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When used in the heliostat system the triple air layer insulation may not be the technology to use when used below 600°F as there would be less total output power available. Remember the heat loss is proportional to the collector area. In heliostat systems the collector is only a fraction of the area of a flat plate collector. Single air layer insulation may be best below 300°F. No insulation may be needed below 170°F.

cover
Another concern with high temperature operation is the temperature attained by the intermediate glass layers. Since clear glass has a very low thermal emissivity the intermediate glass layers may absorb enough heat to cause melting. The heat loss in the glass, though small in percentage, can cause the glass to become very hot. The fiber glass "Kalwall" type of insulation does not work as it deteriorates at high temperatures and high flux of ultraviolet light. (Recently I have seen some examples of water cooled windows that may fix this problem.) I think this is what you are looking for.

solec
A company that makes selective surface coatings.

* Solec Selective Surface Coatings and Paints.

solchrome
A company that makes selective surface coatings.

* Solchrome Systems India Limited Selective Surface Coatings.

fridge
Architectural Science Lab.

* The Fridge Architectural Science Lab Dr. Andrew Marsh solar absorption and normal emittance for a range of surface finishes.

Wow, this site has disapeared. It was a wonderful resource. To bad its gone but I found some of the info at the WayBack Machine.

* The Fridge At the WayBack Machine internet archive.

Absorptivity & Emissivity table 1 plus others.

