Solar Cell Efficiency

Multispectrum Photovoltaics have been the buzz for a while now, and most are being designed for solar concatinator arrays (lots of mirrors focusing on a single solar panel or solar panel array). Looks like the latest version is approximately 40% efficient. Progress is progressing progressively. The problem with this is there is very little information being posted by the major manufacturers about efficiency ratings so it's a little tough to make comparisons.

You can also go to this link for a CR4 blog post that deals with the Spectrolab cell.

Good theory perhaps but no dice.

Recommended available to purchase solar cell products is the request. Anyone with firsh hand recommendations for the most efficient solar cell in the real world on the market at a reasonable price.

So you're not asking anything about spectrum absorption, just need a personal shopper? I know it's being worked on but I don't think there are currently any multispectrum cells on the market to the general consumer.

When you start looking into the different manufacturer's claims and spec's, it's amazing how little information about efficiency and spectrum absorption. Good luck in your search, and if you find anything interesting, please post a followup. If anyone else on the site has any more answers, I hope they post them for you. I would suggest looking around at some of the other blogs, as I'm sure there are many that cover a multitude of aspects of PV.

Perhaps I should clarify by specifying the intended use.

Of the present solar cells, which type solar PV cell generates electricity most efficiently 24/7/365 directly facing toward high intensity flames of the various fuels of combustion: corn, soybeans, hay, paper, wood, rice hulls, grass clippings, manure, household garbage, various biomass materials?

Which type solar cell is most efficient facing light or high intensity flames of various colors or color combinations: white, blue, yellow, orange, red, green or the associated light spectrum wave lengths?

Some solar cells generate adequate electricity to power calculators, for example, from the incandescent light bulb inside buildings at night. Which type solar cell is most efficient from low light intensity at the various light spectrums or wave lengths?

It appears the manufacturers collected lazy data only from full sun at noon with no regard for specific light sources, light intensities, light wave lengths, color spectrums and perhaps total disregard for power output as related to ambient temperature, humidity, altitude or pressure, light intensity, wave length, or heat transfer from background radiation, conduction, and convection.

I hadn't ever even considered using a solar cell to gather low level light emitted from flames. Now it's an interesting concept. I don't think it would be as efficient as containing the combustion and capturing the thermal properties with steam or something of that nature.

What is the actual application? Is it a fixed location. What kind of containment and pollution control is in effect?

When traces of alkali elements are present in the burnt gases of hydrogen + oxygen + nitrogen mixtures, a weak continuous emission, extending from the red into the near ultra-violet (ca. 3000 angstrom), is observed, in addition to some atomic lines of the alkalies. This continuum has been examined as a function of the nature and concentration of the additive, and of the temperature and composition of the flame gases. The observed small variation of the intensity of the continuum with temperature and the correlation of the intensity with the concentration of hydroxyl in the gases have led to the conclusion that the origin of the continuum lies in a radiative process A + OH → AOH + hν , where A represents an atom of alkali element. The results are not consistent with the previously held views that the continuum arises from a radiative recombination of oppositely charged particles. The possible use of the intensity of the continuum as a measure of concentration of hydroxyl is discussed.

The preferred embodiment of the invention is also designed specifically to
discriminate between a small hydrogen flame and the large flare stack
flame that is constantly burning during Space Shuttle fueling. For this
reason, the DSP also computes the frequency spectrum of the flickering in
each of the detected signals by using a Fast Fourier Transform (FFT)
frequency spectrum analysis of one of the detector signals which
determines if the flicker frequency is relatively high and thus indicative
of a small flame, or is relatively low and thus indicative of a large
flame, such as the flare stack flame. This analysis can be employed with
the cross-correlation analysis to insure further that the flame detector
does not respond to either reflections or direct radiation from the flare
stack flame. Thus, if the cross-correlation of any of the three pairs of
signals exceeds the threshold, and the analysis of the flickering
indicates that the source of radiation is a small flame, the DSP generates
an alarm indication which can be used to activate any suitable type of
alarm device.
To prevent the flickering analysis from inhibiting generation of an alarm
signal when signals from both a small flame and a large flame are
received, the algorithm can also perform a high pass filtering of the FFT
frequency spectrum if the flicker analysis indicates the presence of
reflections from a large flame. The high pass filtering removes the lower
frequency large flame components from the frequency spectrum, thus leaving
only high frequency components. If enough high frequency components are
present to confirm the presence of a small flame, an alarm condition will
also be asserted by the DSP.
In the preferred embodiment, the DSP continually receives and stores signal
data from the detectors hundreds of times a second, and performs the
normalized cross-correlation computation on each set of data. The FFT
frequency spectrum analysis need not be performed as often, and is
preferably performed once every couple of seconds. A sliding time window
approximately 30 seconds in length is created using FIFO data buffers
which preserves the detector data received immediately prior to and after
the generation of an alarm. This arrangement permits post alarm analysis
of the detector data by personnel for various purposes, such as to
determine whether the flame detector is operating correctly.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other features and advantages of the present invention
will become apparent from the following detailed description of a
preferred embodiment thereof, taken in conjunction with the accompanying
drawings in which:
FIG. 1 is a general block diagram illustrating the circuit components
employed in a flame detector comprising the preferred embodiment of the
present invention;
FIG. 2 is a flow chart depicting the main program of an algorithm employed
by the flame detector's digital signal processor to determine whether the
detector has received radiation directly from a small flame; and
FIGS. 3A-3C are first, second and third portions of an interrupt subroutine
that is called by the main program to analyze samples received from the
flame detector's three radiation detectors.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A block diagram of the components of a flame detector 10 constructed in
accordance with the preferred embodiment of the present invention is
illustrated in FIG. 1. The heart of the flame detector 10 is a digital
signal processor 12 (DSP) which processes signals received from first and
second IR detectors 14 and 16, and a single UV detector 18. Preferably,
the DSP 12 is a model number DSP56002FC40 processor, and it processes the
received signals in accordance with an algorithm illustrated in FIGS. 2
and 3A-C, and discussed below.
All three of the detectors 14, 16 and 18 can be of any conventional
construction, and are each responsive to radiation in a narrow band of
wavelengths. The first IR detector 14 is specifically selected to be
responsive to radiation of 1.3 micron wavelength, while the second IR
detector 16 is selected to be responsive to radiation of 2.7 micron
wavelength. The UV detector 18 is selected to be responsive to ultraviolet
radiation of wavelength less than 300 nanometers and preferably in the
range of approximately 180 to 260 nanometers. The wavelength sensitivities
of the three detectors 14, 16 and 18 are specifically chosen so that the
flame detector 10 can discriminate between directly sensed hydrogen flame
radiation, and radiation received either from reflections of a hydrogen
flame, or from multiple nonflame sources. All three of the wavelengths are
present in all hydrogen flames, but are not present together in other
types of radiation, and thus provide a hydrogen flame wavelength
signature. For example, although the sun emits UV radiation, the earth's
atmosphere filters out any UV below 300 nanometer wavelength, and thus,
the UV detector 18 will not respond to UV from the sun. In addition, each
of the detector wavelengths is reflected differently from one another so
that the normalized cross-correlation of the signals received from the
three detectors 14, 16 and 18 will not be high if the signals are
generated by received reflections, but will be high if the signals are
generated in response to a directly sensed flame.