Future District Heating Interactions – Modelling Impacts of Industrial Excess Heat Utilisation and Energy Efficient Buildings

International goals for climate change mitigation plus energy security targets could be met cost-effectively by interactions between different parts of energy systems. The fourth generation of the district heating systems concept was developed as an attempt to accelerate district heating (DH) systems’ interactions with other energy systems. This thesis investigates future interactions of district heating (DH) systems with industries and buildings. This is investigated by developing a methodology and applying it to real cases.Taking a long-term and system-wide perspective, the investigation includes carbon (CO2) and techno-economic impacts of increased energy efficiency in industries and buildings on the DH systems. Real case studies are selected to capture the local conditions of DH systems. Climate policy scenarios are designed as the starting point for the investigations and systematic sensitivity analyses are designed to test the robustness of the case study results. The tool applied is dynamic energy systems optimisation modelling. A regional MARKAL model is applied for DH-industry interactions, whereas a local TIMES model is applied for DH-building interactions. The heating sector and parts of the electricity, transport, industry and building sectors are represented in the optimisation models. \ua0The results show that, through a large heat network allowing for long transmission of industrial excess heat (EH) to DH systems, the DH-industry interaction requires major investment. Such investment is likely to be profitable if the EH replaces DH (which is primarily supplied by costly primary energy sources). From a systems perspective, the investment is less likely to be profitable if other EH sources contribute a large share of the DH base load and if there is an abundance of locally available, low-cost biomass. If built, heat networks help reduce biomass and fossil fuel use and provide a related reduction in CO2 emissions in DH systems. This outcome implies decreased electricity generation from combined heat and power (CHP) plants, in the region studied. In low-energy building (LEB) areas, DH-building interactions (using a heat connection which allows heat to be supplied from a nearby urban area DH system to an LEB area) are cost-effective relative to local (on-site) DH and individual heat supply options. However, changes in energy flows (and CO2 emissions resulting from the nearby urban area DH systems) depend on assumptions about future climate policies, marginal electricity generation and alternative use of biomass, as well as the scale of the urban area DH system

Bioenergy and links to agriculture & LULUCF in a Nordic context

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Large Heat Networks in District Heating Systems

District heating (DH) systems have experienced three generations since the 1880s. In chronological order, high temperature steam and pressurized hot water above and below 100 degrees have been used to carry heat over these three generations. The drive to increase energy efficiency and reduce investment costs of these systems have been the principal incentives for shifting from one generation to the other. The future development of DH systems towards the fourth generation will involve an attempt to recover heat from low-temperature sources (e.g. industrial excess heat (EH)), the use of renewable sources and the integration into smart energy systems. In Sweden, DH currently supplies about 60% of the heat demand. For future DH developments, these systems need to be competitive compared to individual solutions (i.e. heat pumps and boilers) in supplying heat. They could also be incorporated in future sustainable energy systems by integrating renewables and establishing synergies with other energy sectors. There are currently some successful synergies between industry and DH systems but as one step towards the fourth generation of DH, industry-DH synergies could be further developed in order to recover still unused industrial EH. Due to the diversity of Swedish DH systems in terms of local fuel use and heat demand, their choice of heat production technologies is affected. Thus, the environmental and economic impacts of DH systems-industry synergies that allow for industrial EH use in DH systems or the DH use in industrial processes have often been studied in a small geographical scale, limited to the boundaries of local DH systems. However, because it is often transported over relatively short distances, biomass as the main fuel used in DH systems has often turned into a regional market. With increasingly stringent targets for climate change mitigation, biomass use is likely becoming more attractive not only in the heat but also in the power and transport sectors. Since synergies between local DH systems and industry affect the regional market for biomass and, consequently, the power and transport sectors, a regional level combined with an inter-sectoral approach might provide a comprehensive way to identify the impacts of DH-industry synergies.The aims of this thesis are, first, to develop a methodology for assessing an option for future DH development, i.e. a large heat network that would allow for long-distance industrial EH transmission for use in DH systems; and, second, to apply this methodology to assess energy systems, environmental and economic impacts of a large heat network between the cluster of chemical industries in Stenungsund and the DH systems of Gothenburg and Kung\ue4lv in West Sweden Region (V\ue4stra G\uf6taland (VG)). The assessment has been carried out with the help of optimizing energy systems model MARKAL_WS, in which the DH systems in the VG Region are represented individually. In addition, options for transport biofuel production as competitors to regional biomass are included. The thesis is based upon two papers. In the first paper, energy system and CO2 emission impacts of the large heat network have been analyzed at a regional level. The results show that the heat network contributes to a reduction of biomass and fossil fuel use, and to a related reduction of CO2 emissions, in the DH systems. This outcome opens opportunities for the earlier production of transport biofuels but implies decreased electricity generation from combined heat and power (CHP) plants in the Region. In the short-term, total CO2 emissions increase, given an expanded systems view that effects on the DH systems, transport and European electricity system are accounted for, while in the mid-term they decrease.In the second paper, the long-term system cost and marginal cost effects of the large heat network have been assessed. The results show that the heat network is profitable under most assumptions and that the profitability increases with biomass competition and the phase-out of fossil fuel use while it decreases with higher CO2 charge, interest rates and the availability of other EH sources in the vicinity of the DH systems. The marginal cost of DH supply in the Gothenburg and Kung\ue4lv DH systems decreases during most seasons except for the cold seasons

