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Cogeneration in the Hawaiian sugar industry
Bioresource Technology 35 ( 1991 ) 231-237
Review Article Cogeneration in the Hawaiian Sugar Industry C. M. Kinoshita Hawaii Natural Energy Institute, University of Hawaii at Manoa, 2540 Dole Street, Honolulu, Hawaii 96822, USA ¢Received 13 February 1990; accepted 28 March 1990)
Abstract For nearly a century the Hawaiian sugar industry has produced most of the steam and electricity needed to process sugarcane and to power its factories and irrigation pumps. This use of bagasse (the fibrous by-product of milled sugarcane), cane leaves and tops has made the Hawaiian sugar industr 3, among the most efficient in the world in converting biomass into electricity -- in comparison with typical worldwide cane-to-electricity conversion productivities of - 10 k w h per tonne of cane, Hawaiian sugar factories today generate, on average, about 60 k w h per tonne of cane and, in some factories, 100 k w h or more. Plantations in Hawaii produce about 800 million k w h annually, and, after satisfying virtually all of their internal power requirements, export roughly 400 million k Wh to public utility companies. Key words: Cogeneration, bagasse, sugarcane, electricity.
INTRODUCTION The generation and use of steam and electricity by the Hawaiian sugar industry has had a long and rather unique history. Milestones in steam and electricity generation and disposition during the past 150 years are summarized in Fig. 1 and are discussed below. Bagasse has been the primary fuel for the industry since the earliest Hawaiian sugar factories. However, its use prior to 1840 was largely restricted to sugar-boiling plants which, at the
time, consisted of a train of uncovered pots over open wood and bagasse fires to concentrate cane juice for sugar crystallization. In 1840 steam coils replaced the open fire for concentrating juice, and, in 1861, the industry made a major advance by introducing a vacuum pan to boil sugar at the Kaupakuea Plantation on the island of Hawaii. During the earliest years of the Hawaiian sugar industry, bagasse often contained so much moisture that it had to be sun-dried prior to firing, or, if burned immediately after milling, had to be supplemented with substantial amounts of wood or coal. However, as milling practices and equipment improved so did the quality of bagasse as a fuel, to the extent that by the late 1800s bagasse was being conveyed directly from the cane mills and burned in boilers without supplemental fueling. Although bagasse has played a major role in sugar processing since the Hawaiian sugar industry was in its infancy, it was not used to provide mechanical power until the mid-1800s. Prior to 1850 most Hawaiian sugar factories used animals or flowing water to drive their mills. Steam was first adopted to power mills at the Haiku Plantation on the island of Maui in 1858 (Thrum, 1875). This practice gained favor rapidly -- by 1861 nearly one-half of the factories in the industry were relying on reciprocating steam engines to power their mills. Steam engines continued to be the major mode of power transformation in milling cane in Hawaiian sugar factories until 1900 when the first steam turbine was installed at the Ewa Plantation on Oahu. Today, virtually every sugar factory has abandoned the reciprocating steam engine in favor of the steam turbine for large mechanical power applications.
231 Bioresource Technology 0960-8524/91/S03.50 © 1991 Elsevier Science Publishers Ltd, England. Printed in Great Britain
232
C. M. Kinoshita
Steam coils first used to concentrate cane juice Steam adopted for motive power Vacuum~ans introduced • Electricity first used as major power source ~, First steam turbine drive installed • Molasses mixed with bagasse for fuel Fuel oil first used for pumping First large turbogenerator unit installed Maui Electric Co. installs its first unit First relatively high pressure boiler installed • Kauai Electric Co. installs its first unit First major firm-power agreement established Act 102 becomes Hawaii law 9 . Passage of PURPA Last multiple small boiler system replaced • First three-party cogeneration arrangement established • Passage of Title 6, Chapter 74
1800
I
I
I
I
I
I
I
I
I
I
1820
1840
1860
1880
1900
1920
1940
1960
1980
2000
Year
Fig. 1. Majormilestones -- cogeneration in the Hawaiian sugar industry.
120
ELECTRIFICATION OF THE INDUSTRY
10
1 /
.e- BoilerCapacity
o-pc_
o
"E
=-~ 100
In the early 1900s, both field (primarily irrigation) and factory operations on plantations were powered mainly by steam, except where electricity from hydroelectric sources was available. Although there are references to numerous small electrical generating units in Hawaiian sugar factories shortly after the turn of the century, the emergence of bagasse-generated electricity as a significant form of power came in 1916 when the first large sugar factory power plant in Hawaii, consisting of two 750 kW turbo-generators, was built at Hawaiian Commercial and Sugar Company on the island of Maui (Anon., 1919). The introduction of the large factory power plant intensified electrification in the sugar industry and, in turn, the evolution of electrification spurred expansion of the sugar factory power plant. As electrification intensified and the demand for electricity expanded, so did the industry's steam and power generation facilities. The need for greater energy efficiency and less labor input (which was becoming among the most expensive in the world) to operate and maintain cogeneration systems forced the industry to consolidate steam and power generating equipment into larger and more efficient units (e.g., see Figs 2 and 3). The process of consolidation of cogeneration units culminated in 1980 when nine low-pressure boilers and three turbo-generators were replaced by one fairly high pressure boiler servicing a single double-extraction/condensing turbogenerator at The Lihue Plantation Company on the island of Kauai. In addition to consolidating
Numberof BoilerUnits /
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Fig. 2. Average boiler and turbo-generator capacities and average number of boiler units per factory, 1961-87. 50~0. "~ ~ 30
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i 1965
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Fig. 3. Average pressure and temperature of Hawaiian sugar factory boilers, 1961-87.
steam and electricity generating systems, Hawaiian sugar factories increased the amounts of steam and electricity generated by making better use of the available biomass resources (as evidenced in Fig. 4 by dramatic reductions in the amounts of cane trash and bagasse discarded by the industry during recent years) and by taking advantage of various energy-recovery opportunities in the cogeneration and sugar-processing plants (Table 1).
