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Seperate 100 Watt
Integrated 150 Watt
Overview “Low Bay Lights”
Background
Low Bay lights are used extensively in Petrol Garages, Lower ceiling manufacturing facilities, parking areas and a range of other applications where good lighting is required with power mounting levels. Most Low Bays are equipped with 400 Watt light globes. These are typically Sodium Vapour or Nickel Halide.
The light fitting involves a single body with a compartment for the power supply and starter and the compartment with the socket and Globe. Most of the Low bay are open as they are mounted under roofs. The total electricity consumption of these lights is the capacity of the globe plus 10%. In other words the 400 Watt light will use 400 plus 10% = 450 Watt of power. The power factor on these lights are normally worse than 0.6 which have a significant impact on the kVA demand.
To date various technologies have been explored to replace the Sodium Vapour or Nickel Halide globes currently used in the Low Bay fittings. All of these have proven to expensive, too difficult to change or not providing adequate light.
With the rapid development of LED lights, options are now becoming viable to displace the current inefficient lights. A new light has now been developed which capture various features in meeting various customer needs in the market. This paper sets out the features of the new LED Low Bay light with retrofit and backup lighting features.
Features of the light
The features of the new light can be summarised as follows:
- Much more efficient use of electricity to provide the light. (75% saving)
- Further power savings with daylight harvesting down to 10% of full power.
- Output can be adjusted from 150 Watt down to 90 watts to meet needs closely.
- These can be used for any type of Low Bays, with current capacity up to 400 Watts.
- Retrofit can be done on all current fittings by simply replacing bypassing the existing power supply and screw in the new LED into the existing socket lamp.
- Once retrofit has been done, future is simply a matter of changing the light as one unit.
- Only 10% failure expected in more than 50 000 hours.
- These lights have life expectancies up to 10 years continuous burning.
- The lights are completely modular and all components are replaceable. Future replacement / repair is thus easy.
- Lights can be switched on and off as the required. Lights shine within a second – no warn up or cool down required.
- The unit has power factor exceeding 0.9.
- A dust filter can be used in dirty environments.
- In the case where closed fitting are used in very dirty environments, the driver and light comes in 2 separate units but limited to 100 Watts.
New Light Design
The basic idea of the new LED Low Bay light is the retrofit of current Low Bay lights with a much more energy efficient LED light or installing new LED light with fitting.
The whole unit is complete as a conventional screw in globe. The product basically feature the following:
A single screw in light containing the following components:
- Screw in fitting with structure to hold the various components.
- A power supply which is a low voltage constant current supply.
- A light sensitive resister for daylight harvesting.
- A cooling fan.
- The heat sink.
- The high power LED.
The whole idea is that the light can be changed as is the case with existing globes. Except in this case there is no separate power supply but it is all integrated with the light.
New/Retrofit/Replacement
New installation / complete new fitting.
A complete new fitting can be fitted to the celling and be connected it to the main supply. The LED light is then screwed into the fitting.
Retrofit. The retrofit is done as follows:
- The old power supply and starter be removed or simple be bypassed.
- The Live and neutral wires from the light socket be connected to the Live and Neutral from the supply.
- The old globe be screwed out and the new screw in type LED light be screwed into the existing socket.
- The grubs crew is then released with the Alan key, the light is aligned with the ground / target area and then the grubs crew is tightened again.
Maintenance / replacement.
The replacement of the light is now a simple matter. An electrician is not required in the case when the power supply is faulty. The new light including the driver can be changed by anybody after the supply has been switched off.
Maintenance/Failures Procedures
The maintenance on the light is very simple:
In very heavily dusted / polluted environment:
- The unit can be blown off of any dirt.
- The cooling fins can be blown clean of any collected dust.
If the light starts to going down:
- This indicates the fan has failed.
- Change the light with spare and replace.
If the light goes off or dims:
- This could indicate a problem with the power supply or the LED.
- Change the light with spare one.
Light Intensity
The LED Low Bay comes in various options to meet different lighting needs. They have been developed to meet different customer needs in different ways as cost reflectively as possible. The following options are compared below:
- HPS (400) watt.
- Various LED options.
The comparative light spectrum for different lights are compared in the figure below:
It is clear that the LED’s lights can provide more light than existing HID lights with much lower power. In this particular case an LED option of about 115 Watt will provide the same light output as a 400 Watt HPS. The bottom line is that each individual application need to be designed and be tested and customers need to experience this new look. The LED delivers close to 130 lumens per Watt which is of the highest in the market.
Daylight Harvesting
The Elexpert LED’s feature the daylight harvesting feature. When the ambient light level is very lower the LED will be running at full power. As the level of ambient light increases the power output reduces accordingly. At ambient light levels close to 1000 Lux, the power output level will reduce to less than 20% of full power thereby providing even more savings. The % output at various levels of ambient light is shown in the table below.
On a cloudy day, where the ambient light in the building is about 100 Lux, the Led lights will substitute with 75% power.
Because South Africa is such a sunny country with more than 90% of the days having ample ambient light, consideration could be given to even consider reducing the light requirement slightly below the ideal requirement for these few day, obviously still within safety standards.
