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Environmental Technology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tent20
Evaluating the impact of LED bulb development on the economic viability of ultraviolet technology for disinfection a
a
a
a
Mohamed A.S. Ibrahim , Jitka MacAdam , Olivier Autin & Bruce Jefferson a
Cranfield Water Science Institute, Cranfield University, Cranfield MK43 0AL, UK Accepted author version posted online: 13 Aug 2013.Published online: 23 Sep 2013.
To cite this article: Mohamed A.S. Ibrahim, Jitka MacAdam, Olivier Autin & Bruce Jefferson (2014) Evaluating the impact of LED bulb development on the economic viability of ultraviolet technology for disinfection, Environmental Technology, 35:4, 400-406, DOI: 10.1080/09593330.2013.829858 To link to this article: http://dx.doi.org/10.1080/09593330.2013.829858
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Environmental Technology, 2014 Vol. 35, No. 4, 400–406, http://dx.doi.org/10.1080/09593330.2013.829858
Evaluating the impact of LED bulb development on the economic viability of ultraviolet technology for disinfection Mohamed A.S. Ibrahim, Jitka MacAdam∗ , Olivier Autin and Bruce Jefferson Cranfield Water Science Institute, Cranfield University, Cranfield MK43 0AL, UK (Received 8 April 2013; accepted 25 July 2013 ) Ultraviolet (UV) technologies have been very successful in disinfection applications due to their ability to inactivate microorganisms without producing harmful disinfection by-products. However, there have been a number of concerns associated with the use of conventional UV systems such as hazardous mercury content, high capital investment and reduced electrical efficiency. These concerns have set limitations for the use of UV processes. The study evaluates the development of light emitting diode (LED) technology as an alternative UV source over the last 5 years, analyses the projections provided by the researchers and UV LED manufacturers and presents the information in a cost model with the aim to predict the timeline at which UV LED will compete with traditional UV low pressure high output technology in the commercial market at full-scale residential and industrial disinfection applications.
Downloaded by [] at 12:25 17 July 2014
Keywords: disinfection; wall plug efficiency; UV light emitting diodes; water treatment; whole life cost
1. Introduction Over the last two decades ultraviolet (UV) processes have gained popularity due to its efficacy in disinfection applications. As previously documented by Crawford et al. [1] and Bowker et al.,[2] germicidal Ultraviolet class C (UVC) irradiation at 254 nm can be applied to inactivate challenging chlorine resistant pathogens in relatively short contact times without producing undesirable disinfection by-products. In addition UV disinfection system has a simple design which usually consists of very few components (UV lamp, reaction chamber and a control box) and it is easy to operate and maintain. Installing or retrofitting a UV system in a new/existing water treatment plant is relatively simple and requires very few modifications to the plant. All these factors have influenced the different regulatory bodies to recommend UV technology for primary disinfection applications.[3,4] Although a capital cost of UV disinfection is likely to be higher than for chlorination, some researchers have suggested that comparing overall costs favours UV over chlorination.[5] However, this might not always be the case, but will depend on the requirements. For domestic or even industrial scenarios, the cost involved would include only the cost of chemical (sodium hypochlorite), a dosing pump and control/monitor with test kits (B. Holden Anglian Water, personal communication). Table 1 highlights the most important technical limitations of traditional UV lamp technologies. Both low pressure high output (LPHO) and
∗ Corresponding
author. Email: j.macadam@cranfield.ac.uk
© 2013 Taylor & Francis
medium pressure (MP) UV lamps commonly used in water and wastewater treatment employ mercury to produce the target germicidal UV irradiation; the wall plug efficiencies and lamp life figures are relatively low and the operating temperatures are significantly high, especially in the case of MP lamps.[3] Those limitations have driven both researchers and manufacturers to develop a safer and more sustainable means of producing UV irradiation.[6,7] Over the last decade, UV light emitting diodes (LEDs) have started to receive greater attention amongst researchers as an alternative UV source owing to a number of advantages over the traditional UV lamps, including the absence of mercury and major glass parts as well as increased operational flexibility and reliability and no need for a warm up period.[7–10] Despite all these advantages, the major challenge remaining is the relatively low power output per device and the low wall plug efficiency1 and as a result the current capital cost of UV LEDs is much higher than conventional UV technologies.[12] However, promising developments lie ahead if we look at the history of visible LEDs. The first commercial visible LED became available in 1968 and 20 years later the development of high brightness LEDs revolutionized the lighting industry. LEDs have become standard components of most electrical appliances, cars and traffic lights. More recently, high brightness LEDs have started to take over traditional lighting systems, in general, lighting and display applications leading to the annual growth rate of the LED market of
Environmental Technology Table 1.
