 40.5 mA. Voltage booster 130 is configured to enhance the voltage of the electrical output of photovoltaic cell 110. For example, voltage booster 130 may be selected from the voltage boosters disclosed in commonly-owned, co-pending U.S. Provisional Application No.

61/845,776. In general, voltage boosting device 130 can be any voltage boosting device appropriate to be used with cell 110 so that both the current and voltage input to battery 120 from cell 110/booster 130 is appropriate for battery 120. For example, in some embodiments, the current input is at least 0.05 mA (e.g., at least 0.1 mA) at 200 Lux or less, and at least one mA (e.g., at least 1.2 mA) at 2,000 Lux or less. In some embodiments, the open circuit voltage (V_oc) of the cell is between 0.525 and 0.585 V at 200 Lux. In certain embodiments, the power input is at least 0.2 milliWatts (mW) (e.g., at least 0.26 mW) at 200 Lux or less and at least 3 mW (e.g., at least 3.2 mW) at 2,000 Lux or less. In some embodiments, voltage booster 130 is a Texas Instruments BQ25504 ultra-low power boost converter. Other examples of voltage boosters include the Maxim max 17710, the Linear Technologies LTC3105 and the Fujitsu MB39C831. In certain embodiments, it may be desirable to use a given voltage boosting device when the cell produces a relatively high output current. As noted below, optionally, more than one photovoltaic cell may be electrically connected to voltage booster 130.

In general, battery 120 is a rechargeable battery. Exemplary rechargeable batteries are lithium ion batteries, lithium ion polymer batteries, lithium iron-phosphate batteries, nickel metal hydride batteries, nickel cadmium batteries, lead acid batteries, rechargeable alkaline manganese batteries, as well as other rechargeable battery systems. Such batteries can be in standard sizes (e.g., 4.5 Volt, D, C, AA, AAA, AAAA, A23, 9 Volt, CR2032, LR44, 18650, 26650, prismatic, pouch, 2/3A, 4/3A and 4/5A) or in any non-standard size.

Generally, under low light conditions, cell 1 10 and booster 130 are able to provide good charging of battery 120. For example, under conditions of 2000 Lux or less (e.g., 1500 Lux or less, 1000 Lux or less, 500 Lux or less, 400 Lux or less, 300 Lux or less, 200 Lux or less, 150 Lux or less, 100 Lux or less, 50 Lux or less), cell 110 and booster 130 can charge battery 120 such that the charge rate of battery 120 is greater (e.g., at least 5% greater, at least 10% greater, at least 25% greater, at least 50% greater) than the self-discharge rate of battery 120, and such that cell 1 10 and booster 130 generate enough chemical energy in battery 130 to replenish the capacity of battery 130. As referred to herein, the capacity of a battery is measured according to IEC 61951 standards (-1 for NiCd, -2 for NiMH, IEC-61960 for lithium ion, etc.). As referred to herein, the self discharge rate of a battery is determined by measuring the capacity of the battery using the IEC standard method, storing the battery for seven days at 20°C +/- 5°C, and then re-measuring the capacity of the battery.

For example, for a NiMH battery at an elevated temperature (40°C), the self-discharge rate can be about 5% of the battery's capacity per day. For a AA-size consumer NiMH battery of 2500 mAh capacity, this would require a minimum of 5.2 mA of continuous charge current ((2500 mAh) x (5%) ÷ (24 hours) = 5.2 mA) to maintain the battery at its initially charged state. However, NiMH charge efficiency is not 100% and thus some of the charge current going into the battery cell is converted to heat and not chemical energy. In addition, the output from the photovoltaic cell 110 needs to accommodate losses in booster 130 and also any additional battery charger circuitry. Therefore, the charge current provided by cell 110 and booster 130 under low Lux conditions (e.g., 2000 Lux or less, 1500 Lux or less, 1000 Lux or less, 500 Lux or less, 400 Lux or less, 300 Lux or less, 200 Lux or less, 150 Lux or less, 100 Lux or less, 50 Lux or less) is greater (e.g., at least 5% greater, at least 10% greater, at least 25% greater, at least 50% greater) than 5.2 mA/hr.

