Now showing 1 - 8 of 8
  • Publication
    Pumped Hydro and Compressed Air Energy Storage at High Wind Penetrations
    (Energynautics GmbH, 2013-10-24) ;
    Energy storage is a widely used tool for balancing power systems and for providing increased operational flexibility - as such it can assist with the integration of variable renewable electricity generation. Grid-scale energy storage provides potential solutions to some of the technical and economic challenges which arise in systems with high penetrations of variable renewables, particularly on isolated systems. However, capital costs per MW are high, which means that variable renewable penetrations must reach significant levels before the operating cost reductions justify the capital expenditure. Optimum levels of grid-scale storage are explored, considering capital costs and potential operational cost savings for two storage technologies - pumped hydroelectric storage and compressed air energy storage. Grid-scale installations are found to achieve significant cost savings, particularly at high levels of wind generation. While the potential for savings is eroded significantly at high levels of DC interconnection, they remain high when non-synchronous penetration limits are increased.
      199
  • Publication
    Impact of flexibility service requirements on investment decisions and costs
    New system services, required for the efficient operation of systems with high shares of variable renewable generation, will change the make up of future generation portfolios. Including these new system services within an investment model demonstrates a shift towards more flexible technologies. The resulting portfolios lead to reduced operating costs and CO2 emissions, and highlight the importance of clear long-term signals for investors.
      82
  • Publication
    Flexible storage operation in a market environment
    (EnergynauticsGmbH, 2014-11-13) ;
    Future power systems with high penetrations of variable renewables will require increased levels of flexibility from generation and demand-side sources in order to maintain secure and stable operations. One potential source of increased flexibility is large-scale energy storage, which can provide a variety of ancillary services across multiple timescales. In order for adequate investment to take place, it is essential that the correct market signals are present which encourage suitable levels of flexibility, either from storage or alternative sources. This paper explores the changes required in operational practices for storage plant at different levels of installed wind capacity, and the challenges that private storage plant operators will face in generating appropriate bids in a market environment at high penetrations of variable renewables. The impacts on system generating costs are explored under different operating assumptions.
      145
  • Publication
    Emissions from cycling of thermal power plants in electricity systems with high penetration of wind power: Life cycle assessment for Ireland
    The increase of renewable sources in the power sector is an important step towards more sustainable electricity production. However, introducing high shares of variable renewables, such as wind and solar, cause dispatchable power plants to vary their output to fulfill the remaining electrical demand. The environmental impacts related to potential future energy systems in Ireland for 2025 with high shares of wind power were evaluated using life cycle assessment (LCA), focusing on cycling emissions (due to part-load operation and start-ups) from dispatchable generators. Part-load operations significantly affect the average power plant efficiency, with all units seeing an average yearly efficiency noticeably less than optimal. In particular, load following units, on average, saw an 11% reduction. Given that production technologies are typically modeled assuming steady-state operation at full load, as part of LCA of electricity generation, the efficiency reduction would result in large underestimation of emissions, e.g. up to 65% for an oil power plant. Overall, cycling emissions accounted for less than 7% of lifecycle CO2, NOx and SO2 emissions in the five scenarios considered: while not overbalancing the benefits from increasing wind energy, cycling emissions are not negligible and should be systematically included (i.e. by using emission factors per unit of fuel input rather than per unit of power generated). As the ability to cycle is an additional service provided by a power plant, it is also recommended that only units with similar roles (load following, mid merit, or base load) should be compared. The results showed that cycling emissions increased with the installed wind capacity, but decreased with the addition of storage. The latter benefits can, however, only be obtained if base-load electricity production shifts to a cleaner source than coal. Finally, the present study indicates that, in terms of emission reductions, the priority for Ireland is to phase out coal-based power plants. While investing in new storage capacity reduces system operating costs at high wind penetrations and limits cycling, the emissions reductions are somewhat negated when coupled with base load coal.
      712Scopus© Citations 65
  • Publication
    Modeling demand response in the residential sector for the provision of reserves
    (Institute of Electrical and Electronics Engineers, 2012-07) ; ;
    Penetrations of variable renewable generation are increasing globally. While this trend is creating challenges for power systems, improved communication technologies are providing opportunities for the demand side to play a role in meeting some of these challenges. Commercial and industrial customers have long participated in demand response, but residential demand response is a largely untapped resource. Smart grid solutions provide the residential sector with the potential to respond to the systems needs over short time scales. A number of residential loads are well suited to providing reserves with minimal impact on consumers. In this paper the potential response from the residential sector in a heating dominated climate is estimated by modeling relevant responsive loads. The potential response is significant (6% of system demand on average). The aggregate interruptible load is expected to fall by approximately 19% by 2020. The modeling captures the daily and seasonal variations of the available resource.
      700Scopus© Citations 14
  • Publication
    Using energy storage to manage high net load variability at sub-hourly timescales
    High net load variability, driven by high penetrations of wind and solar generation, will create challenges for system operators in the future, as installed wind generation capacities increase to unprecedented levels globally. Maintaining system reliability, particularly at shorter time-scales, leads to increased levels of conventional plant starts and ramping, and higher levels of wind curtailment, with sub-hourly unit commitment and economic dispatch required to capture the increased cycling burden. The role of energy storage in reducing operating costs and enhancing system flexibility is explored, with key storage plant characteristics for balancing at this time-scale identified and discussed in relation to existing and emerging grid-scale storage technologies. Unit dispatches for the additional storage plant with varying characteristics highlight the unsuitability of energy only markets in incen-tivizing suitable levels of flexibility for future systems with high net load variability.
      433Scopus© Citations 63
  • Publication
    Efficient large-scale energy storage dispatch: challenges in future high renewables systems
    Future power systems with high penetrations of variable renewables will require increased levels of flexibility from generation and demand-side sources in order to maintain secure and stable operation. One potential flexibility source is largescale energy storage, which can provide a variety of ancillary services across multiple time-scales. In order for appropriate levels of investment to take place, and in order for existing assets to be utilized optimally, it is essential that market signals are present which encourage suitable levels of flexibility, either from storage or alternative sources. Suboptimal storage plant dispatch due to uncertainty and inefficient market incentives are represented as operational constraints on the storage plant, and the impact of these inefficiencies are highlighted. Thus changes required in operational practices for storage plant at different installed wind capacity levels, and the challenges that private storage plant operators will face in generating appropriate bids in a market environment at high variable renewable penetrations are explored. The impacts on system generating costs and storage profits are explored under different plant operating assumptions.
      491Scopus© Citations 51