Technical properties of traditional UV lamps.[3]
Parameter Germicidal UV Wavelength (nm) Wall plug efficiency, (%) Lifetime (h) Operating temperature (◦ C) Arc length (cm) Cold start time (min) Warm start time (min)
Table 2.
Downloaded by [] at 12:25 17 July 2014
City of Pittsburgh E.ON, UK Marriott HQ, USA a Based b Based
UV LPHO
MP
Monochromatic at 254 30–35 8000–12,000 60–100 10–150 4–7 2–7
Polychromatic 200–300 10–20 4000–8000 600–900 5–120 1–5 4–10 (including cool down)
LED lighting upgrades with resulting energy savings.
Site
Annual energy reduction (MW)
Annual energy saving* (£1000)
Reference
959 452 860
74a 40b 66a
[15] [16] [17]
on a rate of £0.077 per kWh. on a rate of £0.09 per kWh.
Figure 1. 18,19].
401
The development of visible LEDs [adapted from
42% during the period from 1995 to 2005.[13] Today, visible LEDs offer the commercial market higher luminescence efficiencies which exceed 200 lm W−1 , superior colour targeting efficiencies and extended lifetime between 50,000 and 100,000 h.[13,14] Many industries worldwide are turning to high brightness LEDs for their lighting system upgrades leading to significant energy savings (Table 2). Figure 1 illustrates the development of ‘luminescence efficiency versus cost’ of visible LEDs over the last four decades; a trend known as ‘Haitz’s Law’ is observed whereby every decade the total output per Watt increases by a factor of 20 and the cost per lumen drops by a factor of 10.[13] Thermal control achieved by choosing the right solid substrate in the construction of UV LED is crucial since overheating reduces the LED electrical efficiency as well
as its lifespan.[20] Sahara [21] suggested that the development in UV LED output power is following Moore’s growth model where the output power is nearly doubled every 12–18 months. This potential increase in wall plug efficiency and UV LED life will result in significant savings in plant operation and maintenance costs, especially in remote installation where maintenance and response to system failure can be difficult.[1,21] The reported wall plug efficiencies in 2007 for UV LED emitting between 210 and 340 nm were below 1% and the UV LED life was in the range of 200 h.[14] It is predicted that UV LEDs will follow in the steps of visible LEDs to reach wall plug efficiency as high as 75% with a life exceeding 100,000 h.[1,18] The most recent breakthrough has been reported by SETi,[19] where UV LEDs emitting at 275 nm wavelength reached 8% wall plug efficiency with a device emission power of 9.8 and 30 mW at 20 and 100 mA, respectively. This breakthrough supports the applicability of Moore’s growth model to describe the rate of development of UV LEDs and although the emission power of LEDs remains too low for use in full-scale UV systems, this significant development makes the performance of UV LEDs comparable to standard UV MP lamps which normally operate at around 15% wall plug efficiency.[3,19] The flexibility promised by the compact and robust LED design makes it a perfect fit for a wider range of applications.[14] In 2008, the market size for UV LEDs emitting in the range between 315 and 400 nm was in the region of £75M where medical, detection and analytical applications were dominant.[22] Roussel [23] expected 100% growth in the UV LED market by 2015 since more UV LEDs emitting within the germicidal range will be used in air and water disinfection applications. Pars and Roussel [24] further predicted that by 2016, UV LEDs will contribute to 28.1% of total UV market. LEDs distribution optimization throughout the disinfection medium will ensure increased UV exposure conditions, hence reduce the disinfection system size and provide more opportunities in the surface disinfection.[14] The most unique feature that differentiates UV LEDs from traditional UV technologies is the potential to fine tune the construction of the UV module to emit at preferred wavelengths which could be very useful in targeting specific microorganisms as well as in other specialized photolysis applications.[6,25] The germicidal UVC wavelength for most microorganisms peaks between
Downloaded by [] at 12:25 17 July 2014
402
M.A.S. Ibrahim et al.