	aS	E
	Solar	Surface	aS/E
Material	Absorption	Emissivity	ratio	Comments	Reference
Silver, Highly polished		0.02 - 0.03	3.00		Marks (1)
Gold, Highly polished		0.02 - 0.04	3.00		Marks (1)
Barium Sulfate with Polyvinyl Alcohol	0.06	0.88	.07		The Fridge
Aluminum polished	0.09	0.03	3.00		?
Magnesium Oxide Paint	0.09	0.90	.10		The Fridge
Magnesium/Aluminum Oxide Paint	0.09	0.92	.10		The Fridge
Aluminum quartz over coated	0.11	0.37	.30		?
Aluminum, Highly polished		0.04 - 0.06	3.00		Marks (1)
Snow, Fine particles fresh	0.13	0.82	.16		?
Zinc Orthotitanate with Potassium Silicate	0.13	0.92	.14		The Fridge
Aluminum anodized	0.14	0.84	.17		?
Aluminum foil	0.15	0.05	3.00	Aluminum foil gets very hot because of this high ratio.	?
Potassium Fluorotitanate White Paint	0.15	0.88	.17		The Fridge
Zinc Oxide with Sodium Silicate	0.15	0.92	.16		The Fridge
Paint, White zinc oxide	0.16	0.93	.17		?
GSFC White Paint NS-74	0.17	0.92	.18		The Fridge
Titanium Oxide White Paint with Potassium Silicate	0.17	0.92	.18		The Fridge
Zerlauts Z-93 White Paint	0.17	0.92	.18		The Fridge
Chromium		0.08 - 0.26	3.00		Marks (1)
Dow Corning White Paint DC-007	0.19	0.88	.22		The Fridge
GSFC White Paint NS43-C	0.20	0.92	.22		The Fridge
Titanium Oxide White Paint with Methyl Silicone	0.20	0.90	.22		The Fridge
Zerlauts S-13G White Paint	0.20	0.90	.22		The Fridge
Light colored paints, firebrick, clay, glass	0.04 - 0.40	0.90	.24		U of Miss
Biphenyl-White Solid	0.23	0.86	.27		The Fridge
P764-1A White Paint	0.23	0.92	.25		The Fridge
Zirconium Oxide with650 Glass Resin	0.23	0.88	.26		The Fridge
Solec LO/MIT selective surface paint	0.21 - 0.26	0.15 - 0.19	1.38	LO/MIT I/II products are low emissivity, non thickness dependent coatings.	Solec
Catalac White Paint	0.24	0.90	.27		The Fridge
Hughson White Paint Z-202	0.25	0.87	.29		The Fridge
Hughson White Paint Z-255	0.25	0.89	.28		The Fridge
Hughson White Paint Z-255	0.25	0.89	.28		The Fridge
3M-401 White Paint	0.25	0.91	.27		?
Hughson White Paint A-276	0.26	0.88	.30		The Fridge
Hughson White Paint V-200	0.26	0.89	.29		The Fridge
OSO-H White Paint 63W	0.27	0.83	.33		The Fridge
Opal Glass	0.28	0.87	.32		The Fridge
Sherwin Williams White Paint (A8W11)	0.28	0.87	.32		The Fridge
Mautz White House Paint	0.30	0.90	.33		The Fridge
Snow, Ice granules	0.33	0.89	.37		?
GSFC White Paint NS44-B	0.34	0.91	.18		The Fridge
Sperex White Paint	0.34	0.85	.40		The Fridge
Dupont Lucite Acrylic Lacquer	0.35	0.90	.39		The Fridge
GSFC White Paint NS-37	0.36	0.91	.40		The Fridge
Sherwin Williams F8WJ2030 w Polasol V6V241	0.36	0.87	.41		The Fridge
Sherwin Williams White Paint (F8WJ2030)	0.39	0.82	.48		The Fridge
Tedlar White Paint	0.39	0.87	.45		The Fridge
Hughson White Paint Z-202+1000	0.40	0.87	.46		The Fridge
Aluminum paint (bright)	0.30 - 0.50	0.40 - 0.60	.80		U of Miss
Hughson White Paint A-276+1O36	0.44	0.88	.50		The Fridge
Dull brass, copper, galv. steel, aluminum	0.40 - 0.65	0.20 - 0.30	2.10		U of Miss
Colored paints, brick, light brick,	0.50 - 0.70	0.85 - 0.95	.67		U of Miss
Concrete	0.60	0.88	.68		?
Galvanized metal new	0.65	0.13	5.00		?
Brick, red (Purdue)	0.65	0.93	.68		?
Concrete and stone, dark	0.65 - 0.80	0.85 - 0.95	.81		U of Miss
Galvanized metal weathered	0.80	0.28	2.90		?
Metal, plated Black chrome	0.87	0.09	9.70		?
Anodize Black	0.88	0.88	1.00		The Fridge
Martin Black Velvet Paint	0.91	0.94	.97		The Fridge
Solec Solkote selective surface paint	0.88 - 0.94	0.28 - 0.49	2.36	SOLKOTE HI/SORB-II is an optical coating specifically formulated for solar thermal applications.	Solec
Metal, plated Nickel oxide	0.92	0.08	11.00	This is stainless steel heated until the nickel oxidizes.	?
Metal, plated Black sulfide	0.92	0.10	9.20		?
Pyramil Black on Beryllium Copper	0.92	0.72	1.28		The Fridge
Metal, plated Cobalt oxide	0.93	0.30	3.10		?
Polyethylene Black Plastic	0.94	0.92	1.01		The Fridge
Martin Black Paint N-150-1	0.94	0.94	1.00		The Fridge
Tedlar Black Plastic	0.94	0.90	1.04		The Fridge
Iron and Steel, strongly oxidized		0.95	3.00		Marks (1)
Hughson Black Paint L-300	0.95	0.84	1.13		The Fridge
Paladin Black Lacquer	0.95	0.75	1.27		The Fridge
Black Crystal	0.92 - 0.98	0.08 - 0.25	5.76	Thermafin's Black Crystal Selective Surface Coating (apparently replaced with "Crystal Clear").	Thermafin
Crystal Clear	0.95 - 0.97	0.09 - 0.14	8.35	Thermafin's Crystal Clear Selective Surface Coating.	Thermafin
Carbon Black Paint NS-7	0.96	0.88	1.09		The Fridge
Carbon Black Paint	0.96	0.88	1.09		The Fridge
Chemglaze Black Paint Z3O6	0.96	0.91	1.05		The Fridge
Delrin Black Plastic	0.96	0.87	1.10		The Fridge
GSFC Black Silicate MS-94	0.96	0.89	1.08		The Fridge
GSFC Black Paint 313-1	0.96	0.86	1.12		The Fridge
Hughson Black Paint H322	0.96	0.86	1.12		The Fridge
Velesat Black Plastic	0.96	0.85	1.13		The Fridge
Solchrome	0.94 - 0.98	0.10 - 0.14	8.00	Solchrome Systems India Limited.	Solchrome
Ebanol C Black	0.97	0.73	1.33		The Fridge
Ebanol C Black-384 ESH* UV	0.97	0.75	1.29		The Fridge
3M Black Velvet Paint	0.97	0.91	1.07		The Fridge
Parsons Black Paint	0.98	0.91	1.08		The Fridge
Flat black paint	0.97 - 0.99	0.97 - 0.99	1.00		U of Miss
Paint, Black (Parsons)	0.98	0.98	1.00	I understand this is lamp black mixed with spar varnish.	?
Selective surfaces
Solec LO/MIT selective surface paint	0.21 - 0.26	0.15 - 0.19	1.38	LO/MIT I/II products are low emissivity, non thickness dependent coatings.	Solec
White paint	0.23 - 0.49				U of Miss
Solec SOLKOTE selective surface paint	0.88 - 0.94	0.28 - 0.49	2.36	SOLKOTE HI/SORB-II is an optical coating specifically formulated for solar thermal applications.	Solec
Copper, aluminum, or nickel plate with CuO coating	0.08 - 0.93	0.09 - 0.21	3.37		U of Miss
Black Crystal	0.92 - 0.98	0.08 - 0.25	5.76	Thermafin's Black Crystal Selective Surface Coating (apparently replaced with "Crystal Clear").	Thermafin
Copper treated with NaCIO2 and NaOH	0.87	0.13	6.69		U of Miss
Solchrome	0.94 - 0.98	0.10 - 0.14	8.00	Solchrome Systems India Limited.	Solchrome
Crystal Clear	0.95 - 0.97	0.09 - 0.14	8.35	Thermafin's Crystal Clear Selective Surface Coating.	Thermafin
Metal, plated Black sulfide	0.92	0.10	9.20		?
Metal, plated Black chrome	0.87	0.09	9.70		?
Metal, plated Nickel oxide	0.92	0.08	11.00	This is stainless steel heated until the nickel oxidizes.	?

