Thu / 03.10. @ 11:30
Solving the energy trilemma of the low-carbon, affordable and secure supply of energy will require a complete rethinking of future energy systems. However, to make things yet more challenging, there are strong and complex interactions and interdependencies between the provision of energy (E), food (F) and water systems (W), known as the EFW nexus. Any action in energy, water or food has impacts on the other two. Maximising the sustainable provision of energy requires that energy systems should strive to satisfy human needs in an economically viable, environmentally benign and socially acceptable way . Added to the complexity of the interactions and interdependencies are future uncertainties regarding governmental policies and new developments in energy technology. Solutions should be local to geographic regions. Given these major uncertainties, there is a need for flexible local solutions to allow for the local supply and demand of energy, and future changes in supply and demand, and technology developments.
The energy intensive process industries account for around 70% of total industrial energy consumption  and 45% of global greenhouse gas emissions . For example, the chemical and petrochemical industries use 10% of global energy consumption and generate 7% of greenhouse gas emissions. In the energy intensive process industries as a whole, energy consumption and greenhouse gas emissions are currently mainly from the combustion of fossil fuels to produce process heat and power. There is also currently gross inefficiency in the way this energy is used, with around 40% wasted as low-temperature heat (<150° C), mainly to cooling towers, air cooling and furnace stack losses .
Primary energy in the energy intensive process industries is currently overwhelmingly dominated by the use of fossil fuels, mainly natural gas and oil, but also coal in some countries. If these industries are to be transformed from huge energy consumers and greenhouse gas emitters, a switch to renewables and waste-to-energy systems is required. However, the energy intensive process industries also have some special energy requirements that bring additional difficulties for such a switch. Firstly, the heating requirement is often far higher than the power demand. Secondly, heat is often required at very high temperatures. This means that in the future if there is a wholesale switch to renewable power, then the use of renewable power has limited potential to substitute fossil fuels directly, because of the large heat demand currently satisfied by steam heating and the high-temperature heat demand currently satisfied by firing fossil fuels in fired heaters. Thus, an appropriate mix of different renewables would be required to satisfy differing heat and power demands. Heat can be provided by biomass, biogas or waste-to-energy for high-temperature process heating and the generation of steam and power at least to some extent by wind and solar photovoltaics. However, because of the intermittency of supply of renewable power, some storage will be required. Such storage is also beneficial for smoothing variations in demand and to compensate for variable power tariffs. In addition to storing electricity, storage can be used for heating or cooling. Currently, energy storage within the energy intensive process industries is hardly practised at all.
To solve this problem requires rethinking the way in which industrial energy is supplied, combining the most appropriate sources of energy. In principle, the supply of energy can also be distributed closer to the end-users. Energy hubs supplying distributed energy need to exploit an appropriate combination of different energy sources, including renewables, waste-to-energy systems, the symbiotic exploitation of waste heat and energy storage to match local power-to-heat ratio demand and heating requirements both in terms of duty and temperature in a more efficient and environmentally sustainable way than current approaches.
To address these challenges, requires a new design framework that adopts a holistic and life cycle approach for the conceptual design of integrated industrial energy systems, utilising a range of energy sources, including in principle fossil and renewable energy, from both distributed and centralised sources, and including the use of strategic energy storage. To address the variability of supply and demand, temporal variations must also be incorporated in the design framework to allow for variability in energy supply, demand and cost tariffs. The design framework must also include life cycle considerations, accounting for economic costs, environmental and social impacts and constraints in the EWF nexus. In principle, this will permit the design of self-sufficient ultra-low-carbon solutions.