In line with the Swedish target of carbon neutrality by 2045, the municipality of Växjö in Kronoberg County has set its own target to be carbon neutral in 2030. Currently, the Municipality's partially decentralized energy system relies heavily on interconnected electricity supply from the national grid, and fuels imports from other parts of Sweden. Under this circumstance, several concerns arise, including: in which ways future demand changes induce supply changes, and whether a future carbon-neutral energy system will be less costly in a sustained-electricity supply condition. In this study, techno-economic evaluations are conducted for different carbon-neutral scenarios for Växjö’s future energy system in 2030 and 2050, using an hour-by-hour dynamic energy simulation tool of EnergyPLAN. Projections for the future energy demands for Växjö were developed and modeled, based on the development strategies and on the national sustainable future scenarios in Sweden. Results for the Växjö’s carbon-neutral scenarios showed that the current energy system is sufficient to satisfy future heat demand. However, fulfilling demands of electricity for all sectors and fuels for transport and industry is a challenge. In the short term and at increased energy demand and price, being carbon neutral is technically viable without major changes in energy supply technologies. However, in the long term, investment for intermittent renewable energy resources, together with carbon capture and storage is considered to be viable financially. Therefore, planning for a carbon-neutral Växjö based on local investments showed to be a feasible strategy.

A large potential for energy savings can be found in building envelopes of the existing Swedish dwelling stock. This study analyzes the final energy savings and cost implications of energy efficiency measures for an existing multi-apartment building in Sweden. Energy efficiency improvements consisting of high-performance windows as well as doors, and additional insulation to attic floor and exterior walls were modelled to the building’s thermal envelope. Dynamic energy balance simulations were performed to determine the final energy savings of the improvements. The cost-effectiveness of the improvements were then analyzed considering the net present value of the energy cost savings and the investment costs of the improvement measures. The results showed that additional insulation to the attic floor is the only cost-effective measure for the building under the existing operating conditions. The other improvement measures give high final energy savings but are not cost effective due to their high investment costs.

A wider deployment of nearly zero energy buildings (NZEBs) is expected to contribute to the transition to a decarbonized and energy-efficient building sector in Europe. This study proposed an integrated energy-economic analysis to exemplify the feasibility of NZEB renovation in temperate climate. A parametric analysis was performed to identify technical building system configurations that give minimum share of renewable energy systems contributing to NZEB level. Final energy savings, global costs and cost-effectiveness of renovating a building to NZEB level are analysed, considering active and passive energy efficiency measures (EEMs). The active EEMs included efficient water taps and heat recovery ventilation, and the passive EEMs encompassed insulations to roof, exterior walls and ground floor, and improvements of windows and doors. The building had initial final energy use of 133 kWh/m2 year for space heating, domestic hot water production (DHW) and facility electricity. The results show that NZEB level is achieved with active and passive EEMs, without renewable energy systems for scenarios with low discount rates and high future energy price escalations. The annual final energy use for space heating, DHW and facility electricity is reduced cost-effectively by 37-54%. Furthermore, increasing size of PV-system enhanced cost-effectiveness by lowering total global costs.

A considerable share of the existing buildings in Europe has low energy performance and are expected to last at least for the next 50 years. The operation of these buildings causes high atmospheric greenhouse gases emissions, besides low thermal comfort for occupants. In Sweden, most of the existing buildings are residential, consisting of multi- and single-family houses. Large final energy savings can be achieved by integrating energy efficient measures (EEMs) to the thermal envelopes of these buildings. However, it is often a challenge to achieve a considerable energy savings and realize cost effectiveness simultaneously. This study investigates the effect of carbon taxes implementation on the cost effectiveness of EEMs applied to an existing multi-apartment building in southern Sweden. It explores the implications of different additional insulation thicknesses for exterior walls and roof, and high-performance windows and doors, for the final energy use and carbon dioxide (CO2) emissions of the building. The final energy savings of the EEMs are estimated through dynamic energy balance simulations and the CO2 emissions are calculated considering the full energy chains. The cost effectiveness of the EEMs are analyzed with and without carbon abatement costs considering the investment costs and associated net present value of costs savings of the EEMs. The results show that replacing the existing windows give the highest final energy savings, reducing the building’s space heating demand by 23 %. The cost optimal analysis without carbon abatement costs shows that all the analyzed thicknesses of roof insulation and high-performance windows are cost effective. Considering the carbon abatement costs altered the cost effectiveness of the EEMs, with exterior walls as well as ground floor insulations and door replacement becoming cost effective for certain thicknesses and U-values, respectively.

The European Union's Directive on energy performance of buildings emphasizes the need to take cost-effectiveness into account when measures are implemented for improved building energy efficiency. In this study, we investigate cost-effective energy renovation measures for a district heated building under different contexts, including varied locations, energy supply systems and economic scenarios. We determine the final and primary energy savings of cost-effective energy renovation packages for the building in the different contexts. The measures analysed include: improved insulation for attic floor, basement walls, and exterior walls; improved windows and doors; resource-efficient taps; heat recovery of exhaust ventilation air; energy-efficient household appliances and lighting. We consider three existing Swedish energy supply systems of varying district heat production scale and tariffs, and also plausible renewable-based energy supply systems. Our analysis calculates the final energy savings of the measures including the cost-effective renovation packages on hourly basis and links these to the different energy supply systems. The cost-effectiveness analysis is based on a double-stage optimization method, considering total and marginal investment costs of renovation measures as well as associated net present values of total and marginal cost savings. The results show that significant final and primary energy savings can be achieved when energy renovation measures are implemented for the building in the different contexts. This study shows that heat demand in existing Swedish building could be about halved while electricity use may be reduced considerably with cost-effective energy renovation measures. The economic viability of the renovation measures is sensitive to the economic regimes especially discount rates and energy price increase.

