About the efficiency of lamps, including LEDs. Comparing incandescent and LED lamps – which is better?

The photo shows a 20 Watt LED lamp. It replaced two 75 watt incandescent bulbs and is a little brighter than them.

But before we talk about LED lamps, let's dispel a few myths that have already quite firmly won their place in the minds of users. At the same time, we will consider the questions of what LED lamps are, how to choose (we recommend considering the Mantra LED chandeliers catalog), why they are better, why they are worse, and why they have such powerful advertising support today.

What temperature is the light in your house: warm or cold?

In fact, the question is not idle, since it is the spectrum that makes the light its own, pleasant to the eye (warm), or, on the contrary, bright (cutting), that is, cold. Different use different principles converting electricity into light, which is why their spectrum is different. This is where the first myth arose - the light of LED lamps is the most natural. In fact, this is not entirely true; LED lamps for the home can have any spectral glow, and in this case the advantage of these lamps becomes a disadvantage. Not every consumer will look into the technical specifications to figure out what's what.

The second myth was born from the labeling, and is that the power of LED lamps is lower than all others.

The third myth is the most complex; they worked on its creation for a long time, driving into our heads the idea that LED lighting The apartment is the most energy efficient.

There is another rumor that it is better not to use LED lamps for the home, since they cannot withstand smooth adjustment or voltage surges, and also quickly fail if turned on frequently.

Let's start from the very beginning, because understanding what an LED is will help us make our decision, not based on rumors, myths and machinations of incandescent lamp sellers.

Where and what kind of light from LED lamps do we see?

The answer right away is the one you chose, both from the point of view of light temperature (spectral characteristics) and from the point of view of power consumption per specific illuminated area. Or, to put it simply, an incandescent lamp of one hundred watts will always shine at one hundred watts in the way it can, while an LED will not only shine where it is needed, but also with the light that is pleasant to you. And either the element (point) or the surface will glow, depending on which LED lamp was chosen for this area of ​​the room.

The most controversial issue is the issue of energy saving. This myth was born as an argument in a dispute between competing manufacturers, and if we consider it honestly, then energy saving lamps Indeed, they consume slightly less energy for lighting than LED lamps. Ask how to choose here? If you believe the manufacturers, then no way. This is parity. The balance of a fragile world at war. True, LEDs are rather the injured party here, since they appeared on the market after large corporations invested a lot of money in energy saving, deciding that LEDs were too expensive a toy.

And then, one event happened that is directly related to the subtitle. It turned out that the spectral characteristics of LEDs are slightly better than even daylight. It turned out that the light of LED lamps does not have flicker, which even incandescent lamps have. In an incandescent lamp this is the mains frequency (usually 50 Hertz), and in a fluorescent (energy-saving) lamp it is a multiple of the triple phase, that is, approximately 3 Hertz. Probably everyone has seen “blinking” fluorescent lamps? This is the same. The lamp glows only when there is current; as long as there is no current, it does not shine. It's just more noticeable in fluorescent lamps.

The LED lamp does not have this drawback; it is not sensitive to current, voltage drop, or frequency. There is tension - it shines, no - it does not shine.

If you work a lot at your desk, with documents or small work, buy table lamp on LEDs and forget about eye fatigue. Problems with vision during such work are the same flicker that we do not notice.

What is the difference between the physics of light from LED lamps and all others?

Basically energy conversion. This is what solves several lighting problems:

1. Minimum electricity consumption for lighting.
2. The most correct spectrum of room lighting (zones in the room).
3. Spot lighting of a selected area (for example, a painting).
4. Durability and reduction of heating of the luminous element.
5. Possibility of control spectral characteristics lighting.
6. Minimum cost of lighting devices.

All these problems were solved by LED lamps. All that remains is to decide how to choose the right ones and it’s in the bag. True, LED lamps do not solve the last point in any way, being even now the most expensive. It's all about that very transformation. The LED directly, without intermediaries, converts electrical energy into light. It's pretty new technology, therefore point 6 is still becoming a limitation in choice for many.

