A probabilistic method for calculating the usefulness of a store with finite energy capacity for smoothing electricity generation from wind and solar power

This paper describes a novel method of modelling an energy store used to match the power output from a wind turbine and a solar PV array to a varying electrical load. The model estimates the fraction of time that an energy store spends full or empty. It can also estimate the power curtailed when the store is full and the unsatisfied demand when the store is empty. The new modelling method has been validated against time-stepping methods and shows generally good agreement over a wide range of store power ratings, store efficiencies, wind turbine capacities and solar PV capacities. Example results are presented for a system with 1MW of wind power capacity, 2MW of photovoltaic capacity, an energy store of 75% efficiency and a range of loads from 0 to 3MW average

High-temporal-resolution analysis of UK power system used to determine the optimal amount and mix of energy storage technologies

High-temporal-resolution analysis of UK power system used to determine the optimal amount and mix of energy storage technologie

Analysis of electrical power data for condition monitoring of a small wind turbine

Certain parts of a wind turbine, for example, the gearbox require significant time and heavy lifting equipment in the event of catastrophic failure necessitating replacement. Continuous condition monitoring has the potential to catch problems early, enable scheduled preventative maintenance and thereby reduce turbine downtime, reduce the number of site visits and prevent secondary damage. Accelerometers applied to mechanical components of the drive train are traditionally used for condition monitoring but require their own data acquisition system and analysis software. In contrast, the electrical current and voltage are continuously measured and could also be used for condition monitoring more cheaply. An experimental data acquisition system has been installed on a small (25kW) onshore turbine in Leicestershire, UK to compare three-phase currents and voltages on the stator windings with six accelerometer signals. Data have been recorded before and after a gearbox failure and replacement. Data were analysed using both Fourier Transform and Morlet Continuous Wavelet Transform methods. Results show that the stator voltages show the same radial and axial mode vibration frequencies as the accelerometers and could therefore be used for condition monitoring. Furthermore, the stator currents show torsional modes of vibration not picked up by the accelerometers

A comparison of functions and safety features on electric pressure cookers

There are dozens of different electric pressure cookers (EPCs) on the market for domestic and small commercial use. They range in price from about £50 to well over £100. Seven EPCs are compared here. One, the BES model is designed for use with a 12V DC electricity, whereas the others are all designed for 230V AC electricity. Section 1 describes the functions and features. Section 2 describes the safety features. This document does not make recommendations as to one type over another, but sets out a factual comparison of functions, external and internal features. However, major safety concerns have been identified in the BES 12V DC EPC and are described in section 3.</div

Benefits of an energy storage device for a wind farm

Energy storage has been a long sought after concept that could give several benefits for an intermittent energy source like wind power. The primary objective of the study presented in this paper is to determine the role that energy storage can play in alleviating network constraints and avoid the need for network investment. Two case studies have been considered in which a new wind farm would cause an existing adjacent radial line to be thermally overloaded at times of high wind, unless the generated wind power is curtailed. Important parameters affecting the viability of using energy storage for the purpose of avoiding spillage without reinforcing the network are: line length, ratio of wind farm size to line rating, wind farm energy curtailment, network reinforcement costs, energy storage systems costs, electricity wholesale price, and losses in the store and power conversion

Time-step analysis of the DECC 2050 calculator pathways

An hour-by-hour time-step analysis is presented of United Kingdom (UK) electricity grid balancing in low-carbon energy pathways from the DECC 2050 Calculator. The detailed modelling uses the Future Energy Scenario Assessment (FESA) tool, which uses real weather data and real electricity demand data from year 2001 to model future supply and demand profiles, suitably adjusted to reflect technology uptakes. The paper describes the linking of the DECC 2050 Calculator with FESA and many of the detailed considerations within the modelling. The calculation of net demand (total demand less intermittent renewables and inflexible portions of other electricity generation) reveals the magnitude and duration of peaks and troughs throughout the year and this allows quantification of required peaking plant, energy storage, demand response or a combination of these. The results indicate that the grid balancing challenge is much greater than is apparent from the DECC 2050 Calculator, with significant excess power from renewables and less flexible generators needing to be exported or curtailed, and, at other times of the year, a significant amount of additional conventional generation being required. FESA also indicates significantly lower capacity factors for despatchable generators than indicated in the DECC 2050 Calculator. The results underline the value of energy storage and flexible demand, particularly in the high-renewables pathways, but also that much of that storage and flexibility needs to be available for days or even weeks rather than hours

Short-run impact of electricity storage on CO2 emissions in power systems with high penetrations of wind power: a case-study of Ireland

This article studies the impact on CO2 emissions of electrical storage systems in power systems with high penetrations of wind generation. Using the Irish All-Island power system as a case-study, data on the observed dispatch of each large generator for the years 2008 to 2012 was used to estimate a marginal emissions factor of 0.547 kgCO2/kWh. Selected storage operation scenarios were used to estimate storage emissions factors – the carbon emissions impact associated with each unit of storage energy used. The results show that carbon emissions increase in the short-run for all storage technologies when consistently operated in ‘peak shaving and trough filling’ modes, and indicate that this should also be true for the GB and US power systems. Carbon emissions increase when storage is operated in ‘wind balancing’ mode, but reduce when storage is operated to reduce wind power curtailment, as in this case wind power operates on the margin. For power systems where wind is curtailed to maintain system stability, the results show that energy storage technologies that provide synthetic inertia achieve considerably greater carbon reductions. The results highlight a tension for policy makers and investors in storage, as scenarios based on the operation of storage for economic gains increase emissions, while those that decrease emissions are unlikely to be economically favourable. While some scenarios indicate storage increases emissions in the short-run, these should be considered alongside long-run assessments, which indicate that energy storage is essential to the secure operation of a fossil fuel-free grid