This study analysed the final and primary energy savings as well as cost-effectiveness of centralised and semi-centralised heat recovery air handling units (AHUs) configurations for existing and efficient variants of a district heated multi-dwelling building. The AHUs have counter-flow plate or rotary heat exchangers, and their performances for the building variants are analysed considering different economic scenarios and frost conditions. Very few studies have explored the techno-economic implications of such AHU configurations in the context of building retrofitting. The final energy savings is calculated on hourly basis using dynamic simulation modelling approach and is linked to the heat supply to calculate the associated primary energy savings. The cost-effectiveness is calculated considering investment costs as well as net present values of energy cost savings when the AHUs are applied. The results show that the primary energy savings and cost-effectiveness for heat recovery AHUs vary considerably for different contexts. The semi-centralised AHUs with rotary heat exchanger seem slightly more cost-effective among the analysed heat recovery configurations. Frost conditions and defrosting need have significant impact on the primary energy and economic performance of the AHUs.

Low-carbon buildings and construction products can play a key role in creating a low-carbon society. Cross-laminated timber (CLT) is proposed as a prime example of innovative building products, revolutionising the use of timber in multi-storey construction. Therefore, an understanding of the synergy between structural engineering design solutions and climate impact of CLT is essential. In this study, the carbon footprint of a CLT multi-storey building is analysed in a life cycle perspective and strategies to optimise this are explored through a synergy approach, which integrates knowledge from optimised CLT utilisation, connections in CLT assemblies, risk management in building service-life and life cycle analysis. The study is based on emerging results in a multi-disciplinary research project to improve the competitiveness of CLT-based building systems through optimised structural engineering design and reduced climate impact. The impacts associated with material production, construction, service-life and end-of-life stages are analysed using a process-based life cycle analysis approach. The consequences of CLT panels and connection configurations are explored in the production and construction stages, the implications of plausible replacement scenarios are analysed during the service-life stage, and in the end-of-life stage the impacts of connection configuration for post-use material recovery and carbon footprint are analysed. The analyses show that a reduction of up to 43% in the life cycle carbon footprint can be achieved when employing the synergy approach. This study demonstrates the significance of the synergy between structural engineering design solutions and carbon footprint in CLT buildings.

Ahead of heat exchanger network (HEN) design, setting an optimal pinch temperature difference for pinch analysis depends vitally on the capital cost target. Conventional methods based on the spaghetti (SPA) structure ignoring matching optimization might result in calculated cost targets of large deviations. This work evolved the SPA structure via four stages by shifting energy towards low-cost matching. The fourth structure evolved from the SPA structure (ESPA-IV structure) with the lowest-cost matching after loops elimination forms the base to establish the ESPA method. It is validated by numerical experiment and applied to a case reported in literature, meanwhile comparisons are always made to the SPA method. The numerical experiment proves that the ESPA method can obtain capital cost targets with higher accuracy than the SPA method. The target deviations (often within ±5%) given by the ESPA method are much lower than those (well above 10%) derived by the SPA method. In the case study, the given HEN is further optimized as hinted by ESPA method results. Of two target methods, the cost target indicated by ESPA method is closer to the optimum capital cost newly derived after optimization. The high accuracy of the ESPA method is further verified.

In this study we explore the effects of end-use energy efficiency measures on different district heat production systems with combined heat and power (CHP) plants for base load production and heat-only boilers for peak and medium load productions. We model four minimum cost district heat production systems based on four environmental taxation scenarios, plus a reference district heat system used in Östersund, Sweden. We analyze the primary energy use and the cost of district heat production for each system. We then analyze the primary energy implications of end-use energy efficiency measures applied to a case-study apartment building, taking into account the reduced district heat demand, reduced cogenerated electricity and increased electricity use due to ventilation heat recovery. We find that district heat production cost in optimally-designed production systems is not sensitive to environmental taxation. The primary energy savings of end-use energy efficiency measures depend on the characteristics of the district heat production system and the type of end-use energy efficiency measures. Energy efficiency measures that reduce more of peak load than base load production give higher primary energy savings, because the primary energy efficiency is higher for CHP plants than for boilers. This study shows the importance of analyzing both the demand and supply sides as well as their interaction in order to minimize the primary energy use of district heated buildings.

We estimate the climate effects of directing forest management in Sweden towards increased carbon storage in forests with more land set-aside for protection, or towards increased forest production for the substitution of carbon-intensive materials and fossil fuels, relative to a reference case of current forest management. We develop various scenarios of forest management and biomass use to estimate the carbon balances of the forest systems, including ecological and technological components, and their impacts on the climate in terms of radiative forcing. The scenario with increased set-aside area and the current level of forest residue harvest resulted in lower cumulative carbon emissions compared to the reference case for the first 90 years, but then showed higher emissions as reduced forest harvest led to higher carbon emissions from energy and material systems. For the reference case of current forest management, increased harvest of forest residues gave increased climate benefits. The most climatically beneficial alternative, expressed as reduced cumulative radiative forcing, in both the short and long terms is a strategy aimed at high forest production, high residue recovery rate, and high efficiency utilization of harvested biomass. Active forest management with high harvest levels and efficient forest product utilization will provide more climate benefit, compared to reducing harvest and storing more carbon in the forest.

Forest residues can be left at the harvest site to gradually decompose, or can be collected for energy purposes. This study analyzes the primary energy and climate impacts of bioenergy systems where forest residues are collected and used for electricity, heat and transportation, compared to fossil-based energy systems where fossil fuels provide the same services while forest residues are left on site to decompose. Time profiles are elaborated of primary energy use and carbon dioxide emissions from various energy applications fulfilled by bioenergy or fossil energy systems. Different biological decay functions are considered based on process-based modeling and inventory data across various climate zones. For all scenarios, the changes in cumulative radiative forcing (CRF) are calculated over a 300-year period, to evaluate the short- and long-term contributions of forest residue to climate change mitigation. A life cycle perspective along the full energy chains is used to evaluate the overall effectiveness of each system. The results show largest primary energy and climate benefits when forest residues are collected and used efficiently for energy services. Using biomass to substitute fossil coal provides greater climate change mitigation benefits than substituting oil or fossil gas. Some bioenergy substitutions result in positive CRF, i.e. increased global warming, during an initial period. This occurs for relatively inefficient bioenergy conversion pathways to substitute less carbon intensive fossil fuels, e.g. biomotor fuel used to replace diesel. More beneficial bioenergy substitutions, such as efficiently replacing coal, result immediately in reduced CRF. Biomass decay rates and transportation distance have less influence on climate benefits.