Simple numbers in the useful conversion of electricity into light

• Incandescent lamp. Efficiency 12% loss 75% (coil heating);
• Modernized incandescent lamps. Efficiency 15% loss 68% (filament resistance);
• Induced glow lamps (fluorescent, mercury, etc.). Efficiency 22% losses 45% (reactive, starting currents);
• LED lamps. Efficiency 58% losses 18% (switching);
• Closed circuit lamps. Efficiency 84% loss 6% (closed cycle until the end of the battery charge).

If you add up these numbers, you will not get 100%. This is an experimental factor. But the efficiency value is exactly how much electricity becomes light. Closed-cycle lamps are street-type lamps with solar panels and batteries. They do not require energy costs, and if desired, you can even read a newspaper by their light. Everything else can be seen from the numbers above.

A little more physics. Piezoelectrics (remember the “eternal lighters for gas stoves”?) When producing a “spark” when pressed, they do not waste “matter”. They can really “eternally” produce a discharge spark when you press a key. And no batteries are needed. An LED works in much the same way. Voltage is applied to the contacts, and the material emits a photon of light. The lamp begins to shine. We don’t know how long such lamps can shine, since they started working not so long ago, and no one yet knows what the energy saturation of excited materials is with “light.” One thing is obvious: LED lighting in an apartment will last for many years. Simply put, within a single apartment it is a kind of “Eternal Light Illuminator”. At least in theory. Let's now come down to earth and see what happens in practice.

Practical recommendations for choosing lighting with comments and tips

Before we get to the question of how to choose LED lamps, a little about technical specifications. Let's start with the main thing: with what shines.

The glow of an LED lamp is a continuous (flicker-free) transformation electrical energy into the world In other words, 1 kWh of energy will be converted into light with an efficiency of at least 60%. This, by the way, is the answer to the question, I want LED lamps, how to calculate the power, in comparison with incandescent lamps? It's simple. LED efficiency is at least 60%, Lamp efficiency incandescence no more than 12%. Hence the ratio – led lamp At 30 watts it shines as brightly as a 150 watt incandescent lamp. And there’s no catch, because with this comparison, an LED lamp will still consume almost half as much electricity. More precisely, you will pay half as much for the same lighting.

When choosing an LED lamp, pay attention to the following factors:

• We select LED lamps first by power, taking into account the reduction factor - a 100-watt incandescent lamp is a 12-watt LED lamp. We assure you that their luminosity will be the same. True, the light of an LED lamp will be warmer and more pleasing to the eyes.
• The second point of choice is the spectrum. Few people think about what it means when they read the Kelvin number on the packaging. The fact is that other lamps simply cannot have exactly this characteristic - that very “light temperature”. However, it is worth remembering that the higher the number, the brighter and warmer the light of LED lamps will be in your home.
• The possibility of smooth adjustment (dimmer control) is also indicated on the packaging as the note “smooth brightness control is allowed.” If you decide to spend money on saving, it is worth keeping in mind that LEDs can be “dimmed” if full light is not needed.
• Compliance with standards. Agree, expensive lamp, which there is nowhere to insert, this is the same case - money down the drain. Lamps with all types of bases and almost any form of luminous element are now produced:

Basic selection options

What do we have as the main parameters? This is not as simple a question as it seems.

1. Manufacturer? Warranties and service life? Applicability in networks with unstable voltage?
2. Possibility of switching on in difficult conditions (including for outdoor use) and under overloads?
3. Approximate amount of savings if you use only LED lamps for lighting?
4. Comparative cost of lighting devices if everything is replaced with LED lamps.

1st question. It is very difficult to understand who the manufacturer is, whether there is a warranty on the product, and how long it will last. Based on the characteristics, it is sometimes difficult to understand whether this lamp is for 220V or 127V? Often the spectrum of a lamp is indicated as a point on a scale that no one except a scientific optician can understand. Permissible voltage fluctuations are not written down at all, except perhaps in the lamp’s passport, as a strange-looking sinusoid.

