Micro wind turbines in the UK domestic sector

The micro-scale wind turbine industry is expanding in the UK with institutional support and UK legislation encouraging the development of numerous companies with a profusion of design options. The application of micro wind turbines in urban environment is encouraged in the UK via a grant scheme which provides a proportion of the initial capital costs. This development is predicated on the assumption that micro wind turbines have the potential to reduce built environment CO₂ emissions. Current methods of estimating the wind speed are reported to over predict by approximately 2.0 m/s. The energy yields of a range of typical micro wind turbines (in the 0.4–2.5 kW size range) were estimated here using two wind speed datasets sited within 1 km of each other recorded with a temporal precision of 10 min. The annual energy yield of a 1.5 kW turbine was found to be 277 kWh and 2541 kWh for the two sites analysed indicating the problem with the current method of yield estimation. Between 33 and 55% of the electricity generated would be exported dependant on the dwelling's electrical demand. For the high yield site, the simple economic payback of this turbine was found to be 26.8 years i.e. beyond the likely life time of the turbine with CO₂ savings of 1093 kg CO₂. The research suggests that this technology does represent a possible route for reducing CO₂ emissions but this is unlikely to be realised unless an adequate method is found for more accurately predicting energy yield at a specific site.     

A comparison of the UK Standard Assessment Procedure and detailed simulation of solar energy systems for dwellings

The drive to reduce worldwide carbon emissions that are directly associated with dwellings and to achieve a zero carbon home dictates that renewable energy technologies will have an increasingly large role in the built environment. The Standard Assessment Procedure (SAP), formulated by the Building Research Establishment (BRE), is the UK Government's approved methodology for assessing the energy ratings of dwellings. This article presents an evaluation of the advantage given to SAP ratings by the domestic installation of typical photovoltaic (PV) and solar domestic hot-water (SDHW) systems in the UK. Comparable PV and SDHW systems will also be simulated with more detailed modelling packages. Results suggest that calculation variances can exist between the SAP methodology and detailed simulation methods, especially for higher performance systems that deviate from the default efficiency parameters.     

Computational Analysis of Fire Dynamics Inside a Wind Turbine

Wind turbines are generally considered cost-effective, reliable and sustainable energy sources. Fires are not common in wind turbines, but a significant number of fires occur every year due to the large number of turbines installed. Wind turbine fires are difficult to extinguish hence significant damage is expected. Due to the unmanned operation, the probability of a turbine being occupied during a fire is very low. However, operators can do several tasks every week, and hence be exposed to a certain risk. Moreover, there is a general lack of information about how a fire develops inside a wind turbine and the subsequent evolution of the tenability conditions during the time required for an eventual evacuation. Gamesa has been working on fire safety since 2013, using CFD fire modelling to provide insights on wind turbine fire development for the design of emergency procedures. The paper describes a fire hazard analysis performed in a Gamesa’s 2.5 MW turbine. A CFD simulation is carried out to estimate the effects during the first minutes of a typical wind turbine fire in an electrical cabinet. Results show that average oxygen concentration at the nacelle remains above 19.5% during the first 10 min; temperature remains below 60°C for 12 min if measured at 1.5 m; and visibility is on average assured at heights lower than 1.5 m, with values above 5 m during the first 8 min in worse locations, implying no danger for personnel. The potential of this type of analysis to design safer wind turbines under performance-based approaches is clearly demonstrated.     

Domestic electricity use: A high-resolution energy demand model

The pattern of electricity use in an individual domestic dwelling is highly dependent upon the activities of the occupants and their associated use of electrical appliances. This paper presents a high-resolution model of domestic electricity use that is based upon a combination of patterns of active occupancy (i.e. when people are at home and awake), and daily activity profiles that characterise how people spend their time performing certain activities. One-min resolution synthetic electricity demand data is created through the simulation of appliance use; the model covers all major appliances commonly found in the domestic environment. In order to validate the model, electricity demand was recorded over the period of a year within 22 dwellings in the East Midlands, UK. A thorough quantitative comparison is made between the synthetic and measured data sets, showing them to have similar statistical characteristics. A freely downloadable example of the model is made available and may be configured to the particular requirements of users or incorporated into other models.     

