Declaration of originality

Transcription

1 Declaration of originality I certify that this is my own work, and it has not previously been submitted for any assessed qualification. I certify that the use of material from other sources has been properly and fully acknowledged in the text. I understand that the normal consequences of cheating in any element of an examination, if proven and in the absence of mitigating circumstances, is that the Examiners Meeting be directed to fail the candidate in the examination as a whole. Signed:.. Date:.. i

2 Abstract The current situation and prospects for small wind turbines (<50kW) in the UK urban environment are examined. Technical information was obtained from British and Irish manufacturers & designers of small wind turbines to assess the state of the art. The number & types of UK installations were collected, and a detailed questionnaire was designed and distributed to them. Models were created and information was collected to assess the economic viability. 31 turbines (including prototypes) were assessed, 92 installations were found of which 19 returned completed questionnaires, and economics for four situations were assessed in detail. The technology is promising, as are the experiences of wind turbine owners (although significant issues remain), but economic viability depends on a combination of factors including grants and good average wind speeds (the latter could be rare in the urban environment). The work was conducted with IT Power for the EC co-funded WINEUR project. ii

3 Executive summary This report examines the current situation and prospects for small wind turbines (<50kW) in the UK urban environment. It focuses on the state of the art, installations & installation experiences, and the economics. To assess the state of the art, technical information was obtained from all 16 British and 3 Irish manufacturers & designers of small wind turbines to assess the state of the art. There are 31 small turbines being manufactured or designed that could be installed in the urban environment, 18 of which are specifically marketed for it. There are no VAWTs currently being manufactured, but 7 are being designed for the urban environment. The turbines presently being manufactured are categorised: there are 6 micro HAWTs, 3 small HAWTs not aimed at the urban market, 4 small HAWTs aimed at the urban market, and 6 larger HAWTs. The latter two categories are aimed at the urban environment. A small wind turbine test centre would be useful to corroborate the data supplied by manufacturers, which would help in making objective technical comparisons of the turbines. The importance of a low cut-in wind speed of 2 or 2.5m/s where AMWSs (Annual Mean Wind Speeds) are 4m/s, and the energy a turbine theoretically loses if it cuts-out at 15m/s where AMWSs are 7m/s is demonstrated. Internet research revealed 92 installations of wind turbines in the urban environment in the UK. They are categorised according to who installed them (i.e. school or housing association), type of turbine, urban or semi-urban, and building-mounted or ground-based. Most of the installations are of Proven 2.5 and 6kW turbines, and they are mostly installed at schools or environment centres. A detailed questionnaire was created from scratch which covered sociological & technical aspects, barriers to installation, and economics. It was distributed to the installations found, and 19 responses were received. The results show that although turbine owners tend to have high levels of satisfaction, and that the perceptions of neighbours and the local communities significantly improved after the installations compared with before; a high proportion of owners have had technical problems with iii

4 their turbines, suffered from poor after sales service, and overrate the economics. The most significant obstacles to installation encountered were planning and connecting to the grid (neighbours and the local community had comparatively little effect). A significant proportion of those who responded had also depended on grants. Installed costs for the turbines are estimated based on data collected, and by /kw are found to approximately corroborate with the Clear Skies estimate of 2,500-5,000 per kw. Economic estimates for building-mounted installations are not significantly more expensive than ground-based installations for turbines of the same type. Initial economic modelling is completed for turbines at a school in Glasgow, a house in Reading, and the RIBA (Royal Institute of British Architects) and Aylesbury Estate buildings in London. The last three sites all have measured wind speed data which is why they have been chosen, because NOABL (a wind speed database widely used by the industry) does not make accurate predictions where the local topography has a large effect (e.g. in the urban environment). The economic analysis for the school is for ground-based turbines, for the London buildings building-mounted turbines, and for the house both kinds. The economics for all of the installations are found to be poor, apart from the Aylesbury Estate where a payback of 5 years could be achieved with a building-mounted Proven 6kW if 50% of installation costs are grant-funded and ROCs are collected. This is due to the high AMWS of 8m/s on the rooftops of the Estate s tower blocks. AMWSs in the other measured areas are much lower, 2.8m/s in central Reading, and 3.4m/s on RIBA s rooftop, and leads to paybacks >20 years. Installations in all the areas are shown to be predominantly sensitive to changes in wind speed, followed by level of initial investment, (other variables measured included ROCs, discount rate, and annual maintenance costs). The research has been carried out with IT Power as part of the EC-funded WINEUR project. This work focuses on the UK & Ireland, while the WINEUR project is covering technologies and the state of the market in Europe. iv

5 SMALL WIND TURBINES FOR THE URBAN ENVIRONMENT: STATE OF THE ART, CASE STUDIES, & ECONOMIC ANALYSIS TABLE OF CONTENTS Declaration of originality Abstract Executive Summary Table of Contents List of figures and tables Glossary of terminology Acknowledgements i ii iii v vii ix x Chapter 1 INTRODUCTION 1.1 Renewable energy & microgeneration targets Possible benefits of urban µgeneration, and small wind The WINEUR project Aims & objectives of this project 3 Chapter 2 METHODOLOGY 2.1 Methodology Note on references 5 Chapter 3 STATE OF THE ART UK & IRELAND 3.1 The urban wind regime HAWT vs. VAWT, lift vs. drag Building-mounting Categorising small wind turbines with respect to the urban environment State of the art summary Technical comparisons of similar turbines Power & efficiency comparisons on the small HAWTs aimed at the urban market Power & efficiency comparisons on the larger HAWTs The importance of low cut-in wind speeds Cut-out wind speeds Weight per swept area turbine robustness RPM (Revolutions Per Minute) & TSR (Tip Speed Ratio) 24 Chapter 4 UK INSTALLATIONS 4.1 Limitations to the study Installations found - results 4.3 The returned questionnaires 4.31 Demographics Turbine details Location type People s perspectives of the turbine Economics & lack of knowledge of turbine operators Reasons for installation Obstacles to installation 37 v

6 4.38 Turbine problems & after sales service With hindsight, would they install a small wind turbine again? Analysis of results Of all the installations found Of the returned questionnaires 40 Chapter 5 ECONOMICS 5.1 Methodology Estimated installed costs per kw e for turbines St. John Bosco School, Renfrewshire 5.4 A traditional house in central Reading, Berkshire 5.5 Large buildings in London RIBA, and the Aylesbury Estate 5.6 Analysis Chapter 6 CONCLUSIONS 61 REFERENCES 64 APPENDICES Appendix A Wind turbine details Appendix B Catalogue of wind turbines on the market Appendix C Catalogue of prototype wind turbines Appendix D Permanent magnet or induction generators? Appendix E Full list of known installations Appendix F Blank sample case study questionnaire Appendix G Raw questionnaire data Appendix H Additional installation results Appendix I The variables for economic analysis Appendix J Approximate installed turbine costs Appendix K Full installation costs for different turbines at John Bosco School Appendix L Important conversations and s Appendix M Economic questionnaires vi

7 List of figures and tables Figure 1 the HAWT categories and their rotor diameter...10 Figure 2 Power vs. wind speed for the small HAWTs aimed at the urban market 15 Figure 3 Power per m 2 of swept area vs. wind speed for the small HAWTs aimed at the urban market...15 Figure 4 Fraction of the Betz limit attained by the small HAWTs aimed at the urban market vs. wind speed...16 Figure 5 Power vs. wind speed for the larger HAWTs...17 Figure 6 Power per m 2 of swept area vs. wind speed for the larger HAWTs...17 Figure 7 Fraction of the Betz limit attained by the larger HAWTs vs. wind speed...18 Figure 8 kwh the D400 generates due to wind speeds in the bins of 3m/s and 3 & 4m/s at different AMWSs...19 Figure 9 Percentage of the total annual energy capture of the D400 due to wind speeds in the bins of 3m/s and 3 & 4m/s at different AMWSs...20 Figure 10 kwh the Proven 15kW generates due to wind speeds in the bins of 3m/s and 3 & 4m/s at different AMWSs...20 Figure 11 Percentage of the total annual energy capture of the Proven 15kW due to wind speeds in the bins of 3m/s and 3 & 4m/s at different AMWSs...21 Figure 12 - kwh the Proven 0.6kW and the Swift generate due to wind speeds in the bins 15m/s at different AMWSs...22 Figure 13 Percentage of the total annual energy capture that the Proven 0.6kW and the Swift generate due to wind speeds 15m/s or 20m/s at different AMWSs...23 Figure 14 Weight per swept area of the turbines...24 Figure 15 Locations of all 92 installed turbines...26 Figure 16 Turbine models chosen...27 Figure 17 Turbine models chosen...29 Figure 18 Locations of installed turbines...30 Figure 19 Owner s overall happiness with their turbine...31 Figure 20 Owner s rating of the visual appearance of their turbine...32 Figure 21 Neighbours and local communities perceptions before the installation 33 Figure 22 Neighbours and local communities perceptions after the installation...33 Figure 23 Owner s estimates of the turbine s paybacks...35 Figure 24 Reasons listed for installing the turbine...36 Figure 25 Owner s rating of the difficulty in overcoming obstacles...37 Figure 26 Estimated turbine installed costs in /kw...44 Figure 27 John Bosco School s turbine and its location...46 Figure 28 LPC sensitivity analysis for John Bosco School...48 Figure 29 Estimated LPCs for different turbines installed at John Bosco School...49 Figure 30 Map of central Reading...51 Figure 31 LPC sensitivity analysis for the installation of a Swift on a house in Reading...54 Figure 32 Map of RIBA s location in London...55 Figure 33 Map of Aylesbury Estate s location in London...56 Figure 34 LPC sensitivity analysis for a roof-mounted Proven 6kW on the Aylesbury Estate...59 vii

