The European Commission has been recognized DH technology of essential importance to reach the sustainability. A flexibility in the fuel mix, and possibilities of industrial waste heat utilization, combined heat and power (CHP) production and energy recovery through waste incineration, are only some of the benefits which characterize DH technology.

The aim of this study is to provide an overview of the possible business strategies which would enable for DH to have an important role towards future sustainable energy systems. The study includes a system approach where DH is seen as a part of an integrated system which consists of transport‑, industrial-, and electricity sectors as well.

Converting energy for running the industrial processes from fossil fuels and electricity to DH and delivering excess heat from industrial processes, would make the industry less dependent on fossil fuels and fossil fuel-based electricity, as well as increase energy efficiency and reduce production costs. Reducing the electricity use in the industry sector while at the same time increasing the CHP production in the local DH systems would (1) replace fossil-based electricity production with electricity in biomass- or waste-fueled CHP plants, and reduce the capacity requirements from the national electricity grid (i.e. it would reduce the pressure on the bottle necks in the grid). Furthermore, by operating their central controlled heat pumps and CHP plants depending on the intermittent electricity production variation the DH companies may enable an increased share of intermittent electricity production in the national electricity grid.

The Paris Agreement sets a framework to reach a goal of limiting the increase in global average temperature to well below 2°C above pre-industrial levels. Actions to reduce greenhouse emissions include increasing the share of renewable electricity production and improving energy efficiency. 

However, this implies challenges related to the intermittent nature of wind and solar power. One way to enable an increased share of intermittent electricity production is to increase flexibility on the demand side. A district heating system that includes centrally controlled heat pumps and combined heat and power plants, together with load management of industrial processes, can provide a platform for an increased share of intermittent renewable power generation. 

Previous studies have analysed technical potentials for flexible operations that can increase the share of intermittent renewable electricity production. However, the view of the actors involved has not been analysed. Therefore, the aim of the present study is to analyse the industry’s and the energy sector’s perceptions of the potentials and challenges related to flexible operations.

Actors from industry and energy companies in Sweden were interviewed to appraise and evaluate how they perceive the potentials and challenges regarding sector coupling and flexible operations. Challenges identified are trade-offs between balancing the electricity grid and cost-optimisation at company level, and that the strategy requires a smart control system and targeting regulations. 

The results from the study can guide policymakers when formulating policies that can stimulate marketplaces for flexible operation that will enable an increased share of intermittent renewable electricity production and reduce the risk of power capacity shortages.

The highly varying character of district heating (DH) demand results in low capacity utilization of the DH plants, as well as increased use of fossil fuels during peak demand. The aim of this study is to present an overview and a comprehensive classification of measures intended to manage these load variations. A systematic literature review was conducted based on previously defined search strings as well as inclusion and exclusion criteria. Two scientific databases were used as data sources. Based on 96 detected publications, the measures were categorized as (1) complementing DH production in heat-only boilers (HOBs), or geothermal or booster heat pumps (HPs) (usually controlled by the DH company), (2) thermal energy (TE) storage in storage units or in the network (controlled by the company), and (3) demand side measures, which can be strategic demand increase, direct demand response (DR), or indirect DR. While the company has control over direct DR (e.g., thermal storage in the thermal mass of the buildings), indirect DR is based on communication between the customer and the company, where the customer has complete control. The multi-disciplinary nature of this topic requires an interdisciplinary approach.

Even though the share of renewable energy in the transport sector has increased during the last decade, the sector is still highly dependent on fossil fuels. Consequences are for example emissions of greenhouse gases, particulates, carbon monoxide and nitrogen oxides. This is of great concern for the environment, climate change, and human health. This study reviews scientific publications about sustainable development of the road transport sector, published 2005-2018. The aim of the study is to investigate if there are differences in the measures and strategies presented in the publications depending on the geographical areas studied, and to analyse if there are differences depending on year of publication. The authors analysed to what extent local conditions influence the choice of proposed measures and strategies. A system perspective was applied in order to include measures related to the whole life cycle of the road transport, as well as other sectors, which influence or are influenced by the transport sector. A literature review was performed using the search-engine Web of Science. Results show that important local conditions that may influence the research focus within the area of sustainable development of the road transport sector are for example: energy supply security (e.g. availability of biomass and renewable electricity, as well as access to domestic fossil fuel resources), possibilities for developing infrastructure for biofuel supply and charging of electric vehicles, political priorities and approaches, and traditions.