城市中风力发电与建筑一体化设计

随着全球城市化程度的日益提高,城市所需能源急剧加大,当下对城市中风能利用的研究和应用具有重要的现实意义。通过介绍城市中风力发电与建筑一体化的设计方法,分析风力发电与建筑一体化设计的特点和存在的问题,提出三种一体化设计的方式：风机安装在屋顶上、风机安装在两座建筑物之间和风机安装在建筑物的空洞中。     

Establishing the zero-carbon performance of compact urban dwellings

This paper presents an analysis of the zero-carbon performance of a case-study building which is representative of a growing number of new buildings that are being built on redevelopment sites in inner-city areas in the UK. Compact urban dwellings are apartment style buildings with a floor area of ～50 m² per dwelling, often based over two floors. The constraints of this type of building on achieving zero-carbon performance in the context of the Code for Sustainable Homes is discussed and the shortcomings of the code are demonstrated in terms of the target heat and electricity demand targets for the design of the building systems. A graphical representation of the simulation results is used to present the findings. It has been demonstrated that in specific urban contexts, zero-carbon performance as defined within the current UK compliance framework may be very difficult to achieve in practice given the assumptions used in the simulation here. Therefore, it is very likely that zero-carbon compact urban dwellings may require a net off-site import of electrical and/or thermal energy.     

Theoretical study and experimental verification of vibration control of offshore wind turbines by a ball vibration absorber

In this paper, a ball vibration absorber (BVA) is introduced for vibration control of offshore wind turbines. The dynamic responses of offshore wind turbines equipped with a BVA are presented. Both theoretical and experimental investigations are carried out. An analytical model for the wind turbine tower system with installed BVA is developed based on Lagrange's equation. The BVA-structure integrated equations are derived and solved in both time domain and frequency domain. A series of shaking table tests on a 1/13-scale wind turbine model with and without a BVA were carried out to evaluate the effects of BVA on the vibration mitigation of the wind turbine tower system under earthquakes and equivalent wind-wave loads. Numerical simulations of the system are performed and compared with the experimental results. Good agreement between the numerical and experimental results is observed. The results indicate that BVA could effectively improve the performance of the offshore wind turbine.     

Likelihood of wind energy assisted hydrogen production in three selected stations of Fiji Islands

ABSTRACT

Majority of the people have been paid attention towards renewable and clean sources of energy like wind. Due to the uncertainties related to wind turbines, issues of energy storage are noteworthy. One of the aptest methods of energy storage is the production of hydrogen from the wind. The main aim of this paper is to investigate the potential of wind energy assisted hydrogen production in three selected stations of Fiji Islands using various wind turbines. From the analysis of results and discussion, Vestas V110-2.0 provides acceptable capacity factors among all inspected wind turbines with the highest value of 77.06% for the station at Labasa. Additionally, the highest energy production was from the Vestas V110-2.0 wind turbine with an annual production of 13,501,620?kWh. The conversion system used in this study resulted in a linear relationship between generated wind energy and the amount of hydrogen produced. Therefore, the highest amount of yearly hydrogen production (240.19 ton-H) is related to the largest examined wind turbine, installed in the station at Labasa.     

Evaluation of energy performance indicators and financial aspects of energy saving techniques in residential real estate

The energy consumption in the existing residential building stock accounts for about 40% of the total energy consumption in the built environment. Different types of energy performance indicators to assess the energy consumption of buildings were and still are internationally under development. In this paper we compare the methodologies and accuracies of three Dutch energy performance indicators by applying them to eight houses. This application shows that the actual domestic energy use is linearly correlated with the estimated energy consumption given by the energy performance indicators, but 7-25% lower.Based on the energy performance indicators and actual energy use, we offer a methodology to incorporate additional revenues within the financial analysis of energy saving techniques. These revenues are related to the value of the dwelling in which the techniques are installed. We use the same houses to analyse the financial returns on energy saving investments. By assigning the value increase of real estate to two popular specific energy saving techniques, namely wall and roof insulation, it is found that the payback period could be 40-50% shorter than when it is solely based on investment costs and energy prices.     

Wind turbine power curve estimation based on cluster center fuzzy logic modeling

Wind energy applications and turbine installation at different scales have been increased for last decade. Technically wind turbine capacity has been improved at high levels. However, electricity could not be generated at all stages of wind speed and so there are some limits related to cut-in and cut-out data. One of the main problems in wind engineering is to estimate output data of wind turbines depends on wind speed and system values. Wind speed problematic values, that are less than cut-in and greater than cut-out, take the most important role for estimating wind power curve models. All wind turbines have different cut-in and cut-out limits and generating of electricity could be achieved in a certain interval that could be called as affective interval. Fuzzy logic that is a new and novel verbal logical approach has many applications in the field of engineering. Cluster center fuzzy logic modeling is also a new and the effective method in this scientific area. In this paper, the first power curve of a wind turbine is modeled by least square methodology. After that depending on the fuzzy logic approach a new application is realized. It is seen that, this curve type could be well represented and modeled by the clustering center fuzzy logic modeling than classical least square methodology. It is estimated that four or five cluster centers are enough for representing wind turbine power curve by running proposed method.     