8 Table 1 the DTI s definition of microgeneration...1 Table 2 Advantages & disadvantages of HAWTs, Lift VAWTs, & Drag VAWTs...7 Table 3 Summary of manufacturers...11 Table 4 Turbines being manufactured for the urban environment...12 Table 5 Prototypes being 12designed for the urban environment...12 Table 6 Turbines on the market which are suitable for building-mounting 13 Table 7 Prototypes which should be suitable for building-mounting...13 Table 8 Breakdown of total number of installations...25 Table 9 Number of known rooftop installations...27 Table 10 Locations of installed turbines...28 Table 11 base case of the school for LPC sensitivity analysis...47 Table 12 estimated installed costs for turbines at John Bosco School...49 Table 13 Estimated economics of residential turbine installations in Reading...52 Table 14 Base case for residential Swift installation in Reading, for LPC sensitivity analysis...53 Table 15 Economics of roof-mounted turbines on RIBA & the Aylesbury Estate..57 Table 16 Base case for roof-mounted Proven 6kW on the Aylesbury Estate, for LPC sensitivity analysis...58 viii

9 Glossary AMWS Annual Mean Wind Speed BEAMA British Electrotechnical and Allied Manufacturers Association. With respect to microgeneration, they are interested in how exports could be metered. Betz limit Theoretical maximum limit to the amount of energy that can be extracted from an airflow, for either HAWTs or VAWTs. The limit is 59.3% of the energy in the wind. CREDIT Centre for Renewable Energy, at Dundalk Institute of Technology CREST Centre for Renewable Energy Systems Technology, at Loughborough University DTI Department of Trade and Industry EERU Energy and Environment Research Unit, at the Open University in Milton Keynes G59 & G83 grid connection standards. When a renewable energy generator connects to the grid, they must ensure that they meet these standards. GLA Greater London Authority HAWT Horizontal Axis Wind Turbine LPC Levelised Production Cost is the present cost of the energy from e.g. a turbine given the costs and income it provides over its lifecycle (normally assumed as a 20 year period). µgenerator (Microgenerator) DTI s definition, is: < 50kW e, or < 45kW heat, from a low carbon source. NOABL DTI database on estimates of AMWSs throughout Britain, to a 1km square 10, 25, or 45m above ground-level ODPM Office of the Deputy Prime Minister PPS22 Planning Policy Statement 22, issued by the ODPM. Guidance aimed at encouraging local planning departments to view renewable energy installations favourably. Rayleigh Wind speed distribution. Special case of the Weibull where the shape factor k = 2. The scale factor c depends on the mean wind speed, therefore the whole shape of the curve can be determined by the mean wind speed. ROC Renewable Obligation Certificate RPM Revolutions Per Minute (of the turbine s rotor) SCHRI Scottish Community and Household Renewables Initiative. This is essentially Clear Skies, but in Scotland. They seem to have more money to spend on projects than Clear Skies, and their website is more comprehensive. SEI Sustainable Energy Installations. A sister company of IT Power that conducts renewable energy installations. TSR Tip Speed Ratio VAWT Vertical Axis Wind Turbine Weibull Wind speed distribution. Shape of the curve depends on shape factor k, scale factor c, and the mean wind speed. ix

10 Acknowledgements I would like to thank my supervisor, Tim Cockerill, for his interest and excellent advice. Special thanks to Katerina Syngellakis, Project Engineer at IT Power, without whom this project would never have gone ahead, and whose project management skills and help were invaluable. Many other members of staff at IT Power were extremely helpful. Particularly Kavita Rai who analyzed some of the data of the installation questionnaires looking for trends (although most of her work is not included in this project), and Duncan Brewer whose knowledge and experience in the subject from an installer s perspective resulted in frequent conversations and much help & guidance. Thanks also to Sarah Davidson and Warren Hicks for their knowledge, and Rolf Oldach for his knowledge of roof-mounting turbines. The resources that were already available at IT Power the library of knowledge around the office and on their computer system collected through their years of work was invaluable. My fellow MSc student from Loughborough University, Steve Carroll, who was working in parallel with me on the project was also of great helping in broadening my knowledge of the subject, providing frequent conversations, and solicit responses to the case study questionnaire. I would also like to thank the other members of the WINEUR project primarily for designing the technical questionnaire which I utilized for obtaining technical data on the turbines, and also for their research into the wind turbines and state of the market in other countries around the world, that helped me to gauge the UK s global position in this field. They also provided the principal economic questionnaire, which I used to interview manufacturers, and Steve Carroll and I modified to send to case studies. x

11 1. INTRODUCTION 1.1 Renewable energy & microgeneration targets Britain has a target to source 10% of its electricity from renewables by 2010, and aspires to source 20% by Although the Energy White Paper assumes this will mostly be met by large-scale wind turbines, it also believes that microgeneration will provide an important contribution and is worth pursuing. (DTI, 2003) Some local planning authorities Unitary Development Plans (so far Merton, Croydon, and North Devon) now demand that a percentage of energy for all major developments 1 must be sourced from onsite renewables (SolarCentury, 2005a). Influence from National planning document PPS22 (ODPM, 2004a) and the Greater London Authority (GLA, 2004) is strongly encouraging other Local Authorities to follow suit. 2 Small wind generators are already being used to meet these local targets (Merton 2004, and SolarCentury 2005b). Table 1 the DTI s definition of microgeneration For heat, < 45 kw For electricity, < 50 kw e Low net carbon emissions (Resouce05, 2005) The DTI also call microgeneration µgeneration. This is convenient, and hereon it is used in this project. 1 Definition of a major development. With dwellings: >10 or total area > 0.5 hectares. Other uses: floor space >1,000m 2, or site > 1 hectare. (Solar Century, 2005a) 2 The Energy Performance of Buildings Directive, when it comes into force, may also have some impact (ODPM 2004b), but it remains to be seen how much. 1

12 1.2 Possible benefits of urban µgeneration, and small wind This research is worthwhile because of the possible benefits of urban µgeneration. They can be summarised as: 1. Additional untapped source of renewable energy 2. At point of use and thus eliminating transmission losses 3. Potentially leading to strengthening of the grid (Martin Bradley conversation, 24/5/05) and distribution networks (DTI, 2005), reducing the need for upgrades 4. Raises awareness of sustainability In addition, compared to the other µgeneration technologies wind is among the most economic where wind speeds are reasonable (DTI 2005), and will probably have a higher Energy Payback Ratio (EPR) and emit less CO 2 over its lifecycle (Boyle et al. 2003, Resource ). Depending on where it is sited, it can be highly visible making it very appropriate for making a green statement or raising awareness. Small wind can also complement PV because it generates most of its energy in the winter, while PV generates most of its energy in the summer. (SolarCentury, 2005b) 1.3 The WINEUR project Despite the relative potential importance of small scale wind generation in urban areas, there is as yet very little comprehensive information on the subject, covering both building-integrated and mast-mounted installations. The EC co-funded WINEUR project (Wind Integration in the Urban Environment) will fill this information gap by collecting, analysing and disseminating information on the technical, economic, planning, policy, and sociological aspects of small wind energy for the urban environment. One of the main aims of the project is to provide comprehensive information that will encourage the further development of urban wind µgeneration. More information on the WINEUR project is available at the project website 2

13 1.4 Aims & objectives of this project This report covers the following work that forms part of the WINEUR project: Aims 1. Cover the state of the art of turbines being manufactured and designed in the UK & Ireland 2. Assess the situation with regards to installations, and analyse detailed experiences of wind turbine owners & operators 3. Analyse the economics Objectives 1. Technology inventory for the UK & Ireland, containing technical details and comparing technologies 2. UK installations assessment, estimating the number and kinds of installations, and analysing some detailed experiences 3. Economic assessment, of the viability of small wind turbines in urban areas By itself, this work is sufficient to give an insight into the state of urban wind in Britain today. It is worth noting that the UK is among the most advanced countries in the world in this field. Only the Netherlands and Japan are on a comparable level with regards to developing urban wind turbines and attempting roof-mounted installations. (WINEUR, 2005) 3