Cogeneration in the Hawaiian sugar industry
Hydroelectric power played a major role in the electrification of the Hawaiian sugar industry, especially during its earlier years. Hydropower was introduced to Hawaii in 1897, at Waianae on the island of Oahu when electricity from a hydrogenerator was used to power three pumps (300 kW total) to transport more than 40 million liters of water per day (Anon., 1906a). Prior to that time virtually all irrigation pumps relied on steam generated from coal and, later, from fuel oil. This bold venture into hydroelectric power was followed by a major effort in 1906 when the McBryde Sugar Company on Kauai connected its two hydro-generators (1200 kW total) at Wainiha on the north end of the island to irrigation pumping stations on the southern plain (Anon., 1906 b). The 33 000 volt transmission line at Wainiha, 330 250~" 200
,/--X t~NN~k* '
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Fig. 4. Amounts of sugarcane trash and bagasse discarded by the Hawaiian sugar industry, 1975-87 (dry weight basis).
233
which stretched 55 km across forests and mountainous terrain, was the highest voltage line in use west of the US Rocky Mountains at that time. On the island of Maui, the HC & S Company took full advantage of its constant need for irrigation water by coupling its irrigation requirements with the production of electrical power from hydro sources in 1912 (Zeug, 1977). During that year an 800 kW plant was installed at Paia, and a 3200 kW plant, which was later expanded to 4500 kW, was completed at Kaheka where water from the Wailoa ditch dropped into lower ditches. The Kaheka and Paia plants are still in operation today as fully automatic facilities that operate 24 h/day except during periods of water shortage. Installation of hydro-generators on Hawaiian sugarcane plantations continued through most of this century; and today the industry controls virtually all of the hydro-generating capability in the state. Then, as today, on irrigated plantations the greatest demand for power outside of the factory came from irrigation pumps. As the demand for irrigation grew, so did the stand-alone coal- and oil-fired units powering pumps. The plantations eventually realized the advantages of electrifying pumps and, later, of centralizing power generation on the plantation. During the earliest years of electrification, sugar plantations generated electricity primarily to satisfy their own field and factory needs; however, as time progressed, plant-
Table 1. Information on cogeneration systems and steam vapor utilization and conservation practices in Hawaiian sugar factories
Sugar factory
Flue gas heat recovery devices"
Boiler blowdown recoveryb
TG extraction pressures'
Pressurized feedwater heating b
Juice heating 't
Juice evaporation"
Vapor bleeding stagesJ
Sugar boiling '~
Hamakua Sugar HCPC Ka'u Agribusiness Kekaha Sugar The Lihue Plantation McBryde Sugar Olokele Sugar HC & S-Paia HC & S-Puunene Pioneer Mill Oahu Sugar Waialua Sugar
A, D E, A, D A A E, A A -A, D A E, A E, A A, D
Y Y N N Y N N Y Y Y Y N
M, L M L L M, L L L M, L M, L M, L M, L L
N Y N N Y N N Y Y Y Y N
V F V V V V V F C V V V
4/F 5/F 4 5 5 5 4 5/F 5/F 5 5/F 5
1, 2 1,2 1 1, 2, 3, 4 1, 3 1,2, 3 1 1, 2, 4 1, 2, 4 1, 3 1, 4 1
V V V V V V V F V V V V
~A= air preheater, D = bagasse dryer (with partial bypass of flue gas), E = economizer. hy = practiced. N = not practiced. 'Turbo-generator extraction pressures: M ---medium pressure (10-15 bars), L = low pressure ( - 1 bar); all factories have at least one turbo-generator which operates in partial-condensing mode. dMedium used for heating: V = vapors, F = some flashed condensates, C = some liquid condensates. eNumber of effects and related practices: 4 = quadruple effect, 5 = quintuple effect; F = flashing of condensates practiced. fNumber indicates evaporation effect from which vapors are bled for other heating purposes.
234
C. M. Kinoshita
ations began to supply electricity to their labor camps and then to nearby communities, in effect serving the role of local utility companies.
