Heat pumps are a promising option to decarbonize the industrial sector. However, their performance at a plant-level can be affected by other process changes. In this work, process changes that improve the heat pump's performance have been identified using Process Change Analysis (PCA), where the background pinch point is used as a reference point for appropriate placement. The effects of the process changes on the heat pump's work requirements are studies by introducing exergy to PCA to form the split exergy grand composite curve. This graph shows the work potential of the streams connected to the heat pump and therefore its work targets. The framework is demonstrated in two case studies. In a biodiesel production plant, it allowed to identify technologies that enhance heat pump performance while reducing overall heating requirements. Here, a heat pump transfers 1.9 MW with a COP of 4.2 but incurs a 40 kW penalty for transferring heat above the background process's pinch temperature. Replacing the wet water washer with a membrane separation unit avoided this penalty, while drastically reducing energy requirements from 0.9 MW to 0.3 MW. in a vinyl chloride monomer-purification process, PCA showed how the extraction of heat by the heat pump impacted the formation of the background pinch, from which an implementation strategy was derived that increased the heat pump's plant-level performance by 6.5% with respect to standard implementation.

@en

In view of the energy transition, it is important that engineering students are familiar with the concept of exergy and the added value of exergy analysis compared to energy analysis. Exergy analysis tells the truth about energy efficiency and exergy is directly related to sustainable development. This paper focuses on teaching exergy to students at the Delft University of Technology (TU Delft), but the contents are valuable to other engineering students as well. To encourage the teaching of exergy, the basics of exergy and exergy analysis are presented, as well as examples and ideas for teaching exergy to BSc students that are related to the topics of their BSc programme. It is recommended that the contents of this paper be discussed with many teachers of BSc programmes, especially teachers of BSc programmes that do not yet seem to include the teaching of exergy, and that attention be paid to teaching exergy to MSc students as well.@en

Heat pumps (HPs) which use low temperature (waste) heat and renewable energy sources to provide high temperature heat are widely regarded as a critical technology for reducing carbon dioxide emissions in the industrial sector. The HighLift technology considered here can provide high temperature output heat up to around 200 °C. This article focuses on the Life Cycle Cost Analysis (LCCA) method and its use for the economic evaluation of different industrial-scale heating methods i.e., a Stirling-cycle-based heat pump, a fossil fuel oil-fired boiler (OB), a bio oil-fired boiler (BOB), a natural gas-fired boiler (NGB) and a biogas-fired boiler (BGB). Many input parameters and boundary conditions apply to Sweden, where the considered heat pump is located. Findings from this study suggest that when comparing the life cycle costs of all these technologies Stirling-cycle-based heat pumps give more economic benefits than fossil fuel or biofuel-fired conventional boilers. For a typical 15-year lifespan, its total life cycle cost decreases in following order OB > BOB > NGB > BGB > SC-HP. The study indicates that replacing conventional boilers with a Stirling-cycle-based heat pump, despite an increased initial cost, would still be a cost-effective heating option due to lower operating and maintenance costs.@en

Steam generating heat pumps show great potential for reducing carbon emissions in the industrial sector. However, predicting their performance is challenging as the exergy destruction of e.g., compressors and expansion valves increases with the temperature lift and condenser temperature. With over seventy design improvements mentioned in the literature, selecting the most effective design improvements is crucial. In this study, energy and exergy-based methods were compared in their ability to identify design improvements for a single stage subcritical heat pump to produce steam from hot condensate. The energy-based method suggested the addition of a sequential compressor with an intermediate cooler; however, this design did not improve the heat pump's techno-economic performance. The suggestion of adding either an internal heat exchanger or a flash vessel by exergy-based methods did lead in both cases to improved techno-economic performance. The internal heat exchanger performed best and increased the coefficient of performance from 2.3 to 2.8 and reduced operational costs by 0.8 M€ after 5 years of operation. Additionally, the initial investment decreased by 135 k€, and the total costs of operation decreased from 10.3 M€ to 8.7 M€. These findings show that exergy-based methods are the way forward in identifying effective design improvements for steam generating heat pumps.

