HomeEconomics

 

Operating Data and the Economics of Different Lamps*

Assume: 4100 hours of use per year (average night time hours, dusk to dawn) 8c per KWH (typical average cost per kilowatt-hour, the power rate)

Low Pressure Sodium

180W

135W

90W

55W

35W

18W

Initial Lumens

33000

22500

13500

8000

4800

1800

Mean Lumens

33000

22500

13500

8000

4800

1800

Lamp Wattage

180

135

90

55

35

18

Circuit Wattage

220

180

125

80

60

30

Initial Lum/watt

150

125

108

100

80

60

Mean Lum/watt

150

125

108

100

80

60

Annual KWH Use

902

738

513

328

246

123

High Pressure Sodium

400W

250W

200W

150W

100W

70W

50W

35W

Initial Lumens

50000

28500

22000

16000

9500

6300

4000

2250

Mean Lumens

45000

25700

19800

14400

8550

5670

3600

2025

Lamp Wattage

400

250

200

150

100

70

50

35

Circuit Wattage

465

294

246

193

130

88

66

46

Initial Lum/watt

108

97

89

83

73

72

61

49

Mean Lum/watt

97

87

80

75

66

64

55

44

Annual KWH Use

1907

1205

1009

791

533

361

271

189


Metal Halide

1000W

400W

250W

175W

150W

100W

70W

50W

32W

Initial Lumens

110000

36000

20500

16600

13000

9000

5500

3500

2500

Mean Lumens

88000

28800

12700

10350

8700

6400

4000

2500

1900

Lamp Wattage

1000

400

250

175

150

100

70

50

32

Circuit Wattage

1070

456

295

215

184

115

88

62

43

Initial Lum/watt

103

79

69

77

71

78

63

56

58

Mean Lum/watt

82

63

58

48

47

56

45

40

44

Annual KWH Use

4387

1870

1210

882

754

472

361

254

176

Mercury Vapor and Incandescent *

1000W

700W

400W

250W

175W

100W

150W*

100W*

Initial Lumens

55000

36400

20500

11850

7850

4100

2850

1710

Mean Lumens

46200

29850

18570

10540

7140

3230

2850

1710

Lamp Wattage

1000

700

400

250

175

100

150

100

Circuit Wattage

1090

765

455

285

205

135

150

100

Initial Lum/watt

50

48

45

42

38

30

19

17

Mean Lum/watt

42

39

41

37

35

24

19

17

Annual KWH Use

4469

3137

1866

1169

841

554

615

410


http://www.solarstreetlights.net/images/spacer.giflined up at nearly equal lumen output, to show the relative energy & cost savings.