EXPANSION OF POWER EXPORTATION
During the first half of the twentieth century sugar factories often had the only major electrical generating capabilities and supplied most of the power to communities on all of the major islands which neighbor Oahu. It is, therefore, not surprising that the electric utility companies on the neighboring islands relied heavily on the sugar industry for power. As an example of the significance of the industry in supplying power to the community and the strong reliance of utility companies on sugar companies for power, it was not until 1948 that Maui Electric Company (MECO) installed its first significant electrical generating unit on Maui. Prior to that time MECO was a utility company which essentially generated no power, relying instead on private power producers, including the three sugar plantations, HC&S, Maui Agricultural, and Pioneer Mill Companies, for electricity. MECO was forced to enter the power-generation business as the plantations on the island became reluctant to expand their power export obligations to meet the growing demand of the public. Kauai Electric Company (KECO), which was originally owned by Kauai sugar companies, installed its first electrical generating equipment (two 2000-kW diesel generators) in 1964. Like MECO, KECO was forced to enter the power-generation business because the plantations decided that they did not want to carry the expanding financial burden of providing increasing amounts of electrical power to the public as Kauai grew. It is difficult to ascertain precisely when electricity was first exported by a Hawaiian sugarcane plantation to a public utility company. (This is clouded by the unique social and corporate relationships that some of the plantations had with the surrounding communities and the utility companies.) There are records of electricity being exported by factories prior to 1910 (Memo, 1910); whether this period represents the earliest years of power being exported by the industry is unknown to the author. These early power agreements formed the basis for the existing contracts between the plantations and the utility companies. Although utility companies have grown sig-
nificantly during the past several decades and the association between the public utilities and sugar plantations has changed markedly over that time, to this date the electrical utility companies on the neighboring islands continue to rely heavily on the sugar industry for electrical energy and generating capacity. In more recent years two significant events occurred which helped to shape power sales arrangements in Hawaii. Although a number of sugar plantations exported power to utility companies on a firm basis prior to 1970, the power sales agreements generally called for the export of a rather small portion of that produced by the sugar plantation. The first major firm power agreement between a sugar producer and a utility company in Hawaii was reached in 1969. This agreement called for the Puna Sugar Company on the island of Hawaii to deliver an increasing amount of electricity (beginning with 70 million kWh in 1971 and escalating to 97 million kWh in 1976) to the Hilo Electric Light Company. Within two years after beginning the delivery of power under the agreement, it became apparent that the sugar plantation would have difficulty meeting its obligation to deliver by burning only bagasse, and in 1975 the Puna Sugar Company exercised its contractual option to reduce its annual obligation by one half. While not totally successful from the business standpoint, the Puna Sugar Company agreement did form a basis for subsequent firm power agreements involving Hilo Coast Processing (with delivery of firm power commencing in 1974), The Lihue Plantation (1981), Hamakua Sugar (1982), and Hawaiian Commercial and Sugar (1982) Companies. In 1980, accompanying the last major cogeneration consolidation effort in the Hawaiian sugar industry, another important event occurred -- the first three-party export power agreement -involving a sugar company (The Lihue Plantation Company; the operator of the cogeneration system), a boiler manufacturer (Foster Wheeler Corporation; the manufacturer/owner of the system), and the utility company (Citizens Utilities Company; the purchaser of the electricity generated) on the island of Kauai. Although no similar arrangement involving the industry has materialized since the Lihue Plantation/Foster Wheeler/ Citizens Utilities agreement, this three-party agreement set an important precedent and may become a model for future export power agreements in the Hawaiian sugar industry and agribusinesses elsewhere.
Cogeneration in the Hawaiian sugar industry INCREASED COMPLEXITY ARISING FROM REGULATORY POLICIES
Prior to 1970 the development of electricity generation in the Hawaiian sugar industry was shaped primarily by technical developments; however, in more recent years electricity generation has been influenced substantially by regulatory and contractual issues. In the earlier years of the industry there was little incentive for sugar factories, other than as a service to the community, to export substantial amounts of power to utility companies because the public utilities were not required to purchase power from independent producers and the power sold to the utility companies usually commanded a low price (e.g. in 1975 the average price received by the industry for electricity sold to utility companies was approximately S0.01 per kwh; Murata & Gibson, 1977). Moreover, in exporting power to utility companies sugar factories faced the risk of being subject to the same regulations as the utility companies. However, in the late 1970s and early 1980s several important regulatory developments took place. In 1977. Act 102, which exempted independent power producers from Public Utilities Commission regulations, became law in the state of Hawaii. This was followed by the landmark federal Public Utilities Regulatory Policies Act IPURPA) of 1978 which mandated that public utility companies purchase electricity generated by independent producers at reasonable rates without discrimination to the producer, and exempted the producer from key federal and state public utility regulations. Section 210 of PURPA, promulgated in 1980, eliminated many of the regulatory and economic impediments to power production, and :instructed the public utilities to purchase power from independent electrical power generators at the avoided cost (i.e. the cost of producing an equivalent amount of energy). In 1982 State of Hawaii Public Utilities Commission Regulation, Title 6, Chapter 74, Standards for Small Power Production and Co-generation in the State of Hawaii, was adopted. This regulation was amended in 1985 to include the concepts of avoided cost and the minimum floor price, making it, in effect, a local PURPA regulation. The federal (PURPA) and state (Title 6, Chapter 74) regulations, in one manner or another, influence nearly all agreements between utility companies and independent power producers in the state today.