@en

The Netherlands is known for its high penetration of natural gas use in households and industry, but the threat of climate change and earthquakes in the province of Groningen, caused by natural gas production, stimulate the search for alternatives, such as hydrogen gas. Various ways of producing and supplying hydrogen have the attention of scientists, companies and policy makers. This study compares the following three ways of green hydrogen production: 1) a photovoltaic system in Africa is used to produce hydrogen from sea water, followed by pipeline transport to Rotterdam, Netherlands, 2) electricity generated by the offshore Borssele 1&2 wind farm in the Netherlands is used for the offshore production of hydrogen from sea water followed by pipeline transport to Rotterdam, or 3) the electricity generated by this offshore wind farm is transmitted to Rotterdam where it is used for onshore production of hydrogen from sea water. The sustainability of the three systems is assessed from a life cycle point of view. The environmental LCA resulted in ReCiPe 2016 endpoint indicators and the midpoint indicators GWP, land use and water consumption. The exergetic sustainability assessment applied the Total Cumulative Exergy Loss (TCExL) method. The preferred system according to the results of the environmental LCA and the exergetic sustainability assessment is the wind energy system including offshore hydrogen production. The results are not unanimous as to which system is the second-best. The three systems need to be investigated in more detail before firm conclusions can be drawn. It is recommended that attention also be paid to the economic and social pillars of sustainability, and to the exergetic sustainability of technological systems in general, as exergetic assessment results are independent of changing and subjective models, weighting factors and other variables.@en

The use of Stirling-cycle-based heat pumps in high-temperature applications and waste heat recovery at an industrial scale is of increasing interest due to the promising role in producing thermal energy with zero CO2 emissions. This paper analyzes one such technology as developed by Olvondo Technology and installed at the pharmaceutical company AstraZeneca in Sweden. In this application, the heat pump used roughly equal amounts of waste heat and electricity and generated 500 kW of steam at 10 bar. To develop and widen the use of a high-performance high-temperature heat pump that is both economically and environmentally viable and attractive, various analysis tools such as exergy analysis and life cycle assessment (LCA) can be combined. The total cumulative exergy loss (TCExL) method used in this study determines total exergy losses caused throughout the life cycle of the heat pump. Moreover, an LCA study using SimaPro was conducted, which provides insight into the different emissions and the overall environmental footprint resulting from the construction, operation (for example, 1, 8, and 15 years), and decommissioning phases of the heat pump. The combined results were compared with those of a fossil fuel oil boiler (OB), a bio-oil boiler (BOB), a natural gas-fired boiler (NGB), and a biogas boiler (BGB).@en

The intermittent nature of renewable energy sources like solar and wind energy stimulates the use of centralised and decentralised energy storage systems. The sustainability of lead acid, lithium-ion and concentration gradient flow batteries, compressed air and pumped hydro energy storage (PHES) systems is investigated by conducting a multi-dimensional life cycle assessment. The environmental, economic and exergetic sustainability are assessed by calculating ReCiPe 2016 indicators, the present worth ratio and the Total Cumulative Exergy Loss, respectively. The multi-dimensional sustainability assessment did not lead to one preferred system. The PHES causes the lowest damage to human health, ecosystem diversity and resource availability and results in the lowest global warming potential. The concentration gradient flow battery system named BBS is preferred from an economic viewpoint, while the PHES is second-best. The lithium-ion battery system causes the lowest exergy losses, followed by the PHES. It is recommended to pay attention to the exergetic sustainability of technological systems as exergy losses are independent of environmental models, weighting factors, market prices, subsidies etc. More research into the specifications of the energy storage systems is needed to be able to draw firm conclusions with regard to which system is preferred.