2nd question. Any LED lamps can be turned on and off under any overload conditions. This is the first type of lamp that continues to shine after short circuit online. Also, this is the first type of lamps whose luminous element cannot fail due to network overloads. Strictly speaking, an LED lamp can generally fail only through physical destruction. At least, there is no data yet on the cessation of glow for other reasons. And these lamps have been studied for 12 years. An interesting finding is that the power of LED lamps allows them to act as a kind of fuses against network loads. Have you heard the words “Diode bridge”? So here is an LED lamp, a kind of trigger that can relieve excess load in the form of a flash. You may not see it, but your power grid will be grateful for such a discharge.

3rd question. 100 watt incandescent lamp at continuous operation uses 100% of the electricity received throughout the year. The meter will count this electricity and convert it into a payment receipt from the energy company. If we replace an incandescent lamp with an LED lamp that has worked for the same long time, then we will also receive a bill for payment from the energy sector. True, this account will differ from the first. If we paid 100 rubles for an incandescent lamp, then we will pay 18.5 rubles for an LED lamp. Of course, you may not believe this, so take a calculator and do the math. Better yet, install LED lighting in your apartment, and after a month compare bills from energy companies.

4th question. The difference in price will be approximately 8 times for incandescent lamps. That is, for the same lighting with LED lamps, you will pay about 7-8 times more than for incandescent lamps.

Real savings

It has now become obvious that, given the sharp rise in energy costs, the payback period for all energy-saving devices has been significantly reduced in time. In addition, it is worth remembering that all these devices are usually a product high technology, capable of working for many years in a row. Therefore, when choosing lamps, do not think about whether it will be LED or not. Look at the manufacturer, the quality of the font on the packaging, the company name, and electrical compatibility. Then remember that a 100-watt incandescent light bulb (at a price of 10 rubles) will cost you 4 times kWh (there are 24 hours in a day), that is, 4 (24 0.1) at least 10 rubles a day if you forget to turn it off. And an LED lamp for a home of comparable power, costing 200 rubles, with the same forgetfulness will cost only 1 ruble 15 kopecks.

We will not impose our opinion, but in our team there are few who have not replaced conventional lamps with LED ones. Not for energy-saving lamps, but for lamps that save money!

After writing the previous article, I myself still had an unanswered question: what exactly is more profitable to buy and how much you can win in the long and short term. Plus, there are still some uncertainties about the efficiency of LEDs. And the question encourages me to search for an answer to it, so I continued to develop this direction. I won’t say that the material turned out to be a full-fledged article, but as a supplement to the previous information, it contains essential data that will be useful.

First, let's figure out exactly what the efficiency of the LEDs discussed in the last part is. Previously, I took the data mainly from the iva2000 article, without checking it, because... there they considered more the issue of the efficiency of photosynthesis when illuminated with light of a different spectrum. Now I decided to look into the overall efficiency.

We will consider LEDs from CREE, because... on the one hand, they are today the most advanced in technology and, accordingly, light output per unit of power, and on the other, all their indicators are stable and well documented (unlike no-name manufacturers). Here the specified company should pay me for advertising, but alas, I am not writing on their behalf, but simply because it is easier and more accessible.

So, what kind of LEDs will we study? I will not post here the entire process of studying and selecting specific series, so as not to flood the material with “water”. In short, I will say that I absorbed the most powerful and at the same time the most efficient chips, subject to free availability and favorable price. According to these criteria, two types are suitable: white ones will be from the XM-L series.

These are 10-watt chips with an efficiency of 158 lm/W (but not at maximum power, and only at 1 W). Cool white (6000-6500K), neutral white (4000-4500K) and warm white (3000-3500K).
And red ones from the XP-E series, High Efficiency Photo Red 650-670nM.
Links to LED documentation at the end of the article.

Let's deal with the whites. Last time, the difference in efficiency of white LEDs was not taken into account and the efficiency was assessed only in relation to the McCree photosynthetic activity curve.