Different pathways and technologies can be used to convert woody biomass to transport services, but the biomass use and climate implications vary strongly between the alternatives. This study focuses on primary energy use and climate change effects of using bioenergy for transportation in the context of a renewable-based energy system. Integrated pathways to improve the energy efficiency of power and transportation sectors and integrated intermittent renewable energy are considered. The results show that the bioenergy pathway that produces biomotor fuels to replace fossil fuels leads to high primary energy use and instantaneous biogenic CO2 emission per km of driving distance, thus increasing global warming during the first 40e50 years, compared to fossil alternatives. The electric vehicle pathway using bioelectricity from combined heat and power plants leads to immediate global cooling and much greater climate benefits in the long run compared to biomotor fuels. Climate change effects of light-duty vehicles could be strongly reduced by changes in technology together with system integration that links the transport sector to the electricity and heating sectors. The use of biomass should be considered in the context of the overall integrated energy system, and in relation to the development of energy conversion technologies between different sectors.

The operation of a district heating system depends on the heat load demand, which varies throughout the year. In this paper, we analyze the coproduction of district heat and electricity or biomotor fuels. We demonstrate how three different taxation scenarios and two crude oil price levels influence the selection of production units to minimize the district heat production cost and calculate the resulting primary energy use. Our analysis is based on the annual measured heat load of a district heating system. The minimum-cost district heat production system comprises different production units that meet the district heat demand and simultaneously minimize the district heat production cost. First, we optimize the cost of a district heat production system based on the cogeneration of electricity and heat with and without biomass integrated gasification combined-cycle technology. We considered cogenerated electricity as a byproduct with the value of that produced by a condensing power plant. Next, we integrate and optimize different biomotor fuel production units into the district heat production system by considering biomotor fuels as byproducts that can substitute for fossil motor fuels. We demonstrate that in district heating systems, the strengthening of environmental taxation reduces the dependence on fossil fuels. However, increases in environmental taxation and the crude oil price do not necessarily influence the production cost of district heat as long as biomass price is not driven by policy measures. Biomotor fuel production in a district heating system is typically not cost-efficient. The biomotor fuels produced from the district heating system have to compete with those from standalone biomotor fuel plants and also with its fossil-based counterparts. This is also true for high oil prices. A carbon tax on fossil CO₂ emissions based on social cost damage will increase the competitiveness of biomass-based combined heat and power plants, especially for BIGCC technology with its high electricity-to-heat ratio.

Woody biomass is an important renewable energy resource that can be used directly or indirectly in the electricity, heat and transport sectors. Different technologies and conversion pathways can be used to convert woody biomass to supply different types of energy services. The primary energy and climate implications of bioenergy systems depend on which conversion technologies and pathways are used to produce the energy services, as well as how the services would have been supplied without the bioenergy system. Here, we focus on bioenergy for transportation in the context of a total renewable-based energy system. We contrast two different pathways: (i) biomotor fuel production in stand-alone plants and (ii) bioelectricity production in standalone plants and district heating systems with CHP plants and heat storage capacity for electric and plug-in hybrid vehicles. We quantify the primary energy use and the instantaneous biogenic CO₂ of the two alternatives, per km of driving distance. We consider both commercially available technologies and emerging technologies for biomass-based conversion systems. Furthermore, for the two alternatives we discuss potential benefits of integration between the electricity, heating and transport sectors, to enable a better use of infrastructure. The results show that primary energy use and instantaneous biogenic CO₂ emission vary strongly between the alternatives. The primary energy efficiency is much higher and gives less instantaneous biogenic CO₂ emission for electric and plug-in hybrid vehicles compared to vehicles using biomotor fuels. Furthermore, the potential integration benefits between the electricity, heating and transport sectors are much larger due to the integration potential of heat storage capacity in DHS and battery storage capacity in electric and plug-in hybrid vehicles, as well as an improved overall integration capacity between the sectors. This study suggests that use of biomass should be considered in the context of the overall energy system, and in relation to the development of energy conversion technologies and integration potential between different energy sectors, to find primary energy efficient alternatives giving climate benefits in both a short- and long-term perspective.

Forests can help mitigate climate change in different ways, such as by storing carbon in forest ecosystems, and by producing a renewable supply of material and energy products. We analyse the climate implications of different scenarios for forestry, bioenergy and wood construction. We consider three main forestry scenarios for Kronoberg County in Sweden, over a 201-year period. The Business-as-usual scenario mirrors today’s forestry while in the Production scenario the forest productivity is increased by 40% through more intensive forestry. In the Set-aside scenario 50% of forest land is set-aside for conservation. The Production scenario results in less net carbondioxide emissions and cumulative radiative forcing compared to the other scenarios, after an initial period of 30–35 years during which the Set-aside scenario has less emissions. In the end of the analysed period, the Production scenario yields strong emission reductions, about ten times greater than the initial reduction in the Set-aside scenario. Also, the Set-aside scenario has higher emissions than Business-as-usual after about 80 years. Increasing the harvest level of slash and stumps results in climate benefits, due to replacement of more fossil fuel. Greatest emission reduction is achieved when biomass replaces coal, and when modular timber buildings are used. In the long run, active forestry with high harvest and efficient utilisation of biomass for replacement of carbon-intensive non-wood products and fuels provides significant climate mitigation, in contrast to setting aside forest land to store more carbon in the forest and reduce the harvest of biomass.