In some embodiments, under low Lux conditions (e.g., 2000 Lux or less, 1500 Lux or less, 1000 Lux or less, 500 Lux or less, 400 Lux or less, 300 Lux or less, 200 Lux or less, 150 Lux or less, 100 Lux or less, 50 Lux or less), photovoltaic cell 1 10 and booster 130 can replenish the capacity of battery 120 within an appropriate period of time to compensate for battery capacity that is lost during use of battery 120. The average capacity loss of battery 120 per use of battery 120 is referred to herein as the average battery use capacity loss, and the average time period between uses of battery 120. In certain embodiments, under low Lux conditions (e.g., 2000 Lux or less, 1500 Lux or less, 1000 Lux or less, 500 Lux or less, 400 Lux or less, 300 Lux or less, 200 Lux or less, 150 Lux or less, 100 Lux or less, 50 Lux or less), photovoltaic cell 110 and booster 130 replenish at least 50% (e.g., at least 75%, at least 90%, at least 95%) of the average battery use capacity loss of battery 120 within at most 10 times (e.g., at most five times, at most two times, at most one times, at most 0.5 times) of the average time period between uses of battery 120. For example, in certain embodiments, under low Lux conditions (e.g., 2000 Lux or less, 1500 Lux or less, 1000 Lux or less, 500 Lux or less, 400 Lux or less, 300 Lux or less, 200 Lux or less, 150 Lux or less, 100 Lux or less, 50 Lux or less), photovoltaic cell 110 and booster 130 replenish at least 50% (e.g., at least 75%, at least 90%, at least 95%) of the average battery use capacity loss of battery 120 within at most five hours (e.g., at most two hours, at most one hour, at most 30 minutes).

Different battery types (e.g., with different anode/cathode materials) have similar minimum and maximum charge rates based on similar parameters but the absolute values may differ. As an example, many lithium-ion rechargeable batteries have a low self-discharge and near 100% charge efficiency so that the minimum charge rate of the battery is relatively low. As another example, some rechargeable alkaline manganese (RAM) batteries have relatively low charge and discharge currents to maintain good cycle life.

In general, the output from the photovoltaic cell 1 10 needs to accommodate the current properties listed above, as well as the appropriate losses in booster 130, and in the case of charging a battery, any additional battery charger circuitry. In some embodiments, the battery charger circuitry is included in the booster circuit 130.

In general, load 140 can be any desired load, particularly a load that is used in conditions of low light, such as artificial lighting, including indoor lighting and night time lighting (e.g., fluorescent lighting, incandescent lighting, light emitting diode (LED) lighting, organic light emitting diode (OLED) lighting, halogen lighting, plasma lighting and high intensity discharge lamp (HID) lighting). Exemplary loads include devices used in the healthcare industry, the building and infrastructure industry, consumer electronics, and home, hospitality and building automation. For example, a load may be at least one of the following: a healthcare monitoring system (e.g., a wireless healthcare monitoring system); an energy management system; a cooling system; a lighting system; motorized shades;

motorized blinds; sensors (e.g., wireless sensors); a computer peripheral (e.g., keyboard, mouse, monitor, printer, scanner); an electronic paper display; an indoor climate control (e.g., for a smart building); a radiofrequency identification device "REID" (e.g., an active RFID); a transportation device; a logistics device; a handheld device (e.g., a smart phone); a computer (e.g., a laptop computer; a tablet computer); a sensor network (e.g., a wireless sensor network); a smart wearable product; a speaker (e.g., a wireless speaker); a headset (e.g., a wireless headset); headphones (e.g., wireless headphones); a smoke detector; emergency lighting; or a vending machine; an electric toothbrush; an electric razor; and a camera. The componentry of the system can be integrated together to form a single (e.g., monolithic) entity (e.g., the photovoltaic cell, voltage booster and battery are integral with the load), or certain components of the system can be removed from the load. In certain embodiments, the load is the lighting (e.g., LED lighting) for a mirror, such as a vanity mirror. In some embodiments, one or more components can be removable and/or replaceable. As an example, the photovoltaic cell can be replaced or removed, the voltage booster can be replaced or removed, the battery can be replaced or removed, and/or the load can be replaced or removed. In some embodiments, a pre-existing system can be retrofit to include a photovoltaic cell in a system as described herein. As an example, Figures 2A and 2B show a system 200 that includes a hotel door 210 having a hotel door lock 220 that holds a battery pack 230 configured to power lock 220 and so that battery pack 230 is not visible to a hotel guest. For such a system, battery pack 230 is replaced when no longer able to provide sufficient electrical power to run lock 220. The lighting conditions in a hotel hallway are such that the photovoltaic cells and system disclosed herein are appropriate for use. As an example, Figures 3A and 3B show a system 300 which is retrofit to the system in Figures 2A and 2B. System 300 includes a door 310 having a door lock 320 and a battery pack 330. However, the batteries in battery pack 330 are rechargeable batteries that are electrically connected to a photovoltaic cell 340 and a voltage booster 350, which are integrated with door 310.

