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Investigation of induction stovetops for use in the new SUB Daw, Colin; Ecklin, Stephen; Reimer, Andrew 2011

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UBC Social Ecological Economic Development Studies (SEEDS) Student Report Investigation of Induction Stovetops for Use in the New SUB Colin Daw Stephen Ecklin Andrew Reimer University of British Columbia APSC 262 April 4, 2011 Disclaimer: “UBC SEEDS provides students with the opportunity to share the findings of their studies, as well as their opinions, conclusions and recommendations with the UBC community. The reader should bear in mind that this is a student project/report and is not an official document of UBC. Furthermore readers should bear in mind that these reports may not reflect the current status of activities at UBC. We urge you to contact the research persons mentioned in a report or the SEEDS Coordinator about the current status of the subject matter of a project/report”. EVALUATION OF INDUCTION STOVETOPS 1 AbstractThe induction stovetop is a fairly new innovation that is becoming morecommonplace in both residential kitchens and commercial establishments. Itpresents numerous advantages over its conventional gas and electric counterparts,but there are also some drawbacks that need to be considered, such as high initialcost and lack of widespread familiarity.  Numerous studies have been performed totest the efficiency and safety of all types of stovetops. Furthermore, there is bothscholarly and informal information available regarding other criteria forcomparison, including environmental effects, social impact, and economicalevaluation. This paper presents a triple-bottom-line evaluation of the numerousperspectives on induction cooking and its alternatives, with a view for commercialestablishment usage in the new Student Union Building (SUB) at UBC. Inductioncooking was found to comparable or better than its alternatives in all three areas ofour triple-bottom-line assessment; thus, we recommend it for use in the new SUB. Keywords: Triple-bottom-line, induction, Student Union Building EVALUATION OF INDUCTION STOVETOPS 2 Table of Contents Section Page Number Abstract 1 List of Illustrations 3 Glossary 3 List of Abbreviations 3 1.0 Introduction 4 2.0 Alternatives 5 3.0 Environmental Assessment 6 4.0 Economical Assessment 8 5.0 Social Assessment 10 5.1 Safety 10 5.2 Workplace Comfort 11 5.3 Health Effects 12 5.4 Limitations on the Ranges 14 6.0 Conclusion 17 References 18 EVALUATION OF INDUCTION STOVETOPS 3 List of Illustrations Illustration Page Number Table 1: System Efficiency Analysis Summary 7 Figure 1: Restaurant Energy Use Breakdown 8 Glossary Joule Heating – atomic energization of a material by electromagnetic inducedcurrent to increase thermal energy in the material. Eddy Current – Current induced in an electrical conductor by a magnetic field that ismoving relative to the conductor, or varying with time. List of Abbreviations Abbreviation Full Name AC Alternating Current (in electrical power sources) BTU British Thermal Unit (of Energy, 1 BTU = 1055 Joules) PG&E Pacific Gas & Electric Company EVALUATION OF INDUCTION STOVETOPS 4 1.0 IntroductionInduction cooking involves using an electromagnetic field to generate eddycurrents in a metal. The metal then heats through resistance, which is known asJoule heating (Renseas, 2008). The field is generated by passing a high-frequency ACcurrent through an electromagnet. In order to enhance the effectiveness of heattransfer, special cookware is often used. This cookware typically takes the form of amulti-ply base, with one layer specially designed to generate heat through induction,and the other layers designed to transfer that heat to the food being cooked and toresist corrosion (Ulam, 1987).Induction is a fairly new technology in comparison to it alternatives, gas andelectric stovetops. Gas is the standard for most homes and commercial kitchens. Itsbenefits include widespread familiarity and availability, with disadvantagesemerging in safety and efficiency. Electric stovetops (infrared and contact heating)have some of the safety and energy benefits of induction, but they take a long timeto heat up, are more difficult to adjust, and have surfaces that are hot to the touch,unlike induction. EVALUATION OF INDUCTION STOVETOPS 5 2.0 AlternativesGas stovetop technology has been in existence for a long time, and theefficiency of its burners has practically been maximized. However, one way to makea gas range more economical is to increase its efficiency. While it’s hard to improvethe efficiency of the burners themselves, there has been some research into newcookware that uses fins on the bottom to greatly enhance heat transfer and thus