This study explores the potential and impact of electricity cogeneration using Organic Rankine Cycle (ORC) integrated with small-scale biomass boilers within district heating systems. An analysis is conducted on a 3 MW_th biomass-fired district heating plant in southern Sweden. Process monitoring data, collected over a one-year period from the plant, serves as the basis for simulation and analysis. The study examines operational changes and fuel usage at a local level, together with an extension to a regional scale considering both short-term and long-term energy system implications. The results show that integrating a 200 kW_e ORC unit with the existing boiler having a flue gas condenser is cos-optimal and could cogenerate approximately 1.1 GWh electricity annually, with a levelized electricity cost of €64.4 per MWh. This is equivalent to a system power-to-heat ratio of 7.5%. From a broader energy system perspective, this efficient integration could potentially reduce CO₂ emissions by 234-454 tons per year when the saved energy locally is used to replace fossil fuels in the energy system, depending on how biomass is utilized and what type of fossil fuels are replaced. Increasing installed capacity of ORC unit to maximize electricity co-generation could result in a carbon abatement cost ranging from €204 to €79 per ton CO₂. This cost fluctuates depending on the installed capacity, operation of the ORC units, and prevailing electricity prices. The study highlights the trade-off between financial gains and CO₂ emission reductions, underscoring the complex decision-making involved in energy system optimization.

A municipal housing company located in the south of Sweden has energy renovatedseveral buildings with a total of 380 apartments to meet today’s energy standards. Several energyefficient technologies and solutions were implemented and the energy consumption for thesebuildings were lowered by 50%. One of the buildings functions as a demonstration building forinnovative solutions such as low temperature district heating, waste water heat recovery, andsolar photovoltaic and thermal (PVT) panels. The solar PVT panels are cooled down with themain purpose to increase the electricity production. The cooling medium for these panels iscirculated through two bedrock boreholes to dissipate the collected heat. The heat from theboreholes is then used for an electric heat pump to produce heat to send to the local districtheating company. The electricity produced is primarily used in the building. The objective ofthis paper is to assess the electricity production from real-life outdoor Photovoltaic-thermal(PVT) plant. The plant was installed on the roof top of an energy renovated multi-familyapartment building located in the south of Sweden. The cooling of the panels were turned on andoff to assess if the electricity production would increase or not. The electricity production didnot increase when the cooling was applied. The temperature measuring equipment which wasinstalled at the wrong position and was supposed to measure the temperature at the back of thePVT is needed to compare the efficiency of the PVT plant and draw further conclusions.

We analyse the climate implications of producing electricity in large-scale conversion plants using coal, forest slash and municipal solid waste with and without carbon capture and storage (CCS). We calculate the primary energy, carbon dioxide (CO₂) and methane (CH₄) emission profiles, and the cumulative radiative forcing (CRF) of different systems that produce the same amount of electricity. We find that using slash or waste for electricity production instead of coal somewhat increases the instantaneous CO₂ emission from the power plant, but avoids significant subsequent emissions from decaying slash in forests or waste in landfills. For slash used instead of coal, we find robust near- and long-term reductions in total emissions and CRF. Climate effects of using waste instead of coal are more ambiguous: CRF is reduced when CCS is used, but without CCS there is little or no climate benefits of using waste directly for energy, assuming that landfill gas is recovered and used for electricity production. The application of CCS requires more fuel, but strongly reduces the CO₂ emissions. The use of slash or waste together with CCS results in negative net emissions and CRF, i.e. global cooling.

An appropriate energy solution for buildings depends on the scale of demand and the availability of the surrounding technical infrastructure. Building energy demand can be altered by the application of various energy efficiency measures whereas the performance of the energy supply system can be changed by the involvement of various technologies. As a result, optimal energy supply options could depend on various parameters that depend on specific contexts. In this study, different options to supply energy to apartment buildings of different energy efficiency levels in Sweden are investigated. Different renewable-based alternatives to produce heat and electricity based on various state-of-the-art technologies are considered. The optimizations are based on the hourly variation throughout the year of energy demand and of different energy supply systems that change with the ambient conditions such as temperature and solar radiation. The results prove that optimal options for a building depend on its scale of energy demand and on the availability of technologies in the market. Also, there is a tradeoff between monetary costs and primary energy use in supplying energy to apartment buildings. This study shows that it is essential to consider the interaction between energy demand and supply to estimate the costs and primary energy use for energy supply alternatives. A heating system with an electric heat pump shows to be primary energy efficient option whereas that with a wood pellet boiler is a more cost efficient once. However, an energy supply option based on a combined heat and power unit using fuel cell technology could potentially be the most cost- and primary energy efficient option for buildings with low energy demand.

District heat production systems (DHSs) are normally designed to meet the heat demand of customers at a minimum cost whilst fulfilling local and national regulations. Various factors influence the choice of district heat production units in a minimum-cost system. In this thesis, the performance of DHSs of different types were analyzed under a range of environmental and social cost scenarios. The scenarios include No tax using the bare cost of fuels without any taxes or fees, Swedish tax using Swedish taxes and fees on fuels, Social cost-550ppm using a carbon damage cost of US$30/t CO₂, Social cost-BAU using a carbon damage cost of US$85/t CO₂, and Renewable-based without using fossil fuels for energy purposes. DHSs were analyzed under varying conditions of scale, potential to co/poly-generate district heat with other products, and integration of new technologies currently being developed. The influence of end-use energy efficiency measures in district-heated buildings on DHSs was also analyzed.

The cost optimal composition of a DHS depends on several factors including the scale, the load factor of the heat demand, the technologies used in the DHS, as well as the environmental and social costs. When environmental and social costs are considered, the co-generation of electricity is more cost-efficient than other options, except for small scale systems, for which heat-only production is more cost-efficient. Also, in a minimum-cost DHS, district heat production cost is about the same for all the environmental and social cost scenarios except for the No tax scenario. The district heat production cost of a small-scale DHS under the No tax scenario is lower than that of the same scale system under the other scenarios. However, a large-scale DHS under the No tax scenario gives higher district heat production cost than the same scale system under the other scenarios. The changed environmental and social costs vary the types and amount of fuel use as well as the value of co-generated products such as electricity, which consequently balances the district heat production cost.

