There has never been so much research conducted in energy efficiency and alternatives to carbon
At current prices for fossil fuels, fuels from concentrated solar energy aqnd other technologies are not competitive. However, alternative technologies will be an economically viable option if the cost of fossil fuels also includes the external costs of incineration and the reduction of fossil fuels.
Thermolysis of water
Examples of manufacturing processes which can exploit solar high-temperature energy include cement and metals manufacturing and recycling heavy metal waste. These processes need heat of up to 2000°C. Concentrated solar heat can therefore potentially save huge amounts of fossil fuels.
Current global energy consumption could be supplied by solar energy systems, at 20% conversion efficiency, covering 0.1% of the land. Solar radiation on the Earth’s surface is about 1-3 kW/m2 on average. It makes sense to maximise the use of solar energy available in the range ± 30° from the equator, where solar intensity is over 3 kW/m2 for many more hours in a year. To do this, it is better to convert the energy into a chemical storage form, rather than electricity. Some of the infrastructure for such a system already exists in the petroleum industry – oil and gas, as well as coal, are after all chemical stores of solar energy from millennia ago. Oil tankers could just as easily transport fuel generated in desert regions through power-to-fuel solar thermogeneration.
At high temperatures above 2500 K and depending on the pressure, water splits into hydrogen and oxygen.
H2O → H2 + ½O2
Um das Trennungsproblem, wobei ein Explosionsgefahr besteht mit der Trennung des Wasserstoffs vom Sauerstoff bei hohen Temperaturen, werden zweistufige Wasserspaltungs-Zyklen eingeführt, die auf sogenannten Metalloxid-Redox-Systemen basieren.
1. Solarthermal (endothermic) dissasociation of metal oxides at high temperatures (> 2300K):
MxOy → xM + (y/2)O2
2. Hydrolysis (exothermic) of metal products at moderate temperatures (< 900 K), through which molecular hydrogen and corresponding metal oxides are formed:
xM + yH2O → MxOy + yH2
With such reduction-oxidation systems, efficiencies of more than 30% can be achieved,
When the solar radiation is concentrated very much and the heat generated by the cooling of the products can be recovered.
The use of a combined electrolysis and chemical synthesis process based on CO2 from the air to create renewable biofuel that is carbon emission neutral.
Electricity + water → H2 → synthesis of CO2 → Fuel chemical components.
The carbon in CO2 can be used for higher energy-containing products, such as the synthesis of methane.
Researchers at the Rapperswil University IET Institute for Energy Technology, are running national and international projects to improve catalytic synthesis techniques. These either use cold water, or a cycle with heat management through a steam generator to high-temperature electrolysis to methanisation of CO2.
Technologies involved: SOEC Solid Oxide Electrolyser Cell, alcaline electrolysis und catalytic methanisation.
See also European Union: Programme Horizon 2020, Project Pentagon.
Thermodynamics – Laws
“Thermo-dynamics is the subject of the relation of heat to forces acting between contiguous parts of bodies, and the relation of heat to electrical agency” (Lord Kelvin). The four laws of thermodynamics were derived from the work of, among others, Sadi Carnot, Émile Clapeyron, Julius Mayer, Hermann Hess, und Rudolf Clausius. They explain heat exchange, entropy, and how substances and machines behave under energy transformation.
The four Laws of Thermodynamics:
0. (Zeroth) If two systems are each in thermal equilibrium with a third, they are also in thermal equilibrium with each other.
1. The internal energy of an isolated system is constant. The law of conservation of energy is a consequence, and states that energy can be transformed from one form to another, but cannot be created or destroyed.
2. Heat cannot spontaneously flow from a colder location to a hotter location. Rudolf Clausius: There is no change in state, the only result of which is the transmission of heat from a body of a lower temperature to a higher temperature body. Entropy is a measure of the loss of order (distribution of energy) and tends to increase with time. This leads to the irreversibility of reactions.
3. As a system approaches absolute zero (0 K or −273.15 °C), all processes cease and the entropy of the system approaches a minimum value. Entropy can not be destroyed. However, entropy may arise in the system. Energy degradation results from irreversible processes.
Intensive quantities: temperature T, pressure ρ, concentration n, chemical potential μ
Extensive quantities: internal energy U, entropy S, volume V and particle number N