theefficiency of the system. In tests performed at the PG&E Food Service TechnologyCenter, they found these pots increased the efficiency of low-efficiency stoves fromaround 25% to over 40%, and of high-efficiency stoves from 30% to over 60%(Sorensen and Zabrowski, 2009). While this is impressive, efficiencies of inductionare generally in the 80-90% range. Thus, a further analysis of the sources of energyfor both types of stoves must be performed, and is outlined in further detail insubsequent sections of this report.Electric stovetops, which heat through contact or infrared light, were billedas an improvement over gas ranges when they first came out. There is not a wealthof scholarly literature available on the merits of this type of stove. The generalconsensus is that while they are more efficient than gas, they still lack the efficiencyof induction. Furthermore, they present dangers of a hot surface with littleindication of heat (i.e. flame), take longer to heat up, and are less adjustable. Thesefundamental disadvantages of electric stovetops make their implementation in thenew SUB less desirable than both gas and induction. Therefore, the remainder ofthis report will investigate and compare only induction and gas alternatives. EVALUATION OF INDUCTION STOVETOPS 6 3.0 Environmental AssessmentThe first portion of the triple-bottom-line assessment will analyze theenvironmental impacts of gas versus induction stoves. Through a life-cycle analysisof the two systems, no distinct difference in the longevity of the cooking surface orcookware was found. One notable danger of induction stovetops is their capacity torapidly melt aluminum foil, which could bond to the cooking surface if accidentallyplaced on top of a running hob (Heldman). However, the cooking surface can bereplaced without replacing all of the operational electronics. Efficiency analysissuggested that gas stoves generally transfer about 30% of input power to the foodbeing cooked, or up to 60% with special finned cookware. Induction, however,commonly tests between 82 and 85% heating efficiency (Sorensen and Zabrowski,2009), and some manufacturers claim up to 90% (The Middleby Corporation, 2010).However, when comparing the environmental impacts of both stovetops, theefficiency of the entire system – from the initial energy source through to foodpreparation – needs to be considered since the new SUB will only be providing 5%of the electrical power demand via renewable photovoltaic cells (UBC AMS, 2010).In the case of gas stoves, natural gas is recovered either from natural gasliquid deposits or as a by-product of oil recovery in some reserves. Since no energyconversion takes place during gas recovery, the only upstream energy losses in thegas stove system occur during transportation of the natural gas via pipeline. In apipeline efficiency analysis, Williams suggested that only 2-3% of fuel energy is lostin pipeline transport to overcome friction (Bowden, 2010). If gas stoves achieve 30-60% heating efficiency, then total gas stove system efficiency falls between 29% and EVALUATION OF INDUCTION STOVETOPS 7 58%. On the other hand, induction stoves require electrical input energy, whichmust be generated from another energy source. Electrical generation is typicallyonly 45% efficient (Green Energy Efficient Homes, 2010). An additional 8%upstream loss occurs due to electrical resistance during transportation andtransformation. Electricity transmission is 93-94% efficient (Bowden, 2010)whereas transformers are typically 99% efficient (Saint, 2008). Once electricityreaches the induction stove, 80-90% of the electrical energy is delivered to the food,giving a total system efficiency of 33-37%. The preceding system efficiency analysisis summarized in Table 1 below.Table 1: System Efficiency Analysis Summary System Production Transportation Cooking Total System Efficiency Gas 100% 97% 30% - 60% 29% - 58% Induction 45% 92% 80% - 90% 33% - 37% As seen in Table 1, induction stovetops are competitive with their traditional gascounterparts from a system efficiency standpoint, but if finned cookware is used in agas application, induction stoves may be the less efficient alternative. An importantnote in this comparison is that the primary source of electricity in BC ishydroelectric power. Since hydroelectric generation is a renewable process, theenergy loss due to production can be ignored because water is a renewable resourcethat replenishes itself regularly. This tips our recommendation towards induction,especially because the highest system efficiency for gas is based on finned cookware,which still has low availability and uncertain reliability. EVALUATION OF INDUCTION STOVETOPS 8 4.0 Economical AssessmentThe second part of the triple-bottom-line assessment will evaluate