Links to sites that have Absorptivity or Emissivity data:

thermalconnection
the "Thermal Connections" by K & K Associates
Infrared cameras and night vision equipment.

Sierra Pacific
Infrared cameras and night vision equipment.

Heriot-Watt University, Department of Physics
Black-body radiation, The Planck function.

Reflectivity and Emissivity table 2.

	%	E
		Average
Surface	Reflectivity	Emissivity	Reference
Aluminum foil, bright	92 - 97	0.05	Marks (2)
Reflective Mylar Film	90 - 93	0.05	Nielsen
Aluminum sheet	80 - 95	0.12	Marks (2)
1/8" Plate glass mirrors coated with aluminum on back	85
Aluminum-coated paper, polished	75 - 84	0.20	Marks (2)
Steel, galvanized, bright	70 - 80	0.25	Marks (2)
Rhodium	70 - 80
Stainless Steel	62 - 65
Chromium	60 - 63
Aluminum paint	30 - 70	0.50	Marks (2)
Building materials: wood, paper, glass, masonry, nonmetallic paints	5 - 15	0.90	Marks (2)

reflectometer
Poor Mans Reflectometer.

A useful reflection measurement can be made by comparing the reflection from a sample to a reference surface.
I use 1/8" thick bathroom mirror tiles which have a reflectivity of about 85%. Arranging 2 mirrors the reflectivity is about 72% and 3 mirrors is about 61%.
Another is good quality reflective Mylar, which uses aluminum as the reflective surface at >95%.
A very nice reference light source is the open sky near the zenith, (strait up), on a cloudless day.

Place these side by side and look back through the mirrors at the sky. It is quite easy to compare the brightness. The less reflective surface appears darker than the more reflective one.

The sample doesn't have to be flat, it can be curved as in a concentrator. Or even wrinkled. It doesn't matter as the sky, over a reasonably small area, say 15 degrees, is even in brightness.