The aim of this study is to analyse the possibilities of converting production and support processes from electricity and fossil fuels to district heating in 83 manufacturing companies in three different Swedish counties. A tool for heat load analysis called Method for Heat Load Analysis (MeHLA) is used to explore how the conversions would affect the heat load duration curves in local district heating systems. Economic effects and impacts on global emissions of greenhouse gases are studied from a system perspective. The study has been conducted considering two different energy market conditions for the year 2030.

The results show that there is a potential for increasing industrial district heating use in all analysed counties. When comparing all three counties, the greatest potential regarding percentage is found in Jönköping, where the district heating use in the manufacturing companies could increase by nine times (from 5 GWh to 45 GWh annually). The industrial district heating use could increase by two times (from 84 GWh to 168 GWh annually) in Östergötland and by four times (from 14 GWh to 58 GWh annually) in Västra Götaland. The conversion of the industrial production processes to district heating would lead to a district heating demand curve which is less dependent on outdoor temperature. As a result, the utilization period of the combined heat and power plants would be prolonged, which would decrease district heating production costs due to the increased income from the electricity production.

In all analysed counties, the energy costs for the companies decrease after the conversions. Furthermore, the increased electricity production in the combined heat and power plants, and the decreased electricity and fossil fuel use in the industrial sector opens up a possibility for a reduction of global greenhouse gas emissions. The potential for the reduction of global greenhouse gas emissions is highly dependent on the alternative use of biomass and on the type of the marginal electricity producers. When the marginal effects from biomass use are not considered, the greenhouse gas emissions reduction is between 10 thousand tonnes of CO2eq and 58 thousand tonnes of CO2eq per year, depending on the county and the type of marginal electricity production plants. The highest reduction is achieved in Östergötland. However, considering that biomass is a limited resource, the increase of biomass use in the district heating systems may lead to a decrease of biomass use in other energy systems. If this assumption is included in the calculations, the conversion of the industrial processes to district heating still signify a  potential for reduction of greenhouse gas emissions, but this potential is considerable lower.

This paper evaluates the effects on profitability of biofuel production if biofuel producers would sell the waste heat from the production to a local district heating system. All analyses have been performed considering four different technology cases for biofuel production. Two technology cases include ethanol production which is followed by by-production of raw biogas. This biogas can be upgraded and sold as biofuel (the first technology case) or directly used for combined heat and power production (the second technology case). The third and the fourth technology cases are Fischer-Tropsch diesel and dimethyl ether production plants based on biomass gasification. Two different district heating price levels and two different future energy market scenarios were considered. The sensitivity analyses of the discount rate were performed as well.

In the case of energy market conditions, the profitability depends above all on the price ratio between biomass (used as the feedstock for biofuel production) and crude oil (used as the feedstock for fossil diesel and gasoline production). The reason for this is that the gate biofuel prices (the prices on which the biofuel would be sold) were calculated assuming that the final prices at the filling stations are the same as the prices of the replaced fossil fuel. The price ratios between biomass and district heating, and between biomass and electricity, also have an influence on the profitability, since higher district heating and electricity prices lead to higher revenues from the heat/electricity by-produced.