the initialand operational costs for gas and induction stoves for an economical comparison ofthe two alternatives. As seen in Figure 1, a commercial restaurant report fromSustainable Foodservice Consulting suggests that almost 25% of a restaurant’selectricity bill (the green area) comes from food preparation alone. Figure 1: Restaurant Energy Use Breakdown(Sustainable Foodservice Consulting, 2011)If the new SUB kitchen and cafeteria are modeled as commercial restaurants, thenFigure 1 suggests that a marginal cost savings from increased energy efficiency infood preparation will lead to the largest total cost savings for the new SUBcompared to any other category. Thus, it is extremely important to minimizeoperating cost of the cooking equipment used in the new SUB. EVALUATION OF INDUCTION STOVETOPS 9 Because technical reports and other technical information regarding anexisting commercial application of induction cookware are extremely rare if notnon-existent, a relative analysis was conducted for the initial and operating costcomparison between gas and induction stovetops. The initial cost of a singleinduction stovetop unit was found to be about $2100 while gas stoves generally cost$1000 (Green Energy Efficient Homes, 2010). However, sustainable cookwaremanufacturers such as the Middleby Corporation claim that the operating cost foran induction stovetop can be half that of a traditional gas stove. (The MiddlebyCorporation, 2010). Additional research confirmed that induction stovetops canoperate at roughly half the cost of their gas counterparts. As of April 1, 2010, BCHydro charges 4-6 cents per kilowatt-hour for commercial clients (BC Hydro, 2011)while a single induction stove typically operates at about 3 kilowatts (The MiddlebyCorporation, 2010). Typical gas consumption for a single gas stove is 70 000 BTU/hr(Engineering ToolBox, 2011), and the price of natural gas is 6 cents per 1000 BTU’s(Sze, 2006). Thus, the relative operating costs from the preceding figures are$0.18$ per hour for an induction stovetop and $0.42 per hour for gas. This briefeconomic comparison suggests that in a long-term application such as the new SUB,yearly operational cost savings from the use of induction stoves are likely to faroutweigh the initial cost savings associated with the implementation of gasalternatives. EVALUATION OF INDUCTION STOVETOPS 10 EVALUATION OF INDUCTION STOVETOPS 11 5.0 Social AssessmentThis section of the report will focus on the social aspects of induction stovesversus their gas counterparts.  This social breakdown will assess safety, workplacecomfort, emissions and their impact on worker health, and limitations of theappliances in operation. 5.1 SafetyOne of the most promising social benefits of using an induction stoveover a gas stove is that the induction stove is much safer.  The method of heatinput, as described above, relies on basically using the pot as a traditionalstove element - directly exciting the molecules via an electromagnetic fieldrather than using a flame. If one were to put a non-ferrous material inbetween the element and the pot, it would not be affected by the field that isheating the vessel above. The same action on a gas stove would be mostunadvisable.There is also a fear with gas stoves that a leak of fuel, whether it is dueto a pipe leak or negligence to spark the burner when it is in an “on” position,can lead to a major explosion.  Of course, safeguards such as tagging gas withan unpleasant sulphuric odour can help prevent a leak from becomingcatastrophic.  It is possible to keep a gas stovetop ignited while a pot is not onthe element, but many induction stoves have sensors that detect a ferrouspot above the cooking area (The Induction Site, 2010). If one does not exist,or it is insufficient in size to be a true cooking vessel, the element does notcreate a field.  This feature is especially effective for an industrial cooking EVALUATION OF INDUCTION STOVETOPS 12 application, where burners are left on all day, because the ranges draw lesspower when they are not creating a field to heat the pot when it is not there. 5.2 Workplace ComfortTo address workplace comfort, the ambient temperature of thecooking area will be considered first. With a gas stove, approximately 60% ofthe gas energy is lost during cooking, compared to about 15% of heat losswith an induction stovetop (The Induction Site, 2010).  This energy is mostlylost through heat transfer to the surrounding kitchen, making temperatureshigher. Even if a temperature regulation system is in place, the issue changesinto one of space heating rather than one addressing workplace comfortlevels.  With higher temperatures in the kitchen, workers are lesscomfortable and more prone to stress (Kuse et al, 2000).   