Energy Sector: issues, challenges and needs

Energy is an economic, environmental, social and political issue, and a balance between energy management, economic interests, and the environment care is needed for sustainable development. The world energy demand continues to grow and must be satisfied in an efficient and effective way. The tendency towards increased mobility, urbanization and industrialization, especially in developing countries, and an integrated global economy will further accelerate the worldwide energy consumption and dependence. Today, the primary means to meet the electrical energy demand is combustion of the fossil fuels (e.g. oil, coal, and natural gas). Figure 1 indicates the world total primary energy supply by source [1].

Although fossil fuels can produce a significant amount of energy, the main drawbacks of fossil fuel energy sources are their limited reserves and their negative effects on the environment. The climate changes induced by the impact on the environment, in particular, pose an additional challenge for energy suppliers, consumers and market operators. To fight climate change, i.e. to reduce the negative effects (e.g. greenhouse gases) of the traditional energy sources, the usage of the fossil energy sources should be replaced with alternative energy sources, i.e. renewable energy sources, which are cleaner and less harmful to the people and the environment.

Introduction

2 In general, the main goal of the energy systems should be to meet the energy demand at any time by reducing the environmental impacts, by developing consistent, reliable and clean forms of energy. However, energy market participants (investors, power producers, system operators, consumers, etc.) face some potential challenges [1]-[5]:

 growing energy demand

 new challenges in the energy consumption patterns

 integration of intermittent (stochastic) renewable energy sources into the electricity grids

 extracting fossil fuels under extreme conditions in a more economical and safer manner

 building up refining capacity

 reducing nuclear waste

 ensuring more reliable means for transporting electricity

Renewable energy is generated from natural renewable resources such as sunlight, wind, rain, tides, biomass and geothermal heat, i.e. naturally replenished with the passage of time, either through biological reproduction or other naturally recurring processes [4], [6]. As a non-polluting renewable energy source considerably cheaper than nuclear energy, wind energy, among the various candidates, has received fast growing attention throughout the world, and the utilization of wind power has increased dramatically over the past decade.

According to the Half-Year Report 2013 released by The World Wind Energy Association (WWEA) [2], the worldwide wind capacity reached 296 GW by the end of June 2013, out of which 13980 MW were added in the first half of 2013. According to the Annual Report 2012 of the European Wind Energy Association (EWEA) [7], the installed capacity in the European Union (EU) has increased from around 13 GW in 2000 to 107 GW in 2012. This meets the power needs of 57 million households, and it is equivalent to the output of 39 nuclear power plants [7]. This continuous and rapid growth indicates that wind energy represents a popular, respectful of the environment and sustainable solution for meeting the increasing need of electricity. For exemplification, the Western Denmark region has one of the highest wind power penetrations in the world, consistently between 25 and 30% over the last few years [5].

Introduction

3 According to the BP Statistical Review of World Energy, oil remains the world’s leading fuel source representing 33.1% of global energy consumption by 2012. However, it had the weakest global growth rate among fossil fuels for the third consecutive year [3].

The evolution from conventional power grids towards grids with integration of distributed renewable energy sources leads to additional uncertainty in the system. Indeed, the challenge of reliably and safely operating power systems increases with the proportion of intermittent renewable energy (e.g. wind, solar, etc.) which is fed into the energy grids.

From the supplier side, particularly, the integration of renewable energy sources (e.g. wind and solar) into the grid imposes an engineering and economic challenge, because of the limited ability to control and dispatch these energy sources due to their intermittent characteristics.

Figure 1. Total primary energy supply by source (source: World Energy Resources Survey 2013) [1].

It is worth pointing out that the use of wind energy will continue to increase: the World Wind Energy Association (WWEA) has predicted a possible wind capacity of more than 700000 MW by 2020 [8]. As an exemplification to the country level, Denmark proposes to

Introduction

4 meet more than 50% of its electricity supply with renewables by 2020, 100% of electricity and heat by 2035, and 100% of transport by 2050, whereas Scotland has a mandate to achieve 100% renewable power supply by 2020 [9]. These projections enhance the importance of the reliable integration of large amount of wind energy to the power grid without harming its reliability.

In Table 1, we report the major advantages and drawbacks/challenges in the exploitation of wind energy [5], [10]. Wind speed is a highly variable meteorological variable with instantaneous, hourly, diurnal and seasonal variations, thus producing volatile power delivery. The volatile nature of wind poses a problem of predictability for wind turbine operation and energy system management. Then, a prediction model must be introduced, capable of providing also information on the uncertainty of the prediction, for informed decision-making.

Along these lines, in this Ph. D. work, we provide a useful framework for prediction and pertinent uncertainty quantification.

Table 1. Some advantages and challenges of wind energy.

Advantages Challenges

 Clean (no impact on the environment)

 Free and unlimited source

 Can be easily used by single households in small towns and villages

 Economical (one of the lowest-priced renewable energy technologies available today)

 Can be built on farms or ranches, thus benefiting the economy in rural areas

 Relatively simple technology

 Dependent on the availability of wind

 Limited predictability owing to intermittent character, inherent variability and

uncertainty of the wind

 Requires high initial investment

 Pollution deriving from turbines manufacturing

 Wind turbines are noisy