14 2. METHODOLOGY 2.1 Methodology To obtain technical details on the British & Irish turbines suitable for the urban environment: 1. Adapted & utilised a standard technical questionnaire prepared by the WINEUR partners to interview manufacturers & designers of small wind turbines (in addition to the questionnaire answers comprehensive notes were made on any additional comments) 2. Going beyond the requirements of WINEUR, the turbines were then split into broad categories depending on their intended use (i.e. urban or non urban) and design (power, rotor diameter, and axis), and then analysed & compared To summarise the situation with regards to urban installations, and find some detailed experiences: 1. Researched installations using the internet. Useful websites included: Clear Skies, SCHRI, Wind & Sun, EcoArc, Community Environmental Networks (CEN), SEE Stats, BWEA, Action Renewables, and BBC. Ensured installations identified were urban by locating them on a map. 2. Some analysis of these known urban installations was made popularity of types of turbine, who are installing them, percentage which are roof-mounted. 3. Created a standard questionnaire from scratch for distribution to small wind turbine owners & operators. Covering sociological, technical, and economic aspects. 4. Input the data received into a spreadsheet, and analysed it with regards to the sociological, technical, and economic aspects. Kavita Rai of IT Power also used specialist to make further comparisons according to my suggestions (and some of her own). This second task provided some valuable information for the sociological and economic aspects of the WINEUR project. 4

15 To analyse the economics: 1. Utilised a standard economic questionnaire prepared by the WINEUR partners to interview turbine manufacturers. 2. Modified the questionnaire, and ed it to those who had returned installation questionnaires and who had agreed to answer further economic questions. 3. Utilised economic data from the returned case study questionnaires, & other sources 4. Obtained a spreadsheet of 151 turbine installations (economic breakdown, AMWS, and generation estimates) made through the Clear Skies program. 5. Accessed economic information from the case studies available on the SCHRI and Clear Skies websites, and the other studies available. 6. Obtained AMWS data 7. Utilised the turbine power curves obtained from the turbine manufacturers, with AMWS estimates & a Rayleigh distribution to produce generation estimates. Further details on the methodology are in Chapter 5 below. 2.2 Note on References As much of the research completed was first-hand, many of the references are discussions and s with people. These references are contained in Appendix L in the back of the project, and they are referred to with the name of the person communicated with, the way the communication was made (i.e. conversation or ), and the date. In Appendix L they are ordered by date. 5

16 3 STATE OF THE ART UK & IRELAND 3.1 The urban wind regime Two things particularly characterise the urban wind regime lower AMWSs (Annual Mean Wind Speeds) compared to rural areas, and more turbulent flow. The lower AMWSs are caused by the rough uneven ground (i.e. a higher roughness length z 0 ) which causes wind to increase with height more slowly. The turbulent flow is a result of the wind interacting with the buildings. Despite the advantages in bringing local wind generation to cities, the low AMWSs and turbulent flow have discouraged many people who may otherwise have been interested, as wind economics are totally dependent on the available resource. (Gipe, 2004) Turbulent flow presents challenges in two ways rapidly changing wind direction, and buffeting the turbine blades. The options are to find a machine that copes well with turbulence, or to find the least turbulent areas of the urban environment. Of the latter, building-tops could show a great deal of promise, partly because the wind flow there could be substantially greater as it gets concentrated by passing around the building. Other less turbulent areas are open areas on the ground such as school playing fields or parks. 3.2 HAWT vs. VAWT, and lift vs. drag There is some debate about which of the different kinds of turbine are most suitable for the urban environment, which would be best for building-mounting, and even whether building-mounting is a good idea. The advantages and disadvantages of the main different designs of machine are summarised in table 2 below. 6

17 Table 2 Advantages & disadvantages of HAWTs, Lift VAWTs, & Drag VAWTs HAWTs Lift VAWTs Drag VAWTs Advantages 1. Efficient 2. Proven product 3. Widely used 4. Most economic 5. Many products available 1. Quite efficient 2. Wind direction immaterial 3. Less sensitive to turbulence than a HAWT 4. Create fewer vibrations Disadvantages 1. Does not cope well 1. Not yet proven with frequently 2. More sensitive to changing wind turbulence than direction drag VAWT 2. Does not cope well with buffeting (Randall 2003, Timmers 2001, and Clear Skies 2003) 1. Proven product (globally) 2. Silent 3. Reliable& robust 4. Wind direction immaterial 5. Can benefit from turbulent flows 6. Create fewer vibrations 1. Not efficient 2. Comparatively uneconomic An unmodified HAWT will work well where the air flow is less turbulent, on top of high buildings or near open spaces, but in more turbulent areas HAWTs would need to be made robustly in order to cope with blade-buffeting. Detrimentally, this will increase the turbine s weight and cost (John Balson conversation, 18/5/05). In fact, many of the HAWTs aimed at the urban market are heavy with respect to surface area, probably for this reason. However this would not solve the issue of them being unable to orient themselves quickly enough to catch all the energy when the wind direction is prone to change frequently. 7

18 Other, less certain issues are that: 1. Lift VAWTs may not be able to cope with strong turbulence either, because they also rely on lift and so their blades would frequently stall (Ken England conversation, 19/5/05) 2. VAWTs should be easier to maintain, as the generator is below the rotor, normally on the ground. (Timmers 2001 & Clear Skies 2003) 3.3 Building-mounting Some respected people within the small wind turbine industry such as Paul Gipe and Mick Sagrillo are against rooftop mounting. They are concerned over vibrations being transmitted to the structure, and the turbulence caused by the roof. (Gipe, 2003) In addition, Larry Staudt (formerly Engineering Manager of Enertech) found that it was very difficult to get a rotor diameter on a roof big enough to get a significant amount of power. (Larry Staudt conversation, 19/5/05) Indeed, structural integrity due to vibrations and dynamic loads is a significant current concern in building-mounting turbines. Hiring a structural engineer to assess the suitability of the buildings is a major cost, as is altering the structure (e.g. by adding steel frames). (Rolf Oldach conversation 16/6/05, Clear Skies 2003) In addition, Gipe, Sagrillo, & Staudt s experiences are predominantly with HAWTs, and VAWTs create less vibrations, exert smaller dynamic loads on the building, and can cope better with turbulence. (However, they are also currently less economic.) (Clear Skies, 2003) Advantages of building-mounting are: potentially much higher wind speeds (depending on relative height of the building compared to surrounding buildings see Chapter 5 below) less turbulence 8

19 3.4 Categorising small wind turbines with respect to the urban environment For the purposes of this report small wind turbines are placed into five principal categories: micro HAWTs small HAWTs not aimed at the urban market small HAWTs aimed at the urban market larger HAWTs VAWTs The definitions of these categories are as following: Micro HAWTs very small HAWTs designed and marketed for remote locations or boats, which in normal conditions would produce too little power to noticeably reduce an ordinary domestic (or other) electricity bill. 3 In addition, G83-certified inverters that could grid-connect the tiny amounts of power they produce cost more than the turbines in August (Peter Anderson conversation, 9/8/05) Small HAWTs not aimed at the urban market HAWTs that would produce a significant amount of power, but are still aimed at remote locations. Small HAWTs aimed at the urban market HAWTs that are designed & marketed for the urban market and should produce enough power to noticeably reduce a normal domestic (or other) electricity bill. Larger HAWTs the larger HAWTs with a rotor diameter >2m, aimed at either the urban or rural markets. VAWTs currently, the VAWTs can all be conveniently grouped together. 3 Gipe defines micro turbines as being those with a rotor diameter of under 1.25m (Gipe, 2004), which correlates with this definition. 9

20 Figure 1 the HAWT categories and their rotor diameter 12 1 = Micro HAWTs 10 2 = Small HAWTs not aimed at the urban market 3 = Small HAWTs that are aimed at the urban market 4 = Larger HAWTs Rotor diameter, m Turbine type Figure 1 above compares the categories of the HAWTs, with the rotor diameters of the turbines, to see if there is any correlation. Category 3 overlaps slightly with categories 1 and 2 because it is primarily defined by the fact that these turbines are aimed at the urban market, and not by their rotor diameter. 3.5 State of the art summary There are 11 companies (2 of which are Irish) manufacturing 19 small wind turbines (all HAWTs). There are 12 organisations (1 of which is Irish) designing and developing small wind turbines (5 HAWTs & 7 VAWTs). Of these 12, 4 are also manufacturers, so 19 organisations in total are either manufacturing or designing 31 small wind turbines, all of which could theoretically be placed in the urban environment. The proven products that generate a substantial amount of energy and are available now for the built environment are the larger HAWTs made by Proven, Iskra, and Gazelle. These products are almost always ground-based, with the exception of Proven who have recently started building-mounting their turbines. Other proven products that could be used in the urban environment are the micro HAWTs, although they generate so little power their applications would be limited. Products which are just emerging (or have emerged recently) onto the market which are specifically intended to be building-mounted on domestic properties (and other 10

