Year: 2011
Type: report
Abstract: Energy sources such as coal may contribute to diversity of supply and thereby enhance security, but deploying them works against our climate change goals.Increasingly ambitious plans to deploy intermittent renewable energy pose challenges for the reliability of electricity supplies without corresponding investment in "back-up" capacity.8. This work is based on four "core" scenarios, organised on a 2x2 matrix, for the development of the UK energy system out to 2050.One dimension of the matrix refers to the level of ambition for CO 2 reduction, the other to the "resilience" of the energy system to external shocks.9.A Reference scenario which assumes no policy measures other than those contained in the 2007 Energy White Paper is the starting point.Under the Low Carbon scenario, CO 2 emissions are constrained so that they fall 36% below 1990 levels by 2025 and 80% by 2050.Our Resilient scenario embodies a number of constraints that enhance the ability of the energy system to withstand shocks, but has no CO 2 constraints.A Low Carbon Resilient scenario includes both sets of constraints. Characterising Resilience10.The advantage of focusing on resilience as the key concept is that it can be seen as an intrinsic characteristic of the energy system.It does not require us to think about the underlying causes of a particular shock, for example a prolonged interruption of gas supply.11. Drawing heavily on the ecological sciences, we used the following working definition of energy system resilience:"Resilience is the capacity of an energy system to tolerate disturbance and to continue to deliver affordable energy services to consumers.A resilient energy system can speedily recover from shocks and can provide alternative means of satisfying energy service needs in the event of changed external circumstances." 12.To ensure that boundaries were clearly defined, we also adopted the following working definition of the UK energy system:"the set of technologies, physical infrastructure, institutions, policies and practices located in and associated with the UK which enable energy services to be delivered to UK consumers".13.The UK Government has identified three elements of energy security:• physical security: avoiding involuntary physical interruptions to consumption of energy (i.e., the lights going out or gas supplies being cut off);• price security: avoiding unnecessary price spikes due to supply/demand imbalances or poor market operation (e.g., market power);• geopolitical security: avoiding undue reliance on specific nations so as to maintain maximum degrees of freedom in foreign policy.14. To address these, we identify three key elements of a resilient energy system: lower levels of imports and hence energy demand; diversity of supply; and robust physical infrastructure.A resilient energy system needs to deliver energy services reliably in the light of outcomes to which probabilities can be attached (plant outages, weather variability) but must also be resilient to larger scale "shocks" to which it is difficult to attach probabilities.Less work has been carried out on this latter aspect. Macro-indicators of resilience15.The following quantified indicators of resilience were arrived at by assessing their practical feasibility and by conducting a variety of sensitivity analyses using the MARKAL-Med model.These are applied as constraints in the Resilient and Low Carbon Resilient scenarios. Energy demand and imports.We have set a constraint that final energy demand should fall by about 3.2% per annum relative to GDP, or about 1% per annum in absolute terms, from 2010 onwards.These were benchmarked against bottom-up estimates of the potential impact of energy efficiency measures out to 2020 made by Government in the most recent carbon and energy projections available at the time the analysis was conducted.Our assumptions about constrained final energy demand correspond roughly to the assumption of high impact of energy efficiency measures up to 2020.We then assume that the same pace of improvement will continue thereafter.This constraint is therefore at the upper end of the plausible range in terms of energy demand reduction. Primary energy demand.We have constrained primary energy demand so that no single energy source (e.g.natural gas, nuclear) gains more than a 40% market share.The constraint on maximum share for primary energy supply ensured supply diversity in the economy as a whole. Electricity generation.We have constrained the electricity generation mix so that no single energy source gains more than a 40% market share.Generation mix was constrained because the electricity sector was found to play a key role in shifting the primary energy mix.19.With these constraints applied in the resilient scenarios, the energy system develops rather differently from the Low Carbon case.The Low Carbon scenario is dominated by rapid de-carbonisation on the supply side, especially in the electricity sector.The sector is virtually de-carbonised by 