Over the past decades significant progress has been made in the development of renewable energies, and technologies are now mature. Especially wind and solar photovoltaic power have achieved economies of scale through a combination of market support programs, technology improvements and mass production; the renewable energy industry has successfully moved into the mainstream. However, compared to the vast global potential of all renewable energy sources, the current market volume shows only a glimpse of what it could be in the future. While wind and solar photovoltaic power dominate the discussion around renewables, there is a huge variety of different technologies available, and each technology has a specific area of application.
Towards a Global Share of 100 Percent Renewable Energy Supply
The Intergovernmental Panel on Climate Change (IPCC) published in 2012 the most comprehensive data collection report about renewable energy currently available—the Special Report on Renewable Energy (Edenhofer et al. 2012). According to this survey, renewable energy technologies available today could supply two and a half times the present total energy demand from China or Europe, while Africa could generate two hundred times its energy demand with renewable energy. Thus, renewable energy potential is not a limiting factor to achieve full global supply.
Despite the Huge Renewable Energy Potential, Less Is More
Using energy efficiently is cheaper than producing new energy from scratch, and often has many other benefits. An efficient washing machine or dishwasher, for example, uses less power and saves water too. Efficiency in buildings doesn’t mean going without comfort—on the contrary, it should provide a higher level of comfort. For example, a well-insulated house will feel warmer in the winter, cooler in the summer and be healthier to live in. An efficient refrigerator is quieter, has no frost inside or condensation outside, and will probably last longer. Efficient lighting offers more light where you need it. Efficiency is thus really better described as “more with less.” There are very simple steps to achieve efficiency, both at home and in businesses and industries, such as updating or replacing separate systems or appliances that will save both money and energy. The biggest savings, however, don’t come from incremental steps but from rethinking the whole concept—the whole house, the whole car or even the whole transport system. In this way, energy needs can often be cut back by a factor of four to ten.
Energy efficiency is based on the following pillars:
- The implementation of best practice technologies and a certain share of emerging technologies, observing energy efficiency standards.
- Behavioral changes, e.g. reducing the average room
- Structural changes, such as shifts from individual fossil-
fuel cars towards electric public transport.
- Updating equipment and installations, replacing them the end of their (economic) lifetime, e.g. switching to LED lighting.
Thus energy efficiency is not a homogenous sector, and involves a large number of technologies and measures. While the renewable energy markets can be clearly defined with a small amount of technical and financial parameters, measuring the development of energy efficiency is complex. Without energy efficiency, the global demand would be 826 EJ/a – 251 EJ/a higher than today. In other words, the energy efficiency measures of the past twenty-five years saved the equivalent to China, India and Europe’s energy demand combined. Between 1990 and 2014 global primary energy intensity dropped continuously for more than two decades by an average annual rate of 1.5 percent. In 2015 energy intensity was more than 30 percent lower than in 1990. Nonetheless, global economic growth has been far greater, resulting in steady net growth in energy demand, which increased by 56 percent between 1990 and 2014 with an average annual growth rate of 1.9 percent.
Within the energy industry, the power sector experienced the most rapid changes over the past decade. Wind power is now among the cheapest new power plant technologies, and solar photovoltaic systems achieved grid parity in many countries. In 2015, every second newly built power plant was based on renewable energy technologies. The development of wind and solar photovoltaic power has been outstanding, and it already has significantly changed the way utilities operate.
In 2015, about half of the total world final energy consumption was used to generate heat (REN21 2016). The overall global consumption of heat energy over the past decade, however, only grew at an average annual rate of less than 1 percent. While cooling demand continues to increase as a result of improved energy access—manly in developing countries with warm climate and rising average global temperatures—the proliferation of highly energy-efficient buildings and passive solar architecture contributes to reduce heat demand. In the building sector, biomass and solar thermal energy account for the vast majority of modern renewable heat. By contrast, in the power sector the available statistical data for heating consumption is incomplete. Bioenergy dominates renewable heat production in the industry sector with around 10 percent of total demand.
While renewable power generation continues to enjoy double-digit growth rates, renewable heating and cooling technologies have grown at a much slower rate. This is partly due to the small-scale nature of this sector, as well as the multiple decision-making processes encountered primarily at the customer level. More complex, and therefore fewer, renewable energy support policies have also hindered growth in this sector.