21 buildings) are the small HAWTs aimed at the urban market made by Eclectic Energy, Renewable Devices, and Windsave. (There is one other recent product in this category Surface Power s turbine but it can t be building-mounted.) There are no VAWTs currently on the market, 4 but many VAWTs designed for the built environment (and that should be suitable for building-mounting) are prototypes currently being tested, and should be available in 2006/2007. Table 3 below summarises the different companies, the categories of turbines they manufacture, and how long they have been manufacturing them for. Table 3 Summary of manufacturers Turbine type Company Years manufacturing, in 2005 Micro HAWTs Small HAWTs not aimed at the urban market Small HAWTs that are aimed at the urban market Larger HAWTs Marlec LVM Ampair Marlec Atlantic Power Master (Irish) Eclectic Energy Surface Power Technology (Irish) Windsave Renewable Devices Iskra Proven Gazelle > > (other turbines) 5 This year This year This year This year 14 7 (George Durrant 8/7/05, Marlec 2005, LVM 2005, Atlantic Power Master 2005, Eclectic Energy 2005, Surface Power Technology 2005, Windsave 2005, Renewable Devices 2005, Iskra 2005, Proven 2005, MKW 2005) 4 Although Ampair used to make a Savonius VAWT for boats called the Dolphin, it was withdrawn due to its extremely low efficiency and power rating. (George Durrant conversation, 16/5/05) 5 Meaning that Eclectic Energy have been making a product which is both wind & water turbine for use on boats for at least 3 years. However, their new urban wind turbine product is new in

22 Tables 4 & 5 below summarise the turbines currently being directed at the urban environment. In table 5, some turbines may be unfairly excluded, due to a lack of knowledge. Table 4 Turbines being manufactured for the urban environment Model & Rated Manufacturer power, kw D400 (Eclectic 0.4 Energy) Surface Power 0.46 Technologies Windsave 1 Swift (Renewable 1.5 Devices) Proven WT Proven WT Iskra 5 Proven WT Proven WT Gazelle 20 Table 5 Prototypes being designed for the urban environment Model & Rated designer/developer power, kw CREDIT Rugged Renewables Eurowind FreeGEN Posh Power Swift, smaller version (Renewable Devices) XCO2 Wind Dam Many (1.3 to 30) Unknown ~2-2.5 Unknown 6 2 (also in stackable modular design) (Resource , (Larry Staudt conversation 19/5/05, John Quinn 21/5/05, Ken England conversation 19/5/05, Renewable Devices 2005, Eurowind 2005, Posh Power 2005, Iskra 2005, MKW 2005) Richard Cochrane conversation 11/7/05, Julie Trevithick conversation 16/5/05) (Although some turbines are being manufactured for the urban environment and others are not, it is possible that any of them can be found in the urban environment somewhere.) From table 4 it can be seen that the three most experienced manufacturers of small turbines in Britain & Ireland Marlec, LVM, & Ampair presently show no interest in the urban market. This is due to poor wind conditions, and the tiny amounts of power their products produce. (Graham Hill conversation 13/5/05, George Durrant conversation 16/5/05, & Stuart James conversation 18/5/05) 12

23 All the turbines in table 4, and the CREDIT & smaller Swift turbines in table 5 are HAWTs, which should therefore be designed in a robust manner. All the other turbines in table 5 are VAWTs. Of the turbines being made for the urban environment, tables 6 and 7 list those aimed at building-mounting. Table 6 Turbines on the market which are suitable for buildingmounting Model & Rated Manufacturer power, kw D400 (Eclectic 0.4 Energy) Windsave 1 Swift (Renewable 1.5 Devices) Proven WT600?? Proven WT Proven WT Proven WT15000?? 7 15 Table 7 Prototypes which should be suitable for building-mounting Model & Rated designer/developer power, kw Rugged Renewables Eurowind Swift, smaller version (Renewable Devices) XCO2 Wind Dam 0.4 Many (1.3 to 30) Unknown 6 2 (also in stackable modular design) (Resource , (Ken England conversation 19/5/05, Renewable Devices 2005) Richard Cochrane conversation 11/7/05, Julie Trevithick conversation 16/5/05, Eurowind 2005) As can be seen from table 6, Surface Power Technologies are absent due to their concern about vibrations (Jenny , 11/7/05). Iskra are absent as although they are interested they believe they would need to design a new turbine, and they are not in table 7 as it seems this has not begun yet (John Balson conversation, 3/6/05). Gazelle s intentions are not certain, but their turbine is probably too big. In table 7, CREDIT are absent due to their concerns over generating enough energy and vibrations (Larry Staudt conversation, 19/5/05), while FreeGEN and Posh Power have been removed as it is not clear if they are intending for their turbines to be 6 Although there are no known examples involving the Proven 0.6kW, it probably could be as the larger 2.5 & 6kW Provens are being building-mounted. 7 Proven haven t excluded the possibility of building-mounting their 15kW turbine, but it has not been done yet, and it has not been possible to confirm that any installations will go ahead. 13

24 building-mounted. Apart from the smaller Swift, all of the turbines in table 7 are VAWTs. For individual descriptions of the turbines see Appendix A. For pictures and technical details of the turbines, please see the catalogues Appendices B and C. 3.6 Technical comparisons of similar turbines This section will focus on the turbines being aimed at the urban market - the small HAWTs being aimed at the urban market, and the larger HAWTs. The machines that are being designed and developed will not be analysed, as their technical specifications (where available) will probably change. As mentioned at the beginning of Appendices B & C, there is a need for a small wind turbine test centre, that will test and independently verify the technical data supplied by manufacturers. This is particularly the case with data such as power curves Power & efficiency comparisons for the small HAWTs aimed at the urban market Power curve data for the Windsave is still classified in August 2005, so it can t be compared. 14

25 Figure 2 Power vs. wind speed for the small HAWTs aimed at the urban market 1600 D SPT Sw ift 1200 Power (W) Wind speed (m/s) Given that the Swift is rated at 1.5kW, while Surface Power s turbine is rated at 0.46kW and Eclecitc s D400 at 0.4kW, it is not surprising that in figure 2 the Swift is shown to produce far more energy than the other two turbines at all wind speeds. Power per m2 of swept area (W/m2) Figure 3 Power per m 2 of swept area vs. wind speed for the small HAWTs aimed at the urban market 600 D400 SPT 500 Sw ift Wind speed (m/s) 15

26 It is much more interesting to compare the products by power per m 2 of swept area as in figure 3. Surface Power s turbine cuts-in at a lower wind speed, but the turbines are broadly similar until 7 and 8 m/s, when the Swift is shown to produce the most power/m 2, followed by the D400, and lastly by Surface Power s. Figure 4 Fraction of the Betz limit attained by the small HAWTs aimed at the urban market vs. wind speed 1.8 D400 Fraction of Betz limit attained 1.6 SPT Sw ift Wind speed (m/s) Figure 4 shows how all three turbines apparently break the Betz limit at 3m/s, but the Swift is notably for extravagantly breaking the Betz limit at 4 and 5m/s. For many of the other wind speeds it is also extraordinarily efficient, while this is also the case for the D400 at 6m/s and below. The Swift has a ring around it, which could partially concentrate the airflow (Larry Staudt conversation, 19/5/05) or reduce blade tip losses but as it is only a few inches wide (see picture in Appendix B) it is more likely that the power curve supplied is erroneous Power & efficiency comparisons on the larger HAWTs It should be noted that the power curve data for the Gazelle is based on very old data, and derived theoretically. (Garry Jenkins , 12/7/05) Therefore it may not represent the machines actual performance in the field very well. 16

27 Power (W) Figure 5 Power vs. wind speed for the larger HAWTs Proven 0.6kW Proven 2.5kW Iskra 5kW Proven 6kW Proven 15kW Gazelle 20kW Wind speed (m/s) In figure 5 above, it can be seen that the turbines generate quite different amounts of power. The most comparable machines are the Iskra 5kW and the Proven 6kW. Power per swept area (W/m2) Figure 6 Power per m 2 of swept area vs. wind speed for the larger HAWTs Proven 0.6kW Proven 2.5kW Iskra 5kW Proven 6kW Proven 15kW Gazelle 20kW Wind speed (m/s) In figure 6 above, the Proven 0.6kW stands out for producing the least power/m 2, and the Gazelle the second least amount, for wind speeds 5m/s. It is difficult to differentiate the other four turbines, except 13m/s where the Proven 2.5kW is sharply ahead. 17

28 Fraction of Betz limit attained Figure 7 Fraction of the Betz limit attained by the larger HAWTs vs. wind speed Proven 0.6kW Proven 2.5kW Iskra 5kW Proven 6kW Proven 15kW Gazelle 20kW Wind speed (m/s) As might be expected from figure 6, in figure 7 the Proven 0.6kW is predominantly the least efficient, followed by the Gazelle. This is the case except where wind speeds are 4m/s, where the Proven 0.6kW is more efficient than the Gazelle. All the other turbines are broadly similar. It is interesting to compare this figure with figure 4 for the small HAWTs being aimed at the urban market none of these turbines break the Betz limit, or have such extraordinary efficiencies for such wide bands of wind speed. This indicates again that the power curves for the smaller HAWTs could be erroneous, especially for the Swift The importance of low cut-in wind speeds Figures 8, 9, 10, and 11 below demonstrate the importance of a low cut-in wind speed at different AMWSs, for two machines Eclectic s D400 and the Proven 15kW. These machines have been chosen because they are of completely different sizes. The D400 cuts-in at ~2m/s, the Proven 15kW at 2.5m/s, and they first generate measurable amounts of energy at 3m/s. A Rayleigh distribution assigns probabilities that the wind will have different wind speeds given the AMWS. It splits the range of wind speeds into different wind speed 18