ECONOMICALLY OPTIMAL HEAT SUPPLY TO LOW ENERGY BUILDING AREAS

European Directives and Swedish national goals aim at increasing buildings’ energy efficiency. The construction of low energy building (LEB) areas in Sweden has increasingly attracted attention due to national support. Compared to conventional buildings, LEBs require little space heating during the cold seasons. Still, there are various options for supply of the required heating. Thus, this study aims at comparing the long-term system cost of three heat supply options to a hypothetical LEB area assumed to be located close to an urban area: an “individual” (i.e. separate heat supply), an “on-site” (i.e. local district heating (DH) system) and a “large heat network” (i.e. heat production in a nearby DH system and transmission to the LEB area). A dynamic approach is applied allowing the heat supply system to develop with time, and an energy system model being able to account for the interactions between the building, heat and power sectors, is utilised for the calculations. Two climate policy scenarios are applied to address the uncertainty in future energy prices etc. A systematic sensitivity analysis is designed to investigate the threshold for cost-effectiveness of the large heat network option compared to the other two options. The sensitivity analysis takes into account different combinations of three key parameters: plot ratio of the LEB areas, specification of nearby DH, and distance between LEB area and nearby DH system. The results show, for most of the tested combinations and under both scenarios, that heat supply from the nearby DH system has the lowest system cost if the distance to this system is no more than 2 km, because of the low-cost sources of heat available in the large DH system. A local DH system is more cost-effective than individual heating of buildings even in a LEB area, if it is densely built

Low-energy buildings heat supply–Modelling of energy systems and carbon

Construction of new low-energy buildings (LEB) areas is attracting attention as a climate mitigation measure.Heat can be supplied to buildings in these areas through individual solutions, through a small, on-site heatnetwork, or through a heat connection to a close-by district-heating (DH) system. The choice between theseoptions affects the energy supply systems and their carbon emissions far beyond the LEB area. We compare thelong-term systems impacts of the three heat-supply options through dynamic modelling of the energy systems.The study draws on data collected from a real LEB area in Sweden and addresses scale-dependent impacts ondistrict heating systems. The results show that, generally, the individual and on-site options increase biomassand electricity use, respectively. This, in turn, increases carbon emissions in a broader systems perspective. Thesystems impacts of the large heat network option depend on the scale and supply-technologies of the DH systemclose to the LEB area

System profitability of excess heat utilisation – A case-based modelling analysis