This time I decided to clarify this issue more thoroughly. Unfortunately, the documentation for LEDs never gives the efficiency, but only writes lumens per watt, so I had to do a reverse calculation. Based on the spectrum of the LED and the photopic curve, it is calculated how many lumens the LED would have if its efficiency were 100%, and then the number of real lumens taken from the documentation for the LED is divided by this number. And this is what we got for three types of white LEDs:

It is noteworthy that despite the increase in lumens during the transition from cold-white to warm-white spectrum (at the same power radiation), table values lm/W and the overall efficiency of the LED drops very significantly - from 40 to 23%. The thing is that the phosphor, of which there is much more in a warm-white LED, is not 100% efficient, and even, apparently, with its large quantities has a shading effect (rays emitted by the lower layers are absorbed by the layers above and disappear). At the same time, the lumen per watt indicator is used at a current of 2A (out of a maximum of three) - it can be seen that it drops from 140 at 350mA to 108 (for cool white). There is no such table in the Cree document - absolute lumens are given there at a given current, and the power must be calculated using the data from the graph current-voltage characteristics. Here is the relevant data from the datasheet:

With them everything is a little simpler, because... The luminous flux is indicated not in luminas but in milliwatts. It is enough to divide the milliwatts of radiation by the watts of consumption and we get the efficiency with high accuracy! If only the LEDs would provide this data, 2/3 of the work wouldn’t have to be done!

They're already looming interesting options use of individual LEDs and their combinations. Now let's recalculate the efficiency table taking into account the newly obtained data.

It can be seen that the red Photo-red are ahead of everyone by a large margin. But you can’t illuminate with pure red, so you need to combine it, and here there are options with white and blue. Let’s immediately note (I considered everything, but threw out what didn’t turn out promising) the combination of warm white and red. The low efficiency of warm white LEDs negates all the advantages of red ones. But cool whites are very good in this combination! They themselves have good efficiency, further enhanced by red LEDs, and the lack of the red spectrum is also covered by them. The combination of red and blue also looks good. Then there are just cold whites and HPS 1000, and the rest don’t really hold up. Well, let's see how it will look complete - with drivers.

Further, the logic of the calculations was based on the assumption that we want to get more photosynthetically active radiation for the same money, so all figures, including prices for LEDs and drivers, are given to the total value of phytoactive radiation of the lamp 100 µmol/s.

Color coding as in the previous table - to make it easier to understand where which LEDs are and not take up space with repeating headings.

But this is only the starting price - how much money you need to invest to get a 100 µmol/s light bulb. This is not enough - you need to see how much it will cost to operate. And if you also count the energy costs over time, then you get a complete picture, which I present for everyone to see!

Saved for history, updated below

Thanks to the close attention of commentators, it turned out that not all LEDs that are sold on Aliexpress under the name CREE are actually LEDs. The cheapest of them, about $1.50 for a 10-watt diode or less, are most likely counterfeits with manufactured chips Chinese company LatticeBright, which are several times cheaper than the original ones and, unfortunately, have approximately 2 times worse performance. In this regard, I searched for prices of the corresponding LEDs in the company Compel, which is the official distributor of cree in the Russian Federation. Prices there are much higher than in China, but small wholesale is quite profitable, including compared to foreign suppliers.
And along the way, I corrected two points - I added lamp replacement once a year for the HPS curve. And I corrected an error (my oversight), due to which the price of all lamps was calculated at the same power (100W), whereas the original idea was per unit of photoactive radiation. In the new chart, these prices are for a lamp emitting 100 μmol/s, not 100 W. I apologize for the oversight.

How to make sense of this bundle of twigs?

On the left is the price of the lamp at the start. Let me remind you that in this case they will all emit the same amount of phytoactive radiation, but have a different spectrum. The lower the bar starts, the cheaper the set. On the X axis we have months. It is assumed that the lamp operates 12 hours a day, 7 days a week, for a total of 36 months, i.e. 3 years. This is only a little more than 13 thousand hours, and for LEDs it is stated 50 thousand. And if everything is done correctly with cooling, and the LEDs are also supplied with a current of 0.7 of the maximum (this means more efficiency by a whole third), then they will work even more , i.e. more than 10 years with virtually no degradation.