Optionally, cell 340 can be adhered to door 310 in the form of film strip, which can be designed to provide an aesthetically pleasing appearance. Even under the low light conditions of a hotel hallway, cell 340 and voltage booster 350 can provide sufficient electrical energy to the batteries in pack 330 to recharge the batteries, thereby reducing or eliminating the need to replace the batteries, resulting in reduced cost and reduced environmental impact. Optionally, system 300 can include multiple photovoltaic cells, voltage boosters, and/or loads (see general discussion below). Further, system 300 can also include any additional circuitry relevant to allowing battery pack 330 provide power for the operation of door lock 320. Also, while shown as having wires that electrically couple cell 340 and voltage booster 350 to battery pack 330, optionally such electrical coupling can be achieved in a wireless fashion. While depicted above as a hotel door lock, in certain embodiments, a lock can be any other form of a lock, such as an instutional door lock.

Another exemplary embodiment is shown in Figure 4, which depicts a system 400 including an advertising and/or retail display 410 electrically connected to a battery 420 which is electrically connected to a photovoltaic cell 430 via a voltage booster 440. Display 410 can be any desired display, such as, for example, a liquid crystal display, an e-ink display, an e-paper display, a light emitting diode display or an electro-luminescent display. Combinations of such displays can be used. Display 410 may be used to display, for example, a product, a price of a product, a feature of a product, a sale or any other information that may be of interest to a customer and/or that may attract a customer. The system 400 can be integrated into shelving, partially integrated into shelving, or may be an entirely stand-alone unit. Components of system 400 can be removable and/or replaceable. Optionally, display 410 provides accent lighting for a placard (e.g., a printed placard). In some embodiments, display 410 can be updated (e.g., wirelessly updated). In certain embodiments, system 400 can include a sensor (e.g., a motion detector, a light detector, a proximity detector, a sound detector, or a combination thereof) which can be used to detect, for example, when a customer is nearby so that the sensor can be used to trigger

implementation (e.g., lighting) of display 410. The sensor can be integral with system 400, or may be separate from other components of system 400. In some embodiments, the sensor is wirelessly connected to system 400.

In general, embodiments in which the load relates to advertising or a commercial product, the system may be associated with the traceability of a product. As an example, the load may be a RFID system or some other identification system which is associated with the product, its life cycle (e.g., manufacturing, distribution, use, disposal). Optionally, the load is associated with the point of purchase of the product.

A further exemplary embodiment is shown in Figure 5, which depicts a system 500 including a transmitter 510 which is electrically coupled to a battery 520, which is electrically coupled to a voltage booster 530 which is electrically coupled to a photovoltaic cell 540. Cell 540 and booster 530 can be used to charge battery 520 which powers transmitter 510.

Transmitter 510 can be constructed to send a wireless signal (e.g., a Bluetooth signal). The signal can interact with an electronic device, such as a smart phone, to display a message on the device. As an example, transmitter 510 can send a signal which results in a message on the device corresponding to an advertisement for a product which is for sale in the general area where the device is located. Optionally, system 500 can include a sensor (e.g., a motion detector, a light detector, a proximity detector, a sound detector, a voltage sensor, a current sensor, a power sensor, a resistance sensor, a temperature sensor or a combination thereof) which can be used to detect, for example, when a customer is nearby so that the sensor can be used to trigger implementation (e.g., lighting) of transmitter 510. The sensor can be integral with system 500, or may be separate from other components of system 500. In some embodiments, the sensor is wirelessly connected to system 500. In such a system, if the sensor detects a relatively high level of light (e.g., sun light), the battery 520 can be used to close the shades/blinds, or, if the sensor detects a relatively low level of light (e.g., sun light), the battery 520 can be used to open the shades/blinds.