 /     / (Tc - Ta)      \ \ 
| 1 - | ---------------- | | * 100 = ST% 
 \     \ (Ts - Ta) * CF / /

ST% = Stasis efficiency of a particular theoretical solar collector system.
Tc  = Collector temperature as measured in a particular collector system.
Ta  = Ambient air temperature around the collector in °F.
Ts  = Stasis temperature. I use (Ts - Ta) of 340°F. You could use 188°C.
CF  = Solar Concentration Factor.

A similar explanation can be had on page 312-317 of:
duffie1
"Solar Engineering of Thermal Processes"
Second edition
Duffie & Beckman
I got mine for about $100us in 1999 at Barnes and Noble:
Get the book here.

[SOLAR] Understanding Performance Equations of Solar Collectors
(A message from David Wells to the Solar Concentration Mailing List.)

Thermomax ( http://209.116.252.72/effi.htm ) gives the efficiency of their collector as:
Efficiency of Collector = 0.84 - 2.02 (Tm-Ta)/G - 0.0046G[(Tm-Ta)/G]**2
Where:
    Tm=Mean working temperature of fluid, Celsius
    Ta=Ambient air temperature
    G=Solar Irradiance in W/m²

This sort of equation is typical of all types of solar thermal collectors. There are some interesting aspects of it worth mentioning.

First, notice that the first term, 0.84, is what you would get for the efficiency if Tm were set equal to Ta. This would be the equivalent of running LOTS of ambient temperature fluid through the collector. In this case, the thermal losses would be equal to zero. Thus, the efficiency of the collector would depend entirely on how transmissive the optics are, and how absorptive the absorber is. For this reason, this test condition measures the "optical efficiency" of the collector.

So, the first term, which is independent of any thermal or irradiance effects, is called the "optical efficiency" of the collector. For the Thermomax collector, the equation says the optical efficiency is 0.84.

Now look at the second term. The second factor is 2.02. This factor multiplies the temperature difference term divided by the solar irradiance term, (Tm-Ta)/G.

So, in my last memo, when I mentioned my "rule of thumb" as being 1/4% reduction in efficiency per degree increase in working temperature, or per PERCENT insolation, it is this second term that is determining this effect (mostly--although the third term has a minor influence, too).

For example: say the solar irradiance is 1000 W/m². The second term becomes 2.02/1000(Ta-Tm). If (Ta-Tm) is 100 °C, then the efficiency is found from the optical efficiency, 0.84, minus this second term, 2.02 x (100/1000), giving about 0.44. The drop in efficiency from the optical efficiency was about 20%, or stated another way, about 0.2% per °C. Close to the "Dave 1/4% rule", right?

Now the third term.

0.0046G[(Tm-Ta)/G]**2 is a small "non-linear" correction term. By "non-linear", we mean that it is a term that accounts for the small amount of bow in the efficiency curve. This bow is due in part to the loss terms which don't go as the first power of the temperature or irradiance. For example, we've seen that the infra red loss goes as the fourth power of the absolute temperature (Stefan-Boltzman law). That's the largest effect which contributes to this term. There are other effects, such as convection effects, all of which are non-linear, and contribute slightly to the bow of the curve (the non-linearity of the curve).

For our example, at solar irradiance of 1000 W/m² and temperature difference of 100 °C, this term becomes:
0.0046 x 1000 x (100)^2 = 0.046. Rounding, this is about 0.05. That's 5% per 100°C, or 0.05 per °C.

So, to get the full "first-order" or linear term, plus "second-order" or non-linear term, you add 0.2 plus 0.05 to get---drum roll, please!--0.25 percent efficiency drop per °C OR per percent insolation drop. That's the origin of the "quarter percent rule of thumb".

-David Wells

This is the minor little correction part which has to get added to the equation.

Thanks Dave!

What could be more simple!

thermomax
Thermomax has some efficiency graphs.

1000Watt/m², 900Watt/yd², or 100Watt/ft²

 800Watt/m², 700Watt/yd², or  80Watt/ft²

Power out thermal  = 61 Watts / ft² = 80 * 76%      

Power out electric =  9 Watts / ft² = 80 * 76% * 15%

Here is a graph of the solar influx from the sun on the earth. Note, it varies during the year with the maximum in winter and minimum in summer.