The use of EH (excess heat) in DH (district heating) may contribute to increased sustainability through reduced use of primary energy. In Sweden, while biomass has become the most important DH fuel during the last decades, there is a significant amount of industrial EH that could be utilised in the DH systems if it could be shown to be an economically viable alternative. This study addresses the long-term system profitability of a large heat network between a cluster of chemical industries and two DH systems that enables an increased use of EH. An assessment is carried out by scenario and sensitivity analyses and by applying the optimising energy systems model MARKAL_WS, in which the DH systems of the V\ue4stra G\uf6taland region of Sweden are represented individually. The results show heat network profitability under most assumptions, and that the profitability increases with biomass competition, phase-out of natural gas use and higher CO2 charges, whereas it decreases with the availability of other EH sources in the base load of the DH systems

A comprehensive assessment of cost-optimal heat supply to new low-energy building areas in Sweden

Buildings in Sweden use a large share of energy produced nationally but produce a low share of direct carbon emissions due to high market share of heat pumps and district heating (DH), which uses biomass. Sweden has set stringent energy and climate goals for 2045 prescribing, among other things, reduced energy consumption in buildings. Consequently, new building areas are built based on low-energy building (LEB) standards. These buildings require space heating on cold days and hot water generally. There are four main heat supply options for these areas: (1) individual heat devices (2) decentralized DH, (3) connection to a nearby centralized DH, and (4) prosumers. In this study we developed and applied a dynamic energy system optimization model and designed a systematic analysis to assess cost-optimal heat supply to LEBs in the long-term, while addressing the climate targets. The results showed that low temperature decentralized DHs (LTDDH)s have the lowest cost and individual heat devices have the highest cost of heat supply to LEB areas. The cost-efficiency of LTDDH increases with if prosumers exist in more densely built LEB areas with higher annual heat demand. Additionally, stringent climate policy scenarios can further decrease the cost of LTDDH in LEB areas

Cost-efficiency of urban heating strategies – Modelling scale effects of low-energy building heat supply

There is now a strong demand in Sweden for construction of new low energy buildings (LEB) areas. There are essentially three options for heat supply to these LEB areas: “individual”, “on-site” and “large heat network” supply. The chosen option is of strategic societal interest. Thus, this study aims at comparing the long-term system cost of the three heat supply options. A dynamic modelling approach is applied in a systematic analysis designed to investigate the threshold for the various options' cost-efficiency. The study addresses scale impacts of hypothetical LEB areas and district heating systems. The results show that, generally, the large heat network option has the lowest system cost whereas in most cases the individual option has the highest system cost. Keywords: Low temperature district heating, Fourth generation district heating, TIMES, Energy system modelling, Passive house

Effekter på utsläpp av luftföroreningar från förändrad framtida elbalans i Sverige

I rapporten undersöks hur framtida höga elbehov i flera sektorer (el- och värmeproduktion, bostäder och service, samt industri) kan komma att påverka framtida utsläpp av NOX och små partiklar (PM2,5). Ökad elektrifiering riskerar att fördröja den pågående utsläppsminskningen av NOX till år 2030 men skynda på utsläppsminskningen till år 2050. Effekten på den pågående utsläppsminskningen av PM2,5 riskerar vara fördröjande både år 2030 och 2050

Modelling environmental and energy system impacts of large-scale excess heat utilisation – A regional case study

EH (excess heat) is an important, but yet partially unused, source for DH (district heating). This study analyses energy system and CO2 emission impacts at a regional scale of integration of EH from a large chemical cluster and local DH systems. The assessment is carried out with the optimising energy systems model MARKAL_WS, in which the DH systems in the V\ue4stra G\uf6taland region of Sweden are represented individually. In addition, options for transport biofuel production are included. The results show that the connection contributes to a reduction of biomass and fossil fuel use, and to a related reduction of CO2 emissions, in the DH systems. This opens opportunities for earlier production of transport biofuels but instead electricity generation from combined heat and power plants in the region decreases. In the short term, total CO2 emissions increase if an expanded systems view is applied in which effects on the DH systems, transport system and European electricity system are accounted for, while in the mid-term they decrease. The study is based on a case and due to the diversity of Swedish DH systems in terms of use of fuels and local available resources, a generalisation of the results is not straightforward