Definitions and Discussion Points

  1. The numbers in the preceding table are approximate. Lumen output depends on the bulb manufacturer and operating conditions. Circuit wattage depends on the ballast manufacturer.
  2. The numbers in the preceding table are for clear bulbs. Diffuse coated ("frosted") bulbs are available for most lamp types, and these will have a somewhat lower lumen output. Always use diffuse coated bulbs when the light source is directly visible from normal viewing angles to reduce glare. Use clear bulbs in fully shielded fixtures or when the fixture lens is diffuse or translucent.
  3. We use 4100 hours as typical of the annual operating time of a street light or any other fixture controlled by a photosensor that comes on at dusk and goes off at dawn. 4100 / 365 = 11.23 hours per night. A sampling of several cities indicates that 4100 hours is typical of the hours that their street lighting system is operating each year.
  4. The U.S.A. national average for electrical utility rates is close to 8 cents per kilowatt-hour. One can and should use a rate that is representative of local utility rates. The range is from a low of about 4 cents (wouldn't that be nice in your own area?!) to a high of 18 cents or more. Any spreadsheet program makes such comparisons easy. One should allow for future rate changes, which are most generally upwards.
  5. Kilowatt-hour (KWH) is a measure of the amount of energy used. Kilowatts measure power. A kilowatt is 1000 watts. A KWH is one kilowatt of power used for a duration of one hour.
  6. Initial lumens is a measure of how much light the lamp is emitting near the beginning of its life. Most high-efficiency light sources (except LPS) decline in light output with time. LPS has a lifetime of about four years, and HPS about five, while mercury vapor almost never "burns out"; it just keeps getting fainter and fainter. You can estimate the relative effects by looking at the row titled "mean lumens". This is the average output of the lamp during its usable lifetime.
  7. Mean lumens is a measure of how much light the lamp is putting out after about two or three years of usage. We a ssume a typical lifetime for the lamp, either due to burnout of the lamp or to group replacement. Many communities replace lamps after a specified interval, so as to minimize any outages due to lamp burnout. The cost of a lamp is much le ss than the cost of an accident or a lawsuit due to a lamp having burned out. The i ssue of half life and replacement strategy is complicated, and few agree on all aspects.
  8. Circuit wattage takes into account the other energy uses besides that of the lamp. The major energy lo ss occurs in the ballast, a unit needed to start and operate the lamp under conditions that it is designed for. There are many different kinds of ballasts, and what is good for one lamp or wattage is usually not good for another. LPS should be used with a ballast designed for efficient LPS use, for example. The ratio of lamp wattage to circuit wattage is not a constant, even for the same type of lamp. See the table for examples.
  9. All these entries have been taken from either lamp manufacturers' catalogs or actual operating experience in different communities. The figures given in the table are sort of an average of all that, and as such should be typical of what is being used in any specific location.
  10. Lumens/watt is a measure of operating efficiency: total amount of light from the lamp per power used.
  11. Annual KWH use is also a measure of operating efficiency, as it tells how much energy is used each year. Naturally, don't use more light than one needs (more light is not always better!) as that uses more energy.
  12. Typical wattages for major highways or streets would be 180 or 135 or 90 watt LPS, or 400 or 250 or 150 watt HPS, or 1000 or 400 or 250 watt Mercury Vapor. Typical values for residential streets might be 90 or 55 watt LPS, or 150 or 100 or 70 watt HPS, or 175 watt mercury vapor. Typical home security lighting might be 35 or 18 watt LPS, 70 or 50 or 35 watt HPS; please don't use mercury vapor, as it is not very efficient. Always use full-cutoff fixtures for all applications!
  13. Annual operating cost is another measure of operating efficiency, of course. It tells how much one must pay for energy usage in order to operate one given fixture for one year. In some cases, the cost of the fixture is le ss than the annual operating cost! Payback times when replacing inefficient fixtures with energy efficient fixtures can be very short. Quite often, a one-step-lower-wattage bulb (and ballast) can be used, resulting in lower operating costs.
  14. Of course, there are other costs for any given installation. Maintenance, lamp replacement, replacements due to accidents and breakages, depreciation, whatever. Generally these are "a wash" as all systems have similar costs.
  15. As you look at the table, be sure to notice the bulb wattages that give similar light output for different types of lamps. For example, 35 watt LPS, 70 watt HPS, 100 watt Metal Halide, or 175 watt Mercury Vapor give similar mean lumen outputs. Such comparisons can offer guidance as to the tremendous savings that can be obtained with more efficient light sources. Keep in mind, though, that an inefficient source used infrequently uses le ss energy than a highly efficient source that burns from dusk to dawn, 365 nights a year. Thus, an incandescent light that is activated by an outdoor occupancy sensor will usually have a lower operating cost than a dusk-to dawn HPS security light, for example.

There are other overall considerations as well. For example, not all fixtures are equally efficient at getting the light produced by the lamp out of the fixture and onto the area needing the light. One should always use efficient fixtures as well as efficient lamps. Many old fixtures are not efficient, as they were designed at a time when energy was cheap and efficiency was low on the priority list. For example, "globes" throw more than half their light output upwards. Today, there is no excuse to use any such inefficient fixtures. Please help stamp them out. Use efficient full-cutoff fixtures for all applications. Install as recommended, of course, to insure that the light output is used, not wasted producing glare and uplight.

Solar LED Street Light Features

• Highest efficient mono-crystalline or poly-crystalline solar modules. which could be used for more than 20 years.
• No mainttence,waterproof & Gel battery. 1-2 years lifetime longer than Lead-Acid battery.
• Solar system controller: light open&close control or time control,over charges and over discharge protection. The contoller has new function to contorl the lamp power in partitioned,that means the lamp power will be down automatically if you want to use lower power after midinight to save energy.
• Lumination:10-12hrs/day.lasting 4-6days under rainy/cloudy day.
• Zinc-Plated steel pole and powder coating to colour of your choice,with the whole kit of stainless steel fasteners.
• Lamp:LED lamp,assembled by 1W LED
• Environmental temperature:-40
-50
• Wind resistance:50m/s

Solar LED Street Light Specifications

LED Lamp: DC12V/24V

Lamp powerW

21W

28W

35W

42W

56W

Solar Module

12V/75W

12V/100W

24V/120W

24V/150W

24V/200W

Battery

12V/65AH

12V/70AH

24V/65AH

24V/70AH

24V/80AH

Lumens

1700LM

2380LM

2975LM

3570LM

4760LM

Lux

10LUX

12LUX

13LUX

14LUX

16LUX

Lamp Height

5M

6M

7M

8M

9M

Pole Distance

15M

20M

25M

25M

30M

Lamp life

100000hrs

100000hrs

100000hrs

100000hrs

100000hrs

How to choose a solar battery ?