2030 and electricity enters new markets through electric and plug-in hybrid vehicles and heat pumps in the residential sector.In the Resilient scenario, electricity de-carbonisation takes place more slowly.In the Low Carbon Resilient scenario, the electricity system de-carbonises by 2050 but the pace of de-carbonisation is about 10-15 years behind the Low Carbon scenario.20.The main theme in the resilient scenarios is the driving down of energy demand.This happens in respect of demand for gas in the residential, services and industrial sectors.This translates directly into reduced imports.21.The key conclusion is that the low carbon agenda contributes to meeting some resilience objectives, especially those relating to diversity but it still leaves the UK much more import dependent.The Resilient scenario reduces CO 2 emissions by 52% by 2050, well short of the UK's target. Physical Infrastructure22. The MARKAL-MED model determines how much electricity generating capacity it installs by applying a capacity margin on top of exogenously specified peak demand. 1 However, as more intermittent renewable capacity (e.g.wind) is added to the system, this simple approach may not meet recognised security standards.The WASP and CGEN models were run to ensure that sufficient investment is made.23.The models use a number of key parameters combined with statistical analysis to ensure adequate investment in electricity capacity.These include: value of lost load (£5/MWh for residential electricity; £40/kWh for industrial electricity; £5/therm for industrial gas; and loss-of load expectation for electricity (maximum 4 hours per year or 0.05% of the time).Disconnection of residential gas is not permitted.24. Applying these reliability standards adds to electricity system costs.The maximum annual increase across the scenarios is £354m in 2020 (Low Carbon Resilient scenario), £575m in 2035 (Low Carbon scenario) and £457m in 2050 (Resilient scenario).25.To meet gas reliability standards, the CGEN model adds LNG terminals and gas storage capacity in addition to facilities that are currently planned.In the Reference scenario, 160 mcm/d of LNG terminals and 2,000 mcm of storage capacity are added by 2030.In the Low Carbon scenario, the same investment in LNG terminals is made, but the need for additional storage capacity is reduced to 1,000 mcm.The Resilient and Low Carbon Resilient scenarios require less capacity because gas demand is lower and the demand profile is less "peaky".In these two scenarios,140 mcm/d of LNG terminals are added by 2030 but no additional gas storage. System shocks26.We have hypothesised a set of shocks to the gas system and investigated the impacts.We do not attribute any specific cause to these shocks, but they are compatible with previous events caused by major accidents rather than politically motivated supply interruptions.There is a system response which adds to costs, but with the most severe shocks supply curtailments are inevitable.The model predicts the following sequence of responses: a) invoking interruptible gas contracts with industry; b) re-dispatching the power system to use less gas; c) use of back-up distillate oil in CCGTs; and d) involuntary interruptions to industrial customers.1 However, intermittent renewable capacity is down-rated using a "capacity credit" to ensure investment in "back-up" plant.27.The "shocks" were all assumed to take place in mid-winter (1 January in 2025) during a spell of "average cold spell" demand.We tested the consequences of losing the Bacton or Easington gas terminals or the Milford Haven LNG terminal for periods of 5, 40 or 90 days.This is broadly consistent with past "shocks" in the gas sector.28.The costs associated with the shocks were much lower in the Resilient and Low Carbon Resilient scenarios.This is because gas demand is much lower.The loss of Easington or Milford Haven does not entail any costs at all in the 5 and 40 days cases.29.The loss of the largest terminal, Bacton, which affects both imported and domestic gas supplies, has the largest impact in the other scenarios.30.The energy system can 'ride through' the loss of Easington or Milford Haven under the Resilient and Low Carbon Resilient scenarios -and the impact of losing Bacton is much diminished.This is because these two scenarios are characterised by lower levels of seasonal gas demand.The system can cope better when demand is less 'peaky'.Demand reduction demonstrably contributes to energy system resilience 31.The imputed value of unserved energy (in £bns) is an order of magnitude larger than the changed system costs.System costs generally rise as more expensive gas is sourced and coal substitutes for gas in electricity generation.This however does not take account of the response in energy spot markets that would be expected following such events, which would tend to increase costs to consumers further.32.The patterns of response are complex because the facilities play d
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1728980084