«Electricity: The key to a sustainable and climatecompatible energy system A study by the Deutsche Physikalische Gesellschaft e. V. (German Physical ...»
The key to a sustainable and climatecompatible energy system
A study by the Deutsche Physikalische Gesellschaft e. V.
(German Physical Society)
(Translation December 2011)
The key to a sustainable and climate-compatible
A Study by the Deutsche Physikalische Gesellschaft e. V.
(German Physical Society)
(Translation December 2011)
The effects of the anthropogenic climate change pose some of the greatest challenges faced by our global civilisation. If carbon dioxide (CO2) production during energy supply is not drastically reduced, there will be grave changes throughout the world. The introduction of a climate-responsible energy supply, therefore, is one of the “great challenges” of this century. The natural sciences, in particular, are required to search for effective solutions across national borders and scientific disciplines, develop them and bring them to fruition.
Accordingly, the German Physical Society (Deutsche Physikalische Gesellschaft, DPG) considers it its responsibility to examine the possibilities and prospects of avoiding CO 2 emission from energy generation and consumption. This study, “Electricity: The Key to a Sustainable and ClimateCompatible Energy System”, was conducted by the Working Group on Energy (Arbeitskreis Energie, AKE) of the DPG. With this study the DPG, as a scientific society, aims at providing a contribution to the discussion on climate and energy policies in the German and European contexts.
Climate-responsible energy supply is a complex interdisciplinary issue which cannot be solved by the methods and facts of physics alone. Knowledge of these facts and methods, however, is the indispensable basis of necessary political decision-making. This study focuses on this basis and, rather than making recommendations, attempts to present the spectrum of possible options and their physical background. A factual analysis of energy supply and utilisation was conducted with regard to the first half of the 21st century. Although this study makes no claim to completeness, it examines all major options in developing a carbon-lean energy system. In particular, it demonstrates that electric energy has been playing, and will continue to play, an increasingly important role in the interplay of the various forms of energy.
Fundamental physics plays the decisive role in determining the various technological options possible.
Expertness, innovation, strategic thinking and perseverance are called for in order to successfully realise these options. The DPG will continue to provide its expertness in order to meet these great societal challenges.
Wolfgang Sandner Martin Keilhacker
Climate change with its potentially serious dangers to mankind requires restructuring of the world’s energy supply for the purpose of drastically reducing CO2 emission. This study presents an overview of present electricity utilisation and a forecast of the role electricity could play in a modern society such as Germany’s that is intent on CO2 avoidance during energy generation and consumption. There are many indications that the importance of electricity in the interplay between the various forms of energy will continue to increase in the coming decades.
Generally speaking, this study takes as its starting point the state of affairs presented in the German Physical Society’s 2005 publication “Climate Protection and Energy Supply in Germany 1990-2020 (“Klimaschutz und Energieversorgung in Deutschland 1990-2020”) and examines the general situation in Germany up until about
2030. Where appropriate, the situation is presented in the wider context of the European Union or, indeed, the world, and the time horizon is extended to about 2050. However, this study makes no claim to being a complete analysis that devotes equal attention to all possible issues, but rather seeks to highlight those aspects that are of particular importance to the future development and t o address issues that may benefit from considering a change of direction or priorities.
This study is divided into three parts: utilisation, supply and distribution of electric energy. It concludes with an outlook on the role of electricity in a future sustainable and climate-compatible energy system.
1 Utilisation of electric energy Utilisation sectors – Electricity demand is going to increase The share of electricity in Germany’s end-use energy consumption is currently about 22%. It is statistically recorded by utilisation sectors. The largest consumer is the industrial sector (43%), followed by private households and the business, trade, and services (BTS) sectors (27% each). Electricity consumption has been increasing in all of these sectors, most notably in the BTS sector. A very small fourth sector (at 4%) is transportation, in which electric energy has hitherto played a role solely with regard to railway transportation.
Electricity consumption by private households is caused by a variety of electric and electronic devices. In many respects, there is potential for energy saving: Replacing energy-inefficient devices, reducing standby losses and, amongst other things, replacing light bulbs in the area of electric lighting, this, however, being relatively unimportant. This cannot compensate, however, for the additional consumption of a continuously increasing number of devices and second sets – changes in consumer attitudes will have the greatest effect on energy saving. In the BTS and industrial sectors, the development of energy consumption is governed by economic growth for the most part; however, it is reduced by further and possibly substantial improvements in energy efficiency. Overall, electricity consumption, and thus the importance of electricity in the energy mix, is expected to continue to increase in the long run – estimates range around 1%-1.4% per annum.
Heating with small temperature differences – Expediency of electrically powered heat pumps When providing low-temperature heat for buildings (which accounts for 70% of the end-use energy consumption of private households), one has a large energy-saving potential which can be realised on the principle of “heating with small temperature differences”. Possible applications are combined heat and power (CHP) and heating using electrical heat pumps (see also chapter II.3 on CHP).
For the three basic functions of the “warm house” energy service – i.e. heating, ventilation and hot water generation – just one-third of the energy required for “conventional heating” would be sufficient. In order to keep the primary energy input as low as possible, an integrated concept is needed: Once thermal renovation of the building, including design of heating surfaces at low temperatures (floor heating or panel heating) and utilisation of “free” energy sources (solar power, waste heat, etc.) has been implemented, the remaining very low heating energy demand can be well met by electrical heat pumps.