This data is based on a equation on page 9-10 in:
duffie2
"Solar Engineering of Thermal Processes"
Second edition
Duffie & Beckman
I got mine for about $100us in 1999 at Barnes and Noble:
Get the book here.

Note, this equation is not rigorous as it shows the variation in influx has a sinusoidal shape which it isn't in reality. It's close enough for most purposes.

I'm done ranting for now because this web site has all the proper data for solar collectors.

latentheat
Latent Heats of Fusion for various substances. All are in BTU/ft³ and melting temperature in °F.

	BTU/ft3	@ °F
Ferric Chloride III	20625	599°F
Potassium Nitrate KN03	11968	611°F
Calcium Nitrate Ca(NO3)2	11968	1041°F
Sodium Nitrate NaN03	11968	590°F

specificheat
Sensible heat storage is similarly small because of the high temperatures. Common table salt, sodium chloride, stores 11000 BTU/ft³ between 212°F and 600°F and is only 53 ft³.

Silica sand stores about 10000 BTU/ft³ between 212°F and 600°F and is only 60 ft³.

10 days of storage for even sand is a cube 8.5 feet on a side. This is the size of a large closet.

Specific heats for various substances pilfered from Marks Standard Handbook ninth edition, The Engineering Toolbox, Wikipedia, and ASI In BTU/(lb°F) and BTU/(ft³°F) mean values for the temperature range of 32-212°F.
(kJ/m³°K) * 0.01492064442128 = BTU/(ft³°R)

	Capacity	Density		Capacity	Density		Capacity	Density		Capacity	Density
	BTU/(lb°F)	BTU/(ft3°F)		BTU/(lb°F)	BTU/(ft3°F)		BTU/(lb°F)	BTU/(ft3°F)		BTU/(lb°F)	BTU/(ft3°F)
Alumina	0.183	46	Aluminium	0.214	36	Basalt (lava)	0.2	?	Borax	0.229	25
Brass	0.089	48	Brick	0.22	27	Bronze	0.104	?	Carbon (coke)	0.203	?
Chalk	0.215	?	Charcoal	0.2	?	Cinders	0.18	?	Concrete	0.156	32
Glass, crown	0.16	?	Glass, flint	0.12	?	Glass, normal	0.2	28	Gniss	0.18	?
Granite	0.2	28	Graphite	0.2	27	Gypsum	0.26	37	Humus (soil)	0.44	?
India rubber	0.37	?	Iron	0.109	58	Limestone	0.217	32	Marble	0.21	34
Paraffin wax	0.69	35	Propane	0.36	45	Porcelain	0.22	33	Quartz	0.23	38
R-12	0.15	?	Salt, rock	0.21	28	Sand	0.195	20	Silica, SiO2	0.191	23
Water	1.0	62.52	Wood, fir	0.65	?	Wood, oak	0.57	27	Wood, pine	0.67	21
	Capacity	Density		Capacity	Density		Capacity	Density		Capacity	Density
	BTU/(lb°F)	BTU/(ft3°F)		BTU/(lb°F)	BTU/(ft3°F)		BTU/(lb°F)	BTU/(ft3°F)		BTU/(lb°F)	BTU/(ft3°F)
Brass	0.089	48	Bronze	0.104	?	Iron	0.109	58	Glass, flint	0.12	?
R-12	0.15	?	Concrete	0.156	32	Glass, crown	0.16	?	Gniss	0.18	?
Cinders	0.18	?	Alumina	0.183	46	Silica, SiO2	0.191	23	Sand	0.195	20
Graphite	0.2	27	Glass, normal	0.2	28	Granite	0.2	28	Charcoal	0.2	?
Basalt (lava)	0.2	?	Carbon (coke)	0.203	?	Salt, rock	0.21	28	Marble	0.21	34
Aluminium	0.214	36	Chalk	0.215	?	Limestone	0.217	32	Brick	0.22	27
Porcelain	0.22	33	Borax	0.229	25	Quartz	0.23	38	Gypsum	0.26	37
Propane	0.36	45	India rubber	0.37	?	Humus (soil)	0.44	?	Wood, oak	0.57	27
Wood, fir	0.65	?	Wood, pine	0.67	21	Paraffin wax	0.69	35	Water	1.0	62.52
	Capacity	Density		Capacity	Density		Capacity	Density		Capacity	Density
	BTU/(lb°F)	BTU/(ft3°F)		BTU/(lb°F)	BTU/(ft3°F)		BTU/(lb°F)	BTU/(ft3°F)		BTU/(lb°F)	BTU/(ft3°F)
Sand	0.195	20	Wood, pine	0.67	21	Silica, SiO2	0.191	23	Borax	0.229	25
Graphite	0.2	27	Brick	0.22	27	Wood, oak	0.57	27	Salt, rock	0.21	28
Granite	0.2	28	Glass, normal	0.2	28	Limestone	0.217	32	Concrete	0.156	32
Porcelain	0.22	33	Marble	0.21	34	Paraffin wax	0.69	35	Aluminium	0.214	36
Gypsum	0.26	37	Quartz	0.23	38	Propane	0.36	45	Alumina	0.183	46
Brass	0.089	48	Iron	0.109	58	Water	1.0	62.52	Gniss	0.18	?
Glass, flint	0.12	?	Basalt (lava)	0.2	?	Charcoal	0.2	?	Carbon (coke)	0.203	?
Chalk	0.215	?	India rubber	0.37	?	Humus (soil)	0.44	?	Cinders	0.18	?
Wood, fir	0.65	?	Bronze	0.104	?	Glass, crown	0.16	?	R-12	0.15	?