If moretemperature regulation needs to be done, this will result in more heatingcosts. Another issue that can be traced to worker comfort is the unwantedcooking of non-organic materials and mishandled food in a burner.  Resultingin odours, smoke, and possibly even a significant loss of material, the burningof these by-products can be avoided with an induction stove, as stated abovein the safety discussion.  These by-products, as well as the gas combustionproducts, result in vaporized material that is deposited on the surfacesaround the cook-top in the form of stains and film (The Induction Site, 2010)(Kuse et al, 2000). EVALUATION OF INDUCTION STOVETOPS 13 An induction stove may also produce noises if the cooking vesselcontains materials referred to as “slugs”, which will cause vibrations (TheInduction Site, 2010).  Vibrations can also be caused by poorly designed lidsand pot-bottoms, but most of these issues can be avoided by buying qualityvessels.  Listed below in section 5.3 are some ways the UBC SUB project willaddress some of these comfort issues. 5.3 Health EffectsA widely discussed issue relating to the competition betweeninduction and gas is the harmful emissions from both technologies and theirimpact on worker health.  The Scientific Committee on Toxicity, Ecotoxicityand the Environment (2001) and  the Scientific Committee on Emerging andNewly Identified Health Risks ( 2006) discuss the health effects of “extremelylow frequency electromagnetic fields”, referenced as “ELF magnetic fields”,that come from devices such as an induction stove.  Both groups assess thesefields and their possibility of being a carcinogen, causing childhood leukemia,causing breast cancer, causing DNA damage, resulting in hypersensitivity toradiation, and leading to many other diseases, but these impacts are deemedas negative or inconclusive by both.  There are a number of possible healthimpacts discussed by the Scientific Committee on Emerging and NewlyIdentified Health Risks (2006), such as enhanced development of tumours,impedance of DNA repair, cell damage, and inhibition of certain breast cancertreatments.  These claims are all noted as either unlikely but requiring EVALUATION OF INDUCTION STOVETOPS 14 further research, biased by other proven factors due to the scientific methodimplemented, or a combination thereof.The impact of gas stoves on health has many conflicting claims like itsinduction-based counterpart.  Burning gas results in hydrocarbons likecarbon monoxide and other by-products.  Without proper ventilation, carbonmonoxide can be a serious issue. According to information from variousstudies, it appears that gas emissions have negligible impact on adult health,but seem to have more impact on children (Eisner and Blanc, 2003)(Jarvis,Chinn, Steme, Luczynska, and Burney, 1998) (Melia, Florey, Altman, andSwan, 1977).  According to Melia, Florey, Altman, and Swan (1977) gas mayincrease prevalence of bronchitis, day and night cough, morning cough, chestcolds, wheeze, and asthma in children.  This study does not address the adultpopulation, but one would expect there to be possible correlations with someworkers.  Gas stove byproducts apparently have no impact on chronic coughor phlegm production within a sample group of adults already with asthma,and might be related to a greater risk of other respiratory symptoms.  Thesepossible symptoms are not excluded in a 95% confidence interval, so there isnot enough evidence to support the validity of this claim (Eisner and Blanc,2003). Researchers Jarvis, Chinn, Steme, Luczynska, and Burney (1998) statethat gas cooking in selected countries is associated with respiratorysymptoms in females.  As well, this article suggests that exposure to gasshould be minimized, appliances should be properly maintained, and properkitchen ventilation is encouraged. EVALUATION OF INDUCTION STOVETOPS 15 Looking at the SUB 75% schematic, the plans call for negativepressure for odour control; commercial exhaust ventilators above anycooking equipment to vent grease, odours, humidity, and other cooking by-products; and the consideration of filters in the air systems (UBC AMS, 2010).All of these address some of the gas by-product and grease particulate issues,as well as the residue and odour problems discussed in section 5.2.   Theschematic also says that “equipment selected shall enable the operator tomaintain or enhance accepted health standards,” (UBC AMS, 2010).  Thoughgas ranges are clearly adequate given the operating conditions and aforesaidplans, it is interesting to consider how to “enhance” the accepted healthstandards.  Many measures seem to be in place to ensure the best healthpractices, but it might be more beneficial to implement induction ranges. 