The move towards cleaner energy and the increase in demand for electricity has created a drive towards modernising electricity grids. Achieving a clean and secure electric power system requires building grids that can accommodate large amounts of renewable energy sources. The consensus, within the literature, is that the most cost effective way of doing this is to create 'smart' grids. This feasibility sets out to demonstrate that battery energy storage technology can integrate with traditional electricity distribution and renewable energy sources. By increasing the flexibility with which distribution grids can be managed, battery energy storage technology can boost the output of smart grids and spur new markets. The resulting economic and environmental benefits would meet the growing needs of stakeholders along the electricity value chain.
The generation of electricity from wind and other renewable sources has increased over the last decade. According to Mohod et al (2011), the worldwide capacity of wind energy has reached 159, 213 MW, adding 38, 312 MW between 2008/9 and 2012. This, they add, shows that wind capacity doubles every three years.
Energy storage is gaining a lot of industry interest as a way of integrating renewable sources into the system. This is because it has the advantage of increasing the flexibility of grid operations whilst maintaining the reliability and robustness needed to meet the projected increase in the demand for clean energy sources (Kintner-Meyer et al, 2012).
In the United Kingdom, there is still a significant gap between energy storage technology and policies aimed at reducing carbon emissions. This is partly due to the limitations inherent in renewable sources such as solar, wind and wave, which are dictated by meteorological factors (Taylor et al, 2012).
1.1 Motivation / Rationale
I first became interested in energy storage technology while working as a power systems engineer for National Grid. Over the eleven years of my employment with National Grid I have became increasingly intrigued and fascinated by sustainability and environmental legislation. However, it was in my current role as project manager that I began to focus my interests in the area of battery energy storage.
In 2009, whilst working on the Severn Barrage feasibility study, I began to research the progress being made in battery energy storage. During my initial reading, I came across an article by Professor Phil Taylor, of Durham University's School of Engineering & Computing Sciences, in an ABB customer newsletter called Ffwd which explained that energy storage technology is a vital element of future grid developments. The magnitude of what could be achieved through energy storage was demonstrated in a 153 MW Notrees wind farm project in Texas. The $43 million project was reported in a news paper article as follows:
"Energy storage truly has the potential to serve as a 'game-changer' when it comes to renewable power … Through this project, Duke Energy intends to show that renewables can play an even bigger role in our country's energy future."
As environmental legislation becomes tighter, for example through: Climate Change Act (2008); Large Combustion Plan Directive (2001) and European Union Air Quality, there has been a need to change the generation mix dynamics in order to incorporate more renewable energy sources.
I am excited to say that on the 23rd Jan 2013 Duke Energy Renewables announced the completion of the 36 MW energy storage and power management systems at its Notrees wind power in Texas. The system completed testing and became fully operational in December 2012.
1.2 Structure of Dissertation
Chapter 1 Introduction
Chapter 2 Literature Review
Comparative assessment of different battery technologies
Economic assessment of battery energy storage
Chapter 3 Methodology
Quantitative Analysis using Matlab and Simulink
Analysis of simulation results
Chapter 4 Discussions, Recommendations and Conclusions
References
Bibliography
Appendix
A1 Health and Safety risk assessment
1.3 Aims and Objectives
As I have already stated, the objective of this project is to examine the viability of battery energy storage as a solution to electrical systems challenges. This requires giving consideration to three main elements: complex and variable demand profile; varying generation profile and the inertia of lower system. In order to achieve this objective, the following aims have been set:
To investigate the effectiveness of different types of battery energy storage technologies. This will be achieved by conducting a comparative analysis / assessment of five battery storage technologies.
To evaluate the economic and environmental costs associated with the different battery energy technologies. This will be done by reviewing the literature in order to highlight the progress that has been made with each battery storage technology.
To examine whether there are any integration issues that could cause potential barriers to the development of increased battery energy storage. This will be achieved by simulating battery storage technologies using Matlab and Simulink. This will identify whether technological issues might present barriers. I will also review the literature to highlight the impact of issues such as legislation and user consumption.
2. Methodology
The purpose of the dissertation will be to analyse the possible use of battery cell storage for Wind farms in the future as we start moving towards a smart grid and as we are all becoming more conscious of the energy that we use and when.