Figure 6 depicts a system 600 including a photovoltaic cell 610 electrically coupled to a battery 620 via a voltage booster 630. Battery 620 is electrically coupled to a sensor 640. During use, photovoltaic cell 610 and voltage booster 630 maintain appropriate charging of battery 620 so that battery 620 can provide sufficient electrical energy to sensor 640 for sensor 640 to operate. As an example, the sensor 640 can be a light sensor, and a load in the system 600 can be automatic window shades/blinds.

While depicted above as including one photovoltaic cell, a system in accordance with the present disclosure can include multiple photovoltaic cells. As an example, Figure 7 shows a system 700 including multiple photovoltaic cells 710, 712, 714, 716 and 718 electrically coupled to corresponding voltage boosters 730, 732, 734, 736 and 738, which are electrically connected to a battery 720, which is electrically connected to a load 740. As another example, Figure 8 shows a system 800 including multiple photovoltaic cells 810, 812, 814, 816 and 818 electrically coupled to a voltage booster 830, which is electrically connected to a battery 820, which is electrically connected to a load 840. In systems including multiple photovoltaic cells, one or more photovoltaic cells can be electrically connected in series, and/or one or more photovoltaic cells can be electrically connected in parallel.

While depicted above as including one battery, optionally a system in accordance with the present disclosure can include multiple batteries. As an example, Figure 9 shows a system 900 including a photovoltaic cell 910 electrically coupled to a voltage booster 930, which is electrically connected to batteries 920, 922, 924, 926 and 928, which are electrically connected to a load 940.

While depicted as including one load, optionally a system in accordance with the present disclosure can include multiple loads. As an example, Figure 10 shows a system 1000 including a photovoltaic cell 1010 electrically coupled to a voltage booster 1030, which is electrically connected to a battery 1020, which is electrically connected to loads 1040, 1042, 1044, 1046 and 1048.

While depicted in the preceding figures as including a battery, optionally a system in accordance with the present disclosure can be devoid of a battery. As an example, Figure 11 shows a system 1100 including a photovoltaic cell 11 10 electrically coupled to a voltage booster 1 130 which is electrically coupled to a load 1140. In such embodiments, the system may include one or more appropriate electrical components.

Systems disclosed herein also include various combinations of features (e.g., one or more photovoltaic cells, one or more voltage boosters, one or more batteries, one or more loads, certain components electrically connected in series and/or in parallel, no battery).

Although wired electrical connection are discussed above, more generally, an electrical connection can be wireless. Further, electrical connections can be constant or intermittent. Optionally, a system disclosed herein can include more than one type of photovoltaic cell. Such hybrid systems are disclosed, for example, commonly-owned, co-pending U.S. Provisional Application No. 61/845,776, the entire contents of which are incorporated by reference herein.

Examples of artificial light sources include incandescent lights, halogen lights, fluorescent lights, HID lights, LED lights, OLED lights, plasma light, plasma displays, LCDs, LCD displays, computer device displays and mobile phone displays.

While embodiments of systems with one or more batteries have been disclosed, additionally or alternatively systems in accordance with the disclosure can include other energy storage devices, such as, for example, one or more capacitors, one or more supercapacitors, one or more inductors, and/or one or more mechanical energy storage devices (e.g., one or more springs).

In some embodiments, a system can include an energy filter (e.g., to filter voltage, current and/or power). An energy filter can be electrically coupled into a system in series or in parallel with other components of the system. Exemplary energy filters include capacitors, inductors, processors configured to filter energy and circuitry configured to filter energy.

In certain embodiments, more than one system described herein can be electrically coupled in series or in parallel to provide a network. The electrical coupling may be achieved with wires or in a wireless fashion, or a combination thereof.

In some embodiments, a system can be configured so that the photovoltaic cell and voltage booster are used to power (directly or indirectly) an indicator, such as, for example, an on/off indicator and/or a sleep mode indicator. The indicator may be associated with, for example, a computer, a television, a smart phone, a monitor, a keyboard, an audio device, and/or an answering machine. In certain embodiments, the indicator can be associated with an automobile (e.g., on the dashboard). Optionally, the indicator can be associated with a stove burner, an oven, a motion detector, a portable heater, a smoke detector, emergency lighting, a vending machine, an electric toothbrush, an electric razor or a camera.