5.4 Limitations on the RangesOne attribute that is prevalent in the selection of gas ranges by cooksis the range’s apparent unique ability to be finely adjusted to fit the cookingparameters.  The induction range actually has the same ability to be finelyadjusted (Kuse et al, 2000). Since interviews with chefs about theadjustability of different ranges were not possible, a cooking site called“Seasoned Advice” was used – where cooks share recipes and equipmentadvice.  A general consensus with cooks that have made the switch from gasto induction is that the controls are just as finely adjustable, but other issuessurface.  Problems with getting accustomed to arbitrary range of heatingvalues (instead of relying on flame size), possibly non-linear heating EVALUATION OF INDUCTION STOVETOPS 16 adjustments, and touch screen controls are voiced (Seasoned Advice, 2010).Many people claim that the induction stovetop is faster at heating food than agas one, perhaps due to the efficient energy transfer.  This would result inshorter cooking times, and a more efficient kitchen.For cooking applicability, there are a number of issues with inductionranges. One is the inability of the induction stovetop to char peppers andother food items you wish to insert into an open flame (The Induction Site,2010).  As well, one “Seasoned Advice” cook complains about the use of aninduction element on with large pan – which will have cold spots on theoutside because of the limited extent of the electromagnetic field (SeasonedAdvice, 2010).  Some brands do have ranges that are fully active on the topsurface: adjusting their field to the size of the cookware on the surface (TheInduction Site, 2010).  This was an isolated incident, and no furtherinformation can be found on the limited vessel size topic.  As the UBC SUBwill probably invest in high quality ranges, this will be an unlikely problem.Regarding limitations on equipment to be used with the ranges, asstated before, only ferrous materials can be used with an induction range.While gas stoves may damage the bottom of a pot over time with the flame,all (non-flammable) cooking vessels can be used on them.  These specialcooking materials are slightly more difficult to find, but it must be assumedthat UBC will be able to find a reliable dealer for this problem, and manycommon vessels are applicable (The Induction Site, 2010) (Seasoned Advice,2010). EVALUATION OF INDUCTION STOVETOPS 17 A definite positive of using induction stovetops is their ability to beeasily cleaned.  Other heating methods require an interruption in the stovesurface to integrate the cooking field, but an induction stovetop can beperfectly smooth (Kuse et al, 2000).  All entries that reference cleaning at“Seasoned Advice” (2010) also address this easy ability to clean the inductionrange surface. As well, since grease, splatter, and burned food are much moreprevalent on the surface and surrounding surfaces of the gas ranges, theseissues compound the problem of cleaning.On another note, no information could be found on how induction andgas stovetops are manufactured. One would assume that they both haveequal likelihood, and a very low likelihood, that they are made unethically.Since they are, in practice, almost identical in practicality and applicability tothe kitchens, they have no adverse social impacts in terms of amount of useand worker training. EVALUATION OF INDUCTION STOVETOPS 18 6.0 ConclusionIt is clear that both gas and induction stoves have advantages anddisadvantages associated with their use in residential and commercial applications.Gas stoves, the current standard for commercial kitchens, have undergone severaldecades of optimization and implementation, so they are widely available and mostpeople are familiar with their function. On the other hand, induction stovetopsaddress the main drawbacks of gas stoves, in that induction stovetops haveextremely high heating efficiency, as well as instant cooling and a cool cookingsurface. The main drawbacks of induction stovetops are the lack of familiarity incommercial applications, and large initial upfront cost.The results of the triple-bottom-line assessment of induction stovetops forimplementation in the new SUB suggest that induction stovetops are superior to gasstoves from both an economical and social point of view. In the long run, the loweroperating cost of induction stoves will lead to cost savings despite the higher initialcost compared to gas. Socially, workplace safety is increased by the implementationof induction stoves due to cool cooking surface properties and reduction of the riskof gas leaks. Finally, environmental analysis suggested induction stoves are at leastcomparable to their gas counterparts from an energy efficiency point of view, orbetter if electricity to the new SUB is supplied mostly by