The dissertation will concentrate on frequency response and cost benefit analysis of implementing battery cells in the electricity industry for wind farms.
Literature review to summarise documented work approach of Battery Energy Storage and the wider area as appropriate.
Literature review to investigate the effectiveness of different types of battery energy storage technologies.
Complete a comparative assessment of the five main battery storage techniques, - lead acid, sodium sulphur, Lithium ion, Metal air and flow batteries.
Complete an economic assessment of Battery Energy Storage for use with wind turbines.
Quantitative analysis once a typical network for study has been developed using Matlab and Simulink. This is called model based design and is a mathematical and visual way of designing complex control systems. The dissertation will aim to investigate / access the role of battery energy storage on frequency control.
Learn Software
Compile suitable data
Model suitable scenario / scenarios
Analyse
Simulate the plant and controller
Build and test suitable models
2.1 Software to be used for Simulations
MATLAB is a high performance language used for technical computing. It integrates computation, programming and visualisation in a user friendly environment. Problems and solutions are shown in mathematical notation.
SIMULINK is a software package that is used to simulate models and analyse dynamic systems. It supports linear and nonlinear systems, modelled in sample time, continuous time or a combination of the two.
3. Literature Review
This section is a literature review of relevant material. Further and more detailed literature review will be carried out in the dissertation.
In 2008, the United Kingdom introduced a carbon reduction plan (Climate Change Act, 2008), with a target of reducing carbon emissions by 80% (from the 1990 baseline) by 2050. However, the gap between technology and policy means that this target is unlikely to be achieved without investment in alternative energy sources, including renewable, nuclear and coal / gas combustion. Given that electricity consumption has increased in recent decades (Delille et al, 2009), there is a need to find sustainable solutions. According to Wilson et al (2010), one possible solution is to provide greater energy storage within electrical networks.
Current outputs of electricity are generated by a small network of large scale power stations linked to a central grid. However, as Abu-Sharkh et al (2006) note, while this is a robust and reliable system of producing electricity, it is not the most efficient. This is because a lot of heat is lost during the generation of electricity. Indeed, Abu-Sharkh et al (2004) assert that producing electricity by integrating small scale generators into micro grids located in close proximity to the energy users, will offer better fuel efficiency and environmental benefits.
The challenge is that any alternative method of generating electricity must also meet consumption demands in a modern industrialised economy. Sinden's (2007) study of the relationship between renewable energy output and the demand for electricity in the UK revealed that renewables that depend on tidal, wind, solar radiation or wave energy do not often follow load. Given their low or zero inertia, renewable energy sources can be very unstable and sensitive to power fluctuations. This makes them unreliable as their outputs cannot be increased to match demand.
Using battery storage to achieve reductions in energy emissions is well documented within the literature. For example, in their article on energy storage in the UK electrical network, Wilson et al (2010), point out that the shift to low carbon electricity is predicated on the deployment of energy storage technologies that can seamlessly fit into the existing network paradigm.
Without an effective storage component, the UK electricity industry remains susceptible to three main conditions: 1. Reduced reliability and stability; 2. Poor security; and 3. Raised volatility (see, Holmberg et al, 2010). Given the prohibitive costs involved in storing electricity directly, the alternative is to store it in forms that can be converted back to electricity when it is needed (Pudjianto et al, 2013).
Research shows that the average usage of power facilities is about 55%, while transmission systems are used for about 60% of the time (see Strbac, 2008; Makansi and Abboud, 2002). Better efficiency can be achieved by utilising battery storage technologies. This can be done by bridging power; enhancing energy management and improving quality and reliability (see, Roberts, 2009; Taylor, 2010).
In terms of economic benefits, battery storage technologies can help minimise volatility by providing electricity during shortages and storing it when there is excess production. This will enhance industry efficiency by increasing the use of existing assets. The resulting economic benefits can be reinvested to increase the availability and quality of electricity. Additionally, access to stored and readily available electricity will minimise disruptions that can affect the entire grid.
Developments within the electricity industry suggest that energy storage technology is the key to future development in renewable energy (Bathurst and Strbac, 2003). This is not to suggest that energy storage technologies are not without challenges. For example, Divya and Ostergaard (2009) reviewed the different storage technologies, their applications and limitations and found that very few had been implemented in practice. The two main reasons for this were:
Conventional power systems had large amounts of generating sources which operated in an inter-connected manner and could be easily varied to match the load demand. Consequently, companies found it difficult to justify the economic gains obtained in using storage technologies.