But the greatest challenges in the switch from fossil fuels to renewables are found in the transport sector. There are three main entry points for renewable energy in this sector: the use of 100 percent liquid biofuels or biofuels blended with conventional fuels; the growing role of natural gas vehicles and infrastructure that can be powered with gaseous biofuels; and the increasing electrification of transportation.
A transition towards 100 percent renewable energy starts with a technical and modal shift. Three main measures must be adopted in order to develop a more energy-efficient and sustainable transport system in the future, with a focus on:
- Reducing transport demand.
- Shifting transport modes from high to low energy intensity.
- Improving energy efficiency through the development of technology.
The remaining energy demand will have to be fulfilled using sustainable biomass and by replacing combustion engines for electric drives in multiple vehicles. However, the shipping and aviation sector in particular, but also heavy-duty trucks and construction vehicles, cannot be electrified with the technologies currently available. Thus, fossil fuels must be replaced with synfuels, hydrogen and renewable methane produced from renewables. Electricity is required to produce these fuels, which will significantly increase future electricity demand. The European Environment Agency (EEA) commissioned an assessment that calculated the future impacts of greater electric vehicle use on Europe’s energy system, and associated emissions from the road transport and energy sectors (EEA 2016). Should the share of electric vehicles in Europe rise to 80 percent by 2050 the electricity demand will rise significantly. According to the research, the share of Europe’s total electricity consumption from electric vehicles will increase from approximately 0.03 percent in 2014 to around 4–5 percent by 2030 and 9.5 percent by 2050. By 2050, an additional power plant capacity of 150GW would be needed in order to charge all the electric cars of the European Union. Furthermore, this additional energy needs to be integrated into the grid infrastructure across Europe. The critical matters raised by this assessment are therefore how much electricity will be needed to cope with Europe’s added demand, what type of generation is used to cover this additional electricity demand, and how could charging peaks be managed.
Balance Variable Wind and Solar Generation with Inter-Sectorial Management and Storage
Currently, the power, transport and heating sectors are to a large extent separate, due to the different energy sources and infrastructures relevant to each of them. While the power sector is limited to the power grid, the heating sector depends largely on gas grids and—in some cases—district heating pipeline systems. The transport sector is currently disconnected from both the power and heating sectors, with its infrastructure primarily focused on the distribution of oil via tankers, pipelines and filling stations. Public transport, on the other hand, does already have links to the power sector, as the electricity used in trains, trams and the metro systems originates from the power sector.
With increased electrification, the power sector will progressively merge with the heating and transport sectors. At the same time, renewables do not need fuel, which will have a significant influence on oil, gas and coal mining companies. Finally renewable power generation—especially solar photovoltaic energy—may move closer to consumers and, if decentralized renewables continue to grow, may generate electricity in small units on the side of demand. Should this be the case, the capacity of a single centralized conventional power plant would be distributed across several thousand locations, which would require a significant change in the business model of traditional utilities.
Technology Trends for Renewable Power Management
Increased market share of renewable energies in the power sector necessitates more infrastructural changes and new power grid management. However the task of integrating renewable energy technologies into existing power systems is similar in all power systems around the world, whether they are large, centralized systems or island ones. Thorough forward planning is needed to ensure that the available production can match demand at all times. In addition to balancing supply and demand at all times, the power system must also be able to fulfill defined power quality standards such as voltage and frequency stability, which may require additional technical equipment in the power system and support from different ancillary services. Furthermore, power systems must be able to cope with extreme situations such as sudden interruptions of supply in case of a fault at a generation unit or interruption of the transmission system.
The integration of renewable energy into a smart grid changes the need for base load power. In countries such as Spain, Denmark and Germany as well as in South Australia, wind and solar power plants already provide more than 30 percent of daily demand on certain days. This redefines the need for base load power. Instead, the load has to be followed in the daytime and the night by a combination of flexible energy providers, such as solar photovoltaic systems complemented by gas, geothermal and wind sources, and demand management. Such a mix of different technologies can form a resilient power supply, but requires a significant change in the business model of utility companies.
