Sustainable Energy and Smart Grids: Breakthrough in Thinking, Modelling, and Technology

As renewable electricity generation increases, additional transmission infrastructure is required to deliver generation from cost-effective remote renewable resources to load centers, enable reserve sharing over greater distances, and smooth output profiles of variable resources by enabling greater geospatial diversity. NREL - Renewable Electricity Futures Study, 2013

Figure 2. Estimates of global energy consumption and global electrical energy consumption in 2012

Figure 2 gives estimates of global energy consumption. This table shows that about 13 percent of total energy consumption is used in the form of electrical energy. This percentage will grow in the future, with the Internal Energy Out- look 2013 expecting that in the period 2010-2040 world energy consumption will grow 56 per cent whereas world electricity consumption will grow 93 per cent (EIA, 2013).

Figure 3 gives estimates of the most important sustainable energy sources. There are some other sustainable energy sources, such as energy from ocean currents, ocean waves and the salinity gradient between salt and sweet water. However, these sources are in such an early stage of development that they do not yet make a significant contribution. Most sources produce electrical energy (hydro, wind, solar) and other sources produce heated water (solar, geothermal) or fuels (biomass).

Figure 3. Estimates of the use of sustainable energy sources in 2012 (based on Wikipedia, IEA wind 2012 annual report). For comparison: the amount of electricity Generated by nuclear sources is 2620 TWH

Comparison of figures 2 and 3 shows that until now only 3 per cent of our energy consumption is produced in a sustainable way (sun and wind: 0.04 per cent). In other words, at the moment we are still far from being a society based on renewable energy.

Of course sustainable intermittent energy sources present an additional challenge, not least because there is a limited amount of electrical energy storage devices in the grid. The Sandia Report (2013) presents the most comprehensive analysis of the technologies, current and future applications, and uses of energy storage systems in electric grids. Through fast control techniques and technologies, production has to be equal to consumption (the power bal- ance has to be kept) in order to maintain the frequency and stability of the grid. In the current system, this balance is kept by automatic control systems mainly via thermal power stations, where the consumption of electrical energy is automatically balanced by the production of electrical energy by adapting the consumption of coal, oil or gas to demand (see figure 4). In possible future power systems, with fewer thermal power stations, this power balance must be kept via energy storage devices, because most of the sustainable energy sources (such as wind, solar, ocean wave, and tidal energy) have an intermittent nature. This means that they are not continuously available: if there is no wind, there is no wind energy. To keep the power balance in these grids without thermal power stations, it may be necessary to have forms of energy storage and to control the loads.

To understand the characteristics of the various forms of renewable energy we will discuss the most important sources in more detail. We will focus on hydro, wind and solar energy. We also will discuss one new source with a high potential: ocean wave energy.