phase
PCM Thermal Solutions
PCM Thermal Solutions is a research and development and consulting firm specialized in the design, development, testing, and evaluation of thermal management of engineering systems and components using Phase Change Materials

teap
TEAP Energy
TEAP Energy is RECOGNISED WORLDWIDE as the LEADER in Phase Change Material (PCM) development, application and manufacture for superior ENERGY EFFICIENCY.

plusice
Environmental Process Systems Limited
Plus Ice
Thermal Energy Storage (TES) is a useful tool to reduce energy requirements by means of spreading the load and taking advantage of lower ambient and off-peak utility rates. Hence TES reduces the overall environmental and economical impacts for given cooling or heating applications.

doerken
Doerken's PCM

Phase Change Materials
by Jonathan Gates
Phase Change Material Research
Here you will find useful links to sites concerning Phase Change Materials (PCM'S) and probably the largest and most comprehensive reading list in relation to PCM's ever compiled.

Phase Change Materials
Dissertation by Carl Vener
PHASE CHANGE THERMAL ENERGY STORAGE
A thesis submitted in partial fulfillment of the requirements of the University of Brighton for the degree of Building Surveying.

1 Watt       = 673 lumen

1 footcandle = 1 lumen / ft^2
1 lux        = 1 lumen / m^2

This is a reference that discusses the light needs for plants.
http://www.aeroponics.com/aero65.htm
This reference says: Only 37% of the power in sunlight is within the wavelength (colors) useful for photosynthesis, while 62.4% is infrared (thermal power) and the remaining 0.6% is ultraviolet. Photosynthesis in the plant leaf is powered by 1% of the sunlight that falls on the plant, 10% of the sunlight is reflected and 10% passes through the leaf. The leaf will retain 80% which is used for transpiration. Some of the light is re-radiated, while the fraction that remains is used for building building food from the carbon dioxide, minerals and water. (The Solar Greenhouse Book)
spectrum
Click to enlarge
Click to enlarge
And the spectral characteristics of sunlight, fluorescent, and incandescent lamps.
They also describe the growing potential for various lamp types especially the Metal Halide Lamps.

chromaticity
Chromaticity
Chromaticity standards.

bandgap
Bandgap
Bandgap Voltage vs Color
An unexpected discovery could yield a full spectrum solar cell.
The serendipitous discovery means that a single system of alloys incorporating indium, gallium, and nitrogen can convert virtually the full spectrum of sunlight ( from the near infrared to the far ultraviolet ) to electrical current.

The LED FAQ Pages.
a compilation of questions and answers relating to Light Emitting Diodes and their Infrared Emitter cousins. These questions all seem to come up again and again on newsgroups like sci.optics and sci.electronics.design.