235
Ironically, the most formidable power-generation challenge facing the industry today is not the improvement of steam- or electrical-generation efficiency or taking advantage of the key regulations relating to the export of electrical power by non-utility generators, but the control of particulate emissions from boilers in an economical manner. The industry must comply with several state and federal regulations on boiler opacity and particulate emissions. These regulations, to the confusion of many, vary between installations. The applicable state regulations for bagasse-fired boilers built prior to March 1972 require particulate emissions <0.4% (based on bagasse, as burned) and opacity <40%. Regulations for boilers built after March 1972 require best available control technology (which is determined on a case-by-case basis) and opacity <20%. Even though the industry has spent tens of millions of dollars during the past two decades in an attempt to comply with state and federal emissions regulations, control of boiler emissions still poses a major challenge to the industry. EXPORT POWER AGREEMENTS
Today every sugar company in Hawaii has a power sales agreement with one of the four major utility companies that serve Hawaii. The essential features of the existing power sales contracts between individual sugar companies and utility companies are listed in Table 2. The terms of power sales contracts vary widely throughout the industry, depending on what regulations governed such agreements and on the prevailing costs of energy and electrical generating capacity at the time the agreements were reached and on the firmness of the obligation to deliver energy and capacity. Of the 11 sugar companies with power sales contracts, four have commitments to deliver prescribed amounts of energy, usually following specific time schedules (firm power); the others deliver power on unscheduled bases. Those sugar companies with firm power commitments generally face substantial penalties if they cannot meet their obligation to deriver power. While Hawaiian sugar factories with firm power contracts are capable of exporting 10-20 MW of electrical power primarily from bagasse during steady factory operations, maintaining the capability to supply power on a nearly continuous basis imposes a significant burden on the sugar factory, which can no longer consider itself solely as a sugar processor.
C. M. Kinoshita
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Cogeneration in the Hawaiian sugar industry
Like the obligation to deliver, the compensation received for electrical energy varies widely throughout the industry; ironically, the former has very little bearing on the latter. Compensation for electricity sold to utility companies is usually linked to the price of fuel oil, to the cost avoided by the utility company in generating an equivalent amount of energy, or to the consumer price index (CPI). Many sugar companies have agreements to provide power to utility companies during emergencies. Power delivered under such situations generally commands a premium price; however, during such periods the sugar company generally has to curtail some of its own operations. As implied in Table 2, electrical energy and generating capacity are generally treated as two distinct components of the electricity sold to utility companies. The above-mentioned federal and state regulations call for electrical energy to be purchased at no less than the avoided energy cost (although, upon mutual agreement, the rate may be lower for long-term contracts) and may call for the establishment of a floor price at the time the contract becomes effective. Payment for capacity is generally based on the individual utility company's need for additional firm capacity. As shown in Table 2, payment for capacity can represent a substantial portion of the total revenue received from the electrical utility company. This is especially true where the utility company is faced with a shortfall in capacity, as is the case on virtually all of the Hawaiian islands.
SUMMARY
The Hawaiian sugar industry is among the most efficient in the world in cogenerating process steam and mechanical and electrical power from biomass. The Hawaiian sugar industry is one of the most significant exporters of electrical energy from biomass worldwide -- Hawaiian sugarcane plantations produce roughly 10% of all elecricity generation units into larger and more efficient one-half of the electricity delivered to the general public by the utility companies originates from the sugar industry. The attainment of high energy efficiency has largely resulted from technical improvements (better utilization of bagasse and cane trash and the steam generated therefrom), and through consolidation of steam and power generation units into large and more efficient
237
systems. However, regulatory and contractual issues have also influenced the evolution of cogeneration in Hawaii. The sale of electricity has presented most Hawaiian sugar companies with a significant source of revenue to supplement the returns from their traditional products, sugar and molasses; however, the obligation to supply power has imposed a substantial burden on many of those same sugar factories. Whether electricity sales will strengthen the economic viability of the industry or become a major burden to sugar companies will become apparent during the next decade.
ACKNOWLEDGEMENTS
This work was performed under the sponsorship of the United States Agency for International Development/Tennessee Valley Authority, through a subcontract from the Experiment Station of the Hawaiian Sugar Planters' Association (HSPA). The author acknowledges the significant contribution of HSPA, in particular librarians Ann Marsteller and Harriet Iwai, for providing much of the information contained in this report, and the members of the Sugar Technology and Engineering Department and Mr Robert H. Hughes (HSPA, retired) for their valuable assistance. Finally, the guidance of Mr John Kadyszewski, Program Manager of the Bioenergy Systems and Technology Project, Office of Energy, Agency for International Development, is fully acknowledged. REFERENCES Anon. (1906a). Pacij~c Commercial Advertiser, Honolulu, Hawaii, 2 July. Anon. (1906b). Pacific Commercial Advertiser, Honolulu, Hawaii, 5 August. Anon. (1919). Pacific Commercial Advertiser, Honolulu, Hawaii, 21 February. Memo (1910). Memorandum of Agreement Between Lahaina Ice Company and Pioneer Mill Company. Hawaiian Sugar Planters' Association Plantation Archives, May. Murata, D. & Gibson, W. (1977). Energy Inventory for Hawaiian Sugar Factories -- 1975. Hawaiian Planters' Record, 59 (5), 51-66. Thrum, T. G. (ed.) (1875). Hawaiian Almanac and Annual for 1875. Pacific Commercial Advertiser Printing House, Honolulu, Hawaii, p. 39. Zeug, M. (1977). Plantation power. Ampersand, Summer, 11 (2), 25-32.