29 bins, of 1, 2, 3, etc. m/s. These probabilities can be multiplied by the number of hours in a year to assess the number of hours in a year that the wind speed will blow at that wind speed, given the AMWS. These figures can then be multiplied by a turbine s power curve, to give an estimate for a turbine s annual energy generation. Figures 8 and 10 compare the energy that the turbines generate due to wind speeds in the bins of 3 and 3 & 4 m/s, while figures 9 and 11 show the percentage that wind speeds in these bins contribute to the total annual energy capture. So these graphs show how much energy these turbines would lose if they cut-in at higher wind speeds. Figures 8 and 10 correlate approximately with money lost (approximately due to complications with ROCs, see Chapter 5, but as a rough method use 0.06/kWh). Figures 9 and 11 show the percentage of total annual energy capture that would be lost. For the D400 Figure 8 kwh the D400 generates due to wind speeds in the bins of 3m/s and 3 & 4m/s at different AMWSs 60 At 3 m/s Energy generated per year, kwh 50 At 3 & 4 m/s AMWS, m/s 19

30 Figure 9 Percentage of the total annual energy capture of the D400 due to wind speeds in the bins of 3m/s and 3 & 4m/s at different AMWSs Percentage of annual energy generation, % At 3 m/s At 3 & 4 m/s AMWS, m/s Proven 15kW Figure 10 kwh the Proven 15kW generates due to wind speeds in the bins of 3m/s and 3 & 4m/s at different AMWSs Energy generated per year, kwh 3000 At 3 m/s 2500 At 3 & 4 m/s AMWS, m/s 20

31 Percentage of annual energy generation, % Figure 11 Percentage of the total annual energy capture of the Proven 15kW due to wind speeds in the bins of 3m/s and 3 & 4m/s at different AMWSs AMWS, m/s At 3 m/s At 3 & 4 m/s In summary, from figures 8-11 above, a low cut-in wind speed would make a noticeable difference to the annual energy capture for AMWSs 4m/s, and a crucial difference with AMWSs 2m/s. There may be many settings in the urban environment with such small AMWSs (see Chapter 5). Also, as turbines with induction generators require a gearbox, which results in a higher cut-in wind speed (see Appendices A & D), they should be avoided where AMWSs are very low. However, there is a question of whether the Weibull distribution is an accurate representation of wind regimes in the urban environment. And it may not be, according to Tim Cockerill of Reading University Cut-out wind speeds None of these wind turbines have a cut-out wind speed, apart from the Windsave which cuts-out at ~15m/s, and the Gazelle which cuts-out at 20m/s. It is possible to theoretically compare a turbine to what it s energy capture might be like if it did not cut-out by taking the power curves of wind turbines which don t 21

32 cut-out, and seeing how much of the annual energy capture at different AMWSs is generated by wind speeds at and over those cut-out wind speeds. Figure 12 below tries to estimate how many kwh the Windsave 1kW is losing by cutting-out at 15m/s, by using the power curves of its nearest equivalents in terms of rated power the Proven 0.6kW and the Swift 1.5kW. (Recall that Windsave s power curve is not currently available.) The amount of energy that the Windsave theoretically loses should lie somewhere between the curves for the two turbines. Figure 13 below tries to estimate what percentage of the annual energy capture these turbines are losing. The Swift & Proven 0.6kW >15m/s curves should be useful to make estimates for the Windsave. The Gazelle is more difficult given that it cuts-out at 20m/s, and only one power curve is available which extends for wind speeds beyond this the Swift s. Therefore, the Swift >20m/s curve is used to make an estimate for the Gazelle. The graphs show that a cut-out wind speed of 15m/s only makes a significant difference to the annual energy generated at AMWSs 7m/s, while a cut-out of 20m/s only makes a difference where AMWSs 9m/s. Figure 12 - kwh the Proven 0.6kW and the Swift generate due to wind speeds in the bins 15m/s at different AMWSs Energy that would be lost annually, kwh 2500 Swift Proven 0.6kW AMWS, m/s 22

33 Figure 13 Percentage of the total annual energy capture that the Proven 0.6kW and the Swift generate due to wind speeds 15m/s or 20m/s at different AMWSs Percentage of annual energy capture that would be lost, % Swift, 15m/s & greater Proven 0.6kW, 15m/s & greater Swift, 20m/s & greater AMWS, m/s 3.65 Weight per swept area turbine robustness This is a way of estimating a turbine s robustness. Sagrillo says that engineers design turbines for survival wind speeds on paper, but rarely test the machines at these speeds. Besides, a wind turbine is more likely to be destroyed by turbulence than survival rated wind speeds. Therefore, he recommends that one divides the weight of the full rotor/nacelle assembly, with the swept area. Lightweight turbines can t handle sites with strong winds or turbulence. Heavyweight turbines should last longer, but are more expensive. (Sagrillo, 2002) His approximate rule is: >10 kg / m 2 = heavyweight 5-10 kg / m 2 = medium weight <5 kg / m 2 = lightweight (Sagrillo, 2002) It should be noted that as Sagrillo s experience is limited to HAWTs, so is the analysis below. 23

34 Weight/swept area figures for all the HAWTs are in Appendices B & C, and none of the machines lightweight, and only two are medium weight Surface Power Technologies turbine and Windsave s. Therefore they may not cope as well at a turbulent or very windy site as the rest. Figure 14 below compares the weight per swept area for the turbines being manufactured which are aimed at the urban environment Figure 14 Weight per swept area of the turbines Weight per swept area, kg/m D400 Surface Power Windsave Swift Proven 0.6kW Proven 2.5kW Iskra Proven 6kW Proven 15kW Gazelle 3.66 RPM (Revolutions Per Minute) & TSR (Tip Speed Ratio) Although a high RPM/TSR makes a turbine noisier, and more prone to wear & tear, (Sagrillo 2002), there is only RPM data for a few turbines not enough to make comparisons with. 24

35 4. UK INSTALLATIONS For this section as many examples of small & micro urban wind turbine installations in the UK were found as possible. The research was mainly conducted on the internet. 4.1 Limitations to the study There can only be an approximate relationship between the frequency with which installations have been detected on the internet, and their actual occurrence in the field. Some organisations are more likely than others to highlight that they have wind turbines on the internet e.g. schools & environmental centres, while individual householders are unlikely to do this. So there is a bias towards some kinds of installations, and against others such as domestic installations and turbines aimed at that market like: the D400, Surface Power s, and the Windsave. The extent of the effect of these biases on the present work is unknown. 4.2 Installations found Results Table 8 Breakdown of total number of installations <0.5kW 80kW >0.5kW & <50kW Total Planned Built Total Appendix E contains a full list of the installations. It should be noted that some examples will have been inevitably missed during the research for this report (due to the limited time available). Therefore, at a minimum there could be 100 installations in total. 91 turbines fit our definition of a µgenerator (excluding the 80kW turbine). Of the 21 (23%) which have not been installed yet it is known that 9 will imminently start building, 2 require planning permission, and 1 requires fundraising there is no detailed information on the state of progress of the other 9. 25

36 Case studies have been split among urban and semi-urban, which were loosely defined as follows: Urban where a turbine appears to be in or within 1 km of a densely populated area (town or city). Semi-urban where a turbine appears to be in or within 500m of a less populated area (e.g. tightly-knit village, but not a loose scattering of houses). Of the 92 installations, 71 are urban (77%), and 21 semi-urban (23%). Figure 15 below shows that 31 of the installations are schools & colleges (34%), and 21 are environmental centres of some type (23%). Number of installations Figure 15 Locations of all 92 installed turbines Government research lab Housing Association properties Universities Community centres (non enviro) Local Authorities Individual domestic properties Where installed Private companies Environmental centres Schools & Colleges Figure 16 below shows all the kinds of wind turbines that have been chosen to be installed. Where more than one model of turbine was chosen at a site, this is represented. But if more than one turbine of a model was installed at a site, this is not represented and counts as one. The idea of the graph is to gauge the popularity of turbines among people choosing them. As most of the installations are of one turbine, it would correlate quite well with a graph of the total number of turbines. The most popular turbine is the Proven 6kW, followed by the Proven 2.5kW. 26

37 Two wind turbines are notably absent the Proven 0.6kW, and Surface Power Technologies. No. of times chosen Aerodyn Wind Dam Lagerwey 80kW Figure 16 Turbine models chosen Wind Harvester 60kW Wind Harvester 45kW Eoltec Wind Runner Ropatec Windside Ampair Eclectic's D400 Jacobs Type of turbine chosen Proven 15kW Iskra Windsave Gazelle Proven unknown Marlec Swift Proven 2.5kW Unknown Proven 6kW Table 9 shows that rooftop installations represent 27% of the 92 installations. (22 of them are urban.) Table 9 Number of known rooftop installations Built Planned Total The returned questionnaires Most of the built installations above were contacted, and asked to complete a case study questionnaire. An example case study questionnaire is in Appendix F. 19 responses were received out of a possible 71, which is a response rate of 27%. The raw data of the questionnaires is in Appendix G. 27