260 and 265 nm.[3,7,26] Crawford et al. [1] suggested that in order to achieve the highest inactivation rates UV LEDs should emit at 265 nm. Vilhunen et al. [25] assessed the disinfection efficacy of 269 and 276 nm UV LEDs on Escherichia coli and found that although the shorter wavelength had the stronger inactivation capacity, three to four log inactivation was still achieved by both wavelengths. In a different study, Hamamoto et al. [27] reported three log pathogenic bacteria inactivation using 365 nm UVA LED, but in this case the inactivation was indirect due to the oxidative effect of H2 O2 and ·OH that form at this specific wavelength. Given the rapid development of UV LED bulb technology, it is reasonable to expect that the technology will be economically viable for use within the next 10 years or so. Accordingly, the current paper aims to use the predictions of bulb development to consider the timeline when LED becomes economically comparable to traditional mercury-based lamps. This is demonstrated through two potential case studies applications, including small- and medium-scale disinfection systems which represent the current market for conventional UV technology. LPHO lamps were selected for this study as they produce monochromatic UVC irradiation at 254 nm which makes the comparison with monochromatic UV LED more relevant. Also low pressure lamps are already few steps ahead in terms of efficiency when compared with MP lamps and the main aim of this study was to establish whether UV LEDs could further improve this efficiency.
2. Methodology 2.1. Model description The model compares the new UV LED technology with traditional UV LPHO amalgam lamps. Two cases were selected as the basis of comparison. The first case is a residential scale UV disinfection application at a flow rate below 2 m3 h−1 . This flow rate has been estimated based on average water usage rate of 25–30 lmin−1 in a property where the shower, the wash basin tap, the washer and the flush are in service simultaneously.[28] The second case is assessing the use of UV LEDs in an average industrial scale UV disinfection application.[29] The third case is a commercial evaluation of UV LEDs for use in a small commercial UV/TiO2 application at a flow rate
Environmental Technology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tent20
Evaluating the impact of LED bulb development on the economic viability of ultraviolet technology for disinfection a
a
a
a
Mohamed A.S. Ibrahim , Jitka MacAdam , Olivier Autin & Bruce Jefferson a
Cranfield Water Science Institute, Cranfield University, Cranfield MK43 0AL, UK Accepted author version posted online: 13 Aug 2013.Published online: 23 Sep 2013.
To cite this article: Mohamed A.S. Ibrahim, Jitka MacAdam, Olivier Autin & Bruce Jefferson (2014) Evaluating the impact of LED bulb development on the economic viability of ultraviolet technology for disinfection, Environmental Technology, 35:4, 400-406, DOI: 10.1080/09593330.2013.829858 To link to this article: http://dx.doi.org/10.1080/09593330.2013.829858
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Environmental Technology, 2014 Vol. 35, No. 4, 400–406, http://dx.doi.org/10.1080/09593330.2013.829858
Evaluating the impact of LED bulb development on the economic viability of ultraviolet technology for disinfection Mohamed A.S. Ibrahim, Jitka MacAdam∗ , Olivier Autin and Bruce Jefferson Cranfield Water Science Institute, Cranfield University, Cranfield MK43 0AL, UK (Received 8 April 2013; accepted 25 July 2013 ) Ultraviolet (UV) technologies have been very successful in disinfection applications due to their ability to inactivate microorganisms without producing harmful disinfection by-products. However, there have been a number of concerns associated with the use of conventional UV systems such as hazardous mercury content, high capital investment and reduced electrical efficiency. These concerns have set limitations for the use of UV processes. The study evaluates the development of light emitting diode (LED) technology as an alternative UV source over the last 5 years, analyses the projections provided by the researchers and UV LED manufacturers and presents the information in a cost model with the aim to predict the timeline at which UV LED will compete with traditional UV low pressure high output technology in the commercial market at full-scale residential and industrial disinfection applications.