Review Article Cogeneration in the Hawaiian Sugar Industry C. M. Kinoshita Hawaii Natural Energy Institute, University of Hawaii at Manoa, 2540 Dole Street, Honolulu, Hawaii 96822, USA ¢Received 13 February 1990; accepted 28 March 1990)
Abstract For nearly a century the Hawaiian sugar industry has produced most of the steam and electricity needed to process sugarcane and to power its factories and irrigation pumps. This use of bagasse (the fibrous by-product of milled sugarcane), cane leaves and tops has made the Hawaiian sugar industr 3, among the most efficient in the world in converting biomass into electricity -- in comparison with typical worldwide cane-to-electricity conversion productivities of - 10 k w h per tonne of cane, Hawaiian sugar factories today generate, on average, about 60 k w h per tonne of cane and, in some factories, 100 k w h or more. Plantations in Hawaii produce about 800 million k w h annually, and, after satisfying virtually all of their internal power requirements, export roughly 400 million k Wh to public utility companies. Key words: Cogeneration, bagasse, sugarcane, electricity.
INTRODUCTION The generation and use of steam and electricity by the Hawaiian sugar industry has had a long and rather unique history. Milestones in steam and electricity generation and disposition during the past 150 years are summarized in Fig. 1 and are discussed below. Bagasse has been the primary fuel for the industry since the earliest Hawaiian sugar factories. However, its use prior to 1840 was largely restricted to sugar-boiling plants which, at the
time, consisted of a train of uncovered pots over open wood and bagasse fires to concentrate cane juice for sugar crystallization. In 1840 steam coils replaced the open fire for concentrating juice, and, in 1861, the industry made a major advance by introducing a vacuum pan to boil sugar at the Kaupakuea Plantation on the island of Hawaii. During the earliest years of the Hawaiian sugar industry, bagasse often contained so much moisture that it had to be sun-dried prior to firing, or, if burned immediately after milling, had to be supplemented with substantial amounts of wood or coal. However, as milling practices and equipment improved so did the quality of bagasse as a fuel, to the extent that by the late 1800s bagasse was being conveyed directly from the cane mills and burned in boilers without supplemental fueling. Although bagasse has played a major role in sugar processing since the Hawaiian sugar industry was in its infancy, it was not used to provide mechanical power until the mid-1800s. Prior to 1850 most Hawaiian sugar factories used animals or flowing water to drive their mills. Steam was first adopted to power mills at the Haiku Plantation on the island of Maui in 1858 (Thrum, 1875). This practice gained favor rapidly -- by 1861 nearly one-half of the factories in the industry were relying on reciprocating steam engines to power their mills. Steam engines continued to be the major mode of power transformation in milling cane in Hawaiian sugar factories until 1900 when the first steam turbine was installed at the Ewa Plantation on Oahu. Today, virtually every sugar factory has abandoned the reciprocating steam engine in favor of the steam turbine for large mechanical power applications.
231 Bioresource Technology 0960-8524/91/S03.50 © 1991 Elsevier Science Publishers Ltd, England. Printed in Great Britain
232
C. M. Kinoshita
Steam coils first used to concentrate cane juice Steam adopted for motive power Vacuum~ans introduced • Electricity first used as major power source ~, First steam turbine drive installed • Molasses mixed with bagasse for fuel Fuel oil first used for pumping First large turbogenerator unit installed Maui Electric Co. installs its first unit First relatively high pressure boiler installed • Kauai Electric Co. installs its first unit First major firm-power agreement established Act 102 becomes Hawaii law 9 . Passage of PURPA Last multiple small boiler system replaced • First three-party cogeneration arrangement established • Passage of Title 6, Chapter 74
1800
I
I
I
I
I
I
I
I
I
I
1820
1840
1860
1880
1900
1920
1940
1960
1980
2000
Year
Fig. 1. Majormilestones -- cogeneration in the Hawaiian sugar industry.
120
ELECTRIFICATION OF THE INDUSTRY
10
1 /
.e- BoilerCapacity
o-pc_
o
"E
=-~ 100
In the early 1900s, both field (primarily irrigation) and factory operations on plantations were powered mainly by steam, except where electricity from hydroelectric sources was available. Although there are references to numerous small electrical generating units in Hawaiian sugar factories shortly after the turn of the century, the emergence of bagasse-generated electricity as a significant form of power came in 1916 when the first large sugar factory power plant in Hawaii, consisting of two 750 kW turbo-generators, was built at Hawaiian Commercial and Sugar Company on the island of Maui (Anon., 1919). The introduction of the large factory power plant intensified electrification in the sugar industry and, in turn, the evolution of electrification spurred expansion of the sugar factory power plant. As electrification intensified and the demand for electricity expanded, so did the industry's steam and power generation facilities. The need for greater energy efficiency and less labor input (which was becoming among the most expensive in the world) to operate and maintain cogeneration systems forced the industry to consolidate steam and power generating equipment into larger and more efficient units (e.g., see Figs 2 and 3). The process of consolidation of cogeneration units culminated in 1980 when nine low-pressure boilers and three turbo-generators were replaced by one fairly high pressure boiler servicing a single double-extraction/condensing turbogenerator at The Lihue Plantation Company on the island of Kauai. In addition to consolidating
Numberof BoilerUnits /
~.
8 ~
/1
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6co
80
>
-~ 60
4~
~ 40 o co 20
.6
01960
I
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1965
1970
1975
1980
1985
0 1990
Year
Fig. 2. Average boiler and turbo-generator capacities and average number of boiler units per factory, 1961-87. 50~0. "~ ~ 30
-o. Pressure I "°" Temperature
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....
