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