Downloaded by [] at 12:25 17 July 2014
Keywords: disinfection; wall plug efficiency; UV light emitting diodes; water treatment; whole life cost
1. Introduction Over the last two decades ultraviolet (UV) processes have gained popularity due to its efficacy in disinfection applications. As previously documented by Crawford et al. [1] and Bowker et al.,[2] germicidal Ultraviolet class C (UVC) irradiation at 254 nm can be applied to inactivate challenging chlorine resistant pathogens in relatively short contact times without producing undesirable disinfection by-products. In addition UV disinfection system has a simple design which usually consists of very few components (UV lamp, reaction chamber and a control box) and it is easy to operate and maintain. Installing or retrofitting a UV system in a new/existing water treatment plant is relatively simple and requires very few modifications to the plant. All these factors have influenced the different regulatory bodies to recommend UV technology for primary disinfection applications.[3,4] Although a capital cost of UV disinfection is likely to be higher than for chlorination, some researchers have suggested that comparing overall costs favours UV over chlorination.[5] However, this might not always be the case, but will depend on the requirements. For domestic or even industrial scenarios, the cost involved would include only the cost of chemical (sodium hypochlorite), a dosing pump and control/monitor with test kits (B. Holden Anglian Water, personal communication). Table 1 highlights the most important technical limitations of traditional UV lamp technologies. Both low pressure high output (LPHO) and
∗ Corresponding
author. Email: j.macadam@cranfield.ac.uk
© 2013 Taylor & Francis
medium pressure (MP) UV lamps commonly used in water and wastewater treatment employ mercury to produce the target germicidal UV irradiation; the wall plug efficiencies and lamp life figures are relatively low and the operating temperatures are significantly high, especially in the case of MP lamps.[3] Those limitations have driven both researchers and manufacturers to develop a safer and more sustainable means of producing UV irradiation.[6,7] Over the last decade, UV light emitting diodes (LEDs) have started to receive greater attention amongst researchers as an alternative UV source owing to a number of advantages over the traditional UV lamps, including the absence of mercury and major glass parts as well as increased operational flexibility and reliability and no need for a warm up period.[7–10] Despite all these advantages, the major challenge remaining is the relatively low power output per device and the low wall plug efficiency1 and as a result the current capital cost of UV LEDs is much higher than conventional UV technologies.[12] However, promising developments lie ahead if we look at the history of visible LEDs. The first commercial visible LED became available in 1968 and 20 years later the development of high brightness LEDs revolutionized the lighting industry. LEDs have become standard components of most electrical appliances, cars and traffic lights. More recently, high brightness LEDs have started to take over traditional lighting systems, in general, lighting and display applications leading to the annual growth rate of the LED market of
Environmental Technology Table 1.
Technical properties of traditional UV lamps.[3]
Parameter Germicidal UV Wavelength (nm) Wall plug efficiency, (%) Lifetime (h) Operating temperature (◦ C) Arc length (cm) Cold start time (min) Warm start time (min)
Table 2.
Downloaded by [] at 12:25 17 July 2014
City of Pittsburgh E.ON, UK Marriott HQ, USA a Based b Based
UV LPHO
MP
Monochromatic at 254 30–35 8000–12,000 60–100 10–150 4–7 2–7
Polychromatic 200–300 10–20 4000–8000 600–900 5–120 1–5 4–10 (including cool down)
LED lighting upgrades with resulting energy savings.
Site
Annual energy reduction (MW)
Annual energy saving* (£1000)
Reference
959 452 860
74a 40b 66a
[15] [16] [17]
on a rate of £0.077 per kWh. on a rate of £0.09 per kWh.
Figure 1. 18,19].