38 There are some limitations to the responses received. The accuracy of the answers can only be as good as the knowledge of the person responding. Some of the responses were obviously inaccurate, e.g. with payback times, and generation estimates. Where identified, inaccuracies have been taken account of. There are only a limited number of conclusions that can be drawn with 19 responses. With more responses, perhaps more trends would be apparent. Kavita Rai s work consisted of cross-tabulating many results. A selection of these are shown in the section below and Appendix H, however the majority of them did not show any correlation and due to the size of her work it has not been included as part of this report Demographics Turbine locations Table 10 Locations of installed turbines Frequency Percent School College Environment centre Local Authority Environment centre and University Environment centre and Local Authority School and Local Authority Other Total Kavita Rai, IT Power, 2005 As would be expected, the case studies are dominated by educational establishments (42%), and environment centres (37%). Local authorities own 4 of the sites above (21%). The remaining 4 ( other ), are: a housing association, a charitable organisation, and 2 businesses. 28

39 Environmental consciousness One person wasn t able to reply on behalf of their organisation, but of the rest 13 thought their organisation was very environmentally conscious (72%) and 5 thought it was fairly environmentally conscious (28%). An option nobody selected was indifferent to the environment Turbine details Wind turbines chosen Figure 17 below broadly correlates with figure 16 above. The most popular turbines are still the Proven 6kW & 2.5kW. 7 Figure 17 Turbine models chosen 6 No. of sites at which chosen Ropatec Jacobs Lagerwey 80kW Proven 15kW Marlec 910F Gazelle Proven 2.5kW Proven 6kW Turbine choice Number of installations Of the 19 sites, 15 had only one turbine (79%), two had two, one had three, and one had four. 29

40 Ground or roof-mounted, and open space 17 of the responses (89%) were from ground-based turbines, but Heeley City Farm has a wall-mounted Marlec 910F (as well as a ground-based Proven), and Bradford West City Community Housing Trust has at least 2 Ropatecs on the roof of a residential tower block (see Clear Skies 2003) Location type 5 Figure 18 Locations of installed turbines 4 Frequency Dense inner-city Typical town/city residential area Industrial development Commercial development Small town Suburban Village Country park Type of area 6 of the installations (32%) are in a village/country park, and can be considered as semi-urban. 30

41 4.34 People s perceptions of the turbine Owner satisfaction Frequency Figure 19 Owner s overall happiness with their turbine Very happy Happy Ambivalent "Awaiting results" Overall happiness with turbine Unhappy Very unhappy One person was not able to answer the question above on behalf of their organisation. This result is a good sign for the small wind industry. 14 people (78%) are happy or very happy with their turbine. The people who were ambivalent, awaiting results, and very unhappy, had all had problems with their turbines (the latter have had severe and ongoing problems). The ambivalent owns a Proven 6kW, awaiting results a Proven 15kW, and the very unhappy people own a Gazelle and Jacobs turbines. The very happy people own a Gazelle, Lagerwey, Proven 6kW, and two of them own Proven 2.5kW s. Three of them had also had problems with their turbines, although only two of the happy people had had turbine problems. 31

42 Owner s feeling of visual appearance of turbine One person felt unable to answer this question on behalf of their organisation. Frequency opinion expressed Figure 20 Owner s rating of the visual appearance of their turbine 0 Beautiful Pretty Okay Quite ugly Very ugly Owner's rating of turbine's visual appearance 12 people (67%) felt indifferent about their turbine s visual appearance, 5 were positive (28%), and only one was negative. A Gazelle, Proven 6kW & Proven 2.5kW were all rated as beautiful, while the Jacobs and Marlec were rated as pretty. The Proven 15kW was described as quite ugly. Of course, these opinions are highly subjective. Safety Out of the 19, 6 rated their turbine as very safe (32%), 12 rated it as safe (63%), and the last rated his 5 year-old Gazelle as about acceptable. Owner s perception of the turbine s noise level With the limited data there is very little correlation between the turbine type or location as shown in Appendix H. 32

43 Change in neighbours and local communities perceptions Opinions of the neighbours and local communities overwhelmingly veered towards the positive after the installation compared with before, only a few stayed the same, and none became negative. Two people were not able to answer these questions, and one simply said that for both groups opinion varied before & after. Figure 21 Neighbours and local communities perceptions before the installation 7 Neighbours 6 Local community Frequency expressed Very negative Negative Indifferent Positive Very positive Their opinion Frequency expressed Figure 22 Neighbours and local communities perceptions after the installation Neighbours Local community 0 Very negative Negative Indifferent Positive Very positive Their opinion 33

44 4.35 Economics & lack of knowledge of turbine operators Grants & loans Two people were unable to answer this question. 4 organisations (24%) did not have any financial help at all (a school, a business, and two environmental centres). Only one took out a loan (a business). Of the 13 which had received grants, 8 (62%) mentioned Clear Skies / SCHRI, 4 mentioned an electricity supplier s grant stream (31%), 2 their local support team for Community Renewables Initiative (15%). Other funding sources included: European Commission; Department of Enterprise, Trade, and Investment (DETI); and Buckinghamshire County Council. 2 people who had received grants neglected to say from where. 5 (38%) received grants from more than one source. Out of the 13 organisations which had received financial support, 8 (62%) said they would not have been able to proceed without it, and 5 (38%) were not sure. Not a single one said they would have proceeded anyway. ROCs Two people were unable to answer this question. Only 5 organisations are collecting ROCs (29%), 2 of which found the paperwork difficult, one had the paperwork completed by their local renewable energy agency, one did not know, and one disagreed that the paperwork was difficult. 2 people are in the process of completing the ROC paperwork, one of which is finding it difficult. 10 are not collecting ROCs, none of which said anything about the paperwork. Generation estimates One other interesting fact is the lack of knowledge many people have regarding their small turbines. Of the 14 that were in a position to know how many kwh their turbine produced, 5 did not know, and at least 2 seemed far too low and 1 far too high. This is >50% of respondents that did not know how much energy their turbine generates. 34

45 Therefore many people did not know if this was the same, more or less than they had originally anticipated. Of the 14 that should have known, 3 did not answer, 2 wrote that they did not know, 6 wrote the same (1 of which had overestimated kwh generated), and 3 wrote less. An interesting result is that not a single person wrote that it was generating more than expected. Payback With regards to payback, of the 17 people that should have known 4 did not. Given the answers provided for energy generated the answers given have been checked using the data from the returned questionnaires, and/or NOABL and power curves. The responses are shown in figure 23 below. 5 Figure 23 Owner s estimates of the turbine s paybacks 4 Frequency >20 Payback period It was possible to check 10 of these, and the results are, probably over optimistic: 5, 10, 12, 13, 15, 20 years, probably correct: 9, 14, and two of the >20 years. (There is insufficient data to determine what the payback figures actually are.) 35

46 It is significant that the 9 year payback is the 80kW Lagerwey, and the 14 year payback is the 4 x 20 Jacobs turbines these are the largest installations in terms of total rated power out of all the ones that returned questionnaires. Both of these received grants, and the Lagerwey is also claiming ROCs Reasons for installation 14 Figure 24 Reasons listed for installing the turbine No. of organisations listing the reason Salesman "County initiative" Network effect Financial reasons To test the turbine General education Organisation's image Reasons for installation Environmental reasons Environmental education Two organisations were unable to provide answers. Network effect means that they knew somebody who had one. County initiative presumably means the decision was mandated from the county council (this person did not list any other reasons). Given that the majority of the institutions are educational in some way (including the environment centres), it is not surprising that 13 of them (76%) list environmental education. Given that they are all environmentally conscious, neither is it surprising that 12 (71%) list environmental reasons. (Only one organisation did not list either 36

47 environmental education or environmental reasons, and that was the one that listed county initiative.) Relevant to the economics in Chapter 5, only 2 (12%) listed financial reasons. The fact that nobody selected salesman, might tell us that up to now wind turbines have been marketing themselves, without the need for initiative from manufacturers Obstacles to installation Frequency Figure 25 Owner s rating of the difficulty in overcoming obstacles Almost insurmountable Difficult Small problem No Problem Actually helped 0 Planning issues Connecting to the grid Neighbours Rest of local community Potential obstacle 8 7 people (44%) had some problem with planning, 7 (50%) had a problem in connecting to the grid, 5 (29%) had a problem with neighbours, and 2 (12%) had a problem with the rest of the local community. Only planning and the local community managed to help installations. 8 With graph LMU above, it is important to note that 3 people did not answer planning, 5 did not answer regarding grid-connection (2 because their turbines are off-grid), 2 did not answer neighbours or local community. 37

48 4.38 Turbine problems & after sales service 8 of the 19 installations (42%) suffered a technical problem. It should be noted that all of the problems were different. They were: blade broke off tail fell off problems with a power supply unit gearbox problems generator problems inverter problems mast was badly finished and turbine kept sticking in one position lightning strike put it out of commission for 2 weeks There is insufficient data to draw conclusions on the quality of any of the individual products. In total 5 people (26%) complained about the after sales service they had received. 4 of these had had problems that d needed fixing, so 50% of those who had had problems complained about delays in getting them fixed. This is despite the fact that no question on after sales service was asked With hindsight, would they install a small wind turbine again? Of the 16 people who were able to answer this question, 100% said that they would make the same decision again although 2 (13%) said they would choose a different turbine (without the questionnaire prompting them). Both of these customers had had technical problems with the turbine and had experienced poor after sales service. 38