Storage Technologies: The Cascade Approach
Once the share of electricity from variable renewable sources exceeds 30–35 percent, energy storage is necessary in order to compensate for generation shortages or to store potential surplus electricity generated during windy and sunny periods. Today, storage technology is available for different stages of development, scales of projects, and for meeting both short- and long-term energy storage needs. Short-term storage technologies can compensate for output fluctuations that last only a few hours, whereas longer term or seasonal storage technologies can bridge the gap over several weeks. There is no one-size-fits-all technology for storage. Along the entire supply and demand chain, different storage technologies are required to cover the exact needs in regard to storage time—from second reserve for frequency stability to seasonal storage of several months. A cascade of different storage technologies is required to support the local integration of power generation from variable renewable energy (VRE) in distribution networks, support the grid infrastructure to balance VRE power generation, and support self-generation and self-consumption of VRE by customers.
Generation Side Management for 24/7 Supply
Load varies over time and additional flexible power generating resources are required to provide the right amount of power. For rural areas, typical technologies are combined-cycle gas turbines (CCGT) or hydropower stations with a sufficient storage capacity to follow the daily load variations. The impact of adding renewable power generation to a conventionally centralized power system will affect the way in which a conventionally designed electricity system runs. The level of impact depends on the renewable energy technology (Teske et al. 2014). Biomass-, geothermal-, concentrated solar power plants (CSP) and hydropower with storage can regulate power output and can supply both, base and peak loads. Meanwhile solar photovoltaic, wind power and hydro power plants without storage depend on available natural resources, so the power output is variable. Sometimes these renewable energy sources are described as “intermittent” power sources; however, this terminology is not correct as intermittent stands for uncontrollable and non-dispatchable. In fact, the power output of these generation plants can already be forecasted with a high degree on certainty and power output can be reduced, hence they can be dispatched.
Conclusion: The Energy System of the Future Uses Cross-Sectorial Demand and Supply Management
New (battery) storage capacity is still expensive and unable to provide long-term seasonal storage; the most efficient hydro pump storage facilities cannot be expanded everywhere. Therefore, the interconnection of power grids with district heating pipelines, gas pipelines (for power-to-gas) and railway power lines offers a vast range of new possibilities. Storage of “surplus” wind and solar power in the form of heat via heat pumps or gas via electrolysis or in the batteries of electric vehicles, as well as demand management of numerous applications help to integrate more variable power generation capacity. The future energy system uses the full range of technologies across all energy sectors to distribute generation and manage demand. A utility company will therefore develop new business concepts and related support policies. The real challenge might not be the technologies, but a stable and consistent policy framework, which requires long-term thinking. The interconnection of systems offers new business opportunities and will most likely lead to a more resilient energy supply.
The research principal of the Institute for Sustainable Futures (ISF) at the University of Technology Sidney (UTS), he has published more than fifty special reports on renewable energy systems and their integration in the market, including the Global Energy Revolution scenario series and the market perspectives for Global Wind Power “Global Wind Energy Outlook”. He also was a lead author for the special report of the Intergovernmental Panel on Climate Change
(IPCC) on renewable energies, published in 2011, and he is a member of the group of consultants to the Japanese Renewable Energy Institute. Teske has also been on the reviewer for the International Energy Agency’s annual report on the World Energy Outlook (WEO), and moreover has experience in practical small-scale developments. In 1999, he founded the first power utility organised as a cooperative in Germany’s electricity market. For ten years he was the director of Renewable Energies for Greenpeace, leading five editions of the project Energy [r]evolution: A World Sustainable Energy Outlook, with joint research by the German Aerospace Center, the Global Wind Energy Council, and various nonprofit organizations.
Edenhofer, Ottmar, Rafael Pichs-Madruga, Youba Sokona, Kristin Seyboth, Patrick Matschoss, Susanne Kadner, Timm Zwickel, Patrick Eickemeier, Gerrit Hansen, Steffen Schlömer and Christoph von Stechow, eds. 2012. Special Report on Renewable Energy Sources and Climate Change Mitigation. Cambridge: University Press. http://www.ipcc.ch/report/srren/.
EEA (European Environmental Agency). 2016. “Electric Vehicles and the Energy Sector – Impacts on Europe’s Future Emissions.” http://www.eea.europa.eu/themes/transport/electric-vehicles
REN21. 2016. Global Status Report Renewables 2016. Paris: Ren21 Secretariat. http://www.ren21.net/status-of-renewables/global-status -report/.
Teske, Sven, Tom Brown, Eckehard Tröster, Peter-Philipp Schierhorn and Thomas Ackermann. 2014. powE[R] 2030. Hamburg: Greenpeace. http://www.greenpeace.de/files/publications/201402-power-grid