In some embodiments, the load can be an electrical interference sensor to indicate electrical interference to a device. In embodiments, such devices may include electronic measuring devices (e.g. volt/current meters), radios, computers, monitors, printers, faxes, televisions, automobile electronic ignition systems, computer networks (e.g. wired, wireless, or microwave), digital clocks, electronic control systems, or other devices that may be sensitive to external power interference. EXAMPLES

A series of different types of photovoltaic cells were tested to determine their power production under different Lux. Each sample photovoltaic cell was tested as follows. A light source appropriate for the application (e.g. light emitting diode light source, incandescent light source, fluorescent light source, halogen light source) was turned on, and the light was passed through a filter to the sample cell. A light meter was used to get the highest reading on the left side, middle, and right side of the photovoltaic cell sample. These values were averaged to provide the average Lux reading for the photovoltaic cell sample. The open circuit voltage (Voc) was measured. The photovoltaic cell was shorted to measure the short circuit current (Lc).

The results are presented in Table 1.

Table 1

a This column of crystalline silicon data is based on an average of six cells.

b This is an interpolated value.

c These data are from only one sample.

Other embodiments are covered by the claims.

Claims

CLAIMS What is claimed is:

1. A system, comprising:

a subsystem which comprises a photovoltaic cell; and

a battery,

wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem charges the battery at a rate that is at least equal to a discharge rate of the battery.

2. The system of claim 1, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 1,500 Lux or less, the subsystem charges the battery at a rate that is at least equal to the discharge rate of the battery.

3. The system of claim 1, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 1,000 Lux or less, the subsystem charges the battery at a rate that is at least equal to the discharge rate of the battery.

4. The system of claim 1, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 500 Lux or less, the subsystem charges the battery at a rate that is at least equal to the discharge rate of the battery.

5. The system of claim 1, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 400 Lux or less, the subsystem charges the battery at a rate that is at least equal to the discharge rate of the battery.

6. The system of claim 1, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 300 Lux or less, the subsystem charges the battery at a rate that is at least equal to the discharge rate of the battery.

7. The system of claim 1, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 200 Lux or less, the subsystem charges the battery at a rate that is at least equal to the discharge rate of the battery.

8. The system according to any of claims 1-7, wherein the subsystem charges the battery at a rate that is at least equal 5% greater than the discharge rate of the battery.

9. The system according to any of claims 1-7, wherein the subsystem charges the battery at a rate that is at least equal 10% greater than the discharge rate of the battery.

10. The system according to any of claims 1-7, wherein the subsystem charges the battery at a rate that is at least equal 25% greater than the discharge rate of the battery.

11. The system according to any of claims 1-7, wherein the subsystem charges the battery at a rate that is at least equal 50% greater than the discharge rate of the battery.

12. The system of claim 1, wherein the subsystem further comprises a voltage booster, and the voltage booster is electrically connected between the photovoltaic cell and the battery.

13. The system of claim 1, wherein the photovoltaic cell comprises a dye sensitized photovoltaic cell.

14. The system of claim 1, comprising a plurality of batteries which are electrically coupled to the subsystem.

15. The system of claim 14, wherein, for each at least some of the plurality of batteries, the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem charges the battery at a rate that is at least equal to a discharge rate of the battery.

16. The system of claim 14, wherein, for each of at least some of the plurality of batteries, the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 1,500 Lux or less, the subsystem charges the battery at a rate that is at least equal to the discharge rate of the battery.

17. The system of claim 14, wherein, for each of at least some of the plurality of batteries, the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 1,000 Lux or less, the subsystem charges the battery at a rate that is at least equal to the discharge rate of the battery.

18. The system of claim 14, wherein, for each of at least some of the plurality of batteries, the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 500 Lux or less, the subsystem charges the battery at a rate that is at least equal to the discharge rate of the battery.

19. The system of claim 14, wherein, for each of at least some of the plurality of batteries, the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 400 Lux or less, the subsystem charges the battery at a rate that is at least equal to the discharge rate of the battery.

20. The system of claim 14, wherein, for each of at least some of the plurality of batteries, the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 300 Lux or less, the subsystem charges the battery at a rate that is at least equal to the discharge rate of the battery.

21. The system of claim 14, wherein, for each of at least some of the plurality of batteries, the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 200 Lux or less, the subsystem charges the battery at a rate that is at least equal to the discharge rate of the battery.

22. The system according to any of claims 15-21, wherein, for each of the at least some of the batteries, the subsystem charges the battery at a rate that is at least equal 5% greater than the discharge rate of the battery.