Renewable-based DHS using biomass is economically viable if environmental and social costs of using fossil fuels are taken into account. A fully biomass-based DHS can be as primary energy-efficient as other DHSs analyzed. Typically, biomass-based co-generation of district heat and electricity combined with stand-alone production of biomotor fuels is more cost- and primary energy-efficient than the co-generation of district heat and biomotor fuels combined with stand-alone production of electricity. The integration of non-fuel renewable technologies such as solar water heating can further reduce the use of biomass in a cost-efficient way for small-scale DHSs in combination with high fuel costs.

The characteristics of a DHS influence the effectiveness of end-use energy efficiency measures in district heated buildings. Although end-use energy efficiency measures change the final energy use, the composition and operation of the supply system determine the amount and types of fuel savings. Supply systems with different composition and operation give varying primary energy savings per unit of reduced end-use energy from an energy efficiency measure. The primary energy savings due to end-use heat saving measures in buildings is much higher for heat-only production units than for co/poly-generation units, because heat savings in co/poly-generation systems also reduce the potential production of co-products. Therefore, the analysis of both demand and supply sides of district heating systems as well as their interaction is crucial for the evaluation of the consequences of end-use energy efficiency measures in district-heated buildings. Actually, energy efficiency measures in district-heated buildings typically increase the overall heat load factor for a DHS which reduces the operating cost per unit of produced district heat in existing system and the total cost when existing district heat production units have to be renewed or changed. The connection of new energy-efficient buildings that balances the energy efficiency improvement in existing district-heated buildings appears to be an optimal option for a DHS.

In this study we estimate the final and primary energy savings for different energy efficiency measures in a multi-apartment building when heated by small-, medium- or large-scale district-heat production systems (DHSs). The small-scale system is based on heat-only boilers, whereas the other two also include cogeneration of district heat and electricity. In the systems with cogeneration units, a change in building's heat demand may influence cogenerated electricity and hence the overall power system. For the building analyzed, the estimated annual total final heat and electricity savings were 136 (54%) and 30 MWh (52%), respectively, giving total annual primary energy savings of 177–289 MWh. This varies as the ratio of primary and final heat savings depends on the type of energy efficiency measure and the energy supply. For the same heat savings measure, a system with a heat-only boiler gave the highest primary energy savings, whereas a system based mostly on cogeneration of district heat and electricity in combination with averaged-efficiency standalone power plants gave the lowest primary energy savings. When the energy supply is based on energy-efficient renewable-based system, the differences in primary energy savings between large- and small-scale DHSs are minor for the same energy efficiency measure.

The effectiveness of energy-efficiency measures in a district-heated building can be complex, as it depends on how energy is produced and used. In this study, a primary energy analysis was conducted based on a case study of a Swedish apartment building that is connected to a district heat production system while considering different climate change mitigation policy instruments including carbon taxes corresponding to Social cost-Business-as-usual or Social cost-550 ppm scenarios. The potential to reduce final heat and electricity demands by different energy-efficiency measures was analyzed for the building used in the case study. The impacts of reducing final energy from the different energy-efficiency measures and the climate change policy instruments on primary energy use and cost of district heat production were investigated using a systems analysis approach. We discussed the importance of analyzing the demand and supply sides and their interaction to minimize primary energy use in district-heated buildings. We showed that climate change mitigation policy instruments have a minimal effect on heat production costs for optimally designed district heat production. The primary energy savings for the energy-efficiency measures depend partly on the characteristics of the district heat production system, which is influenced by the policy instruments.

The effects of heat and electricity saving measures in district-heated buildings can be complex because these depend not only on how energy is used on the demand side but also on how energy is provided from the supply side. In this study, we analyze the effects of heat and electricity saving measures in multistory concrete-framed and wood-framed versions of an existing district-heated building and examine the impacts of the reduced energy demand on different district heat (DH) production configurations. The energy saving measures considered are for domestic hot water reduction, building thermal envelope improvement, ventilation heat recovery (VHR), and household electricity savings. Our analysis is based on a measured heat load profile of an existing DH production system in Växjö, Sweden. Based on the measured heat load profile, we model three minimum-cost DH production system using plausible environmental and socio-political scenarios. Then, we investigate the primary energy implications of the energy saving measures applied to the two versions of the existing building, taking into account the changed DH demand, changed cogenerated electricity, and changed electricity use due to heat and electricity saving measures. Our results show that the difference between the final and primary energy savings of the concrete-framed and wood-framed versions of the case-study building is minor. The primary energy efficiency of the energy saving measures depends on the type of measure and on the composition of the DH production system. Of the various energy saving measures explored, electricity savings give the highest primary energy savings for the building versions. In contrast to the other heat savings measures, VHR gives lower primary energy savings as it also increases electricity demand. Primary energy savings for the building versions are lower where the minimum-cost DH production system includes cogeneration unit compared to where the minimum-cost DH production system comprises heat-only boilers. The primary energy savings are mainly from peak and medium-load boilers even though these production units cover a small share of the total DH production. This study shows that it is essential to consider the interaction between end-use energy saving measures and supply systems for district-heated buildings, to estimate the primary energy efficiency of energy saving measures.