The more horizontal the line is, the greater the efficiency of the lamp. We see that many lines start higher (more expensive chips), but over time they turn out to be cheaper than cheaper analogues. The line for photo red LEDs is indicative of this - it has the smallest slope.

The most surprising thing is that the cheapest ones are now... The most expensive photo red LEDs! This is because they have the most high efficiency and the most “easily digestible” spectrum - they need the least amount at the beginning and they consume the least amount of electricity in the future! The combinations “Cold white + red photo red” are of great interest. On this chart The curve is shown with a ratio of white: red as 2:1 in power. And just “cold white”. These three lines fan out, where the outer ones are white and red LEDs, and the middle one is a combination of them. To grow plants, all components of the spectrum are needed, but in different combinations. It turns out that all options for combinations of spectra are most effectively covered by just one combination - cold white and red LEDs (but in different numerical ratios).
It is worth noting that the blue + red combination, although it has a lower slope than white + red, gives a significantly worse price/luminous flux indicator, so it does not catch up with the white + red combination even in 3 years. In a 10-year perspective it may be preferable, but this is an exceptional case.
The phytolamp turns out to be not so cheap. If you take into account its efficiency, it is more expensive than even cool-white LEDs, and in the long term... Money for electricity is a waste...
DNAT is not very cheap at first (I was surprised how much electronic ballasts for them cost, but Em It’s not worth taking ballasts - they have low efficiency, the lamp too due to flickering, they also hum and heat up like a stove) and over time they do not catch up - especially taking into account the replacement of lamps - which will have to be done at least once a year, which is displayed as steps on the graph. So off to the garden.

Here is the spectrum of a combination of white and red LEDs, superimposed on the MkCree curve (4:1 in power, did not change it to 2:1):

Of course, it is wrong to judge such things based on the beauty of the graphs, but given the numbers that say the same thing, in my opinion the graph is almost ideal in terms of covering the spectrum of the photosynthetically active range.

The conclusion remains the same - buy cool white LEDs and red CREE Photo red and you will get a lot of light for your plants and savings for your wallet!
It is also possible to illuminate with pure red LEDs; one of the commentators wrote about such an experience. This will be most appropriate if the plants are partially illuminated by natural light (vegetable garden on a windowsill, balcony, loggia, when direct sunlight does not hit at all or for a couple of hours a day - then the plants receive mainly blue rays from the sky, and they are sorely lacking in red ones, just like total intensity Sveta. Here red LEDs will fill the existing gap perfectly. Only these should be highly efficient LEDs with a radiation wavelength of 660 nM and it is better if they are CREE Photo red. That's it, I'm off to order diodes!

With the advent of energy-saving light sources on the market, people began to wonder which ones are better and whether it is worth replacing old Ilyich light bulbs. Next, we will try to compare incandescent and LED lamps in the most detail, providing tables, a little theory and video reviews! To do this, various criteria will be considered in order, ranging from performance characteristics to savings indicators.

A little history

So that you understand the difference in the appearance of both options, and, accordingly, the difference in what scientific and technological progress has been, let us present the following facts comparing incandescent and LED lamps by date of invention:

• The first light source (with a tungsten filament) was patented in the 1890s by Russian engineer Alexander Nikolaevich Lodygin. At the same time, the first attempt can be considered the invention on July 11, 1874 - a filament lamp.
• As for the LED, the first one whose glow was visible was invented in 1962. The man who invented LED lighting– Nick Holonyak, American scientist.

As you can see, even if you compare the date of invention of alternative options, you can see a huge difference of almost a century. However, the oldest light bulb is still “fighting for its place in the Sun,” which is its huge advantage.

Power and light output

The first step is to carry out calculations. One of the most important indicators The calculation is the luminous efficiency of the devices. For an older light bulb, the light output fluctuates between 8-10 Lm/W. As for LEDs, their light output efficiency is usually in the range of 90-110 Lm/W, although there are also models with an indicator of 120-140 Lm/W. From the above values ​​it is clear that in terms of lumens, LEDs are better than alternative option 7-12 times.