Due to high biofuel (ethanol + biogas) efficiency, the ethanol production plant which produces upgraded biogas has the lowest biofuel production costs. Those costs would be lower than the biofuel gate prices even if the support for transportation fuel produced from renewable energy sources were not included. If the raw biogas that is by-produced would instead be used directly for combined heat and power production, the revenues from the electricity and heat would increase, but at the same time the biofuel efficiency would be lower, which would lead to higher production costs. On the other hand, due to the fact that it has the highest heat efficiency compared to the other technologies, the ethanol production in this plant shows a high sensitivity to the district heating price level, and the economic benefit from introducing such a plant into a district heating system is most obvious. Assuming a low discount rate (6%), the introduction of such a plant into a district heating system would lead to between 28% and 52% (depending on the district heating price level and energy market scenario) lower biofuel production costs. Due to the lower revenues from the heat and electricity co-produced, and higher capital investments compared to the ethanol production plants, Fischer-Tropsch diesel and dimethyl ether productions are shown to be profitable only if high support for transportation fuel produced from renewable energy sources is included.

The results also show that an increase of the discount rate from 6% to 10% does not have a significant influence on the biofuel production costs. Depending on the biofuel production plant, and on the energy market and district heating conditions, when the discount rate increases from 6% to 10%, the biofuel production costs increase within a range from 2.2% to 6.8%.

Biofuel production through polygeneration with heat as one of the by-products implies a possibility for cooperation between transport and district heating sectors by introducing large-scale biofuel production into district heating systems. The cooperation may have effects on both the biofuel production costs and the district heating production costs. This paper is the second part of the study that investigates those effects. The biofuel production costs evaluation, considering heat and electricity as by-products, was performed in the first part of the study. In this second part of the study, an evaluation of how such cooperation would influence the district heating production costs using Stockholm's district heating system as a case study was performed. The plants introduced in the district heating system were chosen depending on the future development of the transport sector. In order to perform sensitivity analyses of different energy market conditions, two energy market scenarios were applied.

Despite the higher revenues from the sale of by-products, due to the capital intense investments required, the introduction of large-scale biofuel production into the district heating system does not guarantee economic benefits. Profitability is highly dependent on the types of biofuel production plants and energy market scenarios. The results show that large-scale biogas and ethanol production may lead to a significant reduction in the district heating production costs in both energy market scenarios, especially if support for transportation fuel produced from renewable energy sources is included. If the total biomass capacity of the biofuel production plants introduced into the district heating system is 900 MW, the district heating production costs would be negative and the whole public transport sector and more than 50% of the private cars in the region could be run on the ethanol and biogas produced. The profitability is shown to be lower if the raw biogas that is by-produced in the biofuel production plants is used for combined and power production instead of being sold as transportation fuel; however, this strategy may still result in profitability if the support for transportation fuel produced from renewable energy sources is included. Investments in Fischer–Tropsch diesel and dimethyl ether production are competitive to the investments in combined and power production only if high support for transportation fuel produced from renewable energy sources is included.

In this study, cooperation between Stockholm's transport and district heating sectors is analysed. The cooperation concerns the integration of biofuel polygeneration production. A MODEST optimisation model framework is used, assuming various energy market and transport sector scenarios for the year 2030. The scenarios with biofuel production and increased biofuel use in the region are compared with reference scenarios where all new plants introduced into the district heating sector are combined heat and power plants, and the share of biofuel used in the transport sector is the same as today. The results show that the cooperation implies an opportunity to reduce fossil fuel consumption in the sectors by between 20% and 65%, depending on energy market conditions and assumed transport sector scenarios. If we consider biomass an unlimited resource, the potential for greenhouse gas emissions reduction is significant. However, considering that biomass is a limited resource, the increase of biomass use in the district heating system may lead to a decrease of biomass use in other energy systems. The potential for reduction of global greenhouse gas emissions is thus highly dependent on the alternative use of biomass. If this alternative is used for co-firing in coal condensing power plants, biomass use in combined heat and power plants would be more desirable than biofuel production through polygeneration. On the other hand, if this alternative is used for traditional biofuel production (without co-production of heat and electricity), the benefits of biofuel production through polygeneration from a greenhouse gas emissions perspective is superior. However, if carbon capture and storage technology is applied on the biofuel polygeneration plants, the introduction of large-scale biofuel production into the district heating system would result in a reduction of global greenhouse gas emissions independent of the assumed alternative use of biomass.