Don Klipstein's LED Main Page.
Bright and efficient LED lamps! Efficiency of some good ones and some runner-ups in lumens per watt, millicandela and beam angle ratings for most of these, where to get most of these. Also links into Agilent / Hewlett Packard's LED web site.

LED's as Photo Cells

I independently discovered that LEDs make good photovoltaic cell sensors. They have to small of a chip area to compete with silicon PV panels to generate power. However, when used as light sensors they have some advantages over other sensors. Green LEDs generate the most voltage. Generally the current is less than 10uA but when directly aimed at the sun the large ones can get to 150uA.

I developed a solar tracker based on these concepts called the LED3 Solar Tracker.

Blue   = 3.0 V
Green  = 1.74V
Yellow = 1.5 V
Red    = 1.25V

light
Light Measurement Handbook

A very neat book that describes in graphical detail the relationship
between gradient and luminous fluxes and Irradiance and Illuminance.
This is a free publication/advertisement on all aspects of light measurement.

photomet

Definition of terms used in Radiometric and Photometric measurements.

conversion

How do I convert between candlepower and watts?

Many LEDs have an output rated in candela which is a unit of source radiation and equivalent to 1 lumen per steradian. This makes it difficult to compare the illumination qualities of LEDs with conventional lamps.

LEDs output their light in a narrow beam compared to the omnidirectional radiation pattern of conventional lamps. To convert the candela output of LEDs to lumens one must factor in the radiation pattern of the LEDs.

To convert candelas to lumens one must first determine the average steradian angle of the LED.
For a 15deg angle the steradian angle is .01704 solid degrees and
for a 30deg angle the steradian angle is .06699 solid degrees.

As an example:
2000mCd with a 15 degree divergence angle and an electric power consumption of .06W. the equivalent lumens is:
2Cd * .01704lumen/Cd = .03408 lumens
.03408 lumens / (673 lumens/W) = 50.6uW of light
The electric to light efficiency is:
50.6uW / 60mW = .84% efficient
If someone can show me where I have failed in these calculations I would appreciate it. I'm not comfortable with the theory.
Thanks!

From examining the Lamp Data Table I have concluded some useful
Rules of Thumb.

Lamp Type	lumens/Watt	Efficiency
White LEDs	15	2%
Incandescent Lamps	20	3%
Colored Visible Light LEDs	20	3%
Mercury Vapor Gas Discharge Lamps	47	7%
Fluorescent Gas Discharge Lamps	67	10%
Electro Luminescent Light Sources	80	12%
Metal Halide Gas Discharge Lamps	101	15%
Sodium High Pressure (HPS) Lamps	135	20%
Sodium Low Pressure (LPS) Lamps	168	25%