There was a lack of practical experience and tools to be used to optimise operational costs and to assess the benefits of storage technologies during planning.
It is important to state here that there are many types of energy storage technologies available to the electricity industry. However, it is not within the scope of this study to consider all available storage technologies. Given that my project seeks to explore the effectiveness of battery storage technology, the rest of this review will focus on examining the progress that has been made with battery storage technology.
Quite apart from the fact that batteries have been widely used as standby applications, there has been considerable development in battery technology. Batteries are rated in terms of their energy and power capacities. Although these capacities are not independent, they are fixed during the battery design and are enhanced by features such as: efficiency; lifespan; depth of discharge; operating temperature; self discharge and energy density (Divya and Ostergaard, 2009; Lippert, 2007).
The batteries currently used in power system applications are deep cycle batteries with energy capacities ranging from 17 to 40 MWh and efficiency of about 70 to 80 percent. Studies show that there are five main battery technologies that are suitable for power system applications: Lead acid; Sodium sulphur; Lithium ion; Metal air and Flow batteries. These will be compared and discussed in greater detail in the dissertation.
One of the key advantages of using battery storage technologies is that batteries have relatively small voltages and capacities. This makes it possible to construct a wide range of energy storage systems by adding extra modules when needed, as opposed to replacing a whole system. Batteries are simple to install and, other than ensuring that normal safety precautions have been taken, they generally require only bolted connections.
Coupled with the small voltages and capacities, their charge and discharge profiles make them suited for the intermittency and non-controllability of renewable energy systems (Green and LIppert, 2007; Black and Strbac, 2006). These benefits can be harnessed by supporting utility-scale electrical energy storage, through effective frequency response and control (Kaltschmitt, Streicher and Wiese, 2007).
3.1 Frequency Response and Control:
This is an area that will be reviewed in detail in the dissertation, especially in terms of wind turbines and their generating variability and how battery energy storage may be utilised.
In the UK National Grid is responsible for the frequency response and control. This is managed through the purchasing of ancillary services from generation companies. All large generators connected to the England and Wales network must have the technical capability to provide frequency control under the Grid Code.
The system frequency of England and Wales network is maintained within the range of 49.8 Hz - 50.2 Hz (as shown in Figure X) under normal condition in order to meet the statutory requirements specified by the Grid Code.
Figure 1: Frequency Control Limits for England and Wales (National Grid Infonet)
The frequency delivered to the consumer must not vary from the declared value by more than ±1% in as per the Electricity Supply Regulation 1989 and National Grid Transmission License. The frequency service must be automatic. It can be divided into two categories; there are continuous services and occasional services.
3.1.1 Continuous services
The generator output is continuously adjusted as the demand varies to control the system frequency. The balancing of the generation against load is achieved on a second by second basis.
3.1.2 Occasional services
Occasionally the system frequency may drop below it's continuously control limit when there is a connection of a large load or sudden failure in generation as shown in Figure 1. The rate of frequency drops is mainly determined by the total angular momentum of the system. In those cases, response from generating plants and load reduction is then used. These generators that have agreed to provide frequency response increase their output through the governor action and the load of certain customers may be shed by low frequency relays. These occasional response services can be divided into primary and secondary responses.
3.1.3 Primary Response
Following a loss of generation, the initial short-term automatic power output increase to the negative frequency change is termed primary response. The primary response from synchronised generation has to be released increasingly over time, through automatic governor action, in the period 0-10 seconds after the incident and sustained for a further 20 seconds.
3.1.4 Secondary Response
The automatic positive power response in the subsequent frequency stabilisation phase beyond 30 seconds to 30 minutes after the incident is termed secondary response.
4. Project Plan
The planning stage of any project is extremely important to ensure that it is clear what needs to be done and when. It is very easy to procrastinate and go of track and having a plan and other visual aids is extremely useful to ensure that the project is completion on time.
As well as the project plans that I have created in Microsoft project I am also using a calendar at home and each week I mark up what I need to do each day and what other activities / appointments that I have.