400
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~, 20
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100
F-
10 0 1960
i 1965
i 1970
i 1975
i 1980
r 1985
0 1990
Year
Fig. 3. Average pressure and temperature of Hawaiian sugar factory boilers, 1961-87.
steam and electricity generating systems, Hawaiian sugar factories increased the amounts of steam and electricity generated by making better use of the available biomass resources (as evidenced in Fig. 4 by dramatic reductions in the amounts of cane trash and bagasse discarded by the industry during recent years) and by taking advantage of various energy-recovery opportunities in the cogeneration and sugar-processing plants (Table 1).
Cogeneration in the Hawaiian sugar industry
Hydroelectric power played a major role in the electrification of the Hawaiian sugar industry, especially during its earlier years. Hydropower was introduced to Hawaii in 1897, at Waianae on the island of Oahu when electricity from a hydrogenerator was used to power three pumps (300 kW total) to transport more than 40 million liters of water per day (Anon., 1906a). Prior to that time virtually all irrigation pumps relied on steam generated from coal and, later, from fuel oil. This bold venture into hydroelectric power was followed by a major effort in 1906 when the McBryde Sugar Company on Kauai connected its two hydro-generators (1200 kW total) at Wainiha on the north end of the island to irrigation pumping stations on the southern plain (Anon., 1906 b). The 33 000 volt transmission line at Wainiha, 330 250~" 200
,/--X t~NN~k* '
Cane Trash
-o- Bagasse
I
°° 15o o c
g loo
<
50
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0
1974
--~-°~o__o__o~ *---...°Tg~° ~"~o~o
l
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1978
i
l
1980 1982 Year
l
1984
o ~
1986
1988
Fig. 4. Amounts of sugarcane trash and bagasse discarded by the Hawaiian sugar industry, 1975-87 (dry weight basis).
233
which stretched 55 km across forests and mountainous terrain, was the highest voltage line in use west of the US Rocky Mountains at that time. On the island of Maui, the HC & S Company took full advantage of its constant need for irrigation water by coupling its irrigation requirements with the production of electrical power from hydro sources in 1912 (Zeug, 1977). During that year an 800 kW plant was installed at Paia, and a 3200 kW plant, which was later expanded to 4500 kW, was completed at Kaheka where water from the Wailoa ditch dropped into lower ditches. The Kaheka and Paia plants are still in operation today as fully automatic facilities that operate 24 h/day except during periods of water shortage. Installation of hydro-generators on Hawaiian sugarcane plantations continued through most of this century; and today the industry controls virtually all of the hydro-generating capability in the state. Then, as today, on irrigated plantations the greatest demand for power outside of the factory came from irrigation pumps. As the demand for irrigation grew, so did the stand-alone coal- and oil-fired units powering pumps. The plantations eventually realized the advantages of electrifying pumps and, later, of centralizing power generation on the plantation. During the earliest years of electrification, sugar plantations generated electricity primarily to satisfy their own field and factory needs; however, as time progressed, plant-
Table 1. Information on cogeneration systems and steam vapor utilization and conservation practices in Hawaiian sugar factories
Sugar factory
Flue gas heat recovery devices"
Boiler blowdown recoveryb
TG extraction pressures'
Pressurized feedwater heating b
Juice heating 't
Juice evaporation"
Vapor bleeding stagesJ
Sugar boiling '~
Hamakua Sugar HCPC Ka'u Agribusiness Kekaha Sugar The Lihue Plantation McBryde Sugar Olokele Sugar HC & S-Paia HC & S-Puunene Pioneer Mill Oahu Sugar Waialua Sugar
A, D E, A, D A A E, A A -A, D A E, A E, A A, D
Y Y N N Y N N Y Y Y Y N
M, L M L L M, L L L M, L M, L M, L M, L L
N Y N N Y N N Y Y Y Y N
V F V V V V V F C V V V
4/F 5/F 4 5 5 5 4 5/F 5/F 5 5/F 5
1, 2 1,2 1 1, 2, 3, 4 1, 3 1,2, 3 1 1, 2, 4 1, 2, 4 1, 3 1, 4 1
V V V V V V V F V V V V
~A= air preheater, D = bagasse dryer (with partial bypass of flue gas), E = economizer. hy = practiced. N = not practiced. 'Turbo-generator extraction pressures: M ---medium pressure (10-15 bars), L = low pressure ( - 1 bar); all factories have at least one turbo-generator which operates in partial-condensing mode. dMedium used for heating: V = vapors, F = some flashed condensates, C = some liquid condensates. eNumber of effects and related practices: 4 = quadruple effect, 5 = quintuple effect; F = flashing of condensates practiced. fNumber indicates evaporation effect from which vapors are bled for other heating purposes.
234
C. M. Kinoshita
ations began to supply electricity to their labor camps and then to nearby communities, in effect serving the role of local utility companies.
