An energy saving light bulb with the form factor of an incandescent light bulb. It comes from Technea Duurzaam, and is for sale at De Energie Bespaarshop.

See this overview for a comparison with other lightbulbs.

Summary measurement data

parameter	meas. result	remark
Color temperature	2850 K	Warm white
Luminous intensity Iv	31 Cd	Not so bright
Beam angle	274 deg	This light bulbs emits light all around
Power P	9.5 W
Power Factor	0.59	For every 1 kWh net power consumed, there has been 1.4 kVAhr for reactive power.
Luminous flux	344 lm	A lot of light
Luminous efficacy	36 lm/W
CRI_Ra	82	Color Rendering Index.
Coordinates chromaticity diagram	x=0.452 and y=0.417
Fitting	E27
Diameter	62 mm	Measured at the widest part of the lightbulb
Length	123 mm
General remarks		The ambient temperature during the whole set of measurements was 22.5-23.0 deg C. Warm up effect: present (more light due to warm up) Voltage dependency: present. At voltages above 240 V the dependency is stronger. For all raw measurement data follow this link (gogreen_11w_spaarlamp_ww_e27.zip).

E_v at 1 meter distance, or I_v

Herewith the plot of the average Luminous Intensity (I_v) dependent from the inclination angle with the lamp. Average here means that all Luminous Intensities measured with different turn angles but the same inclination angle, are averaged.

The radiation pattern of the lamp.

This radiation pattern shows a wide beam.

The luminous intensity dependent from the inclination angle, now with all turn angle measurements included.

The luminous intensity I_v is relatively constant until at about 90 degrees, and decreases slowly to get to its 50 % value at 137 degrees inclination angle. The beam angle of the light from this lightbulb is then 274 degrees.

The plot at the top of this paragraph shows the averaged luminous intensity values per inclination angle, which is used to compute the total luminous flux.

Luminous flux

With the luminous intensity data as a function of the inclination angle, it is possible to compute the luminous flux.

The result of such computation for this lamp is a luminous flux of 344 lm.

Luminous Efficacy

The luminous flux being 344 lm, and the power of the lightbulb being 9.5 W, yields a luminous efficacy of 344 / 9.5 [lm/W] = 36 lm/W.

A power factor of 0.59 means that for every 1 kWh net power consumed, a reactive component of 1.4 kVAr was needed.

Light bulb voltage	230 V
Light bulb current	70 mA
Power P	9.5 W
Apparent power S	16.1 VA
Power factor	0.59

Color Temperature and Spectral Power Distribution

The spectral power distribution of this lamp.

The measured color temperature is about 2850 K, and the light is warm white. The spectrum shows a lot of peaks, which is normal for a compact fluorescent light bulb as many phosphorescents are used inside the tube.

Chromaticity Diagram

The chromaticity space and the position of the lamp’s color coordinates in it.

The light coming from this lamp is close to the Planckian Locus (the black path in the graph).

Its coordinates are x=0.452 and y=0.417.

Color Rendering Index (CRI) or also Ra

Herewith the image showing the CRI as well as how well different colors are represented. The higher the number, the better the resemblance with the color when a black body radiator would have been used (the sun, or an incandescent lamp).

Each color has an index Rx, and the first 8 indexes (R1 .. R8) are averaged to compute the Ra which is equivalent to the CRI.

CRI of the light of this lightbulb.

The value of 82 is higher than 80 which is considered a minimum value for indoor usage. Since this lightbulb’s color temperature is less than 5000 K, it is compared with the light a black body radiator, such as an incandescent light bulb. When comparing, this light bulb renders the different test colors well enough.

Note: the chromaticity difference is 0.0011 which is lower than 0.0054, which means that the calculated CRI result is meaningful. This is because the chromaticity value of this lamp is relatively close to the Planckian Locus.

Voltage dependency

The dependency of a number of lamp parameters on the lamp voltage is determined. For this, the lamp voltage has been varied and its effect on the following lamp parameters measured: illuminance E_v [lx], color temperature CT or correlated color temperature CCT [K], the lamppower P [W] and the luminous efficacy [lm/W].

Lamp voltage dependencies of certain light bulb parameters, where the value at 230 V is taken as 100 %.

There is a dependency from the applied voltage. And the dependency there is, is also linear with applied lamp voltage. It indicates that the used power converter inside the lamp behaves in a stable manner. Except for voltages above 240 V, where the dependency is different. The cause for this has to be found most likely in the power electronics.

To check whether this dependency can lead to visible changes in illuminance for possible grid voltage changes, just check what variations occur when the lamp voltage varies around 230 V + and – 5 V. Then the illuminance varies < 20 % and will not be visible or noticeable.

Warm up effects

After switch on of a cold lamp, the effect of heating up of the lamp is measured on illuminance E_v [lx], color temperature CT or correlated color temperature CCT [K], the lamppower P [W] and the luminous efficacy [lm/W].

Effect of warming up on different light bulb parameters.

There is the well known effect of the warming up on the lamp parameters; the illuminance value E_v increases when the tube warms up. However the heating up of the complete light bulb with electronics is such that the uncreased light is decreased hereafter (maybe the electronics warm up more then). After 30 minutes there is little difference in illuminance value E_v compared with just after switch on.