Patents
Batteryless solar power system App/icu1zt/llzuentor; Miguel A. Timm (USA)
This invention provides a photovoltaic energy
system rhar accumularcs mechanical energy (e.g.
pneumatic or hydraulic pressure) or performs
mechanical work (e.g. pumping water), withour
using electrochemical barrerics.
The system includes one or more PV panels,
OIlC or more high capacitance electrical
capacitors, an clecrrical motor and an electric/
electronic control circuit. In essence, the system
rakes the energy produced by the PV modules
and accumulates ir in the capacitors.
Once enough energy is accumulated to run
the motor, the controller circuit activates the
motor. As the motor consumption is larger than
the power produced by the PV module, it takes
current from the charged capacitors and the
voltage in the capacitors quickly decreases. Once
the volragr reaches a minimum where the
operation of the motor is no longer practical, the
control circuit stops the motor to let the PV
modules techargc the capacitors, and the cycle is
then repeated.
What the above arrangement doe5 is to take
the small amount of power generated by a PV
module and concentrate it in an electrical
capacitor. The accumulated energy is then L&
to produce a burst of power to run an electrical
motor, which in turn performs the desired
mechanical work such as compressing air,
pumping hydraulic pressure or pumping water.
Pamit turmhr~r US 6367259
I’zrblic&on ~<JNIY: April 9. 2002
Organic photosensitive optoelectronic devices with
transparent electrodes Applicant: Princeton University, USA
An organic. photosensitive optoelectronic device
optimised to enhance desired characteristics such
as external quantum efficiency is described. The
photosensitive optoelectronic device has at least
two transparent electrodes and one or more
organic photoconductive layers, disposed
between the transparent electrodes.
In other embodiments. photosensitive
optoelectronic devices with multilayer phoro-
conductive structures and photosensitive
optoelectronic dcvicr, with a reflective layer are
disclosed. Oproelcctronic devices rely on the
oprical and electronic properties of materials to
either produce, or detect, electromagnetic
radiation clcctronically, or to generate
electricity from ambient elecrromagnetic
radiation. Photo-sensitive optoelectronic
devices convert electromagnetic radiation into
electricity.
Solar photovoltaic cells are specifically used to
generate electrical power. PV devices are used to
drive power consuming loads to provide, for
example, lighting, heating, or to operate elect-
ronic equipment such as computers or remote
moniroring or communications equipment.
These power generation applications also
often involve the charging of batteries or other
energy storage devices. so that equipment
operation may continue when direct
illumination from the sun or other ambient light
sources is not available. The term ‘resistive load
refers to any power consuming or storing device,
equipment or system. Another type of
photosensitive optoelectronic device is a
photoconductor cell. In this function, signal
detection circuitry monitors the resistance of the
device to detect changes due to the absorption of
light.
Another type of photosensitive optoelectronic
d evice is a photodetector. In operation a
photodetector has a voltage applied. and a
current detecting circuit measures the current
generated when the photodetector is exposed to
electromagnetic radiation.
A detecting circuit as described is capable of
providing a bias voltage to a photodetector and
measuring the electronic response of the
photodetector to ambient electromagnetic
radiation.
These three classes of photosensitive
optoelectronic devices may be character&d
according to whether a rectifying junction is
present, and also according to whether the device
is operated with an external applied voltage, also
known as a bias or bias voltage.
A photoconducror cell does not have a
rectifying junction, ‘md is normally operated
with a hias. A PV device has at least one
rectifying junction, and is operated with no bias.
A photodetector has at least one rectifying
junction, and is usually but not always operated
with a bias.
Traditionally, photosensitive optoelectronic
devices have been constructed of a number of
inorganic semiconductors, P.R. crystalline,
polycrystalline and amorphous silicon, gallium
arsenide, cadmium t&ride and others.
The term ‘semiconductor’ denores materials
which c.In conducr electricity when charge
carriers are induced by thermal or
electromagnetic excitarion.
The rerm ‘phoroconductive’ relates to the
process in which clectromagneric radiant energy
is absorbed and converred to eacitarion energy of
electric charge carriers, so that the carriers can
conduct (i.e. transporr) electric charge in a
material.
The terms ‘photoconductor’ and ‘photocon-
ductive material’ are used to refer to
semiconductor materials chosen for their
property of absorbing electromagnetic
radiation of selected spectral energies to
generate electric charge carriers.
Solar cells are charactcri&cd by the efficiency
with which they can convert incident sol,lr
power to useful electric power. IIeviccx urilising
crystalline or amorphous silicon dominare
commercial applications. xd some have
achieved efficiencies of 23’31 or greater.
However, efficient crystalline-based devices,
especially of large surface xrca, ate difficult and
expensive to produce due to the problems
inherent in producing large cry&s without
significant efficiency-degrading defects.
0 n the other hand, high effcicncy
amorphous tilicon devices still suffer from
problems with stability.
More recent efforts have focu~d on the ucc of
organic photovoltaic cells to achicvc acceptable
photovoltaic conversion cfficiencics with
economical production costs.
The organic photosensitive devices of this
invention may be incorporated into, inter alia:
light powered radios. Iclcvisiollh, computers.
calculators. telephones and other- wil-class
communications devicrs, watches. emcrgenr!
location devices, electric vchiclcs, ,>OWCI
generation systems and drvices, and cmcrgenc!
power supplies: monitoring and detection
equipment for power and/or hrnaing.
inspection devices. radiation detectors, imaging
devices; md optical coupling dcviccs for
electrical isolation or use in fibrc optic
communications.
Patem wmbw: US 6352377
Publicatio?2 d‘zte: March 5. 2002
hvemovs: Vladimir Rulovic, Srephcn K Forrest
Maximum power tracking solar power system Applicant: The Aerospace Corporation, USA
A maximum power tracker maximises the powc’r
deliverable from a power source, such as a solar
array using increasing, decreasing d
maintaining states, controlled by a set point
signal, modulated by a dither signal for stabilised
regular power tracking during under-drmand
conditions and maximum power tracking during
periods with over-demand conditions of J load.
Multiple converters and respectively maximum
power trackers can be coupled in parallel, using
shared bus contl-ol signal< for fault-tolerant
equalised power convrrsion through the
converters.
Patext number: US 6369462
Publiukon dute: April 9. 2002
/nuextor: Siri Kasemsan
63 Photovoltaics Bulletin May 2002