@en

Power generation from biomass is mentioned as a means to make our society more sustainable as it decreases greenhouse gas emissions of fossil origin and reduces the dependency on finite energy carriers, such as coal, oil and natural gas. When assessing the sustainability of power generation from biomass, it is important to consider the supply chain of the used biofuel by conducting a life cycle assessment of the system. Besides regular sustainability assessments, such as the calculation of the environmental sustainability, attention should be paid to exergy losses, i.e. the loss of 'energy quality', caused by the system as a whole, because every process and activity is accompanied with the loss of exergy and because the amount of exergy on earth can only be replenished by capturing new exergy from solar and tidal energy. This research compares the use of livestock manure and verge grass for power generation by assessing the systems from an environmental as well as an exergetic life cycle point of view. The assessed systems are the following: combustion of bioethanol from the fermentation of verge grass, combustion of substitute natural gas from anaerobic digestion of cow and pig manure and combustion of substitute natural gas from supercritical water gasification of cow and pig manure. The environmental sustainability is assessed by calculating ReCiPe endpoint indicators and the exergetic sustainability is assessed by applying the relatively new Total Cumulative Exergy Loss (TCExL) method. The TCExL method considers all exergy losses caused by a technological system during its life cycle, i.e. the internal exergy loss caused by the conversion of materials and energy, the abatement of emissions and the exergy loss related to land use. In addition to comparing the three systems as well as both assessment methods, the influence of taking into account the system's by-products as 'avoided products' and via 'allocation' on the assessment results is investigated. The bioethanol system appears more sustainable from an environmental sustainability point of view, while the bioethanol and supercritical water gasification systems are preferred from an exergetic sustainability point of view. The indicator of the environmental sustainability assessment is highly influenced by the way of taking into account by-products, while the exergetic sustainability indicator is not.@en

Energy conversion systems have assumed a crucial role in current society. The threat of climate change, fossil fuel depletion and the growing world energy demand ask for a more sustainable way of electricity production, eg, by using renewable energy sources, by improving the conversion efficiency and/or by controlling power plant emissions. Despite the relationship between exergy and sustainability stated in literature, exergy losses are usually not considered when comparing systems and energy sources for power generation. The exergetic sustainability assessment method named Total Cumulative Exergy Loss (TCExL) has been used to assess several systems for electricity production, ie, a coal-fired power plant, a coal-fired power plant including carbon capture and storage, a biomass-fired power plant, an offshore wind farm and a photovoltaic park. The results of the TCExL method have been compared with an environmental sustainability indicator, ie, the overall ReCiPe endpoint indicator and the economic indicator named Present Worth Ratio. The offshore wind farm is the best system from the exergetic and environmental point of view. The photovoltaic park is the system with the second-best scores. However, from the economic viewpoint including subsidy by the Dutch government, the photovoltaic park performs better than the wind farm system and the system that performs best is the biomass-fired power plant. Without subsidy, only the coal-fired power plant without carbon capture and storage is profitable. The exergetic sustainability scores of the coal-fired and biomass-fired power plants are similar, but from the environmental sustainability viewpoint, the biomass-fired power plant performs better than both coal-fired power plants. As the results of environmental and economic sustainability assessments strongly depend on models, weighting factors, subsidy, market prices, etc, while the results of the exergetic sustainability assessment do not, it is recommended that the exergetic sustainability be taken into account when assessing the sustainability of power generation and other technological systems.

