Find opportunities to decarbonise with pinch technology Pinch technology and exergy analysis can steer energy efficiency and process decarbonisation decisions
David Hart Energy Intelligent Solutions
T he need to decarbonise is clear: to satisfy stakeholder demands associated with climate change. For many organisations this translates into significant disruption to established operations, higher operating costs and significant capital expenditure. The speed with which organisations need to act varies depending on local regulations and demands, and on the local prices and carbon intensities of energy sources, but in all cases there is a need to quickly and robustly develop clear pathways for the future. Many companies have stretching targets for carbon reduction which they have committed to achieving. Pinch technology and conventional thermodynamic and energy performance assessments need to be adjusted to cover situations where, for example, electrification is more appropriate than using fuels to generate heat; in other words, where work (or electricity) is less valuable than heat. This is counter to solutions generally applied in the past where carbon reduction was not a consideration. Figure 1 shows trends in energy prices in the UK for the last decade. The UK is characterised by high cost electricity and lower cost gas, pushing companies to use gas in favour of power, to generate power from gas using gas engines/turbines with heat recovery and to avoid increased electricity use, for example avoiding using heat pumps. A higher relative price for electricity, or work, is consistent with the conventional view of thermodynamics that work has a higher value than heat and that there needs to be a focus on avoiding exergy losses. The trends in UK carbon emissions intensities
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Figure 1 Trends in UK energy prices
for typical utilities are shown in Figure 2 . The decarbonisation of electricity is pushing organisations towards electrification rather than using fossil fuels, and away from combined heat and power and towards the use of heat pumps – the exact opposite of the actions to reduce operating costs. This is driven by the increased percentage of power derived from low carbon sources, resulting in lower carbon emissions from grid electricity. Reducing carbon emissions is inconsistent with reducing costs and with the traditional thermodynamic approach. It is interesting to note the changes in the carbon intensities over the last five years and the associated changes in acceptable technologies: combined heat and power (CHP) has switched from a low carbon solution to a carbon increasing solution in just a few years, but remains one of the few opportunities to significantly reduce utility operating costs (power costs) in the UK. Heat pumps have become the first choice for
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