renewable energyresources such as hydroelectricity. From these results, it is clear that inductionstovetops are far superior to traditional gas stoves for implementation in the newSUB kitchen according to triple-bottom-line evaluation criteria. EVALUATION OF INDUCTION STOVETOPS 19 ReferencesBC Hydro (2011). BC Hydro Electricity Rate Comparison (Chart). Retrieved onMarch 28, 2011 from <http://www.bchydro.com/youraccount/content/residential_ rates.jsp>Bowden, L. (2010). Current State of Pipeline Optimization Efforts. Williams.Retrieved on March 28, 2011 from <http://www.gaselectricpartnership.com/fbowdenWms020811.pdf>Eisner, M.D., and Blanc, P.D. (2003). Gas Stove Use and Respiratory Health AmongAdults with Asthma in NHANES III, Occup Environ Med, Retrieved on March 1,2011 from <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1740397/pdf/v060p00759.pdf>Engineering ToolBox (2011). Natural Gas Consumption. Retrieved on March 20,2011 from <http://www.engineeringtoolbox.com/natural-gas-consumption-d_172.html>Green Energy Efficient Homes (2010). Energy Saving Induction Cooking. Retrievedon March 20, 2011 from <http://www.green-energy-efficient-homes.com/energy-saving-induction-cooking.html>Green Restaurant Guide: Energy Conservation. (n.d.). Green Energy. Retrieved March6, 2011 from <www.sfdph.org/dph/files/EHSdocs/Green/Energy.pdf>Heldmann, C. (n.d.). Kitchen Appliances - Induction Cooktops - Save Time andEnergy. Build Your Own House - Home Building. Retrieved March 20, 2011from <http://www.byoh.com/cookinggreen.htm>Induction Cooking Basics. (n.d.). Renseas Technology Europe. Retrieved February 17,2011 from <www.renesas.eu/media/applications/consumer_industrial/induction_cooking/Renesas_Induction_Cooking.pdf>Jarvis, D., et al. (1998) The Association of Respiratory Symptoms and Lung FunctionWith the Use of Gas for Cooking. European Community Respiratory Health Survey. ERJ, 11(3), 651-658.Kuse, K., et al. (2000). US Patent Number 6,080,975, Washington, DC: US Patent andTrademark Office. Retrieved on March 1, 2011 from <www.google.ca/patentshl=en&lr=&vid=USPAT6080975&id=_tUDAAAAEBAJ&oi=fnd&dq=induction+stove+kithen+temperature&printsec=abstract#v=onepage&q&f=true> EVALUATION OF INDUCTION STOVETOPS 20 Lawrence Berkeley National Laboratory. Volume 2: Potential Impact of Alternative Efficiency Levels for Residential Cooking Products. Berkeley, CA: U.S.Department of Energy. <http://www1.eere.energy.gov/buildings/appliance_standards/residential/pdf s/cooktsd.pdf>Melia, R.J., et al. (1977). Association Between Gas Cooking and Respiratory Diseasein children. British Medical Journal, 2(149).Saint, B. (2008). DOE Distribution Transformer Efficiency Standards. Retrieved onMarch 28, 2011 from <http://www.ieeerepc.org/documents/NRECADOEDistributionTransformerEfficiencyStandardsREPC.ppt>Scientific Committee on Emerging and Newly Identified Health Risks (2006).Preliminary Opinion on Possible effects of Electromagnetic Fields on HumanHealth. European Commission Directorate-General Health and Consumer Protection, Retrieved March 10, 2011 from <http://ec.europa.eu/health/ph_risk/committees/ 04_scenihr/docs/scenihr_o_006.pdf>Scientific Committee on Toxicity, Ecotoxicity, and the Environment (2001). Possibleeffects of Electromagnetic Fields (EMF), Radio Frequency Fields (RF), andMicrowave Radiation on Human Health. European Commission Directorate- General Health and Consumer Protection, Retrieved March 10, 2011 from<http://ec.europa.eu/health/ph_determinants/environment/EMF/out128_en.pdf>Seasoned Advice (2010). Induction Range vs Gas [discussion]. Retrieved March 15,2011 from <http://cooking.stackexchange.com/questions/5124/induction-range-vs-gas.>Sorensen, G., & Zabrowski, D. (2009, August). Improving Range-Top Efficiency withSpecialized Vessels. Appliance magazine, N/A. Retrieved February 6, 2011,from <http://www.appliancemagazine.com/editorial.php?article=2257&zone=114&first=1>Sustainable Foodservice Consulting (2011). Energy Conservation. Retrieved onMarch 20, 2011 from <http://www.sustainablefoodservice.com/cat/energy-efficiency.htm>Sze, M. (2006). Price of Natural Gas. The Physics Factbook. Retrieved on March 20,2011 from <http://hypertextbook.com/facts/2006/MichelleSze.shtml> EVALUATION OF INDUCTION STOVETOPS 21 The Induction Site, (2010). Induction Cooking. Retrieved March 20, 2011 from<http://theinductionsite.com/>The Middleby Corporation (2010). Innovation in Kitchen Energy Efficiency.Retrieved on March 20, 2011 from <www.greenstainless.com>Ulam, John B., “Induction Cooking Utensils,” US Patent 4646935, March 3, 1987.University of British Columbia Alma Mater Society (2010). New Sub Project 75%Schematic Design Report. Retrieved on March 1, 2011 from<mynewsub.com>


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