There is great potential to build new energy-efficient building blocks in combination with efficient energy supply systems. Such a development will contribute to achieve national energy and climate goals as well as the overall aim for a sustainable development. Here, we analyze final and primary energy use for heating a new residential area by using district-heating. The area, located in Växjö, in south Sweden has potentially varied land exploitation levels, energy performance of buildings and district heat supply/return temperatures. The results show that the district heating demand will be reduced by about 52-56% if buildings in the area meet the Swedish passive house criteria instead of the Swedish building code. The exploitation levels of construction in the area strongly influence the total heating demands. A dense instead of a low exploitation will increase the area’s heating demand more than four times. But, the heat demand density of the residential area has quite a small impact on the total heat losses of the distribution network in contrast to changed supply and return temperatures. The distribution heat losses could be reduced by up to 50% with lower supply/return temperatures. However, a reduction of district heat supply/return temperatures to 50/20^oC increases electricity use for boosting hot water temperature to avoid the risk of legionella bacteria. This causes a shift from district heat production to electricity production and increases the primary energy use. The results of this study can be used for further considerations of costs and benefits of energy supply options for new residential areas.

This study investigates the cost and primary energy use to heat an existing multi-apartment building in Sweden, before and after deep energy efficiency renovation, with different types of renewable-based systems. District heating systems of different scales as well as local heat production based on bioelectric boilers, ground-source bioelectric heat pumps and wood pellet boilers with or without solar heating are considered. The annual energy demand of the building, calculated hour by hour, with and without energy efficiency improvements, are matched against the renewable-based heat supply options by techno-economic modeling to minimize cost for each considered heat supply option. The results show that the availability of heating technologies at the building site and the scale of the building's heat demand influence the cost and the primary energy efficiency of the heating options. District heat from large-scale systems is cost efficient for the building without energy-efficiency improvement, whereas electric heat pumps and wood pellet boilers are more cost efficient when implementing energy-efficiency improvement. However, the cost difference is small between these alternatives and sensitive to the size of building. Large-scale district heating with cogeneration of power is most primary energy efficient while heat pumps and medium-scale district heating are nearly as efficient.

Biomass is a key resource in a society based on renewable energy, but is a limited resource and the use of biomass in one sector will influence its availability for other sectors. The global energy system is heavily dependent on fossil fuels, and the climate impacts of CO2 occur regardless of the source of emissions. As a result, the climatic effects of biomass use in an energy system depend largely on which biomass feedstock and bioenergy pathway is being used, and what type of fossil fuel pathway is being replaced. In this study, we evaluate the CO2 emissions and climate effects of woody biomass and fossil fuel use. We analyse the potential production of electricity, heat or transport distance when using one kWh of woody biomass and fossil energy system designed to provide the same service to society as the most energy efficient bioenergy systems. The fuel cycle inputs are included in the analyses and are based on different state-of-the art as well as emerging technologies for energy conversion. We quantify the primary energy use and annual CO2 emission of different bioenergy and fossil alternatives. We then calculate the cumulative CO2 emission and climate effects in terms of cumulative radiative forcing for the fossil and bioenergy systems. The results show that primary energy use, CO2 emission, and cumulative radiative forcing vary strongly between the studied alternatives. The use of bioelectricity and electric vehicles instead of biomotor fuel-based vehicles gives about twice the transport distance per unit of consumed woody biomass. Integrated energy systems that supply a package of energy services including electricity, heat and transport distance reduce the primary energy use and increase the climate benefits of woody biomass. The replacement of coal for heat and electricity production by the here studied woody biomass gives large climate benefits immediately.

The co- or polygeneration benefits of energy products from a system vary and depends on several factors including how each individual product is otherwise produced and used. In a Nordic renewable based energy system, district heating system using woody biomass could be used for the production of several products and for the integration of electricity, heat and transportation sectors. Energy-efficient systems for the production of different wood based energy services, including efficient end-use system, will reduce the need for woody biomass that could be used in other sectors with less other renewable alternatives including aviation, shipping and material production. However, the scale and the annual variation of heat demands for single district heating systems are key factors that influence co- or polygeneration benefits of such systems. In this study, we analyse district heating systems with annual heat demands between 100 to 1000 GWh. Several technical configurations of co- or polygeneration of heat, electricity and/or biomotor fuels are analyzed, considering different standalone production options, woody biomass fuel prices and integration costs of intermittent energy resources. The development of several state-of-the-art technologies shows that there are co- or polygeneration benefits in district heating systems. System configuration varies with the scales of district heat production as does the use of biomass to generate the same amount of products and both depend on the context of the overall energy system. Electric-based solution for transportation as well as electric-based option for small-scale district heating systems together with cogeneration of heat and electricity in larger district heating system reduce the use of biomass and help to integrate wind power in the overall energy system. Further studies are needed to understand how deep energy-renovation of buildings may influence the configuration of co- or polygeneration system in district heating systems and the potential saving of woody biomass.

Efficient district heat production systems (DHS) can contribute to achieving environmental targets and energy security for countries that have demands for space and water heating. The optimal options for a DHS vary with the environmental and social-political contexts and the scale of district heat production, which further depends on the size of the community served and the local climatic conditions. In this study, we design a small-scale, minimum-cost DHS that produces approximately 100 GWh_heat per year and estimate the yearly production cost and primary energy use of this system. We consider conventional technologies, such as heat-only boilers, electric heat pumps and combined heat and power (CHP) units, as well as emerging technologies, such as biomass-based organic Rankine cycle (BORC) and solar water heating (SWH). We explore how different environmental and social-political situations influence the design of a minimum-cost DHS and consider both proven and potential technologies for small-scale applications. Our calculations are based on the real heat load duration curve for a town in southern Sweden. We find that the district heat production cost increases and that the potential for cogeneration decreases with smaller district heat production systems. Although the selection of technologies for a minimum-cost DHS depends on environmental and social-political contexts, fewer technical options are suitable for small-scale systems. Emerging technologies such as CHP-BORC and SWH improve the efficiency of primary energy use for heat production, but these technologies are more costly than conventional heat-only boilers. However, systems with combined technologies are less sensitive to fluctuations in fuel prices, specifically the SWH system, compared to technologies based on conventional fuels. Furthermore, increased market penetration of SWH will reduce the investment costs of such systems and, along with expected fuel price increases, using SWH may be cost-efficient in DHSs.