49 4.4 Analysis of results 4.41 Of all the installations found BRE estimates there are 700 odd mini (>0.5kW & <50kW) wind turbines in the UK (DTI, 2005). Table 8 shows 62 in urban areas. Therefore at a minimum ~10% of the mini-wind installations in the UK are in the urban or semi-urban environment, in August For total wind installations (including planned) there should be at least 100. Figure 15 shows that the majority of installations are limited to schools & environment centres (but bear in mind the limitations of the study above). Figure 15 does not accurately represent the contribution made by local authorities, as both schools & environment centres are often local authority controlled. In addition, the planning departments of local authorities must be considered. Therefore, local authorities play an important role in all small wind turbine installations. From figure 16, the popularity of Provens is obvious (33% of all turbines chosen which makes the unpopularity of their 0.6kW model all the more surprising), as is the high number of Unknown turbines (17%), and the percentage of turbines which are British (74%) 9. The lack of micro turbines either supports, or is because of, the viewpoints of Marlec, LVM, and Ampair. The most popular turbines are the Provens 2.5 and 6kW. There are a surprising number & proportion of rooftop installations because they have only been occurring for approximately the past 2 years. They are probably expanding rapidly e.g. 9 of the 25 rooftop installations are Swifts (36%) and 4 are Windsaves (16%), which have only been available in This can be compared favourably against the proportion of large wind turbines installed which are British. 39

50 4.42 Of the returned questionnaires Demographics So far, most installations have been made by people who are environmentally conscious. Nobody is installing them solely because of financial reasons. Turbine locations The urban sites with open spaces are being developed first. This is unsurprising, as this kind of installation is well-established, and there are relatively good wind regimes. People s perceptions of the turbine Few people find these small wind turbines visually stunning. Although it is possible that some people will prefer the design of the newer models, e.g. Swift, XCO2, Wind Dam, etc, and this could potentially help the small wind industry. Nevertheless, the results show that visual appearance need not be an obstacle to installation of small wind turbines. The vast majority of people are happy with their wind turbines. It is fortunate that the turbines are believed to be safe, but it is hard to say on what basis the people rated their turbines as safe. At present there is limited health and safety guidance for small wind turbines. There are a wide variety of opinions on the amount of noise these turbines make, and no apparent correlations with turbine type or location. There could be several reasons for this relative background noise, distance the owner is accustomed to being from their turbine, or differences in the owner s hearing. The change in perception for neighbours & community between before and after an installation is remarkable, and very good news for the industry. Such evidence could truly help the small wind industry, showing that their products are popular. Therefore, negative feedback from a community or neighbours before an installation may well be due to an overreaction or lack of knowledge. Taking them to see a working small wind turbine could be an excellent way to assuage their fears. Economics & lack of knowledge of turbine operators To date, the existence of grants has been very important for the installation of small wind turbines. It is likely that without grants the number of installations would 40

51 significantly drop. This is to be borne in mind given that Clear Skies will end in March 2006, and that there is no guarantee of a smooth transition period to the Low Carbon Buildings Program or of its form. With regards to generation estimates, it is interesting that not a single person wrote that the turbine was generating more than expected this would have been the case with large wind turbines, where manufacturers often underestimate their performance so as to please customers (Gipe, 2004). Small wind turbine manufacturers may be overestimating performance or relying on incorrect wind speed data for those locations (e.g. NOABL data is widely used by the industry, but see comments on it in Chapter 5). Over optimism on payback times shows lack of knowledge once again, but it also shows that the economics are worse than people anticipate/calculate. Whether or not this will lead to disappointment remains to be seen. It is hard to tell if making the paperwork for claiming ROCs easier could significantly impact on the number of installations made. Obstacles to installation Connecting to the grid and planning are the biggest potential obstacles to installing small wind turbines. Neighbours and local community tend not to be much of a problem. (There is not enough data to see if initiatives like PPS22 have had an impact yet.) Hindsight Despite the complexity of installing a small wind turbine, or the expense, or the technical / after sales problems many of these people have had, they would make the same decision again with hindsight. Exactly why is unclear from this data. Overall Overall the results are positive for the small wind turbine industry, but it has serious issues to contend with: their products need to appeal to people who are not just environmentally conscious, or interested in environmental education 41

52 the industry needs to be able to survive any potential hiatus in Government grant programs connecting to the grid and planning need to be easier the finished products need to be less problem-prone after sales service needs to be improved 42

53 5. ECONOMICS This section of the report covers the economics of small urban wind turbines for a school in Scotland, a typical domestic situation in the south east of England, and some large buildings in London. It gives an assessment of the economic viability of small urban wind. All of the economic assessments in this chapter should be used as a guide only. 5.1 Methodology A spreadsheet was created to model the economic data. It uses standard discount analysis to calculate the net present value and payback. It also estimates the energy the turbine could produce using the power curve and a Rayleigh distribution. Power curves are assumed to be accurate. 10 Appendix I shows the variables included in the model. Sensitivity analysis is also used to determine the sensitivity of the economic situations to the variables. To do this it is necessary to pick a base case where the values of all the variables are taken to be equal to 1, and then the effect that different fractions (say 0 to 5) of each variables has on the Levelised Production Cost (LPC) of energy is shown. The result is a spider diagram, with the lines converging on the base case. The LPC is the present cost of the energy from the turbine given the costs it has and income it provides over its lifecycle (assumed as a 20 year period). LPC does not need to make any assumptions about the electricity tariffs, including the future evolution of electricity prices but in assessing economics one can consider those factors once the LPC is calculated. 10 Recall that power curves are from manufacturers and not from independent testing. 43

54 Although 7 of the people who returned questionnaires on their installation agreed to answer more questions on the economics, only 1 person did. This means that limited data is available on the real breakdown of costs of actual installations. 11 No modelling can be done on the Windsave, as neither the power curve nor generation estimates at different AMWSs are available in August Estimated installed costs per kw e for turbines Based on the information sources, estimates for installation costs of turbines are shown in Appendix J. Figure 26 below is the graphical representation of this data. Clear Skies say that a typical system cost is /kw (Clear Skies, 2005). As can be seen, many estimates of turbine costs fall within this band. In figure 26 below the Clear Skies estimate is next to the y-axis. Estimated cost per installed kw, /kw Figure 26 Estimated turbine installed costs in /kw Clear Skies estimate D400 Surface Power Windsave Swift (now) Swift (projected) Proven 2.5kW (ground) Proven 2.5kW (building) Turbine type Iskra Proven 6kW (ground) Proven 6kW (building) Proven 15kW Gazelle In figure 26 above the error bars show the full range of installed costs that the research has found for each kind of installation, and the heights of the columns 11 However, many other sources of data were utilised, as outlined in Chapter 2. 44

55 represent the average of the extremes of those ranges. There was insufficient data to try and gauge the probability that an installation might have a given cost. There is more data for some installations such as the Proven 2.5kW (ground-mounted), than others, meaning the extremes for installed price are broader. This is because the installed cost of a turbine depends a great deal on individual site factors. Some of the other installation costs might show the same range of extremes if more data were available. Building-mounting Proven 2.5 and 6kW turbines is not significantly more expensive than ground-mounting them. The Windsave is the cheapest turbine per installed kw, but this is the manufacturer s estimate and it is not yet being sold at this price. Very few installations exist, so the price cannot be confirmed and may be subject to change. Surface Power s turbine is a do-it-yourself kit which may explain the low cost, but as with the Windsave there is very limited data available apart from that supplied by the manufacturer. Plotting a graph of /kw against rotor diameter shows no significant correlation, due to a lack of data (particularly with turbines of a higher rotor diameter). 45

56 5.3 St. John Bosco School, Renfrewshire Figure 27 John Bosco School s turbine and its location St John Bosco School This analysis is based on an actual installation of a Proven 2.5kW at St. John Bosco School. The school can be seen on the map in figure 27. It is in Erskine, the westernmost part of Glasgow. AMWS The school estimates their annual energy production at 8,600kWh per year (Appendix G). This corresponds to an AMWS of 7.15 m/s. At 45m above ground level, NOABL estimates an AMWS of 6.50m/s, at 25m 5.8m/s, and at 10m 5m/s. The turbine s mast is 11m high but it is also on a hill, and the location is near the sea which might make it windier than NOABL predicts. However, considering how local topography affects NOABL, 8,600kWh should be regarded as an optimistic estimate. (BWEA, 2005) Tariff The school have a net metering arrangement with Scottish Power, so they buy and sell electricity at 6.15p/kWh. Net metering is the equivalent of offsetting 100% of imported electricity costs. 46