EXPANSION OF POWER EXPORTATION
During the first half of the twentieth century sugar factories often had the only major electrical generating capabilities and supplied most of the power to communities on all of the major islands which neighbor Oahu. It is, therefore, not surprising that the electric utility companies on the neighboring islands relied heavily on the sugar industry for power. As an example of the significance of the industry in supplying power to the community and the strong reliance of utility companies on sugar companies for power, it was not until 1948 that Maui Electric Company (MECO) installed its first significant electrical generating unit on Maui. Prior to that time MECO was a utility company which essentially generated no power, relying instead on private power producers, including the three sugar plantations, HC&S, Maui Agricultural, and Pioneer Mill Companies, for electricity. MECO was forced to enter the power-generation business as the plantations on the island became reluctant to expand their power export obligations to meet the growing demand of the public. Kauai Electric Company (KECO), which was originally owned by Kauai sugar companies, installed its first electrical generating equipment (two 2000-kW diesel generators) in 1964. Like MECO, KECO was forced to enter the power-generation business because the plantations decided that they did not want to carry the expanding financial burden of providing increasing amounts of electrical power to the public as Kauai grew. It is difficult to ascertain precisely when electricity was first exported by a Hawaiian sugarcane plantation to a public utility company. (This is clouded by the unique social and corporate relationships that some of the plantations had with the surrounding communities and the utility companies.) There are records of electricity being exported by factories prior to 1910 (Memo, 1910); whether this period represents the earliest years of power being exported by the industry is unknown to the author. These early power agreements formed the basis for the existing contracts between the plantations and the utility companies. Although utility companies have grown sig-
nificantly during the past several decades and the association between the public utilities and sugar plantations has changed markedly over that time, to this date the electrical utility companies on the neighboring islands continue to rely heavily on the sugar industry for electrical energy and generating capacity. In more recent years two significant events occurred which helped to shape power sales arrangements in Hawaii. Although a number of sugar plantations exported power to utility companies on a firm basis prior to 1970, the power sales agreements generally called for the export of a rather small portion of that produced by the sugar plantation. The first major firm power agreement between a sugar producer and a utility company in Hawaii was reached in 1969. This agreement called for the Puna Sugar Company on the island of Hawaii to deliver an increasing amount of electricity (beginning with 70 million kWh in 1971 and escalating to 97 million kWh in 1976) to the Hilo Electric Light Company. Within two years after beginning the delivery of power under the agreement, it became apparent that the sugar plantation would have difficulty meeting its obligation to deliver by burning only bagasse, and in 1975 the Puna Sugar Company exercised its contractual option to reduce its annual obligation by one half. While not totally successful from the business standpoint, the Puna Sugar Company agreement did form a basis for subsequent firm power agreements involving Hilo Coast Processing (with delivery of firm power commencing in 1974), The Lihue Plantation (1981), Hamakua Sugar (1982), and Hawaiian Commercial and Sugar (1982) Companies. In 1980, accompanying the last major cogeneration consolidation effort in the Hawaiian sugar industry, another important event occurred -- the first three-party export power agreement -involving a sugar company (The Lihue Plantation Company; the operator of the cogeneration system), a boiler manufacturer (Foster Wheeler Corporation; the manufacturer/owner of the system), and the utility company (Citizens Utilities Company; the purchaser of the electricity generated) on the island of Kauai. Although no similar arrangement involving the industry has materialized since the Lihue Plantation/Foster Wheeler/ Citizens Utilities agreement, this three-party agreement set an important precedent and may become a model for future export power agreements in the Hawaiian sugar industry and agribusinesses elsewhere.
Cogeneration in the Hawaiian sugar industry INCREASED COMPLEXITY ARISING FROM REGULATORY POLICIES
Prior to 1970 the development of electricity generation in the Hawaiian sugar industry was shaped primarily by technical developments; however, in more recent years electricity generation has been influenced substantially by regulatory and contractual issues. In the earlier years of the industry there was little incentive for sugar factories, other than as a service to the community, to export substantial amounts of power to utility companies because the public utilities were not required to purchase power from independent producers and the power sold to the utility companies usually commanded a low price (e.g. in 1975 the average price received by the industry for electricity sold to utility companies was approximately S0.01 per kwh; Murata & Gibson, 1977). Moreover, in exporting power to utility companies sugar factories faced the risk of being subject to the same regulations as the utility companies. However, in the late 1970s and early 1980s several important regulatory developments took place. In 1977. Act 102, which exempted independent power producers from Public Utilities Commission regulations, became law in the state of Hawaii. This was followed by the landmark federal Public Utilities Regulatory Policies Act IPURPA) of 1978 which mandated that public utility companies purchase electricity generated by independent producers at reasonable rates without discrimination to the producer, and exempted the producer from key federal and state public utility regulations. Section 210 of PURPA, promulgated in 1980, eliminated many of the regulatory and economic impediments to power production, and :instructed the public utilities to purchase power from independent electrical power generators at the avoided cost (i.e. the cost of producing an equivalent amount of energy). In 1982 State of Hawaii Public Utilities Commission Regulation, Title 6, Chapter 74, Standards for Small Power Production and Co-generation in the State of Hawaii, was adopted. This regulation was amended in 1985 to include the concepts of avoided cost and the minimum floor price, making it, in effect, a local PURPA regulation. The federal (PURPA) and state (Title 6, Chapter 74) regulations, in one manner or another, influence nearly all agreements between utility companies and independent power producers in the state today.