23. The system according to any of claims 15-21, wherein, for each of the at least some of the batteries, the subsystem charges the battery at a rate that is at least equal 10% greater than the discharge rate of the battery.

24. The system according to any of claims 15-21, wherein, for each of the at least some of the batteries, the subsystem charges the battery at a rate that is at least equal 25% greater than the discharge rate of the battery.

25. The system according to any of claims 15-21, wherein, for each of the at least some of the batteries, the subsystem charges the battery at a rate that is at least equal 50% greater than the discharge rate of the battery.

26. The system of any of claims 1-13, further comprising an electronic door lock electrically connected to the battery.

27. The system of claim 26, wherein the battery is configured to power the door lock.

28. The system of claim 26, wherein the photovoltaic cell is configured to be retrofit to a pre-existing unit which comprises the door lock.

29. The system of claim 14, further comprising an electronic door lock electrically connected to the plurality of battereries.

30. The system of claim 29, wherein at least one of the batteries configured to power the door lock.

31. The system of claim 29, wherein the photovoltaic cell is configured to be retrofit to a pre-existing unit which comprises the door lock.

32. The system of any of claims 1-13, further comprising a sensor electrically connected to the battery.

33. The system of claim 32, wherein the battery is configured to power the sensor.

34. The system of any of claims 1-13, further comprising signage electrically connected to the battery.

35. The system of claim 34, wherein the battery is configured to power the sign.

36. The system of any of claims 1-13, further comprising a load electrically coupled to the battery so that the battery powers the load during use of the load.

37. The system of claim 14, further comprising a sensor electrically connected to the plurality of batteries.

38. The system of claim 37, wherein at least one of the batteries is configured to power the sensor.

39. The system of claim 14, further comprising signage electrically connected to the battery.

40. The system of claim 39, wherein at least one of the at least some batteries is configured to power the sign.

41. The system of claim 14, further comprising a load electrically coupled to at least one of the at least some batteries so that the battery powers the load during use of the load.

42. A system, comprising:

a subsystem which comprises a photovoltaic cell; and

a battery having an average battery use capacity loss,

wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within at least 10 times an average time period between uses of the battery.

43. The system of claim 42, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 75% of the average battery use capacity loss of the battery within at least 10 times the average time period between uses of the battery

44. The system of claim 42, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 90% of the average battery use capacity loss of the battery within at least 10 times the average time period between uses of the battery.

45. The system of claim 42, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 95% of the average battery use capacity loss of the battery within at least 10 times the average time period between uses of the battery.

46. The system of claim 42, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within at least five times the average time period between uses of the battery.

47. The system of claim 42, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within at least two times the average time period between uses of the battery.

48. The system of claim 42, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within at least the average time period between uses of the battery.

49. The system of claim 42, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within at least 0.5 times an average time period between uses of the battery.

50 The system of claim 42, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 1,500 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within at least 0.5 times an average time period between uses of the battery.

51. The system of claim 42, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 1,000 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within at least 0.5 times an average time period between uses of the battery.

52. The system of claim 42, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 500 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within at least 0.5 times an average time period between uses of the battery.

53. The system of claim 42, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 400 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within at least 0.5 times an average time period between uses of the battery.

54. The system of claim 42, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 300 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within at least 0.5 times an average time period between uses of the battery.

55. The system of claim 42, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 200 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within at least 0.5 times an average time period between uses of the battery.

56. The system of claim 42, wherein the subsystem further comprises a voltage booster, and the voltage booster is electrically connected between the photovoltaic cell and the battery.

57. The system of claim 42, wherein the photovoltaic cell comprises a dye sensitized photovoltaic cell.

58. The system of claim 42, comprising a plurality of batteries which are electrically coupled to the subsystem.

59. The system according to claim 58, wherein, for each of the plurality of batteries, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within at least 10 times an average time period between uses of the battery.

60. The system according to claim 58, wherein, for at least some of the plurality of batteries, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within at least 10 times an average time period between uses of the battery.

61. The system of any of claims 52-57, further comprising an electronic door lock electrically connected to the battery.

62. The system of claim 61, wherein the battery is configured to power the door lock.

63. The system of claim 61, wherein the photovoltaic cell is configured to be retrofit to a pre-existing unit which comprises the door lock.