57 Economics They do not claim ROCs (Appendix G). Total project costs were 25,000, but grants worth 18,000 were obtained from two sources. (EST, 2005a) The remaining 7,000 was shared with the Local Authority. The school estimated the payback time of their Proven 2.5kW to be 13 years. Assuming the school paid 5,000, and a 4% discount rate, and 0% annual change in electricity prices, gives the same payback as the school estimated. Figure 28 below analyses the sensitivity of the economic situation the school believes they are in to changes in various parameters. Table 11 base case of the school for LPC sensitivity analysis Energy generated 8,600kWh School s investment 5,000 Discount rate 4% Annual maintenance costs ROCs claimed? 180 No 47

58 Levelised Energy Cost /kwh Figure 28 LPC sensitivity analysis for John Bosco School Energy generated School's investment Discount rate Maintenance costs ROC value Fraction of case study's situation In figure 28 above, the school s LPC is most sensitive to changes in energy produced. If the turbine generates less than they believe (which is likely), they will effectively be paying more for their energy. The LPC is also quite sensitive to the investment that the school made (5 on the x-axis is equivalent to the school paying the full cost of the turbine 5 x 5,000 = 25,000). The LPC is less sensitive to the effects of discount rates and annual maintenance. As the school is not claiming ROCs these have been calculated in a different way. Where the fraction is 1 then ROCs = 0, then it is increased proportionally until at 4 ROCs = 45. If the school started claiming ROCs today, then it would be the equivalent of the LPC being at 4 on the ROC graph. But if the value of ROCs were to then fluctuate the effect this would have on the LPC is also shown. Changes in turbine model also affect the economics significantly. Below, in table 12 and in figure 29 the LPCs for different turbine types at this location are shown. Given the grant situation with the school is complex and would have changed had they opted for a different turbine, represent the full costs of the turbines are represented here. 48

59 Table 12 estimated installed costs & LPCs for turbines at John Bosco School Proven 2.5kW Iskra 5kW Proven 6kW Proven 15kW Initial cost, yield, kwh LPC, /kwh The reasoning behind the estimates for the different turbine costs for this situation can be found in Appendix J. Figure 29 Estimated LPCs for different turbines installed at John Bosco School LPC, p/kwh Proven 2.5kW Iskra 5kW Proven 6kW Proven 15kW Turbine type Assumptions made in calculating the LPCs: Project lifetime of 20 years No grants No maintenance costs No ROCs claimed Discount rate of 4% AMWS of 7.15m/s The overall economics would have been significantly better if the school had opted for a larger turbine. The improvement in LPC from a Proven 2.5kW to the other turbines exceeds the bounds of error, and so may the improvement from a Proven 6kW and a Proven 15kW. However, from the results obtained, no difference can be assumed in the economics of an Iskra 5kW and a Proven 6kW. 49

60 5.4 A traditional house in central Reading, Berkshire This analysis is to assess the feasibility for domestic small wind turbines in a typical inland urban site in the South East of England the large town of Reading, in Berkshire. Reading has been chosen because wind speed data is available for it. 12 The turbines (for which data is available) that might be appropriate for an inner-city house are: Eclectic s D400 Surface Power s the Swift The highest point of a typical house in central Reading is ~12m high. Therefore, the rooftop turbines could have a hub height of ~13-14 metres above ground. As Surface Power turbines cannot be roof-mounted (Appendix A), it is assumed that they could be installed on a 13 or 14m mast (or higher) provided potential owners have a large enough garden. However, this is much less convenient than a roofmounted installation. 12 It has also been chosen because it is based on a real situation. Dr. Jonathan Gregory who works in climate change science is interested in installing a small wind turbine on his house at this location. 50

61 Location Below is a map of central Reading. The residential areas principally consist of closely built houses, where buildings rarely exceed 12m in height. Figure 30 Map of central Reading AMWS The Meteorology Department of Reading University (based in the Whiteknights campus visible on the map) have collected extensive data from an 8m mast and estimate an AMWS of 2.8m/s (Ken Spiers , 18/8/05). However: 8m is lower than a turbine would probably be placed the mast is (effectively) in a field in the middle of Reading most houses are surrounded by houses of the same height On balance, 2.8m/s is a relatively good guess for a turbine in this area, given that the first of these factors should mean that the turbine receives more wind while the next two should mean it receives less wind, and given that there is no other data available apart from NOABL. 51

62 NOABL estimates that the wind speed 10m above ground would be 4.8m/s here indicating its unreliability where local topography is complex. Tariffs A green electricity tariff might be 7.56p/kWh. 13 Electricity consumption Typical annual electricity consumption might be 2,900 kwh/year. 14 Economics Table 13 Estimated economics of residential turbine installations in Reading Turbine type Annual Installed Payback Possible Payback energy yield, cost kwh w/out grant, years grant with grant, years D , Not eligible XXXXX Surface Power Technologies 178 1, Not eligible XXXXX Swift 474 5, , Assuming conditions synonymous with best case scenario conditions: none of the electricity is exported annual maintenance costs are zero discount rate of 0% 4% annual increase in energy costs Best case installation costs for each turbine None of the turbines are exporting enough energy to qualify for ROCs. 13 Based on Jonathan Gregory s bills. 14 Based on Jonathan Gregory s electricity consumption. 52

63 The Swift is the only one that could qualify for a grant as the D400 and Surface Power s turbines produce too little power. (Clear Skies, 2005) Even with a grant, the Swift payback is 41 years. This is considerably greater than the expected lifetime of the turbine. Therefore, it would be uneconomic for the homeowner of a typical house in Reading to install any of these turbines. To raise public awareness one could install a D400 relatively cheaply, but it would only reduce their annual energy bill by 8.32 (at these tariffs). For the D400 to payback within 10 years at this location under the highly favourable conditions above, it would need to cost 99 or less. While at 2,200 the D400 takes 13 years to payback, even with an AMWS of 10m/s and including ROCs at 45/MWh. Surface Power s turbine generates its maximum amount of energy at an AMWS of about 9.5m/s, and in the best case conditions above, it can payback in 11 years. It can not benefit from ROCs as it is intended to be an independent off-grid supply. 15 With the best case cost price for the Swift of 3,500 after grant, and including ROCs at 45/MWh, it can payback within 10 years with an AMWS of 5.5m/s. But with the current cost of the Swift of 8,500 after grant, including ROCs, to payback within 10 years requires an AMWS of 9m/s. Figure 31 below is LPC sensitivity analysis, for a Swift, where the base case of 1 is: Table 14 Base case for residential Swift installation in Reading, for LPC sensitivity analysis Energy generated 474kWh Amount invested 3,500 Discount rate 4% Annual maintenance costs As explained in Appendix A, Surface Power market their turbine (and solar panels) with a deepcycle battery, inverter, and plug sockets, and intend for this arrangement to be off-grid so that a homeowner may operate some of their appliances from it whilst leaving the rest of their appliances connected to the grid, thus reducing their bills. 53

64 Levelised Energy Cost /kwh Figure 31 LPC sensitivity analysis for the installation of a Swift on a house in Reading 8 Energy generated 7 Amount invested Discount rate 6 Maintenance costs Fraction of base case parameters The LPC is most sensitive to changes in the energy generated, and the installation cost. Even a small improvement in either can significantly improve the economics. The line for amount invested could stop where the fraction is 3.43, because that reflects 12,000. The furthest extent for the line of energy generated, reflects an AMWS of 5.2m/s. The annual maintenance cost of 75 has been guessed, but once the maintenance costs for the Swift are known (whether they are 0 or 375) the LPC can be deduced from this graph. In the base case the Swift generates insufficient energy to qualify for ROCs, hence there is no graph for it. 54

65 5.5 Large buildings in London RIBA and the Aylesbury Estate This analysis looks at theoretical costs of two projects in London. The RIBA (Royal Institute of British Architects) who were interested in installing a wind turbine on their roof, 16 and the Aylesbury Estate in Southwark should have some wind turbines installed on the rooftops of their tall tower blocks. They have also been chosen because wind speed data is available for them. Locations Figure 32 Map of RIBA s location in London In the map above, the RIBA building is just off the A4201, W1B 1AD. It is slightly taller than the buildings in the surrounding area. 16 They were refused planning permission for such a project prior to PPS22 and the GLA s support, but may try again. 55

66 Figure 33 Map of Aylesbury Estate s location in London The Aylesbury Estate comprises much of the area south of East Street, e.g. around Thurlow Street, SE17 2UZ. It is Europe s largest estate. AMWS Data measured from the rooftops of the RIBA building and a tower block of Portland Estate (near Aylesbury Estate) found the AMWSs to be 3.4m/s (Thomas, 2003) and 8m/s respectively. 17 (Nick Banks , 4/8/05) The difference in wind speeds could be due to differences in the relative height of the RIBA building and its surroundings, and the Portland Estate tower and its surroundings. The Portland Estate tower could also be much higher. At RIBA NOABL estimates the AMWS to be 5.7m/s at 25m height (the RIBA anemometer was 36.5m high Thomas 2003), and at Aylesbury Estate at 45m height it finds it to be 6.1m/s although the towers could be higher than this. 17 Southwark Council who conducted the measurements take no responsibility for any conclusions that might be drawn from the use of this data. 56