On a weekly basis I will be reviewing and updating the project plan and ensuring that I am still on track. Should I start to fall behind I will look at why this is and try to minimise this and discuss this with my supervisor.
Pre Feasibility Project Plan
Feasibility and Dissertation Project Plan
I have taken 3 ½ months off work to enable me to fully concentrate on this dissertation and also completing the NEBOSH General Certificate. I have done this as I was struggling to balance the demands of a full time job with lots of responsibilities and travel commitments, family life and my studies. I have also planned to submit my dissertation on the 2nd August 2013 which is just over a month before submissions have to be in. This gives me a float of just over one month for any delays and uneventualities.
5. Discussions
References
Mohod, S. W., Hatwar, S. M., and Aware, M. V (2011) Grid Support with Variable Speed Wind Energy System and Battery Storage for Power Quality. Energy Procedia, Vol. 12: pp. 1032 - 1041.
Kintner-Meyer, M., Balducci, P., Colella, W., Elizondo, M., Jin, C., Nguyen, T., Viswanathan, V and Zhang, Y (2012) National Assessment of Energy Storage for Grid Balancing and Arbitrage: Phase 1, WECC.
Taylor, P., Bolton, R., Stone, D., Zhang, X., Martin, C and Upham, P (2012) Pathways for Energy Storage in the UK. Yorkshire, United Kingdom: Centre for Low Carbon Low Carbon Futures
Abu-Sharkh, S., Arnold, R. J., Kohler., J., Li, R., Markvart, T., Ross, J., N., Steemers., Wilson, P., and Yao, R (2006) Can Microgrids Make a Major Contribution to UK Energy Supply? Renewable and Sustainable Energy Reviews, Vol. 10: pp. 10 - 127.
Bathurst, G. N and Strback, G (2003) Value of Combining Energy Storage and Wind in Short-term Energy Balancing Markets. Electric Power Systems Research, Vol. 67: pp. 1 - 8.
Black, M and Strbac, G (2006) Value of Storage in Providing Balancing Services for Electricity Generation Systems with High Wind Penetration. Journal of Power Sources, Vol. 162: pp. 949 - 953.
Divya, K. C and Ostergaard, J (2009) Battery Energy Storage Technology for Power System: An Overview. Electric Power Systems Research, Vol. 79: pp. 511 - 520.
Green, A and Lippert, M (2007) Batteries - A Vital Element in Renewable Energy. A Saft White Paper. Bagnolet, France: Saft Renewables.
Holmberg, M. T., Lahtinen, M., McDowall, J and Larsson, Tomas (2010) SVC Light with Energy Storage for Frequency Regulation. IEEEE Conference on Innovative Technologies for an Efficient and Reliable Electricity Supply.
Kaltschmitt, M., Streicher, W., and Wiese, A (Eds.) (2007) Renewable Energy: Technology, Economics and Environment: Springer.
Makansi, J and Abboud, J (2002) Energy Storage: The Missing Link in the Electricity Value Chain. An ESC White Paper; United States: The Energy Storage Council.
Pudjianto, D., Djapic, P., Aunedi, M., Gan, C K., Strbac, G., Haung, S and Infield, D (2013) Smart Control of Minimising Distribution Network Reinforcement Cost Due to Electrification. Energy Policy, Vol. 52: pp. 76 - 84.
Roberts, B (2009) Capturing Grid Power: Performance, Purpose and Promise of Different Storage Technologies. IEEE Power and Energy Magazine, July / August Edition.
Sinden, G (2007) Characteristics of the UK Wind Resource: Long-term Patterns and Relationship to Electricity Demand. Energy Policy, Vol. 35: pp. 112 - 127.
Strbac, G (2008) Demand Side Management: Benefits and Challenges. Energy Policy, Vol. 36: pp. 4419 - 4426.
Taylor, P (2010) Electrical Energy Storage: Simulation to Deployment. United Kingdom: Power and Productivity for a Better World - Conference paper.
Wilson, I. A. G., McGregor, P. G and Hall, P. J (2010) Energy Storage in the UK Electrical network: Estimation of the Scale and Review of Technology Options. Energy Policy, Vol. 38: pp. 4099 - 4106.
National Grid Internal Intranet
Legislation
Department of Energy and Climate Change (2008) Climate Change Act. London, United Kingdom: Her Majesty's Stationary Office.
Bibliography