64. The system of claim 58, further comprising an electronic door lock electrically connected to the plurality of batteries.

65. The system of claim 64, wherein the plurality of batteries isconfigured to power the door lock.

66. The system of claim 64, wherein the photovoltaic cell is configured to be retrofit to a pre-existing unit which comprises the door lock.

67. The system of any of claims 52-57, further comprising a sensor electrically connected to the battery.

68. The system of claim 67, wherein the battery is configured to power the sensor.

69. The system of any of claims 52-57, further comprising signage electrically connected to the battery.

70. The system of claim 69, wherein the battery is configured to power the sign.

71. The system of any of claims 52-57, further comprising a load electrically coupled to the battery so that the battery powers the load during use of the load.

72. The system of claim 58, further comprising a sensor electrically connected to the plurality of batteries.

73. The system of claim 72, wherein the plurality of batteries is configured to power the sensor.

74. The system of claim 58, further comprising signage electrically connected to the plurality of batteries.

75. The system of claim 74, wherein the plurality of batteries batteries is configured to power the sign.

76. The system of claim 58, further comprising a load electrically coupled to the plurality of batteries so that the plurality of batteries powers the load during use of the load.

77. A system, comprising:

a subsystem which comprises a photovoltaic cell; and

a battery having an average battery use capacity loss,

wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within five hours.

78. The system of claim 77, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 75% of the average battery use capacity loss of the battery five hours.

79. The system of claim 77, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 90% of the average battery use capacity loss of the battery within five hours.

80. The system of claim 77, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 95% of the average battery use capacity loss of the battery within five hours.

81. The system of claim 77, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within two hours.

82. The system of claim 77, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within one hour.

83. The system of claim 77, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within 30 minutes.

84. The system of claim 77, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 1,500 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within five hours.

85. The system of claim 77, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 1,000 Lux or less, the subsystem charges the battery so that at least 50% of the average battery use capacity loss of the battery within five hours.

86. The system of claim 77, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 500 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within five hours.

87. The system of claim 77, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 400 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within five hours.

88. The system of claim 77, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 300 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within five hours.

89. The system of claim 77, wherein the photovoltaic cell and the battery are electrically connected so that, when the photovoltaic cell is exposed to 200 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within five hours.

90. The system of claim 77, wherein the subsystem further comprises a voltage booster, and the voltage booster is electrically connected between the photovoltaic cell and the battery.

91. The system of claim 77, wherein the photovoltaic cell comprises a dye sensitized photovoltaic cell.

92. The system of claim 77, comprising a plurality of batteries which are electrically coupled to the subsystem.

93. The system according to 92, wherein, for each of the plurality of batteries, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within five hours.

94. The system according to 92, wherein, for at least some of the plurality of batteries, when the photovoltaic cell is exposed to 2,000 Lux or less, the subsystem replenishes at least 50% of the average battery use capacity loss of the battery within five hours.

95. The system of any of claims 1-16, further comprising an electronic door lock electrically connected to the battery.

96. The system of claim 95, wherein the battery is configured to power the door lock.

97. The system of claim 95, wherein the photovoltaic cell is configured to be retrofit to a pre-existing unit which comprises the door lock.

98. The system claim 92, further comprising an electronic door lock electrically connected to the plurality of batteries.

99. The system of claim 92, wherein the plurality of batteries is configured to power the door lock.

100. The system of claim 92, wherein the photovoltaic cell is configured to be retrofit to a pre-existing unit which comprises the door lock.

101. The system of any of claims 77-91, further comprising a sensor electrically connected to the battery.

102. The system of claim 101, wherein the battery is configured to power the sensor.

103. The system of any of claims 77-91, further comprising signage electrically connected to the battery.

104. The system of claim 103, wherein the battery is configured to power the sign.

105. The system of any of claims 77-91, further comprising a load electrically coupled to the battery so that the battery powers the load during use of the load.

106. The system of claim 92, further comprising a sensor electrically connected to the plurality of batteries.

107. The system of claim 106, wherein the plurality of batteries is configured to power the sensor.

108. The system of claim 92, further comprising signage electrically connected to the plurality of batteries.

109. The system of claim 108, wherein the plurality of batteries batteries is configured to power the sign.

110. The system claim 92, further comprising a load electrically coupled to the plurality of batteries so that the plurality of batteries powers the load during use of the load.