Overheating in English dwellings: comparing modelled and monitored large-scale datasets

ABSTRACT

Monitoring and modelling studies of the indoor environment indicate that there are often discrepancies between simulation results and measurements. The availability of large monitoring datasets of domestic buildings allows for more rigorous validation of the performance of building simulation models derived from limited building information, backed by statistical significance tests and goodness-of-fit metrics. These datasets also offer the opportunity to test modelling assumptions. This paper investigates the performance of domestic housing models using EnergyPlus software to predict maximum daily indoor temperatures over the summer of 2011. Monitored maximum daily indoor temperatures from the English Housing Survey’s (EHS) Energy Follow-Up Survey (EFUS) for 823 nationally representative dwellings are compared against predictions made by EnergyPlus simulations. Due to lack of information on the characteristics of individual dwellings, the models struggle to predict maximum temperatures in individual dwellings and performance was worse on days when the outdoor maximum temperatures were high. This research indicates that unknown factors such as building characteristics, occupant behaviour and local environment makes the validation of models for individual dwellings a challenging task. The models did, however, provide an improved estimate of temperature exposure when aggregated over dwellings within a particular region.     

House tests of an energy saver

A control unit which prevents wasteful boiler cycling in domestic radiator-type heating and hot water systems was tested in six different houses over a 12-18 months period. Annual fuel savings averaging 9-11 percent were indicated, with payback times of 6-12 years if a unit were professionally installed. Fuel savings were greater where the systems were used for long hours without secondary heating; and payback periods would become shorter for larger systems. The author is with the Department of Building Engineering at Liverpool University, UK.     

House tests of an energy saver

A control unit which prevents wasteful boiler cycling in domestic radiator‐type heating and hot water systems was tested in six different houses over a 12–18 months period. Annual fuel savings averaging 9–11 percent were indicated, with payback times of 6–12 years if a unit were professionally installed. Fuel savings were greater where the systems were used for long hours without secondary heating; and payback periods would become shorter for larger systems. The author is with the Department of Building Engineering at Liverpool University, UK.     

Predicting and quantifying the effect of variations in long-term water demand on micro-hydropower energy recovery in water supply networks

To improve water supply energy efficiency micro-hydropower turbines can be installed within networks at locations of excess pressure. However, future changes in flow rates and pressures at these locations could render an installed turbine unsuitable. It is therefore important that long term changes in flow conditions at potential turbine locations be considered at initial feasibility/design stages.

Using historical data over a ten-year period, this paper predicts the effects of changes in water flow rates at potential turbine locations in Ireland and the UK. Results show that future flow rates at these locations could be predicted with an R² of up to 66% using multivariate linear regression and up to 93% using artificial neural networks. Flow rates were shown to vary with population, economic activity and climate factors. Changes in flow rate were shown to have a significant impact on power output within the design life of a typical hydropower turbine.     

Methodologies for city-scale assessment of renewable energy generation potential to inform strategic energy infrastructure investment

In support of national and international policies to address climate change, local government actors across Europe and Asia are committed to reducing greenhouse gas emissions. Many recognise the contribution that decentralised renewable electricity production can bring towards reducing emissions whilst also generating revenue. However, these actors are often subject to significant financial pressures, meaning a reliable and compelling business case is needed to justify upfront investment. This article develops a method for rapid comparison of initial project viability for multiple city sites and installation options using data from wind and solar resource prediction techniques. In doing so, detailed resource assessments grounded in academic research are made accessible and useful for city practitioners.Long term average wind speeds are predicted using a logarithmic vertical wind profile. This employs detailed three-dimensional building data to estimate aerodynamic parameters for the complex urban surface. Solar resource is modelled using a Geographical Information System-based methodology. This establishes the location and geometry of roof structures to estimate insolation, whilst accounting for shading effects from other buildings and terrain features. Project viability for potential installations is assessed in terms of the net present value over the lifespan of the technology and associated Feed-in Tariff incentive. Discounted return on investment is also calculated for all sites. The methodology is demonstrated for a case study of 6794 sites owned by Leeds City Council, UK. Results suggest significant potential for small-scale wind and solar power generation across council assets. A number of sites present a persuasive business case for investment, and in all cases, using the generated electricity on site improves financial viability. This indicates that initial installations should be sited at assets with high electricity demands. Overall, the work establishes a methodology that enables large city-level asset holders to make strategic investment decisions across their entire portfolio, which are based on financial assessment of wind and solar generation potential accurate to the individual asset scale. Such tools could facilitate strategic planning within cities and help to ensure that investment in renewable energy is focused at the most viable sites. In addition, the methodology can assist with asset management at the city scale by identifying sites with a higher market value as a result of their potential for renewable energy generation than otherwise might be estimated.     