The battery or battery bank is one of the most important parts of a solar power system. So It is necessary to choose the right battery for your solar home system, the following two points should be taken into account when your purchase battery:

•  DOD(depth of discharge)

Deep cycle batteries are specifically designed to be discharged anywhere from 50-80% without harm. If the battery is a shallow cycle or automotive type it will not function correctly in the system. The deep cycle batteries are designed to discharge and recharge or cycle day after day without damage for years.

•  Battery Types

The most common type of battery used in a solar system is a sealed or flooded battery. They are generally used because they have a low initial cost and are readily available.

A sealed battery never needs water added nor does it need an equalization charge. The benefits of this battery are the battery can be mounted in any position and are easy to transport; The one downside is that they need to be monitored closely as to not overcharge.

A flooded battery also needs close attention. The water level needs to be checked often and filled. You will also need to perform an equalization charge, which is a long steady controlled overcharge. This removes sulfation from the battery plates. While this restores the battery's capacity, it can lessen the life of the batteries by warping the plates.

Recommended battery types for renewable energy applications are: Flooded Lead Acid (FLA), Sealed Gel Cells (GEL), and Sealed Absorbed Glass Mat (AGM).

Battery Bank Sizing

Before tackling the calculations, start by identifying a few key pieces of information:

  • Watt-hours of electricity usage per day
  • Number of Days of Autonomy
  • Depth of Discharge limit
  • System Voltage
  • Ambient temperature at battery bank

Once you've pinpointed all these variables, it's time to calculate the size of your battery bank! Let's go through the steps below, using the following example system: 1. A system load of 500 Watt-hours per day; 2. Three Days of Autonomy (back up) needed; 3. Planned Depth of Discharge (DoD): 75%; 4. Battery bank ambient average low temperature 60° F.; 5. A 24V system

Assume: 4100 hours of use per year (average night time hours, dusk to dawn) 8c per KWH (typical average cost per kilowatt-hour, the power rate)

Low Pressure Sodium

180W

135W

90W

55W

35W

18W

Initial Lumens

33000

22500

13500

8000

4800

1800

Mean Lumens

33000

22500

13500

8000

4800

1800

Lamp Wattage

180

135

90

55

35

18

Circuit Wattage

220

180

125

80

60

30

Initial Lum/watt

150

125

108

100

80

60

Mean Lum/watt

150

125

108

100

80

60

Annual KWH Use

902

738

513

328

246

123


High Pressure Sodium

400W

250W

200W

150W

100W

70W

50W

35W

Initial Lumens

50000

28500

22000

16000

9500

6300

4000

2250

Mean Lumens

45000

25700

19800

14400

8550

5670

3600

2025

Lamp Wattage

400

250

200

150

100

70

50

35

Circuit Wattage

465

294

246

193

130

88

66

46

Initial Lum/watt

108

97

89

83

73

72

61

49

Mean Lum/watt

97

87

80

75

66

64

55

44

Annual KWH Use

1907

1205

1009

791

533

361

271

189


Metal Halide

1000W

400W

250W

175W

150W

100W

70W

50W

32W

Initial Lumens

110000

36000

20500

16600

13000

9000

5500

3500

2500

Mean Lumens

88000

28800

12700

10350

8700

6400

4000

2500

1900

Lamp Wattage

1000

400

250

175

150

100

70

50

32

Circuit Wattage

1070

456

295

215

184

115

88

62

43

Initial Lum/watt

103

79

69

77

71

78

63

56

58

Mean Lum/watt

82

63

58

48

47

56

45

40

44

Annual KWH Use

4387

1870

1210

882

754

472

361

254

176

Annual per Cost

$350.96

$149.60

$96.80

$70.56

$60.32

$37.76

$28.88

$20.32

$14.08

Mercury Vapor and Incandescent *

1000W

700W

400W

250W

175W

100W

150W*

100W*

Initial Lumens

55000

36400

20500

11850

7850

4100

2850

1710

Mean Lumens

46200

29850

18570

10540

7140

3230

2850

1710

Lamp Wattage

1000

700

400

250

175

100

150

100

Circuit Wattage

1090

765

455

285

205

135

150

100

Initial Lum/watt

50

48

45

42

38

30

19

17

Mean Lum/watt

42

39

41

37

35

24

19

17

Annual KWH Use

4469

3137

1866

1169

841

554

615

410


http://www.solarstreetlights.net/images/spacer.giflined up at nearly equal lumen output, to show the relative energy & cost savings.