The choice of a heat supply option in new residential areas depends on various factors including available local energy resources and the scale and density of the heat demand in the areas. Here, we study costs and primary energy use of using district heat (DH) and ground-source electric heat pump (EHP) for heating a residential area being developed. We consider different architecture layouts and exploitations of the area along with different building energy efficiency standards which give different heat demand densities and profiles for this residential area. The analysis shows that for existing fuel-based energy supply systems, using DH is more primary energy efficient than using EHP to supply heat to the new residential area. However, if the future production of marginal electricity is based on state-of-the art technologies utilizing renewable energy resources, using EHP can be more primary energy efficient than using DH. The initial investment costs are much lower for options using DH than for options using ground-source EHP for the different exploitation alternatives. Also, the marginal heat cost for suppling DH to the residential area, excluding the sunk capital costs, is significantly lower than the heat cost for supplying heat with ground-source EHPs. The potential use of local ground-source heat linked to the exploitation level of residential area and energy performance of the buildings should be further analyzed in comparison to the use of other types of heat sources such as ambient air or ventilation air.

Efficient biomass-based district heat production systems (DHS) can contribute to achieving the social targets of environmental and energy security for countries with demand for space and water heating. In this study, we evaluate the costs of CO₂ emission reduction from biomass-based district heating systems in comparison with fossil-based ones under different scales of district heat production, and we relate this cost to estimated damage costs of CO₂ emission. Our calculations are based on a real heat load duration curve for a city in southern Sweden. The value of cogenerated electricity is assumed to be equal to that produced in minimum-cost standalone condensing power plants. The difference of the production cost and CO₂ emission between fossil- and biomass-based systems is used to calculate the cost of CO₂ emission reduction. We consider four different sizes of DHSs, from 50 to 300 GWh_heat per year, to investigate how the CO₂ emission reduction costs varies with the scale of DHS. We found that the district heat production cost for a minimum-cost DHS depends on scales of district heating systems and that the cost effectiveness between biomass- and fossil-based systems varies for different scales. The costs of CO₂ emission reduction vary from €7.7 to €9.4 per ton of CO_2e depending on the size of DHS. This cost is generally lower than estimated damage costs of CO₂ emission.

The primary energy savings depend on both the final energy savings and the energy efficiency of the supply system. In this study, we evaluate primary energy savings of different energy efficiency measures in a multistory district-heated building in Sweden. We consider various locations of the building with different district heat production systems (DHS) of different scales, technical charac-teristics and heat-load profiles. We show that the primary energy savings of the energy efficiency measures vary with the type of measure and with the type of energy supply systems. The energy efficiency measures give large final energy savings but their primary energy savings vary signifi-cantly. Of the energy efficiency measures, the measure that gives electricity savings but increase the use of district heat is the most primary energy efficient in relation to the final energy savings. Heat savings in buildings connected to small-scale DHS using heat-only boilers is more primary energy efficient than that in buildings connected to medium- and large- scale DHS using combined heat and power units. Evaluation of energy efficiency measures for district-heated buildings re-quires a systems perspective where the final energy savings in buildings are matched to the actu-al energy supply systems.

Woody biomass can be used in different ways to contribute to sustainable development. In this paper, we analyze biomass-based production of district heat, electricity, pellets and motor fuels. We calculate production cost and biomass use of products from standalone production and from different district heat production options, including only heat production and various co/polygeneration options. We optimize the different district heat production systems considering the value of co/polygenerated products, other than district heat, as equal to those produced in minimum-cost standalone plants. Also, we investigate how the scale of district heating systems influences the minimum-cost composition of production units and district heat production costs. We find that co/polygenerated district heat is more cost and fuel efficient than that from heat-only production. Also, coproduction of electricity is more efficient than of motor fuels except for dimethyl-ether production in large district heat production systems. However, the cost difference is minor between coproduction of dimethyl-ether or electricity in such systems. Integrated biopellet production increases the production of electricity or motor fuel and reduces the production cost. District heat production cost depends on fuel price, however, its dependence is reduced if district heat production system is cost-minimized and based on co/polygenerated units. Also, the optimal composition and cost of district heat production depend on the scale of the system. The demand for biopellets may limit the potential integrated production of such a product. (C) 2012 Elsevier Ltd. All rights reserved.

District heat systems can contribute to the achievement of social and environmental targets and energy security. District heat production systems (DHSs) vary in size depending on heat demand, which is influenced by several factors such as local climatic conditions and the sizes of the communities they serve. In this study, we analyzed options for minimum-cost DHSs of different sizes under different environmental and social cost scenarios. We calculated the production cost and primary energy use of district heat for minimum-cost options by considering a value of cogenerated electricity equivalent to the value of electricity produced in minimum-cost standalone condensing power plants. We varied the size of DHSs from 100 to 1800 GWh_heat per year to investigate how size influences the minimum-cost compositions of production units and district heat production costs. We determined that the optimal composition and cost of district heat production is dependent on the size of the system, the overall load factor of heat demand and the technologies considered for both DHSs and reference power plants. In general, cogenerated district heat is more energy-efficient than district heat from heat-only production and also more cost-efficient, except for small DHSs, for which cogenerated district heat is more costly than heat-only production. The cost and primary energy use of district heat production is dependent on environmental and social cost scenarios; however, this dependence is reduced if a DHS is cost-minimized and based on cogenerated units.

Operating capacity of district heat production depends on heat load demand which varies throughout the year. Large capital-extensive production capacity is used briefly for peak-load production while for off-peak periods only capital-intensive base-load is still used. For base-load production, cogeneration of district heat and electricity is often a primary-energy and cost efficient system. In this paper we analyse polygeneration of district heat, electricity and biomotor fuels. We show how different environmental taxation scenarios and changes in crude oil price influence the selection of district heat production units. Our analysis is based on an annual measured district-heat load. We calculate the production costs of district heat and total primary energy use for different polygeneration concepts. Costs are calculated under three environmental taxation scenarios and three crude oil price cases. First, we optimise the cost of a district heat production system based on cogeneration of electricity and heat. We consider cogenerated electricity as a byproduct with value as produced in a reference condensing power plant based on least cost options among different condensing power technologies. Next, we optimize and integrate different biomotor fuel production units into the district heating system considering biomotor fuels as byproducts which are fossil-motor fuel substitutes. We then relate the production cost of district heat and biomotor fuels to evaluate the elasticity between them. We show that the polygeneration improves the primary energy efficiency and reduce the production costs of the generated products. Also, environmental taxation and crude oil price have marginal influences to the produced district heat.