235
Ironically, the most formidable power-generation challenge facing the industry today is not the improvement of steam- or electrical-generation efficiency or taking advantage of the key regulations relating to the export of electrical power by non-utility generators, but the control of particulate emissions from boilers in an economical manner. The industry must comply with several state and federal regulations on boiler opacity and particulate emissions. These regulations, to the confusion of many, vary between installations. The applicable state regulations for bagasse-fired boilers built prior to March 1972 require particulate emissions <0.4% (based on bagasse, as burned) and opacity <40%. Regulations for boilers built after March 1972 require best available control technology (which is determined on a case-by-case basis) and opacity <20%. Even though the industry has spent tens of millions of dollars during the past two decades in an attempt to comply with state and federal emissions regulations, control of boiler emissions still poses a major challenge to the industry. EXPORT POWER AGREEMENTS
Today every sugar company in Hawaii has a power sales agreement with one of the four major utility companies that serve Hawaii. The essential features of the existing power sales contracts between individual sugar companies and utility companies are listed in Table 2. The terms of power sales contracts vary widely throughout the industry, depending on what regulations governed such agreements and on the prevailing costs of energy and electrical generating capacity at the time the agreements were reached and on the firmness of the obligation to deliver energy and capacity. Of the 11 sugar companies with power sales contracts, four have commitments to deliver prescribed amounts of energy, usually following specific time schedules (firm power); the others deliver power on unscheduled bases. Those sugar companies with firm power commitments generally face substantial penalties if they cannot meet their obligation to deriver power. While Hawaiian sugar factories with firm power contracts are capable of exporting 10-20 MW of electrical power primarily from bagasse during steady factory operations, maintaining the capability to supply power on a nearly continuous basis imposes a significant burden on the sugar factory, which can no longer consider itself solely as a sugar processor.
C. M. Kinoshita
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Cogeneration in the Hawaiian sugar industry
Like the obligation to deliver, the compensation received for electrical energy varies widely throughout the industry; ironically, the former has very little bearing on the latter. Compensation for electricity sold to utility companies is usually linked to the price of fuel oil, to the cost avoided by the utility company in generating an equivalent amount of energy, or to the consumer price index (CPI). Many sugar companies have agreements to provide power to utility companies during emergencies. Power delivered under such situations generally commands a premium price; however, during such periods the sugar company generally has to curtail some of its own operations. As implied in Table 2, electrical energy and generating capacity are generally treated as two distinct components of the electricity sold to utility companies. The above-mentioned federal and state regulations call for electrical energy to be purchased at no less than the avoided energy cost (although, upon mutual agreement, the rate may be lower for long-term contracts) and may call for the establishment of a floor price at the time the contract becomes effective. Payment for capacity is generally based on the individual utility company's need for additional firm capacity. As shown in Table 2, payment for capacity can represent a substantial portion of the total revenue received from the electrical utility company. This is especially true where the utility company is faced with a shortfall in capacity, as is the case on virtually all of the Hawaiian islands.
SUMMARY
The Hawaiian sugar industry is among the most efficient in the world in cogenerating process steam and mechanical and electrical power from biomass. The Hawaiian sugar industry is one of the most significant exporters of electrical energy from biomass worldwide -- Hawaiian sugarcane plantations produce roughly 10% of all elecricity generation units into larger and more efficient one-half of the electricity delivered to the general public by the utility companies originates from the sugar industry. The attainment of high energy efficiency has largely resulted from technical improvements (better utilization of bagasse and cane trash and the steam generated therefrom), and through consolidation of steam and power generation units into large and more efficient
237
systems. However, regulatory and contractual issues have also influenced the evolution of cogeneration in Hawaii. The sale of electricity has presented most Hawaiian sugar companies with a significant source of revenue to supplement the returns from their traditional products, sugar and molasses; however, the obligation to supply power has imposed a substantial burden on many of those same sugar factories. Whether electricity sales will strengthen the economic viability of the industry or become a major burden to sugar companies will become apparent during the next decade.
ACKNOWLEDGEMENTS
This work was performed under the sponsorship of the United States Agency for International Development/Tennessee Valley Authority, through a subcontract from the Experiment Station of the Hawaiian Sugar Planters' Association (HSPA). The author acknowledges the significant contribution of HSPA, in particular librarians Ann Marsteller and Harriet Iwai, for providing much of the information contained in this report, and the members of the Sugar Technology and Engineering Department and Mr Robert H. Hughes (HSPA, retired) for their valuable assistance. Finally, the guidance of Mr John Kadyszewski, Program Manager of the Bioenergy Systems and Technology Project, Office of Energy, Agency for International Development, is fully acknowledged. REFERENCES Anon. (1906a). Pacij~c Commercial Advertiser, Honolulu, Hawaii, 2 July. Anon. (1906b). Pacific Commercial Advertiser, Honolulu, Hawaii, 5 August. Anon. (1919). Pacific Commercial Advertiser, Honolulu, Hawaii, 21 February. Memo (1910). Memorandum of Agreement Between Lahaina Ice Company and Pioneer Mill Company. Hawaiian Sugar Planters' Association Plantation Archives, May. Murata, D. & Gibson, W. (1977). Energy Inventory for Hawaiian Sugar Factories -- 1975. Hawaiian Planters' Record, 59 (5), 51-66. Thrum, T. G. (ed.) (1875). Hawaiian Almanac and Annual for 1875. Pacific Commercial Advertiser Printing House, Honolulu, Hawaii, p. 39. Zeug, M. (1977). Plantation power. Ampersand, Summer, 11 (2), 25-32.