Definitions and Discussion Points

  1. The numbers in the preceding table are approximate. Lumen output depends on the bulb manufacturer and operating conditions. Circuit wattage depends on the ballast manufacturer.
  2. The numbers in the preceding table are for clear bulbs. Diffuse coated ("frosted") bulbs are available for most lamp types, and these will have a somewhat lower lumen output. Always use diffuse coated bulbs when the light source is directly visible from normal viewing angles to reduce glare. Use clear bulbs in fully shielded fixtures or when the fixture lens is diffuse or translucent.
  3. We use 4100 hours as typical of the annual operating time of a street light or any other fixture controlled by a photosensor that comes on at dusk and goes off at dawn. 4100 / 365 = 11.23 hours per night. A sampling of several cities indicates that 4100 hours is typical of the hours that their street lighting system is operating each year.
  4. The U.S.A. national average for electrical utility rates is close to 8 cents per kilowatt-hour. One can and should use a rate that is representative of local utility rates. The range is from a low of about 4 cents (wouldn't that be nice in your own area?!) to a high of 18 cents or more. Any spreadsheet program makes such comparisons easy. One should allow for future rate changes, which are most generally upwards.
  5. Kilowatt-hour (KWH) is a measure of the amount of energy used. Kilowatts measure power. A kilowatt is 1000 watts. A KWH is one kilowatt of power used for a duration of one hour.
  6. Initial lumens is a measure of how much light the lamp is emitting near the beginning of its life. Most high-efficiency light sources (except LPS) decline in light output with time. LPS has a lifetime of about four years, and HPS about five, while mercury vapor almost never "burns out"; it just keeps getting fainter and fainter. You can estimate the relative effects by looking at the row titled "mean lumens". This is the average output of the lamp during its usable lifetime.
  7. Mean lumens is a measure of how much light the lamp is putting out after about two or three years of usage. We a ssume a typical lifetime for the lamp, either due to burnout of the lamp or to group replacement. Many communities replace lamps after a specified interval, so as to minimize any outages due to lamp burnout. The cost of a lamp is much le ss than the cost of an accident or a lawsuit due to a lamp having burned out. The i ssue of half life and replacement strategy is complicated, and few agree on all aspects.
  8. Circuit wattage takes into account the other energy uses besides that of the lamp. The major energy lo ss occurs in the ballast, a unit needed to start and operate the lamp under conditions that it is designed for. There are many different kinds of ballasts, and what is good for one lamp or wattage is usually not good for another. LPS should be used with a ballast designed for efficient LPS use, for example. The ratio of lamp wattage to circuit wattage is not a constant, even for the same type of lamp. See the table for examples.
  9. All these entries have been taken from either lamp manufacturers' catalogs or actual operating experience in different communities. The figures given in the table are sort of an average of all that, and as such should be typical of what is being used in any specific location.
  10. Lumens/watt is a measure of operating efficiency: total amount of light from the lamp per power used.
  11. Annual KWH use is also a measure of operating efficiency, as it tells how much energy is used each year. Naturally, don't use more light than one needs (more light is not always better!) as that uses more energy.
  12. Typical wattages for major highways or streets would be 180 or 135 or 90 watt LPS, or 400 or 250 or 150 watt HPS, or 1000 or 400 or 250 watt Mercury Vapor. Typical values for residential streets might be 90 or 55 watt LPS, or 150 or 100 or 70 watt HPS, or 175 watt mercury vapor. Typical home security lighting might be 35 or 18 watt LPS, 70 or 50 or 35 watt HPS; please don't use mercury vapor, as it is not very efficient. Always use full-cutoff fixtures for all applications!
  13. Annual operating cost is another measure of operating efficiency, of course. It tells how much one must pay for energy usage in order to operate one given fixture for one year. In some cases, the cost of the fixture is le ss than the annual operating cost! Payback times when replacing inefficient fixtures with energy efficient fixtures can be very short. Quite often, a one-step-lower-wattage bulb (and ballast) can be used, resulting in lower operating costs.
  14. Of course, there are other costs for any given installation. Maintenance, lamp replacement, replacements due to accidents and breakages, depreciation, whatever. Generally these are "a wash" as all systems have similar costs.
  15. As you look at the table, be sure to notice the bulb wattages that give similar light output for different types of lamps. For example, 35 watt LPS, 70 watt HPS, 100 watt Metal Halide, or 175 watt Mercury Vapor give similar mean lumen outputs. Such comparisons can offer guidance as to the tremendous savings that can be obtained with more efficient light sources. Keep in mind, though, that an inefficient source used infrequently uses le ss energy than a highly efficient source that burns from dusk to dawn, 365 nights a year. Thus, an incandescent light that is activated by an outdoor occupancy sensor will usually have a lower operating cost than a dusk-to dawn HPS security light, for example.