This feature will obviously not make a difference in areas where very little sunlight can come in. The type of light fitting can also have a bearing on the effectiveness of this feature.
Warrantee
All these units will carry a 3 year exchange warrantee. The faulty units will then be exchanged free of charge. The cost of changing the light will be for the account of the customer. This would not involve any costs for the customer by using the telescopic stick with bracket.
If any of the units fault after the warrantee period, the same process will apply except that a fee will be charged to collect / install / replace / repair the faulty components. It is important to note that only the faulty components will be replaced and be charged for.
LED
The LED used is the Luminus CXM-32 Cob Array. The specific unit used mainly is the CXM-32-50-70-54-AC00-F2-3 which yields 140 Lumens per Watt at 150 Watt with a CRI of 70. The LED can be selected based on customer’s requirements. The table below shows the Lumen maintenance curve for a similar Luminus LED with actual test of 6000 hours. The CXM 32 has only been released recently and therefore these results are not available yet.
The Luminus LED’s are well known worldwide and offer excellent Lumens yield.
Fan
The fan used is X-Fan RDL8025B4. This is a 48 Volt fan. The life cycle tests for this unit is shown below.
The working temperature for the fan would be less than 60 degrees C. This will yield a mean time between failures of more than 160 000 hours.
Life Expectancy
The life expectancy of the various key components of the product are as follows:
- The Power supply. – 10 years plus continuous.
- The fan. – 10 years plus continuous.
- LED. – 10% failure after 50 000 hoursusage.
- Other components. – At least 10 years.
The LED is so mounted that it can easily be replaced. When the LED thus goes faulty, only that has to be changed.
In the main thus these lights can easily be used for 10 years and more.
Power Factor Impact
The following should be noted in terms of power factor for the new LED installation:
- The power factor of the new LED with its power supply is better than 0.9.
- The power factor of a some of the HID lights are usually not better than 0.9.
- Many of them are however as bad as 0.6
- When these become faulty, the power factor could reduce to typically less than 0.6.
Because the power consumption of the new LED’s is so small compared with the existing lights, the total varh consumption would always be less as illustrated below.
What this shows is that only if the power factor on the new LED power supply drops below 0.83, would the amount of vars generated from the new LED power supply reach the level of the current lighting supply.
Electricity Savings
To calculate the electricity savings it is important to first understand the impact that the installation of the new LED lights will have on the electricity bills of customers. The following should be noted in this respect:
- The prices for customers differ all over South Africa.
- Eskom’s prices for large and industrial customers are generally the lowest in RSA.
- Different tariff structures are offered namely:
o Maximum demand tariffs with demand / access charges. These will charge for:
- the maximum demand taken in each month / year
- and will also penalise for a bad power factor
o Single or 2 seasonal energy charges.
o Or Time of use energy charges.
o Reactive energy charges.
The impact for every customer will be different and therefore a study has to be done for each customer individually. The impact that has to be determined is the following:
- To what extent is the energy reduced.
o This has to be done for kWh per the relevant period in the case of TOU and seasonal tariffs.
o The extent that the reactive energy charge (c/kvarh) is reduced.
- The extent that the maximum demand is reduced.
For the examples the following has been assumed:
- For the 24 houroperation the price would reflect all the charges as for a 100% load factor customer. This was calculated at a typical municipal large customer tariff at 400V.
- For the 10 hour per day 22 days per month operation it was assumed that the full demand would impact the saving in maximum demand because the times that the lights operate would co-inside with the operation of the business. (This would not necessarily be the same for security lights burning at night only.)
- The impact on the reactive power is neglected because it is small.
The net result of the above assumptions yield the following average price impact for the different cases:
- 8 hours a day weekdays only.
- 10 hours a day for all days of the month.
- 24 houroperation all year.
- These will be escalating by at least 8% per year for the next few years.
The key assumptions relating to each option is shown below.
The annual NPVs for the 8 hour per day for weekdays all year is shown in the table below.
The typical breakeven situations are shown in the figure below.
It is thus clear that the all options break even within 21 12 months.
In all three cases the expected NPV over just 5 years exceeds R4 000. This is excellent considering all the environmental advantages and the small investment of only R2 000 required. In cases where there is ample sunlight, the savings will increase further with the daylight harvesting feature.
Why Change
The main drive for the installation of the new more efficient LED Low Bay lights are as follows:
- Savings in electricity:
o Lower usage of the LED light compared with other lights.
o Lower usage on air-conditioning where applied.
- The ability to switch on and off in very short periods compared with Sodium Vapour.
- The backup supply features during power failures / interruptions from utility.
The new LED light with its power supply will use about 25% of the power of the existing light for similar usable light depending on the customers need.
This reduced electricity savings will off-course assist customers in the following respects:
- Lowering their carbon footprint.
- Moving towards achieving the 10% savings requested / required from key (eventually all) customers.
Conclusions
The new Retrofit LED Low Bay light provides a first real alternative to the high light intensity Sodium Vapour lights used extensively in South Africa. It reduces electricity consumption by at least 75% and provides excellent return on investment. The reduction in electricity demand offered by these lights can make a significant impact on the shortage of electricity supply in South Africa and a very significant reduction in impact on global warming.