Mitigation of tower and out-of-plane blade vibrations of offshore monopile wind turbines by using multiple tuned mass dampers

Offshore wind turbines are vulnerable to external vibration sources such as wind and wave excitations due to the increasing size and flexibility. It is necessary to mitigate the excessive vibrations of offshore wind turbines to ensure the safety and serviceability during their operations. Some research works have been carried out to control the excessive vibrations of the tower and the in-plane vibrations of blades. Very limited study focuses on the out-of-plane vibration mitigation of blades. In the present study, a detailed finite element (FE) model of the latest NREL 5MW wind turbine is developed by using the FE code ABAQUS. The tower and blades are explicitly modelled, and the rotating of the blades is considered. Multiple tuned mass dampers (MTMDs) are proposed to be installed in the tower and each blade to simultaneously mitigate the out-of-plane vibrations of the tower and blades when the wind turbine is subjected to the combined wind and wave loadings. The effectiveness and robustness of the proposed method are systematically investigated. Numerical results show that MTMDs can effectively mitigate the out-of-plane vibrations of the tower and blades when the wind turbine is in either the operational or parked condition.     

Optimisation of consumer benefits from microCombined Heat and Power

Despite government targets that imply 400,000 installed microCombined Heat and Power (microCHP) units by 2010, market penetration is as yet negligible in the UK. This paper reports new experimental data to underpin decisions affecting the uptake of this technology. A simple computer model of the time distribution and use of the electricity output from microCHP, based on trials with a real installation in a UK dwelling, is coupled with a stochastic model of domestic electrical load. It predicts the proportion of output that would be consumed locally, for six household scenarios comprising three different types of house and two levels of occupation and appliance use. The results show that the proportion of microCHP electrical output exported to the electricity distribution network (up to 62%) will be higher than has been estimated by previous studies, and that this is sensitive to the thermal properties of the house and the lifestyle of the occupants. The significance of these results is examined to suggest how careful marketing and the use of half-hourly metering may be used to maximise the benefits of this technology to consumers and the environment.     

Identifying trends in the use of domestic appliances from household electricity consumption measurements

Results are presented from a monitoring study of the electricity consumption of a sample of UK domestic buildings. Five-minutely average whole house power consumption was recorded for 72 dwellings at five sites over a 2-year monitoring period. The mean annual electricity consumption for the households increased significantly by 4.5% (t = 1.9; p < 0.05, one-tailed) from the first to the second year of monitoring. New techniques are developed which estimate the electricity consumption of different appliance groups, based on analysis of the five-minutely monitored data. The overall increase in electricity consumption is attributed to a 10.2% increase in the consumption of ‘standby’ appliances (such as televisions and consumer electronics) and a 4.7% increase in the consumption of ‘active’ appliance (such as lighting, kettles and electric showers). The consumption of different energy user groups (low, medium and high) is also investigated and low and high users are identified as contributing to the overall increase in consumption. The need for further investigation, such as quantitative and qualitative studies, to improve understanding in domestic electricity consumption is discussed.     

The vibration modes of a wind turbine support structure

Lightweight wind turbines offer a considerable reduction in capital and operating costs for electricity generation from the wind. Environmental impact of installation works can be reduced. Lightweight machines are likely to be structurally flexible. It is essential for the designer to study their dynamic characteristics in order to reduce:

1. The magnitude of the stresses in the structure particularly in components loaded cyclically;

2. The electrical noise and power fluctuation experienced by electricity consumers;

3. The acoustic noise emitted.

Using Rayleigh analysis, the vibration frequencies of a mathematical model of the wind turbine support tower can be estimated. Additional structural components can easily be added and components can be modelled more accurately as the process is refined.

Available experimental measurements compare favourably with corresponding predictions.     

Roof-top wind turbines for microgeneration in urban houses in New Zealand

Microgeneration using roof-top wind turbines is at present not common in New Zealand. It is, however, being trialled by the electricity network company, Vector, in a range of urban locations. Limitations of size mean roof-top wind turbines may not satisfy the total energy requirement of New Zealand houses. Ensuring structural stability and complying with stringent noise standards in New Zealand are further issues. In addition, roof-top turbines may be inefficient in terms of net energy and carbon emissions, performance indicators that are fundamental for the adoption of this technology. This paper considers the feasibility of using roof-top wind turbines in urban houses in New Zealand and, using life cycle assessment, evaluates the net energy and carbon emissions associated with their use. The results indicate that the electricity-generating potential of centralised wind farms in New Zealand using large turbines is 11.3-7 times the generating potential of roof-top turbines mounted on urban houses. In spite of this the roof-top turbines that are currently being trialled, could have the potential to reduce the energy and carbon intensity of New Zealand electricity by 81% and 26%, respectively.