Energy and Sustainability On a global scale, sustainability requires the closing of all materials cycles. A living earth in which circular flows of matter are sustained, requires a contiuous influx of energies driving these cycles. As the sun is the only inexhaustible source of energy on a human time scale, sustainable energy development must aim at utilizing renewable energies (which mostly are derived from solar energy), while at the same time minimizing the production of waste and the use of non-renewable resources. Research on materials cycles therefore focuses on the retrieval of energy and secondary resources from waste (e.g., metals and inert construction materials), and on the upgrading of waste byproducts.
Renewable energies An immediately available option is the indirect harvesting of solar energy, by utilizing the energy content of waste biomass. Work at PSI focuses on the gasification of scrap and contaminated wood, with the aim of producing electricity, heat, hydrogen or methanol as synthetic chemical energy carriers. Use of solar energy has to address the facts that the locations (sun belt) and times (summer, daytime) of high solar irradiation are not coincident with the energy demand. Therefore, conversion of solar energy into a transportable storage form is a major long-term research aim at PSI. High temperature solar chemistry, in which solar energy is used to produce chemicals with a high energy content or heating value, may provide an answer to the mentioned problems.
Energy storage Hydrogen, which may be derived from renewable sources such as hydro-electricity or solar chemistry, is likely to represent an important energy carrier in future supply systems. Methods for the storage of hydrogen in the form of liquid secondary energy carriers (synthetic fuels) are being developed at PSI. Catalytic synthesis of methanol from carbon dioxide and hydrogen represents one of several options. In this process, a liquid fuel (methanol) is produced and utilized in a CO2 neutral overall cycle. Short, medium and long term storage of electric energy is of high importance for a variety of technological applications, including transport applications and power supplies for devices. Research at PSI focuses on the development of advanced rechargeable battery systems with superior energy and power densities. The zinc / air battery is attractive in terms of both specifiactions and availability of the materials. Lithium batteries based on Lithium insertion electrodes offer superior power densities and energy storage characteristics. Electric Double Layer Capacitors (supercapacitors or ultracapacitors) are being developed for short term energy storage, e.g. in hybrid vehicles.
Efficient and low emission energy use Efficient use of fossil fuels represents one of the most significant contribution towards the aim of reducing global CO2 emissions. In its 'Program on Advanced Combustion Research' carried out in collaboration with ETH Zürich, PSI investigates the low NOx combustion of gaseous fuels by lean premix techniques. Fuel cells are potentially the most efficient converters of stored chemical energy into electric energy. Work at PSI focuses on the development of low temperature fuel cells for transport applications, such as hybrid electric vehicles. A low-cost, high performance solid polymer electrolyte membrane has been developed, which is now used in fuel cell stacks in order to address gas flow, heat and water management issues, which are crucial for a reliable overall systems performance.
Measurements of air pollutant and trace gas fluxes in the atmosphere For an assessment of the ecological consequences of energy use, experimental techniques are required for monitoring the concentrations and transport of atmospheric pollutants produced upon power generation and energy use (including traffic, industry, and domestic use). Large area airborne concentration measurements of ozone, nitrogen oxides, and volatile carbon compounds are supplemented by ground-based optical measurements. These measurements are supplemented by model-based calculations quantifying chemical transformations, such as ozone generation, during the transport. The effects of air pollutants on the vegetation are a crucial factor determining the external costs of energy use. Experimental techniques are developed to assess how forests and crops respond to the complex interplay of weather conditions (temperature, humidity), nutrients (nitrates), air pollutants (ozone) and atmospheric trace gases (increased CO2 concentration due to anthropogenic emissions).
Comprehensive assessment The mentioned analysis of ecologic consequences of energy use is an integral component of a program on the comprehensive assessment of energy systems, which is pursued jointly with research groups within and outside PSI. This program comprises the life cycle analysis of full energy chains, risk and safety aspects of power generation systems, as well as an analysis of the economic consequences of energy technologies and regulations. For example, the marginal cost associated with different CO2 reduction scenarios, as well as possibilities and benefits for a joint international implementation, are analyzed.