To help you understand how this will affect the comparison of incandescent lamps and LED light sources in terms of power, we will provide the corresponding table:

It can be seen that the power of the diodes is 5 times less, and at the same time the glow efficiency and brightness will be approximately the same.

To independently calculate the light output of a light bulb, you need its luminous flux (indicated on the packaging in “Lm” divided by the power “W”), as a result you will get the desired value. For example, if the luminous flux of an LED is 1000 lumens and the power is 13 W, the output will be 76.9 Lm/W.

Video review of significant differences in luminous flux

Difference in illumination indicators

Heat dissipation

The second, no less important point of comparison between LED lamps and incandescent lamps is the heat transfer from the product. The glass bulb of an incandescent lamp can heat up to 250 degrees (although the temperature is usually around 170). That is why such products are fire hazardous, and it is not recommended to use them when installing electrical wiring in a wooden house. In addition, Ilyich bulbs are difficult to unscrew from the socket if they have been working for a long time before (you can get burned). LEDs in this regard have proven themselves better than all existing options. Their maximum heating temperature does not exceed 50 degrees, which allows them to be used in any room.

Service life

But this indicator is one of the main advantages of diodes in comparison with incandescent lamps. These lighting sources can operate for over 50,000 hours, according to manufacturers. Older light bulbs usually have a service life of less than 1000 hours, which is 50 times less. For reasons of economy, it is better to buy an expensive but long-lasting light bulb once than to change a budget product every few months.

There is also a nuance here that you should be aware of. The high longevity ratings of LEDs are not an exact value. The fact is that diodes fade (degrade) over time, so after 40,000 hours you will no longer be able to enjoy the glow that you had immediately after purchase. You can learn more about it from our article.

Efficiency

Efficiency should also be taken into account when choosing products. Efficiency shows how much electricity is converted into light and how much into thermal energy (which is actually what causes the bulb to heat up). The efficiency is about 90%, which is a very high figure compared to the alternative option, in which only 7-9% of the electricity is converted into light.

Environmental friendliness

Unfortunately, many do not pay due attention to preserving the environment. People throw fluorescent lamps into trash cans, despite the fact that when the bulb is destroyed, mercury evaporates, which harms both the environment and the health of people around.

In this regard, a comparison of incandescent and LED lamps does not put any option in the lead. Both the diodes and the glass bulb can be simply thrown into the trash, without special disposal.

There is an opinion that the Ilyich bulb creates infrared and ultraviolet radiation, negatively affecting human health. In this regard, LED bulbs are completely safe.

Price

And, of course, the most interesting question that users often ask is how profitable it is to buy LEDs, because they are an order of magnitude more expensive. Today, on Internet forums you can read many reviews that refute or justify the savings of LED lamps. The lowest price for a high-quality diode light bulb is 300 rubles, while the alternative costs 20-25 rubles. Here you should independently analyze what is more important to you - a long service life and high efficiency indicators, or low cost and unnecessary overpayment. Based on this, comparisons can be made regarding cost savings. The power of diodes is 7-8 times less, the price is 10 times more. Take into account the service life and even without special calculations you can understand that it is more profitable to buy LED lamps. You can clearly see a comparison of the efficiency of LED lamps and incandescent lamps in the table below:

Other indicators

I would also like, based on the tables, to compare incandescent and LED lamps according to such characteristics as:

• current strength;
• fragility;

The traditional approach to LED lamps often leads to a misunderstanding of fundamental circumstances. We are talking about the efficiency of lamps and the influence of the design of LED and conventional lamps on the efficiency.