401
The development of visible LEDs [adapted from
42% during the period from 1995 to 2005.[13] Today, visible LEDs offer the commercial market higher luminescence efficiencies which exceed 200 lm W−1 , superior colour targeting efficiencies and extended lifetime between 50,000 and 100,000 h.[13,14] Many industries worldwide are turning to high brightness LEDs for their lighting system upgrades leading to significant energy savings (Table 2). Figure 1 illustrates the development of ‘luminescence efficiency versus cost’ of visible LEDs over the last four decades; a trend known as ‘Haitz’s Law’ is observed whereby every decade the total output per Watt increases by a factor of 20 and the cost per lumen drops by a factor of 10.[13] Thermal control achieved by choosing the right solid substrate in the construction of UV LED is crucial since overheating reduces the LED electrical efficiency as well
as its lifespan.[20] Sahara [21] suggested that the development in UV LED output power is following Moore’s growth model where the output power is nearly doubled every 12–18 months. This potential increase in wall plug efficiency and UV LED life will result in significant savings in plant operation and maintenance costs, especially in remote installation where maintenance and response to system failure can be difficult.[1,21] The reported wall plug efficiencies in 2007 for UV LED emitting between 210 and 340 nm were below 1% and the UV LED life was in the range of 200 h.[14] It is predicted that UV LEDs will follow in the steps of visible LEDs to reach wall plug efficiency as high as 75% with a life exceeding 100,000 h.[1,18] The most recent breakthrough has been reported by SETi,[19] where UV LEDs emitting at 275 nm wavelength reached 8% wall plug efficiency with a device emission power of 9.8 and 30 mW at 20 and 100 mA, respectively. This breakthrough supports the applicability of Moore’s growth model to describe the rate of development of UV LEDs and although the emission power of LEDs remains too low for use in full-scale UV systems, this significant development makes the performance of UV LEDs comparable to standard UV MP lamps which normally operate at around 15% wall plug efficiency.[3,19] The flexibility promised by the compact and robust LED design makes it a perfect fit for a wider range of applications.[14] In 2008, the market size for UV LEDs emitting in the range between 315 and 400 nm was in the region of £75M where medical, detection and analytical applications were dominant.[22] Roussel [23] expected 100% growth in the UV LED market by 2015 since more UV LEDs emitting within the germicidal range will be used in air and water disinfection applications. Pars and Roussel [24] further predicted that by 2016, UV LEDs will contribute to 28.1% of total UV market. LEDs distribution optimization throughout the disinfection medium will ensure increased UV exposure conditions, hence reduce the disinfection system size and provide more opportunities in the surface disinfection.[14] The most unique feature that differentiates UV LEDs from traditional UV technologies is the potential to fine tune the construction of the UV module to emit at preferred wavelengths which could be very useful in targeting specific microorganisms as well as in other specialized photolysis applications.[6,25] The germicidal UVC wavelength for most microorganisms peaks between
Downloaded by [] at 12:25 17 July 2014
402
M.A.S. Ibrahim et al.
260 and 265 nm.[3,7,26] Crawford et al. [1] suggested that in order to achieve the highest inactivation rates UV LEDs should emit at 265 nm. Vilhunen et al. [25] assessed the disinfection efficacy of 269 and 276 nm UV LEDs on Escherichia coli and found that although the shorter wavelength had the stronger inactivation capacity, three to four log inactivation was still achieved by both wavelengths. In a different study, Hamamoto et al. [27] reported three log pathogenic bacteria inactivation using 365 nm UVA LED, but in this case the inactivation was indirect due to the oxidative effect of H2 O2 and ·OH that form at this specific wavelength. Given the rapid development of UV LED bulb technology, it is reasonable to expect that the technology will be economically viable for use within the next 10 years or so. Accordingly, the current paper aims to use the predictions of bulb development to consider the timeline when LED becomes economically comparable to traditional mercury-based lamps. This is demonstrated through two potential case studies applications, including small- and medium-scale disinfection systems which represent the current market for conventional UV technology. LPHO lamps were selected for this study as they produce monochromatic UVC irradiation at 254 nm which makes the comparison with monochromatic UV LED more relevant. Also low pressure lamps are already few steps ahead in terms of efficiency when compared with MP lamps and the main aim of this study was to establish whether UV LEDs could further improve this efficiency.
2. Methodology 2.1. Model description The model compares the new UV LED technology with traditional UV LPHO amalgam lamps. Two cases were selected as the basis of comparison. The first case is a residential scale UV disinfection application at a flow rate below 2 m3 h−1 . This flow rate has been estimated based on average water usage rate of 25–30 lmin−1 in a property where the shower, the wash basin tap, the washer and the flush are in service simultaneously.[28] The second case is assessing the use of UV LEDs in an average industrial scale UV disinfection application.[29] The third case is a commercial evaluation of UV LEDs for use in a small commercial UV/TiO2 application at a flow rate
