Managing Intermittency of Renewable Electricity Generation
|In the current global debate about how to simultaneously ensure secure, affordable and environmentally benign energy supplies, there are many issues of contention. The relative merits and real costs of different fuels and technologies are hotly contested in the media, industry, academia and society at large. As the governments and multinational companies of developed countries compete for diminishing oil and gas resources, Agenda 21 calls for increased access to energy for the millions who go without. If the same fossil fuel dominated technologies are used to meet this need, even if they were available or affordable, it would counteract any hopes of cutting anthropogenic emissions of CO2, the main climate change forcing gas.
Electricity has an important place within the energy debate as a premium energy vector, producing zero emissions when used to provide practically any of the energy services we need at the flick of a switch. Additionally, if electricity is generated from renewable energy sources such as wind, solar and hydro, it produces no more CO2, emissions or waste than it takes to build the generators. As prices per kWh come down with increased volume and improving technologies, perhaps the most important remaining issue with renewables is how to maximise their use while simultaneously ensuring reliability of electricity supply. The question arises due to the intermittent nature of the energy source in several leading renewable generation technologies.
A significant amount of work has in fact been done over the last 30 years to analyse and quantify the impacts of intermittency of renewables in electricity systems. However the work is somewhat disparate and often focussed on a specific aspect of intermittency such as the technical issues, economic implications, resource availabilities or demand side factors at a particular national scale. My dissertation hopes to provide a synthesis of the issues and solutions relevant to intermittency by bringing much of this disparate and focussed work together, and placing it within the contexts of scale, use and timeframes within which electricity systems operate. Although the UK is frequently used as a case study due to the availability of information, the intention of this work is to develop a more general understanding and approach which can used in managing intermittency within whatever context is in question.
The scales considered are the national, regional and local scales which enable differentiation of the issues in a highly aggregated system down to a smaller disaggregated system much more sensitive to individual actions. The different contexts of use considered are industrial, urban, rural and island users in developed and developing countries which delineate the characteristics of electricity consumers in decreasing order of grid connectivity. Network connectivity is a key tool in managing intermittency, and as such the existing mechanisms to manage both unpredictability and variation in supply and demand are explored in the context of the regulation, load-following and unit commitment time horizons over which they operate.
The specific analysis carried out on these scales, uses and timeframes involves quantification of the statistical characteristics of generation, demand and renewable natural resources. The unpredictability and variation of these factors is then combined through the use of probabilistic statistics to assess risk levels and to draw conclusions about the appropriateness of tools to manage intermittency in different contexts.