Linking a storyline with multiple models: a cross-scale study of the UK power system transition

State-of-the-art scenario exercises in the energy and environment fields argue for combining qualitative storylines with quantitative modelling. This paper proposes an approach for linking a highly detailed storyline with multiple, diverse models. This approach is illustrated through a cross-scale study of the UK power system transition until 2050. The storyline, called Central Co-ordination, is linked with insights from six power system models and two appraisal techniques. First, the storyline is ‘translated’ into harmonised assumptions on power system targets for the models. Then, a new concept called the landscape of models is introduced. This landscape helps to map the key fields of expertise of individual models, including their temporal, spatial and disciplinary foci. The storyline is then assessed based on the cross-scale modelling results. While the storyline is important for transmitting information about governance and the choices of key actors, many targets aspired in it are inconsistent with modelling results. The storyline overestimates demand reduction levels, uptake of marine renewables and irreplaceability of carbon capture and storage. It underestimates the supply–demand balancing challenge, the need for back-up capacity and the role of nuclear power and interconnectors with Europe. Thus, iteratively linking storylines and models is key

Reconciling qualitative storylines and quantitative descriptions: an iterative approach

Energy system transition research has been experimenting with the integration of qualitative and quantitative analysis due to the increased articulation it provides. Current approaches tend to be heavily biased by qualitative or quantitative methodologies, and more often are aimed toward a single academic discipline. This paper proposes an interdisciplinary methodology for the elaboration of energy system socio-technical scenarios, applied here to the low carbon transition of the UK. An iterative approach was used to produce quantitative descriptions of the UK's energy transition out to 2050, building on qualitative storylines or narratives that had been developed through the formal application of a transition pathways approach. The combination of the qualitative and quantitative analysis in this way subsequently formed the cornerstone of wider interdisciplinary research, helping to harmonise assumptions, and facilitating ‘whole systems’ thinking. The methodology pulls on niche expertise of contributors to map and investigate the governance and technological landscape of a system change. Initial inconsistencies were found between energy supply and demand and addressed, the treatment of gas generation, capacity factors, total installed generating capacity and installation rates of renewables employed. Knowledge gaps relating to the operation of combined heat and power, sources of waste heat and future fuel sources were also investigated. Adopting the methodological approach to integrate qualitative and quantitative analysis resulted in a far more comprehensive elaboration than previously, providing a stronger basis for wider research, and for deducing more robust insights for decision-making. It is asserted that this formal process helps build robust future scenarios not only for socio political storylines but also for the quantification of any qualitative storyline

Distributing power, a transition to a civic energy future: Report of the Realising Transition Pathways Research Consortium ‘Engine Room’

The overarching challenge for UK energy policy is to ensure the delivery of secure, affordable energy in a way that meets the emission reductions targets laid out in the Climate Change Act (2008). The EPSRCfunded Transition Pathways (TP) and, more recently, Realising Transition Pathways (RTP) projects have both argued that multiple logics of governance, ownership, and control of the electricity system can be followed to address the energy trilemma. This work has developed three transition pathways for the UK energy system, each driven by different governance patterns. Each pathway has a specific technological mix, institutional architecture, and societal drivers. These pathways are: Central Co-ordination: Central to this pathway is the role of the nation state in actively delivering the transition. Market Rules: After the creation of a broad policy framework, the state allows competition and private companies to deliver sustainable, affordable energy. Thousand Flowers: This pathway is characterised by a greatly expanded role for civil society in delivering distributed low-carbon generation. The following report focuses on the Thousand Flowers pathway. There is growing interest, from a range of stakeholders, in the potential of distributed low-carbon electricity generation in delivering a low-carbon energy system. Yet there are still significant gaps in understanding, particularly regarding the feasibility of scaling up distributed generation from technological, governance, regulation, policy, and financial perspectives. The aim of this report is to address these gaps within the context of the Thousand Flowers pathway. This research was carried out by the ‘Engine Room’ of the EPSRC-funded Realising Transition Pathways (RTP) consortium. The ‘Engine Room’ was established to facilitate interdisciplinary work across the consortium and consists of research fellows and doctoral researchers from different fields in the nine partner institutions. Engine Room workshops and meetings give researchers the space to present their work and develop and exchange ideas with their peers. This report is an output of a series of interdisciplinary Engine Room workshops held throughout 2013/14 which also drew on contributions from energy industry stakeholders. These workshops brought together the current research and cumulative findings of the Realising Transition Pathways consortium, to examine the consequences of a transition from a centralised energy system to one where distributed generation plays a much greater role (50% of final electricity demand), and is delivered by a civic energy sector. In this report we do not present any panaceas, attempt to preference a civil response to energy transition, or claim technological infallibility. We do, however, explore the potential of a distributed energy future and investigate the technological trajectory it could follow, along with an institutional architecture compatible with its development. We acknowledge throughout that this is a challenging but realistic system transition