@en

It is difficult to decide which power generation system is the most sustainable when environmental, economic and social sustainability aspects are taken into account. Problems with conventional environmental sustainability assessment methods are that no consensus exists about the applied models and weighting factors and that exergy losses are not considered. Economic sustainability assessment methods do not lead to results that are independent of time because they are influenced by market developments, while social sustainability assessment methods suffer from the availability and qualitative or semi-quantitative nature of data. Existing exergy analysis methods do not take into account all exergy losses and/or are extended with factors or equations that are not commonly accepted. The new Total Cumulative Exergy Loss (TCExL) method is based on fundamental thermodynamic equations and takes into account all exergy losses caused by a technological system during its life cycle, i.e. internal exergy losses, exergy losses caused by emission abatement and exergy losses related to land use. The development of the TCExL method is presented as well as the application of this method and environmental, economic and social sustainability assessment methods to two case studies: power generation in combination with LNG evaporation and Fossil versus renewable energy sources for power generation. According to the results of the assessments, large differences exist between the environmental sustainability assessment and TCExL methods in the sense that different parts of the systems contribute most to their overall scores. It is concluded from the case studies that involving the TCExL method in choices between power generation systems with the same energy sources has no consequences, i.e. it does not result in a different ranking of the systems, but can lead to the choice of a system that has a lower economic sustainability if the assessed systems use different energy sources. However, it must be noted that the economic sustainability changes over time, while the results of the TCExL method do not.

@en

The selection of power generation systems is important when striving for a more sustainable society. However, the results of environmental, economic and social sustainability assessments are subject to new insights into the calculation methods and to changing needs, economic conditions and societal preferences. Researchers active in the field of exergy and sustainability claim that exergy losses and sustainability are related. The Total Cumulative Exergy Loss method and the exergy replacement costs of minerals are used to assess and compare power generation systems that make use of fossil and renewable energy carriers. These power generation systems are the following: an ultrasupercritical coal power plant, a power plant that co-fires coal and biomass, a wind farm, and a combined cycle power plant that uses bioethanol originating from the fermentation of verge grass. Furthermore, environmental, economic and social sustainability assessment methods are applied to assess the four power generation systems as well. On the basis of the results of the assessments, it is concluded that the wind farm system is preferred from the environmental, social and exergetic sustainability points of view, but not from the economic sustainability viewpoint. The advantage of the exergetic sustainability assessment method is that its results are not influenced by choices like whether verge grass should be considered a waste product or not. The influence of the exergy replacement costs on the results of the exergetic assessment is small, because less than 5 per cent of the exergy input of the systems during construction, operation and commission is of mineral origin. When looking at the infrastructural part of the systems only, the influence of the exergy replacement costs is larger because about 25 to 40 per cent of the exergy input is of mineral origin. @en

The human genome is diploid, that is each of its chromosomes comes in two copies. This requires to phase the single nucleotide polymorphisms (SNPs), that is, to assign them to the two copies, beyond just detecting them. The resulting haplotypes, lists of SNPs belonging to each copy, are crucial for downstream analyses in population genetics. Currently, statistical approaches, which avoid making use of direct read information, constitute the state-of-the-art. Haplotype assembly, which addresses phasing directly from sequencing reads, suffers from the fact that sequencing reads of the current generation are too short to serve the purposes of genome-wide phasing.
Future sequencing technologies, however, bear the promise to generate reads of lengths and error rates that allow to bridge all SNP positions in the genome at sufficient amounts of SNPs per read. Existing haplotype assembly approaches, however, profit precisely, in terms of computational complexity, from the limited length of current-generation reads, because their runtime is usually exponential in the number of SNPs per sequencing read. This implies that such approaches will not be able to exploit the benefits of long enough, future-generation reads.
Here, we suggest WhatsHap, a novel dynamic programming approach to haplotype assembly. It is the first approach that yields provably optimal solutions to the weighted minimum error correction (wMEC) problem in runtime linear in the number of SNPs per sequencing read, making it suitable for future-generation reads. WhatsHap is a fixed parameter tractable (FPT) approach with coverage as the parameter. We demonstrate that WhatsHap can handle datasets of coverage up to 20x, processing chromosomes on standard workstations in only 1-2 hours. Our simulation study shows that the quality of haplotypes assembled by WhatsHap significantly improves with increasing read length, both in terms of genome coverage as well as in terms of switch errors. The switch error rates we achieve in our simulations are superior to those obtained by state-of-the-art statistical phasers.
@en