Lamp Data Table

Lamp Type	lumens/Watt	Efficiency	Reference
Incandescent Edison's first lamp	4 to 1	0.6% to .15%	Grainger lighting definitions
Incandescent Standard Lamp 15W	8	1.2%	Grainger's GE# 12658
Incandescent Standard Lamp 40W	11	1.6%	Marks (3) Table 12.5.3
Incandescent Standard Lamp 40W	13	1.9%	Grainger's GE# 13255
Incandescent Halogen Lamp 50W	14	2.1%	Grainger's GE# 16746
Incandescent Standard Lamp 60W	14	2.1%	Grainger's GE# 41026
Incandescent Standard Lamp 100W	17	2.5%	Grainger's GE# 41034
Automotive Standard Lamp 21W 24V	18	2.6%	Clare GE# 13498
Incandescent Halogen Lamp 90W	18	2.6%	Grainger's GE# 16746
Incandescent Halogen Lamp 90W	18	2.6%	Grainger's GE# 16746
Automotive Standard Lamp 21W 12V	21	3.2%	Clare GE# 12498
Incandescent Standard Lamp	24 to 6	3.6% to 0.9%	Lighting Fundamentals
Automotive Halogen Lamp 22W 12V	25	3.7%	Clare Philips
Mercury Vapor 40Watt	28	4.2%	Grainger's GE# 12460
Mercury Vapor 75Watt	37	5.5%	Grainger's GE# 12461
LED White	40	5.9%	Elektronik
Mercury Vapor 100Watt	40	5.9%	Grainger's GE# 12467
Mercury Vapor 250Watt	48	7.2%	Grainger's GE# 32127
Mercury Vapor 175Watt	49	7.3%	Grainger's GE# 14111
Fluorescent Lamps 40T12	49	7.3%	Marks (3) Table 12.5.4
Fluorescent Compact Double 10W	50	8.2%	Grainger's GE# 30031
Mercury Vapor 400Watt	56	8.4%	Grainger's GE# 23998
Fluorescent Power Groove PG17	60	8.9%	Grainger's GE# 47732
Fluorescent Compact 20W	60	8.9%	Philips BC-SLS 20
Mercury Vapor	60 to 25	8.9% to 3.7%	Lighting Fundamentals
Fluorescent Compact Triple 18W	62	9.2%	Grainger's GE# 10449
Fluorescent Compact Triple 26W	62	9.2%	Grainger's GE# 12278
Mercury Vapor 1000Watt	63	9.4%	Grainger's GE# 24191
Mercury Vapor	63 to 24	9.4% to 3.6%	Marks (3) Table 12.5.2
Fluorescent Compact Double 18W	64	9.6%	Grainger's GE# 30035
Fluorescent Compact Triple 13W	65	9.7%	Grainger's GE# 11982
Fluorescent Compact Double 26W	65	9.7%	Grainger's GE# 30042
Fluorescent Compact Triple 32W	69	10%	Grainger's GE# 12781
Fluorescent Compact Double 13W	69	10%	Grainger's GE# 30035
Metal Halide Halarc 32Watt	78	12%	Grainger's GE# 12651
Metal Halide Halarc 70Watt	79	12%	Grainger's GE# 12377
Electro Luminescent type TC	80	12%	World Products Inc
Metal Halide Multi-Vapor 175W	80	12%	Grainger's GE# 18902
Fluorescent Lamps 40T12	84	12%	Grainger's GE# 15079
Sylvania Xenarc Auxiliary Kit	84	12%	Sylvania web site
Metal Halide Halarc 100Watt	90	13%	Grainger's GE# 12381
Metal Halide Multi-Vapor 400W	90	13%	Grainger's GE# 18904
Metal Halide Halarc 175Watt	95	14%	Grainger's GE# 11420
Sodium Low Pressure (LPS) 18W	100	15%	Grainger's GE# 21294
Metal Halide Multi-Vapor 1000W	110	16%	Grainger's GE# 18904
Metal Halide	115 to 50	17% to 7.4%	Lighting Fundamentals
Metal Halide	125 to 69	19% to 10%	Marks (3) Table 12.5.2
Sodium Low Pressure (LPS) 35W	131	20%	Grainger's GE# 21296
Sodium Low Pressure (LPS) 55W	139	21%	Grainger's GE# 21297
Sodium High Pressure (HPS)	140 to 73	21% to 11%	Marks (3) Table 12.5.2
Sodium Low Pressure (LPS) 90W	142	21%	Grainger's GE# 21298
Sodium Low Pressure (LPS) 135W	163	24%	Grainger's GE# 21299
Sodium Low Pressure (LPS) 180W	183	27%	Grainger's GE# 30203
Sodium High Pressure (HPS) LUCALUX 35W	64	9.6%	Grainger's GE# 11668
Sodium High Pressure (HPS) LUCALUX 50W	80	12%	Grainger's GE# 11345
Sodium High Pressure (HPS) LUCALUX 70W	91	14%	Grainger's GE# 11339
Sodium High Pressure (HPS) LUCALUX 100W	95	14%	Grainger's GE# 11250
Sodium High Pressure (HPS) LUCALUX 150W	107	16%	Grainger's GE# 13252
Sodium High Pressure (HPS) LUCALUX 400W	128	19%	Grainger's GE# 44054
Sodium High Pressure (HPS) LUCALUX 1000W	140	21%	Grainger's GE# 44058

Chemistry
Process Chemicals.

The following sites have data on solar chemistry.

Paul Scherrer Institute

IEA SolarPACES Program

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