We analyze the possibilities to produce district heat, electricity and/or biomotor fuels in renewable-based energy systems considering district heating systems with annual heat demands between 110 and 1000 GWh. Several technical configurations to co/polygenerate district heat, electricity and/or biomotor fuels are cost optimized in the context of different standalone production options, woody biomass fuel prices and integrating costs of intermittent energy resources. The cost optimum configuration varies with the scale of the district heat production, as does the use of biomass to generate the same amount of product, and both depend on the context of the overall energy system. There are several state-of-the-art technologies that offer significant co/polygeneration benefits within district heating systems. An electric-based solution for transportation as well as an electric-based option for small-scale district heating systems are cost efficient and will reduce the use of biomass and help to integrate wind electricity into the overall energy system. For larger district heating systems, cogeneration of heat and electricity, and also in combination with electric heat pumps for a high biomass price, are cost efficient solutions. Further studies are needed, for example to understand how the deep energy renovation of buildings may influence the configuration of co-/polygeneration systems in district heating systems and potential savings of woody biomass.

In this study, we explored cost-optimal renewable-based district heat production systems and potential to integrate solar heating in such systems under different contexts. We investigated under which conditions a solar heating system become cost-efficient to integrate in district heat production systems and the consequences of this integration. We considered a small-scale district heat production system in the south of Sweden where district-heat production cost is higher and hence it is more cost efficient to integrate solar heating in such district heat production systems. The cost-efficiency of integrating solar heating in a minimum-cost renewable-based district heat production system depends on future fuel prices and investment costs of solar heating systems. In any case, integrating solar heating will help to reduce the use of other primary energy resources as biomass.

In multi-apartment buildings, changes in energy demand may influence cost-optimal heat supply options. District heat based on combined heat and power production has proved to be cost- and primary energy-efficient option for heating purposes in the residential sector. However, for customers with a low heat demand, local heat supply options may be more cost-efficient than district heat supply options. In this study, we investigated cost-optimal options to supply heat to a multi-apartment building in Växjö city, Sweden. We considered biomass-based alternatives for district heating and local heating based on wood pellet boiler and ground-source electric heat pump, also combined with solar heating systems. Furthermore, we evaluated how a varied yearly heat demand influences the cost and primary energy efficiency of the different heat technologies. We found that both fuel costs and initial investment costs of heating systems play an important role for the cost efficiency of the different heat supply options. District heat is not always cost efficient for multi-apartment buildings especially for low energy buildings with minimum heat demand. There is also a tradeoff between heating cost and primary energy use in supplying heat to multi-apartment buildings.

Here we analyze the cost, primary energy and CO2 implications of supplying district heat, considering different supply and return temperatures, to a new residential area in Växjö, Sweden. We explore four land exploitation alternatives consisting different types of buildings with various heated floor areas as well as occupancy densities and two levels of building energy efficiency, based on the Swedish building code and passive house criteria. The analysis shows that energy performance of the buildings and land exploitation alternatives strongly influence the annual heat demand and its profile, which steers the design of the local heat distribution network. Additionally, supply and return temperatures of district heat somewhat influence the design of the network. The distribution heat losses could be reduced by 25% and 50% if district heating systems of 65/30 °C and 50/20 °C, respectively, are used instead of a conventional 80/40 °C system. However, for the same land exploitation alternative, the local distribution heat losses are about the same whether or not the buildings are designed to meet the Swedish building code or passive house criteria, since the same pipe distance is required and the variation of pipe diameters is small. A 50/20 °C system increases electricity use to boost hot water temperature to avoid the risk of legionella bacteria, and this influences quantity of district heat supply, primary energy use and costs. Therefore, a 65/30 °C system appears to be more primary energy and cost efficient than a 50/20 °C system. Increased insulation of district heating network reduces heat losses but this is not cost effective due to increased investment cost. The results are similar whether or not the analysis is based on current energy supply or future renewable based energy supply. This study increases understanding of strategies for planning and designing new urban residential areas and their energy supply systems to reduce primary energy use as well as monetary costs, and to minimize the climate impacts of the built environment.

Forest biomass that is currently unused, such as thinning and harvest residues, could be mobilized to produce bioelectricity, to mitigate climate change. An emerging technology for climate change mitigation is carbon capture and storage (CCS), which can reduce CO2 emissions from energy conversion facilities, but at a cost of additional fuel needed for process energy requirements. The use of forest residues that otherwise would decay on the forest floor, in an energy plant equipped with CCS, could result in a net reduction of CO2 emission to the atmosphere, while producing usable electricity. In this study, we analyse the climate change effects of using either coal or forest residues to produce electricity in large-scale conversion plants. We estimate the primary energy use, annual CO2 emission, annual change in CO2 concentration in the atmosphere and cumulative radiative forcing (CRF) of different energy systems that all produce the same quantity of electricity. We also consider the potential effects of future technology developments including gasification and integrated carbon capture processes. The results show that using forest residues to replace coal with current conversion technologies slightly increase the combustion CO2 emission, but in the long term give much lower net CO2 emission and mitigate climate change. The application of emerging gasification technology reduces primary energy use and CO2 emission compared to current technology, and hence increases the climate benefits. The use of CCS requires larger quantities of fuel, but could strongly reduce the CO2 emissions from conversion facilities, thus increasing the carbon benefits per unit of forest biomass used.