| 1. |
- Beiron, Johanna, 1992, et al.
(författare)
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An assessment of the flexibility of combined heat and power plants in power systems with high shares of intermittent power sources
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- There is an urgent need to reduce anthropogenic CO2 emissions from the power sector as a climate change mitigating strategy. Thus, the share of renewable energy sources in power systems, for example wind power, is increasing. However, the variability in wind power generation poses a challenge to conventional thermal power plants, as well as yielding volatile electricity prices. Once in place, wind power with low operating cost will replace higher-cost electricity generation units in the merit order, while during low-wind periods the need for thermal plants remains. Traditionally designed for stable base load, thermal power plants might thus face a future with new demands for flexible operation to stay competitive. Combined heat and power (CHP) plants are thermal power plants that produce electricity and district heating simultaneously and, depending on plant type and fuel, they have different possibilities to vary the ratio between power and heat production. However, technical constraints place limitations on flexibility, including ramp rates and efficiency. The interconnection between the power and heat markets provides additional opportunities for load variation management. With the comparably slower dynamics of the heat market, and the possibility to store thermal energy, prospects of adapting to new and profitable operating strategies that can aid the balancing of the power system arise. This study focuses on how CHP plants can provide flexibility in a scenario with fluctuating power demand and associated volatility in electricity prices. Plant and market dynamics are analyzed to estimate the need for flexibility, and what is required of CHP units in terms of operation to meet these requirements. A CHP plant is modelled in detail with a boiler, steam cycle and its link to the district heating system, both under steady state and transient conditions, using the softwares Ebsilon and Dymola, respectively. The models are validated against operational data from a Swedish CHP plant. Transient responses to load ramps are characterized, as well as the flexibility in power-to-heat ratio, and their effects on efficiency.
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| 2. |
- Biermann, Max, 1989, et al.
(författare)
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Efficient utilization of industrial excess heat for carbon capture and district heating
- 2020
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Carbon capture and storage (CCS) from fossil and biogenic (BECCS) emission sources is necessary to limit global warming to well below 2°C. The EU as well as Swedish national agencies emphasize the importance of CCS for emission intensive industries. However, the cost of implementing CCS is currently still higher than the cost of emitting CO2 via the EU ETS, for example. To incentivize rapid deployment of CCS, the concept of partial capture has been suggested, i.e. capturing only a fraction of the site emissions to reduce capture cost. Several studies have found that the utilization of excess heat from industrial processes could significantly reduce the capture cost as the heat required (~120°C) may be available in significant quantities. However, available excess heat will not be sufficient to power full capture at most industrial sites. In Sweden, many industries utilize all or part of their excess heat in heat recovery units or in combined heat and power (CHP) plants to produce electricity and deliver heat to municipal district heating (MDH) systems. A broad implementation of CCS will, thus, effect the availability of excess heat for industrial heat and power generation. The future product portfolio of industrial processes with excess heat export and CHP plants can therefore be expected to include not only heat and power production, but also climate services (CCS/BECCS) and grid services (frequency regulation due to intermittent renewables). The aim of this work is to assess partial capture at sites that have access to low-value excess heat to power the capture process, whilst considering competition from using the excess heat for MDH delivery. The work is based on process modelling and cost estimation of CO2 capture processes using amine absorption for two illustrative case studies, a refinery and a steel mill, which both currently use excess heat for MDH. The main focus is on investigating how seasonal variations in the availability of excess heat as well as the demand of district heating impact cost-efficient design and operation of partial capture at industrial sites. A challenge when utilizing excess heat in connection to a process connected to a district heating system is that the heat source which can be used to power part of the capture process will exhibit seasonal availability, and thus may inflict extra cost for the CCS plant not running at full load, and therefore may counteract the economic motivation for partial capture. To prevent this, heat integration between CCS and municipal district heating is investigated, for example by utilizing heat from the CO2 compression so that low-pressure steam is released from MDH to provide heat to capture CO2 whilst maintaining MDH supply. The design of the amine absorption capture process will have to handle significant load changes and still maintain high separation efficiency within hydrodynamic boundaries of the absorber and stripper columns. The cost of such operation will depend on the solvent circulation flows, the number of absorber columns (including packing and liquid collectors/distributors) and capacity of solvent buffer tanks for storing unused solvent during the winter season. Assuming that a constant amount of CO2 is avoided, the avoidance cost of CCS based on excess heat with seasonal heat load variations is compared to the avoidance cost of CCS based on the use of external fuel to achieve a constant heat load to the reboiler.
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| 3. |
- Sköldberg, Håkan, et al.
(författare)
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BIO-CCS I FJÄRRVÄRMESEKTORN – SYNTES
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Den svenska fjärrvärmesektorn har stor potential att bidra med negativa koldioxidutsläpp genom bio-CCS, minst 10 Mton per år. Den största osäkerheten beträffande möjligheterna för bio-CCS gäller marknads förutsättningarna. Uppvärmningsbranschen har en vision om att år 2045 utgöra en kolsänka. Ett sätt att åstadkomma detta är genom att avskilja och lagra koldioxidutsläpp med biogent ursprung. Ett antal fjärrvärmeföretag har redan olika långt gångna planer på att satsa på bio-CCS. De har sett ett värde i att samarbeta kring hur detta kan åstadkommas. Ett led i detta är projektet Bio-CCS i fjärrvärmesektorn som består av ett gediget underlag baserat på forskning kring olika aspekter av frågan samt en strategi baserad på det underlaget. I denna rapport redovisas en syntes av detta forskningsarbete. Projektet visar att fjärrvärmesektorn har stor teoretisk potential att bidra med negativa koldioxidutsläpp, minst 10 Mton per år. I huvudsak är avskiljning, transport och lagring av koldioxid beprövad teknik även om tillämpningen i detta fall är ny. Även om bio-CCS är förknippad med energianvändning så bidrar tekniken sett ur ett systemperspektiv med stor nytta för att minska koldioxid[1]utsläppen. Bio-CCS är en relativt dyr teknik och det är angeläget att utnyttja samverkan och kluster för att exempelvis skapa ökad kostnadseffektivitet i transport och mellanlagring. Tillgång till lagringsplatser är en förutsättning för framgång och flera alternativ bedöms bli tillgängliga. Det kan dock uppstå konkurrens om tillgången till lagringsplatserna. De regelmässiga förutsättningarna för bio-CCS i Sverige har förbättrats avsevärt de senaste dryga decenniet. Flera regelmässiga hinder kvarstår dock. En del utgör mindre barriärer, andra är av mer betydande karaktär. Den största osäkerheten beträffande möjligheterna för bio-CCS gäller ekonomin. Flera potentiella finansieringsmetoder har studerats, både stöd, regleringar och frivilligmarknader. Det finns fortfarande oklarheter kring syftet med planerade stöd och det framtida ägandet av de negativa utsläppen. Det genomförda projektet har skapat ett forum för kunskapsuppbyggnad, erfarenhetsutbyte och nätverkande, vilket de deltagande företagen bedömt vara mycket värdefullt.
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