The efficiency of a luminaire is the ratio of the luminous flux coming out of the luminaire to the entire luminous flux created by the light source. For example, a lamp in the form of a light bulb without lighting fixtures, primarily without a reflector, has an efficiency of 100%. This does not mean at all that this is an ideal to which we must strive; for lamps - less efficiency, this does not mean worse. Any attempts to concentrate (direct) light leads to a decrease in efficiency. But the method of concentration and the quality of the reflector may be different, and the lamps will have different efficiency. You can compare luminaires by efficiency only those that have a similar light distribution(KSS), in this case the efficiency will be determined by the quality of the optical system of the lamp (reflector, glass). It makes no sense to compare luminaires with different KSS in terms of efficiency!

The fundamental difference between LEDs and lamps is that they only shine in one half-plane. That is, an LED lamp without lighting fixtures (100% efficiency) will be directed! The emission angle of LEDs without secondary optics is 90-120 degrees. For example, if we compare two “lamps” in the form of a light bulb and an LED (100% efficiency) with the same luminous flux, then on the axis of the lamp at the same distance the illumination will be approximately 2 times less than on the axis of the LED. If you try to collect the luminous flux of the lamp using a reflector (to achieve the same angle of radiation), then in any case you will not be able to obtain the same illumination that the LED provides due to reflection losses. In this regard, replacing a light bulb light source with an LED source in directional luminaires will make sense, even if these sources have the same luminous efficiency (lm/W).

If a luminaire with a lamp has flat glass, that is, the entire light source is “immersed” inside the lamp, The efficiency of the lamp will decrease significantly due to the fact that the main part of the light coming out of the lamp will be reflected, that is, with reflection losses. For an LED lamp of this design, there is practically no decrease in efficiency(only losses in glass are about 5%), although intuitively it seems that, by analogy with lamp lamps, the efficiency should decrease.

A tube luminaire with flat glass will have an efficiency of about 50-60%.

An LED lamp with flat glass will have an efficiency of about 95%.

This is the main fundamental difference between LED lamps and tube lamps. Directional LED lights are much more efficient than directional tube lights. This is due largely to the design features of LEDs, and not just to their high luminous efficiency.

Understanding this circumstance should lead to a revision of approaches to the calculation of lighting installations using LED lamps.

How efficient are LEDs really and how can you extend their lifespan?

How to measure their efficiency at home and increase the efficiency, as well as increase the durability of LED lamps?

To answer all these questions, it is enough to conduct several visual experiments, without using any complex laboratory instruments.
LED is one of the most efficient and easiest to use light sources. However, at the same time, it still wastes most of the energy consumed, converting it not into light, but into heat.

Of course, there is no need to compare LEDs with a regular light bulb; here they have run far ahead. But how high do you think their real efficiency is?

How to measure LED efficiency

Let's check this live, not by the labels on the packages and data from tables on the Internet, but by the colorimetric method at home.

If you lower an LED into water and measure the temperature difference before it turns on and some time after, you can find out how much energy from it will turn into heat.

Knowing the total amount of energy expended and the energy lost into heat, you can actually find out how much benefit from a given light source was converted into light.

The container in which measurements will be made must be insulated from temperature fluctuations outside and inside. A regular thermos flask is suitable for this.

With some modification, you will have a completely usable homemade colorimeter.

To isolate and prevent current leakage, all wires and terminals on the LED should be coated with a thick layer of electrical insulating varnish.

Before the experiment, pour 250 ml of distilled water into the flask.

Place the LED in water until it completely covers it. In this case, the light should come out freely.

Turn on the power and start counting down the time.

After 10 minutes, turn off the voltage and measure the water temperature again.

At the same time, do not forget to mix it well.

Now you need to repeat the experiment, but this time, tightly seal the matrix with some opaque material. This is necessary so that energy cannot leave the system in the form of light.

The experiment with the sealed specimen is repeated again in the same sequence:

• 250ml distilled water

• initial temperature measurement

• 10 minutes of “glow”

• final temperature measurement

1 of 4

After all measurements and experiments, you can proceed to calculations.

Efficiency calculation

Let's say for this model the average consumption of the light source is 47.8 W. Operating time – 10 minutes.

If we substitute this data into the formula, we find that over a period of 600 seconds, 28,320 J were spent on lighting the LED.

