A method for mapping the turbulence intensity and excess energy available to building mounted wind turbines over a UK City

Assessing the potential of proposed urban wind installations is further hindered by insufficient assessments of both urban wind resource, and the effectiveness of commercial gust control solutions within built up areas. Evaluating the potential performance of wind turbines within the urban environment requires an estimation of the total energy that would be available to them were effective control systems to be used. This paper presents a methodology for estimating the excess energy content (EEC) present in the gusty urban wind, which is usually under represented when using assessments based only on mean wind speeds. The method is developed using high temporal resolution wind measurements from eight potential turbine sites within the urban and suburban environment. By assessing the relationship between turbulence intensities and the EEC, an analytical methodology for predicting the total wind energy available at a potential turbine site is proposed. Sensitivity analysis with respect to temporal data resolution on the predicted EEC is also demonstrated. The methodology is then integrated with an analytical methodology that was initially developed to predict mean wind speeds at different heights within a UK city based on detailed mapping of its aerodynamic characteristics. Additional estimates of turbulence intensities and EEC based on the current methodology allow a more complete assessment of the wind resource available. The methodology is applied to the UK city of Leeds as a case study and the potential to map turbulence intensities and the total kinetic energy available at different heights within a typical urban city is demonstrated

Urban Wind: Characterization of Useful Gust and Energy Capture

Small-scale wind turbine operations within the urban environment are exposed to high levels of gusts and turbulence compared to flows over less rough surfaces. There is therefore a need for such systems to not only cope with, but to thrive under such fluctuating flow conditions. This paper addresses the potential importance of gust tracking technologies within the urban environment via the analysis of the additional energy present in the gusty wind resource using high resolution measurements at two urban roof-top locations. Results demonstrate significant additional energy present in the gusty wind resource at high temporal resolution. This energy is usually under-represented by the use of mean wind speeds in quantifying the power in the wind over longer averaging times. The results support the promise of capturing a portion of this extra energy through gust tracking solutions. The sensitivity of this “additional” wind energy to averaging time interval is also explored, providing useful information for the design of gust tracking or dynamic control algorithms for small-scale turbines. Relationships between turbulence intensity and excess energy available are drawn. Thus, an analytical model is proposed which may prove useful in predicting the excess energy available across wide areas from, for example, boundary layer turbulence models

Inequality can double the energy required to secure universal decent living

Ecological breakdown and economic inequality are among the largest contemporary global challenges, and the issues are thoroughly entangled – as they have been throughout the history of civilisations. Yet, the global economy continues toward ecological crises, and inequalities remain far higher than citizens believe to be fair. Here, we explore the role of inequality, alongside traditional drivers of ecological impacts, in determining global energy requirements for providing universal decent living. We consider scenarios from fair inequality – where inequalities mirror public ideals – through a fairly unequal world, to one with a super-rich global elite. The energy-costs of inequality appear far more significant than population: even fair levels increase the energy required to provide universal decent living by 40%, and a super-rich global 1% could consume as much energy as would providing decent living to 1.7 billion. We finish by arguing that total population remains important nonetheless, but for reasons beyond ecological impacts

Low Carbon Cities: Is Ambitious Action Affordable?

Research has begun to uncover the extent that greenhouse gas emissions can be attributed to cities, as well as the scope for cities to contribute to emissions reduction. But assessments of the economics of urban climate mitigation are lacking, and are currently based on selective case studies or specific sectors. Further analysis is crucial to enable action at the urban level. Here we consider the investment needs associated with 11 clusters of low carbon measures that could be deployed across the world’s urban areas in a way that is consistent with a broader 2°C target. Economic assessment of these low carbon measures finds that they could be deployed around the world with investments of c$1 trillion per year between 2015 and 2050 (equivalent to 1.3$16.6 trillion USD in the period to 2050. However, discount rates, energy prices and rates of technological learning are key to the economic feasibility of climate action, with the NPV of these measures ranging from -$1.1 trillion USD to$65.2 trillion USD under different conditions

Producer Cities and Consumer Cities: Using Production- and Consumption-Based Carbon Accounts to Guide Climate Action in China, the UK, and the US

Meeting the commitments made in the Paris Agreement on climate change will require different approaches in different countries. However, a common feature in many contexts relates to the continued and sometimes increasing significance of the carbon footprints of urban centres. These footprints consider both production or territorial (i.e. Scope 1 and 2) emissions, and consumption or extra-territorial (i.e. Scope 3) emissions. Although a growing number of cities have adopted targets for their production-based emissions, very few have even started to analyse or address their consumption-based emissions. This presents a potential challenge for urban policymaking if consumption emissions rise while production emissions fall, and for climate mitigation more broadly if emissions are effectively migrating to areas without carbon reduction targets or capabilities. To explore these issues, in this paper we analyse and compare production- and consumption-based emissions accounts for urban centres in China, the UK and the US. Results show that per-capita income and population density are strong predictors of consumption-based emissions levels, and consumption-based emissions appear to diminish but not decouple with higher per-capita incomes. In addition, results show that per-capita income is a predictor of net emissions - or the difference between production- and consumption-based accounts - suggesting that continuing increases in per capita income levels may drive the ‘leakage’ of urban emissions. These findings highlight a risk in placing too much faith in city-level climate strategies focused only on production-based emissions, and stress the importance of new city-level initiatives that focus on consumption-based emissions, especially in cities that are shifting from producer to consumer city status