Prospects and problems of electromobility – Key element: batteries of high energy density Electrically powered vehicles, or more generally, the electrification of traffic (catchword “electromobility”) can reduce the consumption of mineral oil and climate-impairing CO2 as well as pollutant emission, provided the electric energy is not generated from fossil fuels. One great advantage of the battery-powered electric drive is its high efficiency (70-80% compared with 20-28% for combustion engines). However, this notion is put into perspective when, amongst other things, the efficiency of electricity generation, the energy invested in producing the battery and losses during load cycles are taken into account.
The central requirement is the development of suitable batteries: Even the most advanced lithium-ion batteries lag a factor of about five behind the target values in energy density and production costs, and despite great efforts in research and development there is no guarantee of success. It will thus take at least twenty more years, even under favourable conditions, before battery-powered electric cars are able to play a significant role in the market. The extent to when the vision of integrating electric cars into an “intelligent” grid and using their batteries as storage for fluctuating renewable energy sources can be realised, also remains to be seen.
Whether electromobility, be it battery-powered or fuel cell-powered, will play the role widely expected, has to be proven in competition with the “conventional” combustion engine (petrol or diesel), which is still expected to have considerable potential for development with regard to energy saving and CO 2 reduction (estimates assume 20-30% over the coming years).
2 Supply of electric energy – Various possibilities for a future energy mix Fossil-based thermal power plants – Necessity for CO2 separation and storage The use of coal (and increasingly of natural gas, combined about 63%) is predominant in thermal power plants worldwide and will continue to be so for many decades – at the same time, the burning of coal is the main cause of anthropogenic CO2 emission. A further increase in the efficiency of power plants and/or the transition from coal to natural gas could reduce CO2 emission from Germany’s fossil-based power plant fleet by possibly 15% and 25%, respectively, by the year 2030. However, the breakthrough necessary for meeting climate protection targets can only be achieved with the help of carbon capture and storage (CCS) technology.
Emission could thereby be lowered to 100 g CO2/kWh, equivalent to a reduction of almost 90% as compared with 1990.
There are several promising procedures for separating CO2. However, all of them still need to be developed to industrial maturity and tested in demonstration plants – their general implementation will therefore only be possible in some 10-15 years at the earliest, possibly even not prior to 2030. It is hoped that by that time renewable energy systems will be able to contribute a considerable share of the overall electricity supply.
Otherwise, energy demand will still have to be met by the energy sources currently available.
While there will be technological solutions to the separation of carbon dioxide, its long-term storage is a much greater problem. Storage is envisaged in leak-proof geological formations: depleted mineral- oil or natural- gas fields, for which there is, however, only a limited storage volume available in Germany, and in so-called aquifers. Furthermore, the safety and effectiveness of this storage method remains to be proven and the consent of the affected general public still has to be won.
CCS technology has its price: The current state of the art reduces efficiency by 8-14 percentage points and thus increases fuel consumption, depending on the efficiency of the power plant, by typically 20-35%.
Nuclear power plants – The only carbon-lean energy source so far apart from renewable energies To some extent, there has been a reassessment of nuclear energy worldwide. International organisations (the IAEA, IEA, OECD/NEA, the EU and the IPCC) consider an increasing contribution of nuclear energy to the electricity supply to be necessary over the next few decades. The crucial factor in this assessment is, above all, climate compatibility, besides the issues of cost-effectiveness and security of supply. However, reservations about nuclear energy, primarily concerning disposal and operating safety, exist in various countries to varying degrees. Utilisation of nuclear energy is thus a political issue that is differently assessed by different nations.
Life cycle analyses of CO2 emission from various power plant types show that nuclear energy is nearly carbon-free, similar to wind and hydro power. From a technical point of view, Germany’s nuclear power
plants are able to support the extension of fluctuating regenerative electricity generation via controlling power:
they are designed for fast load changes in the upper power range (between 50 and 100% nominal power) and can also be operated in co-generation (CHP) mode.
Nuclear energy could significantly contribute to carbon-lean electricity supply in Germany, at least in the next two decades. It could also help to gain time for developing and introducing CCS technology. In particular, the loss of carbon-free electricity generation could be avoided through utilisation of nuclear energy in case the climate protection goals of the German government cannot be met within the fixed period of time despite speedy expansion of renewable energies. In that case, political deliberations about meeting climate protection goals, on the one hand, and the risks of nuclear energy, on the other, play a role beyond the factual aspects of this study.
The remaining CO2 emissions are due to the amount of fossil energy required for construction and fuel processing. They will be reduced in the long term when changing over to an energy system operating with less fossil fuel.
Utilisation of nuclear energy would thus have to be part of an integrated concept of energy and climate policies which would also have to determine the next and increasingly urgent course of action for disposal of highly radioactive waste.
Combined heat and power generation and system comparison – Putting the advantages into perspective Co-generation and utilisation of heat and electricity in combined heat and power (CHP) facilities is intended to improve fuel utilisation. It is regarded as an integral part of meeting the CO 2 reduction goals set by politics and the public (which is why the share of electricity from CHP is to be doubled to 25% by 2020). However, this study shows that many CHP facilities fall short of this expectation: A comprehensive comparison with separate electricity generation in a CCGT power plant and decentralised heat via a condensing boiler shows that the CHP facilities considered are only marginally better and, in some cases, even somewhat worse. Comparing a combination of a CCGT facility and decentralised electric heat pumps (with electricity from the CCGT facility) shows the CHP facilities examined to be even generally significantly inferior.
This example demonstrates that it would be a much more expedient energy policy to give incentives in general, e.g. by a “linear energy savings tariff” for energy savings which can actually be proven, rather than prescribe certain technological solutions.