In the case of the sealed model, the water heated from 27 to 50 degrees. The heat capacity of water is 4200 J, and the mass is 0.25 kg.

Another 130 J per degree was spent heating the bulb, plus you need to add energy to heat the LED itself. It weighs 27 grams and is mainly composed of copper. The result is a figure of 27377 J.

The ratio of energy released and energy expended will be 96.7%. That is, more than 3% is missing. This is precisely heat loss.

In the case of an open LED, the water heated from 28 to 45 degrees. All other variables remained the same. The calculation here would look like this:

What conclusion can be drawn from all these experiments and calculations?

As can be seen from this small experiment, about 28% of the energy left the system directly in the form of light. And if we take into account 3% of heat losses, then only 25% remains.

As you can see, LEDs are still very far from being ideal light sources, as many sellers present them.

Even worse, there are often models on the market of extremely low quality with even lower efficiency.

Brightness and power

Let's now compare the brightness of different models and see what it depends on and whether we can somehow influence it. To make a reliable comparison, use a regular piece of pipe and a lux meter.

Let’s say a previously tested high-quality sample provides illumination of 1100 lux. And this is with a power consumption of 50 W.

What if you take a cheaper model? The data may turn out to be two times lower - less than 5500 Lux.

And this is with the same power! It turns out that you will pay the same amount for light as in the first case, but you will receive it 50% less.

Is it possible to get 3 times more light while spending as little energy as possible?

It is possible, but for this you will need an LED operating in a slightly different mode. To understand how to do this, you need to take some more measurements.

First of all, you should be interested in the dependence of brightness on power consumption. Gradually increase the power and monitor the lux meter readings.

As a result, you will reach such a nonlinear relationship.

If it were linear, you'd get something like this.

It will turn out even more interesting if you calculate the relative efficiency of the LED, taking the power value of 50W as 100%.

You can see how its effectiveness is deteriorating. This deterioration with increasing power is inherent in all LEDs. And there are several reasons for this.

Why LED Efficiency Deteriorates

One of them is, of course, heating. With increasing temperature, the probability of photon formation in the p-n junction decreases.

In addition, the energy of these photons decreases. Even with good cooling of the case, the temperature of the pn junction can be tens of degrees higher, since it is separated from the metal by a sapphire substrate.

And it doesn't conduct heat very well. The temperature difference can be calculated by knowing the dimensions of the crystal and the heat generated on it.

With a heat release of 1 W, taking into account the thickness and area of ​​the substrate, the junction temperature will be 11.5 degrees higher.

In the case of a cheap LED, everything is much worse. Here the result is more than 25 degrees.

High junction temperatures lead to rapid degradation of the crystal, shortening its service life. This is where blinking, flashing, etc. occurs.

I wonder if manufacturers are unaware of this difference in temperature or are they deliberately creating doomed devices?

Often, components that seem to be in normal, expensive lamps operate in extreme conditions, at maximum temperatures, without any safety margin.

As long as the current is small, it is not noticeable. But due to the quadratic relationship, as the current increases, more and more of the energy turns into useless heat.

How to increase efficiency

That is, connect another LED in parallel, thereby halving the resistance losses. And this method certainly works.

By connecting two LEDs in parallel to the lamp instead of one, you will get more light with less energy and, accordingly, less heat.

Of course, this also extends the life of the LED.

You don’t have to stop and connect 3.4 diodes instead of one, it won’t be any worse.

And if there is not enough space for several LEDs, then you can install an LED originally designed for high power. For example, a 100-watt, 50-watt lamp.

It is in this way that the efficiency of the lamp can be increased several times, with the same energy consumption as the original source, but with less power, and operating at the limit of its capabilities.

Moreover, using no more than a third of the maximum power, you will forever forget what it is like to replace burnt-out LEDs.

At the same time, their operating efficiency and efficiency will increase noticeably.

Therefore, when purchasing LEDs, always be interested in the crystal size. After all, their cooling and internal resistance depend on this.

The rule here is that the more, the better.