There are other overall considerations as well. For example, not all fixtures are equally efficient at getting the light produced by the lamp out of the fixture and onto the area needing the light. One should always use efficient fixtures as well as efficient lamps. Many old fixtures are not efficient, as they were designed at a time when energy was cheap and efficiency was low on the priority list. For example, "globes" throw more than half their light output upwards. Today, there is no excuse to use any such inefficient fixtures. Please help stamp them out. Use efficient full-cutoff fixtures for all applications. Install as recommended, of course, to insure that the light output is used, not wasted producing glare and uplight.

Solar LED Street Light Features

• Highest efficient mono-crystalline or poly-crystalline solar modules. which could be used for more than 20 years.
• No mainttence,waterproof & Gel battery. 1-2 years lifetime longer than Lead-Acid battery.
• Solar system controller: light open&close control or time control,over charges and over discharge protection. The contoller has new function to contorl the lamp power in partitioned,that means the lamp power will be down automatically if you want to use lower power after midinight to save energy.
• Lumination:10-12hrs/day.lasting 4-6days under rainy/cloudy day.
• Zinc-Plated steel pole and powder coating to colour of your choice,with the whole kit of stainless steel fasteners.
• Lamp:LED lamp,assembled by 1W LED
• Environmental temperature:-40
-50
• Wind resistance:50m/s

Solar LED Street Light Specifications

LED Lamp: DC12V/24V

Lamp powerW

21W

28W

35W

42W

56W

Solar Module

12V/75W

12V/100W

24V/120W

24V/150W

24V/200W

Battery

12V/65AH

12V/70AH

24V/65AH

24V/70AH

24V/80AH

Lumens

1700LM

2380LM

2975LM

3570LM

4760LM

Lux

10LUX

12LUX

13LUX

14LUX

16LUX

Lamp Height

5M

6M

7M

8M

9M

Pole Distance

15M

20M

25M

25M

30M

Lamp life

100000hrs

100000hrs

100000hrs

100000hrs

100000hrs

How to choose a solar battery ?

The battery or battery bank is one of the most important parts of a solar power system. So It is necessary to choose the right battery for your solar home system, the following two points should be taken into account when your purchase battery:

•  DOD(depth of discharge)

Deep cycle batteries are specifically designed to be discharged anywhere from 50-80% without harm. If the battery is a shallow cycle or automotive type it will not function correctly in the system. The deep cycle batteries are designed to discharge and recharge or cycle day after day without damage for years.

•  Battery Types

The most common type of battery used in a solar system is a sealed or flooded battery. They are generally used because they have a low initial cost and are readily available.

A sealed battery never needs water added nor does it need an equalization charge. The benefits of this battery are the battery can be mounted in any position and are easy to transport; The one downside is that they need to be monitored closely as to not overcharge.

A flooded battery also needs close attention. The water level needs to be checked often and filled. You will also need to perform an equalization charge, which is a long steady controlled overcharge. This removes sulfation from the battery plates. While this restores the battery's capacity, it can lessen the life of the batteries by warping the plates.

Recommended battery types for renewable energy applications are: Flooded Lead Acid (FLA), Sealed Gel Cells (GEL), and Sealed Absorbed Glass Mat (AGM).

Battery Bank Sizing

Before tackling the calculations, start by identifying a few key pieces of information:

  • Watt-hours of electricity usage per day
  • Number of Days of Autonomy
  • Depth of Discharge limit
  • System Voltage
  • Ambient temperature at battery bank

Once you've pinpointed all these variables, it's time to calculate the size of your battery bank! Let's go through the steps below, using the following example system: 1. A system load of 500 Watt-hours per day; 2. Three Days of Autonomy (back up) needed; 3. Planned Depth of Discharge (DoD): 75%; 4. Battery bank ambient average low temperature 60° F.; 5. A 24V system